blood

Chapter 17 – Blood

Functions of Blood

Blood is a connective tissue with three primary functions:

1. Transport

   • Carries oxygen (O₂) from lungs → tissues.

   • Carrying waste products from the cells to sites for elimination

   • Delivers carbon dioxide (CO₂) from tissues → lungs for exhalation.

   • Transports nutrients (from digestive tract → tissues).

   • Transports hormones (from endocrine glands → target organs).

   • Removes metabolic wastes (to kidneys, lungs, sweat glands for excretion).

2. Regulation

   • Body temperature: absorbs/distributes heat throughout body.

   • pH balance: buffers blood (bicarbonate system) to maintain ~7.35–7.45 pH.

   • Fluid balance: maintains proper water/salt content in cells and tissues.

3. Protection

   • Clotting mechanisms: prevent blood loss after vessel injury.

   • Immune defenses: WBCs, antibodies, complement proteins fight infection.

What is Blood?

• Specialized connective tissue.

• Composed of:

  • Plasma (~55%) → fluid matrix.

  • Formed elements (~45%) → RBCs, WBCs, platelets.

• Volume: ~5 L in average adult.

Physical Characteristics

• Color: scarlet (oxygen-rich) → dark red (oxygen-poor).

• Viscosity: thicker than water, sticky due to red blood cells (erythrocytes)

• pH: slightly alkaline (7.35–7.45).

• Temperature: ~38°C (100.4°F).

Weight: ~8% of body weight