Respiratory 2: more structure

Question 1

What are main trends in the diameter, epithelia as you continue branching into 2 from bronchus/trachea to bronchioles further

Answer 1

The diameter reduces. The complexity of the cells decrease (less conditioning needed)
The epithelia height reduces in the form of going from pseudostratified columnar to cuboidal to squamous because we need to have thin cell layer for gas diffusion to be good.

Question 2

What are the layers within the bronchus wall from air to before the alveoli

Answer 2

1. Pseudostratified cillated columnar epithelium + goblet cells
2. Smooth muscle layer
3. Mucous glands
4. Cartilage plates

Question 3

What are the two sources of mucus in the trachea and bronchus

Answer 3

Goblet cells and mucous glands

Question 4

What are the layers within the bronchioles wall from air to before the alveoli

Answer 4

1. Simple cilliated columnar/cuboidal epithelium + club cells
2. Smooth muscle

Question 5

Are the alveoli part of the bronchus/bronchiole wall?

Answer 5

No

Question 6

What are the main differences between the structure of bronchus walls vs bronchiole walls

Answer 6

1. Bronchus still air conditioning whereas Bronchioles not really so Bronchus has 2 places for mucous but Bronchioles have club cells that secrete a watery secretion that helps with hydration and antimicrobial enzymes
2. In bronchus smooth muscle layer doesn’t rlly keep it open bc it has cartilage to do that, but in Bronchioles It doesn’t have Cartilage so smooth muscle layer is important for bronchodilation/constriction and controlling air to respiratory zone

Question 7

What is the mechanism of acute asthma attack and how is it treated

Answer 7

Triggered by heat, pollen, dust etc there is rapid bronchoconstriction which reduces airflow to respiratory zone. Treated with bronchodilators which relax smooth muscle (salbutamol)

Question 8

Describe the 3 structures of the respiratory zone

Answer 8

1. The respiratory bronchioles that have same wall structure as other bronchioles but have small buds of alveoli where gas exchange can take place
2. Alveolar ducts: tubes formed by alveoli
3. Alveolar sacs: bunch of alveoli that extend from one branch

Question 9

Describe the cells in the alveolar wall

Answer 9

Type 1. Squamous pneumocyte, thin bordering with capillaries for gas exchange
Type 2: Surfactant cells: secrete surfactant liquid which keeps the alveolar open
Type 3: Alveolar Macrophage: wandering cell, last line of defense against microbes

Question 10

What is the importance of surfactant in alveolus and how does it relate to Work of breathing

Answer 10

Surfactant prevents the collapse of the alveolus on expiration by decreasing surface tension. Made of phospholipid that repels each other. This reduces the work of breathing

Question 11

What is work of breathing

Answer 11

the energy required to get air in (inspire) and inflate the structures

Question 12

Identify what constitutes a diffusion barrier - also called Blood air barrier (0.5 um)

Answer 12

It has squamous pneumocyte facing the air space. The basement membrane of Sq. pnu. is fused with the basement membrane of capillary endothelium to make it uniquely
Then there is the capillary endothelium that opens to blood plasma

Question 13

What type of respiration takes place at the diffusion barrier and what type of disease can affect it

Answer 13

External respiration. Fibrosis increases the connective tissue in the basement membrane layer which increases distance for diffusion and therefore can lead to hypoxic blood.

Question 14

What are the main subdivisions of the lung and what bronchi supply them

Answer 14

1. There is a right lung and left lung supplied by 1’ bronchi
2. There are 2 left lobes and 3 right lobes supplied by 2’ bronchi
3. There are 8 left segments on the left and 10 segments on the right. Each supplied with its own 3’ bronchi and blood supply.

Question 15

What covers the blood vessels, lymphatic fluid and air supply to the segments of the lung

Answer 15

connective tissue

Question 16

What is the clinical significance of lung segments

Answer 16

Surgeons can remove localised tumours in the lung within 1 or 2 segments without excessive leakage of blood or air from other segments

Question 17

What is the structure of the pleurae

Answer 17

The visceral pleura covers each lung and the parietal pleura covers the thoracic cavity. The place where the ends join is at the hilum. This is filled with a pleural space with a thin layer of pleura fluid.

Question 18

What is the function of the pleurae

Answer 18

The pleural fluid allows the pleurae to slide past each other without friction. It also prevents the two layers from being separated, allowing the movements of the thoracic wall and diaphragm to affect the volume in the lungs.

Question 19

What is the mechanics of the muscles that help inspiration

Answer 19

In inspiration the external intercostal muscles contract and the diaphragm contracts.
External intercostal muscles causes inspiration because as they contract the ribs pivot around their joints in the verterbral column and lift the rib cage up and out.
When Diaphragm contracts, it flattens the central tendon which pulls the dome downwards and increases the volume of the thorax

Question 20

What are the mechanics of the muscles that help expiration

Answer 20

Expiration is a passive process at rest where diaphragm passively relax and rib cage returns to resting position. In active processes the internal intercostal muscles (at right angles to external intercostal muscles) contract and drag the rib in and down.

Question 21

What is the ratio of intercostal muscles to diaphragm with rest breathing vs exercise breathing

Answer 21

At rest, movement of the ribcage is 25% and diaphragm is 75%, however in exercise the ribcage contributes more to exercise

Question 22

Describe the structure of the diaphragm: shape and components

Answer 22

Dome shaped platform that has a central part of thin connective tissue (aponeurosis) callled central tendon and lateral margins of skeletal muscle attaching to the sternum and vertebrae.