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Respiratory > 6. Structure and function of the airways > Flashcards

6. Structure and function of the airways Flashcards

1
Q

How are the cartilage rings specialised for their function in the airways?

A

C shape allows oesophagus to run down back of trachea

All rings are slightly offset which confers greater tensile strength to keep airways open

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2
Q

What is the basic function of the airways?

A

Gas exchange
Conduit pipes to:
Conduct O2 to the alveoli
Conduct CO2 out of the lung

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3
Q

What facilitates gas exchange?

A

Mechanical stability (cartilage)
Control of calibre (smooth muscle)
Protection and ‘cleansing’

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4
Q

Why are parts of submucosal glands embedded in the smooth muscle of the airway?

A

So when muscle contracts it helps squeeze mucous onto airway surface

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5
Q

Describe mucocillary transport

A

Mucous produced by submucosal glands and goblet cells
Secreted onto epithelium
Mucous wafted towards back of throat

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6
Q

What cell types found in the airway?

A 
Lining cells
Contractile cells
Secretory cells
Connective tissue
Neuroendocrine
Vascular cells
Immune cells
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7
Q

What do cilia have many of?

A

Mitochondria

To produce ATP to keep cilia beating

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8
Q

What are goblet cells dense with?

A

Electrolucent mucin granules

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9
Q

What do mucin cells take on and what is the consequence of this?

A

Water

Expand enormously

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10
Q

Describe the structure of submucosal gland.

A

Submucosal glands have functional units (acini)
Acini are either SEROUS or MUCOUS
Serous acini are found peripheral to the mucous acini
Serous: produce WATERY secretions (containing antibacterials e.g. lysozyme)
Mucous acini produce MUCOUS
Serous secretions wash over the mucous secretions into the collecting duct
Glands also secrete water and salts (e.g. Na+ and Cl-)

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11
Q

Describe the structure of a cilium.

A

9 pairs of microtubules around the outside and 2 individual microtubules on the inside (9+2 formation)
Have apical hooks that interact with the mucus
Radial spokes and rods longitudinally
Have inner and outer (dynein) arms that slide over each other to move cilia back and forth

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12
Q

What is the pattern of beating of cilia?

A

Highly synchronised metachronal rhythm

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13
Q

How many cilia per cell?

A

~200

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14
Q

State 4 functions of airway epithelium

A

Secretion of mucins, water and electrolytes
Movement of mucus by cilia
Physical barrier
Production of regulatory and inflammatory mediators

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15
Q

State 6 of the regulatory and inflammatory mediators produced by airway epithelial cells.

A 
NO
CO
Arachidonic acid metabolites e.g. Prostaglandins
Cytokines
Chemokines
Proteases
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16
Q

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

A

Epithelial cells

17
Q

What are the main 3 functions of airway smooth muscle?

A 
Provide structure to airways
Produce tone (contracts and relaxes)
Involved in secretion
18
Q

What occurs to airway smooth muscle in airway inflammation?

A

Airway smooth muscle increases in mass
=Hypertrophy and hyperplasia
Massive increase in secretion

19
Q

What inflammatory mediators can be produced by smooth muscle cells?

A

NO
Prostaglandins
Cytokines
Chemokines

20
Q

Blood flow to airway mucosa

A

100-150 ml/min/100g tissue
(amongst the highest to any tissue)
=Massive perfusion

21
Q

What is the function of the tracheo-bronchial circulation?

A

Provides perfusion to the lung tissue
Involved in WARMING and HUMIDIFYING inspired air
Clears inflammatory mediators and inhaled drugs
Supplies airway tissue with inflammatory cells and proteinaceous plasma

22
Q

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

A

Systemic veins

23
Q

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

A

To both sides of heart via

Pulmonary veins AND bronchial veins

24
Q

What is plasma exudation in the airway? Where does it usually take place?

A

POST-CAPILLARY VENULES

Post-capillary venules have endothelial cells that leak plasma out to bathe tissue

25
Q

What stimulates plasma exudation in the airway?

A 
C fibres (Nerve)
Inflammatory mediators e.g. histamine, platelet activating factor (PAF)
26
Q

In which disease is plasma exudation a feature?

A

Asthma

27
Q

What are the most important motor pathways in the airways?

A

Parasympathetic
CHOLINERGIC
‘Motor’ pathway

28
Q

Describe the cholinergic reflex.

A

Something can go into the airways and trigger a signal via an afferent pathway to the brain.
Cause a CHOLINERGIC reflex= BRONCHOCONSTRICTION

29
Q

What causes bronchodilation in humans?

A

Bronchodilation is caused by:
Release of NITRIC OXIDE from the neuronal pathway (NOTE: NO is a neurotransmitter)
Release of ADRENALINE from the adrenal medulla (part of sympathetic response)

30
Q

What does the cholinergic reflex cause?

A

Constriction of smooth muscle

Secretion of mucus

31
Q

Name 6 regulatory inflammatory cells in airways

A 
Eosinophils
Neutrophils
Macrophages
Mast cells
T lymphocytes
Structural cells e.g. smooth muscle
32
Q

State 3 respiratory diseases that involve a loss of respiratory control.

A

Asthma
COPD
Cystic Fibrosis

33
Q

What are the characteristics of asthma?

A

Increased airway responsiveness to a variety of stimuli Leads to reversible airway obstruction
Dyspnoea, wheezing and cough
Airway inflammation leads to re-modelling

34
Q

Describe 8 histological features of asthma.

A 
Mucus plug formation
Epithelial fragility 
Goblet cell hyperplasia
Thickening of the basement membrane 
Smooth muscle hypertrophy
Vasodilation 
Infiltration by eosinophils
Bronchoconstriction
35
Q

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

A

Eosinophils

36
Q

Describe the pathophysiology of Asthma

A

Epithelial fragility exposes sensory nerves, if stimulated initiates cholinergic reflex
Cholinergic reflex causes bronchoconstriction and mucous secretion
Also there is an influx of inflammatory cells which produce many inflammatory mediators resulting in remodelling of the airways e.g. submucosal gland and airway smooth muscle hypertrophy

37
Q

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

A

Smooth Muscle Hypertrophy

Increase in number of goblet cells

Respiratory (21 decks)

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