CGIER 2 - Blood flow and fluid exchange; Oedema; Lymphatic system, lymph, cancer spread

Question 1

What is the formula for calculating the net filtration pressure of capillaries?

Answer 1

NFP = (HPc - HPif) - (OPc - OPif)
Arterial end: +8.3 mmHg (out of capillaries)
Venous end: -6.7 mmHg (into capillaries)

Question 2

What is Oedema?

Answer 2

Oedema is the build-up of excess interstitial fluid in the tissues due to increased interstitial fluid pressure from its normal negative value to a positive one. Four possible disease conditions cause oedema are:

1. INCREASED CAPILLARY PRESSURE: due to venous obstruction by blood clots. In all, venous pressure increases.
2. DECREASED PLASMA PROTEIN: severe burns lead to loss of albumin (a crucial protein that causes high PCOP); nephritis also causes loss of lots of plasma proteins. In all, Plasma Colloid Osmotic Pressure decreases.
3. LYMPHATIC OBSTRUCTION: protein accumulation in the interstitial fluid caused by filariasis, which increases Interstitial Fluid Colloid Osmotic Pressure into the lymphatic system.
4. INCREASE CAPILLARY PERMEABILITY: loss of fluid and protein into the interstitial spaces as a result of burns or allergic reactions.

Question 3

What are the functions of the lymphatic system?

Answer 3

There are three main functions of the lymphatic systems:

1. To collect and return interstitial fluid to the blood vascular system.
2. To protect against disease
3. To absorb lipids from the gastrointestinal tract

Question 4

Describe the histology of the lymphatic vessels.

Answer 4

Lymphatic vessels are thin and have permeable endothelial cells with loose overlapping cells (between the endothelial cells) which are free to flap inward forming small non-return valves. Larger lymphatic vessels with non-return valves function as lymphatic pumps helped by contraction of the body muscles.

Question 5

What enters the lymphatic vessels?

Answer 5

Interstitial fluid, proteins, particles, and bacteria can enter the lymphatic system, but cannot leave.

Question 6

Describe the difference in lymph flow between rest and exercise.

Answer 6

During EXERCISE lymph flow may increase to five to fifteen times its usual speed.
During REST lymph flow becomes sluggish at slows to a rate of 120 ml/hr.

Question 7

What are lymph nodes?

Answer 7

Lymph nodes are found at the junction between lymphatic vessels and contain two types of white blood cells - lymphocytes and macrophages. They serve to filter bacteria and foreign particles out of the system.

Question 8

What is the lymph node in the gut called?

Answer 8

The lymph node in the gut is called a Peyer’s Patch.

Question 9

Describe the flow of lymph from being absorbed in the lacteals.

Answer 9

Terminal lymphatic capillaries (lacteals) –> lymph nodes –> lymphatics –> cisterna chyli (large sac below the liver) –> thoracic duct (runs behind the oesphogaus) –> enters the venous system at the junction between the left subclavian & right jugular veins

Question 10

How is the lymphatic system not equal on both sides?

Answer 10

The lower body and left upper body (left head and arm) drain through the thoracic duct, while the right upper body (right thorax, head, and arm) drain through the right lymphatic duct and enters the venous system through the junction of the right subclavian vein and right jugular vein.