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123 Cards in this Set
- Front
- Back
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What is the role of memory cells in specific immunity? ***
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- memory cells are part of specific immunity (target a particular antigen, vice just a general response)
- they provide immunity to future attacks by “remembering” a particular pathogen - this decreases response time in future exposures by the same pathogen (Refresher: nonspecific immunity comprises: - first line of defense: epidermis, mucosa, hyalourinic acid, normal flora - second line of defense: phagocytic neutrophils and macrophages, antimicrobial proteins like interferons, complement system opsonization/cytolysis, NK cells, fever and inflammation) |
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What is the main difference between cell-mediated and humoral immunity? ***
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- cell-mediated immunity (T cells)
--- employs lymphocytes that directly attack and destroy foreign cells or diseased host cells --- antigen-bearing cells are attacked and destroyed by T cells --- means of ridding body of pathogens that reside inside human cells where they are inaccesible to antibodies --- allows destruction of pathogen-infected human cells as well as foreign cells - destroy intracellular viruses, bacteria, yeasts, and protozoans - also parasitic worms, cancer cells, cells of transplanted tissues and organs - humoral immunity (B cells) --- B cells produce antibodies (Ab) which attach to foreign pathogens --- "tagged for destruction" --- trigger action against those pathogens by rest of immune system --- "humoral" comes from the fact that many of the Ab are dissolved in the body fluids --- effective against extracellular viruses, bacteria, yeasts, protozoans and molecular (noncellular) pathogens such as toxins, venoms, and allergens --- also would destroy foreign RBCs in event of transfusion of mismatched blood type - T cells and B cells are part of adaptive immunity—the third and final line of defense |
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What is active immunity versus passive immunity? ***
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active immunity
- body produces antibodies or T cells against specific pathogen - two types of active immunity - natural and artificial - natural active immunity --- a person is naturally exposed to a pathogen (e.g., catch a cold and make Ab) --- triggers an active immune response to that specific pathogen - artificial active immunity --- triggering an active immune response by vaccination (deliberate exposure) --- injection of dead or attenuated forms of the pathogen passive immunity - antibodies are given to you, not produced by your body as a response to a pathogen - two types of passive immunity - natural and artificial - natural passive immunity --- short term immunity conferred by transfer of Ab from another person ----- placenta or mother’s milk ----- circulating Ab are eventually removed by liver - artificial passive immunity --- injection of antibodies produced by another individual or even species --- antisera against snakebite, rabies, tetanus, etc. |
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What is natural versus artificial immunity? ***
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- immunity acquired by natural means, i.e., contact with a disease-causing agent, when the contact was not deliberate
--- through exposure or --- through transfer from another person (mother) - immunity triggered by injection, i.e., acquired through deliberate actions such as vaccination or administration of antisera |
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What are haptens? ***
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- molecules that are too small to act as antigens on their own
- become antigenic and can stimulate immune response when bound to larger molecules or cells --- create a unique complex the body recognizes as foreign - e.g. poison-ivy oils, cosmetics, detergents, industrial chemicals, animal dander - after first exposure, hapten alone may stimulate immune response without needing to bind to a host molecule |
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What is the function of antigen presentation? ***
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- T cells on their own do not recognize free antigens; the antigens have to be “presented” to them
- T cells can only “see” an antigen that has been processed and presented by cells via carrier molecules like major histocompatibility complex (MHC) - antigen-presenting cells (APC) attack and destroy foreign cells, then digest them and attach epitopes* to the MHC locus on their membrane --- MHC locus = self-fingerprint on cell surface --- T cells inspect these loci and --- are activated when they recognize a foreign epitope on MHC (*refresher – epitope, a.k.a. antigenic determinant, are the specific regions of the antigen that immune system recognizes) |
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How do the MHC loci help with the process of antigen presentation? ***
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- antigen-presenting cells attack and destroy foreign cells via phagocytosis
- once digested, APCs attach epitopes* to the major histocompatibility complex (MHC) locus on their membrane surface - MHC locus = self-fingerprint on cell surface - T cells inspect these loci and are activated when they recognize a foreign epitope on MHC (* refresher – epitope, a.k.a. antigenic determinant, are the specific regions of the antigen that immune system recognizes) |
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What types of cells are APCs? ***
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- antigen-presenting cells
- signal T cells as to presence of antigen - T-cell receptor (TCR) recognizes and binds to the presented antigen - think of them as the detectives to the T cell bloodhounds - non-professional or - professional, which may be --- macrophages --- dendritic cells --- B cells all function as APCs, in addition to their other roles - once they phagocytize the antigen they move toward the lymph nodes |
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What are the main differences between T-cells and B-cells? ***
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T cells – cell-mediated immunity
- produced in red marrow, mature in thymus (thus “T” cell) - differentiate into 4 types: --- cytotoxic T cells (TC, or T8 cells) – attack and kill cells bearing their specific antigen --- helper T cells (TH or T4 cells) – stimulate activity by TC (divide) and B cells (divide and produce antibodies) --- regulatory T cells (TR cells) – limit activity of immune cells --- T memory cells (TM cells) – persist in lymph nodes like memory B cells - develop surface receptors for specific antigens—become immunocompetent - tested against self-antigens (cells that fail are destroyed—98%) - immunocompetent T cells divide and are distributed throughout body by blood and lymphatic systems - T cells destroy infected cells (esp. virus-infected) and cancer cells and coordinate the acquired immune response B cells – antibody-mediated, humoral (meaning fluid, i.e., plasma/blood/lymph) immunity - produced and mature in red bone marrow (thus “B” cell) - TH/T4 cells recognize antigen and stimulate production of antibodies by B cells - B cells divide and clone themselves, differentiating into memory cells and plasma cells - memory cells remember the antigen, they travel to and persist in the lymph nodes waiting for another contact with the same pathogen—and ensuring a more rapid response on subsequent exposure - once antigen is bound by antibody, one of four things may occur: --- antigen may no longer function properly (e.g., virus inactivation) --- antigen and/or attached microorganism may agglutinate (because most antibodies have more than one antigen binding site) or precipitate out of solution --- complement may be activated --- antibody-dependent cell-mediated cytotoxicity may occur if antigen is found on surface of one of body’s own cells |
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What are the four main classes of T-cells and what do they do? ***
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- cytotoxic T cells (TC, or T8 cells) – attack and kill cells bearing their specific antigen
- helper T cells (TH or T4 cells) – stimulate activity by TC (to divide) and B cells (to divide and produce antibodies) - regulatory T cells (TR cells) – limit activity of immune cells - T memory cells (TM cells) – persist in lymph nodes like memory B) |
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How are T-cells activated? ***
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- TC/T8 or TH/T4 cell binds to matching antigen presented by APC
- TC/T8 or TH/T4 cell divides and --- produces more TC/T8 cells to search for and attack antigen-bearing cells --- produces more TH/T4 cells to produce cytokines to activate other pathways; induce TC to divide and B cells to produce antibodies --- produces TM cells for storage in lymph nodes and future rapid reaction to same antigen |
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What is the role of T-helper cells in cell-mediated immunity? ***
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- attach to antigen-MHC complex
- secrete interleukins* (a type of cytokine—secreted protein/chemical signaling molecule) to activate other cells in order to: --- attract macrophages and NK cells --- activate macrophages (into “super macrophages”) --- stimulate T and B cell mitosis/maturation (especially B cells—plasma and memory) * interleukin – “inter” - between (as in communication between), “leuk”- WBCs |
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What is the role of T-helper cells in humoral immunity? ***
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- attach to antigen-MHC complex
- secrete interleukins* (a type of cytokine—secreted protein/chemical signaling molecule) to activate other cells in order to: --- attract macrophages and NK cells --- activate macrophages (into “super macrophages”) --- stimulate T and B cell mitosis/maturation (especially B cells—plasma and memory) *interleukin – “inter” - between (as in communication between), “leuk”- WBCs |
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How do T-cells destroy antigen-bearing cells? ***
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(find, bind, bomb, move on)
- search for cells bearing foreign antigen - attach to cell --- release perforins (cuts through the suface) and granzymes (like a grenade dropped through the hole created by the perforins) --- release interferons* - releases cells and moves to another antigen bearing cell *interferon – any of various proteins produced by virus-infected cells that inhibit reproduction of the invading virus and induce resistance to further infection |
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What are plasma cells? ***
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- the B cells responsible for humoral immunity
- indirect attack via antibodies --- each plasma cell produces a particular antibody to a specific antigen --- antibodies bind to antigen and flag the cell for destruction - production triggered by TH cell that binds to a B cell and releases interleukins,* creating: --- plasma cells (large numbers of antibodies/immunoglobulins) and --- memory cells (long-lived B cells primed for future attack and stored in lymph nodes) |
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What are immunoglobulins? ***
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- antibodies (the terms are often used interchangeably)
- large, Y-shaped protein produced by B cells and used to identify and neutralize antigens - each tip of the “Y” of an antibody contains a paratope (like a lock) that is specific for one particular epitope (like a key; a.k.a. antigenic determinant) - using this binding mechanism, an Ab can tag a microbe or infected cell for attack by other parts of the immune system, or can neutralize it directly - protein composed of four polypeptide chains - two domains (regions) --- variable (V) region – binding site for antigenic epitope --- constant (C) region – same for all your antibodies; recognized by other parts of immune system |
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What are the two main regions of antibody and what is the function of each region? ***
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- variable (V) region – binding site for antigenic epitope
- constant (C) region – same for all your antibodies; recognized by other parts of immune system |
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How do antibodies help fight against pathogens? ***
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- they are not killer cells; they attach to an antigen and either draw attention to it, or agglutinate it
once antigen is bound by antibody, one of four things may occur: 1) antigen may no longer function properly; masking/blocking the pathogenic region of the antigen-bearing molecule/cell (e.g., virus inactivation) 2) antigen and/or attached microorganism may agglutinate (because most antibodies have more than one antigen binding site—e.g., IgM pentamer) or precipitate out of solution - to stop the spread of the pathogen - to prevent reproduction in some cells - agglutinated complexes are easy for macrophages and eosinophils to destroy 3) complement may be activated 4) antibody-dependent cell-mediated cytotoxicity may occur if antigen is found on surface of one of body’s own cells |
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What is the difference between a primary and a secondary immune response? ***
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primary immune response
- initial exposure - no change evident up to 6 days while B cells multiply - antibody titer begins to rise - immune response noticeable - usually around 10 days after exposure secondary immune response - subsequent exposure - memory cells respond --- T cells activated --- plasma cells formed within hours - quick spike in Ab titer - pathogen may be removed before it affects body (no illness) or the effect may be attenuated |
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What is the difference between a hypersensitivity disorder, an autoimmune disorder, and an immunodeficiency disorder? ***
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hypersensitivity
- overactive immune responds to a normally non-pathogenic antigen - can involve cell-mediated or humoral systems - response of the immune system causes damage/symptoms e.g. - poison ivy (hapten) – T cell mediated skin damage - anaphylaxis – life-threating drop in BP and bronchial constriction (due basophil & mast cell degranulation) - asthma – bronchial constriction auto-immune diseases - failure of self-recognition - produce Ab against own tissues - destruction of those particular tissues e.g. - some type 1 diabetes (Ab attack beta cells) - Grave’s Disease (Ab binds to TSH receptors) immunodeficiency diseases - immune system incapable of responding to pathogens - person susceptible to attack by minor pathogens |
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What type of disorder is AIDS? ***
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immunodeficiency disease
- immune system incapable of responding to pathogens - person susceptible to attack by minor pathogens - (e.g., AIDS - HIV virus destroys TH cells and some macrophages) |
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What are the functions of the respiratory system? ***
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- communication
- olfaction - movement of gases into exchange area - protection of respiratory surfaces - surface for gas exchange – very large internal surface area respiration - ventilation - moving gases in and out of the lungs --- inspiration --- expiration - gas exchange - moving gases into and out of blood - cellular respiration - the use of oxygen for cellular respiration purpose - aerobic respiration - cells need O2, which must be delivered by blood - cells produce CO2, which must be eliminated from body --- carried by blood to lungs |
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What is in the upper respiratory system? ***
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everything above the larynx
- nose - nasal cavity - pharynx |
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What is in the lower respiratory system? ***
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everything from the larynx downward
- larynx - trachea - bronchi and bronchioles - alveoli (lungs) – functional part of the respiratory system |
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What are the structures within the nasal cavity and what are their functions? ***
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nose and nasal cavity function
- bring air into body - warm and filter air - olfaction nose and nasal cavity structures - external nares – nostrils - nasal vestibule – contains hairs to filter air - nasal septum – body division between left and right nasal cavity - nasal conchae – a.k.a. turbinate bones – curled projections from septum that slow/disrupt airflow and moisten incoming air - hard palate – floor of nasal cavity, roof of mouth - soft palate – closes of nasal cavity for swallowing - posterior nasal choanae – a.k.a. internal nares – rear opening nasal mucosa - secrete mucus --- traps particles in inhaled air --- helps humidify incoming air ----- extra moisture from nasolacrimal ducts ----- cool air is warmed and moistened during inhalation ----- expelled air is cooled and moisture recovered |
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How is the incoming air warmed and moistened? ***
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- nasal conchae – a.k.a. turbinate bones – curled projections from septum that slow/disrupt airflow and moisten incoming air
nasal mucosa - secrete mucus --- traps particles in inhaled air --- helps humidify incoming air ----- extra moisture from nasolacrimal ducts ----- cool air is warmed and moistened during inhalation ----- expelled air is cooled and moisture recovered |
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How is moisture and heat recovered from exhaled air? ***
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nasal mucosa
- secrete mucus --- traps particles in inhaled air --- helps humidify incoming air ----- extra moisture from nasolacrimal ducts ----- cool air is warmed and moistened during inhalation ----- expelled air is cooled and moisture recovered |
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What are the regions of the pharynx? ***
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- muscular tube connecting oral and nasal cavity to esophagus and larynx
regions - nasopharynx – uppermost part of the pharynx --- extends from base of the skull to upper surface of the soft palate --- differs from oral and laryngeal pharynx in that its cavity always remains patent (open) - oropharynx – extends from the uvula to the level of the hyoid bone - laryngopharynx – lowermost part of pharynx --- part of the throat that connects to the esophagus --- extends from the hyoid bone to the lower level of the cricoid cartilage |
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What are the cartilages and other structures of the larynx and what are each of their
functions? *** |
- glottis – muscular opening to larynx
cartilages – keep larynx open - thyroid cartilage – large shield of hyaline cartilage; forms laryngeal prominence - cricoid cartilage – below thyroid cartilage; supports rear of larynx - epiglottis – rod of elastic cartilage with connective tissue flaps that closes opening of larynx when swallowing (vestibular folds more important) - arytenoid cartilage – small internal cartilages that keep tension on vocal cords and close glottis - corniculate cartilages – on top of arytenoids; help control glottis and vocal cords other tissues - two folds close glottis --- vestibular folds (a.k.a. aka false vocal cords) – close glottis --- vocal folds – contain the vocal cords |
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How is sound produced and modified by the larynx and structures of the head? ***
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sounds produced by vibration of vocal cords
- pitch depends on tension of cords --- smaller, tighter cords = higher pitch --- larger, looser cords = lower pitch - tension on cords adjusted by pivoting arytenoid cartilage modification of sound - control of air flow - control of pharynx, tongue, lips, jaw - resonance in spaces of oral and nasal cavities and sinuses |
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What are the basic structures that make up the trachea and bronchi? ***
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trachea
- tough, flexible tube from larynx to bronchi - lined with pseudostratified epithelium --- underlying mucus glands --- ciliated --- upper part of respiratory escalator system (brings stuff up) - held open by C-shaped hyaline cartilage rings - primary (main) bronchi – branches of trachea leading to each lung - secondary (lobar) bronchi – branches of primary bronchi to each lung lobe - tertiary (segmental) bronchi – branches of secondary bronchi - bronchioles |
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How many lung lobes are there in humans? ***
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5 total (two left and three right)
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Know the general surface anatomy of the lungs. ***
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- highly vascularized, spongy organs
- two lobes on left (also cardiac notch) - three lobes on right - hilus - indentation where bronchi and vessels enter - mediastinal and costal surfaces (costal surface up against ribcage) |
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What tubes does air pass through on the way to the alveoli? How are each of these
tubes different from each other? *** |
- trachea – tough, flexible tube from larynx to primary bronchi
--- cartilaginous rings --- lined with pseudostratified epithelium --- underlying mucus glands --- ciliated - primary (main) bronchi, secondary (lobar) bronchi, and tertiary (segmental) bronchi – --- cartilaginous rings --- layer of smooth muscle fiber—bronchial muscle --- mucous membrane lined by columnar ciliated epithelium on basement membrane; ducts - bronchioles – branches of tertiary (segmental bronchi) --- no cartilaginous rings - walls are smooth muscle which can be dilated or constricted by ANS - ciliated epithelial cells are cubical in shape - lead into alveoli |
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What is the function of the cells found in alveoli? ***
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alveoli – sac-like ends of bronchioles, about 150 million per lung
three types of alveolar cells (pneumocytes) - type I pneumocyte (squamous alveolar cells) – responsible for gas exchange --- elastic fibers allow expansion --- form 95% of structure of alveolar wall - type II pneumocyte (great alveolar or septal cells) – secrete pulmonary surfactant by exocytosis --- keep alveoli from closing due to cohesive nature of water molecules (RDS) --- lower surface tension of water --- allow membrane to separate, increasing capability to exchange gases --- can differentiate into type I pneumocytes (which cannot replicate and are subject to vast numbers of toxic insults) - alveolar macrophages (dust cells) –destroy foreign material; protect lungs from microbes and aerosols ---most numerous cells in lung --- very short lived (removed by ciliary escalator) - surrounded by pulmonary capillaries |
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How does the negative space of the pleural cavity allow lung inflation? ***
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- creates a vacuum
- helps enlarge lungs when diaphragm and external intercostal muscles contract - increased volume = decreased pressure - air moves from higher pressure area (outside body) to lower pressure area (in lungs) |
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What is a pneumothorax and why does it cause respiratory problems? ***
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- abnormal collection of air or gas in the pleural space separating the lung from the chest wall
- it may interfere with normal breathing due to disruption of the normal vacuum created by the pleural cavity (normally, pressure in lungs is greater than pressure in pleural cavity surrounding lungs) - reduces compliance (ease of respiration)—lung difficult to inflate with increased external pressure - may lead to collapse of lung - if pneumothorax is present, compliance (ability and ease of respiration) is very low From his slide: Pleural cavities and membranes - cavities around lungs - lined with parietal pleura --- visceral pleura covers lungs --- secrete pleural fluid to lubricate lung surface - only a potential space --- normally a vacuum --- visceral and parietal pleura in contact - functions --- reduce friction via pleural fluid --- isolate lungs from each other, thus preventing spread of infection or a single pneumothorax from going bilateral |
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What is the relationship between pressure and volume of a gas? ***
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gas pressures and Boyle’s law
- gas concentrations measure in partial pressures (necessary because volume:mass ratio is not constant) - Boyle’s law - P = 1/V --- pressure is inversely proportional to volume --- decrease volume, pressure increases --- increase volume, pressure decreases - gases move from areas of high pressure to areas of low pressure - when diaphragm and external intercostals contract --- thoracic cavity and lungs expand and internal pressure drops --- air rushes into the lungs because pressure outside the body is greater than that in the lungs - when diaphragm and external intercostals relax --- thoracic cavity and lungs contract and internal pressure increases --- air rushes out of the lungs because the pressure inside the lungs is greater than the pressure outside the body |
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How is this relationship used to move air into and out of lungs? ***
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- Boyle’s law - P = 1/V
--- pressure is inversely proportional to volume --- decrease volume, pressure increases --- increase volume, pressure decreases - gases move from areas of high pressure to areas of low pressure - when diaphragm and external intercostals contract --- thoracic cavity and lungs expand and internal pressure drops --- air rushes into the lungs because pressure outside the body is greater than that in the lungs - when diaphragm and external intercostals relax --- thoracic cavity and lungs contract and internal pressure increases --- air rushes out of the lungs because the pressure inside the lungs is greater than the pressure outside the body |
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How do we inhale? What is the difference during forced inhalation? ***
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- we inhale by contracting the diaphragm and external intercostal muscles
--- increases size of thoracic cavity --- vacuum in pleural cavity enlarges lungs --- increased volume = decreased pressure - air moves from high pressure area (outside) to low pressure area (in lungs) - forced inhalation --- requires conscious thought --- utilizes more muscles (recruits internal intercostals, abdominals, scalenes, SCMs, trapezius, rhomboids, iliocostalis etc.) |
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How do we exhale? What is the difference during forced exhalation? ***
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- we exhale by relaxing the diaphragm (passive process)
--- pushes up into thoracic cavity --- decreases size of cavity --- decrease volume = increased pressure - air moves from high pressure area (in lungs) lower pressure outside body - forced exhalation --- requires conscious thought --- utilizes more muscles (recruits internal intercostals, obliques, rectus abdominis, etc.) |
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What is the tidal volume? ***
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- the amount of air inhaled and exhaled under resting conditions
- typically around 500 ml for both genders |
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What are the inspiratory and expiratory reserve volumes? ***
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IRV
- amount of air that can be inhaled above tidal volume/normal inspiration - normally around 3300 ml (males) and 1900 ml (females) ERV - amount of air that can be exhaled above tidal volume/normal expiration - normally around 1000 ml (males) and 700 ml (females) |
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What is the vital capacity? ***
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- “big breath in, big breath out”= IRV + TV + ERV
- maximum amount that can be taken in and out with forced effort - normally around 4600 ml (males) ad 3100 ml (females) |
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What is alveolar volume? ***
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- amount of air getting into alveoli
- may be influenced by damage to alveoli |
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What is dead air volume? Why is it considered “dead” air? ***
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- amount of tidal volume that stays in trachea, bronchi, and bronchioles
- also includes air in damaged alveoli - not involved in gas exchange - usually around 30% for relaxed breathing |
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What is compliance and what factors can affect it? ***
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- the ability and ease of respiration
factors affecting - lung structure – damaged lungs are less compliant - surfactant levels – takes more force to reopen alveoli in RDS - thoracic mobility – muscle or bone damage to ribcage - condition of parietal pleura – if pneumothorax is present, compliance is very low (atelectasis = collapse of lung) resistance to air flow affects ability of lungs to fill - compliance – factors affecting compliance influence ability to fill lungs - surfactant levels - low surfactant levels make lungs harder to fill - pressure must be increased to levels which can open alveoli - diameter of bronchioles --- bronchodilation – sympathetic stimulation, epinephrine --- bronchoconstriction – parasympathetic stimulation ----- histamine, cold air, chemical irritants ----- anaphylaxis or asthma - different regions of the lung can be regulated independently |
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What are the pressures involved in breathing? ***
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- pulmonary pressure – within lungs
- atmospheric pressure – outside the body - pleural pressure – in pleural cavity - alveolar pressure – pressure within the alveoli (under normal conditions, the driving force behind airflow into and out of the lungs) |
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How is eupnea different from hyperpnea? ***
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- eupnea is relaxed, quiet breathing (approximate tidal volume of 500 ml and rate of 12-15 rpm)
- hyperpnea is increased rate and depth of breathing in response to exercise, pain, or other condition |
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How do oxygen and CO2 get from the alveolus to the blood? ***
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- gas exchange is caused by partial pressures and diffusion
- rate of diffusion is determined by partial pressures (concentration) of the gases gas exchange in the alveoli - PO2 is high in alveolar air, low in blood O2 diffuses into blood - PCO2 is low in alveolar air, high in blood CO2 diffuses out of blood |
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How do oxygen and CO2 get from the blood to the peripheral tissues? ***
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- gas exchange is caused by partial pressures and diffusion
- rate of diffusion is determined by partial pressures (concentration) of the gases gas exchange in peripheral tissues - PO2 is higher in blood than tissues --> O2 diffuses into tissues from blood - PCO2 is higher in peripheral tissues --> CO2 diffuses out of tissues into blood |
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How is oxygen carried in the blood? ***
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oxygen transported by hemoglobin
- each hemoglobin carries up to 4 oxygen - oxygen held to heme group by low affinity bond |
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What variables affect the ability of hemoglobin to carry oxygen? ***
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hemoglobin saturation – percentage of heme units carrying O2 (0%, 25%, 50%, 75%, 100%)
- saturation varies with PO2 --- high PO2 = high saturation --- as PO2 goes down, saturation goes down - hemoglobin gives up oxygen more freely under conditions of low PO2 - saturation is very high when PO2 is moderately high - saturation reached quickly presence of carbon monoxide - higher heme affinity than O2 - bonds quicker, harder to remove pH and hemoglobin saturation (Bohr effect) - hemoglobin saturation/affinity is proportional to pH - as pH goes down, saturation goes down - hemoglobin releases more O2 at low pH - low pH caused by dissolved CO2 (carbonic anhydrase) temperature and O2 saturation - saturation decreases with increased temperature - active areas of the body are warmer --- lower saturation = more release of oxygen fetal hemoglobin – higher affinity for O2 |
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How is CO2 carried in the blood? ***
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most CO2 transported as carbonic acid (H2CO3)
- converted by carbonic anhydrase in RBCs - H+ binds to hemoglobin - HCO3 transported out to plasma - exchanged for Cl- (the chloride shift) some CO2 transported as carboxyhemoglobin |
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How does the fetus get oxygen from the mother’s blood (i.e. why does the mother’s blood give it up)? ***
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- fetal hemoglobin has a higher affinity for O2
- baby can pull it out of the mother’s circulation |
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What parts of the brainstem are involved in respiration and what do they do? ***
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automatic, unconscious cycle
- three pairs of respiratory centers - reticular formation, medulla oblongata, pons respiratory nuclei in medulla - ventral respiratory group (VRG) --- primary control of respiratory rhythm --- during eupnea ----- inspiratory neurons fire for about 2 seconds ----- expiratory neurons fire for about 3 seconds; inspiratory muscles relax ----- respiratory rhythm ~12 breaths per minute - dorsal respiratory group (DRG) --- changes rate and depth of breathing --- influenced from external sources pontine respiratory group (PRG) – a.k.a. pneumotaxic center (pons) - modifies rhythm to VRG and DRG - adapts breathing to special circumstances (e.g., sleep, exercise, speaking, emotion) - may trigger utilization of extra muscles reflexes influencing PRG and DRG - central chemoreceptors --- brainstem neurons respond to pH of CSF --- pH reflects the CO2 level in the blood - peripheral chemoreceptors in carotid and aortic bodies measure O2, CO2, and the pH of blood - inflation reflex - stretch receptors in lungs inhibit inhalation - deflation reflex - triggers inhalation after lung deflation Regulation - medullary and pontine regulatory groups --- receive feedback from baroceptor and chemocepter reflexes --- measure pH, PO2 and PCO2 - inflation reflexes (Hering-Breuer inflation reflex) respond to excessive stretching of the lung during large inspirations; via vagus nerve to --- inspiratory area of medulla(inhibit it directly) and --- apneustic area of pons (inhibited from activating the inspiratory area) - deflation reflexes (Hering-Breuer deflation reflex) respond to stimulation of stretch receptors or stimulation of proprioceptors activated by lung deflation; via vagus nerve to: --- inspiratory centers, rather than pontine apneustic center --- shorten exhalation when lung is deflated --- plays more minor role in humans than other mammals |
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What is the role of the DRG, VRG, and PRG? ***
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respiratory nuclei in medulla
- ventral respiratory group (VRG) --- primary control of respiratory rhythm --- during eupnea ----- inspiratory neurons fire for about 2 seconds ----- expiratory neurons fire for about 3 seconds; inspiratory muscles relax ----- respiratory rhythm ~12 breaths per minute - dorsal respiratory group (DRG) --- changes rate and depth of breathing --- influenced from external sources pontine respiratory group (PRG) – a.k.a. pneumotaxic center (pons) - modifies rhythm to VRG and DRG - adapts breathing to special circumstances (e.g., sleep, exercise, speaking, emotion) - may trigger utilization of extra muscles |
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How does the PCO2 affect bronchioles and blood flow? ***
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ventilation-perfusion coupling - rate of blood flow into lungs and air flow is coupled
- increased airflow into lungs ---leads to high PO2 in alveolar vessels --- this causes vasodilation and more blood flow into region of lung - increased bloodflow into lungs leads to high PCO2 --- results in local bronchiole dilation --- brings more air into that area of lung peripheral tissues - high PCO2 results in dilation of peripheral capillaries - more blood flow to area |
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What are the reflexes that help regulate respiration? ***
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- medullary and pontine regulatory groups
--- receive feedback from baroceptor and chemocepter reflexes --- measure pH, PO2 and PCO2 - inflation reflexes (Hering-Breuer inflation reflex) respond to excessive stretching of the lung during large inspirations; via vagus nerve to --- inspiratory area of medulla(inhibit it directly) and --- apneustic area of pons (inhibited from activating the inspiratory area) - deflation reflexes (Hering-Breuer deflation reflex) respond to stimulation of stretch receptors or stimulation of proprioceptors activated by lung deflation; via vagus nerve to: --- inspiratory centers, rather than pontine apneustic center --- shorten exhalation when lung is deflated --- plays more minor role in humans than other mammals |
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What are the inputs that affect the medulla’s regulation of respiration? ***
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- medullary and pontine regulatory groups
--- receive feedback from baroceptor and chemocepter reflexes --- measure pH, PO2 and PCO2 - inflation reflexes (Hering-Breuer inflation reflex) respond to excessive stretching of the lung during large inspirations; via vagus nerve to --- inspiratory area of medulla(inhibit it directly) and --- apneustic area of pons (inhibited from activating the inspiratory area) - deflation reflexes (Hering-Breuer deflation reflex) respond to stimulation of stretch receptors or stimulation of proprioceptors activated by lung deflation; via vagus nerve to: --- inspiratory centers, rather than pontine apneustic center --- shorten exhalation when lung is deflated --- plays more minor role in humans than other mammals |
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What is ventilation-perfusion coupling? ***
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ventilation-perfusion coupling - rate of blood flow into lungs and air flow is coupled
- increased airflow into lungs ---leads to high PO2 in alveolar vessels --- this causes vasodilation and more blood flow into region of lung - increased bloodflow into lungs leads to high PCO2 --- results in local bronchiole dilation --- brings more air into that area of lung peripheral tissues - high PCO2 results in dilation of peripheral capillaries - more blood flow to area |
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How do airflow and bloodflow into the lung influence each other? ***
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ventilation-perfusion coupling - rate of blood flow into lungs and air flow is coupled
- increased airflow into lungs ---leads to high PO2 in alveolar vessels --- this causes vasodilation and more blood flow into region of lung - increased bloodflow into lungs leads to high PCO2 --- results in local bronchiole dilation --- brings more air into that area of lung peripheral tissues - high PCO2 results in dilation of peripheral capillaries - more blood flow to area |
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What are the organs/structures of the urinary system? ***
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- kidney (2)
- ureter (2) - bladder (1) - urethra (1) - shared with reproductive system in males |
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What are the functions of the urinary system? ***
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- regulation of blood pressure/volume
- regulation of blood pH (ridding body of extra H+ ions) - regulation of plasma concentrations (ions like Na+ and Ca++) - regulation of nutrient levels (e.g., too much glucose) - excretion (a.k.a. micturition) – this is the primary role of the kidney - detoxification – removal of nitrogenous wastes nitrogenous wastes - urea --- formed from deamination of proteins (amine terminals build up) --- amine groups converted to ammonia, then urea - uric acid – formed from nucleic acid catabolism - creatinine – byproduct of creatine phosphate metabolism - BUN (blood urea nitrogen) – clinical measure used to evaluate liver/kidney function |
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What is the general anatomy of the kidney? ***
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gross anatomy
- retroperitoneal – approx. at level of 12th rib - connective tissue covering --- renal capsule – collagen fiber covering over kidney --- adipose capsule --- renal fascia – fibrous connective tissue attaches kidney to surrounding muscles/organs organ structure - renal sinus – medial cavity occupied by blood and lymph vessels, nerves, & urine-collecting structures - renal cortex – 1 cm thick outer capsule - renal medulla – inner portion facing the sinus - renal columns – extensions of the cortex that project toward the sinus, divide kidney into pyramids - renal pyramids – conical divisions of renal medulla; one pyramid and overlying cortex = one lobe of kidney --- renal papillae – blunt point of renal pyramid that faces the sinus - calyces --- minor – papilla of each renal pyramid is nestled in cup-like minor calyx, which collects urine --- major – 2-3 minor calyces converge to form a major calyx - renal pelvis – 2-3 major calyces converge in renal sinus to form funnel-like renal pelvis blood supply from/to heart – he said know this pathway for the test!! - aorta (aortic arch, thoracic aorta, abdominal aorta) - renal artery - interlobar artery - arcuate artery - interlobular artery - afferent arteriole - glomerulus - efferent arteriole - peritubular capillaries - venules - interlobular veins - arcuate veins - interlobar veins - renal vein - inferior vena cava |
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What is a nephron? What is its general anatomical structure? ***
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- the functional unit of the kidney (this received a “foot stomp”) ***
structure - renal corpuscle --- cup shaped chamber (Bowman's capsule) containing glomerulus --- lined with simple squamous epithelium - renal tubule (PCT, nephron loop, DCT, collecting duct) --- tube attached to corpuscle --- takes filtrate away from corpuscle for processing |
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What are the layers of the Bowman’s capsule? ***
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- the renal corpuscle = the glomerulus and glomerular (Bowman’s) capsule surrounding it
- glomerulus --- cluster of fenestrated capillaries --- blood comes in through afferent arteriole - Bowman's capsule --- visceral epithelium comprised of podocytes ----- star-shaped cells wrapped around glomerular capillaries ----- foot like extensions called pedicels ----- filtration slits between pedicels --- parietal epithelium surrounding capsular space |
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What are podocytes, pedicels and filtration slits? What do they do? ***
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part of Bowman's capsule
- visceral epithelium comprised of podocytes --- star-shaped cells wrapped around glomerular capillaries --- foot like extensions called pedicels --- filtration slits between pedicels - podocytes wrap around glomerular capillaries and pedicels of the podocytes interdigitate - pedicels have 30nm wide filtration slits between them - molecules smaller than 3nm pass freely (water, electrolytes, glucose, fatty acids, amino acids, nitrogenous wastes, vitamins) |
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How is filtration accomplished within the renal corpuscle? ***
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filtration – movement of water across a semipermeable membrane under hydrostatic pressure
blood enters glomerulus - hydrostatic pressure forces fluids and small solutes out into capsular space --- filtered through fenestrations and filtration slits between pedicels --- creates plasma-like glomerular filtrate glomerular filtrate enters renal tubule - proximal convoluted tubule (PCT)—get back stuff not meant to be thrown out --- reabsorption of nutrients, water --- reabsorbed materials taken up by peritubular capillaries nephron loop (Loop of Henle) - descending tubule - ascending tubule - both tubules have thick and thin areas --- thin segments are water-permeable region (retrieve water) --- thick segments are not very water permeable, but have lots of ion pumps; recover Na+ from filtrate - distal convoluted tubule – area where active secretion absorption takes place (fine tuning) --- water, Na+, Ca+, reabsorbed --- H+, toxins, nitrogenous wastes secreted - removal of wastes (e.g., urea, extra H+, etc.) - urine drains into collecting ducts, which drain into calyces of kidney |
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What is the GFR? ***
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- glomerular filtration rate
glomerular filtration – fluid leaves glomerular capillaries due to hydrostatic pressure of blood - Glomerular Filtration Rate --- amount of filtrate produced in one minute (~ 125ml or 1/2 cup) ----- ~ 180 liters day (almost 50 gallons, of which 99% is recovered) --- resisted by blood colloid osmotic pressure ---- osmotic pressure of proteins in glomerular blood |
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What variables affect the GFR? ***
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- changes in glomerular hydrostatic pressure (GHP)
--- diameter of afferent arterioles ----- vasodilation – increased hydrostatic pressure and increased GFR ----- vasoconstriction – decreased hydrostatic pressure and decreased GFR --- diameter of efferent arterioles ----- vasoconstriction (moderate) – increase glomerular capillary hydrostatic pressure and slightly increase GFR ----- vasoconstriction (severe) – decrease RBF and decrease GFR - ABP – between 70-170 mm HG, GFR and RBF kept relatively constant by autoregulatory mechanisms - RBF – direct relation with GFR - sympathetic stimulation – if sever, afferent arterioles constricted leading to decreased GFR - changes in Bowman’s capsule hydrostatic pressure (e.g., due stone in ureter) – decreased GFR - change in glomerular colloidal osmotic pressure --- increased COP (e.g., in dehydration) – decreased GFR --- decreased COP (e.g., in hypoproteinemia) – increased GFR autoregulation - constriction/dilation of afferent/efferent arterioles maintain GHP - smooth muscles surrounding afferent arteriole constrict, reduced flow and GFR decrease - smooth muscles surrounding efferent arteriole constrict, build up of hydrostatic pressure and GFR increase --- myogenic autoregulation ----- smooth muscles of arterioles contract when stretched ----- maintains constant pressure to glomerulus --- tubuloglomerular autoregulation – each nephron controls itself ----- cells of macula densa - junction of nephron loop and DCT ----- measure Na concentration in tubular fluid ------- if too high, releases signal to constricts afferent arteriole ------- if too low, allows dilation of arteriole hormonal regulation – global effect, not nephron by nephron - drop in pressure detected by JGA; renin-angiotensin system triggered --- constriction of efferent arteriole – increases back pressure --- aldosterone release – to recover fluid --- release of ADH and stimulation of thirst --- constriction of peripheral arterioles – force more blood to kidney - balanced by natriuetic peptides autonomic - sympathetic fibers - decreases GFR due to constriction of afferent arterioles problems - too high = not enough reabsorption, hyperurea, dehydration, electrolyte depletion - too low = wastes can be reabsorbed azotemia = elevated nitrogenous wastes in blood |
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What is the function of the juxtaglomerular apparatus? ***
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- mass of cells near mouth of capsule, between the afferent and efferent arterioles
- due to their positioning, they can easily compare the pressure between the two - monitor BP and secrete renin in response to drop in blood pressure - also secrete erythropoeitin |
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How do renin and erythropoietin affect GFR? ***
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increase blood pressure, increase GFR
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What is the normal GFR (per minute)? ***
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- Glomerular Filtration Rate
--- amount of filtrate produced in one minute (~ 125ml or 1/2 cup) |
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What is the blood colloid osmotic pressure? What causes it? ***
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- pressure opposing the hydrostatic pressure
- concentration of plasma proteins - in the kidneys, contributes to fluid movement between the glomerulus and the Bowman's capsule, affecting GFR - BHP is so high in glomerular capillaries that they exclusively filter, no osmotic reabsorption |
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How does the diameter of the afferent and efferent arterioles affect the GFR? ***
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- changes in glomerular hydrostatic pressure (GHP)
--- diameter of afferent arterioles ----- vasodilation – increased hydrostatic pressure and increased GFR ----- vasoconstriction – decreased hydrostatic pressure and decreased GFR --- diameter of efferent arterioles ----- vasoconstriction (moderate) – increase glomerular capillary hydrostatic pressure and slightly increase GFR ----- vasoconstriction (severe) – decrease RBF and decrease GFR - ABP – between 70-170 mm HG, GFR and RBF kept relatively constant by autoregulatory mechanisms - RBF – direct relation with GFR - sympathetic stimulation – if sever, afferent arterioles constricted leading to decreased GFR autoregulation - constriction/dilation of afferent/efferent arterioles maintain GHP - smooth muscles surrounding afferent arteriole constrict, reduced flow and GFR decrease - smooth muscles surrounding efferent arteriole constrict, build up of hydrostatic pressure and GFR increase --- myogenic autoregulation ----- smooth muscles of arterioles contract when stretched ----- maintains constant pressure to glomerulus |
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What is removed from the GF in what regions of the renal tubule? ***
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glomerular filtration
- filtrate --- small molecules pass ----- water, electrolytes, glucose, fatty acids, amino acids, nitrogenous wastes, vitamins ----- most everything, except the nitrogenous wastes, will be recovered --- small protein-bound molecules do not pass ----- bound elements (iron, calcium) ----- thyroid hormones proximal convoluted tubule – reabsorption of 65% of filtrate - nutrients --- facilitated diffusion and transport of amino acids and glucose --- transport maxima exist (pumps can only work so hard) - ions via ion pumps - water – drawn out by osmotic gradient created by ion pumps - some secretion of some ions (K+, H+, PO4-), wastes, drugs nephron loop - thin descending limb is water permeable - thick ascending limb contains Na+ and Cl- pumps - countercurrent multiplication --- Na+/Cl- pumped into peritubular fluid by ascending limb --- osmotic gradient causes water to diffuse out of descending limb ----- this leads to increased ion concentration in ascending limb ----- faster rate of Na+/Cl- transport distal convoluted tubule – fine tuning - ion reabsorption --- Na+/K+ pumps – regulated by aldosterone --- Ca++ reabsorption – regulated by PTH and calcitrol - secretion --- K+ -- exchanged for Na+ --- H+ -- proton pumps; may bind to NH3 to produce NH4+ collecting ducts - reabsorption --- Na+ -- aldosterone --- H2O -- water channels controlled by ADH --- HCO3 -- exchanged for Cl- --- urea – diffuses out of duct, creating high osmotic pressure around bottom of loop of Henle |
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What is removed from the GF in the proximal tubule? ***
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proximal convoluted tubule – reabsorption of 65% of filtrate
- nutrients --- facilitated diffusion and transport of amino acids and glucose --- transport maxima exist (pumps can only work so hard) - ions via ion pumps - water – drawn out by osmotic gradient created by ion pumps - some secretion of some ions (K+, H+, PO4-), wastes, drugs |
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How does the countercurrent multiplication system work? ***
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positive feedback loop
- more salt continually added by PCT - higher the osmolarity of the ECF, the more water leaves the descending limb by osmosis - the more water that leaves the descending limb, the saltier the fluid is that remains in tubule - the saltier the fluid in the ascending limb, the more salt the tubule pumps into ECF - the more salt pumped out of the ascending limb, the saltier the ECF in renal medulla - repeat (from step 2) |
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What hormones control excretion/recovery of ions in the renal tubule and how do they
affect the tubule channels? *** |
distal convoluted tubule – fine tuning
- ion reabsorption --- Na+/K+ pumps – regulated by aldosterone --- Ca++ reabsorption – regulated by PTH and calcitrol - secretion --- K+ -- exchanged for Na+ --- H+ -- proton pumps; may bind to NH3 to produce NH4+ |
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How is urine transported from the kidneys and where is it stored? ***
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transported by ureters
- lead urine from renal pelvis to bladder - transitional epithelium lined, smooth muscle tube stored in bladder - muscular sac (detrusor muscle) - urethral opening – closed by internal muscular sphincter - urethra – muscular tube lined with epithelium |
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How does the body release urine (what are the steps of the micturition reflex)? ***
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micturition reflex
- bladder fills with urine - stretch receptors --- signal sacral areas of spinal cord to stimulate reflexive contraction of detrusor --- signals to cerebral cortex the sensation of full bladder - sphincters --- internal urethral sphincter is under autonomic control --- external urethral sphincter is under conscious control - contraction of detrusor muscles |
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What is the alimentary canal? ***
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- alimentary canal = digestive tract or GI tract
- continuous, muscular tube from mouth to anus |
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What is the histological structure of the alimentary canal? ***
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mucosa
- mucous membrane (mucus secreting glands or cells may be in deeper layers) - epithelium --- type depends on organ --- may contain enteroendocrine cells - lamina propria --- areolar tissue --- blood vessels and nerves --- lymphatic vessels and some lymphatic nodules (MALT) --- may be highly folded - submucosa - dense irregular connective tissue - contains major blood vessels and nerves - muscularis externa – two layers of smooth muscle --- inner circular layer --- outer longitudinal layer - serosa – areolar tissue and mesothelium --- layer of serous membrane --- found where structures are not attached to other tissues |
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What is peristalsis? How is it accomplished? ***
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coordinated movement of circular and longitudinal muscles
- forces material through muscular tubes - contraction of circular muscle followed by contraction of longitudinal muscle - predominates in the esophagus |
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What is segmentation? ***
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- breaking up food in digestive tract via contractions of the circular muscles
- moves chyme in both directions, allowing greater mixing with intestinal secretions - occurs in small intestine (where it predominates) and - in the large intestine |
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What are the functions and structures of the oral cavity? ***
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FUNCTIONS
1. sensory processing – taste and smell 2. mechanical processing – chewing 3. lubrication – dissolving food in saliva 4. digestion – lipids and polysaccharides GENERAL STRUCTURES 1. vestibule – space between teeth and cheeks/lips 2. gingivae – gums 3. hard palate – extensions of maxillary and palatine bones 4. soft palate – muscular flap separating nasopharynx from oral cavity 5. lips – help seal anterior end of mouth TONGUE FUNCTION - mechanical processing of food - manipulation and movement of food within oral cavity - sensory analysis of food (taste, temperature, consistency) - digestion --- lingual lipase - begins digestion of triglycerides --- very high acid tolerance - communication TOOTH FUNCTION - mastication --- break up food --- grind up large pieces --- expose more surface of food for digestive enzymes TOOTH STRUCTURE heterodonty – mammals have different teeth for different tasks - incisors – blade shaped shearing teeth - canines (cuspids) – elongate teeth for tearing meat - premolars (bicuspids) – intermediate grinding teeth - molars – large flat grinding teeth dental formula - number of teeth of each type - humans = 2 1 2 3 (on each side) = 32 structure - root – part under gumline; held in alveolar socket by peridontal ligament - crown – exposed part of tooth covered with enamel - dentin – acellular bone-like matrix - pulp cavity – inner chamber of living cells; contains blood vessels and nerves --- connects to major vessels through root canal - occlusal surface – chewing surface of tooth dental succession – humans have two sets of teeth - deciduous teeth – 2, 1, 1, 1 = 20 --- due to small jaws of children --- fall out due to breakdown of peridontal ligament - permanent teeth – begin to replace deciduous teeth in childhood as jaw enlarges --- finishes late in adolescence |
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What are the secretions of the salivary glands? ***
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salivary glands
1. saliva a. mostly water b. mucins – thick glycoproteins for lubrication of food and oral cavity c. antibacterial properties --- rinses bacteria from oral surfaces --- lysozyme – antibacterial enzyme --- antibodies (IgA) 2. parotid glands a. on lateral side of jaw near TMJ b. produce watery saliva with salivary amylase --- digests starch into disaccharides --- drained into mouth by parotid duct 3. sublingual glands a. under tongue on floor of mouth b. produce thicker, mucosal saliva that lubricates food and mouth 4. submandibular glands a. underneath body of mandible b. secrete buffers, mucus and amylase |
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What are the characteristics of the esophagus? ***
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characteristics
1. muscular tube from pharynx to stomach – posterior to trachea 2. no digestive function 3. closed at top and bottom by esophageal and cardiac sphincters 4. mucosa --- stratified squamous epithelium --- many submucosal mucus glands |
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What is involved in the process of swallowing? ***
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1. bolus formed by teeth, tongue and saliva
2. bolus moved to oropharynx – conscious movement 3. presence of bolus triggers swallowing reflex (autonomic from here) - tactile receptors in uvula and soft palate signal medulla --- a. relaxation of pharyngeal muscles --- b. elevation of soft palate – closure of nasopharynx --- c. elevation of larynx – closure of epiglottis against rear of tongue --- e. peristalsis of esophagus --- f. opening of cardiac sphincter |
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What are the functions of the stomach? ***
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- storage of food
- mechanical breakdown of food - denaturation of chemical bonds - production of intrinsic factor - digestion – NOT absorption |
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What are the different regions of the stomach? ***
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- cardiac region – around cardiac sphincter
- fundic region – upper space in stomach; may be used for storage - body – main mixing and digestion region - pyloric region – regulates release of chyme; controlled by pyloric sphincter histology - highly folded mucosa – rugae --- simple columnar epithelium --- prominent gastric pits - extra muscular layers – very muscular organ for churning |
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What are the different gastric gland cells and what do they secrete? ***
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gastric glands – at the base of the gastric pits
parietal cells secrete - intrinsic factor for vitamin B12 absorption - H+ and Cl- --- H+ from CO2 by carbonic anhydrase; transported into stomach lumen --- Cl- brought in from blood in exchange for HCO3-; diffuses into stomach lumen - ghrelin – triggers hunger, release of GHRH, may help form memories chief cells secrete - pepsinogen – low pH converts this to pepsin; powerful proteolytic enzyme - gastric lipase - renin (in newborns) G (gastroendocrine) cells secrete - gastrin in pyloric region to produce gastric juice in response to peptides and amino acids in stomach |
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What is the function of these gastric secretions? ***
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parietal cells secrete
- intrinsic factor for vitamin B12 absorption - ghrelin – triggers hunger, release of GHRH, may help form memories - H+ and Cl- --- H+ from CO2 by carbonic anhydrase; transported into stomach lumen --- Cl- brought in from blood in exchange for HCO3-; diffuses into stomach lumen HCl (stomach acid) functions: - antimicrobial - denaturation of proteins - some breakdown of plant cell walls - breakdown of fibrous connective tissues - activation of pepsin and lingual lipase chief cells secrete - pepsinogen – low pH converts this to pepsin; powerful proteolytic enzyme - gastric lipase - renin (in newborns) G (gastroendocrine) cells secrete - gastrin in pyloric region to produce gastric juice in response to peptides and amino acids in stomach |
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What is the function of gastrin? Where does it come from? ***
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G (gastroendocrine) cells secrete
- gastrin in pyloric region to produce gastric juice in response to peptides and amino acids in stomach |
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What is chyme? ***
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- semifluid mass of partly digested food expelled by the stomach into the duodenum
- results from the mechanical and chemical breakdown of a bolus and consists of partially digested food, water, hydrochloric acid, and various digestive enzymes |
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What are the entero(gastric), gastroenteric, and gastroiliac reflexes? ***
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- enteric reflexes – local reflexive peristalsis
- gastroenteric reflex – stretch of stomach stimulates contraction and secretion in intestine - gastroiliac reflex – stretched stomach opens ileocecal valve |
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What is the origin and function of cholecystokinin? ***
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- peptide hormone of the enteroendocrine cells
- synthesized by cells in the mucosal epithelium of small intestine and secreted in the duodenum - causes release of digestive enzymes and bile from pancreas and gallbladder, respectively - stimulates digestion of fat and protein - also acts as hunger suppressant |
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What is the origin and function of secretin? ***
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- hormone that originates in the S cells of the duodenum, in the crypts of Lieberkuhn
- regulates pH of the duodenal contents - released in response to gastric acid in the duodenum - stimulates the pancreas and bile ducts to release bicarbonate base to neutralize the acid |
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Where does most of the nutrient absorption take place? ***
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- small intestine
- digestion, and 90% of nutrient absorption |
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What is the function of the ileocecal valve? ***
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- controls flow of material into colon
- function is to limit the reflux of colonic contents into the ileum |
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How is the ileocecal valve regulated? ***
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- gastroiliac reflex – stretched stomach opens ileocecal valve
- regulated via pressure in cecum from material that has already passed through the valve - also presence of hormones released during digestion (e.g., gastrin released due to presence of food) |
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What are brush border enzymes? ***
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- enterocytes (absorptive cells) of the small intestine have a fuzzy brush border of microvilli that increase the absorptive surface area of the small intestine and contain brush border enzymes in the plasma membrane
- these enzymes carry out some of the final stages of chemical digestion of carbohydrates and proteins - not secreted into the lumen; the chyme must contract the brush border for digestion to occur - contact digestion is one reason it is so important intestinal contractions churn the chyme and it all contacts the mucosa |
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What is a lacteal? ***
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- the core of a villus is filled with areolar tissue of the lamina propria
- embedded in this tissue are an arteriole, a capillary network, a venule, and a lymphatic capillary called a lacteal - the blood capillaries absorb most nutrients, but the lacteal absorbs most lipids - they give its contents a milky appearance, for which the lacteal is named |
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What process is responsible for movement of materials through the intestine? ***
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small intestine – autorhythmic contraction
- smooth muscle contracts periodically - segmentation mixes materials - waves of peristalsis moves materials along large intestine - ascending colon – slow peristaltic waves and haustral segmentation - transverse throughsigmoid colon --- mass movements --- periodic large scale peristalsis of the colon --- triggered by stretch receptors in stomach and intestines (gastrocolic, duodenocolic reflex) |
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Why is the pancreas both and endocrine and exocrine gland? ***
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- it has functions in both systems; releases hormones into bloodstream and enzymes into intestines
- endocrine functions through the pancreatic islets and secretion of glucagon and insulin - exocrine functions (99%) through secretion of pancreatic juice by Acinar cells |
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What are pancreatic enzymes and what is their function? ***
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pancreatic enzymes – triggered by CCK and parasympathetic innervation
- pancreatic amylase – starch to disaccharides (digests starch) - pancreatic lipase – triglycerides to monoglycerides and glycerol (digests fat) - nucleases – nucleic acids to nucleotides (digests RNA and DNA) |
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How does blood enter and leave the liver? ***
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liver receives
- 70% of its blood from hepatic portal vein --- which receives blood from stomach, intestines, pancreas, and spleen --- all nutrients absorbed by small intestine reach liver by this route, except for lipids (transported in lymphatic system) and - 30% from the hepatic artery - delivery of oxygen and other materials from heart - then flows through sinusoids to central vein |
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Where is bile synthesized? ***
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in the liver, NOT the gallbladder
- hepatocytes produce bile from cholesterol and proteins - collected by bile ducts in lobules - drain to common hepatic duct and into common bile duct - backs up into gall bladder for concentration and storage |
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Where is bile stored? ***
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- after production in the liver, bile drains to common hepatic duct and into common bile duct
- when bile duct is filled it backs up into gall bladder for concentration and storage |
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What is the function of bile? ***
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- aids in the digestion of lipids in small intestine
- stored in gallbladder and, upon eating, is discharged into duodenum - acts as surfactant, helping to emulsify fats in food - bile salt anions have a hydrophilic and a hydrophobic side - aggregate around droplets of fat (triglycerides and phospholipids) to form micelles --- hydrophobic side toward fat, hydrophilic toward outside --- prevents bile-coated fat droplets from reaggregating --- increased surface area for action of pancreatic lipase to digest triglycerides (through gaps between bile salts - triglycerides are broken down into two fatty acids and a monoglyceride - these are absorbed by villi in intestinal walls - after passing through intestinal membrane, fatty acids are re-formed into triglycerides - then absorbed into lymphatic system through lacteals |
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What is the liver’s role in carbohydrate metabolism? ***
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- glycogenolysis when glucose levels are low
- gluconeogenesis when glucose levels are low - glycogenesis when glucose levels are high - convert glucose to lipids when glucose levels are high |
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What is the liver’s role in lipid metabolism? ***
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- lipids come in from hepatic artery
- chylomicrons converted to VLDL - sent to circulation to provide lipids to cells - lipids produced or broken down as energy needs dictate |
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What is the liver’s role in amino acid metabolism? ***
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- removes excess AA from circulation
- used to form proteins or for energy (also removal of wastes through deamination of amino acids and conversion to urea) |
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What is the liver’s role in the regulation of blood? ***
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- Kuppfer cells
--- remove damaged cells and debris ---present antigens for immune system - synthesis of plasma proteins - antibody removal - hormone removal - detoxification |
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What are the regions of the colon? ***
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- cecum – containing appendix and lymph nodules
- colon – contains haustra - rectum - anus |
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What is the function of the colon? ***
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- water absorption
- resorption of bile - production of vitamins via coliform bacteria (e.g., Vitamin K, Vitamin B) |
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What is mass movement? ***
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in the transverse through sigmoid colon:
- periodic large scale peristalsis of the colon - triggered by stretch receptors in stomach and intestines (gastrocolic, duodenocolic reflex) |
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What is excreted in the feces? ***
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~ 75% water by mass
~ 5-8% bacterial cells ~ 5-8% cellulose and other indigestible plant fibers, inorganic materials, other cellular debris, etc. |
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For the four major organic molecules (carbohydrates, lipids, proteins, nucleic acids),
you should be able to tell me *** - where they are digested, - by what enzymes/secretions, - how and where that material is absorbed and processed CARBOHYDRATES |
- teeth and tongue break food down into smaller bits
- salivary glands moisten food and hydrolyze starch into oligosaccharides with salivary amylase - very little carbohydrate digestion in stomach; gastric amylase does play small part - about half the dietary starch is digested before it reaches the small intestine - in duodenum, pancreas releases pancreatic amylase, which converts the starch into oligosaccharides and maltose within 10 minutes - digestion completed as chyme contacts brush border of enterocytes - two brush border enzymes, dextrinase and glucoamylase hydrolyze oligosaccharides 3 or more residues long; maltase hydrolyzes maltose to glucose - brush border enzymes sucrase and lactase break down --- sucrase – breaks down sucrose into glucose and fructose --- lactase – breaks down lactose into galactose and glucose - plasma membrane of enterocytes has transport proteins that absorb monosaccharides as soon as brush border enzymes release them (about 80% is glucose) - glucose taken up by sodium-glucose transporter and transported into the ECF - sugar entering ECF increases osmolarity and draws woter osmotically from lumen of intestine - water brings more glucose and other nutrients with it by solvent drag - fructose absorbed separately by facilitated diffusion, and most is converted to glucose within the epithelial cell - monosaccharides pass through the basal membrane of cell by facilitated diffusion and are then absorbed by blood capillaries of villi into bloodstream - hepatic portal system delivers them to the liver |
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For the four major organic molecules (carbohydrates, lipids, proteins, nucleic acids),
you should be able to tell me *** - where they are digested, - by what enzymes/secretions, - how and where that material is absorbed and processed PROTEIN |
- amino acids absorbed by small intestine come from
--- dietary proteins --- digestive enzymes digested by each other --- sloughed epithelial cells digested by these enzymes --- endogenous total about 30 g/day, 44-60 g/day from diet - proteases/peptidases are the enzymes that digest proteins - absent from saliva, begin work in stomach - in stomach, pepsin hydrolyzes any peptide bond between tyrosine and phenylalanine, digesting 10-15% of dietary protein into shorter polypeptides and small amount of amino acids - pepsin inactivated when it passes into duodenum - in small intestine, pancreatic enzymes trypsin and chymotrypsin continue protein digestion by hydrolyzing polypeptides into even shorter oligopeptides - three more enzymes further take these oligopeptides apart: --- carboxypeptidase – removes amino acids from COOH end of the chain --- aminopeptidase – removes amino acids from the NH2 end --- dipeptidase – which splits dipeptides in the middle and releases the last two free amino acids (the last two are brush border enzymes, whereas carboxypeptidase is a pancreatic secretion) - amino acid absorption is similar to that of monosaccharides - enterocytes have several sodium-dependent amino acid cotransporters for different classes - dipeptides and tripeptides can also be absorbed, but they are hydrolyzed withint he enterocytes before their amino acids are released to the bloodstream - at basal surfaces of cells, amino acids behave like monosaccharides—they leave the cell by facilitated diffusion, enter the capillaries of the villus, and are carried away in the hepatic portal circulation |
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For the four major organic molecules (carbohydrates, lipids, proteins, nucleic acids),
you should be able to tell me *** - where they are digested, - by what enzymes/secretions, - how and where that material is absorbed and processed LIPID |
- hydrophobic quality of lipids makes their digestion and absorption more complicated
- fats are digested by lipases - lingual lipase, secreted by intrinsic salivary glands of the tongue, digests a small amount of fat while food is still in the mount, but becomes more active at the acidic pH of the stomach - here, it is joined by gastric lipase - together, they digest about 10-15% of fat before chyme gets to duodenum - most fat digestion occurs in small intestine by pancreatic lipase - intestinal segmentation breaks up the fat, and lecithin and bile acids emulsify fat - there is enough pancreatic lipase in small intestine to digest average daily fat intake in 1-2 minutes - lipase removes first and third fatty acids from the glycerol backbone, usually leaving the middle one; therefore the products are two free fatty acids and one monoglyceride - absorption of these products depends on minute droplets in the bile called micelles - micelles are 20-40 bile acid molecules aggregated with hydrophilic side facing out, and hydrophobic steroid rings facing inward - bile phospholipids and cholesterol diffuse into the center of the micelle to form its core -micelles pass down bile duct into duodenum, and absorb fat-soluble vitamins, more cholesterol, and the FFAs and monoglycerides produced by fat digestion - due to hydrophilic surfaces, micelles remain suspended in water more easily than free lipids - they transport lipids to surfaces of enterocytes, where lipids leave them and diffuse through plasma membrane into cells - micelles are reused, picking up another cargo of lipids and ferrying them to enterocytes - without micelles, small intestine absorbs only 40% to 50% of dietary fat and almost no cholesterol - within enterocytes, FFAs and monoglycerides are transported into the smooth endoplasmic reticulum and resynthesized into triglycerides - Golgi complex combines these with a small amount of cholesterol and coats the complex with a film of phospholipids and protein, forming droplets chylomicrons - Golgi complex packages chylomicrons into secretory vesicles that migrate to basal surface of cell and release their contents into the core of the villus - although some FFAs enter blood capillaries, chylomicrons are too large to penetrate the endothelium - they are taken up by the more porous lacteal into the lymph - white, fatty intestinal lymph, chyle, flows through larger and larger lymphatic vessels of the mesenteries, eventually passing through the cisterna chyli to the thoracic duct, then entering the bloodstream at the left subclavian vein |
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For the four major organic molecules (carbohydrates, lipids, proteins, nucleic acids),
you should be able to tell me *** - where they are digested, - by what enzymes/secretions, - how and where that material is absorbed and processed NUCLEIC ACID |
- ribonuclease and deoxyribonuclease from pancreatic juice hydrolyze these to their constituent nucleotides
- nucleosidases and phosphatases of the brush border then decompose the nucleotides into phosphate ions, ribose (from RNA) or deoxyribose (from DNA) and nitrogenous bases - these products are transported across the intestinal epithelium by membrane carriers and enter the capillary blood of the villus |
