chris bunting wrote:There are numerous valves and anastomosis in the equine foot.

http://www.laminitisresearch.org/downloads/chrispollitt_clinicalanatomy_andphysiology_ofthenormalequinefoot.pdf

Rick Burten wrote:Is there ever an occasion where the hydraulic pressure between p3 and the wall exceeds some maximum pressure limit (call it x) and the result is some form of damage or trauma ? Or is there for lack of a better term an "escape valve" that would limit or prevent such an event ?

chris bunting wrote:I find that Mssrs. Price and Fisher's understanding of limb and hoof anatomy is at direct variance with the findings of researchers such as Denoix, et al.

That said, in context, the referenced frog is the horny extension of the plantar/digital cushion which does indeed contain vasculature. However, read in its strictest sense, the comment by Price and Fisher regarding the presence of blood vessels in the frog , is correct, just as there are no blood vessels in the stratum externum of the hoof wall. And, as noted, there are veins that drain the venous plexuses of the hoof.

"Most of the veins that drain the major portions of venous blood from the hoof are situated at the palmar aspect of the digit. These veins drain venous blood from the coronary venous plexus, the inner venous plexus and the superficial tributaries of the heel and bulb areas. The latter two venous systems receive venous blood from the sole and frog regions. Most of the veins of the hoof are valveless, except for tributaries of the coronary and subcoronary veins, and the caudal hoof vein and its tributaries."

You may also find interesting reading here: http://www.uq.edu.au/~apcpolli/downloads/chrispollitt_clinicalanatomy_andphysiology_ofthenormalequinefoot.pdf

and here: http://www.extension.org/pages/Blood_Pumping_Mechanism_of_the_Hoof

and here: http://books.google.com/books?id=0U4jtDQaPEAC&pg=PA15&lpg=PA15&dq=venous+plexus+of+the+equine+hoof&source=bl&ots=feri1gpgMM&sig=B9bAfsazL8Gq803jLb2NvS2Qq-o&hl=en&ei=wC9LS7CaFJLaNpi25ZAJ&sa=X&oi=book_result&ct=result&resnum=9&ved=0CCcQ6AEwCA#v=onepage&q=&f=false

and here(scroll down to page18)http://www.nzerf.co.nz/Attachments/The%20Horse%27s%20Foot%20-%20The%20Inside%20Story.pdf

You might also be interested in reading this: http://www.thehorseshoof.com/Bowker_footphy.html

Rick

i was taught that because the circulatory system anastomises there was no need for valves in the lower limb , i apologise for my mistake
chris

lonestar wrote:Laminitis and founder come to mind....Since the hoof capsule is finite in its dimensions and the venous system of the hoof and limb is limited, at least to some degree, by the number of vessels and the size of those vessels, IMO based on my personal reading and conversations with others who are knowledgeable in this area, there is no mechanism to fully compensate for such an event. That said, there is some limited remedy available within the hoof capsule due to the fact that because of the complexity of the venous plexuses, some diffusion of high levels of pressure is possible.

Though not much in vogue anymore, drilling holes through the hoof capsule during episodes of severe laminitis/founder to release internal pressure has been a viable method for pressure relief/release. Analogously, when you have an injury to the nail bed of your fingers and/or toes that results in pressure caused by blood concentrating in the area of the injury, drilling or burning a hole through the nail will release that pressure and provide almost instantaneous relief.

Rick

Thanks for the answers so far ..

My question came because I did not believe that the compression of the hoof in any many is a surports to the blood flow ,and it is still not .
That the hoof (maker of)has an answer to the massive problem of compression in a very closed enviroment (hoof capsel)that is proven here by all the geat posts and info links..

I would still not see this as a pump that is part of the true cardiac system ..

I would say the answers are impressive to see how a hoof functions in a horses hoof under the amount of weight those hoove at the point of high load sure is cool..

An active animal could make one think that the movement supports the nutriton and blood flow ,but an active animal is pumping more blood because of its condition in work training etc ,more than a horse that stands about alot ..
Sorry I hope that makes sence......

I view the entire foot as a a set of interrelated elements what serve as a blood pumping mechanism in addition to other more obvious functions.

In the case of an atrophied non-functional frog, the foot survives. But, that survival happens with the cost of some degree of reduction in optimal overall function.

The lateral cartridges also participate in blood flow. Yet, in horses with severe side bone, the foot still survives.

It seems to me that there is a lot of "functional redundancy" in the hoof when it comes to blood flow. Thus it is hard to say one part is "necessary" (such as the frog or valves) when in real life we see situations where the foot survives in spite of missing some presumably vital part of the whole.

Somewhere out there is an article about a donkey whose hoof has survived in spite of a missing coffin bone. One could say that in the case of this donkey, the coffin bone was not "necessary," as the little donk' gets around on that foot good enough to have a life.

The frog and the hoof do not pump blood. IMO. Take a horse with a broken leg and suspend him from the rafters and blood still flows through the hoof. The only thing that pumps blood is the heart. The hoof may contract becasue it is not weight bearing but blood still flows.

As a horse moves and the widest part of the hoof expands and the sole and frog seek the ground. Blood flow slows or comes to a stop because the vessels are constricted. The heart is still pumping and building up pressure. The hoof leaves the ground. Blood flow continues but with a little more force than before.

IMO a horse that is standing does not provide enough pressure to stop blood flow.

Ray I just re read your last post I think we are saying the same thing.

clearthinkingone wrote:While it is true that the heart is the only pump, and it is also true that a horse standing does not provide enough pressure to completely stop blood flow through the vessels in the hoof and leg.

I'm convinced that lack of movement slows/restricts blood flow back up through the vessels in the leg. This is evident in the swelling I see in the lower leg of horses that are in stalls where movement is limited vs horses that are in paddocks or pastures where they are move free to move around.

Thus it my belief that the pressures caused within the hoof by the horse moving around, aids in moving the blood back up the leg, or for the lack of a better word, helps pump the blood up the vessels.

The information I have learned through clinics and reading seem to support my belief.

Gary_Miller wrote:
I would agree to the point that the blood flow is constricted while a horse is standing and not moving much. Constant pressure on the vessels. A horse that is moving and lifting its feet will allow the blood to flow back up the leg. Part of a reason I’m not a big fan of leaving horse in stalls all the time.

Have any of you noticed on some of your horses when you pull the hinds shoes off and let them go bare in the hind they are more likely to stock up then when they are wearing shoes. Blood flow is being constricted more without the shoes. When the bottom of the hoof is closer to or on the ground and the horse is standing around blood flow is constricted.

clearthinkingone wrote:
Can you explain Barbero's demise as not blood flow related?

clearthinkingone wrote:I don't believe it has anything to do with constant pressure. Your theory suggests that the pressure stops the blood flow, which would cause a pressure buildup on the artery side of the system, with no new blood flowing to the tissue. This would cause the tissue to start dying due to the lack of oxgen. What happens when a horse is standing it the blood flowing, back up the leg, slows down due to the force of gravity, thus causing the blood to pool in the tissue. Thus causing the swelling we see in stall ridden horses. The samething happens to humans if the stand with out movement, if you add diabetes to the equation it worsens.

clearthinkingone wrote:Movement helps because the consent constricting and un-constricting of the muscles helps move the blood out of the capillaries and back into the vessels on the way to the heart to be resupplied with oxygen. Since the horses hoof does not have very large muscles the compression that takes place with in the hoof durning movement is what moves the blood out of the hoof and back up the leg.

clearthinkingone wrote:Actually I have seen no difference between those that have shoes and those that don't.

tbloomer wrote:
I never really followed what happened to him. So I can't really talk about it. My guess would be that TB are started to young. Which ultimately lead to his demise.

Gary I think for the most part we are trying to say the same thing. I never wanted to give the impression that a standing horse does not have blood flow. It is diminished in some cases. And you are correct there are no big muscles in the hoof. I think that you are just trying to explain things in a more complicated manner.