Blood Overview and Properties

Study Notes

Blood is a fluid connective tissue that circulates throughout the body within blood vessels.
It flows in a unidirectional manner.
It is composed of liquid (plasma) and solid components (blood cells).
In medical terms, blood is also referred to as hemo or hemato.

Color: Arterial blood is bright red (high oxygen) and venous blood is dark purple/red (low oxygen).
Volume: Average adult male blood volume is 5-6 liters, and for females is 4-5 liters. A newborn's blood volume is approximately 450 ml.
Weight: Blood comprises about 8% of the total body weight in a healthy adult.
Reaction and pH: Blood is slightly alkaline, with a pH of 7.4 under normal conditions.
Viscosity: Blood is approximately five times more viscous than water due to red blood cells and plasma proteins.
Temperature: Blood temperature is about 38°C, 1°C higher than normal body temperature.

Early Embryonic Development: Blood formation initially occurs in the yolk sac; later, the liver, spleen, and lymph nodes become involved.
Adult: Hematopoiesis mainly takes place in the red bone marrow.

Plasma (Liquid Portion): Approximately 55% of whole blood, it is a straw-colored liquid.
Primarily water, with proteins (albumins, globulins, fibrinogen), electrolytes, nutrients, respiratory gases, and waste products.
Formed Elements (Solid Portion): Approximately 45% of whole blood.
- Erythrocytes (Red Blood Cells): 3.5-5.5 million/mm³, red-colored, biconcave discs, crucial for oxygen transport.
- Leukocytes (White Blood Cells): ~4500-11,000/mm³, colorless, crucial in immune response and defense against infection.
  - Granulocytes (contain granules): Neutrophils, Eosinophils, Basophils.
  - Agranulocytes (lack granules): Lymphocytes, Monocytes.
- Platelets (Thrombocytes): ~150,000-400,000/mm³, cell fragments involved in blood clotting and preventing blood loss.