The human body has two circulatory systems: cardiovascular and the lymphatic. Both are responsible for circulating fluids through the body, but while the cardiovascular system circulates blood via a closed system of vessels, lymphatic fluid is not pumped but passively flows from tissues into lymphatic vessels.
The two systems work within tandem to keep body tissues healthy and supplied with nutrients, provide a conduit for elimination of waste products, and keep body fluid contained by the vascular system where it belongs. Both also provide immune function. The cardiovascular system circulates white blood cells which help fight infections. Lymph nodes in the lymph system screen molecules and organisms in the lymph fluid for toxicity and respond to any foreign invaders or toxic compounds.
Here is an explanation of the duties that each of these systems performs.
Cardiovascular system
The cardiovascular system circulates blood carrying oxygen and nutrients to your body’s tissues and eliminating the waste products of cellular metabolism. At the center of the cardiovascular system is the heart, which pumps blood throughout the vascular system of arteries and veins.
Four chambers comprise the heart: the two upper ones, left and right atrium, which receive circulated blood, and two lower ones, left and right ventricle, which pump blood through the body. The wall separating the two ventricles is the interventricular septum; the wall dividing the two atria is interatrial septum.
The right atrium receives blood low in oxygen from all body tissues through the superior vena cava and the inferior vena cava. It then enters the right ventricle where it travels to the lungs through the pulmonary artery to be reoxygenated. Blood returns via the pulmonary vein to enter the left atrium. From here it enters the left ventricle and is pumped into the aorta to be distributed to all tissues. Blood is kept moving in a forward direction by the mitral valve and the tricuspid valve.
Each contraction of the heart is followed by a relaxation phase during which the chambers fill. Each time the heart beats, both atria contract and immediately thereafter both ventricles contract.
From the heart, blood enters the vascular system which consists of large arteries that that carry blood away from the heart, arterioles- or small arteries that lead into the capillaries. The capillaries,the smallest vessels, are where the work is done, with exchanges taking place between the blood and the tissues. Venules, or small veins receive blood from the capillaries and lead to larger veins that carry blood back to the heart.
Some brief facts about the cardiovascular system:
• Responsible for carrying oxygen, nutrients, and hormones to all parts of the body through blood.
• The liquid plasma in blood is what transports red and white blood cells.
• Blood is filtered by the kidneys where excess fluid and waste products are removed.
The Lymphatic System
The two most important roles of the lymphatic system in the circulation are to return excess fluid and the proteins from the tissues to the bloodstream and to provide immunity. Fluid can escape from the blood stream into the body’s tissues due to the effect of hydrostatic forces and oncotic pressure. Lymphatic vessels act as drains to help avoid build-up of fluid prompting it to return to the bloodstream before it reaches the heart.
This system is composed of moving fluid, called lymph, which is derived from tissue and blood and lymphatics, a group of vessels that parallel veins and whose duty it is to return lymph to the blood. Lymph nodes, which filter lymphatic fluid, are located along the paths of the collecting vessels and isolated nodules of lymphatic patches are found in the intestine.
Other functions of the lymphatic system include absorption of digested fats from small intestines and protecting the body from invading microorganisms. Other organs and tissues of the lymphatic system include the tonsils, the thymus and the spleen.
