What is the meaning of blood?

The blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from them. It also serves to fight infection and maintain homeostasis.

The blood is composed of several components:

- Plasma: The liquid part of the blood that makes up about 55% of its volume. Plasma contains water, salts, proteins, hormones, and waste products such as urea and creatinine.

- Red blood cells (erythrocytes): These are the most abundant cells in the blood and make up about 45% of its volume. Red blood cells contain haemoglobin, an iron-containing protein that carries oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs.

- White blood cells (leukocytes): These are cells that help the body fight infection. They make up about 1% of the blood's volume.

- Platelets (thrombocytes): These are small cell fragments that help the blood to clot and prevent excessive bleeding. They make up about 0.5% of the blood's volume.