Lymphatic System

Lecture Vid and Supplement

Lymphatic Circulation

• drains tissue fluid

• prevents edema (swelling)

• filters lymph

• returns clean lymph to circulation at junction of subclavian and jugular veins to the bloodstream

  • returns tissue fluid to plasma for recirculation, this fluid (lymph fluid) is filtered before returning to the venous system

Lymph Capillaries

• pick up extra fluid and bring it back to the circulatory system

• goes through a series of small vessels

• as it is drained it goes through lymph nodes

• terms

  • plasma in capillaries

  • interstitial fluid in extracellular space

  • lymph in a lymph vessel

Lymph Nodes

• filtration stations that filters lymph so it is just the same as plasma when it reenters circulation

• primary site for WBC differentiation

• bean shaped organs located along the length of lymphatic vessels

• found clustered in specific regions of the body

• help squeeze lymph cells toward antigenic targets by allowing it to see the filtration of lymph

• these vessels are like veins with valves pushing back to the junction between subclavian and jugular vein

Lymph Node Anatomy

consists of

• afferent lymphatic vessel

• efferent lymphatic vessel

• hilum (exit point)

• covered by a fibrous capsule with an

  • outer cortex

  • medulla

• extensions of fibrous capsule

Extensions of fibrous capsule

divides the node into many sinuses along which lymphocytes and microphages are arranged

• as lymph flows through

• macrophage remove foreign material and cellular debris while lymphocytes are brought into antigens

• filtering lowkey

______ lymphatic vessel enter on the convex surface of the node and usually a single large _____ lymphatic vessel exits at the indentation of the ____

afferent, efferent, hilum

Lymphatic System

• we see a series of tubes starting with lymph capillaries that are spread throughout tissues and they all lead to the junction between the subclavian and jugular vein

• thoracic duct is the largest

  • this duct collects drainage from everything below the diaphragm and the left side of the body

Spleen

• largest mass of lymphoid tissue in the body

• surrounded by capsule composed of elastic CT and myoepithelial cells

• rids blood of cellular debris and bacteria

  • filters BLOOD not lymph giving its bloodlike color

• stores blood in its sinuses until its needed

  • can contract via sympathetic stimulation

  • shrinks in emergency situations to supply the body with more blood

• stores platelets and iron

• site of RBC production in fetus

• sits on outer ridge of stomach

• hilus is where blood vessels come in and out of organ

Cisterna Chyli

• at the beginning of the thoracic duct

• gets large due to most of lymphatic drainage of intestines running through here

Axillary lymph

• runs through upper right arm

Accumulation of lymph

• endothelial cell (simple squamous)

• has a basement membrane and when it tapers off into cordlike tissues are filaments that anchor it to the cell

• at tip of the cell it overlaps with the next cell and as lymph accumulates it will pull the flaps open allowing lymph to enter

• lymph enters from tissue to lymphatic vessel

• is a self-regulatory valve, will close on its own

Lymphatic Vessels

• one way circulation which returns tissue fluid, protein, fat, and blood cells to venous circulation

• have semilunar valves to prevent back flow

  • ultimately drain back into veins in chest

  • lymph is pumped mainly by skeletal muscle pumping (similar to veins)

  • two largest vessels are the right lymphatic vessel and the thoracic duct return lymph to circulation by dumping lymph in junction of subclavian and jugular veins

• as vessels increase in size, flow increases too

• are one way valves and can only go forward

Lymph Nodes filters lymph…

• afferent lymphatic vessels bring fluid toward lymph node

• fluid percolates through tissues of lymph and exits through hilus

  • hilus is the indentation of the organ and is the ext point and where efferent lymphatic vessels are

• has an outer cortex and medulla (central portion)

• as lymph enters, goes through a series of channels to get to the cortex and may develop lymphatic nodules with a geminal center

Nodule

a camp of WBC with T-cell accumulation

Outer Cortex

• contains areas of lymph nodules

  • densely packed lymphocytes (WBCs and T cell accumulation)

• center of cortex is where lymphocytes are produced

• germinal center

Medulla

B cell dominated and manufactures antibodies as WBC’s are exposed to target

Thymus

• bi-lobed mass of lymphatic tissue which functions to produce plasma cells capable of fighting invading microbes

• attains max size at puberty and then is replaced by fat and CT in the adult

• organ that sits on top of the heart

• T cells train here, B cells train bone marrow

T cells

• grow and train in thymus

• warrior cells that kill enemy and have a particular target in mind

• will pop open holes in target cell membrane

• reside here so they know to not attack your own cells

• 3 types

  • destroy, ignore, or see it and let it pass *

• mostly trained in cortex, when trained go to center of organ (medulla) and leave via blood vessels

Hassall’s corpuscle

• thymic cell death zone and create circular graves

Tonsils

• masses of lymphoid tissue embedded in mucus membrane

• useful in surveillance functions

• membrane has crypts that go down to the organ where tissue is exposed to incoming things

• active lymphatic nodules seen here

• ring of tonsils: lingual, palatine, pharyngeal

  • palatine and pharyngeal can swell and are the ones removed

Internal Spleen

• composed of white pulp (lymphoid tissue) and red pulp (venous sinuses)

• red pulp is where capillary bed is open and sinusoidal

• white pulp is an accumulation of WBCs

• capsule is thick with abundant elastic CT and contracts

• tightens up during emergencies, forcing blood into circulation

• can live w/o this

• under lower ribs