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75 Cards in this Set
- Front
- Back
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What is the primary function of the respiratory system?
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gas exchange between air and circulating blood
• lungs - provide gas exchange "interface" between air & blood → supply body with O₂ and dispose of CO₂ |
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What is the secondary function of the respiratory system?
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acid-case balance (by regulating CO₂ in the blood)
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The respiratory system consists of ___ and ___ zones
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conducting and respiratory zones
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conducting zone
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from nasal cavity to terminal bronchioles "dead space"
• maintenance of open airway • humidity • adjust temperature • cleanse |
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respiratory zone
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respiratory bronchioles and alveoli
• site of gas exchange |
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respiratory muscles
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diaphragm and other muscle that promote ventilation
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ANS regulates smooth muscle to control _____ diameter
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ANS regulates smooth muscle to control bronchiole diameter
• controls airflow & resistance in lungs |
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bronchodilation
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controlled by SNS → reduces resistance
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bronchoconstriction
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controlled by PNS and histamine release (allergies) → increases resistance
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What is alveoli?
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air-filled pockets within lungs where gas exchange takes place
• ~300 million alveoli • account for most of lung's volume • provide tremendous surface area for gas exchange |
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Alveoli are patrolled by _____ _____ (dust cells) - phagocytize microbes
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alveolar macrophages
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What are Type 1 cells?
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thin, delicate endothelial cells
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What are Type 2 cells?
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produce surfactant (oily secretion - coats epithelium & reduce surface tension)
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Surface tension
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caused by attraction of H₂O molecules to each other (collapses alveoli) (premature babies - immature Type 2 cells = little/no surfactant)
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Pulmonary capillaries
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exchange CO₂ and O₂ with alveoli
• capillaries surround alveoli |
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Respiratory Membrane
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thin membrane of alveoli where gas exchange takes place (air-blood interface)
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What are the three layers that gases must diffuse across?
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1. Type 1 alveolar cells
2. Fused basal laminae between alveolar and endothelial cells 3. Endothelial cells of capillary |
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Blood supply to the lungs: pulmonary circuit
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purpose is gas exchange (also nourishes respiratory membrane)
pulmonary arteries → pulmonary capillaries → pulmonary veins |
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Blood supply to the lungs: systemic circuit
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purpose is to nourish lung tissue
Bronchial arteries → Bronchial capillaries → Pulmonary veins |
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Each lung is located within a double-layers _____ membrane
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serous
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Visceral pleura
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lines outer lung surface
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Parietal pleura
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lines inner surface of thoracic wall
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Thoracic wall:
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• floor - diaphragm
• circumference - ribs & intercostals |
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The right and left pleural cavities are separated by the _____
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mediastinum
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Each pleural cavity holds a long and lungs function ____
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independently
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pleural cavity
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holds serous fluid that reduces friction as lungs inflate/deflate
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What are the two principles affecting air movement?
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atmospheric pressure and Boyle's Law
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Atmospheric Pressure
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(Patm) ~ weight of the Earth's atmosphere (on our bodies and everything around us)
• affects air movement into and out of our lungs • our lungs have their own pressure that varies between above and below atmospheric pressure as we breathe |
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Respiratory Pressure
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is describe relative to Patm
• Negative respiratory pressure is pressure < Patm • Positive respiratory pressure is pressure > Patm |
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Boyle's Law
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defines the relationship between gas pressure and volume
↓ V of container: • each molecule travels same distance within a time period • hit wall more frequently • molecules exert more pressure on container • = ↑ P |
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Respiratory cycle
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1 inspiration (inhalation) + 1 expiration (exhalation)
causes volume changes in thoracic cavity (with expansion or contraction of diaphragm or rib cage) that create changes in pressure |
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Mechanics of Breathing
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based on pressure differences (△P) between air in lungs and atmosphere during on Respiratory Cycle
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What is the normal atmosphere pressure?
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1 atm at sea level = 760 mm Hg
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intra-alveolar pressure (Palv)
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pressure of the lungs (within alveoli)
• measured relative to atmosphere pressure |
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During relaxed breathing ....
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inhalation = −1 mm Hg inside lungs
exhalation = +1 mm Hg inside lungs |
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At rest ("Quiet" inspiration/expiration) the most important muscles are:
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diaphragm and external intracostal muscles of the ribs
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accessory respiratory muscles →
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activated only when respiration increases significantly ("forced" inspiration/exhalation)
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Quiet inspiration
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diaphragm and external intercostal muscles (inspiratory muscles) contract and the rib cages rises
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Quiet expiration
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inspiratory muscles relax and the rib cage descends due to gravity
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What are some physical properties of the lungs?
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elasticity, compliance, and airway resistance
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What is elasticity?
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stretching force
• inward recoil force of lungs due to elastic tissue and surface tension of fluid lining alveoli |
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What is compliance?
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ease of expansion
• increase compliance → easier to expand lungs → decrease work of breathing |
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What is airway resistance?
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depends of diameter of lungs
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Respiratory system adapts to changing oxygen demands by varying:
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• number of breaths per minute (respiratory rate) (
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respiratory rate
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number of breaths per minute
average = 12 breaths per minute |
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tidal volume
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volume of air moved per breath (Vt)
average = 500 mL per breath |
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Respiratory Minute Volume
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(VE) - amount of air moved per minute calculated by:
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Anatomical Dead Space
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volume of air that doesn't reach alveoli (air remaining in conducting passages - trachea, mouth, etc)
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Alveolar Dead Space
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if alveoli cease in gas exchange (e.g. damage or lined with mucus)
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Total Dead Space
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(Vd) = Anatomical Dead Space + Alveolar Dead Space
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Alveolar Ventilation (VA)
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amount of air reaching alveoli each minute
Calculated as: |
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Measurements of airflow: Respiratory volumes
TV |
TV = volume of one breath
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Measurements of airflow: Respiratory volumes
IRV |
IRV = volume inhaled with maximum effort in excess of tidal volume
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Measurements of airflow: Respiratory volumes
ERV |
ERV = volume exhaled with max. effort in excess of tidal volume
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Measurements of airflow: Respiratory volumes
RV |
RV = volume remaining in lungs after max. expiration (keeps alveoli inflated)
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Measurements of airflow: Respiratory capacities
VC |
VC = volume exhaled with maximum effort after maximum inspiration
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Measurements of airflow: Respiratory capacities
IC |
IC = volume of air inhaled after normal tidal expiration
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Functional residual capacity
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Functional residual capacity = volume in lungs after normal tidal expiration
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Total lung capacity
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Total lung capacity = maximum volume lungs can contain
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VC =
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ERV + TV + IRV
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IC =
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TV + IRV
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Functional residual capacity =
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ERV + RV
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Total lung capacity =
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VC + RV
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Pulmonary function tests
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used to asses one's respiratory status (compared with "normal" values)
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spirometer
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instrument used to measure different volumes of breathed air (water is displaced by the breathed air, and the volume can be recorded)
Helpful in distinguishing obstructive or restrictive disorders |
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Obstructive disorder
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difficult to get air out of the lungs (expiration)
• emphysema, bronchitis, and asthma |
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Restrictive disorder
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difficult to get air into the lungs (inhalation)
• mascular diseases, chest wall deformities |
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Gas exchange occurs between air in ____ & ____
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alveoli & blood → across respiratory membrane
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Gases are exchange by diffusion in response to a ____ ____
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concentration gradient
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To understand how gases are exchanged between air in alveoli & blood you will need to consider:
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1. Partial pressure of gases (Dalton's Law)
2. Diffusion of molecules between gas & a liquid (Henry's Law) |
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Dalton's Law of Partial Pressure (PP)
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• Total pressure (of gas mixture) = sum of individual gas pressures... called the partial pressures
• The partial pressure of each gas is directly proportional to its percentages in the mixture Partial pressure (PO₂, PCO₂ is the driving force for diffusion of gases • Gases diffuse from high to low pressure (down their own concentration gradient) Composition of Air: Nitrogen ~ 78.6% Water vapor ~ 0.5% Oxygen ~ 20.9% Carbon dioxide ~0.04% Atmospheric Pressure = 760 mm Hg Each gas above contributes to the total pressure → in proportion to its number of molecules (or its partial pressure) All partial pressure of molecules in air together add up to 760 mm Hg (atm pressure) |
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If you have a container with 4 gases:
50% CO₂ 25% O₂ 12.5% N₂ 12.5% CH₄ Total pressure in the container at: 800 mm Hg According to Dalton's Gas Law; what is the partial pressure of CO₂, O₂? |
CO₂ = 400 mm Hg
O₂ = 200 mm Hg N₂ = 100 mm Hg CH₄ = 100 mm Hg |
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Henry's Law of Dissolves Gases
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• When the mixture of gases is in contact with a liquid, each gas will dissolve in the liquid in proportion to its partial pressure
• The greater the concentration of a particular gas → the faster it will go into solution • At equilibrium - partial pressure in 2 phases (gas & liquid) are equal |
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Forced Exhalation includes respiratory accessory muscles such as:
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internal intercostals and abdominal muscles
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Force Inhalation includes accessory accessory respiratory muscles such as:
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Sternocleidomastoid & scalenes and Pectoralis minor and serratus anterior
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