CBSE Class 10 Answered

sir can u tell me what are the differences between arteries veins and capillaries?

Asked by | 02 Sep, 2011, 03:56: PM

Expert Answer

Structure

Functions

Arteries :The walls (outer structure) of arteries contain smooth muscle fibre that contract and relax under the instructions of the sympathetic nervous system.

	Transport blood away from the heart;
	Transport oxygenated blood only (except in the case of the pulmonary artery).

Capillaries : These are tiny (extremely narrow) blood vessels, of approximately 5-20 micro-metres diameter.
There are networks of capillaries in most of the organs and tissues of the body. These capillaries are supplied with blood by arterioles and drained by venules.

Capillary walls are only one cell thick which permits exchanges of material between the contents of the capillary and the surrounding tissue.

`	Function is to supply tissues with components of, and carried by, the blood, and also to remove waste from the surrounding cells ... as opposed to simply moving the blood around the body (in the case of other blood vessels);
	Exchange of oxygen, carbon dioxide, water, salts, etc., between the blood and the surrounding body tissues.

Veins: The walls (outer structure) of veins consist of three layers of tissues that are thinner and less elastic than the corresponding layers of aerteries.
Veins include valves that aid the return of blood to the heart by preventing blood from flowing in the reverse direction.

	Transport blood towards the heart;
	Transport deoxygenated blood only (except in the case of the pulmonary vein).

Arteries		Veins
Transport blood away from the heart;		Transport blood towards the heart;
Carry oxygenated blood (except in the case of the Pulmonary Artery);		Carry de-oxygenated Blood (except in the case of the Pulmonary Vein);
Have relatively narrow lumens		Have relatively wide lumens
Have relatively more muscle/elastic tissue;		Have relatively less muscle/elastic tissue;
Transports blood under higher pressure (than veins);		Transports blood under lower pressure (than arteries);
Do not have valves (except for those of the pulmonary artery and the aorta).		Have valves throughout the main veins of the body. These prevent blood flowing in the wrong direction