Blood and blood circulation Tnpsc

Blood circulation system

Human heart and blood circulatory system
Parts of Heart

A special system that contains the heart, blood vessels, and blood is called the blood circulation system.

The circulatory system makes the blood circulate around the body because of the contraction and expansion of the heart.

The two types of blood vascular system are open blood and closed blood vascular system.

The blood is pumped by the heart into the blood vessels that open into blood spaces (cavities) is known as the open blood vascular system.

The blood is circulating through the blood vessels and it creates blood pressure inside the blood vessels is known as the closed blood vascular system.

The capillary system is absent in the open blood vascular system. The cavities are called haemocoel.

The pressure of blood in the open type is very low. Example- Cockroach. An example of a closed vascular system is the human blood vascular system.

The heart is placed inside the thoracic chamber in between the two lungs in the mediastinum.

The human heart consists of 4 chambers. Two upper thin chambers are called artria. The lower thick chambers are called Ventricles.

The right side of the heart is separated from the left side by a longitudinal wall named inter artrio- ventricular septum. The coronary vein is connected with the heart in the right atrium.

The pulmonary artery connected with the heart is the right ventricle. The pulmonary vein connected to the heart is covered in our left atrium.

The aorta connected with the heart is the left ventricle. Oxygenated blood is found in the pulmonary vein. Deoxygenated blood is found in the pulmonary artery.

The 3 types of valves found in the heart are the tricuspid valve, bicuspid valve, and semilunar valves. The valve located in between the right atrium and right ventricle is the tricuspid valve.

The valve that lies in between the left atrium and left ventricle is a bicuspid valve also known as the Mitral valve.

The valve present near the mouth of the pulmonary artery and aorta is the semilunar valve. The blood vessels carrying blood away from the heart are called arteries.

The arteries carry oxygenated blood except for the pulmonary artery. The veins carry deoxygenated blood except for the pulmonary vein.

The fine small tubes found spreading in the midst of the cells are capillaries. The vital tube of the blood vascular system is the capillaries.

The carrier of blood from the heart to organs is Arteries. The carrier of blood from the organs to the heart is veins.

The walls of arteries are thick and elastic. The wall of the vein is thin and less elastic. Arteries are found deeps inside the muscles.

Veins are found superficially and it is absent in the arteries. Valves are present in veins.

blood circulation system
blood circulatory system


Components of human blood are blood corpuscles and plasma. Plasma contains proteins, enzymes, hormones, waste, and elements.

45% volume of blood contains blood corpuscles. Three types of blood corpuscles are erythrocytes, leukocytes, and thrombocytes.

Erythrocytes are also known as Red blood Corpuscles or RBC. Leucocytes are also known as White Blood Corpuscles or WBC.

Thrombocytes are otherwise known as blood platelets. The red, biconcave, and disc-shaped cells are erythrocytes. The red color of RBC is due to the presence of respiratory pigment haemoglobin.

Haemoglobin function is to transport oxygen and carbon dioxide to the body. One cubic mm of blood contains 5 million RBC.

The life span of RBC is 120 days.RBC is destroyed in the liver and spleen.RBC is produced by the red marrow bone. The colorless, irregular, and nucleated cells are called Leucocytes.

One cubic mm of blood contains 8000 WBC. The 5 types of WBC are monocytes, Lymphocytes, Neutrophils, Eosinophils, and Basophils. The life span of WBC is 4 weeks.WBC are prepared by yellow marrow bone and lymphatic tissue.

The main function of WBC is to attack the invading germs and protect our bodies. The small, non-nucleated, and colorless structures floating in the plasma are Thrombocytes.

In one cubic mm of blood contains 2,00,000 to 4,00,000 Thrombocytes.At the time of injury, the Thrombocytes disintegrate to give rise to thromboplastin which helps in the clotting of blood.

The digested food gets distributed through the blood. The metabolic wastes are carried to the excretory organs through blood.

The secretion of endocrine glands carried by the blood is called hormones. The heat energy is distributed throughout the body by Blood. Blood keeps all the tissue moist.

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* * All the Notes in this blog, are referred from Tamil Nadu State Board Books and Samacheer Kalvi Books. Kindly check with the original Tamil Nadu state board books and Ncert Books.
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