The structure and purpose of the lymphatic system

June 28, 2019 General Studies

The lymphatic system is responsible for interstitial fluid which comes from the tissues. It is also what absorbs and transports the fatty acids and fats as chyle, which is a milky substance containing fat droplets which is what drains the lacteals of the small intestine and into the lymphatic system, this is during digestion.

The primary function of the lymphatic system is to transport lymph which is a fluid in the body which contains white blood cells which fight infection. The lymphatic system is built up of lymphatic vessels which are also known to be similar to the circulatory systems capillaries and veins.

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Lymph vessels- Lymphatic vessels run all through your body and are found alongside the arteries or veins. Lymphatic vessels are what drain the fluid (lymph) from around the cells and then carry it through the system of lymph nodes and lymph ducts. There are two different types of lymphatic vessels, which are:

  • Afferent lymphatic vessels- are what drain the lymph from the tissues towards the lymph nodes.
  • Efferent lymphatic vessels- are what leave the lymph nodes and then take the lymph towards the lymph nodes or towards the lymphatic ducts and to the veins.
  • The basic structure of lymphatic vessels

Lymph vessels are thin walled valve structures which do carry lymph. The lymph vessels are also lined by endothelial cells and contain a thin layer of smooth muscle and adventitia which then binds the lymph vessels to the surrounding tissues. Looking at the structure, lymph vessels are also very similar to the blood vessels in terms of their structure.

How it protects the body

The lymphatic system is what helps maintain the fluid balance in the body by collecting up all of the excess fluid from the tissues and adding them into the bloodstream. The lymphatic system also helps the body to defend itself against illness and diseases by supplying it with cells which fight disease, these are called lymphocytes.

Lymph nodes- The lymph nodes are important for the immune system to work and function properly, they act as filters for particles and cancer cells. Lymph nodes don’t have a detoxification function, which is dealt with by the kidneys and the liver.

Lymph nodes have two major functions in the body, they are what filter lymph and work side by side with the immune system to build an immune response.

Lymphoid organs- Lymphatic organs are where the lymphocytes are formed and mature. They are what provide an environment for the stem cells to divide and mature into B- and T- cells. Although, there are only two primary lymphatic organs which are:

  • The thymus gland- Attains its peak development in youth and it is also where T lymphocytes are formed. Its function is to generate and select T cells which will protect the body from infection.
  • Blood marrow- The site of B cell maturation. Its responsible for the production of important immune system cells such as B cells, granulocytes, natural killer cells and immature thymocytes. It also produces platelets and red blood cells.

There are also secondary lymphatic organs which are:

  • Lymph
  • Tissue fluid
  • Blood

The lymphoid tissue filtering of each of these fluids are arranged in different ways. The secondary lymphoid tissues are also where lymphocytes are activated. The way in which the lymphoid organs protect the body is that they destroy and get rid of harmful pathogens.

How does filtering at the lymph nodes protect the body?

They help by protecting and maintaining the fluid environment of the human body by filtering, producing and delivering lymph and also by producing various blood cells. The lymph nodes also play a huge role in protecting the human body against infection, as they filter out all of the bad substances which prevents you from getting ill or prevents you from catching diseases. Without lymph nodes our immune system would be run down and there would be a massively higher chance of us catching diseases or infections. It would also be harder to fight off the diseases if you didn’t have lymph nodes and would take longer for the infection/disease to go away.

How macrophages and T lymphocytes protect the body

The macrophage is a large white blood cell which is an integral part of our immune system. Its job is to locate microscopic unknown bodies and ‘eat’ them. The macrophages use a process called phagocytosis to absorb and take in the particles and then they digest them. They are what clear the body out of worn out cells. They also provide and present antigens which is a crucial role in initiating an immune system. The way that the macrophages protect the human body is by getting rid of all of the bad particles, pathogens, bacteria, fungi and parasites. Macrophages are born from white blood cells called monocytes, which are produced by stem cells in our bone marrow.

The ‘T’ cells are called the T cells as they are developed in a small organ called the thymus gland. They are responsible for a range of different other immune responses. The immune system is a complex network of cells such as lymphocytes, and other organs that work together to defend the body against things such as disease, bacteria, virus or tumor cell. When the body discovers these substances several kinds of cells go into action to protect the body which is called an immune response. Your T cells recognise invaders but they also have other jobs to do. For example, some send chemical instructions to the rest of the immune system. Your body can then produce effective weapons to fight off the bacteria, fungi etc. Other types of T cells recognise and kill the virus infected cells straight away. Also, some of them help the B- cells to make antibodies which then bind to antigens.

In conclusion they protect the human body from disease and if or when you do catch a disease the T cells recognise this and get rid of the virus/illness that has affected you.


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