The vessels through which blood travels from the heart to different parts of the body and back to the heart from different parts of the body are called blood vessels. There are three types of blood vessels. Arteries, veins and capillary network.
1. Artery: The blood vessels that carry O2-rich blood from the heart to different parts of the body are called arteries. Arteriosclerosis is the hardening and loss of elasticity of the artery walls. In arteriosclerosis, calcium and cholesterol accumulate in the artery walls and the amount of fibrous tissue increases. Arteriosclerosis is the narrowing of the lumen of arteries and arterioles. Arteriosclerosis is caused by accumulation of fatty substances or cholesterol in the cavities of arteries and arterioles. Atherosclerotic plaque is the accumulation of fatty material caused by arteriosclerosis.
Arterial properties
(i) Arterial wall is thick, strong and elastic
(ii) Its wall is divided into three layers. Tunica externa, tunica media and tunica intima.
(iii) It originates from the heart
(iv) Their lumen or cavity is small
(v) It does not contain kapatika
(vi) Arteries carry blood at high blood pressure
(vii) It carries O2 rich blood.
2. Veins: The blood vessels through which CO2-rich blood reaches the heart from different parts of the body are called veins.
Vein characteristics
(i) Vein wall is thin and inelastic
(ii) Its wall is divided into three layers. Tunica externa, tunica media and tunica intima.
(iii) It originates from body cells
(iv) Their lumen or cavity is large
(v) It contains kapatika
(vi) Arteries carry blood at low blood pressure.
(vii) It carries blood containing CO2
3. Capillaries: The microscopic blood vessels arranged in a network at the junction of arteries and veins are called capillaries. The capillary wall is composed of flattened endothelial cells. The wall is covered by a sheath made of collagen and reticular fibers. This is called the basal lamina. The capillary network carries blood from the aorta to the venules. The capillary network adjacent to the aorta is called the arteriole and the capillary network adjacent to the vena cava is called the venous network. Exchange of nutrients, respiratory air, excreta etc. takes place through capillaries.
Vasa vasorum are the fine blood vessels that supply nutrients to the walls of large arteries and veins.