The Lymphatic System

Overview

• Complements the circulatory system by managing fluid levels in the body.
• Collects excess interstitial fluid and returns it to the bloodstream.
• Plays a vital role in the immune system.

Key Components

1. Lymphatic Vessels

   • Collect excess interstitial fluid.
   • Start as highly permeable lymphatic capillaries.
   • Form larger lymphatic vessels and trunks.
   • Lack a central pump; rely on pressure changes and valves for lymph flow.
   • Flow is stronger during physical activity.

2. Lymph

   • The fluid collected by lymphatic vessels.
   • Includes interstitial fluid, proteins, bacteria, and pathogens.

3. Lymph Nodes

   • Act as filters for the lymph.
   • Contain macrophages that destroy pathogens.
   • Activate the immune system.
   • Structure:
     • Dense fibrous capsule.
     • Trabeculae divide the node into compartments.
     • Cortex with follicles and medulla with medullary cords and sinuses.

Lymphoid Organs

1. Spleen

   • Location: Upper left abdomen, adjacent to the stomach.
   • Functions:
     • Immune surveillance and cleansing of blood.
     • Salvages iron and stores blood components.
   • Structure:
     • White pulp: Immune functions.
     • Red pulp: Removes old/damaged red blood cells.

2. Thymus

   • Location: Thorax, below the neck.
   • Function: Development of certain lymphocytes.
   • More active in newborns.

3. Lymphoid Tissues

   • Tonsils: Located around the mouth and throat; remove pathogens.
   • Peyer's Patches: In the small intestine; destroy bacteria.
   • Appendix: Rich in lymphoid follicles; destroys bacteria.

Functions

• Maintains blood volume by returning excess fluid to the bloodstream.
• Integral to the immune system by filtering pathogens and activating immune responses.

Connection to the Immune System

• The lymphatic system works closely with the immune system to maintain health and defend against diseases.