Tissues such as skeletal muscle, liver, and kidney have extensive capillary networks because they are metabolically active and require an abundant supply of oxygen and nutrients. The primary function of capillaries is the exchange of materials between the blood and tissue cells.Ĭapillary distribution varies with the metabolic activity of body tissues. CapillariesĬapillaries, the smallest and most numerous of the blood vessels, form the connection between the vessels that carry blood away from the heart (arteries) and the vessels that return blood to the heart (veins). The connective tissue in this layer is quite dense where it is adjacent to the tunic media, but it changes to loose connective tissue near the periphery of the vessel. This layer is connective tissue with varying amounts of elastic and collagenous fibers. The outermost layer, which attaches the vessel to the surrounding tissue, is the tunica externa or tunica adventitia. It not only provides support for the vessel but also changes vessel diameter to regulate blood flow and blood pressure. The middle layer, the tunica media, is primarily smooth muscle and is usually the thickest layer. The innermost layer, the tunica intima (also called tunica interna), is simple squamous epithelium surrounded by a connective tissue basement membrane with elastic fibers. The wall of an artery consists of three layers. About 10 percent of the total blood volume is in the systemic arterial system at any given time. The arterioles play a key role in regulating blood flow into the tissue capillaries.
Blood is pumped from the ventricles into large elastic arteries that branch repeatedly into smaller and smaller arteries until the branching results in microscopic arteries called arterioles. Systemic arteries transport oxygenated blood from the left ventricle to the body tissues. Pulmonary arteries transport blood that has a low oxygen content from the right ventricle to the lungs. ArteriesĪrteries carry blood away from the heart. Based on their structure and function, blood vessels are classified as either arteries, capillaries, or veins. The other system, the systemic vessels, carries blood from the left ventricle to the tissues in all parts of the body and then returns the blood to the right atrium. One system, the pulmonary vessels, transports blood from the right ventricle to the lungs and back to the left atrium. The vessels make up two closed systems of tubes that begin and end at the heart. Pulmonary circulation: Pulmonary circulation is the half of the cardiovascular system that carries oxygen-depleted blood away from the heart to the lungs and returns oxygenated blood back to the heart.Acknowledgements Classification & Structure of Blood Vesselsīlood vessels are the channels or conduits through which blood is distributed to body tissues.
The systemic circulatory system circulates oxygenated blood from the heart around the body into the tissues before returning deoxygenated blood to the heart. The pulmonary circulatory system circulates deoxygenated blood from the heart to the lungs via the pulmonary artery and returns it to the heart via the pulmonary vein. It supplies the tissues with their nutritional requirements and removes waste products. The circulatory system is the continuous system of tubes through which the blood is pumped around the body. pressure: The force which overcomes resistance to maintain blood flow throughout the body.resistance: The resistance which must be overcome by pressure to maintain blood flow throughout the body.vasoconstriction: The closing or tightening of a blood vessel.flow: The movement of blood around the body, closely controlled by alterations in resistance and pressure.vasodilation: The opening of a blood vessel.
0 kommentar(er)
