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Human Physiology of Heart & Blood
Human Physiology of Heart
- Heart is a thick, muscular, contractile, automatic pumping organ of blood vascular system.
- There is a thin two layered sac around the heart known as pericardium, filled with a watery fluid called pericardial fluid, which allows frictionless movements of heart and protects it from mechanical shocks.
- In crocodile, birds and mammals the heart is divided into four chambers (two auricles and two ventricles).
- Reptilian heart is structurally three-chambered but is functionally four-chambered (ie., incomplete four- chambered) except in crocodile.
- A new born baby’s heart weight about 20 g.
- A fish has only two-chambered heart (one auricle and one ventricle).
- In amphibians, heart is three-chambered.
- The average weight of heart in men is 280-340 g, while in women is 230-280 g.
- To pump out blood, the heart chamber undergo alternate contration called systole and relaxation called diastole. The regular sequence of these systole and diastole causes the heart sound Lub and Dub.
- Arteries carry pure blood from the heart while veins carry impure blood to the heart.
- The chamber which receives the blood from body tissues are called auricles and the chambers of heart which pump blood to body tissues are called ventricles.
- Human heart beat is myogenic in nature, i.e., initiated by a patch of modified heart muscles itself without requiring an external stimulation. This patch is called SA node (sino-auricular node) or pacemaker.
Human Physiology of Blood
- Blood is fluid connective tissue and composed of blood corpuscles, plasma and platelets.
- The oxygenated or pure blood is bright red while the deoxygenated blood in purple coloured (Darker shade of red).
- During blood clotting fibrinogen changes into fibrin by thrombin which is obtained from thromboplastin in the presence of Ca2+.
- It is slightly alkaline is nature (pH 7.4).
- Its volume in an adult in 5.8 L.
- The haemoglobin contents of adult female amount from 13.5 to 14.5% whereas in adult male its amount from 14.5 to 15.5%