Structure and function of the airways

Question 1

What type of branching do the airways do?

Answer 1

-dichotomus

Question 2

What provides the mechanical stability to the lungs?

Answer 2

-cartilage

Question 3

What are the lobes of the lungs?

Answer 3

3 right lung lobes:

• superior
• middle
• inferior

2 left lung lobes:

• superior
• inferior

Question 4

What are the different parts of the bronchus?

Answer 4

• primary
• secondary (lobar)
• tertiary (segmental)

Question 5

Compare Type I and Type II cells in the alveolar unit.

Answer 5

Type I cells:

• very thin, delicate barrier (facilitates gas exchange)
• cover 95% of alveolar surfaces

Type II cells:

• replicate to replace Type I cells
• secrete surfactant (reduced surface tension), antiproteases
• xenobiotic metabolism
• greater in number but only cover 5% of surfaces

Question 6

What are the basic functions of the respiratory airways and what is this facilitates by?

Answer 6

• getting air efficiently to the gas exchange region
• keeping the pipework clear
• conduit to conduct O2 to alveoli
• conduit to conduct CO2 out of the lung
• gas exchange

Facilitated by:

• mechanical stability (cartilage)
• control of calibre (smooth muscle)
• protection and ‘cleansing’

Question 7

What is the pharynx?

Answer 7

-common passageway for food, liquids and air

Question 8

What is the conchae?

Answer 8

• highly vascular- contribute to warming and ‘humidification; of intra-nasally-inhaled air
• nasal hairs filter out large particles

Question 9

Give the cells types which are lining cells.

Answer 9

• ciliated
• intermediate
• brush
• basal

Question 10

Give the cells types which are contractile cells.

Answer 10

-smooth muscle (airway, vasculature)

Question 11

Give the cells types which are secretory cells.

Answer 11

• goblet (epithelium)
• mucous
• serous (glands)

Question 12

Give the cells types which are found in connective tissue.

Answer 12

• fibroblast

- interstitial cell (elastin, collagen, cartilage)

Question 13

Give the cells types which are neuroendocrine cells.

Answer 13

• nerves
• ganglia
• neuroendocrine cells
• neuroepithelial bodies

Question 14

Give the cells types which are vascular cells.

Answer 14

• endothelial
• pericyte
• plasma cell (+ smooth muscle)

Question 15

Give the cells types which are immune cells.

Answer 15

• mast cell
• dendritic cell
• lymphocyte
• eosinophil
• macrophage
• neutrophil

Question 16

Which cell secretes mucin?-

Answer 16

-by guinea pig tracheal goblet cell

expansion of intra-granular mucin upon secretion; to ATP, Real Time

Question 17

Which cell secretes mucin?

Answer 17

-by guinea pig tracheal goblet cell

expansion of intra-granular mucin upon secretion; to ATP, Real Time

Question 18

What do serous cells secrete?

Answer 18

-anti-bacterial enzymes (e.g lysozyme)

Question 19

What do the submucosal glands also secrete, other than mucus and enzymes?

Answer 19

-water and salts

Question 20

What is an axoneme?

Answer 20

-a strand of a cilium

Question 21

How many cilia are there roughly per ciliated cell?

Answer 21

-about 200 cilia

Question 22

What are the functions of the airway epithelium?

Answer 22

• secretion of mucins, water and electrolytes, components of ‘mucus’
• movement of mucus by cilia- mucociliary clearance
• physical barrier
• production of regulatory and inflammatory mediators:
• NO via nitrous oxide synthase
• CO
• arachidonic acid metabolites (e.g prostaglandins)
• chemokines
• cytokines
• proteases

Question 23

What are the functions of the airway epithelium?

Answer 23

• secretion of mucins, water and electrolytes, components of ‘mucus’
• movement of mucus by cilia- mucociliary clearance
• physical barrier
• production of regulatory and inflammatory mediators:
• NO via nitrous oxide synthase NOS
• CO via haemeoxygenase HO
• arachidonic acid metabolites (e.g prostaglandins) via COX
• chemokines
• cytokines
• proteases

Question 24

What happens to airway smooth muscle during inflammation?

Answer 24

Structure:

• hypertrophy
• proliferation

Tone (airway caliber):

• contraction
• relaxation

Secretion:

• mediators
• cytokines
• chemokines

Question 25

What are the secretory functions of airway smooth muscle during inflammation?

Answer 25

inflammation bacterial products -cytokines stimulate NOS to release NO, COX to release prostaglandins, cytokines, chemokines and adhesion molecules -the released cytokines, chemokines and adhesion molecules stimulate inflammatory cell recruitment

Question 26

Tell me about the trachea-bronchial circulation (systemic).

Answer 26

- 1-5% of cardiac output - blood flow to airway mucosa = 100-150 ml/min/100g tissue - blood returns from tracheal circulation via systemic veins - blood returns from bronchial circulation to both sides of heart via bronchial and pulmonary veins

Question 27

What are the functions of the trachea-bronchial circulation?

Answer 27

- good gas exchange directly between airway tissues and blood - contributes to warming of inspired air - contributes to humidification of inspired air - clears inflammatory mediators - clears inhaled drugs (good/bad, depending on drugs) - supplies airway tissue and lumen with inflammatory cells - supplies airway tissue and lumen with proteinaceous plasm ('plasma exudation')

Question 28

What is the parasympathetic innervation of the airways?

Answer 28

Parasympathetic (cholinergic) 'motor' pathway - ACh neurotransmitter - nodose ganglion - vagus nerve - causes restriction and increased mucous secretion (submucosal glands stimulated)

Question 29

What is the effect of the sympathetic innervation on the airways?

Answer 29

- results in relaxation to increase amount of airflow - adrenaline from adrenal gland also has same effect. -NO release (spinal cord- cervical thoracic ganglion) causes relaxation

Question 30

What is respiratory disease?

Answer 30

- loss of homeostatic control leads to pathophysiology and clinical symptoms of respiratory disease - loss of 'airway' control

Question 31

Examples of respiratory diseases?

Answer 31

- asthma (5% of population) - chronic obstructive pulmonary disease (COPD) - cystic fibrosis (CF)

Question 32

What is the 4th cause of death in the UK and USA?

Answer 32

-COPD

Question 33

What is asthma?

Answer 33

-a clinical syndrome characterised by increased airway 'responsiveness' to a variety of stimuli - airway obstruction - airflow obstruction varies over short periods to time and is reversible (spontaneously or with drugs) - dyspnoea, wheezing and cough - airway inflammation- re-modelling

Question 34

What is the pathology of airway inflammation?

Answer 34

- basement membrane thickening - epithelial fragility - mucus plug in lumen - vasodilation- congested vessels - cellular infiltration

Question 35

What is the pathology of asthma?

Answer 35

- excess mucous- goblet cell hyperplasia - sensory nerve activation, cholinergic reflex- mucus hyper secretion and bronchoconstriction - subepithelial fibrosis Inflammatory mediators increase e.g cytokines and Bfs - mast cells - eosinophils - Th2 lymphocyte - fibroblasts