Phys- Lymphatic Function Flashcards
Extravascular circulation is carried out by what system
Lymphatic System
Where are lymphatic vessels found
throughout the body EXCEPT: BRAIN, BONE, SKIN
composition of lymphatic vessels
single layer of endothelial cells WITHOUT a basement membrane
anchoring filaments
loosely teather lymphatic vessels to surrounding tissue
lymphatic function
maintain interstitial homeostasis
describe the endothelial cells of lymphatic vessels
overlaping edges (rather than tight junctions) form valves that allow movement of water and solutes into the terminal lymphatics
where do lymphativ vessels originate
at the capillary bed
describe what happens to lymph vessels when interstitial volume increases
tension on anchoring flilaments increases and pulls open the spaces between the endothelial cells lining the terminal lymphatics. This allows fluid and solutes to enter the terminal lymphatics. This allows fluids and solutes to flow into the lymphatics and lymphatic capillaries then back into central circulation
can lymphatic vessels contract?
yes- contain smooth muscle in their walls - act like small beating hearts - (as lymph moves segment to segment pressure increaeses in the adjacent segment (increased preload) causing stretch which increaes both the rate and the fource of the contraction and lymph is propelled alon the lymphatic channel)
Influence of movement and tissue compression on lymph flow
increases flow in a unidirectional manner (due to valves)
After dumping into the throacic duct or the right lymphatic duct lymph returns to ______
systemic circulation (recycle fluid and protein)
what is lymph?
fluid that was filtered but not absorbed at the tissue level (net filtration)
Lymph node purpose
filter out particulate matter and bacteria picked up from the interstitium so that it does enter systemic circulation
To maintain equilibrium, lymph flow must equal what
the net fluid filtration throughout the body (~3L/day)
Why is lymph flow important
1.) Maintain dry interstitium (removal of water) 2.) Maintain low interstitial oncotic pressure (picks up plasma proteins that have leaked into the interstitium) 3.) Defense against increased net fluid filtration by maintaining subatmospheric Pi (creates partial vaccum that helps hold tissues together) 4.) Cleansing of the interstitial compartment (collects particulate matter and bacteria) 5.) Absorption of fats (chylomicrons)
Relationship between increased Pi and Lymph flow
any factors that increase Pi (interstitial hydrostatic pressure) will increase lymph flow
at Pi ~0mmHg how much has lymph flow increased
15 fold (remember Pi normally sits right around -6 and anything that increases Pi will increase lymph flow
Intrisic contractions and lymph flow
increased intramural pressure cause intrinsic myogenic contraction sof the smloth muscle in the walls of the lymph vessel which “pumps” lymph form segment to segment (think of it as an increase in preload)
Extrinsic influences on lymph flow
sympathetic activation and increases in circulating NE cause increases in lymph flow
Lymphatic pump
increasesin Pi and intersitial fluid volume open terminal lymphatics allowing the entry of fluid and solutes into the terminal lymphatics and increasing lymph flow. Tissue compression pushed the contents into the next segment (emptying into terminal lymphatic. Release of teh compression stretches the anchoring filaments and opens the terminal lymphatics again
External Compression massage and lymph
external tissue pressure compresses lymph channels (movement, muscle contraction, respiration, intestinal contractions, tissue massage or manipulation) propels lymph along the channels . HOWEVER: excessive compression (tight clothing or bands) can impede lymph flow and lead to distal tissue expansion
Respiratory Movements (Thoracic Lymphatic Pump Technique- OMT)
transiently lower intra-thoracic pressure during insiration and increase lymph flow
What is edema
presence of excess fluid in the tissues
What causes edema
anything that alters the balance of Starling Forces leading to an increased net filtration OR anything that creates an imbalance between the rate of fluid filtration and the capacity to increase lymph flow