Memmler’s The Human Body in Health and Disease 11th edition Chapter 16 The Lymphatic System and Lymphoid Tissue

The Lymphatic System System of tissues and vessels Scattered throughout the body Services almost all regions Only CNS, bone and cartilage, and epithelium do NOT have contact

Functions of the Lymphatic System Fluid balance (picks up excess fluid and protein) Lymph fluid Protection from infection (lymphocytes live and multiply here) Absorption of fats (ones too large to enter capillaries)

The lymphatic system in relation to the cardiovascular system The lymphatic system in relation to the cardiovascular system. Lymphatic vessels pick up fluid in the tissues and return it to the blood in vessels near the heart.  

Lymphatic Circulation One-way system (not a complete circuit) Begins in tissues Ends in bloodstream

Lymphatic Capillaries Capillary walls (endothelium) are flattened epithelial cells Travels and follows capillaries More permeable than blood capillaries Overlapping cells form one-way valves Arise blindly (closed at one end) Lacteals (found in small intestine) absorb digested fats

Lymphatic Vessels Superficial sets Deep sets Nodes Right lymphatic duct (bodies superior right quadrant) Thoracic duct (all other body parts) Cisterna chyli – enlarged part to store chyle Chyle – milky fluid that drains from intestinal lacteals Look on pg. 353 for structure

Vessels and nodes of the lymphatic system Vessels and nodes of the lymphatic system. (A) Lymph nodes and vessels of the head. (B) Drainage of right lymphatic duct and thoracic duct into subclavian veins.

**** moves the same way as venous return Movement of Lymph Segments of vessels located between the valves contract rhythmically Skeletal muscles compress vessels **** moves the same way as venous return

Lymphoid Tissue Distributed throughout the body Makes up specialized organs of lymphatic system

Lymph Nodes Structure - Fibrous connective tissue capsule Function Filter antigens and foreign bodies Grouping Cervical nodes Axillary nodes Mesenteric nodes Inguinal nodes

Structure of a lymph node Structure of a lymph node. (A) Arrows indicate the flow of lymph through the node. (B) Section of a lymph node as seen under the microscope (low power). (B, Reprinted with permission from Cormack DH. Essential Histology. 2nd ed. Philadelphia: Lippincott Williams & Wilkins, 2001.) 

The Spleen (gland and organ) Cleanses blood Filtration Phagocytosis Destroys old red blood cells Produces red blood cells before birth Is reservoir for blood Has an unusually large supply of blood Houses phagocytes and lymphocytes

The Thymus Plays key role in early immune system development Produces thymosin Develops T lymphocyte cells Promotes lymphocyte growth Promotes lymphoid tissue activity Shrinks after puberty

The Tonsils Remove contaminants and trap pathogens Palatine tonsils (“the tonsils”) - each side of soft palate Pharyngeal tonsil (adenoids) - behind nose/upper pharynx Lingual tonsils - posterior to tongue Surgery to treat if recurrent infection or enlarged tonsils make swallowing/breathing difficult

Other Lymphoid Tissue Appendix Mucosal-associated lymphoid tissue (MALT) Peyer patches Gut-associated lymphoid tissue (GALT)

The Reticuloendothelial System Cells responsible for destroying worn-out blood cells, bacteria, cancer cells and other harmful foreign substances Monocytes – when they enter circulation they are: Macrophages Kupffer cells (lining of liver) Dust cells (lungs)

Disorders of the Lymphatic System and Lymphoid Tissue Lymphangitis – inflammation of the lymphatic vessels Septicemia – blood poisoning resulting from pathogens entering the blood Lymphadenitis – inflammation of the nodes Cervical Chronic

Lymphedema Tissue swelling due to obstruction of lymph flow caused by Infection of lymphatic vessels Vessel blockage Malignant growth Parasites Loss of lymphatic vessels from injury or surgery Elaphantiasis – caused by filariae worm blocking lymph vessel

Lymphadenopathy Enlarged lymph nodes accompany certain diseases (cancer) and infections Acquired immunodeficiency syndrome (AIDS) Infectious mononucleosis

Splenomegaly Enlarged spleen accompanies certain diseases and infections Scarlet fever Typhus fever Typhoid fever Syphilis Tropical parasitic diseases Splenic anemia

Lymphoma Any tumor in lymphoid tissue (benign or malignant) Malignant disease Hodgkin disease Non-Hodgkin lymphoma