Gas exchange

Question 1

Difference between gross anatomy and microscopic anatomy?

Answer 1

Gross anatomy - what we see

Microscopic anatomy - What we see through a microscope — divides into histology , study of tissues and cytology -study of cells.

Question 2

What is parenchyma ?

Answer 2

Functional tissue of an organ e.g liver - hepatocytes, heart - cardiomyocytes.

Question 3

What happens at the T4/5 junction?

Answer 3

The bifurcation of the Trachea and the location of the sternal angle. ‘Arch of the Aorta goes round’?, left recurring laryngeal nerve hooks around the Aortic arch.

Question 4

Difference between right and left bronchus and impact?

Answer 4

Right bronchi is shorter (2.5 cm ) compared to (5cm - left) and is more in line with the trachea while left deviates. Foreign bodies more likely to get lodged in the right.

Question 5

Describe the divisions of the bronchioles?

Answer 5

Bronchi undergo 23 divisions e.g from main bronchus, segmental etc then eventually to bronchioles.

Up to the 16-17th generation of bronchi - there is the same lining as Trachea (psuedostraitfied columar epthelium). From the 17th - 19th there is a transition , cells begin to change and become flatter, smaller and more round. From 20th gen - the completely flatten out and become squameous. (ALVEOLI BEGIN TO EMERGE AT AROUND THE 21ST GENERATION. )

Question 6

Describe the cartilage of the Trachea.

Answer 6

C- shaped cartilage - allows food to pass down the oesophagus. (normally oesophagus is a flat muscular tube but food comes down and forms a ball -‘ballus’(made with tongue) and moves down the oesophagus by peristalsis.)

Question 7

What is the deadspace?

Answer 7

• Anatomical deadspace - Air present, but does not take part in gas exchange - includes Trachea , Bronchi (up to gen 16-17)
• Physiological deadpsace - includes the anatomical deadspace but also (alveolar deadspace - well ventilated but poorly perfused layers of the alveoli not taking part in the gas exchange).

around only 15% of alveoli involved in gas exchange (gas exchange can only occur where cells are squamous and right near a blood vessel.)

Question 8

What do alveolar type 2 cells do?

Answer 8

Secrete fluid - Surfactant - reduces surface tension in alveoli. Surfactant prevents alveolar collaspe. Surfactant is only secreted in the final weeks of pregnancy (pre - mature babies - not producing surfactant yet - we have to create positive pressure for them to breathe. )

Question 9

How do we exchange gases?

Answer 9

Simple passive diffusion - using partial pressures