We just got done talking a little bit about the blood flow, or

blood supply to the mammary gland and gave you the example of the dairy cow.

If you recall, a lot of blood's going through the mammary gland to produce milk.

So we talked about a 1 to 400 ratio.

A 1 to 1,000 ratio and so on.

So there's a lot more blood going through the mammary gland

than is coming out in the milk.

As blood comes into a tissue,

fluid comes out of that blood, goes to the extra cellular space.

Again, in the case of a lactating mammary gland, some of that's going out in milk,

but only a small proportion of that total volume

of fluids is coming out in the milk.

Much of it's going back through the venous system.

So it's going back into the body, but not 100% of it.

So some of it is left over in the extracellular fluid,

and as that drains from the gland, that's called lymph.

That's basically in essence what lymph is and how lymph comes to be.

So lymph is really draining from the mammary gland.

There's not lymph coming into the gland, it's only draining from the mammary gland.

So we want to kind of examine this a little bit.

Let's go to the first slide.

To give you an idea, the magnitude of what we're talking about here.

So the estimates are 1.6 units of lymph leave for every unit of milk produced.

If we talk talked about a dry cow, a dry cow is a non-lactating cow.

So she's finished one lactation, she's usually in late pregnancy in this case.

And say weeks to a couple months away from having her next calf and

starting her next lactation.

About 14 to 240 milliliters per hour or this many milliliters per day is

the amount of lymph drainage that would be coming off that mammary gland,

coming out of that mammary gland.

Tremendous variation there between animals.

For a lactating cow on the other hand,

we're talking about 1300 ml/hr or 31,000 ml/day.

So it's roughly 5x the amount of fluid coming off the mammary gland in the form

of lymph, drained from the mammary gland, form of lymph versus a dry cow.

So again a lot of this fluid that's coming out of the mammary gland through the lymph

vessels are very, very fine vessels coming up.

Usually coming up into the lymph nodes and then draining out of the mammary gland.

So let's take a look at those lymph nodes,

because really the key thing you can see in a mammary gland are lymph nodes.

And primarily, in the case of the cow,

we're talking about these great big things at the top of the mammary gland.

They're called supramammary lymph nodes.

Supra meaning on top of, or above.

And again, they're just these white things here.

There could be two on a side, there could be up to six or seven on a side.

Again, some of them on both sides of the mammary gland.

So when we think about visually seeing components of the lymph system and

the mammary gland, alot of times,

what we're talking about are really these supramammary lymph nodes.

There are other components in the mammary tissue, some other lymph nodes,

lots of lymph vessels, but they all feed back through these and

then leave the mammary gland from that point.

Go to the next slide.

And so here's a case, if you look right here, so the top of the mammary gland,

these particular lymph nodes are swollen.

She may have had, for example, mastitis down here and those lymph nodes have

swollen a little bit and just haven't really returned to normal size.

And just see right up there a little bit of swollen lymph nodes,

probably because she had some mastitis in this particular quarter.

This one is slightly swollen as well,

which is harder to see in this particular image.

Go to the next slide.

Now, one of the things that happens, one of the things when lymph drainage

is not perfect, let's say it's not completely formed really well.

And that typically happens at the very beginning of lactation in any animal.

Just some examples of cattle here, but

in any lactating animal especially the first time they lactate,

there's a lot of extracellular fluid that's left in the tissue.

It's not coming out in milk or colostrum.

It's not going back in the venous system.

A lot of that's being accumulated subcutaneously, right underneath the skin

between the skin and the mammary tissue or actually in the mammary tissue itself.

So here's some examples the first calf heifer, just heifer calf.

And you can see a lot of this fluid right in front of the mammary gland

has accumulated down here on the belly.

Subcutaneous, right underneath the skin.

And then her mammary gland itself it quite swollen.

The teats are quite swollen.

Again, a lot of extra lymph that's in this tissue that's not drained off very

well yet.

This is an older cow.

Typically, older cows, the swelling goes down faster.

This particular cow had a lot of swelling, just before she was ready to calve there.

But again, are very kind of swelled out tissue is what it amounts to.

A lot of subcutaneous fluid as well as fluid actually extra fluid in

the mammary tissue.

Typically these animals will,

this fluid will drain out over a period of days to maybe perhaps a few weeks.

Again, typically the first lactation animals have this more severely,

on average, than later lactation animals.

Let's go to the next slide.

[COUGH] Here's another example of edema in the udder of a cow.

And here, you can kind of see demarcation right there.

This cakiness here, or

this swelling here that you're looking at is primary subcutaneous fluid.

And that's not to say that the rest of mammary gland is not also

have extra fluid in it.

It's just the gravity is kind of pull this extra, excuse me,

subcutaneous fluid down to the bottom half of the gland here.

And just to kind of show you that that's what this is, if I took my finger and

just poked it gently right there, just to move that fluid around.

Let's go to the next slide.

It's called dimpling.

And this picture is the same cow, taken a few minutes later and

that dimple is still there.

If I poked up above here and

remove my finger, the tissue would have sprung right back and

you would not have noticed that there was any kind of dimpling at all to speak of.

But here again, it's just all that's done is kind of move that extra fluid,

extracellular, excuse me, subcutaneous fluid, subcutaneous fluid

away from that spot that I poked my finger and it just stays there.

So again, it's just an example again,

of this subcutaneous fluid in the mammary gland.

Again, there's also extra fluid in the mammary tissue itself.

So lymph drainage is very very important for the tissue.

And we run into problems or situations where, when lymph is not being drained

effectively, we have this situation called edema in the mammary gland.

Mammary Lymph System

Lactation Biology

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