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Case 5 > Airways and Cough > Flashcards

Airways and Cough Flashcards

1
Q

Why is a defense system needed for lung parenchyma

A

Airways are fine and fragile

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2
Q

What is the role of hair in the nostrils

A

They trap larger particles and stop them from entering the nose and sinus cavities

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3
Q

What is present in the sinus cavities

A

A mucus layer

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4
Q

What does mucus trap

A

Anything that hasn’t previously been caught and then travels to the oropharnyx and then is swallowed

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5
Q

Describe sinus mucosa

A

They are highly vascular

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6
Q

Why do people with asthma often find that they can’t breathe when they exercise

A

Unconditioned dry, cold air which is breathed in through the mouth can trigger bronchospasm

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7
Q

What do the sinus cavities do to air

A

Humidify and moisten it meaning that air is conditioned and won’t cause bronchospasm

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8
Q

What is the function of the oropharynx

A

It contains a large number of nerves and its function it to prevent food from entering the lungs

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9
Q

What is the trachea composed of

A

Cartilaginous rings which makes it a rigid pathway

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10
Q

How many generations are there between the trachea and alveoli

A

23

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11
Q

What is the respiratory system comprised of

A

The conducting zone and the respiratory zone

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12
Q

What is the conducting zone made up of

A

Nasal cavities, nasopharynx, larynx, trachea bronchii and bronchioles

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13
Q

What does the branching of the trachea

A

Two primary (main) bronchi, secondary bronchi, tertiary bronchi then branch successively to give rise to several orders of progressively smaller airways called bronchioles, the smallest of which are called terminal bronchioles

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14
Q

What are the last components of the conducting portion of the respiratory system

A

Terminal bronchioles

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15
Q

What do terminal bronchioles give rise to

A

Respiratory bronchioles which ultimately lead to alveoli

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16
Q

Describe the defense elements of the respiratory pathway

A

Defense elements are to warm and humidify air to trap particles. With each generation surface area increases which slows down air speed meaning that air is very slow by the time it reaches alveoli. Each generation traps smaller particles

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17
Q

How much fluid do the lungs normally produce

A

Around 1.5L per day which is swallowed and recycled

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18
Q

What does it mean if the sputum becomes green

A

It contains neutrophils

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19
Q

How many tracheal cartilages keep the lumen of the trachea open

A

20 tracheal cartilages

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20
Q

Describe the tracheal cartilages

A

C-shaped rings of hyaline cartilage

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21
Q

What are the gaps between the rings or cartilage filled by in the trachea

A

Trachealis muscle

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22
Q

Describe the trachealis muscle

A

A bundle of smooth and fibroelastic tissue

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23
Q

What do the hyaline cartilage and trachealis muscle do in the trachea

A

Hold the lumen of the trachea open but allow flexibility during inspiration and expiration

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24
Q

How are the respiratory mucosa and submucosa adapted

A

To warm and moisten air and to trap particles in the mucus

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25
Q

Describe the epithelium of the trachea

A

Pseudostratified epithelium. Also mosaic cells in the epithelium meaning that it contains secretory (goblet cells)

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26
Q

What do goblet cells produce

A

Mucus which is sticky

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27
Q

What do serous cells produce

A

Water

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28
Q

What are locates in the connective tissue below the pseudostratified epithelium of the trachea

A

Seromucus glands

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29
Q

What is the respiratory mucosa made up of

A

The epithelium and supporting lamina propria

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30
Q

Describe the epithelium of the trachea

A

Tall columnar pseudostratified with cilia and goblet cells

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31
Q

What does the lamina propria contain

A

Elastin which plays a role in the elastic recoil of the trachea during inspiration and expiration together with blood vessels that warm the air

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32
Q

Describe the sub-mucosa and associated secretions

A

Sub-mucosa contains gland which are mixed sero-mucus glands. The watery secretions from the serous glands humidify the inspired air. The mucous together with the mucus from the goblet cells trap particles from the air which are transported upwards towards the pharynx by cilia on the epithelium

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33
Q

Describe the tertiary bronchus

A

There is a smooth muscle ring (bronchial smooth muscle). Elastin in the submucosa. Tall columnar epithelium, less cartilage. Mucosa is folded

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34
Q

Describe the role of the bronchial smooth muscle in the tertiary bronchus

A

Used to control the diameter and length of the bronchii- contracts during expiration to help expel air

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35
Q

Describe the epithelium of the tertiary bronchus

A

Tall columnar not pseudostarified and contains very few goblet cells. Epithelium is quite corregated meaning that it can change shape easily

36
Q

What is the diameter of bronchioles

A

1mm or less

37
Q

Describe bronchioles

A

Epithelium is made up of ciliated columnar cells in larger bronchioles or non-ciliated columnar cells in smaller bronchioles. No goblet cells but are Clara cells. No cartilage. Corregated epithelium

38
Q

Describe Clara cells

A

Found in bronchioles, they are secretory and secrete one component of surfactant

39
Q

Describe the change of airway wall structure at the three principle levels (bronchus, bronchioles, alveolus)

A

The epithelial layer gradually becomes reduced from pseudostratified to cuboidal and then to squamous but retains its organisation as a mosaic of lining and secretory cells. The smooth muscle layer disappears in the alveoli. The fibrous coat contains cartilage only in bronchi and gradually becomes thinner as the alveolus is approaches. Basement membrane is continuous throughout

40
Q

What are submucosal glands especially regulated by

A

Parasympathetic nerves which cause secretion

41
Q

What does stimulation of sensory afferents in the airway lead to

A

Stimulation of the parasympathetic neurones and thus secretions from the glands

42
Q

What are the afferents in the neural reflexes stimulated by

A

Irritating stimuli or inflammation

43
Q

Describe the reflexes

A

They may pass through the CNS or take place purely in the walls of the airways

44
Q

Describe sympathetic effects on the submucosal glands

A

Effects are rather weak with alpha1 adrenergic inhibiting secretion and beta2 stimulating secretion

45
Q

How do inflammatory paracrines regulate submucosal glands

A

Stimulate secretion

46
Q

Describe neural reflexes

A

Occur starting with stimulation of sensory afferents in the airways which can lead to stimulation of parasympathetic neurones and thus secretion from the glands. The afferents in these neural reflexes are stimulated by irritating stimuli or inflammation

47
Q

What are the two components of the mucus layer

A

Mucus and water

48
Q

What is the prime regulatory factor promoting secretion of fluid

A

Active transport of Cl- ions via phosphorylation of protein kinase causes release of water which lubricates. Net movement of Cl- from interstitial space into lumen= prime regulatory factor

49
Q

What is the level of hydration of the mucus in the airways determined by

A

The amount of water secreted across the epithelium lining the airways. The amount of water secreted is determined by the net movement of ions across the epithelium. When there is a greater net movement of ions more water follows by osmosis

50
Q

Describe the movement of chloride ions in the mucus layer

A

Chloride ions enter the epithelial cells from the interstitial fluid via a cotransporter which also carries sodium ions and potassium ions. Chloride ions enter the lumen via a regulated chloride channel. A second messenger, cyclic AMP, activates a kinase that phosphorylates the chloride channel which leads to its opening

51
Q

What does the fact that the CT scan shows airways that are dilated and thickened walls mean

A

Results in bronchiectasis, as a result the patient would have excess sputum and their ciliary network would be compromised meaning that they would have to constantly cough

52
Q

What neural pathways exist in the lungs

A

Parasympathetic system, sympathetic system, sensory fibres, nonadrenergic, noncholinergic (NANC) efferent system

53
Q

What feels pain in relation to the lungs

A

Not the lungs themselves, only the pleural surface

54
Q

What is the main effector system in the lungs

A

The parasympathetic system

55
Q

Which systems are rudimentary in the lungs

A

The sympathetic system and sensory fibres

56
Q

Which nerve does the parasympathetic system run through

A

The vagus nerve

57
Q

What are the 3 main actions of the parasympathetic system on the lungs

A

Bronchoconstriction, vasodilation, mucus gland and goblet cell secretion

58
Q

Describe acetylcholine actions

A

M1-Rs increase preganglionic transmission. M2Rs reduce further ACh release from nerve endings. M3-Rs stimulate airway smooth muscle contraction

59
Q

What do the vagus nerves and second to fifth thoracic sympathetic ganglia contribute fibres to

A

The anterior and posterior plexuses in the peribronchovascular connective tissue at the lung roots

60
Q

What are the two main plexuses fibres form on entering the lungs

A

The peribronchial plexus which follows the bronchi and contains both myelinated and unmyelinated nerves and the periarterial plexus containing only unmyelinated fibres

61
Q

Describe preganglionic parasympathetic fibres

A

Arise primarily from cell bodies in medullary nuclei, and are carried in the vagus nerve to the lower airways. They synapse with postganglionic fibres in small ganglia along the vagus nerve and in local ganglia in the airway walls, predominantly in the larger central airways. The ganglia are mainly located external to the smooth muscle and cartilage, with only a few smaller ganglia within the submucosa

62
Q

What neurotransmitters do parasympathetic ganglia and postganglionic fibres contain

A

Acetylcholine, vasointestinal peptide (VIP), peptide histidine isoleucine/methionine, helodermin, galanin and the enzyme nitric oxide synthase (NOS)

63
Q

What do postganglionic cholinergic fibres supply

A

Bronchial smooth muscle and that stimulation causes bronchoconstriction, the effects of which can be inhibited by atropine. In addition, they also supply bronchial and pulmonary vascular smooth muscle causing relaxation and vasodilation

64
Q

What do vagal efferent fibres also innervate

A

The mucous glands of the large airways and goblet cells causing an increase in secretion in both

65
Q

What are the 3 effects sympathetic stimulation has

A

Vasoconstriction. bronchdilation (minor effect), modulate cholinergic transmission

66
Q

What is the cough reflex mediated by

A

Sensory afferent nerves

67
Q

What are the two main defense reflexes

A

Cough and expiration

68
Q

What elicits the defense reflexes

A

Mechanical or chemical irritation of the airway mucosa

69
Q

Describe the cough reflex

A

Forces explosive manoeuver usually against a closed glottis. Subject draws air into the lungs to reinforce a subsequent explosive effort

70
Q

Describe the expiration reflex

A

Strong expiration without a preceding drawing in of air which aims to prevent aspiration of material into the lungs

71
Q

Describe the C fibres in the lungs

A

Arise from jugular neurones, conduction velocity

72
Q

Describe the A fibres in the lungs

A

Arise from nodose neurones, conduction velocity >3m/s, Aδ fibres are thin fibres, Aβ fibres and thick unmyelinated fibres.

73
Q

Which fibres respond to mechanical stimuli and are responsible for expulsion

A

A fibres

74
Q

Which fibres respond to chemical stimulation

A

C fibres e.g. capsaicin in chilli acts on TRPV1 receptors. When neuropeptides are released they have a potent effect on the epithelium itself and cause vasodilation and mucus secretion

75
Q

What does the majority of afferent innervation of the lung occur via

A

The vagus nerve

76
Q

What are the proposed mechanisms for the role of tachykinins in cough

A

Tachykinin containing c-fibres when stimualated antidromically release SP, CGRP and neurokinin A. These neuropeptides act on neurokinin 1,2 or 3 receptors which induce pronounced bronchoconstriction and localised inflammation

77
Q

What is the primary characteristic of neurogenic inflammation

A

Increased vascualr permeability allowing leakage of serum inflammatory proteins into tissues and is associated with increased influx of inflammatory cells

78
Q

What are NK-1 effects

A

Increased mucus hypersecretion, and airway smooth muscle contraction

79
Q

What are the causes of chronic cough

A

Asthma, gastro-oesophageal disorders, post-viral cough, bronchiectasis, intersitial lung disease, idiopathic cough, rhinosinutis

80
Q

What cells play a key role in asthma

A

Eosinophils result in smooth muscle contracting

81
Q

How can reflux of gastro juices into the lungs cause chronic cough

A

C-fibres are highly sensitive to low pH

82
Q

How can viruses cause a chronic cough

A

Some viruses cause the epithelial layer to shed resulting in the basemenet membrane being exposed. The epithelium takes a while to regrow meaning that the cough persists even after the virus has gone

83
Q

What happens in bronchiectasis

A

Sputum builds up

84
Q

What happens in interstitial lung disease

A

C-fibres are upregulated

85
Q

What do you need to think of if a cough lasts for longer than 8-12 weeks

A

Other things that may be causing it e.g. COPD, ACE inhibitor therapy, lung neoplasm. pyschogenic cough, tic disorder

86
Q

What are progressive conditions

A

Lung cancer and interstitial lung disease

Case 5 (8 decks)

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