Transport in Animals – Lymphatic System

TRANSPORT IN ANIMALS - LYMPHATIC SYSTEM

1. Overview of the Lymphatic System

• Definition: A network of tissues, organs, and vessels that helps maintain the body’s fluid balance and protect against pathogens.

• Components: Similar to circulatory system with pumps (lymphatic vessels) and fluid (lymph).

• 1-Way System: Unlike the closed circulatory system, the lymphatic system operates in one direction, towards the heart.

2. What is Lymph?

• Formation: Arterial blood carries oxygen and nutrients to cells.

• Fluid Movement: Due to arterial pressure, fluid leaves small arteries into the tissues, becoming interstitial fluid or tissue fluid, which nourishes cells and collects waste.

• Return Flow: Part of this fluid returns as venous blood to circulation; the remaining becomes lymph.

• Appearance: Lymph is a clear to yellowish fluid.

3. Fluid Definitions

• Blood Plasma: The liquid component of blood, found within blood vessels.

• Tissue Fluid: The interstitial fluid present between tissue cells.

• Lymph: The fluid found within the lymphatic system.

4. Structure of the Lymphatic System

• Lymph Capillaries: Originate and branch between tissue cells.

• Larger Vessels: Lymph capillaries converge to form larger lymphatic vessels, which empty into the right and thoracic ducts.

• Connection to Circulatory System:

  • Thoracic duct connects at the left subclavian vein.

  • Right lymphatic duct connects at the right subclavian vein.

• Movement Mechanisms: Lymph is transported towards the heart via:

  • Movement of internal organs.

  • Contraction of voluntary muscles.

  • Semilunar valves prevent backflow.

• Lymph Nodes: Distributed throughout the body, trapping foreign particles and producing lymphocytes and antibodies that boost the immune response.

5. Functions of the Lymphatic System

• Drainage of Interstitial Fluid: Essential for preventing edema by draining excess fluid.

• Fight Infection: Lymphocytes and antibodies combat infections.

• Transport Lipids: Function in the absorption and transport of fats from the digestive system.

6. Components of Blood

• Composition: Approximately 5 liters of blood consisting of:

  • Red Blood Cells (RBCs)

  • White Blood Cells (WBCs)

  • Platelets

  • Plasma (55% of blood volume)

7. Blood Plasma Characteristics

• Volume: Comprises 55% of blood volume; yellowish fluid.

• Composition: 95% water with numerous dissolved substances.

• Functions:

  • Transport of dissolved substances (e.g., CO2, glucose, salts, urea).

  • Nourishment to cells and removal of wastes.

  • Keeps blood vessels from collapsing.

8. Red Blood Cells (Erythrocytes)

• Structure: Biconcave shape enhances surface area for oxygen absorption; lacks nucleus to maximize hemoglobin capacity.

• Function:

  • Transport oxygen via oxyhemoglobin.

  • Remove carbon dioxide from cells.

9. White Blood Cells (Leukocytes)

• Structure: Larger than RBCs with variable shapes and prominent nuclei.

• Functions:

  • Defend the body against infections.

  • Lymphocytes create antibodies targeting foreign pathogens.

  • Phagocytes engulf and destroy foreign microorganisms through phagocytosis.

10. Blood Platelets (Thrombocytes)

• Nature: Cell fragments without nuclei.

• Function: Essential for blood clotting and protection against bleeding.

11. Relationship Between Lymphatic and Blood Systems

• Diagrammatic Representation: Illustrates the connection of tissue cells, lymph capillaries, and circulation within arteries and veins.

• Fluid Exchange: Tissue fluid exits through capillaries under pressure and enters lymphatic capillaries for drainage, emphasizing interdependence of the systems.