Anatomy of the Respiratory System

Question 1

Describe the location of the trachea?

Answer 1

It extends from its attachment to the cricod cartilage (C6) to the carina (T5-T6)

It is ~ 18mm in diameter and 11cm in length.

Question 2

Describe the anatomy of the bronchial tree

Answer 2

Trachea bifurcates to form the left and right main bronchus.

Each main bronchus is divided into 10 functionally separate bronchopulmonary segments each with its own bronchus, blood supply and lung parenchyma.

Each bronchus further subdivides eventually forming bronchioles. Each bronchiole, with its further subdivision, is called a primary lung lobule. Each division is called a generation there are 23 generations in total.

Broadly the bronchial tree can be categorised into the conducting zone generations 1-16 and the respiratory zone generations 17-23.

Question 3

For the following describe the: generation, type of epithelial cell and any important features:
Main Bronchi

Answer 3

Generations 1-4
Columnar ciliated epithelium (same as trachea)
Contain cartilage rings
RMB 25 degree angle LMB 45 degree angle

Question 4

For the following describe the: generation, type of epithelial cell and any important features:
Small Bronchi

Answer 4

Generations 5-11
Transition to cuboidal epithelium

Question 5

For the following describe the: generation, type of epithelial cell and any important features:
Conducting bronchioles.

Answer 5

Generations 12-16​

Diameters <1mm​

No cartilage​

Smooth muscle​

No Goblet cells​

Transition to cuboidal epithelium

Question 6

For the following describe the: generation, type of epithelial cell and any important features: respiratory zone

Answer 6

Respiratory bronchioles (17-19)​
Epithelial layer thinning​
Muscle layer still present forming sphincters​
Intermittent alveolar outpockets

Alveolar sacs and ducts (20-23)

Question 7

What are the different types of aveolar cells and what are there functions.

Answer 7

Type 1: gas exchange
Type 2: produce surfactant
Type 3: alveolar macrophages

Question 8

How many alveoli are there, what are there combined surface area, what is there diameter?

Answer 8

~300million
50-100m2
0.3mm

Question 9

What makes up the blood gas barrier

Answer 9

Type 1 alveolar cells
Interstital space
Pulmonary capillary epithelium

Question 10

During anaesthesia in which bronchopulmonary segment are you most likely to aspirate

Answer 10

Apical bronchus of the right lower lobe (as it is the first segmental bronchus to arise posteriorly on the right hand side)

Question 11

What is the nn supply of the diaphragm and what is its spinal root

Answer 11

Phrenic nerve which arises at C3,C4 and C5

Question 12

In phrenic nerve palsy what would happen to the diaphragm.

Answer 12

The effected side would paradoxically rise with inspiration.