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Overview of Lymphatic System
- a net work of vessels -aid in circulation of body fluids -
closely associated with cardiovascular system, runs side by
side with capillaries - include lymph vessels, lymph tissues,
lymph organs
TERM 2
Lymphatic System function
DEFINITION 2
-defense mechanism; produces, maintains, distributes
lymphocytes -maintains normal blood & interstitial fluid
volume -transports extra fluid away from cells, puts it back
into blood stream -provides an alternate route for the
transport of materials, nutrients, & wastes -provides an
alternate route for hormones
TERM 3
Lymphatic Vessels
DEFINITION 3
-a network of vessels -transport fluid called lymph -range in
size; small lymphatic capillaries, medium lymphatic vessels,
large lymphatic trunks, lymphatic ducts - always associated
with blood vessels - in most tissues, absent in avascular
tissues & CNS
TERM 4
Lymph
DEFINITION 4
- fluid CT - only found in lymphatic vessels - derived from:
interstitial fluid, lymphocytes, macrophages
TERM 5
Origin of lymph
DEFINITION 5 -tissue fluid formation: -originates from blood plasma - made of water & dissolved materials - leaves blood due to diffusion & filtration - lacks protiens & has a lower O2 concentratation - about 27L/day enters interstitial space -lymph fluid: -90% of interstitial fluid reabsorbed -enters lymph capillaries & becomes lymph-
lymphatics-> venous system
lymph capillaries
-closed ended tubes, form complex networks: parallel to blood capillaries -single layer of squamous epithelium, with incomplete basal lamina -cells overlap, fenestrated -differ from blood capillaries -larger diameter, thinner wall, flat & irregular -anchoring filaments to keep the passage open, overlapping endothelial cells - formation of lymph: -cells in wall of lymph capillaries overlap: function as 1-way valve -moves through fenestrations; larger things (viruses) don't follow TERM 7
Lymphatic Vessels
DEFINITION 7
-formed by merging of lymph capillaries - wall similar to
veins; has all the tunicas -larger vessels lead to lymph nodes
-> merge to larger vessels or trunks -travel side by side with
arteries or veins of the same size
TERM 8
Lymphatic Trunks & Collecting
Ducts
DEFINITION 8 -lymphatic trunks: drain larger regions of the body, named for the region they drain (ex. Subclavian, lumbar, intestinal, jugular) -collecting ducts: deliver lymph to venous circulation (becomes part of plasma) -thoracic duct: drains lower body, left arm, left side of head & neck -arises in abdomen from cisterna chyli->diaphragm->ascends in front of vertebral column->empties in left subclavian vein -right lymphatic duct: drains right side of head, neck & right arm; -arises in right thorax->right subclavian vein -lymph joins blood & becomes part of the plasma before blood returns to the right atrium TERM 9
Movement of lymph
DEFINITION 9
-unidirectional -contain valves to prevent back flow -pressure
is lower in veins -lymph is moved using similar methods to
veins (skeletal & breath) -muscle contraction -pressure
gradients -valves -may cause edema is drainage does not
occur
TERM 10
Lymphocytes
DEFINITION 10
-main cells of lymphoid system -immune response to foreign
antigen's - originates in the blood stream->peripheral
tissues->lymph (for hours of years)->returns to bloodstream
lymph node
-clustered along large veins, bean shaped, 2.5 centimeters in size -hilum: indented region where BV's & nerves connect, efferent lymph vessels enter; covered with capsule of fibrous CT -within the capsule nodules (structural unit of node): -separated by trabeculae; outer cortex: mainly B-Cells; inner cortex (mainly T-Cells); medulla (B-Cells leave via efferent vessel) -sinuses: spaces within the node where lymph circulates -cervical, axillary, inguinal, pelvic, abdominal, thoracic -purifies lymph via T-Cells, B-Cells, & macrophages, initiate immune response, helps defend against harmful substances TERM 17
Spleen
DEFINITION 17
-found on the left side of the stomach, is the largest
lymphatic organ -capsule -white pulp: resembles lymph node
-red pulp: large amount of RBC, has sinuses filled with
macrophages, T & B-Cells -removes old blood cells,
stores/recycles iron, initiates immune responses, blood
reservoir, assists in red blood cells production
TERM 18
Thymus
DEFINITION 18 -in mediastinum; 1st lymph organ to develop -grows into puberty; shrinks with age; replaces by fibrous tissue -develops from 2 glands -septa divides lobes into lobules -lobules -cortex: immature T-Cells (90%), reticular epithelial cells (10%) -medulla: immature T- Cells(10%), reticular epithelial cells (90%), produces the hormone thymosin (causes T-Cells to mature) -T-Cells production: pro lymphocyte->cortex: produces T-Cells->medulla matures-
postcapillary venules->lymphoid tissues/organs TERM 19
Blood-Thymus Barrier
DEFINITION 19
-Prevents antigen;s from stimulating undifferentiated T-Cells
protecting them until they are mature
