Anatomy of the Heart. Figure 20 2c

Transcription

1 Anatomy of the Heart Figure 20 2c

2 Pericardium & Myocardium

3 Remember, the heart sits in it s own cavity, known as the mediastinum. The heart is surrounded by the Pericardium, a double lining of the pericardial cavity. The pericardium and its fluid lubricate the moving surfaces of the heart. Figure 20 2c

4 The Pericardium, consists of a double lining: Parietal pericardium Is the tough, outer two-layered sac and is fibrous. This sac contains pericardial fluid. It is attached to the diaphragm, the sternum, and the base of the heart. Visceral (epicardium) pericardium Is the thinner, inner layer of pericardium that adheres tightly to the heart. The space between the parietal and visceral pericardium is known as the pericardial cavity and contains the pericardial fluid. Figure 20 2c

5

6 The parietal layer attaches to the large arteries exiting the heart and turns and continues over the external heart surface as the visceral layer (epicardium). The parietal and visceral layers is the pericardial cavity which contains a serous fluid, known as pericardial fluid. This fluid allows the heart to glide smoothly during heart activity in a friction-free environment. Figure 20 2c

7 The visceral layer secretes the pericardial fluid. The myocardium is the heart muscle and is composed mainly of cardiac muscle and forms the bulk of the heart. The endocardium (inside the heart) is a glistening white sheet of endothelium (squamous epithelium) resting on a thin c.t. layer. Figure 20 2c

8 Atria

9 The atria (atrium = entryway) is the receiving chamber and is thin-walled (relatively speaking). This is because it contracts minimally to push blood downstairs into the ventricles. Each has a little ear-shaped appendage termed the auricle Figure 20 2c which helps increase the atrial volume.

10 Coronary Circulation

11 Although the heart is continuously filled with blood, this blood provides little nourishment to heart tissue. The coronary circulation is the functional blood supply of the heart & is the shortest circulation in the body.

12 The right atrium may show a slight groove, the coronary sulcus which divides the atria and ventricles. This groove is the location of the coronary arteries and posteriorly the coronary sinus (vessels of cardiac muscle), and right coronary artery. Figure 20 2c

13 The arterial supply of the coronary circulation is provided by the right and left coronary arteries, both arising from the base of the aorta and encircling the heart in the coronary sulcus. The left coronary artery divides to form the anterior interventricular and left circumflex artery. Figure 20 2c

14 The right coronary artery divides into two branches, the marginal artery and the posterior interventricular artery Complete blockage leads to tissue death and heart attack. Angina pectoris (choked chest) is thoracic pain caused by a fleeting deficiency in blood delivery to the myocardium. Figure 20 2c

15 How Coronary Heart Disease Develops

16 Coronary Artery Angioplasty

17 After passing through the capillary beds of the myocardium, the venous blood is collected by the cardiac veins, whose paths roughly follow those of the coronary arteries. These veins join together to form an enlarged vessel called the coronary sinus, which empties the blood into the right atrium. Figure 20 2c

18 The sinus has three large tributaries: the great cardiac vein, in the anterior interventricular sulcus; and the small cardiac vein, running along the heart s right inferior margin. Additionally, several anterior cardiac veins empty directly into the right atrium anteriorly. Figure 20 2c

19 The Right Atria

20 Blood enters the right atrium via 3 veins, the superior and inferior vena cava and the coronary sinus. Figure 20 2c

21 The posterior region of the right atrium have smooth LOOKING muscle, but the anterior portion has pectinate muscles (pectin = comb) which contain prominent muscular ridges on the anterior atrial wall and inner surfaces of the right auricle.

22 The right atrium shows the Foramen ovale. Before birth, it is an opening through the interatrial septum that connects the two atria. This seals off at birth, forming the fossa ovalis.

23 AV Valves

24 Atrioventricular (AV) valves connects the right atrium to right ventricle and left atrium to left ventricle Each atrioventricular valve has cusps that are attached to a fibrous ring around the opening The fibrous flaps that form tricuspid (3 valves, right side) & bicuspid (2 valves, left side) valves Valves allow blood flow in one direction.

25 Atrioventricular (AV) valves: When Blood pressure increases it closes the valve cusps during ventricular contraction, the papillary muscles tense the chordae tendineae, (heart strings), which prevents the valves from swinging into the atria.

26 AV Valve Function

27 (a) The AV valves open when the blood pressure exerted on their atrial side is greater than that exerted on their ventricular side.

28 (b) The valves are forced closed when the ventricles contract & interventricular pressure rises, moving the contained blood superiorly. Papillary m. & chordae tendineae keeps the valve flaps closed.

29 Mitral (bicuspid) Left AV Valve

30 Semilunar Valves

31 The semilunar valves (SL) guard the bases of the large arteries coming from the ventricles (aorta & pulmonary trunk) & prevent back flow into the associated ventricles. Each SL valve is fashioned from 3 pocket-like cusps shaped roughly like a crescent moon. The SL valves open & close in response to differences in pressure.

32 Semilunar Valve Function

33 (a) During ventricular contraction, the valves are open. (b) When the ventricles relax, the back flowing blood closes the valves.

34 Ventricular Differences

35 The left ventricle holds same volume as right the ventricle, but is larger & the muscle is thicker and more powerful Similar internally to right ventricle but does not have moderator band Right ventricle wall is thinner, develops less pressure than left ventricle. Right ventricle is pouch-shaped, left ventricle is round.

36 One Heartbeat

37 The ability of cardiac muscle to depolarize and contract is intrinsic; that is, it is a property of heart muscle and does not depend on the n. system. Even if all n. connections to the heart are severed, the heart continues to beat rhythmically, as demonstrated by transplanted hearts. The heart is supplied with autonomic n. fibers that can alter the rhythm of the heart.

38 A cardiac cycle consists of the events occurring during one heartbeat. At a normal heart rate of beats/min, a cardiac cycle lasts 0.8 seconds. Normal heart sounds arise chiefly from turbulent blood flow during the closing of heart valves. Systole = contraction of the ventricles (atria relax) Diastole = relaxation of ventricles (atria contract)

39 The right and left ventricles contract causing the semilunar valves to open and the AV valves to close = LUB (first heart sound, S1)

40 The right atrium contracts and blood is pushed into the right ventricle at the same time, the left atrium contracts and blood is pushed into the left ventricle. The AV valves must be open. As blood in the pulmonary and aorta moves backward it causes the semilunar valves to close = DUB (Second heart sound, S2).

41 Between S1 and S2 = systole, blood is going out into the whole body. Between S2 and S1 = diastole, blood refilling from atrium to ventricles.

42 Normal Heart Sounds

43 Review