Alveolar gas exchange - Cole, Karius

Question 1

respiratory system consists of three portions:

Answer 1

• an air conducting portion (also conditions inspired air)
• resp. portion for gas exchange b/w blood and air
• mechanism of ventilation, controlled by inspiratory and expiratory muscles of the thoracic cage
• • also phonation and olfaction

Question 2

conducting portion composed of

Answer 2

nasal cavity
nasopharynx
larynx
trachea
bronchi, bronchioles and terminal bronchioles
[ In H and N]

Question 3

respiratory portions extend from

Answer 3

respiratory bronchioles to alveoli

Question 4

Fx of nasal cavity and paranasal sinuses

Answer 4

warming and moistening air

filtering dust particles present in inspired air

Question 5

resp. portion lined by ? and fx?

Answer 5

psuedostratified ciliated epithleium w/ goblet cells supported by a lamina propria with seromucous glands (moisturizing secretions) and a rich superficial venous plexus (warms incoming air)

Question 6

create turbulence to help warm and moisten air

Answer 6

superior, middle and inferior conchae

Question 7

paranasal sinuses are lined by

Answer 7

thin pseudostratified columnar ciliated epithelium with few goblet cells

Question 8

adventitia layer has

Answer 8

collagen and elastic fibers

Question 9

lamina propria contents

Answer 9

loose C.T. containing seromucous glands, elastic fibers, bone/ cartilage and sm. m.
–composition changes throughout length!

Question 10

goblet cells contains and what they produce

Answer 10

contain large, light-staining granules
hydrophilic glycoproteins called mucins - hydrated extracellularly to form mucus
[their populaiton tapers off in terminal bronchioles]

Question 11

3 secretory cell types producing airway mucus

Answer 11

1) goblet cells
2) clara cells of the terminal bronchioles
3) serous cells of the submucosal glands

Question 12

mucus contains [4]

Answer 12

1) mucins (>30 diff. types)
2) antimicrobial molecules (defensins, lysozyme and iG A) - mucins bind most bacteria, viruses and inhaled particles
3) immunomodulatory molecules (secretoglobin and cytokines)
4) protective molecules (trfoil proteins-sere barrier function, others heal epithelia- and heregulin)

Question 13

2 layers of airway mucus

Answer 13

1) a periciliary layer
2) a mucos gel layer atop the periciliary layer [polymeric MUC5AC and MUC5B continously made and secreted to replenish as ciliary beat it and its trapped contents upwards]

Question 14

implicated in bronchial carcinoid tumors, small cell lung carcinoma; serete peptide hormones (serotonin.. somatostatin.. calcitonin.. ADH..)

Answer 14

neurendocrine cells (NE, cells of Kulchitsky) 
- NE cells and basal cells rest on basal lamina

Question 15

benign focal pigmentations of oral mucosa that tend to increase significantly with tobacco consumption

Answer 15

Smoker’s melanosis

Question 16

what is metaplasia and in what pathology does it occur

Answer 16

• change to STRATIFIED SQUAMOUS [better protection]
• DECREASE in ciliated columnar cells [get decreased movement of mucus]
• INCREASE in goblet cells [protect against pollutants]
• congestion of smaller airways

Question 17

Trachea characteristics [3]

Answer 17

• 15-20 C-shaped rings of hyaline cartilage
• resp. epithelium lines most of tract (pseudostratified columnar epi. w/ goblet)
• has lamina propria..

Question 18

in trachea, the open posterior portion of the ring is bridged by

Answer 18

FIBROELASTIC LIGAMENT - collagen and elastic fibers [prevents overdistension of the lumen]
TRACHEALIS MUSCLE - sm m. results in narrowing during cough reflex [smaller diameter increases velocity of expired air, clears air passage]

Question 19

aggregates of lymphoid tissue in the bronchi are known as

Answer 19

BALT

Bronchial-associated lymphoid tissue

Question 20

secondary (lobar) bronchi have wall structure similar to main bronchi except

Answer 20

supporting cartilages form irregular plates or islands rather than rings

Question 21

bronchioles; describe their:
epithelium
goblet cells
lamina propria
cartilage and glands

Answer 21

• resp. epithelium that gradually reduces in thickness; becomes simple ciliated columnar
• lose goblet cells as go further down, replaced by clara cells (less viscous secretion); terminal bronchioles have no goblet cells
• lamina propria dominatd by spiraling layer of muscularis mucosa in the terminal bronchioles
• bronchioles don’t have cartilage and glands; only thin layer of adventitia remaining in terminal bronchioles

Question 22

Asthma - mechanism and symptoms

Answer 22

• characterized by reversible bronchoconstriction of sm. m. bundles encircling the bronchiolar lumen
• mucus hypersecreiton by goblet cells
• symp: wheezing, cough, dyspnea

Question 23

pulmonary lobule def.

Answer 23

a terminal bronchiole and the associated regions of pulmonary tissues that it supplies

Question 24

club/ clara cells description and role

Answer 24

• epithleial cells w/ dome-shaped apical domain lacking cilia
• found in terminal and resp. bronchioles
• represent 80% of epithelial cell populaiton there
• secrete surfactant that differs from that produced by type II alveolar cells

Question 25

club cells protective mechanisms

Answer 25

ALVEOLAR BRONCHIOLIZATION - after airway injury, club cells can prolfierate and migrate to replenish alveolar epithelial cells - engulf airborne toxins and break them down iva cytochrome P-450 enzymes (present in their smooth ER)

Question 26

cystic fibrosis description, mechanism, symptoms

Answer 26

- CF results in production of abnormally thick mucus by glands lining the resp. and gastrointestinal tracts - CFTR gene mutations result in defective Cl- transport and increased Na+ absorption - bacterial infections associated with thick mucus plugs consisting of MUC5AC and MUC5B polymers - symp: cough, purulent secretions, dyspnea

Question 27

respiratory portion epithelium, walls

Answer 27

terminal bronchioles DONT have alveoli - sm. m. fiber bundles form knobs bulging into lumen - the epithelium is cuboidal-to-simple squamous - elastic fibers important in bronchioles and alveolar walls

Question 28

alveoli diameter, separated by?

Answer 28

- thin-walled structures about 0.2mm in diameter - separated by interalveolar septa that consists of two simple squamous epithelial layers with interstitium (nonfenestrated capillaries embedded in an elastic connective tissue) b/w them

Question 29

alveolar epithelial cell Type I

Answer 29

represents 40% of the epithelial cell population; covers 90% of the surface; really the one making up the wall

Question 30

alveolar epithelial cell Type IIl; location?

Answer 30

- 60% of cell population, cover only 10% of the alveolar surface - preferentially located at angles formed by adjacent alveolar septa - produce surfactant!

Question 31

alveolar macrophages (dust cells) function, location, migration

Answer 31

- mononuclear phagocyte - found along alveolar surface, within interstitiutm - detached in alveolar lumen histological sections - remove debris that escapses mucus and cilia in the conducting portion fo the system - migrate to bronchi and transported via ciliary action to pharynx to be swallowed or expectorated

Question 32

why are dust cells called heart failure cells?

Answer 32

- in congestive heart failure, LV fails to keep pace with venous return from lungs - lungs become congested with blood - RBCs pass into alveoli and are phagocytosed

Question 33

emphysema disease mech, biochem behind it

Answer 33

- caused by permanent enlargement of the air spaces distal to the terminal bronchioles due to progressive, irreversible destruction of elastic tissue of the alveolar walls - can be destroyed by elastase released by neutrophils present in alveolar lumen - normally serum a1-antitrypsin (serum trypsin inhibitor) neutralizes elastase - if absent, lose elastin, lung elasticity, get COPD, emphysema - damaged elastic fibers can't recoil when stretched, as a result adjacent alveoli become confluent, produce large air spaces or blebs, the structural landmark of emphysema! - loss of elastic tissue also affects terminal and respiratory bronchioles

Question 34

blood air barrier refers to the structures O2 and CO2 must cross during gas exchange, it contains:

Answer 34

- cytoplasm of squamous eptihelial cells (Type I alvoelar cells/ pneumocytes) - fused basal lamina of type I alveolar cells and capillary endothelial cells - cytoplasm of capillary endothelial

Question 35

Acutre Respiratory Distress Syndrome (ARDS), causes, disease mech, can result in..

Answer 35

- form of pulmonary edema resulting form increased permeability of alveolocapillary membrane - cause can be cardiogenic: increase in hydrostatic pressure in alveolar capillaries - noncardiogenic: damage to alveolar epithelial lining caused by bacterial endotoxins or trauma - fluid accumulates in interstitium, alveolar spaces, small airways, stiffening the lung; impairs ventilation, adequate oxygenation of pulmonary capillary blood - can cause intractable and fatal hypoxemia - if recovered, little permanent damage

Question 36

neonatal respiratory distress sundrome

Answer 36

neonates born without surfactant (before week 24, 25) - alveolar surface tension increases - results in hypoventilaiton causing low oxygen (hypoxemia) and CO2 retention - pulmonary hypoperfusion - endothelial cell damage - ifbrin and other proteins form a hyaline membrane exudate