Respiratory - Histology

Question 1

What are the four main layers of the respiratory system?

Answer 1

Mucosa
Submucosa
Cartilage/muscle layer
Adventitia

Question 2

What is the trachea?

Answer 2

A wide flexible tube

Question 3

What keeps the lumen of the trachea patent?

Answer 3

20 C-shaped tracheal cartilages, which are hyaline in nature

Question 4

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

Answer 4

Trachealis muscle and fibroelastic tissue

Question 5

What is the role of the respiratory mucosa and submucosa?

Answer 5

Warm and moisten the air, and to trap foreign particles in mucous.

Question 6

What is the mucosa of the trachea made up of?

Answer 6

Epithelium: Ciliated pseudostratified columnar epithelium with goblet cells.

Question 7

What is the role of the trachea’s adventitia?

Answer 7

Connects and supports trachea to surrounding tissue, eg. thyroid and oesophagus.

Question 8

What does the trachea’s adventitia contain?

Answer 8

Nerves, vessels and adipose tissue.

Question 9

What does the trachea branch into?

Answer 9

The trachea branches into two primary bronchi, which again branches into secondary and then tertiary bronchi.

Question 10

What are the features of the intrapulmonary bronchi?

Answer 10

In the intrapulmonary bronchi, there is less cartilage, and it does not completely encircle the lumen.

Question 11

What does the extrapulmonary bronchi resemble?

Answer 11

The extrapulmonary bronchi (e.g. primary bronchi) closely resemble the trachea histologically.

Question 12

What layers make up the bronchi?

Answer 12

Contains layers of smooth muscle between the mucosa and submucosa

Question 13

What is the diameter of the bronchioles?

Answer 13

1mm or less

Question 14

What type of muscle increases in the bronchioles?

Answer 14

Smooth muscle

Question 15

What cells are present in bronchioles and what do they do?

Answer 15

Clara cells are present: secretes surfactant

Question 16

What do bronchioles lack?

Answer 16

No goblet cells (a few goblet cell may be found in the initial part)
Non-ciliated cells
No submucosal Glands
No Cartilage

Question 17

What is the terminal bronchiole lined by?

Answer 17

Ciliated cuboidal epithelium with clara cells and give rise to respiratory bronchiole

Question 18

What is the respiratory bronchiole lined by?

Answer 18

Low cuboidal epithelium.

Question 19

What are alveolar ducts surrounded by?

Answer 19

Smooth muscle, elastin and collagen

Question 20

What are alveolar sacs surrounded by?

Answer 20

Blood vessels/ pulmonary capillaries

Question 21

What are alveoli surrounded by?

Answer 21

Blood vessels/ pulmonary capillaries.

Gaseous exchange between blood and air occurs.

Question 22

What are the two cell types in the epithelium of the alveoli?

Answer 22

Type I and Type II pneumocytes

Question 23

Describe Type I pneumocytes

Answer 23

Large flattened cells - (95% of the total alveolar area) which present a very thin diffusion barrier for gases.

Question 24

Describe Type II pneumocytes

Answer 24

(making up 5% of the total alveolar area, but 60% of total cells).

These cells secrete ‘surfactant’ which decreases alveolar surface tension and stops alveoli collapsing when we breathe out.

Question 25

Where does gas exchange take place?

Answer 25

Through the endothelial cell of the capillary, basement membrane and type I pneumocyte.

Question 26

What is the conducting portion characterised by?

Answer 26

Pseudostratified columnar epithelium with cilia

Goblet cells

Gland tissue

Hyaline cartilage.

Question 27

What is the respiratory portion characterised by?

Answer 27

Epithelium gradual transition from cuboidal to simple squamous.

Cartilage ends

Abundant smooth muscle, elastic fibers, reticular fibers