The lymphatic system consists of lymph and lymphatic vessels that transport lymph throughout the body. Lymph is interstitial fluid that has entered lymphatic capillaries and contains lymphocytes, macrophages, viruses, bacteria, and cellular debris. The main components of the lymphatic system are lymph, lymphatic vessels, lymph nodes, lymphatic trunks and ducts, and lymphatic tissue. Lymph flows from lymphatic capillaries through vessels, nodes, trunks and ducts and eventually returns to the blood circulation via the subclavian veins. The lymphatic system functions to transport fluids and nutrients, support immune responses, and absorb dietary fats.
3. Learning ObjectivesLearning Objectives
To understand lymph composition & lymph flow
To study function & components of lymphatic system
To study different cells of lymphatic system
To study structure & function of spleen
To describe the anatomy & physiology of lymph node
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Lymphatic SystemLymphatic System
It consists of lymph & lymphatic vessels that
transport the lymph.
After interstitial fluid passes into lymphatic vessels, it
is called lymph
Difference between interstitial fluid & lymph is
location:
Interstitial fluid is found between the spaces of the
cells, & lymph is located within lymphatic vessels &
lymphatic tissue.
7. Lymphatic tissueLymphatic tissue
Lymphatic tissue is a specialized form of reticular
connective tissue that contains large numbers of
lymphocytes.
Lymphocytes are agranular white blood cells
Two types of lymphocytes participate in immune
responses:
B cells
T cells
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FunctionsFunctions
Fluid & nutrient transport
Lymphocyte development
Immune response
Reabsorbs excess interstitial fluid
• returns it to the venous circulation
• maintain blood volume levels
Transport dietary lipids
• Transport lipids & lipid-soluble vitamins (A, D, E, & K)
absorbed by the GI tract.
11. LymphLymph
Fluid present in lymphatic system.
When ISF passes through lymph capillaries it is called as
lymph.
It is then transported through lymph vessels to lymph nodes
From lymph node it is transported to ducts & trunks which
drain lymph to right or left subclavian vein, where it mixes
back with blood.
Clear, colorless fluid
Similar to blood plasma but low protein content
Contain macrophages, viruses, bacteria & cellular debris
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Flow of LymphFlow of Lymph
Lymphatic capillaries
Lymphatic vessels
Lymph nodes
Lymphatic trunks
Collecting ducts
The flow of lymph is regulated by movements of skeletal
muscles & through breathing movements.
This movement compress the lymphatic vessels & force
lymph towards the subclavian veins.
Lymphatic vessels contain one way valve that prevents back
flow of lymph.
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Lymphatic CapillariesLymphatic Capillaries
Microscopic vessels
tiny thin-walled vessels
closed at one end
main purpose is to drain excess
ISF from around the cell to
venous circulation
wall made up of endothelium
larger in diameter
anchoring filaments hold
endothelial cells to the nearby
tissues
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Lymphatic CapillariesLymphatic Capillaries – Lacteals– Lacteals
A lacteal is a lymphatic
capillary present in mucosa of
small intestine
It absorbs dietary fats & lipid-
soluble vitamins from the
small intestine.
Lymph has a milky color due
to the lipid called as Chyle.
17. Lymphatic VesselsLymphatic Vessels
Lymphatic capillaries combines together to form
lymphatic vessels.
Thin walled structures that carry lymph.
Lymph vessels are lined by endothelial cells
Lymph vessels pushes lymph from lymph capillaries
to the lymphatic trunk & ducts
Lymphatic vessels resemble small veins.
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Lymphatic CellsLymphatic Cells
Lymphoid cells
Present in lymphatic system
Elicit an immune response
Types of lymphatic cells are:
Macrophages
Epithelial cells
Dendritic cells
Lymphocytes
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Types & Functions of LymphocytesTypes & Functions of Lymphocytes
T-lymphocytes (T-cells)
B-lymphocytes (B-cells) Types of Lymphocytes
Natural Killer cells (NK-cells)
Migrate through the lymphatic tissues & engulf the micro-
organism (antigens).
Identified according to tissue or organ where they mature:
• T-lymphocytes mature in Thymus
• B-lymphocytes mature in Bone marrow
25. SpleenSpleen
Largest lymphoid organ
Located on the side of
stomach
Hilum: Blood vessels enters
& leaves the spleen
Splenic artery
Splenic vein
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Functions of SpleenFunctions of Spleen
Shows an immune response when antigens are
found in blood (White pulp)
Reservoir of erythrocytes & platelets (Red pulp)
Phagocytosis of old, defective RBCs & platelets (Red
pulp)
Phagocytosis of bacteria & other foreign materials.
31. Lymph NodesLymph Nodes
Oval or bean shaped structures
1 to 15 mm in length
Grayish pink in color
Scattered throughout the body
Present in groups
Superficial groups
Deep groups
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32. StructureStructure ofof lymph nodelymph node
Capsule - Covering of dense connective tissue
Hilum - Depression on medial surface
- 4 to 5 efferent lymph vessels enters & exit, artery & vein
Trabeculae - Extensions of capsule, form partitions within the
lymph nodes
Divided into two parts
Outer cortex: Lymphocytes are arranged in follicles
Inner medulla: Lymphocytes are arranged in medullary
strands
Stroma: Along with capsule & trabeculae, reticular fibers &
fibroblast forms the stroma
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33. FunctionFunction
Filters foreign substances from lymph & passes back to
blood
These substance are trapped by the reticular fibers
within the lymph node
Macrophages destroy the foreign substances by
phagocytosis
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35. DisordersDisorders
Lymphadenitis:
It is the inflammation or enlargement of a lymph node.
Acute infection of lymph nodes called as acute lymphadenitis
caused by microbes in the lymph.
The nodes become inflamed, enlarged, congested with blood.
Splenomegaly:
It is an enlargement of the spleen.
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36. DisordersDisorders
Lymphomas:
There are malignant tumours of lymphoid tissue.
These are classified as either Hodgkins or non-Hodgkins
lymphomas.
It affects individuals between age group of 15 & 35 and it is
more common in males.
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37. QuestionsQuestions
SAQs:
Give the functions of lymphatic tissue. (3 M)
Give different parts of lymphatic tissue. (3 M)
Note on lymph (3 M, October 2009)
Note on lymph node. (3 M, October 2009, May 2010)
Describe composition and function of lymph. (3 M, October
2009)
Explain structure and function of lymph node. (5 M, October
2009, 2010, May 2011, 2012)
Explain structure and function of spleen. (3 M, May 2009,
May 2011, October 2011)
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