Unit 8B.
The lymphatic system.
Organs of the lymphatic system:
Lymphatic vessels.
Lymphatic vessels are a secondary lymphoid organ. Lymphatic vessels have thin walls that
are only one cell thick. The outer edge of the lymphatic vessel is covered with endothelial
cells that overlap each other. The vessel is a tube-like shape that has a closed loop system.
This is because the end of the vessel has a closed end, which has valves which let lymph
through. The lymphatic vessels are responsible for maintaining the fluid levels and keeping
them at a balanced level. These vessels also work with other parts of the lymphatic system,
to drain a fluid called lymph from the body, and gives this excess fluid to the blood, to help
fight off infection. The lymphatic vessels also have a function to transport lipids that are
absorbed by the digestive tract. The thoracic duct, and the right lymphatic duct are
examples of lymphatic vessels. The structure and functions of both these ducts are the same, and
they are the same as the lymphatic vessels structure and function.
Lymph nodes.
Lymph nodes are a secondary lymphoid organ. Lymph nodes are bean shaped organs that
have a lump like formation. Each lymph node has connective tissue and compartments
called lymph nodules, which are dense masses of macrophages and lymphocytes.
However, these two components are separated by a lymph sinus. Lymph nodes filter out
waste products and harmful substances from fluid called lymph. The fluid that is clean and
filtered, returns to the blood, but the lymph nodes have lymphocytes inside them, so that
the bacteria that is in the lymph would get destroyed, and not go back onto the blood. The
lymph nodes are also responsible for dealing with cancer cells. If cancer cells are present,
then the lymph nodes would start to swell, as the body cannot get rid of the cancer cells on its own.
Thymus.
The thymus is a primary lymphoid organ. The thymus is a flat, asymmetrical shape, that
has a lobular structure. It is composed of epithelial, endothelial, dendritic and
mesenchymal cells. The thymus is split into two sections, called the left and right lobe.
These sections are split further into lobules, which gives the thymus a bumpy and
rough structure. The thymus produces and matures immune cells, that are used by the
immune system against infections. If the thymus doesn’t produce and mature these
cells, then the immune system and the lymphatic structures wouldn't have lymphocytes to fight off
foreign antigens. The thymus also produces hormones that help with the maturation of
specialisation of T cells.
Tonsil.
The tonsils are a secondary lymphoid organ. Tonsils are made up of clusters of lymphatic
tissues, and are located in the pharynx. The tonsils have a similar structure to lymph
nodes, and they are like your lymph nodes. Tonsils are oval shaped, and they have a small
mass, compared to the lymph nodes, as they have a dense mass. The tonsils are part of
the lymphatic system, and they help to get rid of the pathogens that enter the nose and
the mouth, and they protect the whole body from infections. The tonsils also prevent
1
, pathogens from entering the lungs, and they produce antibodies, white blood cells, and T
cells, to fight off any pathogens that enter through the nose or the mouth. Lacteals.
Lacteals are a primary lymphoid organ. Lacteals have smooth muscle fibres, and are
surrounded by blood capillaries and vessels. Lacteals have a blunt, closed end capillary that is
located on the small intestine. The lacteals have villi that lines the walls of the lacteals. The
lacteals have a function, which is to absorb nutrients and vitamins and lipids from the
intestines. The lymph in the lacteals have a milky white colour, as it has a high fat content
made up of chyle. Lacteals also collect electrolytes from the large intestine, proteins and
other fluids that are in both of the intestines.
Spleen.
The spleen is a secondary lymphoid organ. The spleen is the biggest lymphatic
organ in the body. The spleen has connective tissues, goes inwards and divides
the organ into lobules. The spleen also has two tissue types, called the red and
white pulp. The white pulp mainly consists of lymphatic tissue, and the red pulp
consists of a filter for the antigens on the blood. Also, the red pulp has blood
vessels which are interwoven with its connective tissues. The spleen fights of
any pathogens that enter the body and go into the blood. The spleen contains antibodies, and it
helps to control the level of white blood cells in the blood, and in the spleen itself. The spleen stores
blood, and filters the blood by getting rid of waste and old and damaged red blood cells, that are in
the blood. The spleen makes some of the white blood cells and the antibodies that are in your body,
and these help to fight off infections that enter your body. The spleen also maintains that level of
fluid that is in the body.
Bone marrow.
Bone marrow is a primary lymphoid organ. Bone marrow is split two sections.
One is red bone marrow, and the second is yellow bone marrow. It is comprised
of hematopoietic cells and hematopoietic tissues. The bone marrow consists of
lymphoid progenitor cells, which can either be T cells, or B cells. The
hematopoietic cells in the bone marrow can be turned into other cells that are
found in the bone marrow. The red and yellow bone marrow are intertwined
with each other. The spleen has a major function, which is to filter the blood. The spleen is also
responsible is to maintain the levels of red blood cells, white blood cells, and platelets. The spleen
filters the blood and get rid of any faulty red blood cells, white blood cells and the platelets. The
spleen fights pathogens that invade the body. The last and major function of the spleen is to act as a
reserve for blood that can be used in case of a haemorrhage.
Formation and function of lymph.
Lymph is formed due to the dependency of pressure gradients. Lymph is a clear fluid that is taken
from plasma cells, and it is similar to plasma cells. Lymph is also formed by the fluid that leaves the
capillaries to go to the tissues. Lymph is the extra fluid that flows in the lymphatic system. Lymph
takes the destroyed bacteria, waste products, and other products into the blood that can be filtered
out from the kidneys or the liver. Lymph has many functions. One is to maintain the fluid levels that
are in the body, so there is no excess fluid, or less fluid in the body. Lymph that is in the lymph nodes
deal with bacteria and cancer cells, so the body can detect them, and prevent them from causing
diseases. Lymph also absorbs fat from our diet, and transport it into the intestines.
2
The lymphatic system.
Organs of the lymphatic system:
Lymphatic vessels.
Lymphatic vessels are a secondary lymphoid organ. Lymphatic vessels have thin walls that
are only one cell thick. The outer edge of the lymphatic vessel is covered with endothelial
cells that overlap each other. The vessel is a tube-like shape that has a closed loop system.
This is because the end of the vessel has a closed end, which has valves which let lymph
through. The lymphatic vessels are responsible for maintaining the fluid levels and keeping
them at a balanced level. These vessels also work with other parts of the lymphatic system,
to drain a fluid called lymph from the body, and gives this excess fluid to the blood, to help
fight off infection. The lymphatic vessels also have a function to transport lipids that are
absorbed by the digestive tract. The thoracic duct, and the right lymphatic duct are
examples of lymphatic vessels. The structure and functions of both these ducts are the same, and
they are the same as the lymphatic vessels structure and function.
Lymph nodes.
Lymph nodes are a secondary lymphoid organ. Lymph nodes are bean shaped organs that
have a lump like formation. Each lymph node has connective tissue and compartments
called lymph nodules, which are dense masses of macrophages and lymphocytes.
However, these two components are separated by a lymph sinus. Lymph nodes filter out
waste products and harmful substances from fluid called lymph. The fluid that is clean and
filtered, returns to the blood, but the lymph nodes have lymphocytes inside them, so that
the bacteria that is in the lymph would get destroyed, and not go back onto the blood. The
lymph nodes are also responsible for dealing with cancer cells. If cancer cells are present,
then the lymph nodes would start to swell, as the body cannot get rid of the cancer cells on its own.
Thymus.
The thymus is a primary lymphoid organ. The thymus is a flat, asymmetrical shape, that
has a lobular structure. It is composed of epithelial, endothelial, dendritic and
mesenchymal cells. The thymus is split into two sections, called the left and right lobe.
These sections are split further into lobules, which gives the thymus a bumpy and
rough structure. The thymus produces and matures immune cells, that are used by the
immune system against infections. If the thymus doesn’t produce and mature these
cells, then the immune system and the lymphatic structures wouldn't have lymphocytes to fight off
foreign antigens. The thymus also produces hormones that help with the maturation of
specialisation of T cells.
Tonsil.
The tonsils are a secondary lymphoid organ. Tonsils are made up of clusters of lymphatic
tissues, and are located in the pharynx. The tonsils have a similar structure to lymph
nodes, and they are like your lymph nodes. Tonsils are oval shaped, and they have a small
mass, compared to the lymph nodes, as they have a dense mass. The tonsils are part of
the lymphatic system, and they help to get rid of the pathogens that enter the nose and
the mouth, and they protect the whole body from infections. The tonsils also prevent
1
, pathogens from entering the lungs, and they produce antibodies, white blood cells, and T
cells, to fight off any pathogens that enter through the nose or the mouth. Lacteals.
Lacteals are a primary lymphoid organ. Lacteals have smooth muscle fibres, and are
surrounded by blood capillaries and vessels. Lacteals have a blunt, closed end capillary that is
located on the small intestine. The lacteals have villi that lines the walls of the lacteals. The
lacteals have a function, which is to absorb nutrients and vitamins and lipids from the
intestines. The lymph in the lacteals have a milky white colour, as it has a high fat content
made up of chyle. Lacteals also collect electrolytes from the large intestine, proteins and
other fluids that are in both of the intestines.
Spleen.
The spleen is a secondary lymphoid organ. The spleen is the biggest lymphatic
organ in the body. The spleen has connective tissues, goes inwards and divides
the organ into lobules. The spleen also has two tissue types, called the red and
white pulp. The white pulp mainly consists of lymphatic tissue, and the red pulp
consists of a filter for the antigens on the blood. Also, the red pulp has blood
vessels which are interwoven with its connective tissues. The spleen fights of
any pathogens that enter the body and go into the blood. The spleen contains antibodies, and it
helps to control the level of white blood cells in the blood, and in the spleen itself. The spleen stores
blood, and filters the blood by getting rid of waste and old and damaged red blood cells, that are in
the blood. The spleen makes some of the white blood cells and the antibodies that are in your body,
and these help to fight off infections that enter your body. The spleen also maintains that level of
fluid that is in the body.
Bone marrow.
Bone marrow is a primary lymphoid organ. Bone marrow is split two sections.
One is red bone marrow, and the second is yellow bone marrow. It is comprised
of hematopoietic cells and hematopoietic tissues. The bone marrow consists of
lymphoid progenitor cells, which can either be T cells, or B cells. The
hematopoietic cells in the bone marrow can be turned into other cells that are
found in the bone marrow. The red and yellow bone marrow are intertwined
with each other. The spleen has a major function, which is to filter the blood. The spleen is also
responsible is to maintain the levels of red blood cells, white blood cells, and platelets. The spleen
filters the blood and get rid of any faulty red blood cells, white blood cells and the platelets. The
spleen fights pathogens that invade the body. The last and major function of the spleen is to act as a
reserve for blood that can be used in case of a haemorrhage.
Formation and function of lymph.
Lymph is formed due to the dependency of pressure gradients. Lymph is a clear fluid that is taken
from plasma cells, and it is similar to plasma cells. Lymph is also formed by the fluid that leaves the
capillaries to go to the tissues. Lymph is the extra fluid that flows in the lymphatic system. Lymph
takes the destroyed bacteria, waste products, and other products into the blood that can be filtered
out from the kidneys or the liver. Lymph has many functions. One is to maintain the fluid levels that
are in the body, so there is no excess fluid, or less fluid in the body. Lymph that is in the lymph nodes
deal with bacteria and cancer cells, so the body can detect them, and prevent them from causing
diseases. Lymph also absorbs fat from our diet, and transport it into the intestines.
2
