Published by Hodder Education © 2010 Helen McGuinness The lymphatic system.

Published by Hodder Education © 2010 Helen McGuinness

The lymphatic system


1 Objectives

By the end of this chapter you will be able to recall and understand the following knowledge:

the functions of the lymphatic system

the definition of lymph and how it is formed

the connection between blood and lymph

the circulatory pathway of lymph


2 Objectives

the names and positions and drainage of the main lymphatic nodes of the head, neck and the body

the immune response

the interrelationships between the lymphatic and other body systems

common pathologies of the lymphatic system.


3 Key wordslymphoedemalactealslymphatic capillariestissue (interstitial) fluidlymphatic vesselslymphatic nodesdeep cervical nodessuperficial cervical nodessubmandibular nodesoccipital nodesmastoid nodes

parotid nodesaxillary nodessupratrochlear nodesthoracic nodesabdominal nodespelvic nodesinguinal nodespopliteal nodesthoracic ductright lymphatic ductsubclavian veinsspleen

tonsilsthymusimmunityspecific immunitynon-specific immunityantigenantibodyhumoral immunitycell-mediated immunityimmunisationallergic reaction


4 Functions

The lymphatic system is closely associated with the cardiovascular system.

The lymphatic system assists the blood by draining the tissues of excess fluid and returning the fluid from the tissues back to heart. This helps to maintain blood volume, blood pressure and prevent oedema (waterlogging of the tissues).

The lymphatic systems also plays an important role in the body’s immune system as the lymph nodes fight infection and generate antibodies.

The lymphatic system also absorbs the products of fat digestion through the intestinal lymph vessels called the lacteals.


5 Definition of lymph

Lymph is a clear, colourless, water fluid derived from tissue fluid and contained within lymph vessels.

Lymph is similar in composition to blood except that it has a lower concentration of plasma proteins.


6 Structures of thelymphatic system

Structure Description FunctionLymphatic capillaries Minute blind-end tubes, similar in structure

to blood capillariesDrain away excess fluid and waste products from tissue spaces of body

Lymphatic vessels Similar in structure to veinsHave one-way valves and thin, collapsible walls

Carry lymph towards heart

Lymphatic nodes Oval or bean-shaped structures covered by a capsule of connective tissueMade up of lymphatic tissue

Filter lymph of micro-organisms, cell debris or harmful substances

Lymphatic ducts

(thoracic and right lymphatic)

Thoracic duct is largest lymphatic vessel and extends from second lumbar vertebra up through thorax to root of neck

Right lymphatic duct is very short in length

Lies in root of neck

Collect lymph from whole body and return it to blood via subclavian veins


7 Circulatory pathwayof lymph

The circulatory pathway of lymph begins with lymphatic capillaries which lie in the tissue spaces between the cells.

Tissue (interstitial) fluid drains into lymphatic capillaries and the excess fluid becomes lymph.

Lymphatic capillaries merge to form larger vessels called lymphatic vessels which convey lymph in and out of structures called lymph nodes.



Lymph passes through at least one node where it is filtered of cell debris, micro-organisms and harmful substances.

Once filtered, the lymph is collected into two main ducts – the thoracic duct (the largest duct), which collects lymph from the left side of the head and neck, left arm, lower limbs and abdomen, and the right lymphatic duct, which collects lymph from the right side of the head and neck and the right arm.

The collected lymph is then drained into the venous system via the right and left subclavian veins.



1. Plasma escapes blood capillary and bathes tissue cells

2. Excess fluid flows through a network of lymphatic capillaries

3. Tissue fluid enters lymph vessels where it becomes lymph

4. Larger lymphatic vessels lead to lymph nodes

5. Lymph passes through at least one lymphatic node where it is filtered

6. Filtered lymph is collected into lymphatic ducts

7. Collected lymph is drained into the venous system via the subclavian veins


10 Lymph nodes of headand neck

Name Position Areas where drained from

Cervical nodes(deep)

Deep within neck, located along the path of larger blood vessels (carotid artery and internal jugular vein)

Drain lymph from larynx, oesophagus, posterior of scalp and neck, superficial part of chest and arm

Cervical nodes(superficial)

Located at side of neck, over sternomastoid muscle

Drain lymph from lower part of ear and cheek region

Submandibular nodes

Beneath mandible Drain chin, lips, nose, cheeks and tongue

Occipital nodes At base of skull Drain back of scalp and upper part of neck


11 Lymph nodes of headand neck

Name Position Areas where drained from

Mastoid nodes

(post auricular)

Behind ear in region of mastoid process

Drain skin of ear and temporal region of scalp

Parotid nodes At angle of jaw Drain nose, eyelids and ear


12 Lymph nodes ofhead and neck


13 Lymph nodes of body

Name Position Areas from where drained

Cervical nodes(deep)

Deep within the neck, located along the path of larger blood vessels

Drain lymph from larynx, oesophagus, posterior of scalp and neck, superficial part of chest and arm

Cervical nodes

(superficial)

Located at side of neck over sternomastoid muscle

Drain lymph from lower part of ear and cheek region

Axillary nodes In underarm region Drain upper limbs, wall of thorax, breasts, upper wall of abdomen

Supratrochlear/ cubital nodes

In elbow region (medial side) Upper limbs which passes through the axillary nodes

Thoracic nodes Within thoracic cavity and along trachea and bronchi

Organs of thoracic cavity and from internal wall of thorax


14 Lymph nodes of body

Name Position Areas from where drained

Abdominal nodes Within abdominal cavity, along branches of abdominal aorta

Organs within abdominal cavity

Pelvic nodes Within pelvic cavity, along paths of iliac blood vessels

Organs within pelvic cavity

Inguinal In groin Lower limbs, external genitalia and lower abdominal wall

Popliteal Behind knee Lower limbs through deep and superficial nodes


15 Lymph nodesof body


16 Other lymphatic organs

Other lymphatic organs include the spleen, tonsils and thymus gland.


17 Types of immunity

Immunity is the ability of the body to resist infection and disease by the activation of specific defence mechanisms.

There are two types of immunity – specific and non-specific.

Non-specific immunity is programmed genetically from birth and includes mechanical barriers (skin and mucous membrane), chemicals, inflammation, phagocytosis and fever.

Specific immunity involves interaction between an antigen and an antibody.

An antigen is any substance that the body regards as foreign or potentially dangerous, and against which it produces an antibody.



An antibody is a specific protein produced to destroy or suppress antigens.

There are two types of immune response produced by different types of lymphocytes – humoral immunity involving B-lymphocytes which produce free antibodies that circulate in the bloodstream and cell-mediated immunity effected by helper T-cells, suppressor T-cells and natural killer (NK) cells that recognise and respond to certain antigens to protect the body against their effects.

Immunisation is when the body is artificially stimulated into producing antibodies.



An allergic reaction may occur when a foreign substance, or antigen, enters the body.

An allergic reaction can only occur if the person has already been exposed to the antigen at least once before and has developed some antibody to it.

Antibodies are located on the cells in the skin or mucous membranes of the respiratory and gastro-intestinal tracts. Typical antigens include pollen, dust, feathers, wool, fur, certain foods and drugs.

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Published by Hodder Education © 2010 Helen McGuinness The lymphatic system.

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