3.1.5. ANATOMY Mediastinum

Question 1

What is the pericardium?

Answer 1

Fibro-serous membrane that covers the heart and the beginning of its great vessels

Question 2

What are the layers of the pericardium?

Answer 2

1. Fibrous pericardium
2. Serous pericardium

Question 3

What are the boundaries of the fibrous pericardium?

Answer 3

Attached anteriorly to the posterior surface of the sternum by the sternopericardial ligaments

Bound posteriorly by loose connective tissue to structures in the posterior mediastinum

Continuous inferiorly with the central tendon of the diaphragm

Question 4

What composes the fibrous pericardium? The serous pericardium?

Answer 4

The fibrous pericardium is Connective tissue with tunica adventitia Serous pericardium is composed mainly of mesothelium

Question 5

What are the layers of the serous pericardium? Describe them.

Answer 5

The serous pericardium, is divided into two layers, the parietal pericardium, which is fused to and inseparable from the fibrous pericardium, and the visceral pericardium, which is part of the epicardium. Both of these layers function in lubricating the heart to prevent friction during heart activity. There is fluid in between these layers to prevent friction.

Question 6

What is the transverse thoracic plane?

Answer 6

Transects the sternal angle through the T5 vertebrae

Question 7

Where is the superior mediastinum?

Answer 7

Extends inferiorly from the superior thoracic aperture to the horizontal plane that includes the sternal angle anteriorly and passes approximately through the junction of T4 and T5 vertebrae posteriorly

Question 8

Where and what is located in the anterior portion of the inferior mediastinum?

Answer 8

Smallest subdivision of the inferior mediastinum:

Lies between the body of the sternum and transversus thoracis muscles anteriorly and the pericardium posteriorly

Consists of loose connective tissue (sternopericardial ligaments), fat, lymphatic vessels, a few lymph nodes, and branches of the internal thoracic vessels

Question 9

What is the middle portion of the inferior mediastinum

Answer 9

Include the pericardium and its contents

Question 10

Where is the posterior portion of the inferior mediastinum?

Answer 10

Inferior to the transverse thoracic plane, anterior to the T5-T12 vertebra, posterior to the pericardium and diaphragm, and between the parietal pleura of the two lungs

Question 11

What are the levels of the viscera relative to the mediastinal divisions in a supine individual?

Answer 11

When a person is supine or when a cadaver is dissected, the viscera are positioned higher (more superior) relative to subdivisions of the mediastinum than when the person is upright

Question 12

What direction do the viscera move when we are standing?

Answer 12

Gravity pulls the viscera downward when we are vertical

Question 13

Where is the arch of the aorta, the trachea, and the central tendon of the diaphragm when we are supine?

Answer 13

Arch of the aorta lies superior to the transverse thoracic plane

Bifurcation of the trachea is transected by the transverse thoracic plane

Central tendon of the diaphragm lies at the level of the xiphisternal junction and vertebra T9

Question 14

Where is the arch of the aorta, the trachea, and the central tendon of the diaphragm when we are standing or sitting upright?

Answer 14

Arch of the aorta is transected by the transverse thoracic plane

Tracheal bifurcation lies inferior to the transverse thoracic plane

Central tendon of the diaphragm may fall to the level of the middle of the xiphoid process and T9-T10 IV discs

Question 15

What are the steps of the cardiac cycle?

Answer 15

1. Venous return to the right atrium
2. Venous flow arrives in the right ventricle
3. Venous blood is sent in the lung via the pulmonary artery
4. After oxygenation in the lung, the blood returns to the left atrium
5. Oxygenated blood arrives in the left ventricle
6. Blood is sent through the aorta and to the rest of the body, including the heart itself.

Question 16

What is a myocardial infarction?

Answer 16

Sudden occlusion of a major artery by an embolus that results in the region of myocardium supplied by the occluded vessel becoming infarcted (rendered bloodless) and undergoes necrosis

An area of myocardium that has undergone necrosis

Question 17

What are the three most common sites of coronary artery occlusion?

Answer 17

Anterior IV (LAD) branch of the LCA [40-50%]

RCA [30-40%]

Circumflex branch of the LCA [15-20%]

Question 18

What is cardiac referred pain?

Answer 18

The heart is insensitive to touch, cutting, cold, and heat; however, ischemia and the accumulation of metabolic products stimulate pain endings in the myocardium

Noxious stimuli originating in the heart are perceived by a person as pain arising from a superficial part of the body

Question 19

Where is the most common location for cardiac referred pain?

Answer 19

Left upper limb

Question 20

Describe the conduction pathway of a heart contraction

Answer 20

1. SA node fires
2. Excitation spreads through atrial myocardium
3. AV node fires
4. Excitation spreads down AV bundle
5. Purkinje fibers distribute excitation through the ventricular myocardium

Question 21

What are these areas of auscultation?

Question 22

What is happening at these heart sounds?

Question 25

What “s” beats are these?