Sem 1 - G - Superior&Posterior (of Inferior) Mediastinum - Boundaries&contents, Sympathetic chain/Splanchnic nerves, diaphragm

Question 1

Thoracic cavity has right and left hemithoracies with the mediastinum in the centre which is divided into superior and inferior by the transverse thoracic plane (T4/5 vertebral level) Inferior can be divided into anterior, middle and posterior What are the borders of the anterior and middle thoracic cavity?

Answer 1

Anterior mediastinum boundaries * Body of sternum anteriorly * Fibrous pericardium posteriorly * Transverse thoracic plane superiorly * Diaphragm inferiorly Middle mediastinum boundaries * Within the fibrous pericardium

Question 2

What is the border of the superior mediastinum?

Answer 2

Superior mediastinum Thoracic inlet superiorly Transverse thoracic plane inferiory Manubrium of sternum anteriorly T1-4 vertebral bodies posteriorly Parietal pleura of lungs laterally

Question 3

What is the border of the posterior aspect of the inferior mediastinum?

Answer 3

Fibrous pericardium anteriorly T5-12 vertebral bodies posteriorly Transverse thoracic plane superiorly Diaphragm inferiorly Parietal pleura of the lungs

Question 4

What are the contents of the superior mediastinum from anterior to poster?

Answer 4

Thymus Brachiocephalic veins and the superior vena cava Arch of the aorta and its branches Trachea Oesophagus Vagus and phrenic nerves Lymphatics

Question 5

Where do veins draining the head, neck and upper limb empty? What vein does arch of the aorta lie posterior to? What are its branches?

Answer 5

Veins draining the head neck & upper limb empty into the right and left brachiocephalic veins which join to form the SVC - enters into right atrium Arch of the aorta lies posterior to the left brachiocephalic vein Branches of the arch - brachiocephalic trunk, left common carotid and left subclavian artery

Question 6

The brachiocephalic veins are joined by the union of the subclavian and internal jugular veins What other vein drains into the left brachiocepahlic vein?

Answer 6

The inferior thyroid vein

Question 7

Where does the vagus nerve (R+L) run before giving off the recurrent laryngeal branches?

Answer 7

Right vagus runs anterior to the RSA ,gives off right recurrent laryngeal nerve which loops under RSA Left vagus runs in between the left common carotid and subclavian arteries - gives off the left recurrent laryngeal nerve which hooks under the arch of the aorta & runs posterior to ligamentum arteriosum

Question 8

What does the vagus nerve give branches to before it forms the anterior and posterior oesophageal plexuses?

Answer 8

The vagus nerve gives branches to the cardiac plexus deep to the arch of the aorta - gives parasympathetics to supply the SA node Also gives branches to the right and left pulmonary plexuses on the right and left main bronchi And then the oesophageal plexuses are formed

Question 9

Once the oesophageal plexuses are formed, how do the vagal nerves continue?

Answer 9

They continue as the anterior vagal trunk on the anterior surface of the oesophagus and the posterior vagal trunk on the posterior surface

Question 10

What level does the vagus nerve pass through the diaphragm? Does the anterior or posterior vagal trunks consist of mainly fibres from the right or left vagus nerves?

Answer 10

The anterior and posterior vagal trunks pass through the diaphragm at the oesophageal hiatus at the level of the T10 vertebrae Anterior vagal trunk - mainly fibres from left vagus nerve Posterior vagal trunk - mainly fibres from right vagus nerve (LARP

Question 11

The phrenic nerve is formed by the anterior rami of C 3,4,5 spinal nerves Describe the course of the right phrenic nerve on its way to the diaphragm?

Answer 11

The right phrenic nerve runs alongside the right brachiocephalic vein, superior vena cava and pericardium over the right atrium It runs anterior to the hilum of the right lung and pierces the diaphragm near the caval opening (opening for IVC)

Question 12

Describe the course of the left phrenic nerve on its way to the diaphragm?

Answer 12

The left phrenic nerve runs between the left subclavian vein and artery and to the left of the arch of the aorta anterior to the left vagus nerve It runs anterior to the left lung root and passes over the pericardium over the left atrium and ventricle before peircing the diaphragm near the pericardium

Question 13

Where does the trachea begin and what does it branch into and at what level?

Answer 13

The trachea begin at the C6/7 vertebrae level below the larynx and divides into the right and left main bronchi at the carina The carina is a V-shaped cartilage at the T4/5 vertebral level - level of the transverse thoracic plane

Question 14

What makes up the trachea anteriorly and posteriorly?

Answer 14

The trachea is made ofup of C-shaped cartilage anteriorly and posteriorly made up of trachealis muscle The trachealis muscle allows for expansion of the oesophagus into the trachea

Question 15

Is there any trachea in the inferior mediastinum?

Answer 15

As the trachea bifurcates at the transverse thoracic plane allowing the right and left main bronchi to enter the right and left hemi-thoraces, there is no trachea in the inferior mediastinum

Question 16

What type of tissue is the oesophagus and where does it begin? Where does the oesophagus lie in relation to the aorta?

Answer 16

The oesophagus is a fibromuscular tube beginning at the C6 vertebral level as a continuation of the pharynx It initially lies to the right of the aorta and then crosses anteriorly just before piercing the diaphragm at the T10 vertebral level

Question 17

The oesophagus has a short abdominal course before entering the stomach What are the three constrictions in the oesophagus?

Answer 17

There is a constriction at the Arch of the aorta Left bronchus Diaphragm

Question 18

Now we have talked about the structures in the superior mediastinum, lets talk about the posterior mediastinum What are the borders of the posterior mediastinum again? What are the main structures contained within the posterior mediasitnum? (5 things)

Answer 18

Superiorly - transverse thoracic plane Inferiorly - diaphragm Anteriorly - fibrous pericardium Posteiorly - vertebral bodies T5-12 Laterally -Parietal Pleura Contains oesophagus, thoracic duct, sympathetic chains, descending aorta, azygous veins

Question 19

When does the arch of the aorta become the descending aorta? (thoracic aorta) What branches come of the thoracic aorta? When does the descending aorta become the abdominal aorta?

Answer 19

The arch of the aorta becomes the descending aorta at the transverse thoracic plane Branches: * Braonchial * Oesophageal * Pericardial * Thoracic wall * Diaphragm It becomes the abdominal aorta once the aorta passes through the diaphragm

Question 20

The azygous venous system is in the posterior inferior mediastinum The azygous venous sytem drains the posterior intercostal veins Where do the right posterior intercostal veins drain?

Answer 20

1st posterior intercostal vein - drains to the right brachiocephalic vein 2-11 posteiror intercostal veins and subcostal vein drains into the azygous vein which drains into the superior vena cava

Question 21

Where do the left posterior intercostal veins drain?

Answer 21

1-4 left posterior intercostal veins - drain into the left brachiocephalic vein 5-8 left posterior intercostal veins - drain into the accessory hemiazygous veins 9-11 + subcostal veins drain into the hemiazygous vein Accessory hemiazygous and hemiazygous veins drain into the azygous vein

Question 22

What is the thoracic duct a continuation of? The thoracic duct runs superiorly on the surface of the vertebral bodies What two vessels does the thoracic duct run between?

Answer 22

The thoracic duct is a direct continuation of the cisterna chyli It runs between the azygous vein and the descending aorta

Question 23

What branches join the thoracic duct to form the left lymphatic duct?

Answer 23

The left lymphatic duct is formed by the left bronchomediastinal trunk, left subclavian trunk and left jugular trunk joining the thoracic duct Usually a very pale and thin structure

Question 24

Chain of sympathetic ganglia extending the length of the vertebral column on either side What is this? Where does the sympathetic outflow exist between?

Answer 24

Chain of sympathetic ganglia extending the length of the vertebral column on either side - this is the sympathetic chain Sympathetic outflow exists between T1-L2 vertebrae (this is where the spinal cord has lateral horns in the grey matter)

Question 25

Splanchnic nerves are the nerves which pass through the sympathetic chain without synapsing What are the three nerves arising in the posterior aspect of the inferior mediastinum division of the thoracic cavity that supply sympathetic innervation to the abdominal viscera?

Answer 25

Greater splanchnic nerve Lesser splanchnic nerve Least splanchnic nerve

Question 26

From what sympathetic ganglia from the sympathetic chain do the three splanchnic nerves supply sympathetics to the abdominal viscera arise from?

Answer 26

Greater splanchnic nerve - T5-T9 ganglia Lesser splanchnic nerve - T10,11 ganglia Least splanchnic nerve - T12 ganglia

Question 27

The splanchnic nerves arising from the sympathetic chain pass through the diaphragm to synapse as plexuses on arterial structures before heading to supply the abdominal organs What is the name of the ganglia formed by the greater, lesser and least splanchnic nerves plexuses?

Answer 27

Greater splanchnic nerve - synapse in the coeliac and superior mesenteric ganglia Lesser splanchnic nerve - synapse in the superior mesenteric and aorticorenal ganglia Least splanchnc nerve - synapse aorticorenal ganglia

Question 28

What travels through the diaphragm at T8, T10, T12? Dont forget where do the splanhcnic nerves pass through and what are the openings called

Answer 28

T8 - inferior vena cava at caval opening T10 - oesophagus with vagal trunk(s) at oesophageal hiatus T12 - aorta, thoracic duct, azygous vein through the aortic hiatus Greater ad lesser splanchnic nerves through openings in the crura at T12 Least splanchnic nerve and sympathetic chain behind the medial arcuate ligament

Question 29

What is the medial arcuate ligament?

Answer 29

The medial arcuate ligament is a tendinous fascia that arches over the psoas major muscle as it passes through the diaphragm - the least splanchnic nerve and sympathetic chain pass into the abdomen behind this ligament

Question 30

Which structures pass through an opening in the central tendon of the diaphragm?

Answer 30

The inferior vena cava at the caval opening and The right phrenic nerve which pierces the diaphragm near the caval opening