Airway function

Question 1

1. How do the airways divide into smaller airways?

Answer 1

Trachea divides in two-dichrotomous branching. As they branch they get smaller and narrower. Goes from primary bronchi to secondary (lobar), then teriary (segmental). Rigth primary bronchi is wider, shorter and goes down more

Question 2

2. Describe the arrangement of cartilage rings in the airways.

Answer 2

Held open by cartilage rings-shaped in C. Trachea, oesophagus, bronchi. C shape allows stretching allowing food to go down. Also slightly offset from one another to allow greater tensile strength (at an angle)

Question 3

3. Where are submucosal glands found and what are their functions?

Answer 3

Found underneath the epithelial layer, usually nest within the smooth muscle. Made of a lot of goblet cells nested in a gland. Mucus is there to trap microbes and toxin in airway, and its constantly pushed out by cilae. Nearly 10ml mucus produced per day.

Question 4

4. Describe the tissue organisation of airways

Answer 4

Airway lumen, then epithelial layer of ciliated cells and goblet cells with mucus. Deeper in, you have submucosal glands within a smooth muscle cell layer. Outside of that you get cartilage

Question 5

4. Describe the secretion of mucus by goblet cells.

Answer 5

Mucin granules come to the apical surface and fuses with it-little pores form allowing water in. This makes mucin expand rapidely, and as pore opens more the mucus pops out-expands hundreds of time witrh water

Question 6

5. Describe the structure of submucosal gland.

Answer 6

Linked to epithelia by ciliated duct, then collecting duct. Cells are mixes of functional units (Acinii)-serous and mucous. Serous are peripheral to mucus acini. Produce watery mucus and its flushed through the duct into airway. Also secretes water, lysosymes

Question 7

6. Describe the ultrastructure of a cilium.

Answer 7

9+2 pattern – 9 outside and 2 inside. Ciliae are transmembrane with hooks at the end. The rod turns to move-need lot of energy. About 200 per cell

Question 8

7. What is the pattern of beating of cilia?

Answer 8

Metachronal rhythm-one field beats and the next one then catches up, then the next etc. As its slightly delayed, mucus is moved along

Question 9

8. State some of the regulatory and inflammatory mediators produced by airway epithelial cells.

Answer 9

NO, CO, Arachnoidic acid metabolites (prostaglandins), chemokines, cytokines, proteases. Role of epithalia, secretion of mucsin, movement of mucus, physical barrier, and those mediators

Question 10

9. In which cells of the airway do you find a high concentration of Nitric Oxide Synthase?

Answer 10

Epithalia has a lot of NOS and maybe NO-which might have a role in increasing speed of beating

Question 11

10. What inflammatory mediators can be produced by smooth muscle cells?

Answer 11

SMC role-structure, tone and secretion

Can secrete medators, cytokines and chemokines. Mostly NOS upregulation

Question 12

11. How does blood return to the heart from the tracheal circulation?

Answer 12

As normal through systemic veins

Question 13

12. How does blood return to the heart from the bronchial circulation?

Answer 13

Returns to blood to both sides of the heart through systemic AND pulmonary veins

Question 14

13. What is the function of the tracheo-bronchial circulation?

Answer 14

One of best perfused tissue-many capillaries. Helps in gas exchange, warming and humidifcation of air
Clears mediators and inhaled drugs, and good supply of Immune cells and protein plasma

Question 15

14. Explain the process of plasma exudation in the airways.

Answer 15

In post capillary venules-the endothelial cells can contract-creates gaps and openings, leading to plasma leakage. This is a normal process, and mediated by sensory nerves, histamines and other mediators. In disease like asthma, this can be excessive, producing excess histamine and sensory nerve activatoon

Question 16

15. What effect does platelet activating factor (PAF) have on exudation?

Answer 16

Causes a large increase of plasma exudation-happens in asma

Question 17

16. What are the most important motor pathways in the airways?

Answer 17

Cholinergic nerves, that go straight to brain stem (afferent and efferent, though vagus). Other controles are refulatory mechanism (histamine, etc), reactive gas species, proteinases

Question 18

17. Describe the cholinergic reflex.

Answer 18

As something large enter the airways, activates sensory pathway of cholinergic nerves, causing cholinergic effect-bronchoconstriction to stop from going in. But we don’t have sympathetic release-rely on adrenaline to relax airway. Also has a neuronal pathway, not sympathetic, which produces NO, relaxing NO

Question 19

18. What causes bronchodilation in humans?

Answer 19

We don’t have sympathetic pathways to relax. Instead rely on adrenaline to relax muscle AND some innervation that produces NO to relax SMC

Question 20

19. What does the cholinergic reflex cause?

Answer 20

After sensory nerve activation, vagus nerve to parsympathetic ganglion, then contracts SMC wit Ach, increase mucus secretion (also Ach) and maybe mild vasodilation (muscarinsic)

Question 21

20. State three respiratory diseases that involve a loss of respiratory control

Answer 21

Asthma, COPD and Cystic Firbosis

Question 22

21. What are the characteristics of asthma?

Answer 22

Clinical syndrome characterised by increased airway responsiveness to stimuli-but its REVERSIBEL (with adrenaline)-causes dyspnea, wheezing, cough. Constant inflammation causes remodelling. Can get mucus plugs in lumen with a lot of eosinophils, epithelial fragility, ticker Basment membrane, large blood vessels

Question 23

22. Describe the histological features of asthma.

Answer 23

Mucus plug in lumen, epithelial fragility, thicker Basement membrane, large blood vessels and MASSIVE EOSINOPHIL INFITRATION

Question 24

23. What cells are abundant in a mucus plug formed by asthma?

Answer 24

Eosinophils

Question 25

24. How does asthma set up a central cholinergic reflex?

Answer 25

Epithelial fragility exposes sensory nerves to mediators-activates central cholinergic effect cause SMC constriction and mucus secretion. Repeated offenses causes hypertrophy and increase of goblet cells-bracho constriction and extra mucus. Also increase chemical mediators in these cells

Question 26

25. What are the consequences of asthma to the structure of the airways?

Answer 26

Causes general brachocontriction, as the SMC clears. It would be fine in a normal person but mucus plug can then fill it very easily-then hard to breath or death