Thorax 2: The Mediastinum

Question 1

Describe the pericardium

Answer 1

Fibrous and serous layers

Enables movement of the heart to expand and contract

Question 2

Describe the fibrous pericardium

Answer 2

It is a closed sac with a fixed volume which surrounds the heart and great vessels. It defines the middle mediastinum

Question 3

Where does the pericardium attach

Answer 3

Superiorly to the great vessels and inferiorly to the diaphragm at the central tendon

Question 4

What does the diaphragmatic attachment of the pericardium do?

Answer 4

prevents descent of diaphragm and eversion of the ribs

Question 5

What innervates the fibrous pericardium

Answer 5

Phrenic Nerve

Question 6

What is interesting about the serous pericardium?

Answer 6

Its complex reflections give rise to 2 sinuses - transverse and oblique

Question 7

How are sinuses formed

Answer 7

The heart tube folds and invaginates into the serous pericardium during embryological development

Question 8

What forms the transverse sinus?

Answer 8

arterial and venous ends of the developing heart tube are brought together

Question 9

Where is the transverse sinus located

Answer 9

behind the aorta and pulmonary trunk and in front of the SVC and left atrium auricle

Question 10

Clinical implication of the transverse sinus

Answer 10

Cardiac surgery

Question 11

What forms the oblique sinus

Answer 11

As the pericardium reflects around the Expansion of the veins it results in a potential space behind the left atrium

Question 12

Requirements of pulmonary circulation

Answer 12

Deoxygenated blood to the lungs at 12-16 mmHg

Question 13

Requirements of systemic circulation

Answer 13

Oxygenated blood at 70-120 mmHg

Question 14

What are the surfaces of the heart

Answer 14

Anterior Sternocostal, Inferior Diaphramatic and Posterior Base

Question 15

What is represented on the anterior surface

Answer 15

R atrium and ventricle

Question 16

What is represented on the inferior surface

Answer 16

Left and right ventricles

Question 17

what is represented on the posterior surface

Answer 17

Left auricle and coronary sinus

Question 18

Describe the borders of the heart

Answer 18

Right atrium/left ventricle and auricle/apex of left ventricle

Question 19

What structures are at the side of heart

Answer 19

pleura, lungs and phrenic nerves

Question 20

What structures are behind the heart

Answer 20

Oesophagus and descending aorta

Question 21

What structures are related to the right mediastinum

Answer 21

Superior Vena Cava
Arch of Azygous
R Atrium
Inferior Vena Cava

Question 22

What structures are related are related to the left mediastinum

Answer 22

Left common carotid
left subclavian
arch of aorta
thoracic aorta
left ventricle

Question 23

Where do phrenic nerves enter the mediastinum

Answer 23

Superior mediastinum between the venous and arterial planes, posterior to the brachiocephalic vein

Question 24

Describe the course of the right phrenic nerve after entering the superior mediastinum

Answer 24

1. Passes right of SVC to the right atrium of the heart anterior to the lung root.
2. Passes right of the IVC and through the diaphragm at the level of T8

Question 25

Describe the course of the left phrenic nerve after the entering the superior mediastinum

Answer 25

1. Passes between the left common carotid and left subclavian artery.
   passes anterior to arch of aorta and lateral to the vagus nerve.
   passes anterior to left lung root on the pericardium lying over the left ventricle

Question 26

what is the motor supply of the phrenic nerve

Answer 26

diaphragm

Question 27

what is the sensory supply of the phrenic nerve

Answer 27

1. Central tendon of diaphragm, its parietal pleura and underlying peritoneum
2. Mediastinal parietal pleura
3. Pericardium

Question 28

Why does phrenic nerve pain refer to the shoulder

Answer 28

Supraclavicular nerves arise from C3/4

Lateral supraclavicular nerve supplies skin covering the shoulder in the dermatome C4