Functions of the Circulatory System
There are three primary responsibilities relegated to the cardiovascular system: conveyance of substances, defense against foreign bodies, and homeostatic regulation.
The Cardiovascular Pump
The human heart contains four chambers and acts as a sort of double-pump, the left and right sides each operating as a seperate pump. Each of these sides are divided by a thick wall of tissue called the septum.
De-oxygenated blood from the veins enters the right side of the heart where it is then pumped into the lungs for oxygenation. The blood from the lungs that has been oxygenated enters the left side of the heart where it is then pumped into the arteries to be transported throughout the tissues of the body. Every single beat of the heart is in actuality the simultaneous contracting of both sides of the heart, demonstrating the extreme efficiency of this vital organ.
Blood Pressure Regulation
There are quite a few way in which the circulatory system can regulate blood pressure. Autonomic nerve impulses from the brain together with specific hormones influence how fast and strong the heart contracts. An increase of force during contraction and higher heart rate results in a rise in blood pressure.
Changes in the blood vessels can also cause blood pressure variations. Vasoconstriction happens when an artery’s diameter decreases due to contraction of the smooth muscle of it’s wall. One example of when this happens is during the sympathetic “fight or flight” response of the autonomic nervous system, resulting in an increase of blood pressure and a decrease in the flow of blood in the constricted area.
Vasodilation is an artery expands as the smooth muscle it’s wall relaxes after the sympathetic response subsides or as result of specific hormones or chemicals in the blood.
Blood pressure can also be affected by the volume of blood in the body. A greater amount of blood increases blood pressure by boosting the volume of blood pumped during each heart beat.
The platelets are responsible for hemostasis, which is the clotting of blood and development of scabs. Platelets usually remain inactive in the blood unless they come into contact with injured tissue or bleed out of the blood vessels as the result of a wound. When platelets become active, they morph into a spiny ball-like shape which enables them to attach to injured tissues.
At that point, the platelets will begin emitting chemical clotting factors, then initialize the production of protein fibrin to serve as a foundation for the blood clot. They will also start clumping together in order to create a platelet plug. A platelet plug acts as a provisional seal to maintain blood in the vessel, at the same time stopping foreign substances from entering until the damage to the wall of the blood vessel can be repaired by it’s cells.