Functions of Blood

Overview of Blood

Blood is a specialized, red, viscous liquid connective tissue that plays a vital role in the cardiovascular system. It is slightly alkaline (pH 7.35–7.45) and constitutes about 8% of total body mass, with adults having approximately 4–6 liters of blood.

• Definition: Blood is a fluid connective tissue composed of plasma and formed elements.

• Key Properties: Red color, viscous texture, specialized for transport and regulation.

• pH: Slightly alkaline, optimal for physiological processes.

Essential Functions of Blood

Blood supports life by performing three main functions: Transport, Regulation, and Protection.

• Transport:

  • Delivers oxygen (O2), nutrients, and hormones to body cells.

  • Transports wastes (e.g., carbon dioxide, urea) to elimination sites.

• Regulation:

  • Maintains body temperature.

  • Buffers maintain optimal pH range.

  • Maintains volume in cardiovascular system.

• Protection:

  • Prevents blood loss (success) through clotting mechanisms.

  • Prevents infection via immune cells.

Example: Blood transports oxygen from the lungs to tissues and removes carbon dioxide for exhalation.

Composition of Blood

Main Components

Blood can be separated into three main components: Erythrocytes, Buffy Coat, and Plasma.

• Erythrocytes (Red Blood Cells, RBCs):

  • Main cell type in blood, adapted for O2 and CO2 transport.

  • Hematocrit: Percentage of total blood volume composed of RBCs (range: 36–50%).

  • Classified as formed elements (living cells).

• Buffy Coat:

  • Consists of White Blood Cells (provide immunity) and Platelets (blood clotting).

  • Less than 1% of blood volume.

• Plasma:

  • 90% water, electrolytes (Na+, Cl-, etc.), and various proteins (albumin, globulins, fibrinogen).

  • About 55% of blood volume.

  • Classified as the matrix (non-living component).

Blood Component Table

Key Facts and Practice Questions

• Plasma accounts for 55% of all blood; water accounts for 90% of plasma.

• Platelets are the most numerous formed element in blood after RBCs; their function is to prevent bleeding from open wounds.

• White blood cells fight infection; erythrocytes carry oxygen and carbon dioxide.

Formulas and Equations

• Hematocrit Calculation:

Examples and Applications

• Blood transports hormones from endocrine glands to target organs.

• Regulation of pH balance by buffering acidic and alkaline substances.

• Removal of metabolic waste products such as carbon dioxide and urea.

Additional info: Blood does not produce digestive enzymes for breaking down food in the stomach; this is a function of the digestive system, not the circulatory system.