Blood
- Blood is the body’s fluid connective tissue, and it forms a vital part of the human circulatory system.
- Its main function is to circulate nutrients, hormones, minerals and other essential components to different parts of the body.
- Blood flows through a specified set of pathways called blood vessels. The organ which is involved in pumping blood to different body parts is the heart.
Blood is composed of:
- Plasma – the fluid part of the blood and is composed of 90% of water.
- Red blood cells, white blood cells and platelets constitute the solid part of blood.
Types of Blood Cells
Red blood cells (RBC) / Erythrocytes
- Red blood cells are mainly involved in transporting oxygen, nutrients, and other substances to various parts of the body. These blood cells also remove waste from the body.
White blood cells (WBC) / Leukocytes
- White blood cells are specialized cells, which function as a body’s defence system. They provide immunity by fending off pathogens and harmful microorganisms.
Platelets / Thrombocytes
- Platelets are cells that help to form clots and stop bleeding. They act on the site of an injury or a wound.
Blood Vessels
- Blood vessels are a network of pathways through which blood travels throughout the body.
- Arteries and veins are the two primary types of blood vessels in the circulatory system of the body.
Arteries
- Arteries are blood vessels that transport oxygenated blood from the heart to various parts of the body.
- They are thick, elastic and are divided into a small network of blood vessels called capillaries.
- The only exception to this is the pulmonary arteries, which carries deoxygenated blood to the lungs.
Veins
- Veins are blood vessels that carry deoxygenated blood towards the heart from various parts of the body.
- They are thin, elastic and are present closer to the surface of the skin.
- However, pulmonary and umbilical veins are the only veins that carry oxygenated blood in the entire body.