A&P2-Ch21.1-3

Chapter 21: Anatomy of the Lymphatic and Immune Systems

Overview

• The lymphatic system consists of vessels, cells, and organs that manage fluid levels, filtering pathogens from the blood and returning excess fluids to the bloodstream.

• The immune system is a complex network that attacks and neutralizes pathogens to prevent disease.

21.1 Structure and Function

• Lymphatic tissue components:

  • Lymph fluid: Interstitial fluid within the lymphatic system.

  • Lymphatic vessels: Transport lymph to larger lymphatic ducts.

  • Organs: Include various lymphatic and immune organs that facilitate immune responses.

Functions of the Lymphatic System

• Main functions:

  • Drains body fluids back to the bloodstream.

  • Transports immune system cells.

  • Carries dietary lipids and fat-soluble vitamins.

• Lymph: Interstitial fluid once within the lymphatic system.

Anatomy of Lymphatic Vessels

• Capillaries: Open-ended vessels where interstitial fluid enters.

• Vessel structure: Similar to veins, with three tunics and valves.

• Trunks and Ducts:

  • Include right lymphatic duct and thoracic duct, draining lymph into subclavian veins.

Immune Function Organization

• Phases of Immune Response:

  • Barrier defenses: Skin and mucous membranes provide immediate protection.

  • Innate immune response: Quick, non-specific response involving various specialized cells.

  • Adaptive immune response: Slower but specific, managed primarily by lymphocytes.

Blood Cells in Immunity

• Classes of blood cells:

  • Phagocytic cells: Ingest and destroy pathogens.

  • Lymphocytes: Coordinate adaptive immunity.

  • Granule-containing cells: Target parasites and some viruses.

Lymphocytes

• Types:

  • B cells: Activated to produce antibodies.

  • T cells: Different types mediate immune responses or destroy infected cells.

  • Natural Killer (NK) cells: Attack viruses and cancer cells, acting as first responders.

Primary and Secondary Lymphoid Organs

• Primary Organs:

  • Bone marrow: Site of hematopoiesis and B cell maturation.

  • Thymus: Supports T cell maturation.

• Secondary Organs:

  • Lymph Nodes: Filters lymph, contains germinal centers for B cell activation.

  • Spleen: Filters blood, presents antigens to lymphocytes.

  • Tonsils and MALT (Mucosa-associated lymphoid tissue): Localized immune responses in various tissues.