B2 W1 Respiratory Tract Histology & Gas Exchange

Question 1

What are the two functional divisions of the respiratory system?

Answer 1

The conducting zone and the respiratory zone.

Question 2

What is the main role of the conducting zone?

Answer 2

To warm, humidify, and filter air.

Question 3

What type of epithelium lines the nasal cavity?

Answer 3

Pseudostratified columnar epithelium.

Question 4

Why is the epithelium in the nasal cavity called “pseudostratified”?

Answer 4

Although it is a single layer of cells, the nuclei are at different levels, giving the illusion of multiple layers.

Question 5

What is the function of cilia in the nasal cavity?

Answer 5

To sweep particulates away from the lungs.

Question 6

What do goblet cells produce?

Answer 6

Mucus, which helps filter and humidify inhaled air.

Question 7

What is the function of the larynx?

Answer 7

It is a passageway for air and is involved in sound production (phonation).

Question 8

Which pair of vocal folds is responsible for producing sounds in speech?

Answer 8

The vocal (true) folds.

Question 9

What type of muscle is the vocalis muscle?

Answer 9

Skeletal muscle.

Question 10

What is the key characteristic of the trachea that helps maintain an open airway?

Answer 10

C-shaped rings of hyaline cartilage.

Question 11

Why are the cartilage rings in the trachea C-shaped and not complete circles?

Answer 11

To allow the oesophagus to expand during swallowing.

Question 12

What is the collective term for the branching system of airways?

Answer 12

The bronchial tree.

Question 13

As you move deeper into the bronchial tree, what happens to the amount of hyaline cartilage?

Answer 13

It decreases.

Question 14

What happens to the amount of smooth muscle as you move deeper into the bronchial tree?

Answer 14

It increases.

Question 15

What are the structural differences between bronchi and bronchioles?

Answer 15

Bronchi have cartilage and a pseudostratified columnar epitheliumBronchioles lack cartilage and have a simpler epithelium.

Question 16

What is the function of Type I pneumocytes in the alveoli?

Answer 16

They form the thin walls of the alveoli and facilitate gas exchange.

Question 17

What do Type II pneumocytes secrete, and what is its function?

Answer 17

They secrete surfactant, which reduces surface tension and prevents the alveoli from collapsing.

Question 18

What is the role of macrophages in the alveoli?

Answer 18

They remove foreign material like dust and bacteria.

Question 19

What is the process by which gases move between the alveoli and capillaries?

Answer 19

Diffusion.

Question 20

What is partial pressure?

Answer 20

The pressure exerted by a single gas within a mixture of gases.

Question 21

What are the components of the alveolar-capillary membrane? (3)

Answer 21

Alveolar epithelial cellsA fused basement membranePulmonary capillary endothelial cells.

Question 22

What is the function of the trachealis muscle?

Answer 22

It connects the C-shaped rings of cartilage in the trachea, helps stabilise them, and aids in forceful expiration.

Question 23

How does the solubility of carbon dioxide compare to oxygen, and what is the effect of this on their diffusion rates?

Answer 23

Carbon dioxide is about 20 times more soluble in tissue than oxygen. This higher solubility allows carbon dioxide to diffuse about 20 times faster than oxygen, even though it has a slightly larger molecular weight.

Question 24

How does the composition of alveolar gas differ from atmospheric air?

Answer 24

Alveolar gas has a lower partial pressure of oxygen and a higher partial pressure of carbon dioxide compared to atmospheric air. This difference is due to the continuous exchange of gases between the alveoli and the blood.

Question 25

How does surfactant regulate surface tension within the alveoli, particularly during rapid inflation?

Answer 25

Surfactant, a liquid secreted by Type II pneumocytes, lines the alveoli and reduces surface tension. During rapid inflation, the surface density of surfactant decreases, causing an increase in surface tension and elastic recoil. This increased surface tension acts as a “brake” to prevent overexpansion of the alveoli.

Question 26

How can diseases affect gas exchange in the lungs?

Answer 26

Some diseases can affect the surface area, thickness, or properties of the alveolar-capillary membrane. These changes can decrease the lungs’ diffusing capacity, leading to impaired gas exchange.

Question 27

What is the function of the smooth muscle in the bronchi?

Answer 27

The smooth muscle in the bronchi helps to regulate the diameter of the airways. This is especially important in the tertiary bronchi, where the smooth muscle helps to stabilise the cartilage and control the size of the bronchial lumen.

Question 28

What are the histological differences between the primary and tertiary bronchi in terms of their epithelium?

Answer 28

The primary bronchi are lined with ciliated pseudostratified columnar epithelium with many goblet cells. In the tertiary bronchi, the epithelium transitions to ciliated columnar epithelium with fewer goblet cells. This reduction in goblet cells reflects the difficulty of clearing mucus from smaller airways.