The document summarizes the key components and functions of the lymphatic system. It describes the lymph, lymphatic vessels, lymph nodes, spleen, and thymus. The lymphatic system is responsible for immunity and drains interstitial fluid via a network of lymph capillaries, vessels, nodes, and ducts. Lymph nodes filter foreign substances and allow immune cell proliferation. The spleen and thymus also play important roles in immune functions.

1. 1
LYMPHATIC SYSTEM
• System responsible for specific
resistance or immunity
• System is allied with cardiovascular
system also functions with digestive
system
• Components:
Lymph, Lymphatic vessels, Lymph
nodes, Spleen, Thymus

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LYMPH
• Blood plasma filter through blood capillary walls
and form interstitial fluid.
• Interstitial fluid passes into lymph capillaries, is
called lymph.
• It is pale yellow colored liquid.
• Composition of lymph similar to that of plasma
but concentrations of constituents are different.
• Also contains substances that are large to pass
through blood capillary walls.
• Lymph passes through vessels of increasing
size and no. of lymph nodes and return to blood.

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LYMPHATIC VESSELS
• Lymphatic vessels begin as lymphatic
capillaries.
• Lymphatic capillary originate as blind-end tube in
the interstitial spaces, made of single-layer
endothelial cells.
• When pressure is greater in interstitial fluid than
in lymph capillary the endothelial cells separate
slightly and interstitial fluid enters capillary
• When pressure inside capillary is more cells
adhere closely and prevent back flow of lymph.
• Lymph moves further.

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Lymph Vessels:
• Lymph capillaries carry lymph into lymph
vessels.
• Lymph vessels has outer fibrous covering,
middle layer of smooth muscle and elastic
tissue and inner lining of endothelium.
• It has numerous cup shaped valves that
prevent back flow of lymph.
• Lymph vessels unite to form Lymph
trunks.

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Lymph Trunks
Name of trunk Organs drained
Lumbar trunks (L ,R) Lower limbs, Pelvis
region, kidneys, adrenal
glands, abdominal walls
Intestinal trunk Stomach, Intestines,
Pancreas, part of liver
Bronchomediastinal
trunks (L,R)
Thoracic wall, Lungs,
Heart
Subclavian trunks (L,R) Upper limbs
Jugular trunks (L,R) Head, Neck

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Lymphatic Ducts
• Lymph passes from lymph trunks into 2 ducts: Thoracic
(Left Lymphatic) duct & Right Lymphatic duct
• Thoracic duct:38-45cm long
• Begin as dilation called Cisterna chyli at anterior to
second lumbar vertebra
• It receives lymph from Lumbar trunks (L ,R), Intestinal
trunk, Bronchomediastinal trunks (L), Subclavian trunks
(L), Jugular trunks (L) i.e. 75% of body
• Right lymphatic duct:1cm long, receives lymph from
Bronchomediastinal trunks (L), Subclavian trunks (R),
Jugular trunks (R)
• Thoracic & Right lymphatic duct pour lymph at the
junction of left internal jugular vein & left subclavian vein
and right internal jugular vein & right subclavian vein

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Drained by
Thoracic
Duct
Drained by
Right Lymphatic
Duct

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LYMPH NODES
• About 600, bean-shaped, located along lymph
vessels, scattered throughout body
• Vary In size from 1-25mm long
• Lymph node is covered by fibrous tissue
capsule. It extends into node, these extensions
are called trabecule.
• Internal to capsule is supporting network of
reticular fibers and fibroblasts
• Capsule, trabecule, reticular fibers and
fibroblasts constitute stroma (supporting tissue)
of lymph node

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• Parenchyma (functioning part) of lymph node is
divided into superficial cortex and deep medulla
• Cortex consists of an outer cortex and inner
cortex.
• Outer cortex composed of B-cells, follicular
dendritic cells and macrophages.
• Inner cortex consists of T-cells and dendritic
cells
• Medulla of lymph node contains B-cells, plasma
cells and macrophages.
• Afferent lymphatic vessels penetrate node at
several points. Lymph flows through trabecular
sinuses into medullary sinuses.

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• Medullary sinuses drain lymph into one or two
efferent lymphatic vessels
• Efferent lymphatic vessels emerge from one
side of lymph node, at a slight depression-hilum
• Blood vessels also enter and leave node at
hilum
Functions:
1.Filteration:Foreign substances are trapped by
reticular fibers. Macrophages and lymphocytes
destroy these . Filtered lymph then leaves other
end of lymph node.
2.Proliferation:T-lymphocytes and b-lymphocytes
undergo multiplication in lymph node.

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SPLEEN
• Slightly oval in shape, 12cm in length, 7cm in width, 2.5cm
thick
• Located in left hypochondriac region between stomach and
diaphragm.
• Surrounded by fibroelastic capsule & Trabecule extend
inwards from capsule forms stroma
• Parenchyma of spleen consists of: White pulp & Red pulp
• White pulp- consists of lymphocytes & macrophages
• Red pulp -consists of blood filled venous sinuses and sple
15nic cords. It consists of RBCs, lymphocytes,
macrophages and granulocytes.
• Functions: 1.White pulp carry out immune functions.
2.Red pulp performs 3 functions:
-Removal by macrophages of ruptured, worn out or
defective blood cells
-Storage of platelets, up to 1/3 of body supply
-Production of blood cells during fetal life

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SPLEEN

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Interior 0f Spleen

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THYMUS
• A bilobed organ, located in upper part of mediastinum
between sternum & arota
• Weighs about 70g at birth, at puberty between 30-40g
and in old age 3-5g
• Both lobes are covered in envelope of areolar tissue.
Each lobe has capsule of fibroelastic tissue. Trabecule
form lobules.
• Each lobules consists of outer cortex and central
medulla.
• Cortex consists of large no.of T-cells, dendritic cells &
macrophages
• Medulla consists of T-cells, dendritic cells &
macrophages.
Function:Maturation of T-cells & acts as source of future
generations of T-cells

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FUNCTIONS OF LYMPHATIC SYSTEM
1. Draining excess interstitial fluid: Lymphatic
vessels drain excess of interstitial fluid from
tissue spaces & return to blood.
2. Transporting dietary lipids: Lymphatic
vessels transport lipid & lipid-soluble vitamins
absorbed by g.i.t to blood.
3. Carrying out immune responses: T-cells &
B-cells assisted by macrophages recognize
foreign cells, microbes, toxins and cancer cells
and destroy them by releasing cytotoxic
substances or by producing antibodies.