Lecture 13 – Introduction to the Lymphatic System

Question 1

Lymphatic system (4)

Answer 1

Cleansing system.
Network of drainage tubes connected to lymph glands which act as drainage channels for the body’s tissues.
Initial lymphatics absorb fluid, salts, proteins and cells from tissues to make lymph.
Lymph transported down bigger lymphatic vessels which contract while pumping , with valves to ensure lymph flows in one direction to lymph nodes/glands. Lymph nodes filter the lymph (interaction with immune system) and then pass into large lymphatic vessels which discharge lymph into great veins of the neck.

Question 2

Lymph nodes - Function (2)

Answer 2

1) To clean up the lymph before it re-enters the blood stream, by sieving out, trapping and destroying (inorganic) foreign materials.
2) Monitoring the lymph for telltale signs of (organic) predators e.g. Infection, so playing a vital role in our immune system responses.

Question 3

Lymphatic system - Functions (3)

Answer 3

Fluid homeostasis
Tissue immunity
Fat homeostasis

Question 4

Lymphatic system - Functions - Fluid homeostasis (4)

Answer 4

The first function of the Lymphatic System is fluid balance (homeostasis).
• 8 litres a day of plasma is filtered into the tissues and then reabsorbed almost entirely by the lymph drainage.
• Any build-up of fluid in the tissues for any length of time i.e. oedema, represents a failure of the lymph system to do its job properly i.e. act as an overflow pipe.
• CHRONIC OEDEMA = LYMPHATIC FAILURE
• Either lymph drainage is insufficient or lymph load (vascular fluid filtration) exceeds lymph drainage capacity.

Question 5

Lymphatic system - Functions - Fluid homeostasis: Chronic venous oedema (5)

Answer 5

Venous disease e.g. varicose veins.
Capiliary filtration faster than lymph drainage.
Occurs in legs, ankles and feet.
Rate limiting step is lymph drainage.

If lymph drainage is robust no oedema occurs despite high volumes of fluid entering.

Question 6

Lymphatic system - Functions - Tissue immunity + example (1,1)

Answer 6

Responsible for tissue immunosurvelliance.

Cellulitis - problem with lymph drainage.

Question 7

Lymphatic system - Functions - Fat homeostasis (4)

Answer 7

Responsible for gut/peripheral fat absorption.
Disturbances in lacteal function (villi in small intestine) leads to malabsorption.
Lymphoedema - elephantiasis.
Obesity impairs lymphatic function.

Question 8

Lymphoedema (3) + Treatment (1)

Answer 8

Primary - Intrinisic fault.
Teaches us about roles of genes in human biology/diseases.
Secondary - Lymphatic damage.
Management includes stimulating lymphatic drainage/reduce blood vascular filtration e.g. compression and exercise.

Question 9

Diseases of Lymphatic Dysfunction

Answer 9

• Respiratory disease: Asthma, Chronic airways disease
• CVS: Hypertension, Plasma volume homeostasis, Atherosclerosis
• CNS: Glaucoma, Dementia
• Infection and Immunity: HIV, Organ rejection, Autoimmunity, Cellulitis, Sepsis, wound healing, tissue repair
• GI: Crohn’s disease
• Cancer Metastases
• Obesity and Hypercholesterolaemia
• The greater knowledge arising from improved molecular techniques which now enables better investigation of lymphatics indicates how important lymphatic function is in human biology. We now realise that many diseases have a lymphatic dysfunction component.