Biology: Blood Components and Function

Understanding Biology: Blood Components and Function

Plasma does more than act as a liquid background. Its water content helps maintain blood volume and allows substances to move quickly. Plasma proteins have specialised jobs.

Albumin helps keep water in the bloodstream by creating an osmotic pull. Without enough albumin, fluid can leak into tissues and cause swelling. Other proteins include antibodies, which recognise foreign material, and clotting factors, which circulate in an inactive form until a vessel is damaged.

Plasma also helps control pH and body temperature. When a person becomes badly dehydrated, plasma volume falls. This makes circulation harder and can lower blood pressure.

Red blood cells are shaped like flexible discs with a dip in the middle. This shape gives them a large surface area for gas exchange and lets them squeeze through tiny capillaries. Mature human red blood cells have no nucleus.

That leaves more room for haemoglobin, but it means the cells cannot divide or repair themselves. They survive for roughly four months before being removed, mainly by the spleen and liver. Their iron is recycled to make new haemoglobin.

A low red cell count or too little haemoglobin is called anaemia. It can reduce oxygen delivery, causing tiredness, breathlessness, pale skin, or poor concentration.

White blood cells are not one single type of cell. Neutrophils often arrive early at a bacterial infection and can engulf microbes. Lymphocytes include B cells, which can make antibodies, and T cells, which can destroy infected body cells or direct other immune responses.

Some immune cells become memory cells after an infection or vaccination. They help the body respond faster if the same pathogen enters again. Inflammation is part of this defence system.

Increased blood flow makes an injured area red and warm, while fluid and immune cells moving into tissue can cause swelling. These signs are useful, though excessive inflammation can damage healthy tissue.

Clotting needs careful control because blood must seal a cut without blocking an undamaged vessel. Platelets first attach to exposed material at the injury and clump together to make a temporary plug. Chemical signals then start a chain of reactions involving clotting proteins.

The final clot contains fibrin, a tough mesh that traps cells and strengthens the plug. After repair, the body gradually breaks the clot down. Students often confuse a clot with a scab.

A clot forms inside or at the surface of damaged tissue, while a scab is the dry protective layer that forms over a skin wound. Blood tests can measure cell numbers, haemoglobin, proteins, glucose, and clotting ability, helping doctors identify problems in these systems.