Mediastinum

Question 1

What divides the superior and inferior mediastinum?

Answer 1

Sternal angle

Question 2

What is the inferior mediastinum subdivided into?

Answer 2

Anterior

Middle

Posterior

Question 3

What are the contents of the anterior mediastinum?

Answer 3

Portion of the thymus

Lymph nodes and lymphatic vessels

Sternoperiardial ligaments

Question 4

What are the contents of the middle mediastinum?

Answer 4

Heart

Ascending aorta and pulmonary trunk

Superior vena cava, azygous vein, inferior vena cava four pulmonary arteries

Phrenic nerve

Pericardiacophrenic artery and vein

Mediastinal lymph nodes

Question 5

What is the pericardial cavity?

Answer 5

Similar to pleural cavity, surrounds the heart, filled with serous fluid

Question 6

What two layers comprise the pericardial sac?

Answer 6

Fibrous pericardium and inner serous membrane

Question 7

What is cardiac tamponade?

Answer 7

Compression of the heart due to a rapid accumulation of excess fluid

Fibrous pericardium is inelastic

Question 8

What is the transverse pericardial sinus?

Answer 8

Portion of the pericardial cavity between the superior vena cava posteriorly and the ascending aorta/PT anteriorly

Question 9

What is the oblique pericardial sinus?

Answer 9

Blind space of pericardial cavity between the left atrium and the posterior wall of the pericardial sac

Question 10

What is the septum transversum?

Answer 10

Plate of mesoderm that incompletely separates the thoracic cavity from the abdominal cavity

Eventually forms the central tendon of the diagphragm

Question 11

Why is the diaphragm innervated by the phrenic nerve (C3,4,5)?

Answer 11

During development the septum transversum is pushed down due to rapid growth of the CNS, so the phrenic nerve is dragged along with it

Question 12

What is a congenital diaphragmatic hernia?

Answer 12

Herniation of abdominal organs into the pleural cavity through a defect in the diaphragm

Results from the failure of the pleuroperitoneal membrane to form or fuse properly with the other contributors to the diaphragm (usually left side)

Causes lung compression and underdevelopment

Question 13

What is an esophageal hiatal hernia?

Answer 13

Herniation of the stomach through an enlarged esophageal hiatus of the diaphragm

Causes dysfunction of the esophageo-gastric sphincter

Infant presents with vomiting after being laid on its back post-feeding

Question 14

What is a parasternal hernia or Foramen of Morgagni?

Answer 14

Herniation of abdominal vescera through the space which surrounds the superior epigastric artery (sternocostal hiatus)

Question 15

What is the superior border of the mediastinum?

Answer 15

Formed by the thoracic inlet

Boundaries are T12 vertebra, rib 1 and superior border of the manubrium

Question 16

What is the inferior border of the mediastinum?

Answer 16

Formed by thoracic outlet

Boundaries are T12 vertebra, diaphragm, xiphoid process

Question 17

What is the course of the phrenic nerve through the middle mediastinum?

Answer 17

Located anterior to the root of the lung between the mediastinal parietal pleura and fibrous pericardium

Question 18

What sensory innervation comes from the phrenic nerve?

Answer 18

Mediastinal pleura

Pericardium

Pleura and Peritoneum covering the central region of the diaphragm

Question 19

What pierces the fibrous pericardium at the apex?

Answer 19

Ascending aorta

Superior Vena Cava

Pulmonary Trunk

Question 20

What pierces the fibrous pericardium at the base of the heart and what is it fused to?

Answer 20

Inferior vena cava

Fused with the central tendon of the diaphragm

Question 21

What pierces the fibrous pericardium posteriorly?

Answer 21

Four pulmonary arteries

Question 22

What structures anchor the fibrous pericardium in the middle mediastinum?

Answer 22

Superior/Posterior - Blends with tunica adventitia of the great vessels

Inferior - blends with central tendon of the diaphragm

Anterior - Tethered to the sternum by the sternopericardial ligaments

Question 23

What two ways is the needle inserted during a pericardiocentesis?

Answer 23

Parasternally into the left 4th or 5th intercostal space

Immediately to the left of the xiphoid process and angled posteriorly/superiorly at 45 degrees

Question 24

What are the borders of the fibrous pericardium?

Answer 24

Corresponds to those of the heart

Except extends to the level of the second costal cartilage

Question 25

What is the fibrous pericardium derived from?

Answer 25

Somatic mesoderm of the lateral plate

Question 26

What are the two layers of the serous pericardium?

Answer 26

Parietal - lines inner surface of the fibrous pericardium Visceral - Located on outer surface of the heart, forms the epicardium

Question 27

Describe the early development of the intraembryonic ceolem

Answer 27

A continuous space in the lateral mesoderm that develops into a horseshoe-shaped cavity in the trilaminar embryo Lateral folding brings the sides together to form a single coelom

Question 28

What septae divide the coelom into pleural, pericardial and peritoneal cavities?

Answer 28

Pleuropericardial membrane and thoracic diaphragm

Question 29

What are the pleuropericardial membranes?

Answer 29

Paired layers of somatic mesoderm that isolate the pleural cavities from the pericardial cavities The fuse together to form the definitive fibrous pericardium, and isolate the pericardial cavity from the pleural cavities Contain the phrenic nerves

Question 30

What four structures fuse to form the thoracic diaphragm?

Answer 30

Septum transversum Paired pleuroperitoneal membranes Dorsal mesentery of the esophagus Myoblasts from the somatic mesoderm of body wall

Question 31

What are the pleuroperitoneal membranes?

Answer 31

Paired layers of somatic mesoderm that fuse with the septum transversum and dorsal mesentery of the esophagus to close the pericardioperitoneal canals