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cardiovascular lectures > host defence in the lung : non immune mechanisms > Flashcards

host defence in the lung : non immune mechanisms Flashcards

1
Q

what are the functions of the lung

A
  1. respiration
  2. non respiratory functions
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2
Q

describe respiration

A

ventilation and gas exchange :

oxygen, carbon dioxide , pH, warming and humidifying

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3
Q

what are the non respiratory functions of the lung

A
  1. synthesis, activation and inactivation of vasoactive substances, hormones , neuropeptides
  2. lung defence: complement activation , leucocyte recruitment, host defence proteins, cytokines and growth factors
  3. speech, vomiting, defecation
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4
Q

how much air do we inhale in a day

A

more than 10,000 litres

this means the lung is exposed to a large number of airborne pathogens which contains pathogens and particulates

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5
Q

why are respiratory infections so comparatively rare

A

because of mechanisms of host defence

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6
Q

3 types of host defences

A

intrinsic

innate defence

adaptive immunity

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7
Q

what is intrinsic host defences

A

they are always present

physical and chemical

eg apoptosis, autophagy, RNA silencing, antiviral proteins

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8
Q

what is innate defence

A

induced by infection

( interferon, cytokines, macrophages, NK cells)

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9
Q

define adaptive immunity

A

a type of immunity that develops when a person’s immune system responds to a foreign substance or microorganism, such as after an infection or vaccination

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10
Q

where are host defences mechanisms

A

throughout the respiratory tract and involves the epithelium

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11
Q

what is epithelium

A

a tissue compose of cells that line the cavities and surfaces of structures throughout the body

many glands are also formed from epithelial tissue

it lies on top of connective tissue and the two layers are separated by a basement membrane

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12
Q

what is respiratory epithelium

A

serves to moisten and protect the airways
also functions as a barrier to potential pathogens and foreign particles, preventing infection and tissue injury by action of the mucociliary escalator

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13
Q

how to classify epithelium

A

on the basis of:
- number of layers -simple or stratified
- cell shape - squamous, cuboidal, columnar

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14
Q

describe epithelium in nasal cavity and superior portion of pharynx

A

a respiratory mucosa, with mucous cells and the mucus escalator lines it

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15
Q

describe epithelium in inferior portions of pharynx

A

stratified squamous
protects epithelium from abrasion and chemical attack

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16
Q

describe epithelium in the conducting portion of the lower respiratory tract

A

a typical respiratory mucosa lines it

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17
Q

describe epithelium in the finer bronchioles

A

it becomes cuboidal

18
Q

describe epithelium on gas exchange surfaces

A

consists of a delicate simple squamous epithelium

here the distance between the air and the blood in adjacent capillaries is less than 1 um

19
Q

do airway epithelium in different regions have the same cell types

A

no they contain multiple cell types that express multiple cell-specific genges

20
Q

what are chemical epithelial barriers

A

molecules secreted from the epithelium cells that play a role in host defence

21
Q

give 5 examples of chemical epithelial barriers

A
  1. antiproteinases
  2. anti-fungal peptides
  3. anti-microbial peptides
  4. antiviral proteins
  5. opsins
22
Q

does the alveolar epithelium have a host defence function

A

yes
even though it is specialised for gas exchange it is also involved in host defence

23
Q

what are the physical barriers in the respiratory tract

A
  • mucus
  • products of the submucosal glands
24
Q

what is airway mucus

A

a viscoelastic gel containing water, carbohydrates, proteins and lipids

25
Q

what secretes airway mucus

A

mucous cells - the goblet cells of the airway surface epithelium and the submucosal glands

26
Q

what does mucus do

A

protects the epithelium from foreign material and fluid loss

has antiseptic peptides and works passively to prevent bacterial adhesion. The viscous nature of mucous traps bacteria,, which can then be actively cleared by the mucociliary escalator

27
Q

how is mucus transported from the lower respiratory tract into the pharynx

A

by air flow and mucociliary clearance

28
Q

describe the mucociliary escalator

A

mucus clearance occurs via the mucociliary escalator

bronchial cilia cells form the escalator

cilia beat in directional waves to move the mucus up the airways

allows the gradual removal of pathogens from the respiratory system

29
Q

what makes the epithelial strong

A

it is held together by tight junctions, making it robust enough to impede deeper pathogen access

30
Q

what is a cough

A

an expulsive reflex that protects the lungs and respiratory passages from foreign bodies

31
Q

3 causes of cough

A
  1. irritants - smokes, fumes, dusts etc
  2. diseased conditions eg COPD, tumours
  3. infections eg ifluenza
32
Q

what are the 2 ways coughing is initiated

A

voluntarily or reflexively

33
Q

what are the cough pathways as a defensive reflex

A

afferent and efferent pathwats

34
Q

what does the afferent limb include

A

receptors within the sensory distribution of the trigeminal, glossopharyngeal, superior laryngeal and vagus nerves

35
Q

what does the efferent limb include

A

the recurrent laryngeal nerve and spinal nerves

36
Q

what is a sneeze

A

the involuntary expulsion of air containing irritants from nose

37
Q

2 causes of sneezing

A
  1. irritation of nasal mucosa
  2. excess fluid in airway
38
Q

sensory pathway of a sneeze

A

receptor - nerve endings in nose
sensory neurone
integration centre - sneezing centre in brain stem
motor neurone
effectors - eyes, nose, lungs, diaphragm, chest muscles and parts of the mouth

39
Q

why does airway epithelium exhibit a level of functional plasticity

A

following an insult/injury the airway epithelium can effect a complete repair

this is good

40
Q

what hapens when complete repair goes wrong

A

you get pulmonary disease

41
Q

what is a cause of many obstructive lung diseases

A

abnormal epithelial responses to injury/insult

42
Q

what causes mucus plugs/ inflammation

A

mucus and inflammatory cells blocking the airways
can be fatal

cardiovascular lectures (15 decks)

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