Blood - Composition of Blood: Plasma (The Liquid Portion of Blood)

Plasma is the liquid part of blood that appears pale yellow, clear, and slightly alkaline. It makes up about 55% of the total blood volume and serves as a medium for transporting various substances throughout the body.

• Plasma is made up of 90-92% water, which keeps the blood fluid and helps transport nutrients, hormones, and waste products.
• The remaining part consists of 6-8% proteins and 1-2% inorganic salts and other components.

1. Albumin

Albumin is a type of protein in plasma that helps distribute water throughout the body, ensuring a proper balance between the tissues and the bloodstream. This helps maintain blood pressure and volume.

2. Globulins

Globulins are proteins that play a role in protecting the body from infections. They act as antibodies, which are part of the immune system and help fight off bacteria, viruses, and other harmful invaders.

3. Fibrinogen and Prothrombin

These are proteins involved in blood clotting. Fibrinogen and prothrombin work together to form clots and stop bleeding when an injury occurs. They are essential for preventing excessive blood loss.

4. Inorganic Ions (like Calcium, Sodium, and Potassium)

These ions help regulate muscle and nerve function.

• Calcium (Ca): Important for muscle contraction, blood clotting, and nerve signalling.
• Sodium (Na): Helps maintain fluid balance, supports nerve impulses, and contributes to muscle function.
• Potassium (K): Essential for proper heart function, nerve impulses, and muscle contractions.

Blood plasma, though 92% water, plays several vital roles in the body.

1. It contains 7% essential proteins, including albumin, gamma globulin, and antihemophilic factor, along with 1% mineral salts, sugars, fats, hormones, and vitamins.
2. Plasma helps maintain stable blood pressure and blood volume.
3. It provides critical proteins necessary for blood clotting and immune defence.
4. It transports electrolytes, such as sodium and potassium, to support muscle function.
5. Plasma also helps regulate the body’s pH (acid-base) balance, which is crucial for proper cell function.