Human blood

Human Blood
File:Blood smear 2020.jpg
Microscopic view of human blood
Specialty	Hematology

Human blood is a specialized bodily fluid that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. Blood is essential for maintaining homeostasis, providing immunity, and facilitating the repair of tissues.

Composition

Human blood is composed of several key components:

Plasma

Plasma is the liquid component of blood, making up about 55% of its total volume. It is primarily composed of water, electrolytes, proteins, hormones, and waste products. Plasma serves as a medium for transporting nutrients, hormones, and proteins to the parts of the body that need it.

Red Blood Cells (Erythrocytes)

Red blood cells are responsible for carrying oxygen from the lungs to the rest of the body and returning carbon dioxide to the lungs for exhalation. They contain the protein hemoglobin, which binds to oxygen and gives blood its red color.

White Blood Cells (Leukocytes)

White blood cells are part of the immune system and help the body fight infection. There are several types of white blood cells, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specific functions in immune response.

Platelets (Thrombocytes)

Platelets are small cell fragments that play a crucial role in blood clotting. When a blood vessel is injured, platelets gather at the site and form a plug to help stop bleeding.

Functions

Blood performs many critical functions, including:

• Transportation: Blood transports oxygen, nutrients, hormones, and waste products throughout the body.
• Regulation: Blood helps regulate body temperature, pH levels, and fluid balance.
• Protection: Blood contains cells and proteins that are essential for immune defense and clotting.

Blood Types

Human blood is classified into different blood types based on the presence or absence of certain antigens on the surface of red blood cells. The most well-known blood group system is the ABO blood group system, which includes four main types: A, B, AB, and O. Another important system is the Rh factor, which can be either positive or negative.

Blood Disorders

There are numerous disorders that can affect blood, including:

• Anemia: A condition characterized by a deficiency of red blood cells or hemoglobin, leading to fatigue and weakness.
• Leukemia: A type of cancer that affects white blood cells.
• Hemophilia: A genetic disorder that impairs the body's ability to make blood clots.
• Thrombocytopenia: A condition characterized by a low platelet count, leading to increased bleeding risk.

Also see

• Hematology
• Circulatory system
• Bone marrow
• Blood transfusion
• Immune system