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Blood vessels carry nutrients and oxygen throughout the body and aid in gas exchange.
List the functions of blood vessels
Systemic and pulmonary circulatory systems efficiently deliver oxygen to the tissues of the body and remove waste products such as carbon dioxide.Arterial blood (except the pulmonary artery) is highly saturated with oxygen, supplying oxygen to the body's tissues.
Venus blood (except the pulmonary vein) is de-oxygenated and is returned to the heart to be pumped into the lungs for re-oxygenation.
Nutrients carried in the blood are released to tissues via the permeable endothelium of blood vessels.
Immune cells circulate throughout the circulatory system and are able to rapidly permeate the walls of the blood vessel to attend sites of injury or infection.
Blood vessels can increase or decrease blood flow near the surface of the body either increasing or reducing the amount of heat lost from the body as a means of regulating body temperature.
Blood plays many key roles such as delivering nutrients and chemicals to tissues and removing waste products as well as maintaining homoeostasis and health. The circulatory system is key in transporting blood around the body to perform these actions which is facilitated by the network of blood vessels distributed throughout the body.
The circulatory system can be split into two sections, systemic and pulmonary. In the systemic circulatory system highly oxygenated blood (95-100%) is pumped from the left ventricle of the heart and into the arteries of the body. Upon reaching the capillary networks gas exchange between the tissue and blood can occur, facilitated by the narrow walls of the capillaries. Oxygen is released from the blood into the tissues and carbon dixoide, a waste product of respiration, is absorbed. The capillaries merge into venules and then veins carrying blood the de-oxygenated blood (~75%) back to the right atrium of the heart, at the end of the systemic circulatory system.
The much smaller pulmonary system serves to re-oxygenate the blood and facilitated the removal of carbon dioxide from the blood. Leaving the heart through right ventricle the blood passes through the pulmonary artery, the only artery in the body that contains de-oxygenated blood, and into the capillary network within the lungs. Here the close association of the thin walled alveoae with the equally thin walled capillaries allows for the rapid release of carbon dixoide and uptake of oxygen. Leaving the lungs through the pulmonary vein, again the only vein which carries oxygenated blood in the body, the blood enters the left atrium completing the pulmonary circulatory system.
Blood vessels also facilitate the rapid distribution and efficient transport into the tissue of other factors such as glucose, amino acids or lipids and the removal of waste products for processing elsewhere such as lactic acid to the liver or urea to the kidneys. Additionally, blood vessels provide the ideal network for immune system surveillance and distribution. Numerous white blood cells circulate around the body sensing for infection or injury. Once detected they are able to rapidly leave the circulatory system passing through gaps in the vessel walls to reach the area, whilst signalling for a larger targeted immune response.
Mechanically the blood vessels, especially those near the skin can play a key role in thermo-regulation. Blood vessels can swell to allow greater blood flow, allowing for greater radiant heat loss. Conversely, blood flow through these vessels can be reduced to reduce heat loss in colder climates.