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Physiology

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Cardiovascular System

Question
13 out of 19
 

Lymph flow from the foot is (AIPG 2008)
 
A Increased when an individual rises from the supine to standing position.
B Increased by messaging the foot
C Increased when capillary permeability is decreased
D Decreased when the valves of the leg veins are incompetent
Ans. B Increased by massaging the foot

Explanation

a.Basic anatomy: Lymph is the ultrafiltrate of blood, formed at the tissue level, from the fluid coming out of the capillaries.

b.Most of the fluid will enter the venules, but some of it remains in the intercellular space and will be taken up by the lymphatics, as lymph.

c.Lymphatic vessels are just like veins (but are thin walled)and usually will maintain unidirectional flow (due to valves)towards the heart.

d.Lymphatic flow from the periphery increases upon movements of the structures in the vicinity, e.g., arteries, veins, etc. Any external compression on the vessels will increase the lymphatic flow (as happens with the venous return).

e.Lymphatic vessels enter the neck veins; before the neck veins enter the heart (Thoracic duct enters the left venous angle at the junction of internal jugular and subclavian vein).

f.As evident, when an individual rises from the supine to standing position the lymphatic flow from the foot will decrease and not increase, due to gravity. If we massage the foot we will force the lymphatic flow (as well as venous return),by forcing the lymph to enter the lymphatic vessels.

g.Lymphatic flow decreases when capillary permeability is decreased Since, less interstitial fluid will be produced and less interstitial pressure will be generated,(this pressure is essential for lymph movement into the lymphatic vessels).Less interstitial fluid means less lymph production. When the valves of the leg become incompetent there will be venous pooling. This pooling causes retrograde pressure in the venules, resulting in reduced entry of fluid into them (from the tissues). Now, as evident, there will be more of interstitial pressure to drive the lymph into the lymphatic vessels and push it towards the heart more forcefully. So, lymphatic flow from foot is increased, in case there is incompetency of venous valves in the leg.

Cardiovascular System Flashcard List

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