The Heart, Arteries & Veins Forms the Circulatory System:
The heart pumps blood into arteries. The arteries divide and subdivide and finally end in capillaries. The capillaries later unite to form veins. The veins return blood to the heart. The arteries carry pure blood away from the heart, Veins carry De-oxygenated blood to the heart and the capillaries are minute channels receives blood from smaller arteries (arterioles) and deliver into smaller veins (venules).
Blood circulation: depending on the course of blood. Circulation can be classified into:
- Systemic circulation.
- Pulmonary circulation
- Coronary circulation
- Portal circulation.
Systemic circulation:
it’s the blood circulation that carries oxygenated blood away from the heart, to the body, and returns deoxygenated blood back to the heart except for lungs. This circulation starts Oxygenated blood enters the left atrium from the pulmonary veins. The blood is then pumped through the mitral valve into the left ventricle. From the left ventricle, blood is pumped through the aortic valve and into the aorta, the body’s largest artery. The aorta arches and branches into major arteries and then it breaks up into smaller arteries and finally ends in capillaries. The capillaries unite to form venules which join up ultimately to form 2 large venous trunks namely superior vena cava and inferior vena cava. These 2 venous trunks open in the right atrium of the heart.
Gas and nutrient exchange with the tissues occurs within the capillaries that run through the tissues. Metabolic waste and carbon dioxide diffuse out of the cell into the blood, while oxygen and glucose in the blood diffuse out of the blood and into the cell. The arterial component of systemic circulation the highest blood pressures in the body. The venous component of systemic circulation has considerably lower blood pressure in comparison, due to their distance from the heart, but contain semi-lunar valves to compensate. Systemic circulation as a whole is a higher pressure system than pulmonary circulation.
Pulmonary circulation:
it involves the purification of blood in lungs. It’s the circulation of the blood from the heart to the lungs for oxygenation, then back to the heart again. The Oxygen-depleted blood from the body leaves the systemic circulation when it enters the right atrium, The blood is then pumped through the tricuspid valve into the right ventricle. From the right ventricle, blood is pumped through the pulmonary valve and into the pulmonary artery. The pulmonary artery splits into the right and left pulmonary arteries and travel to each lung. The oxygenated blood then leaves the lungs through pulmonary veins, which returns it to the left atrium, completing the pulmonary circulation.
Coronary Circulation:
Coronary circulation involves blood supply to the heart itself, it is the circulation of blood in the blood vessels of the heart muscle. The vessels that deliver oxygen-rich blood to the myocardium are known as coronary arteries. The right and left coronary arteries arise from ascending aorta. The vessels that remove the deoxygenated blood from the heart muscle are known as cardiac veins which collect and opens into the right atrium.
Portal circulation:
It’s the circulation of blood through the liver. In this circulation, the portal vein carries blood that has circulated in stomach, intestine, and pancreas to liver. The portal vein divides into capillaries. These capillaries join with the capillaries of the hepatic artery. The venous blood of liver is collected by hepatic vein which joins with inferior vena cava.