Module 6: Section 5

Question 1

Filtration vs. Reabsorption Imbalance

Answer 1

• There is slightly more filtration than reabsorption in capillaries
• With about 7200 L of blood flowing through capillaries per day, ~20 L/day is filtered but only ~17 L/day is reabsorbed
• he remaining fluid enters the lymphatic system

Question 1

What does the lymphatic system include?

Answer 1

• The spleen
• The thymus
• The lymph nodes
• The lymph channels
• The tonsils

Question 2

Lymphatic vessels

Answer 2

• Composed of a single layer of endothelial cells
• Arranged in an overlapping pattern that creates one way valves

Question 3

Lymphatic vessels function

Answer 3

• One-way valves in lymph vessels allow fluid to enter when interstitial pressure increases, but close if vessel pressure rises, preventing backflow
• This system also lets large particles like proteins or bacteria enter the lymphatics instead of returning to capillaries

Question 4

Lymph Flow to Venous System

Answer 4

• Initial lymphatics merge into larger vessels that drain into the venous system near the right atrium
• Smooth muscle in larger lymph vessels helps move lymph toward the heart, since the system has no pump

Question 5

4 main functions of the lymphatic system

Answer 5

1. Return of excess fluid
2. Defense against disease
3. Transport of absorbed fat
4. Return of filtered protein

Question 6

Return of excess fluid - function of the lymphatic system

Answer 6

Lymphatic system helps to correct the imbalance between filtration and reabsorption to prevent the accumulation of fluid in the interstitial space

Question 7

Defense against disease - function of the lymphatic system

Answer 7

• Lymph travels through lymph nodes on its way to the heart, where phagocytes destroy bacteria picked up by lymph system
• Lymph nodes also contain lymphocytes which attack bacteria, viruses and other causes of illness

Question 8

Transport of absorbed fat - function of the lymphatic system

Answer 8

• When dietary fats are digested, their end product is too large to be absorbed into capillaries
• It can be picked up by the lymphatic system

Question 9

Return of filtered protein - function of the lymphatic system

Answer 9

• Any protein that is filtered cannot re-enter the capillaries so it is taken up by the lymphatic system
• If it were to accumulate the πIF would be significant enough to impact the balance of filtration and reabsorption
• Reabsorption could not occur

Question 10

Oedema

Answer 10

• Accumulation of interstitial fluids
• Causes swelling of the tissues

Question 11

Lymphatic Filariasis

Answer 11

• A mosquito-borne parasitic worm invades lymph vessels, blocking lymph drainage and causing severe swelling (especially in extremities)
• Affects ~120 million people in 73 countries, mainly in Africa and the Indian subcontinent