Physiology Of The Lymphatic System

Question 1

What is lymph fluid composed of?

Answer 1

Water

Protein

Cells (lymphocytes, bacteria, viruses and debris)

Fatty acids

Coagulation factors

Electrolytes

Question 2

What is the difference between blood and lymph?

Answer 2

1. Blood is red vs. lymph which looks like plasma
2. Blood clots more easily than lymph
3. Blood contains RBC, WBC and platelets whereas lymph contains WBC’s
4. Blood carries oxygen and more digested food vs. lymph which carries waste products and larger proteins
5. Blood is filtered by the kidneys vs lymph which is filtered by lymph nodes
6. Blood is pumped by the heart. Lymph system has no pump
7. Blood capillaries connect arteries and veins vs lymph capillaries are blind ended

Question 3

How does fluid get from the blood to the lymphatic system?

Answer 3

1. Hydrostatic pressure
2. Osmotic pressure
3. Filtration
4. Reabsorption

Question 4

In a steady state, fluid flows continuously from one compartment to another to the next. How many litres per day does the the lymph system turnover?

Answer 4

8litres

Question 5

What is the main process of fluid exchange and what is it affected by?

Answer 5

Filtration is the main process of fluid exchange. It is affected by hydrostatic pressure and osmotic absorption

Question 6

Filtration is a type of?

Answer 6

Hydrostatic pressure that forces fluid out of the capillaries.

Question 7

What is filtration (blood capillary pressure) influenced by and where is the pressure greatest?

Answer 7

It is influenced by interstitial pressure and is greatest on the arterial side and less on the venous side

Question 8

Filtration (interstitial fluid pressure) is a type of……….and is exerted by the……..on the blood capillary surface. It’s tends to be ………..and therefore draws fluid ………..in to the ………

Answer 8

Filtration (interstitial fluid pressure) is a type of HYDROSTATIC PRESSURE and is exerted by the INTERSTITIUM on the blood capillary surface. It’s tends to be NEGATIVE and therefore draws fluid OUTWARDS in to the INTERSTITIUM.

Question 9

What is osmosis?

Answer 9

Water movement due to proteins

Question 10

Reabsorption by blood capillaries occurs ……. in most tissue and …….in a steady state.

Answer 10

Reabsorption by blood capillaries occurs rarely in most tissue and not in a steady state.

Question 11

What is active hyperemia?

Answer 11

Increased capillary permeability. Eg. Heat, exercise and inflammation.

Dilation of precappilary sphincter ➡️blood flow increases ➡️blood capillary pressure increases➡️filtration increases ➡️lymphatic load increases

Question 12

What is passive hyperaemia?

Answer 12

Increased capillary hydrostatic pressure e.g DVT, congestive heart failure, CVI (causes venous oedema).

Obstruction of venous return ➡️blood backs up in the capillaries ➡️blood capillary pressure increases ➡️filtration increases➡️lymphatic load increases

Question 13

What does lymphatic load refer to?

Answer 13

To the amount of substances and fluid that have to be removed from the interstitium by the lymphatic system

Question 14

What is lymph time volume?

Answer 14

The amount of lymph transport in a unit of time. The LTV of the thoracic duct is 1-4L per day

Question 15

What is transport capacity of the lymphatic system equal to?

Answer 15

The maximum lymph time volume. Our lymph system usually works at 10% of its capacity

Question 16

Lymphatic drainage is determined by:

Answer 16

The functional integrity of the lymphatic circulation and the extrinsic muscle pump during exercise

Question 17

What are the 5 main types of oedema?

Answer 17

1. Lymphoedema
2. Dependency related oedema
3. Traumatic oedema
4. Venous oedema
5. Systemic causes (cardiac malnourishment, kidney failure)

Question 18

What is lymphatic fluid?

Answer 18

Refers to fluid once it is inside the lymphatic vessels eg. When it enters the lymph capillaries

Question 19

What are types of oedema/insufficiency?

Answer 19

High output failure

Low output failure

Combined insufficiency

Haemodynamic insufficiency

Question 20

Explain high output failure

Answer 20

Normal transport capacity with increased lymphatic load. It occurs due to overload of filtration into tissue e.g infection

Increased venous pressure ➡️ increased load ➡️ lymph transport increases ➡️lymph system attempts to return fluid back to venous system where the pressure is higher ➡️Patient eventually develops lymphoedema

Question 21

Explain low output failure

Answer 21

Decreased transport capacity and normal lymph node

Question 22

Describe the process of lymphoedema

Answer 22

Lymphoedema is caused by an accumulation of protein rich fluid in the interstitium.

The interstitial fluid stagnates with the accumulation of protein, macromolecules, hyaluronic acid, fat, water and cell debris.

Hypertension develops in the lymphatics that are still functioning causing further damage.

Secondary degenerative changes in the tissue and chronic inflammation develop due to the impaired lymph transport of immune cells

Question 23

What is the revised Starling principle?

Answer 23

It was originally thought that there was an equilibrium between filtration and reabsorption

HOWEVER

Filtration is the main process that controls fluid exchange and prevails in a steady state. Reabsorption occurs rarely in s steady state.

This means the lymphatic system has a greater role to play in fluid movement than previously believed

Question 24

Name the four mechanism that fluid, electrolytes, gases and modules transverse the capillary epithelium

Answer 24

1. Diffusion
2. Bulk flow (through pores and clefts) - small water soluble substances
3. Vesicular transport (cell wall encases proteins and pushes it to the other side)
4. Active transport