Lympathics Flashcards
What are the three components of the lymphatic system?
Lymph fluid, vessels and organized lymphatic tissues/organs (spleen, liver, thymus, tonsils, appendix, visceral lymphoid tissue, LNs)
What is the physiologic function of the lymphatic system?
Major role in numerous homeostatic mechanisms of the body
Immune, digestive, fluid balance, waste
Describe lymphatic development
Begins during 5th week of gestation
Significant presence by 20 weeks
Describe lymphoid tissue during development
Immature at birth
Increases until 6-9 years
At puberty immune system matures but lymphoid tissues slowly degrees until 15-16 years
What is the function of the lymphatic system?
Maintain fluid balance, tissue cleansing/purification defense and nutrition
Describe fluid balance
30 L of fluid move from capillaries to interstitial space each day
90% to venules; 10% to lymphatic system
1/2 of diffused plasma proteins re-enter system via lymph
When fluid overload occurs the lymphatic system helps prevent tissue damage by doing what?
Clearing the excess
Second/third spacing
Describe purification and cleansing
Lymph fluid bathes organs
Cleanses extracellular spaces of particulate matter, toxins, bacteria, cellular waste products and post injury biochemical by products
Fluid then travels via lymphatic vessels -> LN (acts as purifying filter)
Describe the defense function
Lymph fluid brings toxins, bacteria and viruses into contact with the organized lymph tissue (LNs)
Contain high concentrations of immune cells, Ag processing and presentation, maturation of the immune cells -> immunity
Free flow of lymph necessary for appropriate immune function
Describe the nutrition function of lymph
Fat absorption via chylomicrons
Too big to cross capillary intercellular junctions
Travel via lacteals -> larger lymph vessels -> thoracic duct -> venous system
Returns proteins to vasculature
Proteins then bind nutrients
What is lymph fluid?
Substances that leak out of the arterial capillaries into the interstitium get taken up by the lymphatic capillaries (fluids, proteins, electrolytes, and cells)
Immune cells, foreign Ags, bacteria and viruses, clotting factors, chylomicrons post prandial
Which tissues do not have lymphatic vessels?
Epidermis (including hair and nails), endomysium of muscle, cartilage and bone marrow
What is the pathway of lymphatic vessels?
Terminal lymphatics -> collecting vessels -> afferent lymph vessels -> LNs -> efferent lymph vessels -> lymphatic trunks -> thoracic or right lymphatic duct -> venous system
What are terminal lymphatics?
Lymph formation begins in the interstitial space of tissues with initial lymphatics/terminal lymphatic/lymph capillaries
Lined by leaky endothelium anchored to ECM by small filaments
-endothelial cells overlap creating one way valves; lack smooth muscle walls
Terminal lymphatic coalesce into collecting vessels
What are collecting vessels?
Consists primarily of chains of muscular units called lymphangions which posses two leaflet bicuspid valves (lymphatic hearts)
Contract regularly throughout the lymphatic system and moving lymph in peristaltic waves
Contain smooth muscle
Describe LNs
Dispersed along the course of lymph vessels
Two types - superficial (within subcutaneous tissue) or deep (beneath fascia, muscles, organs)
Function: filtration of lymph fluid, maturation of lymphocytes and phagocytosis of bacteria/cellular debris
What is the path of lymph flow through a LN?
Afferent lymphatic -> subscapular space -> outer cortex (B cells)-> deep cortex (T cells) -> medullary sinus -> efferent lymphatics
What are the 5 lymphatic trunks?
Lumbar, intestinal, bronchomediastinal, subclavian and jugular
What do lumbar trunks drain?
Lymph from lower limbs and pelvic organs
What do intestinal trunks drain?
Abdominal viscera
What do bronchomediastinal trunks drain?
Portions of thorax
What does the subclavian trunk drain?
Upper limbs
What does the jugular trunk drain?
Portions of neck and head
What are cisterna chyli?
Located at level of L1-2
Drains lymphatic trunks of the lower body
Gives rise to thoracic duct
Describe the thoracic duct
Origin: cisterna chyli as a dilation at L1-2 level
Termination: pierces Sibson’s fascia at superior inlet, U turns to empty into L subclavian and L internal jugular veins
What is the function of the thoracic duct?
Master lymph vessel and drains L head and neck, LUE, L thorax/abdomen, everything inferior to umbilicus, receives from lumbar lymphatics