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BRS 6 Cardio and respiratory > Structure And Function of the Airways > Flashcards

Structure And Function of the Airways Flashcards

1
Q

What is meant by dichotomous branching?

A

Where each part of the bronchi splits into two

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2
Q

What does the cartilage around the bronchi provide?

A

Mechanical stability

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3
Q

What is the main unbranched part of the airway called?

A

Trachea

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4
Q

What is the first branch of the trachea called?

A

Primary bronchus

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5
Q

What is the carina?

A

A ridge at the base of the trachea (windpipe) that separates the openings of the right and left main bronchi (the large air passages that lead from the trachea to the lungs).

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6
Q

What is an alveolar duct?

A

Ducts that connect the alveolar sacs to the bronchioles

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7
Q

Do the respiratory bronchioles contain cartilage?

A

no - they are non-cartilaginous

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8
Q

What do Type II Pneumocytes secrete and why?

A

Surfactant - in order to reduce surface tension

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9
Q

What happens to Type II cells if Type I cells become damaged?

A

They form type 1 cells

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10
Q

What do the anti-proteases produced by Type 2 pneumocytes do?

A

They degrade foreign proteases which may have entered into the airways

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11
Q

Which type of alveolar cell is involved in xenobiotic metabolism?

A

Type 2

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12
Q

Describe the structure of Type 1 alveolar cells?

A

They are thin, and very flat that form a barrier between alveolus and capillaries

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13
Q

What percentage of the alveolar surface do type 1 cells cover?

A

95%

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14
Q

What percentage of the alveolar surface do type 2 cells cover?

A

5%

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15
Q

Are there more type 1 or type 2 alveolar cells?

A

Type 2

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16
Q

What are the two basic functions of the respiratory airway?

A

Conducting oxygen to the alveoli and conducting carbon dioxide out the lungs

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17
Q

What are the three things which facilitate the efficient gas exchange?

A
  • Mechanical stability from cartilage
  • Control of calibre from smooth muscle
  • Protection and cleaning to remove foreign particles
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18
Q

What are the three regions of the pharynx?

A

Nasopharynx, oropharynx and laryngopharnx

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19
Q

What is the pharynx?

A

A common passageway for food, liquids and air

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20
Q

What do the conchae found in the nose do?

A

They contribute to the warming and humidification of intra-nasally-inhaled air

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21
Q

Why must the air be warmed before being breathed in?

A

Cool air damages the alveoli

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22
Q

What property of the conchae makes them able to humidify nasally inhaled air?

A

They are highly vascular

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23
Q

What filters out large particles from nasally inhaled air?

A

Nasal hairs

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24
Q

What is the main function of the goblet cells and submucosal glands?

A

To produce mucus

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25
Q

Label this diagram

A
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26
Q

What do the conchae, meatuses and paranasal sinuses produce?

A

Mucous to trap debris

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27
Q

What are the 7 types of airway cell types?

A 
Lining cells
Contractile
Secretory
Neuroendocrine
Connective tissue
Vascular
Immune
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28
Q

Describe the structure of the airway wall

A
  • Submucosal glands are partially embedded in the contractile smooth muscle ring
  • Goblet cells in the epithelium produce mucous and lie superficially above the ciliated epithelial layer
  • Mucociliary transport releases pollutants
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29
Q

What is contained within the granules found in the goblet cells?

A

Mucin

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30
Q

Why do the cillia contain many mitochondria?

A

They need ATP to move and waft mucous along the surface

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31
Q

What happens after the granules recieve a stimuli that they need to secrete their mucin?

A

Goblet cells take on water, causing the mucin granules to expand and release their mucous

32
Q

What part of the granule attracts the large volume of water?

A

The glycans

33
Q

What type of secretion do mucins show?

A

Constituitive

34
Q

What can stimulate mucin secretion?

A

Dust and smoke

35
Q

What is mucocilliary clearance?

A

The process by which mucus is swept by the cilia of the respiratory epithelium and propelled out the lungs and into the pharynx which results in the removal of debris and pathogens from the airways

36
Q

What do mucous acini in the airways secrete?

A

Mucous

37
Q

What do serous acini in the airways secrete?

A
  • Anti-bacterial enzymes like lysozyme
  • Water and salts
38
Q

What is the 9+2 microtubule arrangement?

A
  • Refers to how the microtubules are arranged in the cillia
  • Helps the cilia to move rhythmically
39
Q

How many cilia are there per ciliated cell?

A

Approx 200

40
Q

What is the name given to the rhythm which cilia move by?

A
  • Metachronal rhythm
  • Different lines of ciliary hair move at different times to waft mucous to the back of the throat
41
Q

What do the apical hooks do?

A

Engage with the mucous and assist with mucous removal

42
Q

List 4 functions of airway epithelium

A
  1. Secretion of mucin, water and electrolytes
  2. Mucociliary clearance
  3. Physical barrier against inhaled insult
  4. Production of regulatory and inflammatory mediators
43
Q

What does nitric oxide synthase do?

A

Produces nitric oxide (an inflammatory mediator)

44
Q

What does nitric oxide do?

A

Interacts with the calcium ions to facilitate the beating of the cilia

45
Q

What does haem oxygenase do?

A
  • Produces carbon monoxide (inflammatory mediator)
  • Haem oxygenase catalyses the degradation of haem
  • This produces biliverdin, Fe2+ and CO to activate vasodilatory pathways
46
Q

Apart from NO and CO, what other inflammatory mediators do the airway epithelium produce?

A
  • Arachidonic acid metabolites (COX, prostaglandins)
  • Chemokines (IL-8)
  • Cytokins (GM-CSF)
  • Proteases
47
Q

What does brown-staining on a histological section in the human airway show?

A

Anti-NOS antibody results in brown staining to identify NOS

48
Q

What exhibits a regulatory function on ciliary beat?

A

Nitric oxide speeds it up

49
Q

What does contraction of airway smooth muscle lead to?

A
  • Stimulates secretion into epithelial lining
  • Closes airway to prevent accidentally inhaled particles from causing choking
50
Q

Apart from secretion, what are 2 other functions of airway smooth muscle cells?

A
  • Structure of airway
  • Tone (airway caliber), contraction and relaxation
51
Q

What does the smooth muscle in the airways secrete?

A

Mediators, cytokines and chemokines

52
Q

How do the functions of airway smooth muscle cells change under inflammation?

A
  • They contribute more to structure via hypertrophy and proliferation (e.g. in asthma)
  • Secrete more mediators, cytokines and chemokines
  • Produce prostaglandins, adhesion and NO molecules
53
Q

What are some bronchoconstrictor mediators that are released from mast cells?

A

Histamine, cys-LTs and PGD2

54
Q

What are mitogens?

A

Peptides that induce cell division

55
Q

What is the blood flow levels to the airway mucosa?

A

100-150mL/min/100g

56
Q

Where do bronchial arteries arise from?

A

Many sites on the aorta and intercostal arteries

57
Q

How does the blood return from tracheal circulation?

A

Via systemic veins

58
Q

How does blood return from bronchial circulation?

A

Via bronchial and pulmonary veins

59
Q

What are the function of the tracheo-bronchial systemic circulation?

A
  • Direct gas exchange between airway tissues and blood
  • Warming and humidification of air
  • Clears inflammatory mediators
  • Clears inhaled drugs
  • Supplies airways tissue with inflammatory cells and proteinaceous plasma for plasma exudation
60
Q

What is plasma exudation?

A

The leak of plasma into the airway tissue and lumen

61
Q

What are the four mechanisms of the control of airway function?

A
  • Nerves
  • Proteases
  • Reactive gas species (e.g. NO)
  • Regulatory and inflammatory mediators
62
Q

What different types of nerves control airway function?

A
  • Parasympathetic (cholinergic)
  • Nitrous oxide sympathetic adrenergic pathway
  • Sensory nerves
63
Q

What effect does nitric oxide gas have on the smooth muscle in the airway?

A

It causes it to relax

64
Q

What is the predominant parasympathetic neurotransmitter in the airway?

A

Acetylcholine

65
Q

What does acetylcholine regulate?

A

Bronchoconstriction and mucus secretion

66
Q

How many mediators do regulatory-inflammatory cells produce?

A

They can produce more than 1

67
Q

What are the regulatory-inflammatory cells which are found in the airways?

A

Eosinophils, Neutrophils, Macrophages, Mast cells and T Cells

68
Q

What are the functions of he regulatory-inflammatory cells found in the airways?

A 
Contraction and relaxation of smooth muscle
Secretions
Plasma exudation
Neural modulation
Chemotaxis
Remodelling
69
Q

What percentage of the population suffers from ashtma?

A

5%

70
Q

What event is common with asthma, COPD and cystic fibrosis?

A

An increase in airway inflammation

71
Q

Why is it helpful for surfactant to be released by the alveolar cells?

A

Surfactant helps to create a moist surface for gas exchange to occur over as it is easier for oxygen to diffuse across the alveolar membranes when dissolved in a liquid

72
Q

How does alveolar surfactant ensure that all the alveoli inflate at roughly the same time?

A

When the alveoli inflate with air, the surfactant becomes spread out. Smaller alveoli have more surfactant per area which reduces surface tension and allows faster inflation; eventually they all inflate at the same time

73
Q

What is xenobiotic metabolism?

A

The metabolism of Nox-ous chemicals which might get into the airways

74
Q

Describe what happens in the nerve pathways between the airway and brain/spinal cord when a peanut is inhaled

A
  • The peanut goes down the airway and is detected by sensory nerves
  • Sensory nerves send an AP up the vagus nerve, through the nodose ganglion and into the brainstem
  • This sets up the cholinergic parasympathetic reflex, where ACh causes airway smooth muscle to contract to stop the peanut from going further down
  • Once the peanut is coughed up, the adrenal gland secretes adrenaline, which relaxes smooth muscle to open the airway
75
Q

What causes airway smooth muscle to relax due to the absence of sympathetic nerves that release noradrenaline?

A

Nitric oxide producing nerves cause brochondilation and airway smooth muscle relaxation

76
Q

Outline the parasympathetic ‘motor’ pathway for airway control

A
  • The vagus nerve innervates the corticospinal tract
  • ACh is secreted in the cholinergic synapse of the postganglionic fibre and gland
  • This stimulates bronchoconstriction, smooth muscle contraction and submucosal glands to secrete mucous
77
Q

Outline airway control via the adrenergic reflex

A

Adrenal gland secretes adrenaline which directly causes bronchodilation and smooth muscle relaxation

BRS 6 Cardio and respiratory (26 decks)

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