Respiratory Histology

Question 1

What are the innervations of the lung?

Answer 1

Parasympathetic - bronchoconstriction, mucus secretion, vasodilation.
Sympathetic - bronchodilation.

Question 2

What are the four main layers of the respiratory system?

Answer 2

Mucosa.
Submucosa.
Cartilage and/or muscle layer.
Adventitia.

Question 3

What fills the gaps between rings of cartilage in the trachea?

Answer 3

Trachealis muscle.
Fibroelastic tissue.

Question 4

How are the respiratory mucosa and submucosa adapted in the trachea?

Answer 4

Moistens the air.
Traps foreign particles in mucus.

Question 5

What cells make up the mucosa of the trachea?

Answer 5

Ciliated pseudostratified columnar epithelium, with goblet cells.
Lamina propria is underneath the epithelium, and contains elastin and blood vessels.

Question 6

What is the function of basal cells in the trachea?

Answer 6

Regenerates the columnar epithelium if they are damaged, or renewal is needed.
Acts as stem cells.

Question 7

What cells make up the submucosa of the trachea?

Answer 7

Mixed sero-mucous glands.
Watery secretions humidify inspired air.
Mucus traps particles in the air and transport them to the pharynx via cilia.

Question 8

What is the adventitia of the trachea?

Answer 8

Connects and supports the trachea to the thyroid and oesophagus.
Contains nerves, vessels, and adipose tissue.

Question 9

What is the histology of the extrapulmonary and intrapulmonary bronchi?

Answer 9

Closely resembles the trachea.

Question 10

What cells make up the bronchioles?

Answer 10

Ciliated pseudostratified columnar.
This decreases in height in the bronchiole, to become simple columnar, then simple cuboidal.

Clara cells are present (non-ciliated).
These secrete surfactant.

Question 11

What are the differences between the bronchi and bronchioles?

Answer 11

Bronchioles have -
Less or no cilia.
Less or no goblet cells.
Thicker smooth muscle.
No submucosal glands in the lamina propria.
No cartilage.

Question 12

What lines the -
Terminal bronchiole?
Respiratory bronchiole?

Answer 12

Ciliated cuboidal epithelium.
Clara cells.

Question 13

What surrounds the -
Alveolar ducts?
Alveolar sacs and alveoli?

Answer 13

Smooth muscle, elastin, and collagen.

Question 14

What are ‘dust cells’?

Answer 14

Macrophages in the lumen of alveoli.
Has a brownish appearance.

Question 15

Describe the histology of gas exchange.

Answer 15

Takes place through the capillary endothelium, the basement membrane, and Type I pneumocytes.
The wall of the capillary endothelium is fused to the alveoli.

Question 16

What is the trachealis muscle?

Answer 16

In the posterior wall of the trachea.
Allows for tracheal constriction and dilation.

Question 17

What does the trachea branch into?

Answer 17

Two extrapulmonary main bronchi, which branch into secondary (lobar) and tertiary (segmental) intrapulmonary bronchi.

Question 18

Describe the arrangement of cartilage in an intrapulmonary bronchus.

Answer 18

Discontinuous arrangement.

Question 19

What happens in an asthma attack?

Answer 19

Airways can almost completely shut if the smooth muscle contracts strongly.
Bronchiole diameter is reliant on smooth muscle tone.

Question 20

What type of tissue is the lamina propria?

Answer 20

Loose CT.