Alexandra Nedelcu
The Lymphatic system
This report describes the normal functioning of the lymphatic system and its importance to the
human body and an introduction to a disorder affecting this system.
What is the lymphatic system?
The lymphatic system is a network of tubes that runs throughout the body and this system filters
unwanted substances out of the body and collects and returns lymph to blood circulation. This
system is made up of vessels that transport lymph fluid and other structures and organs that contain
specialised lymphatic tissue.
The system also includes lymphatic organs (lymph nodes, spleen, and thymus), lymphatic nodules
such as tonsils and Peyer’s patches, bone marrow, and diffuse lymphatic tissue which is found in the
mucous membranes, walls of the gastrointestinal tract, airways, urinary, and reproductive tracts. [1]
Our immune responses, both general and particular, rely on the lymphatic system to work properly.
The lymph nodes are lymph nodes that monitor the lymph that flow into them and create cells and
antibodies to defend our bodies from infection and sickness.[2]
Figure 1 - The lymphatic organs and the major lymph nodes.
1
,Alexandra Nedelcu
What are lymphocytes?
A lymphocyte is a type of white blood cell that is formed in the bone marrow and is then transported
through the lymph fluid. B lymphocytes and T lymphocytes are the two main types of lymphocytes. T
lymphocytes help to eliminate tumour cells and regulate immune responses, whereas B lymphocytes
produce antibodies. Lymphocytes' primary function is to function as part of the immune system,
producing antibodies that aid in responding to and eliminating foreign invaders in the body. As a
result, they protect our bodies from infectious diseases. [3]
What is lymph?
Lymph is the fluid that runs through the lymphatic system. When tissue fluids/blood plasma (mainly
water, with proteins and other dissolved components) drain into the lymphatic system, this material
forms. The fluid contains proteins, minerals, fats, nutrients, damaged cells, cancer cells and foreign
invaders (bacteria, viruses, etc).
White blood cells, often known as lymphocytes, are found inside the lymph and they fight against
bacteria and infection. The waste products and germs that have been eliminated are carried back
into the bloodstream by lymph fluid. These are then removed from the blood by the liver or kidneys.
They are excreted with other bodily waste in bowel movements or urine. [4]
Functions of the lymphatic system
Formation and transport of lymphocytes and lymph
Lymph fluid travels through the lymph vessels and drains into the bloodstream.
Lymph capillaries are tiny, thin-walled microvessels that run alongside the body's arteries and veins
in the gaps between cells. Because they contain microscopic holes, their walls are exceedingly thin
and permeable, which facilitates their function of draining and processing extracellular fluid. They
are the tiniest lymph vessels and some lymph vessels have a smooth muscle that contracts
rhythmically to transport the fluid. The fluid is also propelled by the skeletal muscles that surround
the veins, and the semilunar valves prevent backflow (fluid traveling in the wrong direction). [5]
Lymph vessels are compressed by skeletal muscle contractions, which transport lymph into the lower
neck's subclavian veins.
Lymph capillaries connect to produce larger vessels with thinner walls and more semilunar valves,
comparable to veins. The thoracic and right lymphatic ducts are formed when lymph veins connect
together. These two ducts transport lymph fluid into the neck's blood arteries.
Lymphocytes begin to form in the bone marrow by mitosis of stem cells. Some migrate to the
thymus, where they mature into T cells, while others mature into B cells in the bone marrow. They
migrate to lymph nodes in response to pathogens, where they interact with T and B cells to initiate
the adaptive immune response. Lymphocytes divide and increase in numbers at lymph nodes and in
the thymus gland.
Lymphocytes attack and break down bacteria, viruses, damaged cells or cancer cells and the lymph
fluid carries these waste products and destroyed bacteria back into the bloodstream and then the
liver or kidneys remove these from the blood.
The lymphocytes are also transported through lymph fluid and leave the node through the efferent
vessels to travel to other parts of the body to perform adaptive immune response functions. The
lymphocytes are also transported by lymph vessels. [6]
2
, Alexandra Nedelcu
Figure 2 [7]
The interstitial fluid is the fluid that fills the gaps between cells. Oxygen and nutrients diffuse from
the interstitial fluid into cells, while carbon dioxide and other wastes, as well as some proteins,
diffuse from the fluid into the cells. Its primary function is to bathe and surround body cells but the
exchange of materials also happens here.
The lymphatic system maintains fluid balance. The system removes all of the fluids and its contents
that leak out into the tissues. In humans, 20 litres of plasma is released into the interstitial space of
the tissues each day due to capillary filtration. Once this filtrate is out of the bloodstream and in the
tissue spaces, it is referred to as interstitial fluid. Of this, 17 litres are reabsorbed directly by the
blood vessels. The lymphatic system then comes into action and the excess fluid is then drained and
emptied back into the bloodstream via a series of vessels, trunks and ducts[8]
This process is very important because water, proteins, and other substances are continuously
leaking out of tiny blood capillaries into the surrounding body tissues. Since the small holes in lymph
capillary walls are larger than those in blood capillary walls, large protein molecules in the fluid can
also pass into lymph capillaries. These protein molecules are then transported out of tissues. If these
proteins were not carried away, they would exert osmotic effects and prevent tissue fluid removal,
resulting in swelling (oedema for a short period of time or lymphoedema when it is more than about
3 months).
The loss of the lymphatic system would be fatal within a day. Our tissues would swell, blood volume
would be lost, and blood pressure would rise if the lymphatic system did not drain excess fluid. [9]
3
The Lymphatic system
This report describes the normal functioning of the lymphatic system and its importance to the
human body and an introduction to a disorder affecting this system.
What is the lymphatic system?
The lymphatic system is a network of tubes that runs throughout the body and this system filters
unwanted substances out of the body and collects and returns lymph to blood circulation. This
system is made up of vessels that transport lymph fluid and other structures and organs that contain
specialised lymphatic tissue.
The system also includes lymphatic organs (lymph nodes, spleen, and thymus), lymphatic nodules
such as tonsils and Peyer’s patches, bone marrow, and diffuse lymphatic tissue which is found in the
mucous membranes, walls of the gastrointestinal tract, airways, urinary, and reproductive tracts. [1]
Our immune responses, both general and particular, rely on the lymphatic system to work properly.
The lymph nodes are lymph nodes that monitor the lymph that flow into them and create cells and
antibodies to defend our bodies from infection and sickness.[2]
Figure 1 - The lymphatic organs and the major lymph nodes.
1
,Alexandra Nedelcu
What are lymphocytes?
A lymphocyte is a type of white blood cell that is formed in the bone marrow and is then transported
through the lymph fluid. B lymphocytes and T lymphocytes are the two main types of lymphocytes. T
lymphocytes help to eliminate tumour cells and regulate immune responses, whereas B lymphocytes
produce antibodies. Lymphocytes' primary function is to function as part of the immune system,
producing antibodies that aid in responding to and eliminating foreign invaders in the body. As a
result, they protect our bodies from infectious diseases. [3]
What is lymph?
Lymph is the fluid that runs through the lymphatic system. When tissue fluids/blood plasma (mainly
water, with proteins and other dissolved components) drain into the lymphatic system, this material
forms. The fluid contains proteins, minerals, fats, nutrients, damaged cells, cancer cells and foreign
invaders (bacteria, viruses, etc).
White blood cells, often known as lymphocytes, are found inside the lymph and they fight against
bacteria and infection. The waste products and germs that have been eliminated are carried back
into the bloodstream by lymph fluid. These are then removed from the blood by the liver or kidneys.
They are excreted with other bodily waste in bowel movements or urine. [4]
Functions of the lymphatic system
Formation and transport of lymphocytes and lymph
Lymph fluid travels through the lymph vessels and drains into the bloodstream.
Lymph capillaries are tiny, thin-walled microvessels that run alongside the body's arteries and veins
in the gaps between cells. Because they contain microscopic holes, their walls are exceedingly thin
and permeable, which facilitates their function of draining and processing extracellular fluid. They
are the tiniest lymph vessels and some lymph vessels have a smooth muscle that contracts
rhythmically to transport the fluid. The fluid is also propelled by the skeletal muscles that surround
the veins, and the semilunar valves prevent backflow (fluid traveling in the wrong direction). [5]
Lymph vessels are compressed by skeletal muscle contractions, which transport lymph into the lower
neck's subclavian veins.
Lymph capillaries connect to produce larger vessels with thinner walls and more semilunar valves,
comparable to veins. The thoracic and right lymphatic ducts are formed when lymph veins connect
together. These two ducts transport lymph fluid into the neck's blood arteries.
Lymphocytes begin to form in the bone marrow by mitosis of stem cells. Some migrate to the
thymus, where they mature into T cells, while others mature into B cells in the bone marrow. They
migrate to lymph nodes in response to pathogens, where they interact with T and B cells to initiate
the adaptive immune response. Lymphocytes divide and increase in numbers at lymph nodes and in
the thymus gland.
Lymphocytes attack and break down bacteria, viruses, damaged cells or cancer cells and the lymph
fluid carries these waste products and destroyed bacteria back into the bloodstream and then the
liver or kidneys remove these from the blood.
The lymphocytes are also transported through lymph fluid and leave the node through the efferent
vessels to travel to other parts of the body to perform adaptive immune response functions. The
lymphocytes are also transported by lymph vessels. [6]
2
, Alexandra Nedelcu
Figure 2 [7]
The interstitial fluid is the fluid that fills the gaps between cells. Oxygen and nutrients diffuse from
the interstitial fluid into cells, while carbon dioxide and other wastes, as well as some proteins,
diffuse from the fluid into the cells. Its primary function is to bathe and surround body cells but the
exchange of materials also happens here.
The lymphatic system maintains fluid balance. The system removes all of the fluids and its contents
that leak out into the tissues. In humans, 20 litres of plasma is released into the interstitial space of
the tissues each day due to capillary filtration. Once this filtrate is out of the bloodstream and in the
tissue spaces, it is referred to as interstitial fluid. Of this, 17 litres are reabsorbed directly by the
blood vessels. The lymphatic system then comes into action and the excess fluid is then drained and
emptied back into the bloodstream via a series of vessels, trunks and ducts[8]
This process is very important because water, proteins, and other substances are continuously
leaking out of tiny blood capillaries into the surrounding body tissues. Since the small holes in lymph
capillary walls are larger than those in blood capillary walls, large protein molecules in the fluid can
also pass into lymph capillaries. These protein molecules are then transported out of tissues. If these
proteins were not carried away, they would exert osmotic effects and prevent tissue fluid removal,
resulting in swelling (oedema for a short period of time or lymphoedema when it is more than about
3 months).
The loss of the lymphatic system would be fatal within a day. Our tissues would swell, blood volume
would be lost, and blood pressure would rise if the lymphatic system did not drain excess fluid. [9]
3
