• Blood Circulation..

Blood circulates continuously in blood vessels in the body. Blood circulating in the body is mainly divided into two parts.

1. Pulmonary Circulation..

Pulmonary circulation started from the right ventricle and blood goes to the lungs and from there returns to the left atrium, so the circulation from the right ventricle to the left atrium is called pulmonary circulation.

In the pulmonary circulation, deoxygenated blood in the right ventricle exits the right ventricle through the pulmonary artery. As it exits, the pulmonary artery divides into a right and a left pulmonary artery and both enter the lung. In which two branches in the left lung and three branches in the right lung enter the pulmonary artery which is according to each lobe of the lung.

In the lungs, gas exchange takes place between the blood and the tissue of the lungs, and two pulmonary veins take oxygenated blood from each lobe and enter the left atrium of the heart from the lungs on both sides.

Pulmonary circulation converts deoxygenated blood in the heart to oxygenated blood via the lungs. This blood enters the left ventricle and supplies oxygenated blood to the whole body through the systemic circulation.

Circulation from right ventricle to left atrium is called pulmonary circulation.

• Systemic or General Circulation…

Systemic circulation starts from the left ventricle of the heart. The left ventricle of the heart contains oxygenated blood that circulates throughout the body through the aorta and supplies oxygenated blood to every cell and tissue through the general circulation.

As the aorta leaves the heart in the systemic circulation, different arteries divide into regions and supply oxygenated blood to different regions.

Aorta…

They are the main vessels of the systemic circulation. It is the largest artery of all the arteries in the body. It circulates oxygenated blood from the left ventricle throughout the body.

The aorta arises from the left ventricle and is further known by different names according to its location. such as ascending aorta, arch of aorta and descending aorta.

Descending aorta after reaching the thoracic and abdominal divides into two right and left common iliac arteries and circulates blood to the lower limb.

In the systemic circulation, the aorta divides into lower branches according to the thoracic and abdominal regions that supply oxygenated blood to that area.

•Thoracic Aorta : This part of the aorta is above the diaphragm and is described in three parts:

1.Ascending Aorta

• Coronary arteries

1. Arch of aorta

•Brachiocephalic artery

• Left common carotid artery
• Left Subclavian artery

1. Descending Aorta in the thorax.

•Brachial arteries

•Oesophageal arteries

•Intercostal arteries

4. Abdominal aorta:

•Inferior Phrenic

•Renal artery

•Testicular Arteries or Ovarian arteries

• Lumbar arteries
• Median sacral arteries

•Coeliac artery

• Left gastric artery
• Common hepatic artery
• Splenic artery

•Superior mesenteric artery

•Inferior mesenteric artery

All the above mentioned arteries complete the systemic circulation and supply oxygenated blood to every organ of the body.

• PORTAL CIRCULATION

Portal circulation is the circulation of blood returning deoxygenated blood to the heart through the portal vein in the body.

In this, deoxygenated blood from the organs below the diaphragm of the body such as small intestine, large intestine, pancreas, liver, gall bladder and stomach is drained through different veins such as gastric vein, cystic vein, superior mesenteric vein, inferior mesenteric vein, etc. It merges into the portal vein.

The portal vein takes this blood and enters the liver along with the hepatic artery. A network of capillaries of these two vessels spreads in the liver and finally, when it exits the liver, it converts into the hepatic vein and from there it mixes with the inferior vena cava and brings deoxygenated blood to the right atrium of the heart.

Blood coming from the body’s intestines is highly nutritious. Absorption of nutrition takes place through the liver and the liver distributes this nutrition to every part of the body.

This circulation is called portal circulation because the blood drains mainly through the portal vein.

• CIRCLE OF WILLS

Oxygenated blood is supplied to the brain through this circulation.
To supply blood to the brain, many arteries connect at the lower part of the brain to form a circle and through all these arteries oxygenated blood is supplied to the brain, hence this is called the circle of Wills.

The brain is an important organ so that all these arteries connect to each other by anastomosis. So, if the blood supply is interrupted through any one branch, the blood supply can reach the part of the brain through another branch.

The anterior and posterior vertebral arteries from the lower part of the brain at the circle of Wills transform into the basilar arteries as they enter the brain.

The anterior cerebral artery from the front of the brain and the posterior cerebral artery from the back of the brain and the internal carotid artery are located between the brain. There are anterior and posterior communicating arteries connecting the front and back of the brain. All these arteries join together to form a circle-like structure at the base of the brain. Oxygenated blood is supplied to the brain through all these arteries.

• CORONARY CIRCULATION

Oxygenated blood supply to the heart to function As soon as the aorta exits the left ventricle of the heart, it branches off into the right and left coronary arteries, which supply oxygenated blood to the heart. These coronary arteries are branches of the ascending aorta.

About five percent of the blood that the heart circulates out of the aorta during a contraction is supplied to the heart through the coronary arteries.

These coronary arteries divide into many branches and supply oxygenated blood to all parts of the heart.

The deoxygenated blood in the heart collects the small coronary veins and drains the deoxygenated blood into the coronary sinuses, and through the coronary sinuses, all the blood drains directly into the right atrium of the heart.