Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
356 Cards in this Set
- Front
- Back
|
What does the upper respiratory system consist of?
|
everything above the trachea:
Nose Palate Pharynx:naso/oro/hypo Larynx Vocal Cords Laryngeal muscles Glottis |
|
|
Functions of the nose
|
Smell
Warm inspired air-to within 1 degree of body temp Filter inspired air |
|
|
The nose
|
External nares(nostrils)
Nasal cavaties, Internal nares(choanae) |
|
|
What seperates the two nostrils and nasal cavaties?
|
The septum
|
|
|
What is the roof of the nasal cavities formed by?
|
The ethmoid bone
|
|
|
What are scroll-shaped projections of the lateral walls of the nasal cavities(also create turbulent flow)
|
Conchae(turbinates)
|
|
|
What are the nostrils and nasal cavities lined by?
|
epithelium
|
|
|
What do goblet cells in the epithelium produce?
|
mucous
|
|
|
Humidification of inspired air to near what?
|
near saturation
|
|
|
What is saturated vapor pressure at body temp?
|
47 mmHg
|
|
|
How does the nose filter inspired air?
|
1. large particles filtered by hairs in the nostrils
2. turbulent precipitation of smaller particles as they contact the mucous coating of the nasal cavities 3. when breathing through the nose, usually no particles larger the 6 microns in diameter enter the lungs |
|
|
Does the nose offer resistance to airflow?
|
Yes
|
|
|
When breathing at rest through the nose, total airway resistance is about __________that when breathing through the mouth
|
twice
|
|
|
When is mouth breathing typically used?
|
when high airflow rates(eg: exercise) are necessary
|
|
|
What forms the floor of the nasal cavities, as well as the roof of the mouth?
|
Palate
|
|
|
What portion of the palate is the hard palate?
|
the anterior portion
|
|
|
what is the soft palate attached to?
|
the posterior border of the soft palate
|
|
|
What does the soft palate separate?
|
the nasopharynx from the oropharynx
|
|
|
What projects from the midline posterior border of the soft palate?
|
the uvula
|
|
|
what does the uvula contain and what is it's function?
|
the uvula contains muscle and functions to close the nasopharynx, the uvula is important for the phonation of consonants and singing(vibrato) and is also involved in snoring and sleep apnea
|
|
|
What consists of the pharynx?
|
Nasopharynx
Oropharynx Hypopharynx (laryngeal pharynx) |
|
|
What lies above the soft palate and behind the nasal cavity?
|
The nasopharynx
|
|
|
The pharyngeal tonsils, or adenoids are lymphoid tissue that lie in the lateral wall of the ?
|
The nasopharynx
|
|
|
What lies behind the oral cavity and below the soft palate?
|
The oropharynx
|
|
|
The palatine tonsils(lymphoid tissue) lie in the lateral walls of ?
|
the oropharynx
|
|
|
What lies behind the opening to the larynx and becomes continuous with the esophagus at C6
|
The hypopharynx(laryngeal pharynx)
|
|
|
Function of the larynx
|
phonation(vibration of the vocal cords)
Protective sphincter at the opening to the lower respiratory system |
|
|
Location of the larynx
|
lies below the tongue and hyoid bone
lies in front of vertebrae C3-C6(anterior to) |
|
|
cartilagenous skeleton
|
nine cartilages
|
|
|
the single cartilages
|
Thyroid cartilage(adams apple)
Criciod cartilage Epiglottis |
|
|
leaf-shaped elastic cartilage , attached by a stalk to the back of the thyroid bone
|
Epiglottis
|
|
|
what is attached to the base if the tongue by glossoepiglottic folds on either side of the mediam glossoepiglottic fold are depression known as
|
Valleculae
|
|
|
what folds attache the sides of the epiglottis to the arytenoid and corniculate cartilages?
|
Aryepiglottic folds
|
|
|
the upper portion of the epiglottis is free and functions to cover the glottis(opening of the larynx) during what, to prevent what?
|
during swallowing to prevent aspiration
|
|
|
The arytenoid cartilages are a pair, true or false
|
True
|
|
|
The arytenoid cartilages are what shape and where do they lie?
|
pyramid-shaped structures that lie at the backk of the larynx
|
|
|
The apex of each arytenoid cartilage articulates (hinges) with what?
|
a corniculate cartilage
|
|
|
The base of each arytenoid cartilage articulates with the what?
|
cricoid cartilage
|
|
|
Each has a vocal process (projection) that is attached to a what?
|
vocal fold
|
|
|
Each has a muscular process that is attached to the posterior and lateral ____________muscle.
|
Cricoarytenoid
|
|
|
Corniculate cartilages are paired and articulate with the _________ __________and are attached to the _________?
|
arytenoid cartilages
aryepiglottic folds |
|
|
Cuneiform cartilages are paired rod-shaped cartilages that lie in the _____________folds and strengthen the ____________folds.
|
aryepiglottic
aryepiglottic |
|
|
Within the laryngeal cavity are vestibular (ventricular) folds of fibrous tissue known as what?
|
False vocal cords
|
|
|
The false vocal cords extend from the anterolateral aspects of the arytenoid cartilages to the?
|
thyroid cartilage
|
|
|
Lying inferior to the vestibular folds are the ?
|
vocal folds or TRUE VOCAL CORDS
|
|
|
The true vocal cords are pale white structures that attach anteriorly to the ________cartilage and posteriorly to the vocal processes of the arytenoid cartilages.
|
Thyroid cartilage
|
|
|
What is abduction and adduction of the vocal cords dependent on?
|
Movement of the arytenoid cartilages, which are achieved by contraction of certain laryngeal muscles
|
|
|
LARYNGEAL MUSCLES
|
-
|
|
|
What muscles abduct the vocal cords?
|
posterior cricoarytenoid muscles
|
|
|
What muscles adduct the vocal cords?
|
Lateral cricoarytenoid muscles
|
|
|
What muscle tenses the vocal cords and tilts thyroid cartilage forward?
|
Cricothyroid muscle
|
|
|
What muscle relases the vocal cords and pulls the arytenoid cartilage forward?
|
Thyroarytenoid muscle
|
|
|
What muscle closes the posterior portion of the glottis?
|
Transverse arytenoid muscle
|
|
|
GLOTTIS
|
-
|
|
|
What is the triangular opening between the vocal cords?
|
The glottis
|
|
|
What is the narrowest portion of the larynx in adults?
|
The glottis
|
|
|
In children <10 years the narrowest portion of the larynx is where?
|
at the cricoid ring
|
|
|
Sensory innervation of the upper respiratory system involves what cranial nerves?
|
V
VII IX X |
|
|
What does the trigeminal nerve (cranial nerve V) innervate?
|
1. Opthalmic division(anterior ethmoidal nerve)-anterior septum and lateral walls of the nose
2. Maxillary division (sphenopalatine nerve)-posterior portions of the nose 3. Mandibular division (lingual nerve)-general sensation to the tongue (BUT NOT TASTE) 4. Hard and soft palate |
|
|
What does the facial nerve(cranial nerve VII) innervate?
|
1. Tongue-sensation of taste
2. Hard and soft palate |
|
|
What nerve innervates the diaphragm?
|
the phrenic nerve, C3,4,5....keep the diaphragm alive!!
|
|
|
What does the glossopharyngeal nerve(cranial nerve IX) innervate?
|
1. roof of pharynx
2. tonsils 3. tongue-sensation of taste |
|
|
What does the vagus nerve(cranial nerve X) innervate?
|
1. provides sensory innervatio of the airway below the epiglottis
2. superior laryngeal nerve 2a)--internal laryngeal nerve-sensory innervation of the larynx, between the epiglottis and vocal cords 2b)--external laryngeal nerve-motor |
|
|
What does the recurrent laryngeal nerve provide?
|
sensory innervation of the larynx below the vocal cords and also the trachea
|
|
|
MOTOR INNERVATION OF THE LARYNX
|
-
|
|
|
All laryngeal muscles are innervated by the recurrent laryngeal nerve EXCEPT this one?
|
cricothyroid muscle
|
|
|
Injury to the recurrent laryngeal nerve is a potential consequence of what procedures?
|
thyroidectomy
parathyroidectomy cervical disc surgery |
|
|
What will unilateral injury to the recurrent laryngeal nerve cause?
|
paralysis of ipsilateral vocal cord; hoarseness
|
|
|
What will acute bilateral injury to the recurrent laryngeal nerve cause?
|
stridor; respiratory distress(eg. dyspnea)
|
|
|
What will chronic bilateral injury to the recurrent laryngeal nerve cause?
|
aphonia; resp. problems less frequent than with acute injury
|
|
|
What is of greater concern, unilateral or bilateral injury to the laryngeal nerve?
|
Bilateral
|
|
|
What is the cricoithyroid muscle innervated by?
|
the external laryngeal nerve
|
|
|
And what does it do to the vocal cords?
|
tenses the vocal cords
|
|
|
What will unilateral injury to the external laryngeal nerve cause?
|
minimal effects on the voice
|
|
|
What will bilateral injury to the external laryngeal nerve cause?
|
hoarseness, tiring of voice, breathing NOT affected
|
|
|
LOWER RESPIRATORY SYSTEM
|
All structures below trachea(distal) to the trachea
|
|
|
General arrangement includes successive__________branching of respiratory passageways.
|
Dichotomous(one branch gives rise to two and so on....)
|
|
|
Estimated to involve how many divisions or generations from trachea to alveoli?
|
23
|
|
|
The conducting airways(conducting zone) consists of what generations?
|
the first 16
|
|
|
Respiratory airways
|
respiratory zone
|
|
|
Conducting airways (conducting zone) include what structures?
|
Trachea
Bronchi Bronchioles |
|
|
Describe the adult trachea
|
10-15cm in length
2.5 cm in diameter blood supply primarily via the inferior thyroid artery |
|
|
Where does the trachea begin?
|
At level of cricoid cartilage (C6) and bifurcates at the carina(sternomanubrial joint, T5)
|
|
|
What anchors the trachea to the cricoid cartilage?
|
cricotracheal membrane
|
|
|
What does the wall of the trachea contain?
|
Cartilagenous rings (16-20) extend about 5/6 of the way around the trachea-prevent collapse/provide support
|
|
|
What does the posterior wall of the trachea contain?
|
slowly adapting sensory stretch receptors that play a role in the regulation of breathing, activation of these can decrease vagal efferent activity to lung resulting in dilation of bronchi
|
|
|
What receptors lie all around the tracheal wall?
|
Rapidly adapting irritant receptors, activation of these recepotors can trigger the cough reflex and bronchoconstriction
ie: small piece of potato chip could trigger this protective function |
|
|
BRONCHI
|
RIGHT & LEFT
|
|
|
Describe the right main bronchi
|
Wider
diverges from trachea at 25 degree angle Inadvertent endobronchial intubation or aspiration is more likely to occur in right |
|
|
Describe the left main bronchi
|
Diverges at 45 degree angle
|
|
|
The right main bronchus has branches that supply what lobes?
|
Upper
Middle lower lobes of the right lung |
|
|
Orifice of the right upper lobe bronchis is how many cm from the carina?
|
2.5 cm
|
|
|
The bronchus proceeds posteriorly at a ____degree angle to the right main bronchus
|
90 degree
|
|
|
In the supine position, aspirated material is more likely to enter which lobe?
|
right upper lobe
|
|
|
The left main bronchus has branches that supply what lobes?
|
upper and lower lobes of the left lung
|
|
|
Orifice of the left upper lobe bronchus is _____cm from the carina
|
5 cm
|
|
|
Cartilage in walls of the bronchi maintain?
|
patency
|
|
|
The first ___generations of bronchi have cartilaginous rings
|
7
|
|
|
BRONCHIOLES
|
Do not contain cartilage
|
|
|
Where do the bronchioles begin and end?
|
11th generation of the conducting zone airways and end at the terminal bronchioles
|
|
|
What generation has the smallest airways without alveoli?
|
16
|
|
|
Walls of the bronchioles do NOT contain cartilage BUT DO have what?
|
Smooth muscle
|
|
|
What does patency of the bronchioles depend on?
|
traction exerted by the surrounding lung tissue-diameters will fluctuate some wit insp and exp.
|
|
|
Velocity of airflow falls rapidly in the terminal bronchioles, allowing what?
|
allowing inspired particles between 1 and 5 microns in diameter to settle out on to the epithelium preventing them from going down into alveoli
|
|
|
What is the function of the conducting airways?
|
to conduct inspired air to regions of gas exchange in the lung
|
|
|
Do conducting airways participate in gas exchange?
|
NO
|
|
|
What do the conducting airways constitute?
|
Anatomic dead space
|
|
|
What is the volume of the anatomic dead space?
|
150mL (2.0-2.2mL/kg)
|
|
|
RESPIRATORY AIRWAYS
|
RESPIRATORY ZONE
|
|
|
What do the respiratory bronchioles contain?
|
occasional alveoli
no cartilagenous support |
|
|
Since there is no cartilagenous support of the resp bronchioles what does patency depend on?
|
traction exerted by surrounding lung tissue
|
|
|
Alveolar ducts are completely lined with what?
|
Alveoli
|
|
|
Each alveolar sac contains how many alveoli?
|
15-20
|
|
|
What marks the termination of airway?
|
Alveoli
|
|
|
Estimated how many alveoli?
|
300 million by age 8 or 9
|
|
|
What is the diameter and total surface area of the alveoli?
|
Diameter 0.2-0.3 mm (2/10-3/10 mincrons)
Total surface area: 50-100 m squared |
|
|
What do the type I epithelial cells provide?
|
they are flat,and provide gas exchange
|
|
|
What do the type II epithelial cells produce?
|
pulmonary surfactant (prevents collapse)
|
|
|
Other cell types in the alveoli?
|
alveolar macrophages
mast cells |
|
|
What is a source of histamine relese and plays a role in asthma?
|
Mast cells
|
|
|
Epithelial lining of the resp. passageways has mucous coating from the nose to the terminal bronchioles and does what?
|
Keeps surfaces moist
Traps small inhales particles |
|
|
Epithelial cells are ciliated from the ______to the ________ _________
|
nose
terminal bronchioles |
|
|
Cilia in the nose beat?
|
downward
|
|
|
cilia in the bronchi and bronchioles beat?
|
upward
|
|
|
What does the cilia continually move?
|
mucous and entrapped particles to the pharynx to be swallowed or expectorated
|
|
|
What does pulmonary circulatin begin with?
|
Pulmonary arteries
|
|
|
Pulmonary arteries are ______diameters and relatively_____walls; much more distensible (higher compliance) than systemic arteries
|
Large
Thin |
|
|
The pulmonary arterial system can accommodate about_____of stroke volume of the right ventricle wit a relatively small increase in pressure
|
2/3 or 66%
|
|
|
Pulmonary arteries direct what type of blood to the pulmonary capillaries?
|
Deoxygenated
|
|
|
The pulmonary capillaries, surround the alveoli and form what?
|
a dense network ("sheet" of blood) within the alveolar walls
|
|
|
What is the average diameter of the pulmonary capillaries?
|
10 microns (same as red blood cell)
|
|
|
The endothelium is relatively rich in what? What is the consequence?
|
Albumin
Possibly pulmonary edema |
|
|
How many pulmonary veins are there and what do they deliver?
|
4
oxygenated blood to the left side of the heart |
|
|
Bronchial circulation
|
accessory circulation to lungs
|
|
|
Bronchial arteries direct __________blood (1%-2% of CO) to lung tissue
|
oxygenated
|
|
|
What lung tissue?
|
connective tissue
large and small bronchi NOT to the alveoli |
|
|
Where does venous blood drain into?
|
pulmonary veins
|
|
|
Where is venous blood delivered to?
|
Left atrium
|
|
|
pulmonary veins deliver what type of blood?
|
oxygenated
|
|
|
What is the consequence of venous blood draining into pulmonary veins and delivered to the left atrium?
|
shunt
|
|
|
Pulmonary lymphatics
|
-
|
|
|
Where do the lymphatic capillaries originate?
|
in the interstitial spaces surrounding the terminal bronchioles
|
|
|
Large lymphatic vessels travel_______next to the airways and empty into what?
|
upward
thoracic duct |
|
|
What do the lymphatics do?
|
serve to remove particulate matter that crosses the alveoli into the interstitium, as well as albumin present in the interstitium
|
|
|
MECHANICS OF RESPIRATION
|
-
|
|
|
the lungs are located within the thoracic cavity, one on each side of the ?
|
mediastinum
|
|
|
What is the central compartment of the thoracic cavity and how many subdivisions does it have?
|
mediastinum
4 subdivisions each contain certain anatomical structures |
|
|
What surgical procedures involve the mediastinum?
|
CABG
thymectomy mediastinoscopy |
|
|
What is each lung surrounded by?
|
double-layered membrane known as the pleura
|
|
|
what does the parietal pleura line?
|
inner chest wall
diaphragm mediastinum is then reflects back to form the visceral pleura that covers the outer surface of the lung |
|
|
What can activate nociceptors in the parietal pleura and cause pain?
|
noxious stimule
|
|
|
What is the narrow space between the pleurae known as?
|
the pleural space (or interpleural space)
|
|
|
What does the pleural space contain?
|
several mL of pleural fluid, which acts to hold "glue" the lungs against the inner chest wall
|
|
|
The thorac cavity is normally a __________compartment
|
closed
|
|
|
What does the apex of the thoracic cavity(thoracic inlet) allow?
|
passage of the trachea, esophagus, nerves(phrenic, vagus, recurrent laryngeal, sympathetic trunk), blood vessels (carotid and subclavian arteries; internal jugular and subclavian veins), and lymphatics
|
|
|
What is the base of the thoracic cavity formed by?
|
diaphragm
|
|
|
What is the pleural space?
|
narrow space between the visceral and parietal plurae; contians several mL of pleural fluid
|
|
|
What is the pleural pressure normally?
|
subatmospheric(negative)
|
|
|
What is the negative pleural pressure due to?
|
elastic recoil of the lung and chest wall Ppl is the pressure surrounding the lung alveoli(immediately outside the alveoli)
|
|
|
At end-expiration, the average pleural pressure is approx what?
|
-5cm H2O
|
|
|
During normal inspiration, average pleural pressure decreases to approx what?
|
-7.5cm H2O
|
|
|
What may trigger pain and impair ventilation?
|
certain situation can cause gas or liquid to accumulate in the pleural space
|
|
|
What is alveolar pressure?
|
pressure within the lung alveoli
|
|
|
When the glottis is open and no air is moving in or out of the lung, alveolar pressure(PA) is equal to what?
|
atmospheric pressure(0 cm H2O)
|
|
|
During normal inspiration, PA falls to______, causing movement of a volume of air (500mL) into the lungs over a period of approx how many seconds?
|
-1cm H20
2 seconds |
|
|
During normal expiration, what does PA increase to and what does it cause?
|
+1cm H2O
causing expiration of the same volume of gas over a period of 2-3 seconds |
|
|
What is transpulmonary pressure?
|
PA-Ppl
value is normally positive |
|
|
The transpulmonary pressure is a ____________pressure that tends to keep the alveoli________?
|
distending
expanded (open) |
|
|
The transpulmonary pressure is also a measure of what?
|
elastic forces thatn tend to collapse the lung at any point of its expansion
|
|
|
What is the most important muscle of inspiration?
|
diaphragm
|
|
|
The diaphragm is a sheet of _______muscle that inserts into the lower ribs
|
skeletal
|
|
|
The diaphragm is arranged as two domes (hemidiaphragms) that form what?
|
base of the thoracic cavity and that can function independently
|
|
|
So what can the hemidiaphragms do?
|
function independently
|
|
|
What is the diaphragm as mix of?
|
50:50 mix of slow twitch and fast twitch muscle fibers
|
|
|
Slow twitch allows what?
|
endurance muscle fibers for continual breathing without fatigue
|
|
|
Fast twitch muscle fibers provide what?
|
for short bursts of maximal ventilatory effort(ie: coughing, sneezing, they fatigue quickly)
|
|
|
What are the hemidiaphragms innervated by?
|
phrenic nerves(somatic nerves)
|
|
|
Which spinal nerves do the phrenic nerves originate from?
|
C3-C5
keep the diaphragm alive :)) |
|
|
The phrenic nerves are what type of nerves and what does this mean to anesthesia?
|
Somatic nerves and so they are blocked by muscle relaxants
|
|
|
What will injury or local anesthetic block of a phrenic nerve cause?
|
paralysis of the ipsilateral hemidiaphragm
|
|
|
Contraction of the diaphragm forces abdominal contents how?
|
downward, increaseing the superior-inferior(verticle) dimension of the thorax
|
|
|
During normal tidal breathing (eupnea) the diaphragm moves approx?
|
1-2 cm (not much movement)
|
|
|
During forced breathing its total excursion may reach what?
|
10cm
|
|
|
External intercostal muscles are what?
|
skeletal muscles that connect adjacent ribs
|
|
|
External intercostal muscles slope how?
|
slope downward and forward
|
|
|
External intercostal muscle contraction pulls the ribs how?
|
upward
forward("bucket handle") |
|
|
How does this movement change diameter of the thorax?
|
increases the anterior-posterior diameter of the thorax
|
|
|
What nerves innervate the external intercostal muscles?
|
intercostal nerves(somatic nerves) that originate from spinal cord segments at the same level
|
|
|
The external intercostal muscles assist the diaphragm during eupnea but are not normally required for what?
|
not required for breathing at rest, become more important during forceful inspiration
|
|
|
What are the accessory muscles of inspiration?
|
Cervical strap muscles(infrahyoid muscles)
Sternocleidomastoid muscles |
|
|
What are the most important inspiratory accessory muscles?
|
Cervical strap muscles
|
|
|
What do the cervical strap muscles assist with?
|
elevation of the sternum and upper chest wall
|
|
|
When do the cervical strap muscles become the primay inspiratory muscles?
|
when diaphragm functin is impaired, eg: in patients with cervical cord transection-that interfers with phrenic nerve innervation
|
|
|
What do the sternocleidomastoid muscles do?
|
raise the sternum and scalene muscles(elevate the first two ribs)--NOT active during resting breating, but become important during forceful inspiration(eg: exercise)
|
|
|
During normal breathing expiration is what?
|
passive
and results from elastic recoil of the lung and chest wall-muscles are not recruited for process |
|
|
Muscles are recruited for?
|
active expiration(coughing, exercise, voluntary hyperventilation)
|
|
|
Muscles of the abdominal wall:
|
rectus abdominus
transversus abdominus internal and external oblique |
|
|
Contraction of the abdominal wall muscles does what?
|
increases intra-abdominal pressure, raising the diaphragm
|
|
|
What do intercostal muscles do?
|
pull ribs downward and inward
|
|
|
The thoracic cavity is a closed compartment so which law applies?
|
Boyles Law
**write in** |
|
|
ELASTIC PROPERTIES OF THE LUNG
|
-
|
|
|
Pressure-volume events in the lung
|
-
|
|
|
Increse in volume of the thoracic cavity does what to pleural & alveolar pressure?
|
decreases pleural pressure and alveolar pressure, allowing inspiration of air and expansion of the lungs
|
|
|
The pressure-volume curve of the lung displays Hysteresis, what is this?
|
two curves are different, insp curve is different from exp. curve
|
|
|
Slope at any point is the __________of the lung(usually measured on the insp curve)
|
Compliance
|
|
|
Compliance of the lung
|
C=changeV/changeP
|
|
|
Compliance of the lung is the extent to which the lungs ________for each unit change in pleural or transpulmonary pressure(change pressure)
|
expand (change volume)
|
|
|
What is the normal transpulmonary pressure?
|
5-10 cm H2O
|
|
|
At the normal transpulmonary pressure the lung is ______compliant(steeper slope of the compliance curve); compliance is less at low and high lung volumes, as reflected by the flatter portions of the pressure-volume curve
|
highly
|
|
|
What factors reduce compliance?
|
interstitial edema
fibrosis obesity external compression of lung tissue |
|
|
What factors increase compliance?
|
aging
emphysema-both are associated with reduced elastic tissue in the lung |
|
|
What does pursed lip breathing provide?
|
auto PEEP
voluntary closing of the glottis |
|
|
Elastic forces of the lungs that cause alveoli to collapse
|
Elastic recoil
surface tension |
|
|
Elastic recoil of interwoven fibers(collagen and elastin)
|
stretch and are distensible in the alveolar walls and around blood vessels and bronchi
|
|
|
Surface tension
|
in the liquid film lining the alveoli-air/water interface
(quantatively more important) |
|
|
Why does surface tension arise at an air/water interface?
|
interactions cause surface tension
|
|
|
What are the SI units of surface tension?
|
N/M dyne/cm
**check notes page 7** |
|
|
Surface tension tends to cause what?
|
collapse of alveoli, it effectively causes and elastic contractile force in all the alveoli
|
|
|
Surface tension accounts for approx ________% of total elastic forces in the lungs, and thus contributes significantly to the pressure-volume work of the lung, of inspiration
|
2/3 or 66%
|
|
|
What does pulmonary surfactant reduce?
|
reduces surface tension in the alveoli
|
|
|
What is surface active agent produced by?
|
Type II epithelial cells in the alveoli walls-can insert into surface and reduce surface tension
|
|
|
What is one component?
|
dipalmitoyl lecithin-amphipathic molecule
(water soluble and lipid soluble end, polar head group can insert 2 fatty acid tails and break up attractive forces) endogenous substance |
|
|
What does reduced surface tension do?
|
increases lung compliance and reduces work of breathing
|
|
|
Surfactant promotes _______of the alveoli
|
stability
|
|
|
Surface tension is reduced in __________alveoli
|
smaller
otherwise smaller alveoli would tend to empty into larger alveoli and collapse (atelectasis) |
|
|
Why the above?
|
??
|
|
|
Does surfactant undergo rapid turnover?
|
yes
|
|
|
So cessation of blood flow to a region of the lung(eg: embolus) may therefore deplete surfactant in that region and cause what?
|
atelectasis
|
|
|
When does production of surfactant begin in the fetus?
|
28-32 weeks
|
|
|
Babies born without adequate amounts of surfactant may develop what?
|
infant respiratory distress syndrome
|
|
|
Characteristics of infant resp distress syndrome:
|
Stiff lungs (low compliance)
Areas of atelectasis Fluid in alveoli with surfactant loss |
|
|
What can be used to measure the L/S ratio(lecithin/spingomyelin ratio)?
|
Amniocentesis
L/S ratio indicated the amount of mature surfactant present inthe fetus |
|
|
Effects of the thoracic wall on lung expansion
|
-
|
|
|
Like the lungs, the thoracic wall has its own what?
|
own elastic and viscous properties within the wall, collagen and elastin
|
|
|
When air is introduced into the pleural space, pleural space becomes what?
|
atmospheric
the lung collapses inward and the thoracic wall spirngs outward |
|
|
Compliance of the lung-thorac combination is approx ______that of the lung alone
|
one-half
|
|
|
Thus, twice as much transpulmonary pressure is necessary to expand the lung-thorax combination than is necessary to expand the lung alone, true or false?
|
True
|
|
|
Compliance=
|
see notes pg. 9
|
|
|
GAS FLOW AND AIRWAY RESISTANCE
|
-
|
|
|
When gas flows through a tube what exists?
|
a pressure difference (pressure drop) (delta P)
between the ends of the tube |
|
|
What does the pressure difference depend on?
|
Rate and type of flow
|
|
|
Poiseuilles's Law
|
See notes
|
|
|
Laminar flow characteristics:
|
streamline flow
parabolic velocity profile |
|
|
Poiseuille's Law
|
Pressure drop is proportional to flow rate
Resistance is inversely related to the forth power of the radius Resistance is directly related to the gas viscosity |
|
|
Does Poiseuille's law apply to turbulent flow?
|
NO
|
|
|
Turbulent flow:
|
Crosswise as well as longitudinal flow
Presssure drop is proportional to the flow rate squared Gas density is much more important than viscosity in determining the pressure drop for a given flow rate |
|
|
Where does pure laminar flow occur?
|
only in the very small airways where Reynolds numbers are very low
|
|
|
Reynolds number:
|
predictor of laminar vs. turbulent flow
|
|
|
Where does pure turbulent flow occur?
|
Trachea, particulary when flow velocities are high(eg: during exercise)-voluntary hyperventilation
|
|
|
Where is gas flow transitional?
|
In most of the tracheobronchial tree, with some turbulence occuring at branch points in the resp. passageways
|
|
|
Airway resistance
|
see notes for equation
|
|
|
What is the chief site of airway resistance?
|
medium sized bronchi and most of the pressure drop in the lower resp. system occurs up to the seventh generation
|
|
|
Because of their large number, the very small airways(less than 2mm in diameter) contribute less than ______% of total airway resistance
|
2%
|
|
|
FACTORS DETERMINING AIRWAY RESISTANCE:
|
Lung volume
Bronchiolar smooth muscle tone |
|
|
Lung volume:
Patency of the smaller bronchi and bronchioles depend on what? |
radial traction exerted by surrounding lung tissue, diameters of these airways increse as the lung expands, decreaseing their resistance
|
|
|
Conversely, as lung volume decreases, the diameters of the smaller bronchi and the bronchioles_________, causing their resistance to?
|
Decrease
Increase |
|
|
At very low lung volumes(eg: with forced expiration) some of the small airways may _______completely, particularly where?
|
Completely
base of the lung |
|
|
What does contraction of smooth muscle do to bronchioles?
|
narrows
and increases their resistance |
|
|
Reflex contraction in response to irritants in the airway do what?
|
release (ACh) causes smooth muscle constriction
-vagus nerve(ACh) mediates contraction |
|
|
Histamine
|
released from mast cells
|
|
|
Leukotrienes
|
very potent bronchoconstrictors
|
|
|
reduction in alveolar PCO2
|
results from hyperventilation
stimulates local bronchoconstriction in attempts to resotre PCO2 in affected lung tissues |
|
|
Bronchodilation reduces bronchiolar resistance
|
epinephrine
exogenous beta-2 agonists nitric oxide-bronchodilator (through cyclic GMP-produced in smooth muscle in response to nitric oxide) |
|
|
WORK OF BREATHING
|
Work of inspiration
Work of expiration Energy expenditure in breathing |
|
|
Total work of inspiration=
|
average pressure of inspiration x tidal volume
|
|
|
Compliance work(elastic work)=
|
work required to expand the lungs against the elastic forces of the lungs and thoracic wall
|
|
|
work required to overcome viscous foeces in the lungs and thoracic wall is what?
|
Tissue resistance work
|
|
|
Work required to overcome resistance to air flow through the airways is what?
|
Airway resistance work
|
|
|
During normal (upnea) breathing, most of the work of inspiration is?
|
compliance work
|
|
|
At high rates of air flow(exercise), however, the greater proportion of work is done to?
|
overcome airway resistance
|
|
|
Work of breathing is increase in what pulmonary disease?
|
Fibrosis increases compliance work and tissue resistance work
Obstructive disease increases airway resistance work |
|
|
Work of expiration
|
-
|
|
|
During normal, quiet breathing___muscle work done
|
NO
|
|
|
Work IS done, though, to overcome what?
|
airway resistance
|
|
|
With forceful breathing or when airway resistnance or tissue resistance is increased, expiratory work may become greater than inspiratory work
|
TRUE
|
|
|
Energy Expenditure in breathing
|
-
|
|
|
Efficiency of breating is about?
|
5-10%
meaning 10% of energy from ATP breakdown in the lung muscle is available for the mechanical event of inspiration |
|
|
At rest, approx ______% of total body oxygen consumption is used for the work of breathing
|
3%
|
|
|
During exercise the energy cost of breathing _________, and may be the _________factor for exercise
|
increases
limiting |
|
|
In patients with pulmonary disease, as much as _____%of total body oxygen consumption may be used for the work of breathing
|
50%
|
|
|
Tidal Volume(Vt)
|
Volume of AIR inspired, or volume of GAS expired with each breath
Approx 500mL at rest |
|
|
Inspiratory reserve volume(IRV)
|
amt of air that can be inspired over and above the resting tidal volume
Approx 3000mL |
|
|
Expiratory reserve volume(ERV)
|
amount of gas that can be expired beyond a normal tidal expiration by forceful expiration
Approx 1100mL |
|
|
Residual volume(RV)
|
volume of gas remaining in the lungs after maximal expiration
Approx 1200mL |
|
|
Pulmonary capacities
|
combinations of TWO or more pulmonary volumes
|
|
|
Inspiratory capacity(IC)
|
IC=Vt + IRV
Amount of air (approx 3500mL) that a person can inspire beginning at normal end-expiration and maximally expanding the lungs |
|
|
Functinal residual capacity(FRC)
|
FRC=ERV + RV
important in anesthesia |
|
|
FRC is:
|
Amount of gas(approx 2300mL) remaining in the lungs at the end of a normal expiration; alveolar pressure(PA)=atmospheric pressure and NO GAS flow occuring
|
|
|
At FRC what in inward recoil balanced by?
|
inward recoil of the lung is exactly balanced by outward recoil of the chest wall
|
|
|
What factors affect FRC?
|
Body habitus
Gender-FRC 10% less in females Restrictive disease Posture-FRC decreases in moving from the upright to the supine position Anesthesia reduces FRC-both induction and placing in the supine position |
|
|
Vital Capacity (VC)
|
VC=IRV + Vt + ERV
amount of gas(approx 4600mL) expelled from the lungs during a maximal expiration that follows a maximal inspiration |
|
|
Total lung capacity(TLC)
|
TLC= FRC + IC
Maximal volume (approx 5800mL) to which the lungs can be expanded with a maximal inspiratory effort |
|
|
MEASUREMENT OF LUNG VOLUMES AND CAPACITIES
|
-
|
|
|
Spirometry measures all volumes and capacities EXCEPT:
|
FRC
RV TLC |
|
|
Measurement of FRC by Helium dilution method:
|
Subject breathes from a spirometer that contains a known concentration of helium, helium is essentially insoluble in blood, SO NO alveolar uptake occuring-stays in lungs
|
|
|
Eventually the helium concentrations in the spirometer and the lung will become?
|
equal
|
|
|
By conservation of _____, the amount of helium present before equilibrium equals what?
|
Mass
equals the amount of helium present after equilibrium **see notes for equation** |
|
|
Helium dilution measures only what?
|
only the ventilated lung volume and NOT the volume of air trapped hehind collapsed airways
|
|
|
Body plethysmograph
|
measures total volume of gas in the lung, including that trapped behind collapsed airways-this is an advantage
|
|
|
Body plethysmograph
|
Subject sits in airtight box
|
|
|
At end of a normal expiration, the mouthpiece is______and the subject makes an ___________effort against a ________airway
|
closed
inspiratory closed |
|
|
Intrathoracic pressure ________and lung volume________slightly, at the same time, box pressure(surrounding the individual) ________and the box volume ________
|
decreases
increases increases decreases |
|
|
Apply Boyles Law:
|
see notes
|
|
|
Apply Boyles Law to the Lung:
|
see notes
|
|
|
In normal individuals, lung volumes mesured by helium dilution and body plethysmography are essentially what?
|
the same
|
|
|
By contrast, in patients with lung disease, the ventilated lung volume may be much less thant the total volume because why?
|
because of gas trapped behind collapsed airways
|
|
|
What can be calculated once FRC is known?
|
RV and TLC
|
|
|
Total ventilation(minute ventilation, VE)
|
product of tidal volume and RR
VE=Vt x F (F=RR) approx 6L/min at rest In extreme circumstances VE may reach 200L/min for a bried period |
|
|
Alvrolar ventilation(VA)
|
-
|
|
|
Not all tidal volume reaches the sites of gas exchange in the _______zone-some is held within the conducting airways(________ _____ _____) of the resp. system
|
respiratory
anatomic dead space |
|
|
Volume of th eanatomic dead space(VD) is approximately?
|
150mL
(2.0-2.2mL/kg) and increases slightly with age |
|
|
Calculation of alveolar ventilation
|
see notes for two equations
|
|
|
Significance of VA?
|
rate at which new air reaches the sites of gas exchange, the alveoli
VA is primary determinant of the partial pressures of oxygen and carbon dioxide in alveolar gas and thus in arterial blood |
|
|
What is physiological dead space?
|
sun of anatomic dead space and alveolar dead space-volume of air contained in alveoli that are ventilated but are poorly or NOT at all perfused
|
|
|
In individuals wiht normal respiratory function, the anatomic and physiologic dead spaces are what?
|
nearly all the same-all alveoli are functional in the normal lung
|
|
|
In patients with lung disease, the physcilogic dead space may be considerabley greater that the anatomic dead space, leading to what?
|
ventilation-perfusion inequality in the lung
|
|
|
Measurement
Bohr's method |
Measures volume of the lung that does not eliminate CO2
|
|
|
Where does all expired CO2 come from?
|
alveolar gas and NOT from the dead space
|
|
|
The Bohr method is useful for what?
|
Assessing the physiologic lung dead space
|
|
|
In individuals with normal resp function what is the VD/VT?
|
approximately 0.20-0.35
|
|
|
REGIONAL DIFFERENCES IN VENTILATION
|
-
|
|
|
Do to the weight of the lung(gravity acting on the lung), pleural pressure at the apex of the upright lung is more________than at the base
|
negative
|
|
|
Ppl increases _____cmH2O for each cm of distance from apex to base
|
0.25cmH2O
|
|
|
Alveoli in the apex of the lung have a larger resting volume than?
|
than alveoli in the base
|
|
|
Because they lie on a steeper part of the compliance curve, alveoli in the ______of the lung expand to a greater degree during normal inspiration(from FRC) thant do alveoli in the ____?
|
Base
Apex |
|
|
So, the lower (dependent) regions of the lung__________better than do the upper regions-the change in volume per unity of resting volume (change volume/volume) is greater in the base of the lung than the apex
|
ventilate
|
|
|
Paradox: at FRC, although the base of the lung is less expanded then the apex, is is better?
|
ventilated
|
|
|
Situations at low lung volumes(eg: after maximal expiration)
|
-
|
|
|
Pleural pressures are everywhere greater than those at FRC, as the lung is not as well _______ and ________recoil forces are less
|
expanded
elastic |
|
|
However, regional differences in Ppl between base and apex are still present, ie, Ppl is greater at the base of the lung
|
-
|
|
|
Ppl at the base of the lung may ______small airway pressure, causing airway (not alveoli) collapse: ventilation of alveoli in the base is not possible until what?
|
exceed
the local Ppl falls sufficiently to allow the collapsed airways to reopen |
|
|
Why does the apex ventilate better than the base?
|
because it is on the steeper portion of the pressure-volume curve and therefore ventilates better than the base
|
|
|
Dynamic airway compression
|
-
|
|
|
During FORCED expiration, there can occur reversal of the normas trasnmural pressure difference, what does result in airway compression which results from:
|
Generation of +pleural pressure
Exaggerated pressure drop along the airways due to increased airway resistance(turbulent flow and reduced lung volume |
|
|
At some point along the airways, the transmural pressure difference will become ZERO-this is the equal pressure point, or EPP; upstream (toward the mouth) frome that point what happend?
|
Ppl exceeds airway pressure
causing collapse |
|
|
What airways collapse?
|
It is the small airways (eg: resp. bronchioles) that collapse, trapping gas in the distal alveoli, the alvioli DO NOT collapse
|
|
|
What does the flow-volume curve demonstrate?
pg. 9 notes |
the phenomenon of dynamic airway compression
|
|
|
Maximal inspiration followed by maxinam expiration will show what?
|
Descending portion of flow-volume curve is independent of SPEED and INTENSITY of expiratory effort
|
|
|
Expiratory flow is limited by what?
|
pleural pressure and is
INDEPENDENT OF EFFORT |
|
|
In younger adults with normal lung function, flow of this type occurs only during what?
|
forced expiration
|
|
|
What is closing capacity (CC)?
|
the lung volume at which airways in the dependent regions of the lung begin to close during expiration
|
|
|
Closing Capacity = ?
|
CC=closing volume + RV
|
|
|
In younger individuals, closing capacity is normally well below FRC
|
TRUE
|
|
|
What can predispose to airway closure and hypoxemia?
|
Any factor that decreases FRC relative to CC, or increases CC relative to FRC
|
|
|
Why does closing capacity increase steadily with age, what is this probably responsible for?
|
the normal age-related decline in arterial PO2
|
|
|
At an average age of 44, what does closing capacity equal in the supine position?
|
FRC
|
|
|
By age 66, closing capacity is?
|
equal to or greater then FRC in the UPRIGHT position
|
|
|
When may dynamic airway compression occur during normal expiration?
|
In patients with exphysema, bronchitis or asthma
|
|
|
Why may dependent regions of the lung be only intermittently venilated?
|
as the closing volume of affected airways lies within the tidal volume, impaired gas exchange and hypoxemia occur
|
|
|
To compensate, these patients may terminate exhalation prematurely or may purse their lips, why?
|
maneuver to reduce pressure drop along airways, trying to prevent some airway collapse
|
|
|
How is FORCED VITAL CAPACITY measured?
|
Vital capacity is measured with an exhalation that is a forceful and rapid as possible
|
|
|
What does forced vital capacity provide?
|
important information regarding airway resistance
|
|
|
What is the normal ratio for FEV1 to FVC?
|
80%
|
|
|
When are both FEV1 and the ratio reduced?
|
obstructive disease
|
|
|
When are FEV1 and FVC reduced?
|
Restrictive disease, but the ratio is normal or even increased
|
|
|
Maximal mid-expiratory flow rate(MMF25-75%, or FEF25-75%
|
Sometimes more valuble
-effort-independent -May be reduced even when FEV1 is normal, thus may be a more sensitive indicator of early airway obstruction |
