Lymphatic System

Two parts:

  1. Cellular component - lymphatic tissue found on all organs and lymph nodes

  2. Vascular component – lymph vessels and lymph duct system

For Immune response:

  1. Fixed cells found on lymphoid organs

  2. Mobile cells that circulate (Lymphocytes, Monocytes, and Plasma cells)


The system of ducts picks up some of the fluid leaked from the capillaries into interstitial tissue

  • Lymph

  • Osmotic pressure

  • Lymph vessels do not have muscles

  • Thoracic duct


  • Lymph from the digestive system is called Chyle

  • White or pale yellow and cloudy

  • Postprandial lipemia

  • Cisterna chylii

Thymus

  • Production of Mature T cells from pre-cursors sent from the Bone marrow.

  • Stimulates a cell-mediated immune response

  • Largest when an animal is young, but shrinks and is replaced by fat as the animal matures

  • Cortex contains a large number of lymphocytes

Bone Marrow

  • Contains immature cells called Stem Cells (which can differentiate into RBC’s, WBC’s, or Platelets)

  • Mesenchymal and Hematopoietic

  • Hematopoietic stem cells gives rise to two main type of cells: Myeloid lineage and Lymphoid lineage

Secondary Lymphoid Organs

  • Main Function is to trap and process antigens and mature lymphocytes that mediate immune responses

Lymph Nodes

  • Small, kidney bean-shaped filters located at various points along lymphatic vessels.

  • Has a cortex and medulla which has lymphatic sinuses running through it

  • Afferent and Efferent Vessels

  • Nodules located on the Cortex are made up predominantly B cells, although T cells and macrophages are also found in smaller numbers

Spleen

  • Tongue-shaped organ located on the left side of the abdomen

  • Filters blood and lymph

  • Trabeculae

  • White Pulp and Red Pulp

  • White Pulp

    • formed of localized areas of lymphoid tissue

  • Red Pulp

    • contains blood vessels, tissue macrophages, and blood cell storage spaces called sinuses

  • Tissue macrophages filter out antigens and other foreign material from the lymph and remove dead, dying, and abnormal red blood cells

  • Acts as reservoir for blood when the animal is at rest

Tonsils

  • Nodules of lymphoid tissues that are not covered with a capsule

  • Found in epithelial surfaces all over the body

  • Prevent the spread of infection into the respiratory and digestive system

Blood

  • Supplies body tissues with oxygen, nutrients, and various chemicals

  • Blood transports waste products to various organs for removal from the body

  • Immune and Endocrine system

  • Buffy Coat

B lymphocytes

  • Produced and mature in the bone marrow

  • Differentiate into Plasma cells and Memory B cells

  • Immunoglobulins or Ig

T lymphocytes

  • Produced by the bone marrow and matures in the Thymus

  • Coordinate immune defenses and kill organisms on contact

Types of T cells