one of the arteries closes during bending of the joints. Capillaries Capillary beds are made up of fine networks of capillaries. The capillaries are thin walled and consist of single layer of squamous epithelium. Tunica media and elastin fibres are absent.
The capillary beds are the site for exchange of materials between blood and tissues. The walls of the capillaries are guarded by semilunar valves. The blood volume in the capillaries is high but the flow of blood is slow. Mixed blood (oxygenated and deoxygenated) is present in the capillaries.
Tunica externa Tunica media Tunica intima Endothelium Tunica externa Tunica media Tunica intima Endothelium Tunica externa Tunica media Tunica intima Endothelium Tunica externa Tunica media Tunica intima Endothelium Tunica externa Endothelium Tunica externa Endothelium Large vein Vein Venule Elastic artery Muscular artery Arteriole Endothelium Capillary Figure . Structure of Blood Vessels XI Std Biology-Zoology Chapter- The capillary bed may be flooded with blood or may be completely bypassed depending on the body conditions in a particular organ. Why there are no blood capillaries in the cornea of the eye and cartilage? How are these regions supplied with the required nutrients?
Suggest why arteries close to the heart have more elastic fibers in their walls than arteries further away from the heart? Veins Veins have thinner walls and a larger lumen and hence can be easily stretched. They carry deoxygenated blood except, the pulmonary vein. The blood pressure is low and the lumen has a wide wall which is collapsible.
Tunica media is thinner in veins than in arteries. Unidirectional flow of blood in veins is due to the presence of semilunar valves that prevents backflow of blood. Blood samples are usually taken from the veins rather than artery because of low pressure in the veins. .
. Coronary Blood Vessels Blood vessels that supply blood to the cardiac muscles with all nutrients and removes wastes are the coronary arteries and veins. Heart muscle is supplied by two arteries namely right and left coronary arteries. These arteries are the first branch of the aorta.
Arteries usually surround