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LSS 1 > Respiratory Systems 4 & 5 - Structure and Function of the Airways > Flashcards

Respiratory Systems 4 & 5 - Structure and Function of the Airways Flashcards

1
Q

List the basic functions of the airways, and describe how these functions are facilitated

A
  • The airways are condiut to conduct O2 to the alveoli, and conduct CO2 out of the lung
  • This is facilitated by mechanical stability, control of calibre, protection and cleansing
  • Mechanical stability is produced by cartilage
  • Control of calibre is due to smooth muscle
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2
Q

Describe the organisation of the airway structure in the trachea, in a transverse section

A
  • Outside - cartilage, which is in rings that are non-centred and C-shaped
  • Smooth muscle
  • Blood vessel
  • Submucosal glands
  • Ciliated cells covered with mucous and goblet cells
  • Airway lumen
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3
Q

Which cell types in the airway are lining cells?

A
  • Ciliated
  • Intermediate
  • Brush
  • Basal
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4
Q

Which cells types in the airway are contractile cells?

A

Smooth muscle

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5
Q

Which cell types in the airway are secretory cells?

A
  • Goblet
  • Mucous
  • Serous (glands)
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6
Q

Which cells types in the airways are connective tissue?

A
  • FIbroblasts and intersitial cells

- Produce elastin, collagen, and cartilage

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7
Q

Which cell types in the airways are neuroendocrine?

A
  • Nerves
  • Ganglia
  • Neuroepithelial bodies
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8
Q

Which cell types in the airways are vascular cells?

A
  • Endothelial
  • Pericyte
  • Plasma cells
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9
Q

Which cell types in the airways are immune cells?

A
  • Mast cells
  • Dendritic cells
  • Lymphocytes
  • Eosinophil
  • Macrophage
  • Neutrophil
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10
Q

What do mucin granules contain?

A

Mucin (glycsylated proteins) in a highly condensed form

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11
Q

What do the submucosal glands produce?

A
  • Mucous cells secrete mucus
  • Serous cells secrete antibacterials
  • Glands secrete water and salts too
  • Secreted from acini
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12
Q

What is the difference between mucous and mucus?

A
  • Mucous is the adjective (eg. mucous membrane)

- Mucus is the noun

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13
Q

Describe the structure of cilia

A
  • Apical hooks engage with mucus
  • Covered with cell membrane
  • Made of microtubules in a 9+2 formation
  • 200 per ciliated cell
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14
Q

Describe how cilia beat.

A
  • Metachronal fashion

- Synchronised, like wind blowing over a field of wheat

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15
Q

List the functions of the airway epithelium

A
  • Secrete mucus, water and electrolytes
  • Move mucus by cilia (mucociliary clearance)
  • Physical barrier
  • Produce regulatory and inflammatory mediators
  • Triggers lung repair
  • Metabolises foreign and host derived compounds
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16
Q

List the regulatory and inflammatory mediators produced by the airway epithelium, and what enzyme they are produced by

A
  • NO (by nitric oxide synthase, NOS)
  • CO (by hemeoxygenase, HO)
  • Arachidonic acid metabolites, e.g. prostaglandins (COX)
  • Chemokines, e.g. interleukin (IL)-8
  • Cytokines, e.g. GM-CSF
  • Proteases
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17
Q

List the three functions of airway smooth muscle in inflammation

A
  • Hypertrophy and proliferation
  • Tone
  • Secretion of mediators, cytokines, adhesion molecules and chemokines
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18
Q

Briefly describe the tracheo-bronchial circulation

A
  • Bronchial arteries arise from the aorta, intercostal arteries and others
  • Blood returns from the trachea via systemic veins
  • Blood returns from te bronchi to both sides of the heart via bronchial and pulmonary veins
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19
Q

List the functions of the tracheo-bronchial circulation

A
  • Good gas exchange
  • Contributes to warming of inspired air
  • Contributes to humidification of inspired air
  • Clears inflammatory mediators
  • Clears inhaled drugs
  • Supplies the airway tissue with inflammatory cells and proteinaceous plasma
20
Q

Describe the control of plasma exudation in airways.

A
  • C-fibre nerves stimulate increased plasma to leave the blood
  • Also stimulated by inflammatory mediators, such as histamine, and platelet activating factor
21
Q

List the controls of the airway function

A
  • Nerves (parasympathetic cholinergic and sympathetic adrenergic sensory)
  • Regulatory and inflammatory mediators (histamine, arachidonic acid metabolites, cytokines and chemokines)
  • Proteinases
  • Reactive gas species
22
Q

Describe the innervation of the airways

A
  • To shut the airway, sensory nerve fibres relay up to the brain and there is a parasympathetic response (acetylcholine) to close the airway and secrete a small amount of mucous
  • The airway afterwards is opened by sympathetic nerves and noradrenaline in other animals, while humans use an NO producing pathway, which speeds up cilia and is a vasodilator/dilates the airways
  • The adrenal gland also produces adrenaline to open the airways
23
Q

List the regulatory and inflammatory cells in the airways

A
  • Eosinophils
  • Neutrophils
  • Macrophage
  • Mast cell
  • T lymphocyte
24
Q

Give some examples of respiratory diseases with loss of airway control

A
  • Asthma
  • COPD
  • Cystic FIbrosis
25
Q

Define asthma and list the characteristics

A
  • A clinical syndrome characterised by increased airway responsiveness to a variety of stimuli
  • Airflow obstruction varies over short periods of time
  • Dyspnoea, wheezing and cough
  • Chronic inflammation and remodelling
26
Q

Explain the pathophysiology of asthma

A
  • Sensory nerves are activated, casing a cholinergic reflex resulting in bronchoconstriction and mucus hypersecretion
  • This is accompanied by goblet cell hyperplasia, and hypertrophy
  • Increase inflammatory mediators and growth factors
  • Vasodilation
  • Plasma leak and oedema
  • Subendothelial fibrosis
27
Q

Describe how the human airway epithelium looks in patients with COPD

A
  • Increased goblet cell numbers and increased mucous secretion
  • This is to defend against smoke
28
Q

How do goblet cells change in smokers?

A
  • Goblet cell number doubles (20% of epithelial cells in healthy people)
  • Secretions increase
  • Secretions are more viscoelastic
29
Q

How do ciliated cells change in smokers?

A
  • Severely depleted (usually 60-80% of epithelial cells in healthy people)
  • Beat asynchronously
  • Found in bronchioles
  • Unable to transport thickened mucus
30
Q

Describe the formation of stenotic bronchiolar airways in COPD

A
  • In healthy people, intact alveolar walls hold the airway open, as there is no cartilaginous material in small airways
  • In COPD patients, the walls of alveoli are disrupted so the airway doesnt open when you breathe in
  • This results in blockage of the small airways
31
Q

What is the function of club cells?

A
  • Only present in the small airways of humans
  • Previously were called CLARA cells
  • 20% of epithelial cells, less in smokers
  • Secretory cells, involved in detoxification and act as repair/progenitor cells.
32
Q

What can smoking cause in the exchange surfaces of the alveoli?

A

HOLES

33
Q

What is emphysema?

A
  • A type of COPD where the breathing tubes are narrowed and the alveoli are damaged.
  • Pulmonary fibrosis - increased synthesis of ECM makes the lungs rigid and unable to move
  • Caused by smoking
34
Q

What is the ratio of type 1 to type 2, and compare this with the percentage coverage of alveolar surface?

A
  • Ratio of type 1 to type 2 is 1:2

- However, type 1 cells are thinner and more spread out, so take up 95% of the alveolar surface

35
Q

Describe the function of epithelial type 2 cells

A
  • Contain lamellar bosies which store surfactant prior to release onto the air-liquid interface
  • Prevent alveolar collapse on expiration
  • Precursor of type 1 cells
  • Repair/progenitor cells
36
Q

Describe the function of type 1 epithelial cells

A

Facilitate gas exchange and transport

37
Q

Describe the function of stromal myofibroblasts in the alveoli

A
  • Make ECM
  • Collagen and elastin give elasticity and compliance
  • They divide to repair
38
Q

Describe the appearance of cells in alveolar fibrosis

A
  • Increased type 2 cells
  • Increased fibroblasts
  • Increased collagen deposition
39
Q

Describe the normal pathway of lung repair, and compare with the abnormal pathway

A
  • Type 1 cell death is followed by growth factors stimulating type 2 cells to become type 1 cells
  • Orchestrated by myofibroblasts
  • In abnormal repair, there are elevated growth factors so type 2 proliferation occurs with no differentiation
40
Q

List the functions of secretory epithelial cells

A
  • Includes goblet, club and type II cells
  • Secrete a protective layer to trap particles (surfactant/mucus)
  • Synthesise and release antioxidants and antiproteinases
  • Release lysosyme
  • Carry out xenobiotic metabolism (process and detoxify foreign compunds)
  • Contain cytochrome P450 and phase I/II enzymes
41
Q

Why do neutrophils and macrophages increase in smokers?

A
  • Increase by 10 fold

- Undergo phagocytosis, antimicrobial defence, xenobiotic metabolism, synthesise antioxidants

42
Q

How does the macrophage:neutrophil ratio change in COPD patients?

A

Usually 70:30 in non-smokers

30:70 in COPD patients (as neutrophils increase by a lot more than macrophages)

43
Q

What do neutrophils and macrophages do in the airways?

A
  • Neutrophils produce serine proteinases
  • Macrophages produce metalloproteinases
  • Substrates: proteins, connective tissue, elastin, collagen
  • Generate peroxides, interact with proteins and lipids, inactivates alpha-1-antitrypsin
  • Produces growth factors
44
Q

What are contained in club cells, type II cells and macrophages?

A
  • Phase I and phase II enzymes

- These are involed in xenobiotic metabolism (foreign compounds)

45
Q

How do phase I and phase II enzymes affect cigarette smoke?

A
  • Phase I enzymes are involved in production of the active compound/carcinogen
  • Phase II enzymes cause normal metabolism to water soluble metabolites
  • Absence of phase II enzymes results in DNA binding, adduct formation and mutation

LSS 1 (35 decks)

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