Anatomy of the Heart

1. Anatomy of the Heart Part 2

2. Atria Atria • Low pressure chambers • Separated from each other by the inter-atrial septum • RA receives deoxygenated blood from the SVC, IVC and CS • LA receives oxygenated blood from the 4 pulmonary veins.

3. Atria Atria • Atria serves as conduit – 70% of blood flows directly through the atria into the ventricles before the atria contracts. • Atrial contraction contributes the remaining 30%.

4. Ventricles • Pump blood to the lungs and systemic circulation. • Interventricular septum separates the right and left ventricles. • Externally this septum correspond to a groove, the interventricular sulcus which anatomically divided into the anterior and posterior interventricular sulci.

5. Ventricles

6. Ventricles • Larger and thicker than atria • LV is a high pressure chamber • The capacity of each ventricles is approximately 150 ml.

7. Layers of the Heart • Epicardium • Myocardium • Endocardium

8. Layers of the Heart Epicardium • External layer of the heart. • The coronary arteries, blood and lymph vessels, nerve fibers and fat are found in this layer.

9. Layers of the Heart Myocardium • Middle and thickest layer of the heart. • Responsible for contraction of the heart • Muscle fibers of the myocardium are separated by connective tissue supplied by blood vessels and nerve fibers.

10. Layers of the Heart Endocardium • Thin, smooth layer of epithelium and connective tissue. • Lines the heart’s inner chambers, chordae tendineae, valves and papillary muscles • Continuous with the innermost layer of the arteries, veins and capillaries of the body.

11. Layers of the Heart Pericardium • Double walled sac. • Encloses heart and protects from trauma and infection.

12. Layers of the Heart Fibrous Pericardium • Rough outer layer of the pericardium is called the fibrous pericardium. • Continuous with outer wall of the great vessels • Blends with the fascia of the diaphragm.

13. Layers of the Heart Serous Pericardium • Consists of two layers • Parietal layer which lines the inside of the fibrous pericardium. • Visceral layer adheres to the outside of the heart. • Visceral layer = epicardium

14. Pericardium

15. Consist of many muscle cells (myocytes) Each muscle cell is enclosed in a membrane called a sarcolemma. Each cells contains hundreds of long, tubule like structures called myofibrils Cardiac Muscle

16. Cardiac Muscle • Each myofibril consist of many sarcromeres • Each sarcromere consist of two types of proteins: actin and myosin.

17. Cardiac Muscle Cardiac Muscle Myocyte Myofibrils Sacromeres Actin & Myosin

18. Cardiac Muscle

19. Cardiac Muscle

20. Cardiac Muscle Actin Myofibril Contains two proteins: • Tropomyosin • Troponin These two proteins inhibit the formation of cross bridges with myosin.

21. Cardiac Muscle When cross bridge formation is inhibited the muscle is relaxed.

22. Cardiac Muscle Each muscle cell is surrounded by a cell membrane called the sarcolemma. Each muscle fibers contain T tubules that are extensions of the cell membrane. Another system of tubules called the sarcoplasmic reticulum stores calcium.

23. Cardiac Muscle Calcium enters the cytoplasm from: • The interstitial fluid via the T tubules • Sarcroplasmic reticulum

24. Cardiac Muscle Cardiac Muscle Fibers • Consist of long branching cells • The cells fit together tightly at junctions • These junctions are called intercalated disc.

25. Cardiac Muscle • These tight-fitting junctions gives an appearance of a syncytium. • Intercalated disc fit together in such a way to form permeable gap junctions.

26. Cardiac Muscle • This gap junction function as electrical connections. • These connections join the muscle fibers into a single unit.

27. Cardiac Muscle • This allows for rapid conduction of an impulse throughout the wall of a cardiac chamber. • This results in the wall of both atria (and both ventricle) to contract almost simultaneously.

28. Cardiac Muscle The heart consist of two syncytia: • Atrial Syncytium • Right atrial wall • Left atrial wall • Ventricular Syncytium • Right ventricular wall • Left ventricular wall

29. Cardiac Muscle Impulses can only be conducted from the atrial syncytium into ventricular syncytium by means of the atrioventricular junction.

30. Cardiac Muscle Atrial Syncytium Conducting System Ventricular Syncytium

31. Heart Valves • Two atrioventricular valves • Mitral • Tricuspid • Two Semilunar • Aortic • Pulmonic

32. Heart Valves

33. Atrio-ventricular Valve Each atrio-ventricular valve consists of: • Annulus – (tough fibrous rings) • Leaflets • Chordae tendineae • Papillary muscles

34. Atrio-ventricular Valve The base of the leaflets are attached to the fibrous annulus. The tips of the AV valves are attached to thin strands of fibrous tissue called fibrous connective tissue chordae tendineae.

35. Atrio-ventricular Valve The chordae tendineae are attached to small mounds of myocardium called papillary muscle.

36. Tricuspid Valve • Lies between the RA and RV • Consists of 3 leaflets: anterior, posterior and septal. • Opens when the pressure in the RA becomes greater than the pressure in the RV.

37. Tricuspid Valve

38. Tricuspid Valve

39. Mitral Valve • Lies between the LA and LV • Consists of 2 leaflets: anterior and posterior. • Opens when the pressure in the LA becomes greater than the pressure in the LV.

40. Mitral Valve

41. Pulmonic Valves Pulmonic Valve • Lies between the RV and Main Pulmonary artery. • Consists of 3 cusps. • The Pulmonic Valve opens when the pressure in the RV becomes greater than the pressure in the Pulmonic Artery.

42. Pulmonic Valves

43. Aortic Valves Aortic Valve • Lies between the LV and Aorta • Consists of 3 cusps. • The Aortic Valve opens when the pressure in the LV becomes greater than the pressure in the Aorta.

44. Heart Valves

45. Heart Valves