Session 2 - The lungs and the mediastina

Question 1

Describe the surface structure of the lungs

Answer 1

○ An apex 
	○ Three surfaces: a costal surface, a diaphragmatic surface and a mediastinal surface
	○ Three borders 
		§ Anterior, inferior, posterior 
	○ A base
	○ Lobes
		§ Two (left lung) or three (right lung) 
		§ Created by one or two fissures

Question 2

What is the oblique fissure in the right lung?

Answer 2

• Separates the right upper and middle lobes from the lower lobe of the right lung

Question 3

What is the oblique fissure in the left lung?

Answer 3

Separates the upper and lower lobes

Question 4

What is the horizontal fissure in the right lung?

Answer 4

• Separates the right upper and middle lobes

Question 5

What extends into the fissures of the lungs?

Answer 5

The visceral pleura

Question 6

What do the lungs receive nervous supply from?

Answer 6

• The vagi and sympathetic trunk via the pulmonary plexuses, situated in the hilum

Question 7

What enters the lung through the hilum

Answer 7

• Pulmonary arteries and veins
• Bronchial arteries and veins
• Nerves
• Lymphatics

Question 8

What is the hilum of the lung?

Answer 8

A wedge shaped area on the mediastinal surface of each lung through which structures forming the roots of the lung pass to enter or exit

Question 9

What do the roots of the lung consist of?

Answer 9

• Bronchi
• Pulmonary arteries
• Superior and inferior pulmonary veins
• Pulmonary plexus of nerves
• Lymphatics

Question 10

What is the mediastinum?

Answer 10

• The central compartment of the thoracic cavity

Question 11

What is the mediastinum covered by?

Answer 11

• Mediastinal plueura

Question 12

Where does the mediastinum extend to and from?

Answer 12

• Superior thoracic arpeture to the diaphragm

* Sternum and costal cartilages anteriorly to the bodies of the thoracic vertebrae posteriorly

Question 13

What two sections is the mediastinum divided into?

Answer 13

• Superior and inferior parts

Question 14

Where does the superior mediastinum extend to and from?

Answer 14

• Superior thoracic aperture to the transverse thoracic plane

Question 15

What is the transverse thoracic plane?

Answer 15

• Horizontal plane that includes the sternal angle anteriorly and passes approximately through the junction of T4 and T5 posteriorly

Question 16

Where does the inferior mediastinum extend to and from?

Answer 16

• Transverse thoracic plane to the diaphragm
• Further subdivided by the pericardium
○ Anterior
○ Middle

Posterior

Question 17

Give one structure which lies in more than one compartment of the mediastinum

Answer 17

Oesophagus

Question 18

Where do the pulmonary arteries carry mixed venous blood?

Answer 18

• From the right ventricle for gas exchange at the alveoli

Question 19

What does the main pulmonary artery divide into?

Answer 19

The right and left pulmonary arteries

Question 20

What structure do the pulmonary arteries divide with?

Answer 20

The bronchial tree

Question 21

What do the pulmonary arteries supply?

Answer 21

• The alveoli only

Question 22

Are there any anastamoses between bronchial and pulmonary arteries?

Answer 22

Yes, at pre capillary and capillary level

Question 23

How does the path of the pulmonary veins differ from that of the pulmonary arteries?

Answer 23

• Do not follow divisions of bronchi

* Tend to run into intersegmental septa

Question 24

How many pulmonary veins leave each hilum?

Answer 24

• Two

Question 25

What is the name of the two lymphatic plexi that drain the lungs?

Answer 25

• Subpleural lymphatic plexus Deep bronchopulmonary lymphatic plexus

Question 26

What is the diaphragm?

Answer 26

A dome shaped muscle which divides the thoracic cavity from the abdominal cavity.

Question 27

Why is the large size of the diaphragm clinically important, as pertaining to the position of other organs?

Answer 27

* Means kidneys, liver, spleen, parts of the stomach and upper kidneys lie in the abdominal cavity and are covered by the ribs * Lower chest injuries significant

Question 28

Outline the structure of the diaphragm

Answer 28

• A peripheral muscular part and a central tendon

Question 29

What is the peripheral muscular part of the diaphragm made up of?

Answer 29

* The crura tendons which arise from L1-L3 | * Arcuate ligaments, which are thickening of the fascia

Question 30

What are the three parts of the diaphragm?

Answer 30

* Vertebral arising from the crura and acruate ligaments * Costal part arising from inner aspects of 7-12 costal cartilage Sternal part arising from deep surface of xiphissternum

Question 31

What happens if you have cervical spinal damage from C2 downwards

Answer 31

• Severs link to phrenic nerve (C3, C4, C5), so lose function of the diaphgragm

Question 32

What is the phrenic nerve sensory for?

Answer 32

* Both surfaces of diaphragm * Medialstinal part of the pleura * Diaphragmatic part of the parietal pleura

Question 33

What are the three parts of the thoracic cavity?

Answer 33

• Two lateral pulmonary cavities and one central compartment - the mediastinum

Question 34

What compartments is the mediastinum divided up into?

Answer 34

* Superior * Middle * Posterior Inferior

Question 35

What is the purpose of the parietal pleura?

Answer 35

• Secretes fluid, which sticks it to the visceral pleura This means everything moves at once

Question 36

What proportion of chest expansion is done by the diaphragm?

Answer 36

70%

Question 37

What proportion of chest expansion is governed by the chest wall?

Answer 37

30%

Question 38

What does inspiration involve?

Answer 38

• Elevation of external intercostal muscles

Question 39

What does inspiration result in?

Answer 39

* Increase in transverse diameter of thoracic cavity * In the A=P diameter of thoracic cavity * Increase in vertical dimension

Question 40

What occurs in expiration?

Answer 40

• In quiet respiration it simply relaxes elastic of chest wall and lungs In forced expiration, internal and innermost intercostal muscle and abdominal muscle are used

Question 41

What muscles are used in quiet inhalation?

Answer 41

* Diaphragm | * External intercostals

Question 42

What muscles does forced inhalation involve? (6)

Answer 42

``` • Diaphragm • External Intercostals • Scalene • Pectoralis Minor • Sternocleidomastoid Serratus Anterior ```

Question 43

What muscles does forced exhalation involve?

Answer 43

* Internal intercostals * Innermost intercostals * Abdominal muscles