Muscle in Lymph Vessels?

[justadream]

TBR Bio pg 189 #77

TBR claims that “contraction of the muscular layer of the lymph vessels” DOES NOT contribute to movement of lymph inside the lymphatic system.


Howver, Campbell Biology 10th ed says “Rhythmic contractions of the vessel walls help draw fluid into the small lymphatic vessels.”



So it TBR wrong?

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[t5Nitro]

Wiki says it contributes (and therefore agrees with Campbell Biology), but I think the major driving force is skeletal muscle contraction. I think you will be alright if you think of it most similar to veins in this respect.

 

[Cawolf]

I agree with @t5Nitro - lymphatic vessels are highly analogous to veins in their structure and function.

 

[Czarcasm]

Wiki says it contributes (and therefore agrees with Campbell Biology), but I think the major driving force is skeletal muscle contraction. I think you will be alright if you think of it most similar to veins in this respect.

I agree with this. Seems odd TBR would say that. Like capillaries, lympahtic vessels are a layer of endothelial cells, just more porous and loosely held. Excess interstitial fluid is pushed into and picked up my lymph vessels and is eventually recirculated back into the blood. Skeletal muscle is what ultimately drives the movement of this fluid; the endothelial cells of lymphatic vessels also form a valve to prevent backflow of fluid. Excess body fluid is especially problematic in people who are bed prone for so long, which is due to the lack of movement in this individuals.

 

[justadream]

@Czarcasm

You said endothelial cells form a valve?

I thought endothelial cells were like a 1-cell-thick layer that lined the inside of vessels. How could something so thin form a valve?

 

[Czarcasm]

@Czarcasm

You said endothelial cells form a valve?

I thought endothelial cells were like a 1-cell-thick layer that lined the inside of vessels. How could something so thin form a valve?

Might help to visualize it with a picture:

 

[Cawolf]

I think valves are comprised of collagen.

 

[Cawolf]

While lymphatic capillaries are largely endothelium - the actual vessels have the same three layers of all vessels.

 

[Czarcasm]

From my A&P book, this might help clarify things a bit: "Lympathic vessels form in the embryo by budding from the veins, so it is not surprising that the larger ones have a similar histology. They have a tunica interna with an endothelium and valves, a tunica media with elastic fibers and smooth muscle, and a thin outer tunica externa. Their walls are thinner and their valves are closer together than those of the veins."

We're use to referring to lympathic capillaries, but forgetting that these structures get more intricate as they converge to form vessels which in turn converge to lympahtic trunks, etc. and eventually dumped into the subclavian veins. It's the vessels and beyond that have the smooth muscle and the valves indicated above.