Blood Volume

There is an average of 5 liters of blood in a healthy adult. Men usually have more blood than women but during pregnancy, a woman’s blood volume can increase by 50% (Sharma et al., 2021). Blood volume is regulated by how much sodium and water we intake and how much we excrete (CV Physiology, n.d.). We excrete water and sodium through our kidneys but we can also lose them through our GI tract, skin, and lungs. If our blood volume were to decrease by 5 to 10 percent so would our blood pressure (Betts, 2013). ADH is then released from our pituitary gland. The release of this hormone causes vasoconstriction which helps raise our blood pressure back up. To help restore blood volume this hormone also stimulates aquaporin channels in our kidneys to help restore the volume of water. When blood return to the atria is too elevated cells in the atrial wall secrete ANH (Patton et al., 2011). ANH is called atrial natriuretic hormone. This decreases our blood volume by increasing sodium excretion in the kidneys. When this is stimulated water is also excreted by the kidneys due to the rule of osmosis. The opposite of this would be when the kidneys stop water loss by reabsorbing it from the urine when the antidiuretic hormone is secreted. If there is more antidiuretic hormone present then there is less water excreted from the body which in turn causes an increase in total blood volume. What are two disorders that can affect our total blood volume?