Mediastinum - Middle

Question 1

Describe the anatomical position of the heart:

Answer 1

Heart is located within the mediastinum
Superior to the diaphragm
Anterior to the vertebral column
Posterior to the sternum
Medial to the hilum of the lungs
The apex of the heart is located in the 5th intercostal space near the midclavicular line

Question 2

Describe the pericardium:

Answer 2

A two-layered fibro-serous sac surrounding the heart and great vessels.
It lies posterior to the body of sternum and anterior to the thoracic vertebrae
Made of fibrous and serous pericardium
Serous pericardium divided into parietal and visceral pericardium
Pericardial cavity - space between serous layers
Pericardial fluid - secreted by serous layers to reduce fluid

Question 3

Describe the fibrous pericardium:

Answer 3

Attached by sternopericardial ligaments and attached to sternum
Fuses with tunica adventitia of great vessels
Fuses with central tendon
Protects against sudden overfilling
Physical barrier for protection
Rich in collagen

Question 4

Describe the serous pericardium:

Answer 4

Closed sac formed from
Parietal layer - lines fibrous
pericardium, great vessels, continuous with visceral layer
Visceral layer - lines the heart
Pericardial cavity contains
lubricating pericardial fluid

Question 5

Describe the development of the pericardium:

Answer 5

Embryologically the heart begins as a tube
Lined by a double layer of continuous pericardium
As the heart twists and folds, chambers form
Causes spaces or sinuses to occur

Question 6

Describe the transverse pericardial sinus

Answer 6

Located posterior to aorta and pulmonary trunk
Transverse recess of serous pericardium
Located between ascending aorta and pulmonary trunk, and upper parts of the atria and superior vena cava
In pericardial space
Important landmark in cardiac surgery

Question 7

Describe the oblique pericardial sinus:

Answer 7

Located;
Posterior to the heart
Near pulmonary veins and inferior vena cava
Where visceral serous pericardium becomes parietal serous pericardium
A recess of serous pericardium

Question 8

Describe the arterial supply to the pericardium

Answer 8

Pericardiacophrenic arteries - main, branches from internal thoracic artery, travels next to phrenic nerve

Musculophrenic arteries - terminal branches, supplies the lower parts of the pericardium

Pericardial branches from the bronchial and superior phrenic arteries

Question 9

Describe the venous drainage for the pericardium

Answer 9

Pericardial veins drain to the azygos system
Drain anteriorly into;
Internal thoracic
Superior phrenic

Question 10

Describe the phrenic nerve

Answer 10

Formed by ventral rami of C3-C5 spinal nerves
Passes anterior to the anterior scalene muscle
Located between fibrous pericardium and the mediastinal parietal pleura
Terminates at diaphragm
Innervates the structures it passes
Passes anteriorly to the hilum of the lungs

Question 11

Describe the sternocostal/ anterior surface of the heart

Answer 11

Upper border - formed by atria, hidden anteriorly

Right border - formed by right atrium, slightly convex due to curve

Lower border - formed by right ventricle, slightly concave as sits on central tendon of diaphragm, marginal branch of right coronary artery runs

Left border - formed by left ventricle and atrium, convex

Question 12

Describe the base of the heart:

Answer 12

Formed by mainly left atrium
Lies opposite thoracic vertebrae T5 - T8
Separated from the descending aorta and oesophagus by oblique sinus

Question 13

Describe the diaphragmatic surface of the heart:

Answer 13

Formed by left ventricle
Ventricles are separated by posterior interventricular groove
Separated from base by the coronary sulcus

Question 14

Describe the right atrium

Answer 14

Function - receive deoxygenated blood and pump it into RV
Blood flows into the right atrium from three primary vessels: Superior vena cava, inferior vena cava, and coronary sinus
Tricuspid valve separates the right atrium from the right ventricle, ensuring one-way flow of blood
Fossa Ovalis - marks location of foramen ovale,
Sinoatrial node - heart’s pacemaker, wall of RA

Question 15

Describe the right ventricle

Answer 15

Receives deoxygenated blood from the right atrium through the tricuspid valve
Pumps blood into the pulmonary artery through the pulmonary valve during systole (contraction), which travels to the lungs for oxygenation
Trabeculae carneae - series of muscular ridges on inner surface that aid contraction during systole
Papillary muscles - some trabeculae carneae give rise to papillary muscles, which anchor the chordae tendineae of the heart valves
Infundibulum - channel deoxygenated blood from the right ventricle into the pulmonary artery

Question 16

Describe the left atrium

Answer 16

Walls of LA are thicker than than RA because it receives blood from the pulmonary veins, which requires more pressure
Receives oxygenated blood from the lungs through four pulmonary veins
During atrial systole pumps blood through bicuspid valve to LV
Smooth walls - maintains low pressure, allowing for smooth blood flow from the pulmonary veins
Musculi pectinati in auricle

Question 17

Describe the left ventricle

Answer 17

Thick, muscular walls composed primarily of cardiac muscle tissue (myocardium)
Necessary to generate the high pressure needed to pump blood throughout the body
Receives oxygenated blood via left atrium via bicuspid valve
During systole LV pumps blood through aorta via aortic valve to systemic circulation
Aortic vestibulae

Question 18

Describe foetal circulation:

Answer 18

1. Placenta oxygenates blood.
2. Blood makes way to right atrium.
3. Blood passes through the foramen ovale to left atrium.
4. Blood in the pulmonary trunk can pass into the aorta.
5. Blood passes from the left atrium to the left ventricle, then systemically.
6. Deoxygenated blood returns