Superior and Posterior Mediastinum

Question 1

What are the boudnaries of the mediastinum?

Answer 1

upper limit is the thoracic inlet (rib 1, manubrium, T1 vertebral body), lower limit is the diaphragm

posterior boundary is the vertebral bodies of T1-T12
Anterior boundary is the sternum

Question 2

What are the contents of the superior mediastinum?

Answer 2

thymus gland, arch of the aorta (with brachiocephalic trunk, left common cartodi, and left subclavian branches), superior vena cava, right and left brahciocephalic veins and the termination of the azygos vein into the SVC, trachea, esophagus

Question 3

What artery does the vagus nerve run with on the right? on the left?

Answer 3

right - brachiocephalic artery

left - subclavian artery

Question 4

What does the recurrent laryngeal nerve loop around on the right? on the left?

Answer 4

right - subclavian

left - arch of the aorta

Question 5

What is just adjacent to where the left recurren laryngeal nerve loops under the arch?

Answer 5

the ligamentous arteriosum

Question 6

What passes through the aortic hiatus with the thoracic aorta?

Answer 6

the thoracic duct and axygos vein to the right

Question 7

What are the 4 major branches of the thoracic aorta?

Answer 7

posteiror intercostal arteries
subcostal arteries
visceral branches to esophagus, bronhci, mediastinum and pericardium
superior phrenic to diaphragm

Question 8

What type of muscle makes up the esophagus?

Answer 8

the upper 1/3 is skeletl muscle
the middle section transitions to smooth musc
ethe lower 1/3 is all smooth muscle

Question 9

What are the three constriction sof the esophagus?

Answer 9

1. cricopharyngeus muscle
2. aortic arch crossing its anterior surface with the left primary bronchus below the arch
   3 .diaphragm, as the esophagus passes into the abomen (lower esophageal sphincter)

Question 10

Why are the constrictions of the esophagus important clinically?

Answer 10

1. forein objects are more likely to lodge there
2. perforations are possible there
3. carcinomas are more common there

Question 11

What nerves contribute to the esophageal plexus of nerves?

Answer 11

the right and left vagus

note - the right forms the posterior plexus and the left forms the anterior plexus.

Question 12

What do the anterior and posterior esophageal plexi form caudally?

Answer 12

the anterior and posterior vagal trunks

Question 13

THe sympathetic fibers that inhibit peristalsis are mostly postganlgionic from T1-T5, but there are also some pregalnglionic fibers from what nerve?

Answer 13

greater splanchnic nerve

Question 14

What fibers carry pain information in this area?

Answer 14

visceral afferents in the sympathetic fibers

Question 15

Where does blood supply to the esophagus come from?

Answer 15

branches of the thoracic aorta in the thorax

branches of the abdominal arota also supply the lower esophagus via the esophageal hiatus

Question 16

Venous drainage from the submucosal plexuses goes where?

Answer 16

to the azygous and hemiazygous system

Question 17

What are some of the symptoms you get from an aortic aneurysm and why?

Answer 17

hoarseness (pressure on left recurrent)
dysphagia (pressure on esophagus)
dysnea (pressure on the trachea)

Question 18

What consisutes the main lymphatic return to the venous system? What percentage of lymph does it carry?

Answer 18

the thoracic duct - carries 75% of the lymph of the body back to the venous system

Question 19

What does the thoracic duct drain?

Answer 19

the cisterna chyli in the abdomen at T12-L1

Question 20

Where does the thoracic duct terminate?

Answer 20

at the confluence of the left interna ljugular and subclavian veins

Question 21

What do you call it when the throacic duct is lacerated, spilling lymph into the thoracic cavity?

Answer 21

a chylothorax

Question 22

What veins join to form the azygos vein?

Answer 22

the right subcostal vein and the right ascending lumbar vein from the abdomen

Question 23

At T4, what does the azygos vein form?

Answer 23

the arch of the azygous vein over the right bronchus

Question 24

What does the azygos vein dump into?

Answer 24

svc

Question 25

Why is the azygos system important clinically?

Answer 25

it forms an anastomosis between the inferior and superior vena cava and will form an important alternative circulation in case of obstruction of either vessel

Question 26

Som epreganglionic sympathetic fibers DO NOT synapse in the sympathetic chain but instead pass forward as wehat/

Answer 26

the splanchnic nerves (greater T5-9, lesser T10-11, least T12)

Question 27

Where do the splanchnic nerve fibers travel to synapse?

Answer 27

prevertebral ganglia - either celiac or superior mesenteric