Circulatory System In Humans.

There are two types of fluids which runs through the circulatory system namely blood and lymph. The blood, heart and blood vessels form the cardiovascular system. The lymph, lymph nodes, and lymph vessels form the lymphatic system. The cardiovascular system and the lymphatic system collectively make up the circulatory system.

This system is required because the human body is multi cellular band has a small surface area to volume ratio. Diffusion alone is far too slow a process for adequate distribution of oxygen and dissolved food substances to cells and the removal of waste from cells.

The Structure And Functions Of The Blood Circulatory System In Humans : The humans circulatory system is also refers to as the cardiovascular system. The blood circulatory system in humans consists of the blood, the blood vessels and the heart. The heart is the organ that controls the circulation of the blood in the body. The heart is a hollow and muscular organ which lies in the chest or between the two lungs. It is protected by muscles of the chest walls, the ribs, the sternum and the diaphragm. The heart is divided into four chambers namely the left atrium, right atrium, left ventricle and right ventricle. So the parts of a heart include the following: Superior vena cava, inferior vena cava, right atrium, left atrium, semi lunar valves, tricuspid valve, right ventricle, septum, bicuspid valve chordae tendineae, left ventricle, pulmonary artery, pulmonary vein, aorta and semi lunar valves. Let's look at their functions. So the first one is superior vena cava. It returns deoxygenated blood from the head and upper limbs to the heart. The second one is the inferior vena cava. It returns deoxygenated blood from the lower limbs and organs to the heart.

The right atrium receives deoxygenated blood from the vena cava. The semi lunar valves prevent back flow of blood from the pulmonary artery into the right ventricle when the right ventricle relaxes. The tricuspid valve prevent back flow of blood to the right atrium when the right ventricle contracts. The right ventricle pumps blood to the lungs. The septum prevents the mixing of deoxygenated blood in the right side of the heart with the oxygenated blood from the left side of the heart. Now the chordae tendineae tendons become taut and prevent the valve from flapping back into the atrium under the blood pressure generated during the contraction of the ventricles. The left ventricle pumps blood to all parts of the body except the lungs. The left atrium receives oxygenated blood from the lungs via pulmonary vein . Pulmonary artery carries deoxygenated blood to the lungs. Pulmonary vein carries oxygenated blood from the lungs to the left atrium, aorta carries blood to all parts of the body except the lungs and the semi lunar valves prevents backflow of oxygenated blood from the aorta into the left ventricle when the left ventricle relaxes.

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