1. Lymphatic System Chapter 16

2. Basics Functions –Circulates body fluids Return interstitial fluid to blood stream –Help protect against disease General Pathway –Capillaries  vessels  large vessels in thorax –Capillaries Closed ended tubes Lymph – fluid in capillaries Lacteals – in villi of sm. Intestine  transport fats

3. Basics Lymphatic Vessels –Like veins but thinner walls –3 layers: endothelial lining, smooth muscle, connective tissue –Semilunar valves prevent backflow –Lead to lymph nodes before entering lymphatic trunks Lymphatic trunks and collecting ducts –Drain lymph –Lumbar trunk, intestinal trunk, intercostal and bronchomediastinal trunk, subclavian trunk, jugular trunk –2 collecting ducts: Thoracic duct Right lymphatic duct

4. Tissue Fluid and Lymph Formation –Fluid that leaves circulatory system at capillary beds –Water + dissolved nutrients and gases: no large proteins –Helps resorb small proteins and return back Needed for proper osmotic potential –Transports foreign agents to lymph nodes –Flap-like valves

5. Lymph Movement Osmotic pressure Muscular movement –Breathing Valves force in one direction Edema – swelling –Obstructions preventing lymph movementf

6. Lymph Nodes Expanded, bean shaped organs –Hilum – indented where blood vessels and nerves connect Efferent (leaving) exit at hilus –Nodules – structural unit Actively dividing lymphocytes and macrophages –Locations: Cervical: mandible, neck, behind ears Axillary: underarms, breasts Inguinal: lower limbs, external genitalia Pelvic Cavity: pelvic viscera Abdominal Cavity: mesenteric a. and abdominal aorta; abdomnal viscera Thoracic Cavity: mediastinum, trachea, bronchi; thoracic viscera Supratrochlear Region: medial side of elbow –Function: lymphocyte and macrophage production

7. Thymus and Spleen Thymus –Location: mediastinum, in front of aortic arch, behind the upper part of sternum –Larger in children; shrinks after puberty –T Lymphocytes – provide immunity Thymosin – hormone promotes formation of T lymphocytes Spleen –Location: upper left portion of abdominal cavity; beneath diaphragm, behind stomach –White and red pulp White – nodules Red – red blood cells leave capillaries