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 personâs fist.
⢠Weighs about 300 grams in an adult.
5. * COVERING OF THE HEART :
⢠The heart is surrounded by double walled sac âpericardiumâ.
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 :
â˘pulmonary vein
RIGHT ATRIUM
⢠Receives Deoxygenated blood from the
body through :
â˘superior vena cava
â˘inferior vena cava
⢠Receiving chamber of the heart.
⢠Seperated by interatrial septum.
⢠Foramen ovale â opening in interatrial septum in fetus.
⢠Fossa ovalis â 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 â 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:
â˘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.
- âLubâ â closing of antrioventricular valves
- âDubâ- closing of semilunar valves