Cellular Structure and Blood Components

Cellular Composition

• Definition: The body is composed of cells, which are the basic building blocks.

  • Examples: bone cells, skin cells.

Anatomical Structures of a Cell

• Three Main Components:

  1. Cytoplasm:

  • A liquid medium primarily made up of water inside the cell.

  • It allows various cellular processes to occur.

  1. Cell Membrane:

  • Encloses the cell and maintains its integrity by separating it from the external environment.

  • Semi-permeable, allowing selective entry and exit of substances.

  1. Nucleus:

  • Controls all cell functions, including reproduction.

  • Has varying shapes, often round.

Blood Composition

• Total Blood Volume:

  • An average adult has about 12-13 pints of blood; children have smaller amounts.

  • Approximately 10 pints are actively circulating through the heart.

• Components of Blood:

  1. Cellular Component:

  • Contains all blood cells, which occupy about 40-45% of total blood volume.

  1. Acellular Component:

  • Comprises the plasma and occupies approximately 55-60% of blood volume.

Blood Functions

• Blood performs critical functions including:

  • Transporting nutrients from the digestive system to the cells.

  • Delivering oxygen to maintain cell function.

  • Preventing toxins from entering cells.

Types of Blood Cells

1. Red Blood Cells (Erythrocytes):

   • Most numerous cells in blood, normal count: 4.5-5.4 million per mm³.

   • Major functions include transporting oxygen via hemoglobin (Hb), which has a weak bond with oxygen to facilitate release.

   • Structurally, they are bi-concave disks, maximizing surface area for gas exchange.

2. White Blood Cells (Leukocytes):

   • Play a vital role in immune response.

   • Types include Granular and Agranular cells:

     • Granular: Basophils, Eosinophils, Neutrophils.

     • Agranular: Lymphocytes (B and T lymphocytes).

   • Function in identifying and destroying pathogens via processes such as phagocytosis, where bacteria are engulfed.

3. Platelets (Thrombocytes):

   • Small cell fragments with a normal range of 200,000 - 400,000 per mm³.

   • Function in blood clotting, particularly in smaller blood vessels. They aggregate and form a clot to prevent bleeding.

Blood Coagulation Process

• Fibrinogen Conversion:

  • Fibrinogen converts from a water-soluble form to an insoluble fibrin form, forming blood clots.

  • Fibrin is essential for clotting blood effectively after an injury occurs.

Key Hematological Tests

• Complete Blood Count (CBC):

  • Tests for levels of Red Blood Cells, White Blood Cells, and Platelets in the blood.

  • Elevated white cell counts may indicate various conditions and are measured through additional tests like Differential Blood Count (DBC).

Summary of Normal Counts

• Blood Cell Counts:

  • Erythrocytes: 4.5-5.4 million/mm³ (carry oxygen)

  • Leukocytes: 6,000-8,000/mm³ (protect from infection)

  • Thrombocytes: 200,000-400,000/mm³ (assist in clotting)