2. THE HEART:-
• The heart is muscular hollow organ that pumps blood in order for it to circulate throughout
the body.
• Located in the thoracic cavity in the mediastinum between the lungs. Lies obliquely, little
more to the left than the right.
• About 12 cm long, 9cm wide at its broadest point
and 6 cm thick.
• Size is about of a person’s fist.
• Weighs about 300 grams in an adult.
5. * COVERING OF THE HEART :
• The heart is surrounded by double walled sac ‘pericardium’.
1} The outer sac :- composed of fibrous tissue. That prevents over distension of the heart.
2} The inner sac :- composed of double layer of serous membrane.
• Serous membrane:
• Outer Layer : parietal layer
-lines the internal surface of fibrous
Pericardium.
• Inner layer : visceral layer or epicardium.
-lines the surface of the heart.
• Between the 2 layers of serous membrane, pericardial
cavity is present which contain pericardial fluid.
• This fluid allows smooth movement between these 2 layers
when the heart beats.
6. * HEART WALL :
*EPICARDIUM:
• Outermost layer of the heart wall formed by the visceral layer of serous
pericardium.
• Composed of connective tissue and simple squamous epithelial cell
7. * MYOCARDIUM :
• Middle layer of the heart wall.
• Composed of cardiac muscle tissue found only in the heart which enables
heart contractions.
• Thickest layer of all three heart wall layers .
• Thickest at the apex and thins out towards the base and thickest in the left
ventricle.
8. * ENDOCARDIUM :
• Innermost layer of the heart wall.
• It is thin , smooth, glistening membrane which permits smooth flow of blood
inside the heart.
• Forms the lining of heart chambers and heart valves.
• Consist of loose connective tissue and simple squamous epithelium tissue which
continuous with the endothelium that lines the blood vessels.
9. * HEART CHAMBERS :
• The heart is devided into right and
left side by muscular walls called
septum.
• Each side is devided into upper
chamber the atrium and lower
chamber the ventricle by
antrioventricular valves.
• 4 Chambers:
• 2 atria
• 2 ventricles
10. ATRIA OF THE HEART
LEFT ATRIUM
• Receives oxygenated blood from the
lungs through :
•pulmonary vein
RIGHT ATRIUM
• Receives Deoxygenated blood from the
body through :
•superior vena cava
•inferior vena cava
• Receiving chamber of the heart.
• Seperated by interatrial septum.
• Foramen ovale – opening in interatrial septum in fetus.
• Fossa ovalis – remnant of foramen ovale.
• Pump blood into ventricle.
11. VENTRICLES OF THE HEART
LEFT VENTRICLE :
• Pumps blood into aorta.
• Thicker myocardium due to greater
work load.
• Systemic circulation supplied by left
ventricle is a higher pressure system
and thus requires more forceful
contraction.
RIGHT VENTRICLE :
• Pumps blood into the pulmonary trunk.
• Pulmonary circulation supplied by right
ventricle is a much low pressure system
Requiring less energy output by
ventricle.
• Ventricles are the discharging chambers of the heart.
• Have little projections of myocardium covered with endothelium, called Papillary
muscles.
• Separated by an Interventricular septum.
12. * HEART VALVES :
• Heart valves ensure unidirectional blood flow through the heart.
• Composed of an endocardium with a connective tissue core.
*Two major types :
1. Antrioventricular valves
2. Semilunar valves
* Antrioventricular valve
• Lie between atria and ventricle.
• Prevent backflow of blood into atria.
• Chordae tendineae – fine, white, connective tissue cords attach cusps of AV valves
to Papillary muscles of ventricle valves.( prevent prolapse of valve back into
atrium)
13. ANTRIOVENTRICULAR VALVES
* TRICUSPID VALVE
• Right antrioventricular valve.
• Has three triangular cusps.
* BICUSPID VALVE
• Left antrioventricular valve
• Also called mitral valve
• Has two triangular valves .
14. SEMILUNAR VALVES
• Semilunar valves prevent backflow of blood into the ventricles .
• Have no chordae tendineae attachment.
• 2 semilunar valves:
1) Aortic semilunar valve:
•lies between the left ventricle and the aorta .
• has 3 cusps.
2) pulmonary semilunar valve:
• lies between the right ventricle and
pulmonary trunk.
• has 3 cusps
• Heart Sounds (lub-dub) due to valves closing.
- ”Lub” – closing of antrioventricular valves
- “Dub”- closing of semilunar valves
