06 CVS1 Lymphatic systems

Anatomy of the Circulatory Systems

Lymphatic System Overview

  • Author: Niggy Gouldsborough

  • Description: The lymphatic system is an integral part of the circulatory system, consisting of a network of vessels, lymph, and specialized tissues.

Components of the Lymphatic System

Major Components

  • Network of lymph vessels: Transport lymph throughout the body.

  • Lymph: The fluid that circulates within the lymphatic system.

  • Lymphatic tissues and organs: Includes lymph nodes, spleen, and thymus, which play critical roles in immunity.

Functions

  • Defense Mechanisms: The lymphatic system is involved in the body’s immune response, helping to defend against pathogens.

  • Fluid Drainage: Provides a mechanism for the drainage of interstitial fluid, preventing tissue swelling and maintaining fluid balance (Martini et al, 2018).

Interstitial Fluid and Capillary Dynamics

Fluid Dynamics

  • Interstitial Fluid Movement:

    • Fluid moves from the interstitial space back into the capillary at the venous end.

    • Fluid moves from the arterial end of the capillary into the interstitial space.

  • Labeling:

    • In the capillary, the fluid is termed plasma.

    • In the interstitial space, it is called interstitial fluid.

Capillary Exchange Mechanisms

Exchange Processes

  • Capillary Blood Pressure (CBP):

    • Pushes fluid out of the capillary into the interstitial fluid (process called filtration).

    • Facilitates the transport of nutrients and gases.

  • Blood Colloid Osmotic Pressure (BCOP):

    • Pulls fluid back into the capillary, aiding in the removal of wastes (process called reabsorption).

    • Primarily driven by plasma proteins.

Pressure Gradients

  • Arterial End vs. Venous End:

    • At the arterial end, CBP is greater than BCOP, leading to filtration.

    • At the venous end, BCOP is greater than CBP, leading to reabsorption.

    • CBP decreases over the length of the capillary, while BCOP remains constant.

Capillary Exchange Efficiency

Fluid Reabsorption

  • Approximately 85% of the filtered fluid is reabsorbed at the venous end.

  • The remaining 15% enters the lymphatic system, which is critical for preventing edema.

Role of Lymphatic Capillaries

Lymphatic Capillaries

  • Structure: Blind-ended tubes located adjacent to capillary beds.

  • Fluid Collection: Excess interstitial fluid that enters the lymphatic capillary is called lymph.

  • Lymphatic Circulation: Lymph flows through the lymphatic circulation and eventually returns to the blood system.

Lymphatic Drainage Pathways

Pathway of Lymph

  1. Lymph Capillaries

  2. Lymph Vessels

  3. Lymph Trunks

  4. Ducts:

    • Thoracic Duct: Drains lymph from the left side of the body and the lower body.

    • Right Lymphatic Duct: Drains lymph from the right side of the head, thorax, and upper limb.

  5. Lymph Nodes: Filter lymph and mount immune responses.

Return to Circulation

  • Lymph eventually drains into the right subclavian vein and left subclavian vein, re-entering the vascular circulation (Martini et al, 2018).