Lymphatic System – Ms Atkinson Leaving Cert Biology
Network of lymph vessels
-One way system of dead-ends
Collect the fluid that surrounds every cell in the body
-tissue fluid
Tissue fluid is fluid that has been leaked through the walls of blood capillaries as they enter the tissue
(due to high blood pressure). This fluid must be returned to the blood. Some of it returns to the
capillaries as the blood leaves the tissue. Protein in the tissue fluid does not reenter the blood. Some of
it is taken into lymphatic vessels.
Lymphatic Vessels
Lymphatic capillaries collect the tissue fluid
These drain into larger lymphatic ducts
Lymphatic vessels contain valves
Movement of lymph is as result of

surrounding muscles ‘milking’ the vessels

contractions in the muscular walls of lymph vessels
Lymph
Tissue fluid that has entered the lymphatic system is called lymph.
Its composition is similar to that of plasma, with lymphocytes, protein and lipids, though contains much
less protein than plasma. Many larger proteins do not pass through the leaking capillary walls.
Lost protein and fluid is returned to the blood by the thoracic lymph duct into the subclavian vein.
Plasma
Tissue Fluid
Ms Atkinson 2012
Lymph
Plasma
Formation of Lymph
lymphatic
some tissue fluid
enters the lymphatic
tissue fluid
cells
glucose
nitrogenous
waste
carbon
oxygen dioxide
blood flow
plasma filtered
out of capilliary
Circulation in the Lymphatic System
Ms Atkinson 2012
capilliary
tissue fluid
enters capilliary
Lymph Nodes
These are swellings found along lymph vessels
Contain large numbers of lymphocytes
Form clusters called glands in some parts
Eg: thymus, tonsils, spleen, adenoids, armpits, neck, groin
Immunity function of lymph nodes
1. Filter microbes and debris from the lymph
2. Maturation and storage of lymphocytes

antibody production

clean up cancerous cells

disable bacteria and viruses
Functions of the Lymphatic System
1. Collecting lost tissue fluid.
2. Returning lost fluid and protein to the blood

this helps maintains the blood at the right concentration.
3. Defence against pathogens

detects and filters out foreign antigens

lymphocyte and antibody production
4. Absorption and transport of fats

lacteals in the villi of the small intestine
5. Assists in hearing and balance

lymph is found in the inner ear
Oedema is the swelling of the body (usually lower legs and feet) due to too much tissue fluid. It may be
due to a failing circulation system or an unusual blood composition (too much water and salt or too little
protein) due to a kidney complaint.
Elephantiasis is due to eggs from a parasitic roundworm getting in by mosquito bites. The young worms
grow and block the lymph vessels giving an elephantiasis appearance of limbs. Treatment is by removal of
worm, drainage of fluid and surgical repair of damaged vessels if necessary
Ms Atkinson 2012
Lymphatic system
Blood system
Open circulatory system
Closed c.s.
No pump
Heart
No RBCs and proteins
Has both
Colourless fluid
Red
Nodes
None
Ms Atkinson 2012