Lecture4

Question 1

Division of the mediastinum

Answer 1

Superior mediastinum
Inferior mediastinum :
Anterior
Posterior
Middle

Question 2

Location of superior mediastinum

Answer 2

Posterior to the manubrium of the sternum and anterior to the bodies of the first 4 TV.
Its superior boundary is an oblique plane passing from the jugular notch upward and posteriorly to the superior border of T1.
Inferiorly a transverse plane passing from the sternal angle to the intervertebral discs between TIV/V seperates it from the inferior mediastinum.
Laterally it is borderd by the mediastinal part of the prietal pleurae on each side.

Question 3

Main contents of the mediastinum

Answer 3

Thymus 
R&L bracheocephalic veins
Left superior intercostal vein
SVC
arch of aorta and its branches
Trachea and esophagus
Phrenic nerves
Vagus nerves
Left recurrent laryngal branch of the left vagus nerve
Thoracic duct
Small nerves,blood vessels and lymphatics

Question 4

Location of thymus

Answer 4

Most anterior component of the superior mediastinum lying immediately posterior to the manubrium of the sternum and anterior to the great vessels its an asymmetrical bilobed structure.
The upper part can reach into the neck as high as the thyroid gland, the lower portion typically extend into the anterior mediastinum

Question 5

Roles of the thymus

Answer 5

Involved in the early development of the immune system, its a large structure in child that begins to atrophy after puberty and shows size variations in adults, in the elderly adult its barely identifiable as an organ consisting mostly of fatty tissue arranged sometimes as two lobulated fatty structure.

Question 6

Vasculature of the thymus

Answer 6

Arteries consists of small branches origanating from the imternal thoracic arteries.
Venous drainage is usually into the left brachecephalic vein and possibly the internal thoracic veins.

Question 7

Lymphatics of the thymus

Answer 7

Multiple groupof nodes at one or more of the following locations:
Along the internal thoracic arteries(parasternal).
At the tracheal bifurcation ( tracheobronchial).
In the root of the neck.

Question 8

Location of brachecephalic veins

Answer 8

Immediately posterior to the thymus, they form on each side at the junction between the internal jugular and subclavian veins. The left bc vein crosses the midline and joins with the right brachecephalic vein to form the SVC

Question 9

Venous tributaries of the right BC vein

Answer 9

Vertebral, right first posterior intercostal and internal thoracic veins. The inferior thyroid and thymic veins may also drain in it.

Question 10

Location of the right BC vein

Answer 10

begins posterior to the medial end of the right clavicle and passes vertically downward, forming the superior vena cava when it is joined by the left brachiocephalic vein

Question 11

Location of left BC vein

Answer 11

begins posterior to the medial end of the left clavicle. It crosses to the right, moving in a slightly inferior direction, and joins with the right brachiocephalic vein to form the superior vena cava posterior to the lower edge of the right first costal cartilage close to the right sternal border

Question 12

Venous tributaries to the left BC vein

Answer 12

include the vertebral, first posterior intercostal, left superior intercostal, inferior thyroid, and internal thoracic veins. It may also receive thymic and pericar- dial veins.

Question 13

Tributaries of the left superior intercostal vein

Answer 13

The left superior intercostal vein receives the second, third, and sometimes the fourth posterior intercostal veins, usually the left bronchial veins, and sometimes the left pericardiacophrenic vein.

Question 14

Location of the left superior intercostal vein

Answer 14

It passes over the left side of the aortic arch, lateral to the left vagus nerve and medial to the left phrenic nerve, before entering the left brachiocephalic vein.Inferiorly, itmay connect with the accessory hemiazygos vein (superior hemia- zygos vein).

Question 15

Location of the SVC

Answer 15

The vertically oriented superior vena cava begins posterior to the lower edge of the right first costal cartilage, where the right and left brachiocephalic veins join, and terminates at the lower edge of the right third costal cartilage, where it joins the right atrium

Question 16

Tributaries of the SVC

Answer 16

The superior vena cava receives the azygos vein imme- diately before entering the pericardial sac and may also receive pericardial and mediastinal veins.

Question 17

Arch of aorta is divided to

Answer 17

Ascending aorta
Descending aorta
Arch of aorta

Question 18

Location of aortic arch

Answer 18

It begins when the ascending aorta emerges from the pericardial sac and courses upward, backward, and to the left as it passes through the superior mediastinum, ending on the left side at vertebral level TIV/V. Extending as high as the midlevel of the manubrium of the sternum, the arch is initially ante- rior and finally lateral to the trachea.

Question 19

What is the first branch of the aortic arch

Answer 19

The bracheocephalic trunk lies anterior to the trachea and posterior to the left BC vein It is the largest of the three branches and, at its point of origin behind the manubrium of the sternum, is slightly anterior to the other two branches. It ascends slightly posteriorly and to the right. At the level of the upper edge of the right sternoclavicular joint

Question 20

the brachiocephalic trunk divides into

Answer 20

The right common carotid artery
The right subclavian artery

Occasionally, the brachiocephalic trunk has a small branch, the thyroid ima artery, which contributes to the vascular supply of the thyroid gland.

Question 21

The second branch of the aortic arch is

Answer 21

the left common carotid artery .It arises from the arch immediately to the left and slightly posterior to the brachiocephalic trunk and ascends through the superior mediastinum along the left side of the trachea.

Question 22

The third branch of the aortic arch is

Answer 22

the left sub- clavian artery. It arises from the arch of the aorta immediately to the left of, and slightly posterior to, the left common carotid artery and ascends through the superior mediastinum along the left side of the trachea.

Question 23

The role of the ligamentum arteriosum

Answer 23

is important in embryonic circulation, when it is a patent vessel (the ductus arteriosus). It con- nects the pulmonary trunk with the arch of the aorta and allows blood to bypass the lungs during development. The vessel closes soon after birth and forms the ligamentous connection observed in the adult.

Question 24

Location of trachea and esophagus

Answer 24

The trachea is a midline structure that is palpable in the jugular notch as it enters the superior mediastinum. Posterior to it is the esophagus, which is immediately anterior to the vertebral column.
As the trachea and esophagus pass through the superior mediastinum, they are crossed laterally by the azygos vein on the right side and the arch of the aorta on the left side.

Question 25

Route of the right vagus nerve

Answer 25

enters the superior mediastinum and lies between the right brachiocephalic vein and the brachiocephalic trunk. It descends in a posterior direction toward the trachea, crosses the lateral surface of the trachea, and passes posteriorly to the root of the right lung to reach the esophagus. Just before the esopha- gus, it is crossed by the arch of the azygos vein.

Question 26

Branches of the right vagus nerve

Answer 26

As the right vagus nerve passes through the superior mediastinum, it gives branches to the esophagus, cardiac plexus, and pulmonary plexus.

Question 27

Route of the left vagus nerve

Answer 27

enters the superior mediastinum posterior to the left brachiocephalic vein and between the left common carotid and left subclavian arteries. As it passes into the superior mediastinum, it lies just deep to the mediastinal part of the parietal pleura and crosses the left side of the arch of the aorta. It continues to descend in a posterior direction and passes posterior to the root of the left lung to reach the esophagus in the posterior mediastinum.

Question 28

Branches of the left vagus nerve

Answer 28

it gives branches to the esophagus, the cardiac plexus, and the pulmonary plexus.
The left vagus nerve also gives rise to the left recurrent laryngeal nerve, which arises from it at the inferior margin of the arch of the aorta just lateral to the ligamen- tum arteriosum. The left recurrent laryngeal nerve passes inferior to the arch of the aorta before ascending on its medial surface. Entering a groove between the trachea and esophagus, the left recurrent laryngeal nerve continues superiorly to enter the neck and terminate in the larynx.

Question 29

Route of the right phrenic nerve

Answer 29

The right phrenic nerve enters the superior mediastinum lateral to the right vagus nerve and lateral and slightly
posterior to the beginning of the right brachiocephalic vein. It continues inferiorly along the right side of this vein and the right side of the superior vena cava.
On entering the middle mediastinum, the right phrenic nerve descends along the right side of the pericardial sac, within the fibrous pericardium, anterior to the root of the right lung. The pericardiacophrenic vessels accompany it through most of its course in the thorax. It leaves the thorax by passing through the diaphragm with the inferior vena cava.

Question 30

Route of the left phrenic nerve

Answer 30

The left phrenic nerve enters the superior mediastinum in a position similar to the path taken by the right phrenic nerve. It lies lateral to the left vagus nerve and lateral and slightly posterior to the beginning of the left brachioce- phalic vein, and continues to descend across the left lateral surface of the arch of the aorta, passing superficially to the left vagus nerve and the left superior intercostal vein.
On entering the middle mediastinum, the left phrenic nerve follows the left side of the pericardial sac, within the fibrous pericardium, anterior to the root of the left lung, and is accompanied by the pericardiacophrenic vessels. It leaves the thorax by piercing the diaphragm near the apex of the heart.

Question 31

Route of the thoracic duct

Answer 31

It ascends between the thoracic aorta on its left, the azygos vein on its right, the esophagus anteriorly, and the vertebral bodies posteriorly.
• At the level of the T4–T6 vertebrae, the thoracic duct crosses to the left, posterior to the esophagus, and ascends into the superior mediastinum
• The thoracic duct continues through the superior mediastinum, posterior to the arch of the aorta, and the initial portion of the left subclavian artery, between the esophagus and the left mediastinal part of the parietal pleura.

Question 32

Location of the middle mediastinum and its contents

Answer 32

centrally located in the thoracic cavity. It contains the pericardium, heart, origins of the great vessels, various nerves, and smaller vessels.

Question 33

Contents of the serous pericardium

Answer 33

The parietal layer of serous pericardium lines the inner surface of the fibrous pericardium.
The visceral layer (epicardium) of serous pericar- dium adheres to the heart and forms its outer covering.

The parietal and visceral layers of serous pericardium are continuous at the roots of the great vessels. The narrow space created between the two layers of serous pericar- dium, containing a small amount of fluid, is the pericar- dial cavity. This potential space allows for the relatively uninhibited movement of the heart.

Question 34

Fibrous pericardium shape and attachment

Answer 34

The fibrous pericardium is a cone-shaped bag with its base on the diaphragm and its apex continuous with the adventitia of the great vessels. The base is attached to the central tendon of the diaphragm and to a small muscular area of the diaphragm on the left side. Anteriorly, it is attached to the posterior surface of the sternum by sternopericardial ligaments. These attach- ments help to retain the heart in its position in the thoracic cavity. The sac also limits cardiac distention.

Question 35

Vasculature and innervation of fibrous pericardium

Answer 35

The phrenic nerves, which innervate the diaphragm and originate from spinal cord levels C3 to C5, pass through the fibrous pericardium and innervate the fibrous pericar- dium as they travel from their point of origin to their final destination . Their location, within the fibrous pericardium, is directly related to the embryological origin of the diaphragm and the changes that occur during the formation of the pericardial cavity. Similarly, the pericardiacophrenic vessels are also located within and supply the fibrous pericardium as they pass through the thoracic cavity.

Question 36

Locations of the reflection of serous pericardium

Answer 36

one superiorly, surrounding the arteries—the aorta and the pulmonary trunk.
the second more posteriorly, surrounding the veins—the superior and inferior vena cava and the pulmonary veins.

Question 37

Vasculature and innervation of the pericardium

Answer 37

The pericardium is supplied by branches from the internal thoracic, pericardiacophrenic, musculophrenic, and infe- rior phrenic arteries, and the thoracic aorta.
Veins from the pericardium enter the azygos system of veins and the internal thoracic and superior phrenic veins. Nerves supplying the pericardium arise from the vagus nerve [X], the sympathetic trunks, and the phrenic nerves.

Question 38

Sides of the heart

Answer 38

A diaphragmatic (inferior) surface: this surface faces inferiorly and rests on the diaphragm. it consists of the left ventricle and a small portion of the right ventricle separated by the posterior interventricular groove and extends from the base to the apex of the heart.

An anterior (sternocostal) surface: oriented anteriorly: faces anteriorly and consists mostly of the right ventricle, with some of the right atrium on the right and some of the left ventricle on the left

A right pulmonary surface: consists of the right atrium

A left pulmonary surface: consists of the left ventricle and a portion of the left atrium

Question 39

Contents and location of the base of the heart

Answer 39

It consists of:
the left atrium,
a small portion of the right atrium, and
the proximal parts of the great veins (superior and inferior venae cavae and the pulmonary veins).

the base of the heart is fixed posteriorly to the pericardial wall, opposite the bodies of vertebrae TV to TVIII (TVI to TIX when standing). The esophagus lies immediately posterior to the base.

Question 40

Borders and margins of the heart

Answer 40

The right and left margins are the same as the right and left pulmonary surfaces of the heart.

The inferior margin is defined as the sharp edge between the anterior and diaphragmatic surfaces of the heart it is formed mostly by the right ventricle and a small portion of the left ventricle near the apex.

Superior border: formed by the right and left atria and auricles in an anterior view.

The obtuse margin separates the anterior and left pulmonary surfaces it is round and extends from the left auricle to the cardiac apex, and is formed mostly by the left ventricle and superiorly by a small portion of the left auricle.