Lymphatic System and Body Defense Chapter 16

Lymphatic System Lymphatic system consists of lymphatic vessels, lymphatic organs and associated lymphoid tissue Functions contribute to homeostasis Helps defend body against disease Lymphatic capillaries take up excess tissue fluid and proteins , and return it to bloodstream Lacteals receive lipoproteins and transport them to bloodstream.

Lymphatic Organs Thymus Lymph nodes Spleen

Major Organs of Lymphatic System

Lymphatic System

Lymphatic Capillaries Microscopic Closed-ended tubes with flap like valves Found in interstitial spaces of most tissues Attached via proteins to surrounding connective tissue remain open Closely associated with the circulatory system

Lymphatic Vessels One-way system that carry lymph Valves prevent backflow Lymphatic capillaries absorb excess fluid

Lymph - fluid in lymphatic system Lymph Function Lymphatic capillary Interstitial spaces Lymph - fluid in lymphatic system Increasing hydrostatic pressure within interstitial spaces forces tissue fluid into lymphatic capillaries This process prevents accumulation of excess tissue fluid or edema

Lymph Movement respiratory movements action of skeletal muscles respiratory movements smooth muscle in larger lymphatic vessels valves in lymphatic vessels

Lymph Nodes Macrophages and lymphocytes Filter potentially harmful particles from lymph Areas of lymphocyte production

Obstruction of Lymph Movement Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Conditions that interfere with lymph movement Fluid to accumulate in interstitial spaces Results in edema Lymphatic vessels Lymph node Muscle Blood vessels © Dr. Kent M. Van De Graaff

Spleen Largest lymphatic organ Function Protection from pathogens, removes aged RBC recycles Fe Blood , platelets, monocyte reservoir Fetal blood cell production but not after birth

Spleen Contains two tissue types White pulp lymphocytes Immune functions Red pulp Red blood cells Lymphocytes Macrophages Worn out RBC and pathogens are destroyed

Thymus Secretes thymosins Site of T lymphocyte maturation Shrinks with age

Mucosa-Associated Lymphoid Tissues (MALT) Peyer’s Patches Lymphoid follicles in appendix Tonsils of the pharynx and oral cavity Follicles in urogenital and respiratory tract They prevent pathogens in these passages from penetrating mucous membranes

Diseases of the Lymphatic System Lymphatic filariasis Facts from WHO Nearly 1.4 billion people in 73 countries worldwide are threatened by lymphatic filariasis, a parasitic infection that leads to a disease commonly known as elephantiasis. Over 120 million people are currently infected, with about 40 million disfigured and incapacitated by the disease. http://www.cdc.gov/parasites/lymphaticfilariasis/ .