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The Lymphatic system

The lymphatic system

The lymphatic system is similar to the circulatory system and runs alongside it. It is a defensive system responsible for draining the tissues of excess fluid and removing all waste materials.

The lymphatic system is composed of:

  • Lymph: a straw coloured fluid (similar to blood plasma)
  • Lymphatic vessels eg capillaries, ducts and lacteals
  • Lymph nodes or glands (up to 500)
  • Lymphatic tissue eg tonsils, adenoids, thymus, Peyers patches and the spleen

The main functions of the lymphatic system are:

  1. Removal of bacteria and abnormal material
  2. Helps prevent infection
  3. Drains away excess fluids which are then eliminated from the body.

Lymph is colourless, clear, and similar to a watery fluid resembling blood plasma which it supplies to tissues for their metabolism. It is filtered through the walls of the capillaries. In the spaces between the cells where there are no blood capillaries lymph provides nourishment.

It also carries lymphocytes – these are a type of white blood cell. There is also another type of white blood cell present which lines the inside walls of the lymph nodes. Macrophages destroy and engulf any debris, bacteria or foreign bodies carried in the lymph. They also manufacture antibodies to fight bacteria, which pass into the blood stream along with the circulating lymph. When we suffer from an infection, the lymph nodes that are nearest to the infectious site will swell (oedema) and as the white cells fight the bacteria the area tends to become tender.

The lymphatic system has no muscular pump (heart) as does the blood circulation. The lymph moves through the vessels and gets around the body through movements of large muscles contracting. Lymph travels in one direction, from body tissue back towards the heart.

Through massaging the body, the lymph flow is stimulated, the flow is assisted and the removal of waste products increased.

Lymph vessels

Lymph vessels contain valves along their vessels to prevent lymph flowing backwards. The vessels run very close to the veins around the body, and are very similar in structure to veins.

The vessels join to form larger lymph vessels, until they eventually flow into one or two large lymphatic vessels; these are the thoracic duct (or left lymphatic duct) and the right lymphatic duct. The thoracic duct receives lymph from the left side of the head, neck, chest, abdomen and lower body. The right lymphatic duct receives lymph from the right side of the head and upper body.

These large lymph vessels then empty their contents into a vein at the base of the neck, which then empties into the vena cava. The lymph is then mixed into the venous blood as it returns to the heart.

It is extremely important when massaging to ensure the movements are directing the blood and lymph flow back towards the heart.

Oedema is the swelling of the tissues. This can occur when fluids accumulate instead of returning to the blood stream.

Lymph nodes

These are usually called glands. They are tiny oval structures usually between 1mm and 25mm in length, which filter the lymph, extracting the bacteria, and defending the body by fighting against infection, destroying any harmful bacteria. Lymphocytes are found in the lymph glands, and produce the antibodies which fight against the invasion of any micro-organisms.

The lymph capillaries form a network of fine tubes. These can be found throughout the body and contain lymph. The capillaries have thin muscular walls only one cell thick. They contain one-way valves and rely on muscle contraction to push the lymph around the body. Large waste particles such as proteins, viruses and bacteria and excess tissue fluid pass through their walls, they are too large to pass through into the blood vessels.

As the lymph leaves the capillaries it passes into lymph glands stationed throughout the body, it enters the gland by one of five afferent vessels and is filtered of any unwanted material. Lymphocytes are produced in the lymph nodes which help fight infection by destroying invading bacteria and viruses by engulfing the germs. Once the lymph is filtered it passes out through the lymph nodes by the efferent vessel into the larger lymph vessels, which take the lymph to the chest region. Here it enters one of the two main lymphatic ducts which are called the thoracic and right lymphatic ducts.

These two ducts return the body’s lymph into the blood stream; creating a constant circulation between the tissue fluid, lymph in the capillaries and the blood stream.

The right lymphatic duct drains the right arm, head, neck and chest into the right brachio cephalic vein. Whilst the larger 15 inch thoracic duct drains the rest of the body, lower limbs, abdominal cavity into cistena chili from which the thoracic duct leads up to the left brachocephalic vein in the neck.

The lymph nodes of the face and head  

  • The Occipital nodes: drain the back of the head and upper neck
  • The Superficial cervical lymph nodes: drain the back of the head and neck
  • The deep cervical lymph nodes: drain the back of the head and neck
  • The Posterior auricular or mastoid lymph nodes: drain the ear and temple area
  • The Anterior auricular or parotid lymph nodes: drain the nose, eyelids and ear areas
  • The Buccal lymph nodes: drain the cheek area
  • The Sub mental lymph nodes: drain the chin and lower lip areas
  • The submandibular lymph nodes: drain the chin, lip , nose and cheek areas

The functions of the lymphatic system are:

  • To fight infection
  • To prevent excess fluid in the tissues by draining excess fluid from peripheral tissue
  • Production of antibodies
  • Removes unwanted waste materials
  • Produces lymphocytes and transports them
  • Absorbs digested fats in the villi of the intestines