Thorax Gross Anatomy 1

Question 1

What does the base of the heart consist of?

Answer 1

Left atrium, small portion of right atrium and proximal parts of the great veins (venae cavae and pulmonary veins). Because the great veins enter the base of the heart, with the pulmonary veins entering the right and left sides of the left atrium and the superior and inferior venae cavae at the upper and lower ends of the right atrium, 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 2

How is the apex of the heart formed?

Answer 2

By the inferolateral part of the left ventricle and is positioned deep to the left fifth intercostal space, 8 to 9 cm from the midsternal line.

Question 3

What are the surfaces of the heart?

Answer 3

Anterior surface 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.

Heart rests on diaphragmatic surface, which consists of the left ventricle and a small portion of the right ventricle separated by the posterior interventricular groove. Faces inferiorly, rests on the diaphragm, is separated from the base of the heart by the coronary sinus, and extends from the base to the apex of the heart.

Left pulmonary surface faces the left lung, is broad and convex, and consists of the left ventricle and a portion of the left atrium.

Right pulmonary surface faces the right lung, is broad and convex, and consists of the right atrium.

Question 4

What are the margins of the heart?

Answer 4

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

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

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

Question 5

What structures define the cardiac borders?

Answer 5

The right border in a standard posteroanterior view consists of the superior vena cava, the right atrium, and the inferior vena cava.

The left border in a similar view consists of the arch of the aorta, the pulmonary trunk, left auricle, and the left ventricle.

The inferior border consists of the right ventricle and the left ventricle at the apex. In lateral views, the right ventricle is seen anteriorly, and the left atrium is visualized posteriorly.

Question 6

What external sulci divide the heart?

Answer 6

1. Coronary sulcus circles the heart, separating the atria from the ventricles - as it circles the heart, it contains the right coronary artery, the small cardiac vein, the coronary sinus, and the circumflex branch of the left coronary artery.
2. Anterior and posterior interventricular sulci separate the two ventricles—the anterior interventricular sulcus is on the anterior surface of the heart and contains the anterior interventricular artery and the great cardiac vein, and the posterior interventricular sulcus is on the diaphragmatic surface of the heart and contains the posterior interventricular artery and the middle cardiac vein.

Question 7

How are the 4 chambers of the heart separated?

Answer 7

Interatrial, interventricular, and atrioventricular septa separate the four chambers of the heart.

Question 8

How is blood returned to the right atrium?

Answer 8

By the superior and inferior venae cavae, which together deliver blood to the heart from the body; and the coronary sinus, which returns blood from the walls of the heart itself. The superior vena cava enters the upper posterior portion of the right atrium, and the inferior vena cava and coronary sinus enter the lower posterior portion of the right atrium.

Question 9

Where does blood pass to from the right atrium?

Answer 9

From the right atrium, blood passes into the right ventricle through the right atrioventricular orifice. This opening faces forward and medially and is closed during ventricular contraction by the tricuspid valve.

Question 10

Describe the interior structure of the right atrium

Answer 10

Consists of two spaces. Externally, separation indicated by a shallow, vertical groove (the sulcus terminalis cordis), which extends from the right side of superior vena cava opening to the right side of the inferior vena cava opening.

Internally, this division is indicated by the crista terminalis which is a smooth, muscular ridge that begins on the roof of the atrium just in front of the opening of the superior vena cava and extends down the lateral wall to the anterior lip of the inferior vena cava.

Question 11

Describe the two spaces of the right atria

Answer 11

Posterior to crista is the sinus of venae cavae which has smooth, thin walls, and both venae cavae empty into this space. Anterior to crista (including right auricle) referred to as atrium proper whose walls are covered by ridges called the musculi pectinati (pectinate muscles). These muscular pouches also found in right auricle and externally overlaps ascending aorta.

Question 12

What additional structures are present in the right atria?

Answer 12

Opening of the coronary sinus, which receives blood from most of the cardiac veins and opens medially to the opening of the inferior vena cava. Contain valve of coronary sinus and inferior vena cava. Numerous small openings—the openings of the smallest cardiac veins (the foramina of the venae cordis minimae )—are scattered along the walls of the right atrium. These are small veins that drain the myocardium directly into the right atrium.

Question 13

What is the fossa ovalis?

Answer 13

A depression in the septum just above the orifice of the inferior vena cava. Limbus fossa ovalis is the border. This depression is found in the interatrial septum, which faces forward and to the right because the left atrium lies posteriorly and to the left of the right atrium. The fossa ovalis marks the location of the embryonic foramen ovale , which is an important part of fetal circulation.

Question 14

How does blood enter the right ventricle?

Answer 14

Blood entering the right ventricle from the right atrium therefore moves in a horizontal and forward direction. The walls of the inflow portion of the right ventricle have numerous muscular, irregular structures called trabeculae carneae - most are either attached to the ventricular walls throughout their length, forming ridges, or attached at both ends, forming bridges.

Question 15

How does blood leave the right ventricle?

Answer 15

Outflow tract of the right ventricle, which leads to the pulmonary trunk, is the conus arteriosus (infundibulum). This area has smooth walls.

Question 16

What is an alternate function of papillary muscles?

Answer 16

A few trabeculae carneae (papillary muscles) have only one end attached to the ventricular surface, while the other end serves as the point of attachment for tendon-like fibrous cords (the chordae tendineae ), which connect to the free edges of the cusps of the tricuspid valve.

Question 17

What are the 3 papillary muscles?

Answer 17

1. The anterior papillary muscle is the largest and most constant papillary muscle, and arises from the anterior wall of the ventricle.
2. The posterior papillary muscle may consist of one, two, or three structures, with some chordae tendineae arising directly from the ventricular wall.
3. The septal papillary muscle is the most inconsistent papillary muscle, being either small or absent, with chordae tendineae emerging directly from the septal wall.

Question 18

What is the purpose of the septomarginal trabecula?

Answer 18

Forms a bridge between the lower portion of the interventricular septum and the base of the anterior papillary muscle plus carries a portion of the cardiac conduction system, the right bundle of the atrioventricular bundle, to the anterior wall of the right ventricle.

Question 19

Describe the structure of the tricuspid valve

Answer 19

The base of each cusp is secured to the fibrous ring that surrounds the atrioventricular orifice. This fibrous ring helps to maintain the shape of the opening. The cusps are continuous with each other near their bases at sites termed commissures.

Question 20

How are the three cusps of the tricuspid valve arranged?

Answer 20

The naming of the three cusps, the anterior , septal , and posterior cusps , is based on their relative position in the right ventricle. The free margins of the cusps are attached to the chordae tendineae, which arise from the tips of the papillary muscles.

Question 21

How does the tricuspid valve act?

Answer 21

During filling of the right ventricle, the tricuspid valve is open, and the three cusps project into the right ventricle. The papillary muscles and associated chordae tendineae keep the valves closed during the dramatic changes in ventricular size that occur during contraction.

Question 22

What can necrosis of a papillary muscle cause?

Answer 22

Necrosis of a papillary muscle following a myocardial infarction (heart attack) may result in prolapse of the related valve.

Question 23

Describe structure of the pulmonary valve

Answer 23

Located at apex of infundibulum, the outflow tract of the right ventricle. Consists of three semilunar cusps with free edges projecting upward into the lumen of the pulmonary trunk. The free superior edge of each cusp has a middle, thickened portion, the nodule of the semilunar cusp , and a thin lateral portion, the lunula of the semilunar cusp. The cusps are named the left , right, and anterior semilunar cusps.

Question 24

Describe the structure of the left atrium

Answer 24

The posterior half, or inflow portion, receives the four pulmonary veins and has smooth walls. The anterior half is continuous with the left auricle. It contains musculi pectinati and unlike the crista terminalis in the right atrium, no distinct structure separates the two components of the left atrium.

Question 25

What makes up the anterior wall of the left atrium?

Answer 25

The interatrial septum is part of the anterior wall of the left atrium. The thin area or depression in the septum is the valve of the foramen ovale and is opposite the floor of the fossa ovalis in the right atrium.

Question 26

Where does the left ventricle lie?

Answer 26

The left ventricle lies anterior to the left atrium. It contributes to the anterior, diaphragmatic, and left pulmonary surfaces of the heart, and forms the apex.

Question 27

Describe the structure of the left ventricle

Answer 27

Blood enters the ventricle through the left atrioventricular orifice and flows in a forward direction to the apex. The chamber itself is conical, is longer than the right ventricle, and has the thickest layer of myocardium. The outflow tract (the aortic vestibule) is posterior to the infundibulum of the right ventricle, has smooth walls.

Question 28

How is the trabeculae carnae in the left ventricle different to the right ventricle?

Answer 28

The trabeculae carneae in the left ventricle are fine and delicate in contrast to those in the right ventricle. The general appearance of the trabeculae with muscular ridges and bridges is similar to that of the right ventricle.

Question 29

What papillary muscles are found in the left ventricle?

Answer 29

Two papillary muscles, the anterior and posterior papillary muscles , are usually found in the left ventricle and are larger than those of the right ventricle.

Question 30

Describe the interventricular septum

Answer 30

Forms the anterior wall and some of the wall on the right side of the left ventricle. Has two layers: muscular part and membranous part. The muscular part is thick and forms the major part of the septum, whereas the membranous part is the thin, upper part of the septum. A small part of the septum is atrioventricular and exists between the right atrium and left ventricle.

Question 31

Describe the structure of the mitral valve

Answer 31

Has two cusps, the anterior and posterior cusps. The bases of the cusps are secured to a fibrous ring surrounding the opening, and the cusps are continuous with each other at the commissures. The coordinated action of the papillary muscles and chordae tendineae is as described for the right ventricle.

Question 32

Describe the structure of the aortic valve

Answer 32

This valve is similar in structure to the pulmonary valve. It consists of three semilunar cusps with the free edge of each projecting upward into the lumen of the ascending aorta.

Question 33

What is the purpose of the aortic sinuses?

Answer 33

Between the semilunar cusps and the wall of the ascending aorta are pocket-like sinuses—the right, left and posterior aortic sinuses. The right and left coronary arteries originate from the right and left aortic sinuses.

Question 34

How is the aortic valve different to the pulmonary valve?

Answer 34

The functioning of the aortic valve is similar to that of the pulmonary valve with one important additional process: as blood recoils after ventricular contraction and fills the aortic sinuses, it is automatically forced into the coronary arteries because these vessels originate from the right and left aortic sinuses.

Question 35

What are the two types of valve disease?

Answer 35

1. Incompetence (insufficiency), which results from poorly functioning valves
2. Stenosis, a narrowing of the orifice, caused by the valve’s inability to open fully

Mitral valve disease is usually a mixed pattern of stenosis and incompetence, one of which usually predominates.

Question 36

What does valve disease lead to?

Answer 36

1. Left ventricular hypertrophy (this is appreciably less marked in patients with mitral stenosis)
2. Increased pulmonary venous pressure
3. Pulmonary edema
4. Enlargement (dilation) and hypertrophy of the left atrium.

Question 37

What can cause aortic valve disease?

Answer 37

Aortic valve stenosis is the most common type of cardiac valve disease and results from atherosclerosis causing calcification of the valve leaflets. It can also be caused by postinflammatory or postrheumatic conditions.

Question 38

What can aortic valve disease lead to?

Answer 38

May lead to aortic regurgitation such as infective endocarditis, degenerative valve disease, rheumatic fever, or trauma. Can produce marked heart failure.

Question 39

What can valve disease in right side of heart indicate?

Answer 39

Valve disease in the right side of the heart (affecting the tricuspid or pulmonary valve) is most likely caused by infection. Intravenous drug use, alcoholism, indwelling catheters, and extensive burns predispose to infection of the valves, particularly the tricuspid valve. The resulting valve dysfunction produces abnormal pressure changes in the right atrium and right ventricle, and these can induce cardiac failure.

Question 40

Describe course of coronary arteries

Answer 40

1. Arise from the aortic sinuses in the initial portion of the ascending aorta and supply the muscle and other tissues of the heart.
2. Circle the heart in the coronary sulcus, with marginal and interventricular branches, in the interventricular sulci
3. Converge toward the apex of the heart

Question 41

How is venous blood from heart itself returned?

Answer 41

Returning venous blood passes through cardiac veins, most of which empty into the coronary sinus. Coronary sinus empties into the right atrium between the opening of the inferior vena cava and the right atrioventricular orifice.

Question 42

What branches arise from the right coronary artery?

Answer 42

1. Early atrial branch passes in the groove between the right auricle and ascending aorta, and gives off the sinu-atrial nodal branch which passes posteriorly around superior venae cavae to supply sinoatrial node.
2. Right marginal branch is given off as the right coronary artery approaches the inferior (acute) margin of the heart - continues till apex of heart.
3. Posterior interventricular branch lies in the posterior interventricular sulcus and is the final major branch.

Question 43

Summarise what parts the right coronary artery supplies

Answer 43

Right atrium and right ventricle, the sinu-atrial and atrioventricular nodes, the interatrial septum, a portion of the left atrium, the posteroinferior one third of the interventricular septum, and a portion of the posterior part of the left ventricle.

Question 44

What branches arise from the left coronary artery?

Answer 44

The left coronary artery originates from the left aortic sinus of the ascending aorta. It passes between the pulmonary trunk and the left auricle before entering the coronary sulcus. Emerging from behind the pulmonary trunk, the artery divides into its two terminal branches, the anterior interventricular and the circumflex.

Question 45

Describe the branches of the left coronary artery

Answer 45

1. Anterior interventricular branch (left anterior descending artery—LAD) continues around the left side of the pulmonary trunk and descends obliquely toward the apex of the heart in the anterior interventricular sulcus. May give rise to diagonal branches which descend diagonally across the anterior surface of the left ventricle.
2. Circumflex branch courses toward the left, in the coronary sulcus and onto the base/diaphragmatic surface of the heart, and usually ends before reaching the posterior interventricular sulcus. A large branch, the left marginal artery arises from it.

Question 46

Summarise what parts the left coronary artery supplies

Answer 46

Most of the left atrium and left ventricle, and most of the interventricular septum, including the atrioventricular bundle and its branches.

Question 47

What is the implication of this distribution pattern of the coronary arteries?

Answer 47

Means that the posterior interventricular branch arises from the right coronary artery. The right coronary artery therefore supplies a large portion of the posterior wall of the left ventricle and the circumflex branch of the left coronary artery is relatively small.

Question 48

What are the alternative names for coronary vessels?

Answer 48

1. Short left coronary artery -> left main stem vessel
2. Anterior interventricular artery -> left anterior descending artery
3. Posterior interventricular artery -> posterior descending artery

Question 49

What is a heart attack?

Answer 49

A heart attack occurs when the perfusion to the myocardium is insufficient to meet the metabolic needs of the tissue, leading to irreversible tissue damage. The most common cause is a total occlusion of a major coronary artery.

Question 50

Why does occlusion of arteries occur?

Answer 50

Occlusion of a major coronary artery, usually due to atherosclerosis, leads to inadequate oxygenation of an area of myocardium and cell death. Severity of the problem will be related to:
1. Size and location of the artery involved
2. Whether or not the blockage is complete
3. Whether there are collateral vessels to provide perfusion to the territory from other vessels.
Depending on the severity, patients can develop pain (angina) or a myocardial infarction

Question 51

What is percutaneous coronary intervention?

Answer 51

Technique in which a long fine tube (a catheter) is inserted into the femoral artery in the thigh and passed through the external and common iliac arteries and into the abdominal aorta. Moved upward through the thoracic aorta to the origins of the coronary arteries. Fine wire is then passed into the coronary artery and is used to cross the stenosis and balloon inflated at level of obstruction in angioplasty.

Question 52

What are the classic symptoms of a heart attack?

Answer 52

Typical symptoms are chest heaviness or pressure, which can be severe, lasting more than 20 minutes, and often associated with sweating. Pain radiates to the arms (left more common than the right), and can be associated with nausea. The severity of ischemia and infarction depends on the rate at which the occlusion or stenosis has occurred and whether or not collateral channels have had a chance to develop.

Question 53

Are heart attack symptoms the same in men and women?

Answer 53

Although men and women can experience the typical symptoms of severe chest pain, cold sweats, and pain in the left arm, women are more likely than men to have subtler, less recognizable symptoms. These may include abdominal pain, achiness in the jaw or back, nausea, shortness of breath, or simply fatigue.

Question 54

What drains into the coronary sinus?

Answer 54

The coronary sinus receives four major tributaries: the great, middle, small, and posterior cardiac veins.

Question 55

Describe course of great cardiac vein

Answer 55

The great cardiac vein begins at the apex of the heart. It ascends in the anterior interventricular sulcus, where it is related to the anterior interventricular artery and is often termed the anterior interventricular vein. Associates with the circumflex branch of the left coronary artery at base/diaphragmatic surface of the heart. Gradually enlarges to form the coronary sinus, which enters the right atrium.

Question 56

Describe course of middle cardiac vein

Answer 56

Begins near the apex of the heart and ascends in the posterior interventricular sulcus toward the coronary sinus. Associated with the posterior interventricular branch of the right or left coronary artery throughout its course.

Question 57

Describe course of small cardiac vein

Answer 57

Begins in the lower anterior section of the coronary sulcus between the right atrium and right ventricle. Continues in this groove onto the base/diaphragmatic surface of the heart where it enters the coronary sinus at its atrial end.

Question 58

Describe course of posterior cardiac vein

Answer 58

The posterior cardiac vein lies on the posterior surface of the left ventricle just to the left of the middle cardiac vein. Either enters the coronary sinus directly or joins the great cardiac vein.

Question 59

What are the two other cardiac veins?

Answer 59

The anterior veins of the right ventricle drain the anterior portion of the right ventricle.
Veins of Thebesius drain directly into cardiac chambers and are abundant on right side but sometimes associate with left.

Question 60

Describe lymphatic drainage of heart

Answer 60

Brachiocephalic nodes, anterior to the brachiocephalic veins; and
Tracheobronchial nodes, at the inferior end of the trachea.

Question 61

Describe pathway of cardiac conduction

Answer 61

1. Impulses begin at the sinu-atrial node , the cardiac pacemaker. This collection of cells is located at the superior end of the crista terminalis at the junction of the superior vena cava and the right atrium.
2. The excitation signals generated by the sinu-atrial node spread across the atria, causing the muscle to contract.
3. Wave of excitation in the atria stimulates the atrioventricular node, which is located near the opening of the coronary sinus, close to the attachment of the septal cusp of the tricuspid valve, and within the atrioventricular septum.
4. The atrioventricular bundle is a direct continuation of the atrioventricular node. Impulse spreads through here to Purkinje fibres, causing ventricular muscle contraction.

Question 62

Describe atrioventricular bundle structure and how it conducts

Answer 62

It follows along the lower border of the membranous part of the interventricular septum before splitting into right and left bundles. The right bundle branch continues on the right side of the interventricular septum toward the apex of the right ventricle. From the septum it enters the septomarginal trabecula to reach the base of the anterior papillary muscle where it divides into Purkinje fibres. Left bundle branch does the same and this spreads the electrical excitement through the ventricles.