Circulatory system

The circulatory system or cardiovascular system is an organ system that circulates blood in the body and transport nutrients (electrolytes and amino acids), oxygen, Co2, hormones, and blood cells in the body to provide nourishment and help in fighting diseases, stabilize temperature and pH and maintain the process of homeostasis.

The circulatory system includes the lymphatic system to circulates lymph. The lymph passage takes much longer than the blood. Blood includes plasma, white blood cells, red blood cells, and platelets that is circulated via heart through the vertebrate vascular system, carrying oxygen and nutrients to and keeps away the waste materials from all body tissues.

Lymph is recycled excess blood plasma, the lymph, lymph nodes, and lymph filtered blood plasma from the interstitial fluid (between cells).

The circulatory system of the blood having two components, a systemic circulation and pulmonary circulation. Humans have a closed cardiovascular system like vertebrates have, It means that in humans the blood never leaves the network of arteries, veins and capillaries, but some invertebrate groups are like that they have an open cardiovascular system.

Many diseases affect the circulatory system, the disease can affect both cardiovascular system, and lymphatic system.

Cardiovascular system

Heart, blood and blood vessels are the essential components of human cardiovascular system. It includes the pulmonary circulation and systematic circulation, in pulmonary circulation blood is oxygenated by the loop in the lungs while in the systemic circulation, a "loop" provides oxygenated blood through the rest of the body.

The systemic circulation can function in two parts (macro and micro circulation). An average adult contains roughly 4.7 to 5.7 liters of blood approximately 7% of their total body weight. The digestive system also works with the circulatory system to provide the nutrients to the body to keep the heart pumping.

The cardiovascular systems of humans are closed while the lymphatic system is open, therefore the blood never leaves the blood vessels, only oxygen and nutrients diffuse across the blood vessel and enter in  interstitial fluid, which carries oxygen and nutrients to the target cells and remove carbon dioxide and wastes in the opposite direction.

Arteries

Oxygenated blood enters the circulation when leaving the ventricle, through the aortic heart valve. The primary part of the circulation is that the aorta, a huge and thick-walled artery. The aorta arches start supplying to the upper part of the body after passing through the aortic opening of the diaphragm at the extent of thoracic ten vertebra, it enters the abdomen. Later it descends down and supplies branches to abdomen, pelvis, perineum and then the lower limbs. The walls of aorta are elastic in nature. This elasticity maintains blood pressure throughout the body. When the aorta receives almost five liters of blood from the guts, it recoils and is responsible for pulsating blood pressure.

Capillaries

Arteries branch into small passages called arterioles then into the capillaries. The capillaries combine to bring blood into the venous system.

Veins

Capillaries merge into venules, which merge into veins. The venous system feeds into the 2 major veins: the superior vein – which mainly drains tissues above the guts – and then the inferior vein – which mainly drains tissues below the guts. These two large veins empty into the proper atrium of the guts.

Portal veins

In humans the sole significant example is that the hepatic portal vein which mixes from capillaries around the alimentary canal where the blood absorbs the varied products of digestion; instead of leading directly back to the guts, the hepatic portal vein branches into a second capillary system within the liver.

Heart

The function of the heart is to pumps oxygenated blood to the body and deoxygenated blood to the lungs. In the human heart there is one atrium and one ventricle for every circulation, there are four chambers in total: left and right atrium of the heart, and their ventricles. the proper atrium is that the upper chamber of the right side of the guts. The blood that's returned to the right atrium is deoxygenated (poor in oxygen) and passed into the right ventricle to be pumped through the arteria pulmonary to the lungs for re-oxygenation and removal of CO2. The left atrium of the heart receives newly oxygenated blood from the lungs also because the vena pulmonary which is passed into the strong ventricle to be pumped through the aorta to the various organs of the body.

Coronary vessels

Through a small "loop" of the systemic circulation the heart itself is supplied with oxygen and nutrients and derives very little from the blood contained within the four chambers. The coronary circulation system itself provides a blood supply to the heart muscle. Near the origin of the aorta, the coronary circulation begins by two coronary arteries: the right and left coronary artery. Blood returns through the coronary veins into the coronary sinus and from this one into the right atrium after nourishing the heart muscle. Backflow of blood is prevented by Thebesian valve through its opening during atrial systole. The cardiac veins channel directly into the heart chambers.

Lungs

The pulmonary circulation showing both the arteries pulmonary and bronchial.

Oxygen-depleted blood is pumped away from the heart in the cardiovascular system, via the pulmonary artery to the lungs and return oxygenated blood to the heart via the pulmonary vein.

In the right atrium of the heart oxygen-deprived blood from the superior and inferior vena cava enters and flows through the tricuspid valve (right atrioventricular valve) into the right ventricle, then it is pumped through the pulmonary semilunar valve into the pulmonary artery to the lungs. Gas exchange happens in the lungs, whereby CO2 is released from the blood, and oxygen is absorbed. The pulmonary vein returns the oxygen-rich blood to the left atrium, and process continues.

But there is a separate system which supplies blood to the tissue of the larger airways of the lung known as the bronchial circulation.

Systemic circulation

The systemic circulation and capillary networks are separate from the pulmonary circulation.

It is the portion of the cardiovascular system which transports oxygenated blood away from the heart through the aorta from the left ventricle where the blood has been previously dropped from pulmonary circulation to the rest of the body, and then returns oxygen-depleted blood back to the heart.

Brain

The brain has a dual blood supply at its front and back that comes from arteries known as "anterior circulation" and "posterior circulation”. The anterior circulation arises from the internal carotid arteries and then supplies to the front of the brain. The posterior circulation arises from the vertebral arteries and then supplies to the back of the brain and brainstem. The circulation from the front and the back join together at the Circle of Willis.

Kidneys

In kidney the renal circulation we’ll discuss this circulation receives around 20% of the cardiac output. It divides from the abdominal aorta and returns blood to the ascending vena cava. It contains many specialized blood vessels which supply blood to the kidneys.

Lymphatic system

It is the part of the circulatory system. Which is a network of lymphatic vessels and lymph capillaries, lymph nodes and organs, and lymphatic tissues and circulating lymph.

The main function of the lymphatic system is to carry the lymph, draining and returning interstitial fluid back towards the heart for return to the cardiovascular system, by emptying into the lymphatic ducts. Its other function is in the adaptive immune system.