HSBTE. DMLT. IInd Semester. HAP. Circulation of Blood: Systemic Circulation, Arterial System, Venous System, Portal system,

SYSTEMIC CIRCULATION

Circulation of oxygenated blood from the left ventricle of the heart to a different part of the body and movement of deoxygenated blood from different parts of the body to the right atrium of the heart is called systemic circulation or greater circulation (Except lungs). It consists of Arterial circulation and Venous Circulation.

ARTERIAL SYSTEM:

Arteries to circulate oxygenated blood from the left ventricle of the heart to different parts of the body constitute the arterial system. It consists of the following blood vessels. Two aortas arise from the heart. These are the Pulmonary Aorta and the Systemic Aorta.

A. Pulmonary Aorta: The pulmonary aorta arises from the right ventricle's left upper end. It forms the right pulmonary artery and the left pulmonary artery. The right pulmonary artery supplies deoxygenated blood to the right lung and the left pulmonary to supplies deoxygenated blood to the left lung.

B. Systemic aorta: Systemic aorta arises from the left ventricle right upper end to supply oxygenated blood to different parts of the body. The systemic aorta has three parts. These are the ascending aorta, arch of the aorta, and descending aorta

• 1. Ascending aorta: Two coronary arteries arise from ascending aorta to supply oxygenated blood to cardiac muscles.

• 2. Arch of Aorta: Three arteries arise from the arch of the aorta to supply oxygenated blood to the head and upper extremities. These three arteries are

  • The brachiocephalic artery arises from the right side of the arch of the aorta. It supplies oxygenated blood to different parts of the head such as the neck, mouth, face, eyes, brain, etc.

  • The subclavian artery arises from the left side of the arch of the aorta. It supplies oxygenated blood to the back of the cerebrum, the spinal cord, the neck, the upper limbs, and the superior and anterior of chest wall.

  • Common carotid: Common carotid supplies oxygenated blood to the neck, face, mouth, eye, and brain. Similarly,

• 3. Descending aorta: Some parts of the descending aorta remain in the thoracic cavity and some parts in the abdominal cavity. The following arteries arise from the thoracic part of the descending aorta to supply oxygenated blood as per the below details.

  • · Intercostal artery to intercostal muscles

  • · Brachial artery to lungs

  • · Oesophageal artery to the oesophagus

  • · Superior phrenic artery to diaphragm, superior surface

The following arteries arise from the abdominal part of the descending aorta to supply oxygenated blood as per the below details.

• · Inferior phrenic artery to the diaphragm inferior surface

• · Coeliac artery to GIT, liver, pancreas and spleen

• · Superior mesenteric artery to the small intestine

• · Inferior mesenteric artery to the large intestine

• · Supra renal artery to the adrenal gland

• · Renal artery to the kidney

• · Genital artery to testes/ovaries

• · Lumbar artery to vertebrae, muscle, skin

• · Common iliac artery to left and right pelvic region.

VENOUS SYSTEM:

Veins collect deoxygenated blood from different parts of the body to carry them toward the heart constituting the venous system. The following veins constitute the venous system:

1. Pulmonary vein: Two pulmonary veins carry oxygenated blood from the lungs to the left atrium. These are the right pulmonary vein from the right lung and the left pulmonary vein from the left lung.

2. Coronary Sinus: Coronary sinus from cardiac muscles carry deoxygenated blood into the right atrium.

3. Superior Vena cava: The superior vena cava is formed by the union of two brachiocephalic veins. Brachiocephalic veins are formed by the union of the Jugular vein, subclavian vein, and internal thoracic vein. These veins carry deoxygenated blood. to superior vena cava. The superior vena cava pours deoxygenated blood into the right atrium. These veins carry deoxygenated blood from different parts of the body.

• a. Jugular vein (Internal and external jugular vein) from head and neck,

• b. Subclavian vein (right and left subclavian) from upper limb,

• c. Internal thoracic vein from the chest, Internal thoracic vein from the left side and right side unite

4. Inferior Vena cava: Inferior vena cava collects deoxygenated blood from the lower limbs and pelvic region. The following veins carry deoxygenated blood from different parts of the body to the inferior vena cava.

• a. Right iliac vein: Right lower limb and right pelvic region

• b. Left iliac vein: left lower limb and left pelvic region,

The right iliac vein and left iliac vein unite to form a common iliac vein. It opens into inferior vena cava.

• c. Genital vein: testes/ovaries,

• d. Lumbar veins: lumbar region,

• e. Renal vein: Kidney,

• f. Suprarenal vein: adrenal gland,

• g. Hepatic vein: liver,

• h. Inferior phrenic vein: the lower surface of the diaphragm

1. Portal system: Portal veins constitute the portal system. Portal veins do not carry blood towards the heart. They arise from one organ to distribute blood to another organ. They form blood capillaries in the organs that receive blood.

These capillaries do not unite to form veins to supply blood to the heart. An organ with portal vein capillaries is called a portal organ. Blood circulation in the portal system is called portal circulation (Hepatic portal system).

Hepatic portal system: The splenic vein, superior mesenteric vein, inferior mesenteric vein, cystic vein, paraumbilical vein, and gastroepiploic vein constitute the hepatic portal system. These veins carry blood from different parts of the body to the liver as per the below detail.

• a. Superior mesenteric vein: small intestine, coecum

• b. Ascending and transverse colon

• c. Splenic vein: spleen

• d. Gastro epiploic vein: Pancreas and stomach

• e. Cystic vein: Gall bladder

• f. Paraumbilical vein: Abdominal wall

Pulmonary Circulation

Pulmonary circulation is the movement of blood between the heart and the lungs. It is responsible to oxygenate the blood and remove carbon dioxide.

• 1. Deoxygenated blood: Pulmonary circulation begins with deoxygenated blood returning to the heart from the body's tissues. This blood enters the right atrium of the heart through two large veins called the superior and inferior vena cavae.

• 2. Right Atrium: Once in the right atrium, the deoxygenated blood flows through the tricuspid valve from the right atrium to the right ventricle.

• 3. Right Ventricle: The right ventricle contracts. It pumps the deoxygenated blood through the pulmonary valve and into the pulmonary artery.

• 4. Pulmonary Artery: The pulmonary artery carries the deoxygenated blood away from the heart and towards the lungs. It branches into the left and right pulmonary arteries. These arteries deliver blood to the left and right lungs respectively.

• 5. Lungs: The pulmonary arteries further divide into smaller arteries and arterioles and pulmonary capillaries inside the lungs. The pulmonary capillaries surround the alveoli.

• 6. Gas Exchange: Deoxygenated blood releases carbon dioxide and absorbs oxygen through the process of gas exchange. Oxygen diffuses from the alveoli into the blood, while carbon dioxide moves from the blood into the alveoli to be exhaled.

• 7. Oxygenated blood: The blood becomes oxygenated. Oxygen-rich blood travels from the pulmonary capillaries into the pulmonary venules. Pulmonary venules merge to form pulmonary veins.

• 8. Pulmonary vein: The pulmonary veins carry oxygenated blood from the lungs to the heart. Four pulmonary veins (two from each lung) enter the left atrium of the heart.

• 9. Left Atrium: Oxygenated blood flows from the left atrium through the mitral valve into the left ventricle.

• 10. Left ventricle: The left ventricle contracts. It pumps oxygenated blood through the aortic valve and into the aorta.

• 11. Systemic Circulation: Oxygenated blood is distributed throughout the body via systemic circulation. It delivers oxygen and nutrients to tissues and organs.