Lymphatic System & Immunity

Covers Ch 17 in HOLE'S HUMAN ANATOMY & PHYSIOLOGY 12th edition
Lymphatic System
Transports excess fluid to the bloodstream, absorbs fats, and helps defend the body against disease causing agents.
Lymphatic Capillaries
Microscopic, closed-ended tubes that extend into the interstitial spaces. They receive tissue fluid through their thin walls. Lacteals are lymphatic capillaries in the villi of the small intestine.
Lymphatic Vessels
Lymphatic vessels are formed by the merging of lymphatic capillaries. They have walls similar to veins, but the walls are thinner, and valves that prevent backflow of lymph. Larger vessels lead to lymph nodes and then merge into lymphatic trunks.
Lymphatic Trunks
Lymphatic trunks drain lymph from large body regions. Trunks lead to two collecting ducts-the thoracic and right lymphatic ducts. Collecting ducts join the subclavian veins.
Tissue Fluid formation
(a)Tissue fluid originates from plasma and includes water and dissolved substances that have passed through the capillary wall. (b) Tissue fluid generally lacks large proteins, but some smaller proteins are filtered out of blood capillaries into interstitial spaces. (c) As the protein concentration of tissue fluid increases, colloid osmotic pressure increases.
Lymph formation
Increasing hydrostatic pressure in interstitial spaces forces some tissue fluid into lymphatic capillaries. This fluid becomes lymph. (b) Lymph formation prevents accumulation of excess tissue fluid (edema).
Lymph function
Lymph returns the smaller protein molecules and fluid to the bloodstream. (b) It transports foreign particles to the lymph nodes.