The Lymphatic System “the body’s drains”

Principle Organs/Tissues Lymph (lymphatic fluid) Lymphatic vessels Lymph nodes (glands) Tonsils Thymus Spleen Peyer’s patches

Principle Functions Fluid balance (returns water, proteins, etc. from tissues back to blood) Immunity Transports lipids from the digestive tract Lacteals (lymph capillaries) in intestine transport fatty lymph called chyle

What does the lymphatic system do? As blood circulates small amounts of fluid gets left behind in tissues If allowed to build up this could cause edema(swelling) Lymph vessels collect fluid and return it to veins

Lymph Interstitial fluid is fluid which surrounds cells Once it drains into lymph vessels it is called lymph Lymph is clear and watery

Lymphatic Capillaries Lymphatic vessels begin as “blind end” vessels called lymphatic capillaries Those originating in the small intestines are called lacteals All lymph vessels drain into either the thoracic duct or right lymphatic duct.

Structure of Lymphatic Vessels Vessels have thinner walls than veins (same tunicas as veins) Contain many valves, giving them a beaded appearance lymph nodes present at certain intervals Small openings between endothelial cells allow for high permeability to large substances

Circulation of Lymph Solutes and water constantly leak out of capillaries into interstitial fluid These are reabsorbed by lymph vessels and returned to blood Lymphatic vessels absorb excess fat preventing increased viscosity of blood

Lymphatic Pump Lymph is kept moving by two (lymphokinetic)actions –Breathing –Skeletal muscle movement Inspiration causes intraabdominal pressure while decrease thoracic pressure allowing lymph to move up thoracic duct Other factors that increase lypmh flow –Physical activity –Postural changes –Massage –Arterial pulsations

Structure of Lymph Nodes Lymph nodes are biological filters Fibrous trabecula created sinuses where fluid “percolates” Sinuses are lined with recticuloendothelial cells that are capable of phagocytosis

Major Lymph Node Locations Preauricular- located in front of ear Submental and submaxillary- floor of the mouth Superficial cervical- in the neck Superficial cubital, supratrochlear- above bend in elbow Axillary- underarm and chest Inguinal- groin

Functions of Lymph Nodes Filtration and Phagocytosis –Cells phagocytose microorganisms and other foreign particles –During infections nodes become swollen and tender, called adenitis –Tumors can block flow causing edema Hematopoesis –Maturation of some lymphocytes and monocytes occur in lymph nodes Role of a lymph node in a skin infection. Yellow areas represent dead and dying cells (pus). Black dots around the yellow areas represent bacteria.

The Tonsils Are a mass of lymphoid tissue First line of defense against infection The pharyngeal tonsils are called adenoids pharyngeal palatine lingual

The Thymus Located above the heart Plays a role in lymphocyte development Releases thymosin that helps in T cell maturation

The Spleen Located above the left kidney behind the stomach Functions –Defense- phagocytosis of microorganisms –Hematopoesis- monocytes and lymphocytes maturation –Red blood cell and platelet destruction, hemoglobin is recycled –Blood Reservoir