Lymphatic System and other Circulatory Fluids

Question 1

Regarding lymph (true or false):

The lymph draining the liver has three times that draining the heart and twice as much protein in the lymph as skeletal muscle

Answer 1

True. There is negligible protein in lymph from the choroid plexus or ciliary body but lymph in the porta hepatis has 6 g/dl.

Question 2

Regarding lymph (true or false):

Fats with more than six carbon atoms cannot pass across the capillary basement membrane

Answer 2

False. Fats up to a chain length of 12 carbon atoms are sufficiently water soluble to be absorbed into the capillary blood.

Question 3

Regarding lymph (true or false):

Chylomicrons are made in the lumen of the small intestine facilitating the absorption of cholesterol

Answer 3

False. The chylomicrons are made in the golgi apparatus of the enterocyte cells after the triglycerides have been re-esterified.

Question 4

Regarding lymph (true or false):

Apoprotein APO B-100 is typical of the endogenous system

Answer 4

True. APO B-100 is a high molecular weight form found on very low density lipoprotein and intermediate density lipoprotein in the blood.

Question 5

Regarding lymph (true or false):

T lymphocytes and Granulocytes are found in lymph draining the spleen

Answer 5

False. Lymphocytes are found in lymph but granulocyte cells are not. After maturing in the bone marrow they circulate in the blood stream. In areas of inflammation they leave the blood stream, however in the tissues they are absorbed by macrophages and do not re-circulate.

Question 6

Regarding flow in the lymphatics from the foot (true or false):

It increases when an individual rises from the supine to standing position

Answer 6

False. This will reduce flow due to the gravity effect.

Question 7

Regarding flow in the lymphatics from the foot (true or false):

Increases when capillary permeability is decreased

Answer 7

False. When capillary permeability increases so more fluid is filtered, the pressure in the interstitial space will rise, causing increased flow in the lymphatics.

Question 8

Regarding flow in the lymphatics from the foot (true or false):

Is increased by massaging the foot

Answer 8

True. This will aid flow away from the foot, and is used as a treatment in lymph oedema.

Question 9

Regarding flow in the lymphatics from the foot (true or false):

Decreases when the valves of the deep veins are incompetent

Answer 9

False. This will reduce venous return and may cause swelling and ulceration of the lower leg but will not effect the flow of lymph. The flow relies on intrinsic contraction of the vessels augmented by skeletal muscles. The large veins of the thorax may help flow due to their pulsation, which is transmitted from the arteries.

Question 10

Regarding flow in the lymphatics from the foot (true or false):

Is decreased by exercise

Answer 10

False. The increased muscle tone in exercise helps propel the lymph along the vessels.

Question 11

The following are typical constituents of lymph (true or false):

Platelets

Answer 11

False. Lymph can contain al polymorphonuclear leukocytes which leave the circulation by diapaedesis but not red blood cells or platelets except if there has been trauma to the area.

Question 12

The following are typical constituents of lymph (true or false):

A glucose content of 12 mmol/L

Answer 12

False. Glucose content is similar to the plasma so should be 3-5 mmol/l.

Question 13

The following are typical constituents of lymph (true or false):

Chylomicrons

Answer 13

True. Triglycerides and some cholesterol are incorporated into chylomicrons to allow absorption from the gut as they are too insoluble to be carried in the blood.

Question 14

The following are typical constituents of lymph (true or false):

Phagocytic cells

Answer 14

True. Roaming macrophages are found in the lymph where they act as a filter for microorganisms and foreign particles.

Question 15

The following are typical constituents of lymph (true or false):

A protein concentration of 100 mg/dl

Answer 15

False. Appreciable amounts of protein are carried in the lymph draining the liver and intestine and in addition proteins leak out of the capillaries at junctions between the cells. Between 25-50 % of the total circulating protein is returned to the circulation via the lymphatics daily.

Question 16

Which of the following best explains the forward flow of lymph from the periphery back into the central veins?

A. Filtration exceeds re-absorption in the systemic capillaries, producing a positive interstitial compartment pressure
B. Inspiration produces a large negative intra-thoracic pressure, which sucks the lymph into the thorax from the periphery
C. High velocity flow in the brachiocephalic vein by a venturi effect sucks lymph into the circulation
D. In the standing position, skeletal muscles contract to propel the lymph towards the thorax
E. The main lymphatic vessels have smooth muscle in their walls and undergo ‘myogenic contractions’ to propel the lymph towards the thorax

Answer 16

A. The major force causing flow in the lymphatics is the tissue interstitial pressure, this is related to the excess ultra-filtration over re-absorption in that capillary bed and the elasticity of the tissues surrounding the interstitial space. The resting pressure may be sub-atmospheric but in the brain it is 6 mm Hg.

B. Incorrect. This and the venturi effect of blood flow in the brachiocephalic vein are also important but only effect the lymph flow in the large vessels.

C. Incorrect.

D. Incorrect. During exercise, the arterioles dilate causing increased capillary hydrostatic pressure, which results in excess ultra-filtration, and consequently the volume absorbed into the lymphatics is increased. Allied to this skeletal muscle contractions aid flow of the lymph.

E. Incorrect. The intrinsic contractions only permit very sluggish flow alone.

Question 17

Regarding lymphatic drainage in the body (true or false):

Drainage from the anal canal is to the superficial inguinal nodes

Answer 17

True. Lymph drains to the upper superficial inguinal group from the lower third of the anal canal. The upper two thirds of the anal canal and the rectum drain to the internal and common iliac nodes.

Question 18

Regarding lymphatic drainage in the body (true or false):

The liver may drain to the mediastinal nodes or the porta hepatis

Answer 18

True. The liver has superficial and deep plexi and both can either drain along the portal vein to the porta hepatis, or with the hepatic vein to the inferior vena cava, and through the diaphragm to the mediastinal nodes.

Question 19

Regarding lymphatic drainage in the body (true or false):

The kidneys are drained by the preaortic nodes

Answer 19

False. The kidneys drain into the paraaortic nodes which unite to form the right and left lumbar lymph trunks.

Question 20

Regarding lymphatic drainage in the body (true or false):

The cisterna chyli is 15 cm long lying in front of the 4th and 5th lumbar vertebrae

Answer 20

False. The cisterna chyli is 5-7 cm long and in front of L1 and L2 vertebra. It lies between the aorta and the right crus of the diaphragm, and empties directly into the thoracic duct.

Question 21

Regarding lymphatic drainage in the body (true or false):

The cerebellum drains via the occipital nodes to the deep cervical lymph chain

Answer 21

False. The brain has no lymph drainage. The posterior scalp and neck do drain via this route.