Blood – Components and Function

Blood is a specialized bodily fluid that plays a vital role in various physiological functions within the human body. It is considered a connective tissue because it consists of cells suspended in a liquid matrix called plasma. Blood circulates throughout the body via blood vessels, delivering essential substances to cells and tissues and removing waste products.

Components of Blood:


Plasma is the liquid portion of blood, making up about 55% of its volume. It is a pale yellow fluid containing water, electrolytes (such as sodium and potassium), hormones, waste products, and proteins. Plasma serves as a medium for transporting blood cells, nutrients, hormones, and other substances throughout the body.

Blood Cells

Blood contains three main types of cells:

Red Blood Cells (Erythrocytes)
These cells are responsible for transporting oxygen from the lungs to the body’s tissues and organs and carrying carbon dioxide back to the lungs for exhalation. Red blood cells contain a protein called hemoglobin, which binds to oxygen and gives blood its red color.

White Blood Cells (Leukocytes)
White blood cells are a crucial part of the immune system, defending the body against infections, viruses, bacteria, and other foreign invaders. There are different types of white blood cells with specific functions, such as neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

Platelets (Thrombocytes)
Platelets are cell fragments that play a key role in blood clotting (hemostasis). When there is an injury or damage to blood vessels, platelets help form clots to prevent excessive bleeding. They also release chemicals that initiate the clotting process.


Oxygen Transport

Red blood cells carry oxygen from the lungs to body tissues and organs, enabling cellular respiration and energy production

Nutrient Delivery

Blood transports nutrients absorbed from the digestive system to cells throughout the body, providing them with the necessary building blocks for growth and maintenance.

Waste Removal

Blood carries waste products, such as carbon dioxide and urea, away from cells to be eliminated through the lungs (carbon dioxide) and kidneys (urea).

Immune Response

White blood cells help defend the body against infections and diseases by identifying and neutralizing pathogens and foreign substances.

Clotting and Hemostasis

Platelets and clotting factors in the blood collaborate to form blood clots, which prevent excessive bleeding when blood vessels are damaged.

Hormone Transport

Blood carries hormones produced by various glands to target cells and tissues, helping to regulate various bodily functions.