1/19/2018 1 Lymphatic System and Immunity Anatomy & Physiology-Honors Turner College & Career High School Lymphatic System • One way system: to the heart. • Return of collected excess tissue fluid. • Return of leaked protein. • “Lymph” is this fluid. • Edema results if system blocked or surgically removed. Lymph Capillaries • Have one way mini valves allowing excess fluid to enter but not leave. • Picks up bacteria and viruses as well as proteins, electrolytes and fluid(lymph nodes destroy most pathogens). Lymphatic System • Lymph capillaries o Absent from bone, bone marrow, teeth, CNS. o Enter lymphatic collecting vessels. • Lymphatic collecting vessels o Similar to blood vessels (3 layers), but thin & delicate. o Superficial ones in skin travel with superficial veins. o Deep ones of trunk and digestive viscera travel with deep arteries. o Very low pressure. o Distinctive appearance on lymphangiography. o Drain into lymph nodes. • Lymph nodes: bean shaped organs along lymphatic collecting vessels. • Up to 1 inch in size. • Clusters of both deep and superficial LNs. 6
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1/19/2018
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Lymphatic System and ImmunityAnatomy & Physiology-HonorsTurner College & Career High School
Lymphatic System
• One way system: to the
heart.
• Return of collected
excess tissue fluid.
• Return of leaked protein.
• “Lymph” is this fluid.
• Edema results if system
blocked or surgically
removed.
Lymph Capillaries
• Have one way mini valves
allowing excess fluid to enter but not leave.
• Picks up bacteria and viruses as
well as proteins, electrolytes and fluid(lymph nodes destroy most pathogens).
Lymphatic System
• Lymph capillaries
o Absent from bone, bone marrow, teeth, CNS.
o Enter lymphatic collecting vessels.
• Lymphatic collecting vessels
o Similar to blood vessels (3 layers), but thin & delicate.
o Superficial ones in skin travel with superficial veins.
o Deep ones of trunk and digestive viscera travel with deep
arteries.
o Very low pressure.
o Distinctive appearance on lymphangiography.
o Drain into lymph nodes.
• Lymph nodes: bean shaped organs along
lymphatic collecting vessels.
• Up to 1 inch in size.
• Clusters of both deep and superficial LNs.
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Functions of Lymphatic System
1. Draining interstitial fluid.
2. Transporting dietary lipids.
3. Protection.
Lymphatic Vessels
• Begin as closed ended lymph capillaries in tissue
spaces between cells.
• NOT A CIRCULATING FLUID.
• Interstitial fluid drains into lymphatic capillaries, forming lymph.
• Lymph capillaries merge to form lymphatic vessels.
• Lymphatic vessels carry lymph into and out of
lymph nodes.
• And finally back to the vascular system.
Lymphatic Capillaries
• Made of a single layer of squamous
epithelial cells.
• Slightly larger than blood capillaries.
• Cells overlap and act as one-way valves.
• Opened by pressure of interstitial fluid.
• Anchoring filaments attach cells to
surrounding tissue.
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Lymphatic Vessels
• Resemble veins (same 3 layers).
• Found throughout body except:
oAvascular tissues.
oCentral nervous system.
o Splenic pulp.
o Bone marrow.
Lymphatic Vessels
• Lymphatic vessels join to form lymphatic
trunks.
• Lymphatic trunks join to form :
o Thoracic duct (3/4 of body).
o Right lymphatic duct (drains right arm, and right
side of head, neck and upper torso).
• These empty into subclavian veins at
junction with internal jugular vein.
Formation of Lymph
• Fluid leaves capillaries by diffusion and
filtration.
• Escaped proteins.
• If lymph flow blocked = tissue swelling or
edema.
• Specialized lymphatic capillaries in vili of
small intestine transport lipids - they are
called lacteals, and the fluid is called chyle.
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Lymphatic Organs
• Red bone marrow
• Thymus gland
• Lymph nodes
• Lymph nodules Secondary organs
• Spleen
Primary organs
Lymph Nodes
• Lymph is filtered through lymph nodes.
• Found in clusters.
• “Waste water treatment plants”.
• Vary in size.
• Principal groupings in cervical, axillary and
inguinal regions.
• Provide biological filtration.
• Site of cancer growth and metastasis.
• Vessels enter node on convex side.
• Lymph passes through irregular channels called sinuses.
• Leaves node through one or two efferent
vessels at the hilum or hilus.
• Capsule, cortex and medulla.
• Cortex contains lymph nodules.
• Follicular dendritic cells.
• Germinal centers – B cells proliferate.
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Lymph Nodules
• Lymph nodules are also found singly or in groups throughout the mucous membranes of
the respiratory, urinary, reproductive and digestive tracts.
• MALT – mucosa associated lymphoid tissue.
• Peyer’s patches in ileum.
• Tonsils.
• Some in appendix.
Development of Lymphocytes
• Originate in bone marrow from lymphoid stem cells
• B cells stay in bone marrow, hence “B” cells
• T cells mature in thymus, hence “T” cells
• These divide rapidly into families
• Each has surface receptors able to recognize one