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Respiratory > Airways Function > Flashcards

Airways Function Flashcards

1
Q

What hold open airways?

A

cartilage
- C shaped rings to make gap for oesophagus
- slightly offset that confers greater tensile strength to keep airways open
no complete ring

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2
Q

Basic function of airway? What facilitates gas exchange?

A

gas exchange - O2 to alveoli/ CO2 out of lung

  • mechanical stability (cartilage) before terminal bronchioles/alveoli
  • control of calibre by smooth muscle
  • protection and cleansing
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3
Q

Where is some of submucosal gland embedded?

A

smooth muscle

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4
Q

What is the process by which mucus is moved by cilia?

A

mucociliary transport

  • cilia beat in a metachronal rhythm where leading edge of mucus is moved a little by first cilia field which beat and then return to position
  • then next field of cilia moves mucus further
  • highly coordinated
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5
Q

Which major cell types comprise the airway epithelium?

A

goblet cells and cilia

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6
Q

Goblet cells?

A
  • contain mucin granules in highly condensed form
  • exocytosed
  • upon secretion by exocytosis intra-granular mucin rapidly expands by taking on water using ATP
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7
Q

What is the structure of cilia?

A
  • lots of mitochondria to produce ATP for cilia to beat
  • apical hooks to engage with mucus
  • inner and outer arms slide over each other to determine direction of movement
  • 9+2 structure
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8
Q

What is the function of submucosal glands?

A

Contains mucus and serous acini (functional mucus secreting unit into CD)

  • mucous cells secrete mucus, serous cells secrete antibacterials (lysozyme)
  • glands also secrete water and salts (Na, Cl)

Water serous secretions help wash out mucous secretions

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9
Q

What are the 2 mucus sources in the respiratory system?

A
  • goblet cells

- airway submucosal glands

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10
Q

What are the functions of the airway epithelium?

A
  • secretion of mucin/water/electrolyte component of mucus
  • move mucus by cilia in mucociliary clearance
  • physical barrier
  • produce regulatory/inflammatory mediators such as NO, CO, arachidonic acid metabolites e.g. prostaglandins, chemokines (IL), cytokines, proteases
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11
Q

What is NO, CO for?

A

NO produced modulate cilia beat and speed it up (made by NO synthase)
CO toxic to kill bacteria

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12
Q

What is the function of the airway smooth muscle?

A
  • structure
  • tone (airway calibre adjustment via contraction and relaxation)
  • secretion (mediators, cytokines and chemokines)
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13
Q

How does inflammation (especially chronic as in asthma) impact airway smooth muscle cells?

A

Structure

  • hypertrophy
  • proliferation

Secretion greatly increased

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14
Q

How does inflammation increase secretion?

A

bacterial products/cytokines stimulate secretion of NO, prostaglandins, cytokines, chemokines, adhesion molecules

the last 3 are involved in inflammatory cell recruitment –> prolonged inflammation

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15
Q

Describe the tracheo-bronchial circulation?

A
  • 1-5% CO (large input) very high perfusion
  • blood flow to airway mucosa is 100-150ml/min to 100g of tissue which amongst highest of tissues
  • blood returns from tracheal circulation in systemic veins
  • blood returns from bronchial circulation to both sides of heart via bronchial and pulmonary veins
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16
Q

Where do bronchial arteries arise from?

A

aorta
intercostal arteries
others

17
Q

How to achieve high perfusion?

A

-SUBEPITHELIAL MICROVASCULAR NETWORK = plexus of capillaries, veins and arteries just below epithelium

18
Q

What is the function of the subepithelium microvascular network?

A
  • good gas exchange
  • warm/humidify inspired air
  • clear inflammatory mediators/inhaled drugs
  • supply airway tissue and lumen with plasma and inflammatory cells
19
Q

What is the mechanism for plasma exudation in airways?

A

Post capillary venules are fenestrated that leak out plasma to bathe tissue

20
Q

What stimulates endothelial cells to leak out more plasma?

A
  1. C-fibre (nerve)

2. Inflammatory mediators/humoral control (histamine, platelet activating factor PAF)

21
Q

How to assess plasma exudation?

A

Evans blue dye

  • see whether it moves out of capillaries or not
  • dye autofluoresces to bright orange
22
Q

What controls airway function?

A
  1. nerves
    PNS (cholinergic) and SNS (adrenergic)
  2. regulatory and inflammatory mediators (histamine, arachidonic acid metabolites (prostaglandin, leukotriene), cytokines, chemokines)
  3. Proteinases (neutrophil elastase)
  4. Reactive gas species (O2-, NO)
23
Q

How to close airway with nervous control?

A
  1. sensory neurone detects obstruction
  2. impulse down PNS motor path
  3. constrict airway –> cough up
24
Q

What happens after constriction?

A

relax airway - in humans, no sympathetic nerve to open airways

  1. NO - vasodilation of airways by relaxation of smooth muscle cells
  2. Adrenal gland also causes relaxation
25
Q

What is the cholinergic mechanism in the airway?

A
  1. Airborne irritants/obstruction stimulate sensory nerve
  2. Central cholinergic reflex down vagus nerve using acetylcholine
  3. to parasympathetic ganglion
  4. contract smooth muscle to constrict airway
  5. increase mucus secretion from submucosal gland
  6. vasodilation
26
Q

What cells can become regulatory-inflammatory airway cells?

A

structural smooth muscle cells that become inflammatory

27
Q

What do inflammatory cells produce? What is the effect of these?

A

cells product more than one mediator - not specific
mediators have varying functional effects
1. smooth muscle contract/relax
2. secretion of mucin, water
3. plasma exudation
4. neural modulation
5. chemotaxis (attract inflammatory cells into particular airway)
6. remodelling

28
Q

What is the function of histamine?

A

contract airway smooth muscle
relax vascular smooth muscle
cause plasma exudation, mucus secretion, modulate neural function

29
Q

What 3 respiratory diseases commonly cause loss of airway control?

A

COPD 4th COD UK/USA
CF
asthma (5% population)

all have airway inflammation and airway remodelling leading to airway obstruction

30
Q

What is asthma?

A

= increased airway responsiveness to variety of stimuli leading to airway obstruction

  • obstruction varies over time and is reversible spontaneously/with drugs
  • dyspnoea, wheezing and cough (mild to severe)
  • airway inflammation leading to remodelling
31
Q

What is the pathology of asthma?

A
  • mucus plug in lumen
  • epithelial fragility
  • goblet cell hyperplasia
  • thicker BM
  • smooth muscle hypertrophy and submucosal gland hypertrophy and increase number
  • vasodilation of congested vessels
  • cellular infiltrate with mediators (eosinophil is main inflammatory cell of asthma)

also bronchoconstriction as airway wall thrown into folds as muscle contracted

32
Q

What is human neural relaxant pathway?

A

nitric oxide

33
Q

What is humoral relaxant pathway?

A

adrenaline from adrenal gland

Respiratory (7 decks)

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