Structure And Function Of The airways

Question 1

What is the branching pattern of the airways?

Answer 1

Dichotomous branching (each level splits into two

Question 2

What is the structure of the lungs?

Answer 2

Trachea from pharynx to lungs

Left lung (2 lobes)

Right lung (three lobes)

Thea he’s splits into two primary bronchi (one on each side)

Primary bronchi split into secondary bronchi

Secondary split into tertiary

Mechanical stability is provided by c shaped cartilage rings

Question 3

What is the structure of the alveolar region?

Answer 3

Where gas exchange occurs

Terminal (non cartilaginous) bronchioles branch into the respiratory bronchioles

These contain alveolar ducts, and many alciolar sacs comprised of many alveoli

Question 4

What cells make up the alveolar unit?

Answer 4

Type I cells: very thin, delicate Barrier, facilitate gas exchange, make up 95% of surface but fewer type I cells than type II

Type II cells: replicate to replace type I cells, secrete surfactant (reduces surface tension) anti proteases, xenobiotic metabolism (such as noxious chemicals)

Question 5

What is the basic function of the airways?

Answer 5

Getting air efficiently to the gas exchange region. Keeping the Pipework clear

Conduit to: conduct O2 to the alveoli, conduct CO2 out of the lung. For gas exchange

facilitated by: mechanical stability (cartilage), control of Calibre (smooth muscle), protection and cleansing

Question 6

What is the structure and role of the nasal passages? (In relation to the airway)

Answer 6

Pharynx: common passageway for food, liquids and air

Conchae: highly vascular - co tributes to warming and humidification of intra nasally inhaled air

Nasal hairs filter out large particles

Question 7

What is the organisation/structure of the trachea?

Answer 7

(Outside to inside of a transverse section)

Surrounded by cartilaginous rings

Layer of smooth muscle

Blood vessels,nerves and submucosal glands (secrete mucus) (this has part of it in the smooth muscle layer)

Layer of ciliated epithelial cells (lots of mitochondria to beat cilia) and goblet cells (secrete mucus)

Layer of mucus

Question 8

What are the cell types found in the airway?

Answer 8

Lining cells (ciliated, intermediate, brush, basal)

Contractile cells (smooth muscle)

Secretory cells (goblet, mucous, serous (glands))

Connective tissue (fibroblasts, interstitial cells

Neuroendocrine (nerves, ganglia)

Vascular cells (endothelial, pericyte, plasma cell)

Immune cells (mast cell, dendritic cell, lymphocyte, eosinophil, macrophage, neutrophil)

Question 9

What do the goblet cells do?

Answer 9

Contain and secrete mucin granules

These contain a highly condensed form of mucin

When the granules are released they take on water and decondense when opened

Question 10

What is the structure and function of the submucosal glands?

Answer 10

Serous acini -> mucous acini -> collecting duct -> ciliated duct

Mucous cells secrete mucus

Serous cells secrete anti bacterial enzymes

Also secrete water and salts

The serous glands are more distal than the mucous glands, this may be coz their secretions are more watery so help the mucous to move out of the gland and

Question 11

What is the structure of a cilium?

Answer 11

Longitudinal section:

Long axoneme (microtubules)

Apical hooks at the end that engage with mucus

Intracellular anchoring proteins

Transverse section:

Dynein (outer and inner arm)

Microtubules connected by nexin links

There are abiut 200 cilia per ciliated cell

Google the structure

Question 12

What are the functions of the airway epithelium?

Answer 12

Secretions of mucins, water and electrolytes (components of mucus (and plasma etc))

Movement of mucus by cilia -mucociliary clearance

Physical barrier

Production of regulatory and inflammatory mediators:

Nitric oxide (NO via nitric oxide synthase (NOS))

Carbon monoxide (CO via hemeoxygenase (HO))

Arachadonic acid metabolites (eg. Prostaglandins, via COX)

Chemokines (eg IL 8)

Cytokines

Proteases

Question 13

What is the function of the airway smooth muscle?

Answer 13

Inflammation ->

Smooth muscle:

Structure - hypertrophy/proliferation

Tone(calibre) - contraction/relaxation

Secretion - mediators, cytokines, chemokines

Question 14

What are the secretory function of the airway smooth muscle?

Answer 14

Inflammation (presence of bacterial produce and cytokines) stimulates the NOS pathway to produce NO, the COX pathway to produce prostaglandins, the production of cytokines, chemokines and adhesion molecules

Production of the last three leads to inflammatory cell recruitment

Question 15

What is the vasculature of the airway?

Answer 15

Tracheo-bronchial circulation (systemic)

1-5% of cardiac output

Blood follow to the mucosa is some of the highest one of the highest to any sissy’s

Bronchial arteries arise from many sites on the aorta, intercostal arteries and others

Blood returns from tracheal circulation via systemic veins

Blood returns from bronchial circulation to both sides of the heart via bronchial and pulmonary veins

Question 16

What are the functions of tracheo-bronchial circulation?

Answer 16

Good gas exchange (directly between airways and blood)

Contributes to warming and humidification of inspired air

Clears inflammatory mediators

Clears inhaled drugs

Supplies airway tissue and lumen with inflammatory cells

Supplies airway tissue and lumen with proteinaceous plasma

Question 17

What is the innervation of the airways?

Answer 17

Parasympathetic (cholinergic) “motor” pathway - contraction/constriction, mucous secretion

Nitric oxide - relaxation

Adrenaline -relaxation

Question 18

What are some airway diseases with loss of airway control?

Answer 18

Asthma, COPD, CF

All are common

Airway inflammation, airway obstruction

Airway remodelling (COPD)