BLOOD VESSELS AND THE CIRCULATION:::
Blood circulates all over the body through the blood vessels There are two types of blood vessels Arteries and Veins
Arteries::
arteries are the vessels which carry the blood from the heart to supply it to all parts of the body The blood is usually oxygenated except that of pulmonary arteries which carry deoxygenated or CO2 containing blood the arteries divide and redivide to form small arteries called arterioles these arterioles finally end in capillaries which are single layered thin vessels lying in between the cells
veins::
veins are the vessels which bring the blood from various parts of the body to pour it into the heart The blood is usually deoxygenated except that of pulmonary veins which bring oxygenated blood to the left atrium The veins are formed from smaller veins called venules and venous capillaries
Histologically blood vessels consist of three layers:
1. Tunica externa or external layer(Elastic layers)
2.Tunica media or middle layer(Muscle layer)
3.Tunica intima or internal layer (Serous layer)
Tunica externa is made up of areolar connective tissue it is thicker in veins than in arteries
Tunica media is made up of smooth muscle fibres This layer is thicker in artery than in the vein
Tunica intima is made up of endothelial cells separated from the middle coat by a membrane called the internal elastic lamina
The lumen in vein is generally collapsed while it is usually wide open in artery
The human circulatory system has three divisions systemic circulation pulmonary circulation and coronary circulation
systemic Circulation:::
It is a long circuit that starts from the left ventricle supplies the blood to all the parts of the body except the lungs Blood is finally collected into the right atrium the systemic circulation can be described under the arterial system and the venous system
0 Comments