Lymphatic system.ppt

Lymphatic System
V.Mythily,JCE
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Lymphatic System _V.Mythily,JCE

Lymphatic System
• The lymphatic system- Middle man between blood
and the body tissues.
• A closed system of vessels which draws the extra
tissue fluid into the blood vascular system.
• All interchanges of nourishment and waste products
between the blood and the body tissues take place
through the medium of tissue fluid.
• Colloid material from the tissue fluid cannot re-enter
the blood capillaries.
• Lymph capillaries receive collids, electrolytes, water
and other substances and return them to the blood
stream. 2

Lymphatic System
• The lymphatic system is, therefore , a subsidiary or
second circulatory system, which drains the tissue
fluids.
• Components
– Lymph and Lymph vessels
• Lymph capillaries
• Lymph vessels
• Lymphatic trunks & Terminal collecting ducts
– Lymphoid organs and tissues
• Lymph nodes
• Spleen
• Tonsils
• Thymus
• Bone marrow 3

Functions of lymphatic system
• Helps to maintain interstitial tissue pressure .
• Returns proteins ,electrolytes from tissue spaces to blood .
• Act as transport mechanism to remove RBC that have lost
into the tissues as a result of haemorrhage.
• Supplies nutrients and oxygen to those parts where blood
cannot reach.
• Role in defence mechanism as lymph nodes associated with
lymphatic system act as efficient filters and involved in
phagocytosis and transport of lymphocytes , antigen and
antigen presenting cells to the secondary lymphoid organs
that fight against infections.
• The main role of the lymphatic system is to act as a filter
against microbes, organic wastes, toxins and other debris.
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Functions of lymphatic system
• As a vital part of immune system, lymphatic
system protects a person from infection and
destroys old or abnormal cells a body doesn’t
need.
• The digested fats in small intestines are
absorbed into the lymph vessels and carried
to the liver and the circulation.
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Lymphatic System _V.Mythily,JCE 6

Lymphatic system -Lymph
• Lymphatic system is a network of organs, vessels and
tissues that work together to move a colorless, watery
extra tissue fluid (lymph) back into circulatory system .
LYMPH
• Lymph is essentially the name given to the tissue fluid
when it has entered the lymphatics.
• Protein concentration of lymph fluid is equal to tissue
fluid but lower than the plasma.
• Lymph carries particulate material, coloids and
macromolecules from tissue fluid-helps maintain the
low protein concentration of tissue fluid.
• Lymphocytes – abundant component of the lymph.
7

Lymphatic system -Lymph
• Most of the fluid (90 %) is filtered at arterial
end of the capillary is reabsorbed at its
venous end, and the remaining 10 % enters
the circulation through lymphatics and is
called lymph.
• Normal lymph flow : 2-4 L/day
• Rate of lymph flow varies in different organs
and is highest in gastrointestinal tract and the
liver.

Introduction
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Lymph Flow
• Lymph enters the lymphatic capillaries under the influence of
osmotic pressure of tissue fluid.
The lymph flow is controlled largely by the outside forces which
include:
• Contraction of smooth muscles in the walls of large lymph
vessels,
• Contraction of skeletal muscles,
• Movement of different body parts
• Arterial pulsations
• Compression of tissue by object outside the body
• Negative intra thoracic pressure and action of respiratory
muscles.
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Organisation of Lymphatic System
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Lymphatics
12

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Organization of Lymphatic System
Lymphatic System
• Lymphatic system is a closed system of lymph channels or
lymph vessels, through which lymph flows from tissue spaces
toward the blood. It is a one-way system.
• Lymphatic system arises from tissue spaces as a meshwork of
delicate vessels. These vessels are called lymph capillaries.
• Lymph capillaries start from tissue spaces as enlarged blind
ended terminals called capillary bulbs.
• These bulbs contain valves, which allow flow of lymph in only
one direction.
• There are some muscle fibers around these bulbs.
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• These muscle fibers cause contraction of bulbs so
that, lymph is pushed through the vessels.
• Lymph capillaries are lined by endothelial cells.
Capillaries unite to form large lymphatic vessels.
• Lymphatic vessels become larger and larger
because of the joining of many tributaries along
their course.
• The structure of lymph capillaries is slightly
different from that of the blood capillaries.
• Lymph capillaries are more porous and this
allows the fluid to move into the lymph capillaries
and not in the opposite direction.
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Lymph capillaries
• The lymph capillaries originate as
closed endothelial tubes that are
permeable to fluid and HMW
compounds.
• Structure is basically similar to that
of blood capillaries.
• Differences:
• The basal lamina around the
endothelial cells is absent / poorly
developed.
• Pericytes / connective tissue are not
present around the lymph caillaries.
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Lymphatic vessels
• The lymphatic capillaries join to form the lymphatic
vessels.
• The lymphatic system constitutes an accessory route
for the removal of interstitial fluid.
• The small lymph vessels are called lymph capillaries
and large lymph vessels are called lymphatic trunks
and the largest lymph vessel is thoracic duct.
• The lymphatic capillaries are present in most tissues
of the body except brain, cartillage, bone marrow
and avascular structures (e.g. cornea, crystalline lens,
nails and hairs).
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Lymphatic trunks and collecting ducts
• The lymphatic trunks are larger lymph vessels which drain
lymph from relatively large regions of the body, and they are
named for the region with which they are associated.
Examples:
Lumbar trunk: It drains lymph from the lower
limbs, lower abdominal wall, and the pelvic
organs.
Intestinal trunk : It drains lymph from the
various viscera of abdomen.
Intercoastal trunk: It drains from portions of
thorax.
Bronchomediastinal trunk: It also receives
lymph from the portion of thorax
Subclavian trunk: It drains lymph from the
upper limb.
Jugular trunk: It drains lymph from portions of
the neck and head.

Lymphatic Ducts
• Larger lymph vessels ultimately form the right
lymphatic duct and thoracic duct.
• Right lymphatic duct opens into right
subclavian vein and drains lymph from right
side of head, neck, right thorax and right arm.
• The thoracic duct opens into left subclavian
vein collects lymph drained from the lower
limbs, the abdomen, the left upper limb, and
the left side of the thorax, head, and neck .
• Thoracic duct drains the lymph from more than
two third of the tissue spaces in the body.
• Blue area = Drained by right lymphatic duct
• Pink area = Drained by thoracic duct.
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Lymphatic Vessels to Lymph Node
• Lymph node receives lymph by one or two
lymphatic vessels called afferent vessels.
• Afferent vessels divide into small channels.
Lymph passes through afferent vessels and
small channels and reaches the cortex.
• It circulates through cortex, paracortex and
medulla of the lymph node.
• From medulla, the lymph leaves the node via
one or two efferent vessels.
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Lymphatic organs and tissue
• The lymphatic organs and tissues in the body
include:
– Lymph nodes
– Spleen
– Thymus , and
– Mucosa –associated lymphoid organ (MALT)

Lymphatic tissue
• Part of tissue macrophage system (aka
Reticuloendothelial system) that play a major
role in immunological surveillance.
• Formed by aggregation of lymphocytes,
macrophages, plasma cells and dendritic cells
arranged on reticular fibres.
• They help to destroy bacteria, foreign bodies,
old dead RBCs and WBCs.

Lymph Nodes
• Lymph nodes are bean-shaped
glands that monitor and cleanse
lymph as it filters through them.
• They clear out damaged cells and
cancer cells.
• lymph nodes also store lymphocytes
and other immune system cells that
attack and destroy harmful
substances like bacteria. There are
about 600 lymph nodes scattered
throughout your body. 24

25

Lymph Nodes
– Paracortex = in between the cortex and medulla
• Contain T lymphocyes

Lymph nodes
Distribution of Lymph Nodes
• Lymph nodes are present along the course of lymphatic vessels
in elbow, axilla, knee and groin.
• Lymph nodes are also present in certain points in abdomen,
thorax and neck, where many lymph vessels join.
Functions of lymph nodes :
• Lymph nodes serve as filters which filter bacteria and toxic
substances from the lymph.
1. When lymph passes through the lymph nodes, it is filtered, i.e.
the water and electrolytes are removed. But, the proteins and
lipids are retained in the lymph.
2. Bacteria and other toxic substances are destroyed by macrophages of lymph
nodes. Because of this, lymph nodes are called defense barriers.
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Spleen
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Thymus
• Thymus. This organ is located behind the
sternum in the mediastinum.
• It’s most active before puberty.
• Function:
• It’s where T-cells (a type of white blood cell)
fully mature. T-cells help your body fight off
invaders.
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Mucosa-associated lymphoid
tissue (MALT)
• This mucus membrane exists throughout
body in many important locations.
• For example, it lines tonsils, airways, small
intestine and appendix.
• MALT looks for and destroys germs.

Lymphatic System organ
• Bone marrow. This is the soft, spongy tissue in
the center of certain bones, like hip bone,
backbones and breastbone.
• Bone marrow has the vital job of making
white blood cells, red blood cells and
platelets.
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