Mediastinum - Superior, Anterior, Posterior

Question 1

What is the mediastinum ?

Answer 1

A space between the lungs, extending from the sternum to the vertebral column and from the thoracic inlet to the diaphragm
Divided by the upper and lower boundaries, the pulmonary spaces and trans thoracic plane
Contains major thoracic organs providing space for their movement and breathing

Question 2

Describe the anterior mediastinum:

Answer 2

Smallest of all the compartments
Located posterior to the sternum, anterior to the pericardium and heart
Organs - thymus
Vessels - internal thoracic vessels
No nerves
Contains lymphatics and lymph nodes

Question 3

Describe the superior mediastinum:

Answer 3

Superior to the trans thoracic plane
Posterior to the manubrium, anterior to T1-T4 vertebrae

Contains;
Organs - thymus, trachea, oesophagus
Vessels - arch of aorta, superior vena cava, L & R brachiocephalic veins
Nerves - Phrenic (supplies diaphragm), Vagus, L & R recurrent laryngeal
Other - left thoracic duct, right lymphatic duct, lymph nodes

Question 4

Describe the arterial great vessels

Answer 4

Arch of aorta;
Brachiocephalic trunk - formed by right common carotid and right subclavian arteries
Left subclavian
Left carotid

Ascending aorta - arises from the left ventricle and becoming coronary arteries
Descending Thoracic Aorta - supplies the thoracic organs and intercostal muscles
Pulmonary trunk - arises from the right ventricle and divides into right and left pulmonary arteries

Question 5

Describe the venous great vessels:

Answer 5

Left and right brachiocephalic veins - formed by joining of Internal jugular vein and Subclavian vein
Superior vena cava - unification of left and right brachiocephalic veins
Inferior vena cava - formed by joining of left and right common iliac veins

Question 6

Describe the phrenic nerve:

Answer 6

Passes anterior to the root of lung
Motor innervation to the diaphragm
Sensory innervation to the pericardium, mediastinal pleura and diaphragmatic pleura
Mixed nerve as anterior rami

Question 7

Describe the vagus nerve:

Answer 7

Passes posterior to the root of the lung
Provides parasympathetic innervation to thoracic organs including heart and lungs

Question 8

Describe the recurrent laryngeal nerve:

Answer 8

Branches of the vagus nerve
Right side loops under right subclavian artery
Left side loops under aortic arch
Motor innervation to intrinsic muscles of the larynx (voice production)
Travels upward alongside the trachea and oesophagus

Question 9

Describe the oesophagus and trachea

Answer 9

Oesophagus is a fibromuscular tube
Extends from pharynx (ends T6) to stomach
Located anteriorly to the vertebral bodies
Posterior to the trachea
Pierces diaphragm at level at T10
Oesophageal plexus - left and right vagus nerve, aids parasympathetic innervation

Question 10

Describe the thoracic duct:

Answer 10

Part of lymphatic system
Drains lymph from majority of body
Enters into left venous angle (where left subclavian meets left jugular)
In between thoracic aorta and oesophagus

Question 11

Describe functions of the lymphatic system:

Answer 11

Fat absorption
Immune - Lymph nodes around the body monitor for foreign pathogens
Reabsorption of fluid - interstitial fluid that has leaked to the interstitial space is taken up to prevent oedema

Question 12

Describe the posterior mediastinum:

Answer 12

Inferior to the transthoracic plane
Anterior to T5-T12 vertebrae and posterior to the pericardium
Medial to parietal pleura
Superior to the diaphragm

Contains;
Organs - oesophagus
Vessels - thoracic aorta, azygous vein, hemi azygous vein, accessory hemi azygous vein
Nerves - vagus nerve, sympathetic trunk, Splanchnic nerves
Thoracic duct

Question 13

Describe the location and path of the thoracic duct

Answer 13

Drains structures inferior to the diaphragm
Passes through the diaphragm with the aorta T12
Lies anterior to vertebral bodies
Found between azygous vein and oesophagus
Runs to the left at the trans thoracic plane
Drains to left venous angle