This assignment got me a distinction and meets distinction criteria, including functions of the lymphatic system, roles of the lymphatic system, disorders of the lymphatic system and their treatment, as well as patient case studies . Please use this as a guide for your assignment , not to copy and ...
The lymphatic system is a network of vessels and organs that transport a liquid called lymph
and it works in conjunction with your circulatory system as it samples tissue fluid that has
come from plasma in your blood and returns it. Lymph also contains many things your body
needs like fats and white blood cells called lymphocytes.
Functions
Tonsils = The tonsils are masses of soft lymphoid tissue and are located behind the mouth
cavity on each side of the pharynx forming a ring around the oropharynx and the
nasopharynx. It is the starting point of the respiratory tract and is the first line of defence
against unwanted pathogens or foreign cells. The tonsils trap inhaled or consumed bacteria
in pits called crypts and use stored lymphocytes called B cells and T (white blood cells) that
help the tonsils to create antibodies to neutralise the threat to help prevent illness/infection.
This helps with the defensive and protective role of the lymphatic system.
Spleen = The spleen is the largest lymphatic organ, it is located in between the stomach and
the diaphragm
and is responsible for filtering the blood. In the red pulp ( the area in the spleen responsible
for blood cell filtering), Once receiving blood from the splenic artery, old/damaged
erythrocytes (red blood cells) are removed and broken down into products like iron which are
eventually returned to bone marrow and recycled into haemoglobin. The red pulp also
provides a big storage site for thrombocytes (platelets). In the white pulp of the spleen(the
area for immune functions), T cells detect pathogens and signal to B cells. B cells then
produce the antibodies necessary to eliminate them. It is part of the lymphatic system as it
helps reinforce the protective and defensive role that the lymphatic system plays.
Thymus gland = The thymus gland is located between your lungs behind the breastbone,
above your heart. It is made up of epithelial cells as well as immature and mature
lymphocytes (white blood cells formed in red bone marrow) and fat tissue. T cells are tested
and undergo positive selection in the cortex to see if they can respond to foreign antigens
and then go through negative selection in the medulla to check that they don't bind to self-
antigens. It's important T cells mature so they don't become autoimmune. These T cells will
then go to the rest of the body and carry out important immune responses. This is an
important part of the lymphatic system as these T cells go on to circulate lymph fluid to aid in
the protection and defensive role.
Peyer’s patches = Peyer's patches are small masses of lymphatic tissue similar to the tonsils
called nodules and are located on the ileum of the small intestine. Peyer's patches are
responsible for sampling material in your small intestine; they do this as specialised cells
called M (microfold) cells feed antigens to dendritic cells/macrophages of your Peyer's
patches and these antigens are then shown to B and T cells and they determine whether it
requires an immune response. if it does, Peyer's patches signal a full-body immune
response before it can spread beyond the intestines. This also helps with the defensive role.
,Lymph Nodes = lymph nodes are located all around the body, for example, the neck and
armpit (axillary), groin (inguinal), behind the knee (popliteal), inside the elbow
(supratrochlear) and abdominal nodes. They are bean-shaped tissue surrounded in a fibrous
capsule, unlike lymphatic nodules. The capsule extends into compartments that contain B
and T cells as well as macrophages. They are attached to your lymphatic vessels where
lymphatic fluid flows through and is filtered before it goes back into the blood. It filters out
bacteria, dead cells, cancer cells and cellular waste products. These help the protective and
defensive role of the lymphatic system.
Lymph vessels = The lymphatic system is composed of many tubes (lymph vessels) which
are located all around the body and they transport a substance called lymph. The lymphatic
system is different from other systems in that it does not contain a pump like the circulatory
system. Lymphatic vessels pass through muscle tissue as it relies solely on processes like
breathing and skeletal muscle contractions for the lymph to move. It also has valves which
are similar to what circulatory veins have that prevent backflow of lymph. All lymph vessels
are essential to the overall function of the lymphatic system. The vessels carry chyle which is
essential for fat digestion, it carries white blood cells which are essential for the protective
and defensive role and it carries lymph to ducts to be emptied into blood to maintain
hydrostatic pressure.
Lymphatic ducts and the cisterna chyli= lymphatic ducts like the thoracic duct and the right
lymphatic duct help to drain lymph fluid back into the blood. The thoracic duct carries chyle,
a liquid containing both lymph and emulsified fats from digestion. The cisterna chyli is a sac
found at the lower end of the thoracic duct and it receives fatty chyle and empties into the
thoracic duct. And so aids in the absorption of fats and the maintenance of hydrostatic
pressure roles
Bone marrow = bone marrow is where white blood cells are created and where B cells
mature. white blood cells then go on to circulate the lymphatic system to aid in the protective
and defensive role.
Formation of lymph fluid = lymph fluid comes from the plasma which is the liquid substance
in the blood and due to arterial pressure is forced out of the capillaries through the
endothelium. Once it comes out of capillaries, it ends up around the surrounding tissue and
is called interstitial tissue fluid. It bathes cells to exchange materials like oxygen and
nutrients and takes waste products like carbon dioxide from respiration. Lymph vessels then
carry lymph to ducts where it is drained and returned to the bloodstream. It is considered
lymph fluid when tissue fluid is in lymph vessels/lymphatic system. seventeen out of twenty
litres of interstitial fluid goes back to the bloodstream the other three litres circulates in the
lymphatic system. Lymph is made of mostly water but contains lymphocytes, lipids and
proteins.
Three main functions of the lymphatic system
Defensive and protection role = the lymphatic system can protect the body as it contains
many lymphocytes or white blood cells that circulate in lymph fluid and in lymph nodes.
There are B and T cells as well as macrophages which all help to eliminate pathogens.
Pathogens are organisms that can cause disease this could be a virus, a bacteria, fungi,
parasites, protozoa and even proteins. Pathogens have antigens on them which are proteins
that are found on the membrane. Antigens can be recognised by the
body as non-self cells by T cells and once this happens, killer T cells will try to destroy it this
is called a cell mediated immune response but if they cant, helper T cells stimulate B cells to
, divide and B cells are able to produce antibodies that can neutralise pathogens and help to
reduce its infectivity so it can’t cause any more harm to the body. It can do this as the tip of
an antibody contains an antigen binding site called a paratope that is specific for a particular
epitope on an antigen. This can tag the pathogen or infected cell so other immune cells such
as macrophages can attack it and perform phagocytosis (engulf it) or the antibody can
neutralise it by blocking a part of the cell that is essential for invasion and survival. For
example, in bacteria antibodies can burst their cell wall and can even attach to a bacterial
flagellum to restrict its movement. Apart from making antibodies, B cells can become
memory cells that stay circulating in lymph and can remember the same pathogen so
antibody production is faster for a future infection. Your lymphatic system works differently
when you are ill or have contracted a disease than when you are healthy. When you are ill or
have a disease, you have a higher number of lymphocytes circulating in lymph to combat the
infection. may also notice that their lymph nodes for example under their jaws begin to
swell. It does this as there are more lymphocytes needed in the nodes to fight infection it can
also be due to accumulation of bacteria and dead cells. The speed in which your lymph
travels increase in order to get these increased numbers of lymphocytes to sites of infection
faster. The B cell lymphocytes as well as memory B cells at this point will actively be creating
lots of antibodies to help neutralise the threat. If the memory B cell comes across an
infection it has seen before it will start to produce antibodies faster than when it had first
encountered it this is called a humoral immune response. When ill, there is also increased
inflammation. Inflammation is your body's response to eliminate the cause of damaged cells,
in this case it's because of a pathogen. Some main symptoms of inflammation are redness,
pain, heat and swelling most of these are due to increased blood flow as blood vessels are
dilating and capillaries become “leaky” which allows more immune cells to be carried to the
sites of infections. We can see heat is a symptom of inflammation and this causes body
temperature to go up as it is harder for bacteria and viruses to survive and that it activates
your immune response. If we compare this to when you are healthy then we would see that
there is a lower number of lymphocytes as there is nothing for them to be actively
eliminating. We would also see that lymph moves at a slower rate as there is no need for the
fluid to be travelling at a faster pace. Memory B cells would be circulating in lymph in case
they are needed and there is no sign of active inflammation in the body and body
temperature is normal. The immune response starts when a pathogen that has entered the
body's surface barrier mechanism for example a cut on the skin. It will then encounter
macrophages which once recognised as a dangerous organism, will engulf some of the
pathogens and digest them through phagocytosis. But there aren’t enough macrophages to
engulf all of the bacteria as they multiply too fast so they then take on the role of dendritic
cells and present the digested protein antigens to helper T cells and they start to multiply.
Helper T cells then activate B cells and B cells create memory cells and they differentiate
into plasma cells that produce many antibodies which attach to the pathogens and neutralise
it.
Removal of tissue fluid and maintenance of hydrostatic pressure = Hydrostatic pressure is
the energy that forces blood out of capillaries and into the tissue. The lymphatic system
helps to aid in this as it carries on the cycle of tissue fluid removal and absorption by
providing a second channel. It drains tissue fluid back into the blood by lymphatic ducts in
the neck region and this means blood volume increases and this helps maintain hydrostatic
blood pressure as it is generated by fluid in blood vessels. Removal and absorption of tissue
fluid through blood vessels is dependent on changes in water potential. Water potential is
how free water molecules are to move in a certain environment. A high-water potential
means that water molecules are free to move but solutes found in blood and tissue fluid can
lower water potential as water molecules surround the solutes so they are not able to move
and this causes a low force driving it to move from one area to another. And osmosis is the
movement of water from a high-water potential to a low water potential through a permeable
membrane which in this case is the capillary. If we zoom into a capillary, we can see that
hydrostatic pressure forces plasma out of capillaries at the arterial end as arteries carry
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