Physiology

Question 0

Right main bronchus vs. Left main bronchus

Answer 0

Right main bronchus is more prone to foreign body aspiration (vomitus) than left because right is larger diameter, shorter, oriented more vertically than left.

“Swallow a bite, goes down the right”

Question 1

Where is the Maximal airway resistance along the bronchial tree

Answer 1

Upper respiratory tract (nasal passages, mouth, pharynx, larynx) accounts for half of total airway resistance.

regional airway resistance within the first 10 generations of bronchi contributes to most of the total airway resistance of the lower respiratory tract. Resistance is maximal in the 2nd to 5th generation airways, including the segmental bronchi. (Due to highly turbulent airflow.) In contrast, airways < 2mm in diameter (bronchioles) contribute to < 20% of total airway frictional resistance.

Human respiratory tree branching structure:
CONDUCTING ZONE:
Generation 0 - Trachea 18 mm diam, 3.2 cm2 x-section
Generation 1 - primary bronchi, 12.2, 3.8
2 - lobar bronchi, 8.3mm, 4.0 cm2
3. segmental bronchi, 5.6mm, 4.3 cm2
4 subsegmental bronchi, 4.5mm, 5.3 cm2
5-10 small bronchi, 3.5-1.3 mm, 8.3-32 cm2
11-15 - bronchioles, 1.1-0.7mm, 39-68 cm2
16 - terminal bronchioles 0.6mm, 92cm2
RESPIRATORY ZONE:
17-19 respiratory bronchioles 0.5mm, >10^2cm2
20-22 alveolar ducts 0.4mm, >10^3
23+ alveolar sacs, 0.3mm, >10^4 cm2

Question 2

Flow Volume Curve for obstructive vs. restrictive diseases

Answer 2

Obstructive:
reduced expiratory airflow velocity
decreased tidal volume
increased residual volume
Ex. chronic bronchitis, emphysematous destruction of interavleolar walls

Restrictive:
decrease all lung volumes
no significant affect on expiratory flow rates

Question 3

Costal level to perform thoracentesis at: 1. Midclavicular line, 2. midaxillary line, 3. paravertebral line

Answer 3

1. midclavicular: upper margin of 7th rib, lower than 5th
2. midaxillary: upper margin of the 9th rib, lower than 7th
3. posterior scapular: upper margin of 11th rib, below 9th

insertion of needle lower increases risk of penetrating abdominal structures. Insertion of the needle on inferior margin of rib risks striking the subcostal neurovascular bundle

Question 4

Cellular changes down respiratory tract:
until what structure to cilia persist?
until what structure do goblet cells, glands and cartilage persist?
where do the epithelial cells change morphology from pseudostratified to ciliated simple cuboidal?

Answer 4

Bronchi: pseudostratified columnar ciliated epithelium with goblet cells, and submucosal mucoserious glands and cartilage

Bronchioles, terminal bronchioles and respiratory bronchioles: lack goblet cells, glands, and cartilage.

Terminal bronchioles: airway epithelium is ciliated simple cuboidal.

Epithelial cilia persist up to the end of the the respiratory bronchioles.

cilia beyond the level of mucus producing cells (goblet cells) prevents bronchiolar mucus accumulation and airflow obstruction.

Question 5

Chest compliance/Lung compliance curves and the point of Functional residual capacity

Answer 5

at FRC, the tendencies of the chest wall to expand and the lung to collapse oppose one another, creating a negative intrapleural pressure of about -5 cm H2O. During inspiration, intrapleural pressure decreases to an average of -7.5 cm H2O which then induces a slightly negative alveolar pressure that draws air into the lungs.

Center of the airway pressure-volume curve is the functional residual capacity of the lungs. it identifies the resting state where the airway pressure equals zero. At the FRC the intraplaural pressure is negative with a value of -5 cm H2O.

Question 6

Type 2 Pneumocytes

Answer 6

have two important functions:

1. regeneration of the alveolar lining following injury
2. surfactant production.

Question 7

Clara cells

Answer 7

non-ciliated secretory constituents of the terminal respiratory epithlium. They secerte clara cell secretory protein (CCSP_ which inhibtis neutrophil recruitment and activation as well as neurtophil-dependent mucin production. may also be a source of apoprotiens associated with surfactant and or precursors of mucin producing goblet cells.

Question 8

alveolar macrophages

Answer 8

lungs first line of defence against foreign particles in the air. they may accumulate within the alvoelar spaces in disease states like desquamative interstial pneumonia (DIP)

Question 9

GOblet cells

Answer 9

rarely found below the level of smallest bronchi. normally absent from terminal bronchiolar mucosa dn from alveoli.

Question 10

Pseudostartifed columnar ciliated epithelial cells ends

Answer 10

at the level of respiraotry bronchioles. turns into cuboidal ciliated epithlium. cilia absent from lining of terminal alveolar ducts and alvoelar sacs.

Question 11

location of stratified squamous epithelium

Answer 11

only the oropharynx, laryngopharynx, anterior epiglottis, upper half of hte posterior epiglottis and true vocal cords (vocal folds)
:. infection with HPV is possible on true vocal cords causing hoarseness and possible stridor. upper airway obstruction

respiratory tract, nose, paranasal sinuses, nasopharynx, most of the lanrynx and trachobronchial tree are lined with pseudostratified, columnar, mucus-secreting epithelium.

Question 12

Cough and Gag reflexes mediated by what nerves

Answer 12

the internal laryngeal nerve mediates afferent limb of cough reflex above the vocal cords. Foreign bodies fish bones can become lodged in the piriform recess and may cause damage to the nerve, impairing the cough reflex.

The afferent gag reflex is mediated by the glossopharyngeal nerve, efferent limb by the vagus nerve. Internal laryngeal nerve carries no motor fibers and mediates sensation mainly from larynx and epiglottis. stimulation of these ares induces coughing, not gagging.

Question 13

Elastin’s plasticity is due to..

Answer 13

elastin’s plasticity and ability to recoil upon release of tension is attributable to a unique form of desmosine crosslinking between 4 different lysine residues on 4 different elastin chains. This crosslinking is accomplished by teh action of extracellular lysyl hydroxylase.

Elastin vs. collagen
very few proline and lysine residues are hydroxylated in elastin
triple helix is basis of collagen, elastin does not form triple helix
triple helix formation in collagen is initiated by hydroxylation, glycosylation and interchain disulfide bridges at the C-terminus of procollagen molecule. these are not found in elastin molecules.

Question 14

V/Q ratio from base to apex

Answer 14

increases, both V and Q increase as you go from apex to base, but Q increases much much more, so from base to apex there’s an increase in V/Q ratio from 0.6-2.5.

Question 15

zone 1

Answer 15

would be found at the apex. In this zone alveolar pressure > areterial pressure > venous pressure.

arterial pressure is low in this region as the heart must pump blood uphill against the force of gravity. because the arterial pressure is lower than the alveolar pressure, the pulmonary capillaries are collapsed and there is no blood flow (dead space). These regions can form when there is low pulmonary arteial pressure (hemorrhage) or high alveolar pressure.(positive pressure ventilation)

Question 16

zone 2

Answer 16

higher areas of lung. arterial pressure > alveolar pressure > venous pressure. So alveolar pressure obstructs pulmonary capillaries toward the venous side. can be overcoem in systolel so you get pulsatile flow through pulmonary capillaries here.

Question 17

Zone 3

Answer 17

lower areas of lung. arterial pressure > venous pressure > alveolar pressure. blood flows continuously. when person is supine, all the lung is zone 3.

Question 18

Vagal stimulation effects on bronchi

Answer 18

FLow rates decrease with increasing resistance Ohms law V=IR, flow = ∆pressure/resistance

vagus nerve stimulation causes bronchoconstriction and increased mucus secretion. increase airway resistance.

mechanism is Acch to M3 receptors that induce constriction and mucous secretion.
inhibition by muscarinic acch antagonists like tiotropium and ipratropium. used for COPD and asthma.

Question 19

effects of exercise on O2 and CO2 are none, why?

Answer 19

HR and CO increase to meet oxygen demands, respiratory rate increases to eliminate excess CO2 produced. Content of O2 and CO2 in arterial blood remains relatively close to resting values at most levels of exercise. changes occur mostly in venous blood.
arterial blood remains relatively constant.

Question 20

secretions of type 1 pneumocytes, type 2 pneumocytes, clara cells, goblet cells and ciliated epithelium

Answer 20

T1PN - alveolar fluid secretory products
T2PN - phospholipid species: dipalmitoyl phosphatidylcholine - pulmonary surfactant
Clara - clara cell secretory protein (CCSP) which inhibits neutrophil recruitment and activation. may also be source of apoproteins associated with surfactant
Goblet cells - mucin (not present in epithelium of bronchioles, terminal bronchioles, respiratory bronchiles and lung acini)
ciliated epithelium of lower resp tract: mucinous substances to promote mucociliary clearance.

Question 21

difference between Minute ventilation and alveolar ventilation

Answer 21

minute ventilation is the volume of air that enters/leaves the lung in 1 minute. includes air that doesn’t participate in gas exchange.
minute ventilation = tidal volume x RR (it includes dead space ventilation)

alveolar ventilation = RR x (TV-dead space volume) (does not take into account dead space volume

Question 22

calculating dead space volume Vd

Answer 22

Vd = tidal volume x (arterial pressure of CO2 - expired pressure of CO2) / arterial pressure of CO2 [so percentage of partial pressure remaining in the blood x tidal volume].

how does this make sense? percentage of partial pressure of CO2 remaining in the blood times the total volume of air inspired = that volume of air in the lungs that does not participate in CO2 exchange. assumes that CO2 exchange is not limited by any other factor and is a perfect surrogate for “live” space.

Question 23

Lamellar bodies of T2 pneumocytes

Answer 23

store and release pulmonary surfactant into the fluid layer lining the inner surfaces of avleoli. Since the major function of surfactant is to reduce surface tension in this fluid layer, a surfactant deficiency can cause patchy alveolar atelectasis, as is seen in neonatal respiratory distress syndrome.
Ca-dependent fusion of lamellar bodies
they carry phospholipids dipalmitoyl phosphatidylcholine

Question 24

blood flow per minute in systemic and pulmonary circulations is the same when? rest? exercise?

Answer 24

both. Pulmonary circulation is part of a continuous circuit wit the systemic circulation. The rate of blood flow through the pulmonary circulation must equal the rate of blood flow in the systemic circulation at all times. The arterial pressures and oxygen contents of the pulmonary and systemic arterial systems are considerably different both at rest and during exercise.

Question 25

High altitude ABGs after 5 days

Answer 25

reduction in barometric pressure and concomitant reduction in inspired partial pressure of O2.
low O2 stimulates carotid and aortic body chemoreceptors to increase ventilatory drive.
hyperventilation results in respiratory alkalosis, low CO2, high blood pH.

to compensate, the kidneys excrete bicarb in urine, cuasing mild metabolic acidosis through decreased serum bicarb levels. this begins within 48 hours after onset of hyperventilation.

within a few hours of high alt., hyoxia beigns to stimulate renal production of erythropoietin. increases RBC production with concomitant increase in hemogllobin levels in about 10-14 days. response is sufficient to restore arterial oxygen content near sea level values.

other compensatory changes: capillary density, myoglobin concentrations, cellular mitochondria.