UNIT 5 Lymphatic System
UNIT 5 Lymphatic System
UNIT 5 Lymphatic System
Introduction
to
Lymphatic System
Unit: 5 Introduction to Lymphatic System 7 Hrs
5.1 Structure and function of lymphatic system
5.2 Lymphatic vessels
5.3 Lymphatic organs and tissue
• Lymph nodes
• Spleen
• Thymus
• Tonsils
Payer’s patches
Lymphatic system
The lymphatic system is a part of circulatory system and a vital
part of the immune system comparing a network of lymphatic
vessels that carry a clear fluid called lymph directionally
towards the heart.
This system also known as lymphoid system or immune
system.
The lymphatic system is a network of tissues
and organs that help rid the body of toxins,
waste and other unwanted materials.
The lymphatic system consists of lymph
vessels , lymph node , and lymph. The tonsils ,
spleen and thymus are all part of the lymphatic
system.
The primary function of lymphatic system is to
transport lymph , a fluid containing infection –
fighting white blood cells, throughout the body.
The tissue fluid derived from the blood plasma and waste
products from the cells is returned to the venous capillary but
within the tissue space fine capillary vessels known as
lymphatic capillaries begin, which helps to drain the waste
products and water from the interstitial spaces.
The fluid within the lymphatic capillaries and vessels is known
as lymph.
The composition of lymph is likely of the blood plasma but
the dissolved substances are in different concentration.
Lymph also contains materials which may be damaging to the
body. Because of the greater permeability of the lymph
capillaries, substances of larger size can enter these vessels and
be removed from the interstitial space eg . If infection is
present and phagocytosis has occurred, the neutrophils and
monocytes with their ingested micro organism are drained
away in the lymphatic capillaries and vessels and finally
destroyed by lymph nodes.
The lymphatic system consists of
following structure:-
a. Lymph capillary
b. Lymph vessels
c. Lymph duct
i. The thoracic duct
ii. The right lymphatic duct
d. Lymph nodes
The accessory organs of lymphatic
system are:-
a. Spleen
b. Tonsil
c. Thymus gland
Function of lymphatic system
1. It helps to absorbed the fat from small intestine because the
only way of fat absorption is lymph.
2. The protein which contain in tissue fluid, send into the
blood .
3. It supplies nutrition and oxygen for those organs where
blood supply is impossible.
4. Its nature is lymphocytes.
5. It serves as an immune system for the body by providing
lymphocytes and other.
6. The lymph node filters the lymph and neutralizes the
bacteria by the process of phagocytosis.
7. It transports the infection and other malignant cells from the
organ to another so the cancer is spread mainly through
lymph vessels.
8. It removes the waste products from intercellular fluid.
Lymph
Lymph is a clear , watery appearing fluid found in the
lymphatic vessels.
A thin coagulable fluid (Similar to plasma but ) containing
white blood cells (lymphocytes) and chyle (A milky fluid
consisting of lymph and emulsified fat ; formed in the small
intestine during digestion of ingested fats) ; is convey to the
blood steam by lymphatic vessels.
The lymph is formed where the interstitial fluid (the fluid
which lies in the interstices of all body tissues) is collected
through lymph capillaries. It is then transported through
lymph vessels to lymph nodes before emptying ultimately
into the right and left subclavian vein , where it mixes back
with blood
Composition of Lymph
Lymph contain a variety of substance
including:-
Protein
Salt
Glucose
Fats
Water
White blood cells
Formation of lymph
Plasma gets filtered into the interstitial space across the
capillary wall.
This will be reabsorbed, leaving a small amount of fluid
behind.
In glands, various substance like protein, fats are also enters
into the interstitial space.
Various organic substance from degenerating cells are also
enters in the interstitial space.
The left out fluid and other substances enter the lymph vessels
and constitute lymph.
Small pressure favours the formation of more fluid than they
absorbed this fluid enters the lymphatic vessels.
Function
Lymphatic vessels play a role in:-
Absorption of dietary fats
Delivering fats to the bloodstream.
Collecting of excess interstitial fluids to the
bloodstream.
Delivering foreign particles to the lymph nodes.
Lymph capillaries
The lymphatic capillaries are end tubes originated
from interstitial space. It is composed of a single layer
of endothelial cells, same structure as blood capillaries
but their walls are more permeable to all interstitial
fluid constituents including proteins and cell debris.
Lymphatic capillaries are widespread, but are absent in
bones, bone marrow, teeth and CNS.
Lymphatic capillary are incredibly permeability much
more so than blood capillaries.
The tiny lymphatic capillaries join with each other to
form lymphatic vessels.
Lymph Vessels
The walls of the lymphatic vessels are about the
same structure as those of a small vein.
Lymphatic vessels begin at the blind ended
capillary weave between the tissue of the body.
It has 3 layers.
Mediastinal lymph nodes: They are present in the central part of the
chest, between the lungs. It drains from the middle section of chest
cavity, parts of the upper abdomen and lungs.
Supratrochlear lymph nodes: These nodes are present on the arms
just above the elbow joint. They drain from the fingers, hand on
the ulnar side of the arm and superficial areas of the forearm.
Inguinal lymph nodes: These nodes are located in the groin area.
They may be superficial or deep lymph nodes. They receive
lymph from the genital areas, buttock, anus, abdominal wall and
legs.
Femoral lymph nodes: Located in the upper thigh portion along
the femoral veins. They are immediately below the inguinal
lymph nodes. They drain from some of the genital parts, buttock,
thigh and the medial side of the leg.
Popliteal lymph nodes: These lymph nodes are present in the
knee area called popliteal fossa. There are two sets of
popliteal lymph nodes some are present beneath the popliteal
fascia and some are found between the popliteal artery and
the posterior surface of the knee joint. They drain from the
knee, thigh, calf and feet.
Nodes Location Region drain
Superficial
I. Cervical (Supefacial Neck Head and neck
and deep)
▶ Production of Antibodies
According to medical studies, lymph nodes are the major sites for initiation
of autoimmune responses. Lymph nodes contain lymphocytes, which is a
type of WBC. At the time of infection, in response to the antigen,
lymphocytes make antibodies which target the pathogens and destroy them.
Due to this activity, there is an increase in the production of beta cells which
results in swollen, inflamed, painful and sensitive nodes. Significant change
in their size can be observed during mild infection like cold and life-
threatening condition like cancer.
The Spleen
The spleen is a dark purple –colored organ, which lies in
the left hypochondriae region of the abdomen, between
the fundus of the stomch and the diaphragm.
Its long axis lies in the line of 9th to 10th ribs on the left
hand side .
The spleen, in healthy adult humans, is approximately 7
centimetres (2.8 in) to 14 centimetres (5.5in) in length 3-
4 cm thick.
It usually weighs between 150 grams to 200 grams.
It varies in size and weight during the lifetime of an
individual .And normally spleen is not palpable.
Organ associated with spleen
Superiorly and posteriorly- Diaphragm
Inferiorly- Left colic flexure of the large intestine
Anteriorly- Fundus of the stomach
Medially- Pancreas and the left kidney
Laterally- Separated from 9th , 10th and 11th ribs and intercostals
muscles by the diaphragm.
ArterySplenic artery
Vein Splenic vein
Nerve Splenic plexus
The spleen has diaphragmatic and visceral surface.
The diaphragmatic surface of the spleen is convex, smooth,
and is directed upward, backward. It contains hilum, where
branches of the splenic artery enter the spleen.
The visceral surface of the spleen is divided by a ridge into
two regions: an anterior or gastric and a posterior or renal.
The gastric surface is directed forward, upward, and toward
the middle, is broad and concave, and is in contact with the
posterior wall of the stomach.
The renal surface is directed medial ward and downward. It
is somewhat flattened, considerably narrower than the
gastric surface, and is in relation with the upper part of the
anterior surface of the left kidney and occasionally with the
left suprarenal gland.
Structure
The spleen has an outer coat of peritoneum , which is
firmly adherent to the internal fibro-elastic coat or splenic
capsule that dips into the organ, forming trabeculae.
Two kinds of spleenic pulp occupy the interstices of the
reticulum
Micrograph of spleenic tissue showing the red pulp (red),
white pulp (blue) and a thickened inflamed capusule.
Red pulp (Mechanical filtration of red blood cells.) It
consists of numerous various sinusoids, containing blood
,separated by a network of perivascular tissue which is
referred to as the spleenic cords. These are so called cord
contains numerous microphages and are the site of intense
phagocytes activity .
They are also contain numerous lymphocytes, which are
derived from the white pulp.
The sinusoids are microscopic blood channels. The Kupffer cells
are phagocytic, i.e., capable of ingestion of other cells and of
foreign particles. They also store hemosiderin so that it is available
for the production of hemoglobin, the oxygen-transporting
component of the red blood cell.
white pulp:- It is consists of periateriolar sheath of
lymphatic tissue with enlargements called spleenic
lymphatic follicles or Malpighian bodies .
Active immune response through humoral and cell-
mediated pathways. Composed of nodules, called
Malpighian corpuscles. These are composed of "lymphoid
follicles" (or "follicles"), rich in B-lymphocytes.
They are visible to the naked eye as whitish dots against the
dark red background of the red pulp on the freshly cut
surface of the spleen.
Functions
1. Destruction of warm out erythrocytes (Phagocytosis):-
Erythrocytes(RBC) are destroyed in the spleen and the breakdown
products are bilirubin, biliverdin and iron . Iron is passed to the
liver via the spleenic and portal veins. Other cellular materials e.g
leukocytes ,platelets and mocrobes are phagocytosed in the spleen.
2. A reservoir for blood :- The spleen can act as a reservior for red
cells , which is discharge into the bloodstream in an emergency
situation.
3. The formation of lymphocytes:- The spleen is formed partly by
lymphatic tissue which produces T lymphocytes and B
lymphocytes.
4. Haemopoiesis(formation of blood cells):- In the foetus , the spleen
is an important haemopoitic organ and platelets are formed in the
red pulp. The white pulp of the mature spleen contributes to the
circulating pool of immuno-compelent lymphocytes
Thymus glands
The thymus is a specialized primary lymphoid organ of the
immune system. Within the thymus, T cells(A small lymphocytes
develop in the thymus it is act as immune systems response to
infected or malignancy cells ) or T lymphocytes mature.
Anterior view of chest showing location and size of adult thymus
the thymus is of a pinkish-gray color, soft, and lobulated on its
surfaces.
The thymus is composed of two identical lobes and is located
anatomically in the anterior superior mediastinum, in front of the
heart and behind the sternum.
Histologically, each lobe of the thymus can be divided into a
central , medulla and a peripheral cortex which is surrounded by
an outer capsule. The cortex and medulla play different roles in
the development of T-cells.
Age Mass
birth about 15 grams
puberty about 35 grams
twenty-five years 25 grams
sixty years less than 15 grams
seventy years as low as 5 grams
At birth it is about 5 cm in length, 4 cm in breadth, and about 6 mm in
thickness. The organ enlarges during childhood, and atrophies at
puberty.
Unlike the liver, kidney and heart, for instance, the thymus is at its
largest in children.
The thymus reaches maximum weight (20 to 37 grams) by the time of
puberty. The thymus of older people is scarcely distinguishable from
surrounding fatty tissue.
As one ages the thymus slowly shrinks, eventually degenerating into
tiny islands of fatty tissue. By the age of 75 years, the thymus weighs
only 6 grams. In children the thymus is grayish-pink in colour and in
Structure
The thymus consists of two lobes joined by
areolar tissues .The lobes are enclosed by a
capsule which dips into their substances.
Dividing them into lobules that consists of an
irregular branching framework of epithelial cells
and lymphocytes.
Blood supply :- The arteries supplying the thymus are
derived from the internal thoracic artery, and from the
superior thyroid artery and inferior thyroids.
Development
Tonsils tend to reach their largest size near puberty, and they
gradually undergo atrophy thereafter. However, they are
largest relative to the diameter of the throat in young children.
Functions
These immuno competent tissues are the immune system's
first line of defense against ingested or inhaled foreign
pathogens.
Tonsils have on their surface specialized antigen capture cells
called M cells that allow for the uptake of antigens produced
by pathogens.
These M cells then alert the underlying B cells and T cells in
the tonsil that a pathogen is present and an immune response is
stimulated.
B cells are activated and proliferate in areas called germinal
centers in the tonsil. These germinal centers are places where
B memory cells are created and secretary antibody (IgA) is
produced.
Peyer's patches
Peyer's patches are organized lymphoid nodules, named
after the 17th-century Swiss anatomist Johann Conrad
Peyer.
They are aggregations of gut associated lymphoid tissue
that are usually found in the lowest portion of the small
intestine, the ileum, in humans
As such, they differentiate the ileum from the duodenum
and jejunum. The duodenum can be identified by
Brunner's glands. The jejunum has neither Brunner's
glands nor Peyer's patches
Peyer's patches are observable as elongated thickenings of
the intestinal epithelium measuring a few centimeters in
length.
About 30 are found in humans.
Microscopically, Peyer’s patches appear as oval or round
lymphoid follicles (similar to lymph nodes)
Function
Peyer's patches importance for the immune surveillance
of the intestinal lumen and in facilitating the generation
of the immune response within the mucosa.
Heavy chain γ α μ ε δ
Short notes
Lymph capillary
Lymph vessels
Payers patches
Tonsils
Thymus gland