host defence in the lung : non immune mechanisms

Question 1

what are the functions of the lung

Answer 1

1. respiration
2. non respiratory functions

Question 2

describe respiration

Answer 2

ventilation and gas exchange :

oxygen, carbon dioxide , pH, warming and humidifying

Question 3

what are the non respiratory functions of the lung

Answer 3

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

Question 4

how much air do we inhale in a day

Answer 4

more than 10,000 litres

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

Question 5

why are respiratory infections so comparatively rare

Answer 5

because of mechanisms of host defence

Question 6

3 types of host defences

Answer 6

intrinsic

innate defence

adaptive immunity

Question 7

what is intrinsic host defences

Answer 7

they are always present

physical and chemical

eg apoptosis, autophagy, RNA silencing, antiviral proteins

Question 8

what is innate defence

Answer 8

induced by infection

( interferon, cytokines, macrophages, NK cells)

Question 9

define adaptive immunity

Answer 9

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

Question 10

where are host defences mechanisms

Answer 10

throughout the respiratory tract and involves the epithelium

Question 11

what is epithelium

Answer 11

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

Question 12

what is respiratory epithelium

Answer 12

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

Question 13

how to classify epithelium

Answer 13

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

Question 14

describe epithelium in nasal cavity and superior portion of pharynx

Answer 14

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

Question 15

describe epithelium in inferior portions of pharynx

Answer 15

stratified squamous
protects epithelium from abrasion and chemical attack

Question 16

describe epithelium in the conducting portion of the lower respiratory tract

Answer 16

a typical respiratory mucosa lines it

Question 17

describe epithelium in the finer bronchioles

Answer 17

it becomes cuboidal

Question 18

describe epithelium on gas exchange surfaces

Answer 18

consists of a delicate simple squamous epithelium

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

Question 19

do airway epithelium in different regions have the same cell types

Answer 19

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

Question 20

what are chemical epithelial barriers

Answer 20

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

Question 21

give 5 examples of chemical epithelial barriers

Answer 21

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

Question 22

does the alveolar epithelium have a host defence function

Answer 22

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

Question 23

what are the physical barriers in the respiratory tract

Answer 23

• mucus
• products of the submucosal glands

Question 24

what is airway mucus

Answer 24

a viscoelastic gel containing water, carbohydrates, proteins and lipids

Question 25

what secretes airway mucus

Answer 25

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

Question 26

what does mucus do

Answer 26

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

Question 27

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

Answer 27

by air flow and mucociliary clearance

Question 28

describe the mucociliary escalator

Answer 28

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

Question 29

what makes the epithelial strong

Answer 29

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

Question 30

what is a cough

Answer 30

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

Question 31

3 causes of cough

Answer 31

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

Question 32

what are the 2 ways coughing is initiated

Answer 32

voluntarily or reflexively

Question 33

what are the cough pathways as a defensive reflex

Answer 33

afferent and efferent pathwats

Question 34

what does the afferent limb include

Answer 34

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

Question 35

what does the efferent limb include

Answer 35

the recurrent laryngeal nerve and spinal nerves

Question 36

what is a sneeze

Answer 36

the involuntary expulsion of air containing irritants from nose

Question 37

2 causes of sneezing

Answer 37

1. irritation of nasal mucosa 2. excess fluid in airway

Question 38

sensory pathway of a sneeze

Answer 38

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

Question 39

why does airway epithelium exhibit a level of functional plasticity

Answer 39

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

Question 40

what hapens when complete repair goes wrong

Answer 40

you get pulmonary disease

Question 41

what is a cause of many obstructive lung diseases

Answer 41

abnormal epithelial responses to injury/insult

Question 42

what causes mucus plugs/ inflammation

Answer 42

mucus and inflammatory cells blocking the airways can be fatal