Blood

Blood is a specialized bodily fluid in humans and other animals that delivers essential substances such as oxygen and nutrients to cells and transports metabolic waste products away from those cells. It circulates through the body via the circulatory system and plays a vital role in maintaining life and overall body function.

Blood is composed of plasma, red blood cells, white blood cells and platelets. It performs multiple important functions including oxygen transport, immune defense, clotting and regulation of body temperature.

Composition

Blood consists of four main components:

Plasma

Plasma is the liquid portion of blood and makes up about 55% of total blood volume. It is mostly composed of water and contains proteins, hormones, nutrients, salts and waste products.

Red Blood Cells

Red blood cells (RBCs), also known as erythrocytes, contain haemoglobin which carries oxygen from the lungs to body tissues and returns carbon dioxide back to the lungs.

White Blood Cells

White blood cells (WBCs), or leukocytes, help protect the body against infections and diseases by supporting the immune system.

Platelets

Platelets, also called thrombocytes, are responsible for blood clotting and help prevent excessive bleeding during injuries.

Functions

Blood performs several critical functions in the human body:

• Transport of oxygen and nutrients
• Removal of waste materials
• Regulation of body temperature
• Immune system defense
• Blood clotting and wound healing
• Hormone transportation

Blood Groups

Human blood is classified into different blood groups based on the presence or absence of antigens on red blood cells.

ABO Blood Group System

The main blood groups are:

• A
• B
• AB
• O

Rh Factor

Each blood group may be either Rh-positive or Rh-negative depending on the presence of the Rh antigen.

Examples include:

• A+
• O-
• AB+

Medical Importance

Blood plays an essential role in medicine and healthcare. Blood tests help diagnose diseases and monitor health conditions. Blood transfusions are used during surgeries, accidents and treatment of various disorders.

Common blood-related disorders include:

• Anaemia
• Leukemia
• Hemophilia
• Sickle Cell Disease
• Thalassemia

Blood Donation

Blood donation is the voluntary process of giving blood to help patients requiring transfusions. Donated blood is used in emergencies, surgeries, cancer treatment and medical therapies.

World Blood Donor Day is observed annually on 14 June to raise awareness about the importance of blood donation.

See Also

• Human body
• Circulatory system
• Heart
• Blood donation
• Haemoglobin
• Plasma
• Red blood cell
• White blood cell