Blood is composed of blood cells suspended in blood plasma. Vertebrate blood is bright red when its hemoglobin is oxygenated and dark red when it is deoxygenated. Some animals, such as crustaceans and mollusks, use hemocyanin to carry oxygen, instead of hemoglobin. Jawed vertebrates have an adaptive blood mandarin system, based largely on white blood cells.

White blood cells help to resist infections and parasites. Platelets are important in the clotting of blood. Blood is circulated around the body through blood vessels by the pumping action of the heart. You can help by adding to it. Left tube: after standing, the RBCs have settled at the bottom of the tube.

Red blood cells contain the blood’s hemoglobin and distribute oxygen. The blood plasma volume totals of 2. The term serum refers to plasma from which the clotting proteins have been removed. Most of the proteins remaining are albumin and immunoglobulins.

Blood pH is regulated to stay within the narrow range of 7. Extra-cellular fluid in blood that has a pH below 7. Human blood is typical of that of mammals, although the precise details concerning cell numbers, size, protein structure, and so on, vary somewhat between species. Red blood cells of non-mammalian vertebrates are flattened and ovoid in form, and retain their cell nuclei. Additional return flow may be generated by the movement of skeletal muscles, which can compress veins and push blood through the valves in veins toward the right atrium. The blood circulation was famously described by William Harvey in 1628.

Healthy erythrocytes have a plasma life of about 120 days before they are degraded by the spleen, and the Kupffer cells in the liver. The liver also clears some proteins, lipids, and amino acids. The kidney actively secretes waste products into the urine. CO2 is carried in blood in three different ways. Hemoglobin, the main oxygen-carrying molecule in red blood cells, carries both oxygen and carbon dioxide. However, the CO2 bound to hemoglobin does not bind to the same site as oxygen.

Instead, it combines with the N-terminal groups on the four globin chains. Some oxyhemoglobin loses oxygen and becomes deoxyhemoglobin. Deoxyhemoglobin binds most of the hydrogen ions as it has a much greater affinity for more hydrogen than does oxyhemoglobin. In mammals, blood is in equilibrium with lymph, which is continuously formed in tissues from blood by capillary ultrafiltration. Lymph is collected by a system of small lymphatic vessels and directed to the thoracic duct, which drains into the left subclavian vein, where lymph rejoins the systemic blood circulation. Blood circulation transports heat throughout the body, and adjustments to this flow are an important part of thermoregulation. Rate of blood flow varies greatly between different organs.