Circulatory System

Circulatory system

It is a transport system to supply the useful material and to remove the wastes from the body cells.

Heart

Heart is a thick muscular,contractile automatic pumping organ of blood vascular system.The chamber which receive s 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)or pacemaker.
When SA node becomes defective,i.e.,it does not generate cardiac impulse ,it can be cured by surgical grafting of an artificial pacemaker(an electric device) in the chest of the patient.It stimulate the heart electrically at regular intervals.

Blood Vessels

Blood vessels are of three types.
1.Arteries : These carry the blood away from the heart to various body parts.These carry oxygeneted(pure) blood in them.except the pulmonary artery which carries de-oxygenated blood to the lungs.
2.Veins : These carry blood away from various body aparts of the heart.These carry de-oxygenated blood in them except the pulmonary vein which carries oxygenated blood to the heart.
3.Capillaries : These are the thinnest blood vessels and connect arteries to the veins.These help in exchange of materials like the nutrients,gases waste products etc.Beyween blood and cells.
Blood : Blood is fluid connective tissue and composed of blood corpuscles,Plasma and plateletes.It is slightly alkaline in nature (pH7.4)Itas volume in an adult in 5.8 L.