Plasma
Plasma accounts for around 55% of blood fluid in humans. Plasma is 92% water, and the contents of the remaining 8% include:
l glucose
l hormones
l proteins
l mineral salts
l fats
l vitamins
The remaining 45% of blood mainly consists of red and white blood cells and platelets. Each of these has a vital role to play in keeping the blood functioning effectively.
Red blood cells, or erythrocytes
Red blood cells have a slightly indented, flattened disk shape. They transport oxygen to and from the lungs. Hemoglobin is a protein that contains iron and carries oxygen to its destination. The life span of a red blood cell is 4 months, and the body replaces them regularly. The human body produces around 2 millionTrusted Source blood cells every second.
The expected number of red blood cells in a single drop (microliter) of blood is 4.5–6.2 million in males and 4.0–5.2 million in females.
White blood cells, or leukocytes
White blood cells make up less than 1% of blood content, forming vital defenses against disease and infection. The number of white blood cells in a microliter of blood usually ranges from 3,700–10,500. Higher or lower levels of white blood cells can indicate disease.
Platelets, or thrombocytes
Platelets interact with clotting proteins to prevent or stop bleeding. There should be between 150,000 and 400,000 platelets per microliter of blood.
Bone marrow produces red blood cells, white blood cells, and platelets, and from there they enter the bloodstream. Plasma is mostly water that is absorbed from ingested food and fluid by the intestines. The heart pumps them around the body as blood by way of the blood vessels.
Functions
Blood has various functions that are central to survival. They include:
l supplying oxygen to cells and tissues
l providing essential nutrients to cells, such as amino acids, fatty acids, and glucose
l removing waste materials, such as carbon dioxide, urea, and lactic acid
l protecting the body from diseases, infections, and foreign bodies through the action of white blood cells
l regulating body temperature
The platelets in blood enable the clotting, or coagulation, of blood. When bleeding occurs, the platelets group together to create a clot. The clot forms a scab, which stops the bleeding and helps protect the wound from infection.
Summary
Blood is essential for maintaining the health and life of the human body. It has many functions, including delivering nutrients and oxygen. The four main components of blood are red blood cells, white blood cells, plasma, and platelets.
Problems that arise due to illness or blood loss can be life threatening, but effective treatment is available for many blood-related disorders.