Blood is a specialized connective tissue consisting of cells suspended in a liquid matrix called plasma.
Blood is composed of various cellular components, including red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes), suspended in plasma.
The red blood cells are responsible for oxygen transport, while white blood cells are involved in immune responses. Platelets aid in clotting.
Composition of Blood
1. Plasma (about 55% of blood volume)
Plasma is the liquid portion of blood, primarily made of water (about 90%) and contains dissolved proteins, glucose, mineral ions, hormones, and other substances.
Functions:
Transport Medium: Carries nutrients, waste products, and hormones throughout the body.
Regulation: Helps regulate body temperature and maintain the acid-base balance.
2. Cellular Components (Formed Elements)
The cellular components, or formed elements, include red blood cells (RBCs), white blood cells (WBCs), and platelets. Each has specific roles:
A. Red Blood Cells (RBCs) or Erythrocytes
The most abundant blood cells, responsible for oxygen transport.
Functions:
Oxygen Transport: RBCs transport oxygen from the lungs to body tissues and remove carbon dioxide, a waste product of cellular metabolism.
Hemoglobin: RBCs contain hemoglobin, an oxygen-binding protein that gives them their red color.
Acid-Base Balance: RBCs help maintain the blood's pH balance.
B. White Blood Cells (WBCs) or Leukocytes
Nucleated cells crucial for the immune system, protecting the body against infections and diseases.
Types and Functions:
I. Neutrophils: The most abundant WBCs, which phagocytize (engulf and destroy) bacteria and foreign particles.
II. Lymphocytes: Produce antibodies and regulate immune responses; include:
B-cells: Produce antibodies.
T-cells: Directly attack infected cells and regulate immune responses.
Natural Killer (NK) Cells: Kill abnormal cells, such as cancerous or virus-infected cells.
III. Monocytes: Transform into macrophages that phagocytize pathogens, dead cells, and debris.
IV. Eosinophils: Combat parasitic infections and participate in allergic reactions.
V. Basophils: Release histamine during allergic reactions and contribute to inflammation.
C. Platelets or Thrombocytes
Small cell fragments critical for blood clotting and wound healing.
Functions:
Clot Formation: Platelets clump together at injury sites to form a plug, preventing excessive blood loss.
Wound Healing: Release growth factors that promote tissue repair and regeneration.
Functions of blood
Transportation: Carries oxygen to tissues, removes carbon dioxide, and transports nutrients, hormones, and waste products.
Immune Response: Contains white blood cells that defend against infections and diseases.
Clotting: Platelets form clots to prevent excessive bleeding.
Regulation: Maintains pH balance and electrolyte levels (e.g., sodium, potassium).
Temperature Regulation: Distributes heat throughout the body.
Hormone Transport: Delivers hormones from glands to target organs.