Blood Circulatory System

Blood Circulatory System is a system of organs which are responsible for the transmission of essentials nutrients, oxygen, hormone, etc. to the human body.

The system of organs which are responsible for the transmission of essentials nutrients, oxygen, hormone, etc. to the different parts of the human body and collection of the unwanted waste materials such as urea, uric acid, carbon dioxide, etc. from different parts of the body to excretory organs is known as blood circulatory system.

It consists of blood, the heart, and blood vessels.

1. Blood

Blood is a connective tissue composed of plasma and blood cells. 

Blood is responsible for the transmission of nutrients, hormones, oxygen, etc. to the different parts of the body and the collection of the waste materials from the different parts of the body to the excretory organs. Blood is red in color due to the presence of ‘hemoglobin’. There are about 5.5 liters of blood in the body of an adult healthy person.

Plasma

About 55% composition of blood consists of plasma. It is a yellow transparent liquid. It is composed of 90% water and the remaining 10% protein, mineral, fat, and carbohydrate.

Function of plasma

• It transports urea from liver to kidney.
• It carries carbon dioxide from the different parts of the body to the lungs during respiration. 
• It carries the hormone produced by the endocrine gland to the different parts of the body.
• It balances the amount of water in the body.

Fibrinogen

It is a plasma protein that helps in clotting the blood thereby preventing the loss of blood from the wounds.

Blood cells

About 45% of the blood is composed of blood cells. There are 3 types of blood cells, they are:

1. Red Blood Cell (RBC)
2. White Blood Cell (WBC)
3. Platelets

Composition of Blood

1. RBC

Red Blood Cell is also known as erythrocytes. It is biconcave in nature. They are formed in the bone marrow. About 20 lakhs RBC are produced every second and they are produced every second and they are destroyed in the same number every second. They are destroyed in the liver and spleen. But the iron found in RBC is reused. RBC does not contain a nucleus. 

It consists of a red pigment called hemoglobin. Hemoglobin contains iron which absorbs oxygen from the lungs. The hemoglobin containing oxygen is called oxy-hemoglobin.

Function of RBC

It transports oxygen to the different parts of the body. (cells and tissues)

2. WBC

They are also called leucocytes. They are larger in size, colorless, and contains a nucleus. They are found in the bone marrow and destroyed in infected areas. The life span of WBC is about 15 days.

Functions of WBC

• They fight against germs. SO, they are called the police of the body.
• They destroy some diseases causing germs.
• Some of them remove the damaged cells or germs to remove the damaged cells or germs from the infected area of the body and help in the quick healing of the body.

3. Platelets

They are also known as ‘thrombocytes. They are small, irregular, colorless, and have no nucleus. They are produced in the bone marrow. Their lifespan is 1 to 3 days and destroyed in the spleen.

Functions of platelets

It helps in blood clotting and hence prevents the loss of blood from the cuts and wounds.

Functions of blood

The functions of blood are classified into three groups, they are:

1. Transmission
2. Regulation/control
3. Protection

1. Transmission

• Blood transports oxygen from the lungs to the tissues and carbon dioxide from tissues to the lungs.
• It carries nutrients to all parts of the body.
• It transports waste products to the excretory organs.
• It transports hormones produced by the endocrine gland to the different parts of the body.

2. Regulation/Control

• Blood regulates body temperature.
• It maintains the water level in the body.

3. Protection

• WBC protects the body from the infection of various diseases.
• Platelets help in clotting the blood and prevent the loss of blood from the cut and wounds.