Blood

Definition:

Blood is a specialized body fluid that circulates through the cardiovascular system, delivering essential substances such as oxygen and nutrients to cells and removing waste products like carbon dioxide. It also plays vital roles in immune defense, regulation of body temperature, and maintaining homeostasis.

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Parts of Blood:

Blood is composed of two main components:

1. Plasma:
   • The liquid portion, making up about 55% of blood volume.
   • Composed of water (90%), electrolytes, nutrients, hormones, waste products, and plasma proteins (e.g., albumin, globulins, and fibrinogen).
2. Formed Elements (Cells):
   • Red Blood Cells (Erythrocytes):
     • Contain hemoglobin, which binds to oxygen and transports it from the lungs to the tissues.
     • Responsible for the red color of blood.
   • White Blood Cells (Leukocytes):
     • Part of the immune system, protecting the body against infections and foreign invaders.
     • Types include:
       • Neutrophils: First responders to infection, performing phagocytosis.
       • Lymphocytes: Include T-cells and B-cells for adaptive immunity.
       • Monocytes: Become macrophages that engulf pathogens and debris.
       • Eosinophils: Fight parasitic infections and are involved in allergic reactions.
       • Basophils: Release histamine and heparin during allergic responses.
   • Platelets (Thrombocytes):
     • Cell fragments involved in blood clotting (hemostasis) to prevent bleeding.

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Functions of Blood:

1. Transportation:
   • Carries oxygen from the lungs to body tissues and carbon dioxide back to the lungs for exhalation.
   • Transports nutrients from the digestive system to cells.
   • Delivers hormones from endocrine glands to target organs.
   • Carries metabolic waste products to the kidneys and liver for excretion.
2. Regulation:
   • Maintains body temperature by distributing heat.
   • Balances pH levels through buffering systems.
   • Regulates fluid and electrolyte balance in body tissues.
3. Protection:
   • Clotting Mechanism: Platelets and plasma proteins (e.g., fibrinogen) form blood clots to prevent excessive bleeding.
   • Immune Defense: White blood cells defend against pathogens, and antibodies neutralize toxins and harmful microorganisms.
4. Homeostasis:
   • Maintains stable internal conditions, supporting cellular function and overall health.