- Slides: 12
Chapter 22 The Lymphatic System and Immunity
The Lymphatic System • A system consisting of lymphatic vessels through which a clear fluid (lymph) passes • The major functions of the lymphatic system include: • Draining interstitial fluid • Transporting dietary lipids absorbed by the gastrointestinal tract to the blood • Facilitating the immune responses
The Lymphatic System • Components of the lymphatic system include: • Lymphatic capillaries • Lymphatic vessels • Lymph nodes • Lymphatic trunks • Lymphatic ducts • Primary lymphatic organs • Secondary lymphatic organs and tissues
Lymphatic Vessels and Fluid • Lymph is a clear to milky fluid in the extracellular fluid compartment. Extracellular fluids include: • Plasma – the liquid component of blood • Interstitial fluid – the clear fluid filtered through capillary walls when it enters the “interstitium” (space between cells, also called the intracellular space) • Lymphatic fluid – the unaltered interstitial fluid that enters the lymphatic vessels. In the GI tract, lymphatic fluids also include absorbed dietary lipids.
Lymphatic Vessels and Fluid • The flow of lymph fluid is always from the periphery towards the central vasculature. • It starts as interstitial fluid. • Then enters lymphatic capillaries. • It travels in lymphatic vessels to the regional lymph nodes…
Lymphatic Vessels and Fluid • The flow of lymph fluid continued… • Lymph ascends or descends to the thorax, either to the Left or Right Lymphatic Duct. • Lymph fluid’s final destination is the bloodstream, as it enters through the Subclavian veins.
Lymphatic Vessels and Fluid • Lymphatic capillaries are slightly larger than blood capillaries and have a unique one-way structure. • The ends of endothelial cells overlap and permit interstitial fluid to flow in, but not out. • Anchoring filaments pull openings wider when interstitial fluid accumulates. • There are specialized lymphatic capillaries called lacteals that take up dietary lipids in the small intestine. • Chyle is the name of this “lymph with lipids”.
Lymphatic Vessels and Fluid Lymphatic capillaries showing blind ends and one way flow
Lymphatic Vessels and Fluid • Lymphatic capillaries unite to form larger lymphatic vessels which resemble veins in structure but have thinner walls and more valves. • Lymphatic vessels pass through lymph nodes – encapsulated organs with masses of B and T cells. • Function as lymph filters
Lymphatic Vessels and Fluid
Lymphatic Vessels and Fluid • Lymphatic fluid is moved by pressure in the interstitial space and the milking action of skeletal muscle contractions and respiratory movements. • An obstruction or malfunction of lymph flow leads to edema from fluid accumulation in interstitial spaces.
Lymphatic Organs • The lymphatic system is composed of a number of primary and secondary organs and tissues widely distributed throughout the body - all with the purpose of facilitating the immune response.