Blood vessels have the job of carrying blood to the various parts of the body that needs them. The three main varieties of blood vessel are, arteries, veins and capillaries. Arteries, veins and capillaries vary greatly in size, length and thickness from person.
Arteries carry blood away from the hart, they have the highest blood pressure and amount of oxygen. (except for pulmonary arteries)
Capillaries carry blood from arteries to veins. They are a single cell wide and exchange chemicals with nearby tissue.
Veins carry blood towards the heart, and have the lowest amount of oxygen. (except for pulmonary veins)
arteries-carry blood away from the heart
veins- carry blood to the heart
capillaries- connect arteries and veins and deliver oxygen to the cells
compare the kinds of blood vessels according to the thickness of the walls
Capillaries are the smallest blood vessels in the body (in terms of diameter), measuring about 20 micrometres (or one cell) across.
The differences in size has to do with the function of the vessels; where they came from and where they are going.
describe and explain the relationship between the diameter of vessels and the velocity of blood
In different parts of the body the blood vessels are of different diameters. The normal diameter of the aorta is around 2 cm and this would be the largest vessel in the human body, while the smallest, a capillary would be between 0.5 to 2.28 mm in diameter.
Capillary
The smallest blood vessels are the capillaries.
The size of blood vessels varies enormously, from a diameter of about 25 mm (1 inch) in the aorta to only 8 Ξm in the capillaries.
Closed circulatory systems have the blood closed at all times within vessels of different size and wall thickness. In this type of system, blood is pumped by a heart through vessels, and does not normally fill body cavities.
An arteriogenesis is an increase in the diameter of existing arterial vessels.
Blood vessels can feel the shear stress caused by blood flow. When shear stress increases the blood vessel responds and the diameter becomes larger. Thus in short, changes in blood flow might cause blood vessels to change diameter.
Thickness of the walls.