Airways function

Question 1

Purpose of C-shaped rings of cartilage

Answer 1

C shaped so oesophagus can run down back of trachea

Slightly offset= greater tensile strength to keep airwyas open

Question 2

How is airway function facilitated?

Answer 2

Mechanical stability (cartilage)
Control of diameter (smooth muscle)
Protection+ Cleansing

Question 3

Structural organisation of airways
Outside to in
(slide 5, lecture 5)

Answer 3

-

Also the basement membrane at basal membrane of epithelium

Question 4

Purpose of submucosal gland positioning

Answer 4

When airways contract, mucus can be squeezed on smooth airway surface

Question 5

Blood vessels in airways

Answer 5

Supply tissue rather than for gas exchange

Question 6

Mucociliary transport

Answer 6

Mucus moves to back of throat

Question 7

Goblet cells features

Mucus formation?

Answer 7

Mucin granules- fuse with membrane+ releases mucin
Acini= units that secrete mucus, 2 units: mucous acini, serous acini (more watery secretion- when gland contracts, watery secretion washes out mucous acini secretion into collecting duct into airways)
Mucin comes into contact with H20+ expands massively to form mucus

Question 8

Ciliated cells features

Answer 8

Mitochondria= provides ATP for cilia to beat

Question 9

Cilia beating

Answer 9

Metachronal fashion: Leading edge of mucus moved by cilia+ swing back and move next leading edge
Sequential rather than synchronised

Question 10

Airway epithelium functions

Answer 10

Secretions of mucin, water, electrolytes
Movement of mucus
Physical barrier
Production of regulatory+ inflammatory mediators (NO)

Question 11

Airway smooth muscle under inflammation

Answer 11

Structure: Hypertrophy, Proliferation
Increased Secretion: Mediators, Cytokines, Chemokines, which bring more inflammatory cells in area= inflammatory response initiated by a previously structural cell

Question 12

Trachea-Broncho circulation
Blood returns from tracheal circulation via?
Blood returns from bronchial circulation to?
Just below epithelium?
Functions?

Answer 12

Lots of blood flow to airway mucosa (most)
Systemic veins
Both sides of heart via bronchial+ pulmonary circulation
Plexus of arteries/ capillaries and veins

Good gas exchange (so pulmonary circulation not needed)
Warming of inspired air
Humidification of inspired air
Clears inflammatory mediators
Supplies with inflammatory cells
Provides plasma exudation

Question 13

Plasma exudation

Evan’s blue dye?

Answer 13

Post-capillary venules= little gaps that leak plasma to bathe tissue
C-fibres (nerve) stimulates plasma leak+ inflammatory mediators

Evan’s blue dye= binds to albumin so can see it leaking into tissue

Question 14

What increases plasma exudation

Answer 14

PAF (platelet activated induced plasma exudation)

Question 15

Innervation of airways
Obstruction of airways response?
Difference from animals?

Answer 15

Sensed by sensory nerve fibres= relay to brain stem via nodose ganglion
Sets up cholinergic parasympathetic reflex (ACh= neurotransmitter) via vagus nerve= constricts airway= increased chance to cough up obstruction
Animals have sympathetic pathway, but we have NO relaxation pathway:
Sensed by sensory nerve fibres= relay to spinal cord via dorsal root ganglion
NO speeds up cilia+ vasorelaxant= dilates blood vessels+ airways, adrenaline does same thing

Question 16

Inflammatory cells in airways
Mediators examples?
Effect?

Answer 16

Eosinophils
Neutrophils
Macrophages
Mast Cells
T lymphocytes
Structural cells (e.g. muscle cells)

Histamine, Cytokines, Chemokines

Smooth muscle contraction, secretion, plasma exudation

Question 17

Asthma

Symptoms?
Pathology?
Pathophysiology?

Answer 17

Increased airway responsiveness to variety of stimuli
Varies over short periods of time+ reversible
Airway inflammation= re-modelling
Dyspnoea (SOB), Wheezing, Cough

Epithelial fragility
More goblet cells
BM thicker
More inflammatory cells
Bronchoconstriction- folding of smooth muscle
Mucus plug (wouldn’t have happened if diameter was normal)

Epithelial fragility exposes sensory nerves= sets up cholinergic reflex
Causes bronchoconstriction+ mucus secretion= constricted airways+ excess mucus in lumen
Also causes influx of inflammatory cells= inflammatory mediator production= remodelling (submucosal gland hypertrophy, smooth muscle hypertrophy, general inflammation)