Trachea, bronchial tree and lungs

Question 1

What is the trachea composed of?

Answer 1

C- shaped hyaline cartilage and trachealis muscle which makes up the posterior aspect of trachea, it alters tracheal diameter

Question 2

Describe the relations of the trachea

Answer 2

It is covered by sternohyoid and sternothyroid muscles. Isthmus of the thyroid gland and the inferior thyroid vessels are at the level of 2 and 3 tracheal cartilage. Lateral to trachea are the carotid sheaths. Inferiorly - brachiocephalic trunk. Anteriorly jugular venous arch. Recurrent laryngeal nerve sits between oesophagus and trachea

Question 3

Describe the travel of the trachea

Answer 3

Starts C6 and enters thoracic cavity via thoracic inlet and then at the sternal angel it divides into left and right principle bronchi

Question 4

Describe the structural differences between the two lungs

Answer 4

Right lung is shorter and wider while right lung is more narrow and has a cardiac notch.

Question 5

Describe the divisions of the main bronchi

Answer 5

Divide into segmental bronchi which will pass into Broncho-pulmonary segments. There are 10 segmental bronchi per lung which continue to divide

Question 6

What do the segmental bronchi divide into and describe their features?

Answer 6

Terminal bronchioles which are connected to respiratory bronchioles. The smooth muscle around bronchioles means they cause the greatest resistance to air flow in the conducting pathways. Each respiratory bronchiole is connected to 2-11 alveolar ducts

Question 7

Describe features of alveolar ducts

Answer 7

Each duct opens into alveolar sacs which are clusters of pulmonary alveoli. Each duct is connected to 5-6 alveoli. They have large surface area for diffusions of gases

Question 8

Describe the structure of the lungs

Answer 8

Three surfaces : Costal, diaphragmatic and mediastinal which make up three margins: anterior, posterior and inferior. ThRee lobes in the Right lung. Two lungs in the left and left has lingula. The lungs are separated by oblique fissures (horizontal fissue in right lung)

Question 9

What are the impressions on the lungs?

Answer 9

Add photo
R - Phrenic nerve on SVC, vagus nerve and liver.
L - Aortic arch, thoracic duct, vagus nerve, subclavian artery, oesophagus, phrenic nerve, stomach and spleen

Question 10

What is the root/hilum of the lung and what is it composed of?

Answer 10

Collection of structures that attach the lung to the structures in mediastinum: Pulmonary artery, two pulmonary veins, main bronchus, bronchial vessels, nerves and lymphatics covered by sleeve of mediastinal pleura which will form the pulmonary ligament.

Question 11

What are the bronchopulmonary segments?

Answer 11

Smallest functionally and structurally independent unit. It is a section of lung with its own branch of pulmonary artery, nerve and segmental bronchus, Tributaries of pulmonary veins and lymphatics pass in inter-segmental septum.

Question 12

Describe features of bronchopulmonary segments

Answer 12

Pyramid shaped with apices facing the hilum. They are separated by connective tissue and have no anastomosis between neighbouring segments so safe surgical excision.

Question 13

Name the different bronchopulmonary segments

Answer 13

R +L Upper lobe: Apical, anterior and posterior segments.

Lingula: Superior and inferior
R middle lobe: Middle and lateral.

Lower lobe: Apical, medial, lateral, anterior and posterior.

Question 14

Describe the histological changes in the bronchial tree

Answer 14

Psudostratified columnar epithelium in the bronchi is replaced by simple cuboidal epithelium in the bronchioles. The wall of each pulmonary alveolus is one once cell layer thick to increase diffusion rate.

Question 15

What are the two types of alveolar and their function?

Answer 15

Type 1 - Permits diffusion,

Type 2 - Produce surfactant that reduces the tendency for pulmonary alveoli to collapse.

Question 16

What area of the lung is most prone to pneumonia and why?

Answer 16

Apical segment on inferior lobe as its tertiary bronchus drops off the bronchial tree posteriorly.

Question 17

Describe the arterial supply of the lungs

Answer 17

Supplied by bronchial arteries:

• One on the right from the 3rd posterior IC artery or the superior posterior IC artery.
• Two on the left from the aorta.

Question 18

Describe the venous drainage of the lungs

Answer 18

It is drained by the bronchial veins into the azygos system or by the pulmonary veins (meaning a small volume of deoxygenated blood enters pulmonary veins).

Question 19

Describe features of the pulmonary arteries

Answer 19

Carry deoxygenated blood to lungs at low pressure. They arise from pulmonary trunk, just below the sternal angel.

Question 20

What is the direction of the right pulmonary artery?

Answer 20

Passes anterior to right primary bronchus and posterior to ascending aorta and SVC.

Question 21

Describe the lymphatic drainage of the lungs

Answer 21

Deep and superficial lymphatic plexus drain to pulmonary lymph nodes which are buried in the hilum. Pulmonary nodes drain to bronchopulmonary nodes, then to inferior and superior tracheobronchial nodes, then to paratracheal nodes and finally to the bronchmediastinal lymph trunks. From there they drain to thoracic ducts then the right lymphatic duct.

Question 22

What is the clinical significance of the lymphatic drainage?

Answer 22

There is connections between the left and right lung meaning cancer can spread very easily

Question 23

Describe the nerve supply of the lungs

Answer 23

Pulmonary plexus composed of parasympathetic fibres from the vagus nerve which synapse in plexus (cause bronchoconstriction, vasodilation and secretomotor). Sympathetic fibres from sympathetic trunk, they synapse in the sympathetic ganglia and cause bronchodilation and vasoconstriction.