Anatomy Lecture 3 -- The Mediastinum

Question 1

Subdivisions of the mediastinum

Answer 1

Anterior Superior Posterior Middle

Question 2

Anterior boundary of the mediastinum

Answer 2

Sternum

Question 3

Posterior boundary of the mediastinum

Answer 3

Thoracic vertebrae

Question 4

Lateral boundaries of the mediastinum

Answer 4

Ribs

Question 5

Define the mediastinum

Answer 5

Organs contained in the middle of the thoracic cavity that are not the lungs

Question 6

Ribs in the superior subdivision of the mediastinum

Answer 6

Ribs 1 and 2

Question 7

Boundary of superior mediastinum

Answer 7

T1 to T4

Question 8

Contents of the superior mediastinum

Answer 8

Vessels, namely the aortic arch Trachea

Question 9

Contents of the posterior mediastinum (from most posterior to most anterior)

Answer 9

Descending aorta Thoracic duct Eosophagus

Question 10

What happens to the contents of the mediastinum when you lie down to sleep at night?

Answer 10

Heart moves upwards and backwards in the curvature (a difference of 1 - 2 vertebrae), thus pulling the other structures with it

Question 11

4 reasons why T4 is a clinical landmark

Answer 11

Trachea bifurcates Thoracic duct crosses to dump load into the brachiocephalic vein on the left Upper border of the heart Manubriosternal angle

Question 12

Location of the phrenic nerve in the mediastinum

Answer 12

Infrton of the hilum, glued to the left ventricular pericardium, descending from C 3, 4, and 5.

Question 13

Phrenic nerve function

Answer 13

Feed diaphragm efferent information Secondarily transmit sensation to the pericardium and pleura

Question 14

Describe the pathway of the vagus nerve in the mediastinum

Answer 14

Wanderer/ hobo nerve. Behind the hilum and encircles esophagus at a lower point. Hooks around the ligament between the pulmonary trunk and aortic arch to become the recurrent laryngeal nerve

Question 15

Recurrent laryngeal nerve function

Answer 15

Innervate the larynx (cut = no speech)

Question 16

Where does the intercostal space 1 vein empty to?

Answer 16

Vertebral vein

Question 17

Which veins join to become the left superior intercostal vein?

Answer 17

Intercostal space veins 2 and 3

Question 18

Which veins join to form the superior hemiazygous vein?

Answer 18

Intercostal space veins 4, 5, 6

Question 19

Which veins join to form the inferior hemiazygous vein?

Answer 19

Intercostal space veins 7 - 12

Question 20

Where do all of the intercostal arteries come from? What is the exception?

Answer 20

All come from aorta except 1 and 2, which come from subclavian artery

Question 21

Inferior boundary of the mediastinum

Answer 21

Diaphragm

Question 22

Where does the esophagus exit the mediastinum?

Answer 22

At the level of T10 through the diaphragm

Question 23

Where does the aorta exit the mediastinum?

Answer 23

At the level of T12 through the diaphragm

Question 24

What is the significance of the hole formed by the esophagus in the diaphragm?

Answer 24

Potential diaphragmatic herniation at the T10 hole, causing regurgitation and spontaneous vomiting (a reflux condition) If the hole is big enough, the whole stomach can move through into the mediastinum

Question 25

What is a potential cause of diaphragmatic herniation at T10?

Answer 25

Woman with several pregnancies can eventually stress the esophageal hole to the point where it widens too much

Question 26

Define the boundaries of the sympathetic trunk

Answer 26

T1 to L2

Question 27

Describe the relationship of the intercostal nerves to the sympathetic system

Answer 27

Pick up post ganglionic fibres from the sympathetic trunk

Question 28

What are the beads at each intercostal nerve?

Answer 28

Synapses between pre-ganglionic and post-ganglionic fibres

Question 29

What happens to the pre-ganglionic fibres that do not synapse in the mediastinum?

Answer 29

Form the splachnic nerve series that travels to the abdomen

Question 30

Describe the sources of sensation in the diaphragm

Answer 30

Middle = phrenic nerve Edges (and pleura) = intercostals

Question 31

What is the superior vena cava actually comprised of?

Answer 31

The two brachiocephalic veins

Question 32

Where does the parasympathetic nervous system come from?

Answer 32

Vagus

Question 33

6 effects of sympathetic system activation

Answer 33

1) Rate and strength of contraction of heart increases 2) Coronary artery dilation 3) Dilation of bronchi = max air input (main secondary and tertiary) 4) Redirect blood from G.I. to arm/leg muscles 5) Liver: glycogen -> glucose 6) Adrenal gland = adrenaline