The superior mediastinum

Question 1

arrange the order of structures in the superior mediastinum from anterior to posterior

Answer 1

thymus
large veins
large arteries
trachea (the trachea bifurcates at the level of the sternal angle)
oesophagus & thoracic duct
sympathetic trunks

Question 2

describe the passage of the right vagus nerve

Answer 2

• enters the mediastinum lateral to the right common carotid artery
• It passes anterior to the subclavian artery, this is where it gives on the right recurrent laryngeal nerve
• then passes posterior to the subclavian vein and the superior vena cava.
• the right vagus nerve passes inferoposteriorly and descend through the posterior mediastinum with the oesophagus behind the lung root and heart

Question 3

describe the passage of the left vagus nerve

Answer 3

• enters the mediastinum lateral to the left common carotid artery
• It passes anterior to the subclavian artery and posterior to the left brachiocephalic vein
• When it reaches the lateral side of the arch of the aorta the left recurrent laryngeal nerve branches off to hook under the aorta next to the ligamentum arteriosum ascend to the larynx
• the left vagus nerve continues posterior to the root of the left lung where it breaks into may branches which contribute to the pulmonary and cardiac plexuses.
• hen joins the fibres of the right vagus to branch out and form the oesophageal plexus.

Question 4

where do phrenic nerves enter the superior mediastinum

Answer 4

between the subclavian artery and the origin of the subclavian vein

Question 5

describe how the right phrenic nerve descends

Answer 5

The right phrenic nerve descends lateral to the right brachiocephalic vein, the SVC and then over the pericardium over the right atrium (anterior to the lung root), down to the diaphragm

Question 6

describe how the left phrenic nerve descends

Answer 6

The left phrenic nerve descends between the left subclavian and left common carotid arteries and then crosses the left surface of the arch of the aorta, anterior to the vagus nerve and then passes anterior to the lung root as it runs over the pericardium superficial to the left atrium and ventricle

Question 7

how long is the trachea

Answer 7

13cm

Question 8

describe the structure of the trachea

Answer 8

• fibroelastic walls
• U shipped bars of hyaline cartilage keep the lumen patent
• posterior ends of the cartilage are connected by smooth muscle, the tracheal muscle
• trachea commences in the neck below the larynx at the level of C6 and ends at the low border of T4

Question 9

What is the bifurcation into the left and right main bronchi called?

Answer 9

carina

Question 10

how long is the oesophagus

Answer 10

25cm

Question 11

describe the structure of the oesophagus

Answer 11

• starts at C6
• continuation of the pharynx
• lies anterior to the vertebral column in the neck but as it descends it moves towards the left

Question 12

describe the structure of the thoracic duct

Answer 12

• begins in the abdomen as the cisterns chyle
• ascends through the diaphragm through the opening for the aorta on the right of the midlein
• crosses the midline at T4/T5 then runs on the left of the oesophagus up into the root of the neck

Question 13

how many ganglia does the sympathetic trunk have

Answer 13

12 or 11

• each has white and grey ramps communications
• frist ganglia is fused with the inferior cervical ganglion

Question 14

where do the gray rami go

Answer 14

The gray rami go to all the thoracic spinal nerves. The post ganglionic fibres are distributed with the spinal nerve to the blood vessels, sweat glands and the erector pili muscles of the skin.

Question 15

The first five ganglia give out postganglionic fibres to …..

Answer 15

the heart, aorta, lungs and oesophagus

Question 16

the lower 8 ganglia mainly give preganglionic fibres …

Answer 16

which are grouped to form the splanchnic nerves. They enter the abdomen by piecing the diaphragm.
– The greater splanchnic nerve (going to the foregut) Ganglia 5-9

– The lesser splanchnic nerve (going to the midgut) Ganglia 10 & 11

– The lesser splanchnic nerve (going to the hindgut) Ganglia 12