BLOOD VESSELS -

• Some vessles supply blood to wall of large vessels these are vessel of vessels or vasa vasorum.
• Mainly artery and vein, 2 types of vessels present.
• Third one is capillary - discovered by Marcillo Malpighi, thin, present in organ, only inner layer in wall present.
• In man 10 billion capillaries present.
• They may form 150,000 miles rope.
• In vein blood flows mainly by contraction of body muscles & suction created by diastole of heart.
• In wall of blood vessels 3 layers present.

1. Tunica Externa - Made up of connective tissue, collagen fibres present.

2. Tunica media - Thick, made up of smooth muscles arranged in circular way.

3. Tunica interna - Inner most layer. Outerly made up of yellow elastin fibre. Inner layer is of endothelial cells.