Lymphatic system images

The Lymphatic System

Overview

• The Lymphatic System is essential for maintaining fluid balance, transporting immune cells, and facilitating dietary lipid transport.

• Comprised of lymphoid organs and tissues.

Lymphoid Organs and Tissues

• Primary Lymphoid Organs:

  • Thymus

  • Red bone marrow

• Secondary Lymphoid Organs:

  • Lymph nodes

  • Spleen

  • Tonsils

  • Peyer's patches (aggregated lymphoid nodules in the small intestine)

  • Appendix

  • Mucosa-associated lymphoid tissue (MALT) - includes structures in the intestines and tonsils.

Functions of the Lymphatic System

• Drains interstitial fluid from tissues to maintain blood pressure.

• Transports immune cells enabling responses to pathogens and infections.

• Facilitates absorption and transport of dietary lipids and fat-soluble vitamins from the gastrointestinal tract.

Lymphatic Vessel Structure and Function

• Types of Vessels:

• Lymphatic capillaries: smallest, collect excess interstitial fluid.

• Collecting vessels: transport lymph to lymph nodes.

• Lymphatic trunks: larger vessels carrying lymph to ducts.

• Lymphatic ducts: main conduits returning lymph to the bloodstream.

• Key Structures:

• Right lymphatic duct drains the right upper body.

• Thoracic duct drains the rest of the body into the left subclavian vein.

Lymph Transport & Lymphedema

• Lymph transport is aided by:

  • Respiratory pulsations

  • Transmural pressure differences

  • Smooth muscle contractions in lymphatic vessels.

• Lymphedema: associated with disrupted flow or blockage in lymphatic vessels, causing fluid accumulation.

Lacteals

• Specialized lymphatic vessels in the intestine:

• Function: Absorb dietary fats and fat-soluble vitamins.

• Found in the duodenum, jejunum, and ileum of the small intestine.

Lymphoid Cells

• Components of the lymphatic system include:

• Macrophages: engulf pathogens and debris.

• Reticular cells: provide structure in lymphoid tissues.

• Lymphocytes: B cells and T cells, key players in adaptive immunity.

• Dendritic cells: present antigens to T cells to initiate immune response.

Lymph Nodes

• Structure:

• Cortex: Contains lymphoid follicles and germinal centers for lymphocyte proliferation.

• Medulla: Medullary cords provide a pathway for lymphatic flow; fewer efferent vessels.

• Function: Filter lymph; sites for immune responses and lymphocyte activation.

Spleen

• Major organ for cleansing blood, involving:

• Red pulp: filters blood, removes old red blood cells.

• White pulp: site for lymphocyte activation.

• Structure includes: Trabeculae, splenic cords, and sinusoids.

Mucosa-Associated Lymphoid Tissue (MALT)

• Comprises lymphoid tissue in mucosal membranes:

• Important in protecting openings to the outside world (e.g., intestines, respiratory tract).

• Tonsils, Peyer's patches are examples of MALT regions.

Summary of Lymphoid Organs and Tissues

Major Functions and Features

• Lymph Nodes:

  • Cleanse lymph, site of lymphocyte activation.

  • Capsule, medulla, cortex structures present.

• Spleen:

  • Cleanses blood, stores platelets, activates lymphocytes. Red and white pulp present.

• MALT:

  • Protects mucous membranes, prevents pathogen entry, lymphocyte activation occurs.

• Thymus:

  • Site of T-cell maturation, characterized by a fibrous capsule and cortical structures.