THE LYMPHATIC SYSTEM

The lymphatic system consists of capillaries, vessels, ducts and nodes that transport a fluid known as lymph. Lymph is formed from tissue fluid, which surrounds all tissue cells and performs three important functions: (i) transportation of lymphocytes, which defend the body against infection and foreign antigens (ii) transportation of lipids (iii) by its formation the drainage of excess fluid from tissues.

Distinct patches of lymphatic tissue have been given specific names; these include tonsils, adenoids, spleen and thymus.

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Lymph / Lymph/o / It is used to mean the fluid lymph or lymphatic tissue

Activity 1 write the meaning of;

1. lymphocytosis ______

2. lymphorrhagia ______

Build words which mean;

3. Removal of a lymph gland ______

4. Disease of a lymph gland ______

Lymph nodes (glands) consist of lymphatic channels held in place by fibrous connective tissue which forms a capsule. The nodes contain lymphocytes and special cells called macrophages, which can engulf foreign substances and microorganisms (by phagocytosis). Lymph nodes often trap malignant cells as well as microorganisms, some of which are also destroyed. During infection lymphocytes and macrophages multiply rapidly, causing the lymph nodes to swell. They may become inflamed and sore. Lymphocytes and macrophages can enter the lymph and blood from nodes.

The macrophages, which line the lymph organs, are part of a large system of cells known as the reticuloendothelial system or macrophage system. Cells that form this network have a common ancestry and carry out phagocytosis in the liver, bone marrow, lymph nodes, spleen, nervous system, blood and connective tissues.

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Lymphaden / lymphaden/o / A lymph node
Lymphangi / lymphangi/o / A lymph duct or vessel
Spleen / splen/o / Spleen. This organ has four main functions: destruction of old red blood cells, blood storage, blood filtration and participation in the immune response.

Activity 2 build words which mean:

1. enlarged spleen ______

2. enlargement of the liver and spleen ______

(Port/o refers to the portal vein, which drains blood from the intestines, stomach, pancreas and spleen into the liver.)

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Tonsill / tonsill/o / Tonsils form a ring of lymphoid tissue at the back of the mouth and nasopharynx. They are thought to be important in the formation of antibodies and lymphocytes.

Activity 3 build words which mean;

1.  inflammation of the tonsils ______

2.  removal of the tonsils ______

NOTE: An enlarged nasopharyngeal tonsil is known as an adenoid. Sometimes these obstruct the passage of air or interfere with hearing. Removal of the adenoids is known as an adenoidectomy.

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Thym / thym/o, thymic/o / Thymus gland which lies high in the chest above the aorta. It controls the development of the immune system in early life.

IMMUNITY

This is the condition of being immune to infectious disease and antigenic substances, which may harm the body. Immunity is brought about by the production of antibodies and cells, which destroy invading pathogens. During our lifetime we acquire immunity to common disease-producing organisms, such as viruses, which cause colds and influenza. We can also acquire immunity to more serious disease by vaccination.

DEFINITIONS:

Antibody – a substance, which circulates in the blood and can destroy or precipitate foreign substances, which have entered the body.

Antigen – is any foreign substance that enters the body and stimulates antibody production.

Activity 4 build words which mean;

1. the study of immunity ______

Write the meaning of;

2. autoimmunity ______

3.immunoglobulin ______

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Ser / ser/o / The clear portion of any liquid when separated. Blood serum is the liquid formed when blood clots. This serum can then be used as a source of antibodies.
Py / py/o / Pus.

Serum investigations can lead to a patient being seronegative or seropositive for the presence of a particular antibody.

DEFINITIONS:

Seronegative – means a lack of antibody.

Seropositive – means a high level of antibody

Pus is a yellow, protein-rich liquid, composed of tissue fluids containing bacteria and leucocytes. When a wound is forming or discharging pus it is said to be suppurating. Pus is formed in response to certain types of infection.

Activity 5 write the meaning of;

1. pyogenic ______

2. pyorrhoea ______

The immune response of the lymphatic system not only resists invasion by infective organisms but also functions to identify and destroy everything that is described as non-self, ie. foreign antigens, which have entered the body, such as in, transplanted organs or body cells, which have changed their form, such as malignant cells.

Patients infected with microorganisms, such as those present in tonsillitis, experience swollen lymph glands and blood counts will indicate an increase in the number of circulating white blood cells. Once the foreign cells have been destroyed, the lymph glands will return to their normal size.

An important feature of some lymphocytes, which make the initial response to an infection, is that they become memory cells. This means that they retain the ability to respond very rapidly to the same organism should it enter the body again. This process is the basis of immunity.

ABBREVIATIONS

AIDS – Acquired immunodeficiency syndrome

ALL – Acute lympocytic leukaemia

T & A – Tonsils and adenoids

CLL – Chronic lymphocytic leukaemia

Ig – Immunoglobulin

TLD – Thoracic lymph duct

LYMPHATIC 3