Formation of Lymph

Question 1

Describe the balance of hydrostatic and oncotic pressure at the arteriole end of the capillary bed?

Answer 1

Hydrostatic pressure is much higher than oncotic pressure

Question 2

What is the result of the hydrostatic pressure being much higher than the oncotic pressure at the arteriole end of the capillary bed?

Answer 2

Get movement of fluid from arteriole end of capillary into interstitial space

Question 3

What is the function of the movement of fluid from arteriole end of capillary to interstitial space?

Answer 3

Bathes cells, delivering glucose etc. that the cells need

Question 4

What macromolecules leak through the capillary wall into interstitial space?

Answer 4

• Smaller proteins
• Cell debris
• Bacteria

Question 5

What happens to the balance between hydrostatic pressure and oncotic pressure as you pass across the capillary bed?

Answer 5

• Hydrostatic pressure has dropped due to the loss of fluid
• Oncotic pressure remains almost the same

Question 6

What is the result of the decrease in hydrostatic pressure across the capillary bed?

Answer 6

There is a higher pull into the capillary than push out, so at the venule end you get fluid going back into the capillary

Question 7

Is the net filtration of fluid the same as the net reabsorption of fluid at the capillary bed?

Answer 7

No, about 9/10 of what is filtered is reabsorbed

Question 8

What happens to the 1/10 of fluid that is not reabsorbed at the venule end of the capillary bed?

Answer 8

It remains in interstitial space along with proteins, bits of cellular debris, and bacteria, and is drained by lymph

Question 9

Why do proteins, bits of cellular debris, and bacteria remain in the interstitial space?

Answer 9

They can’t get back through the capillary pores

Question 10

What would happen if we didn’t have a lymphatic system?

Answer 10

Would get lots of fluid pooling in the interstital space, and so become very oedematous

Question 11

When is fluid called lymph?

Answer 11

As soon as tissue fluid and the things it contains pass into the lymphatic capillaries

Question 12

What does lymph consist of?

Answer 12

• Tissue fluid
• Small proteins
• Lipids (chylomicrons from gut lymphatics)
• Damaged cells
• Bacteria
• Cancer cells

Question 13

How much lymphatic fluid is produced each day?

Answer 13

3-4L

Question 14

What does the lymphatic system do?

Answer 14

Continuously removes remaining tissue fluid (and macromolecules such as proteins) from extracellular space back to blood circulation

Question 15

What is the clinical relevance of the lymphatic system?

Answer 15

Provides route for spread of infection and malignant disease

Question 16

What are the features of lymphatic flow?

Answer 16

• One directional
• Low pressure system
• No central pump

Question 17

What allows the one directional flow in the lymphatic system?

Answer 17

• Endothelial cells in the lymphatic capillary act as one way valves to the entry of lymph
• Valves prevent backflow
• Passive and intrinsic constriction

Question 18

What is passive constriction of lymphatic vessels?

Answer 18

Something from outside helping to squeeze the tubes of lymph vessels

Question 19

What outside forces contribute to passive contriction?

Answer 19

• External constriction of the muscle that the lymphatic vessel is running through
• Pulsation of an artery running next to lymph vessel

Question 20

What vessels can perform intrinsic compression?

Answer 20

Larger lymphatic vessels

Question 21

What happens in intrisinic compression of lymph vessels?

Answer 21

As lymphatic vessels stretch, they contract due to smooth muscle in their walls, therefore as they start to fill with fluid, autonominously contract

Question 22

Describe the pathway of lymph fluid

Answer 22

1. Lymphatic capillary (small to large)
2. Afferent lymphatic vessel
3. Lymph node
4. Efferent lymphatic vessel
5. Lymphatic ducts
6. Venous circulation

Question 23

What is the result of their being multiple points of entry from a single lymphatic duct, but only one exit?

Answer 23

Slows down flow

Question 24

What is the advantage of slowed flow in lymph nodes?

Answer 24

So that whatever is in the lymph node can start to do its roles and functions

Question 25

What does the lymphatic system drain into?

Answer 25

Venous circulation

Question 26

Where does the lymphatic system drain into the venous circulation on the left?

Answer 26

The junction between left internal jugular and left subclavian

Question 27

Where does the lymphatic system drain into the venous circulation on the right?

Answer 27

Between right internal jugular vein and right subclavian vein

Question 28

Where does the right lymphatic duct drain?

Answer 28

• Right side of face
• Right arm
• Right hemithorax

Everything else drained by left

Question 29

Why is lymph not returned to the artery?

Answer 29

Because the pressure difference is too great