[SOUND] Welcome, in this module, this set of videos, we're going to talk about mamary structure. Now in this case, what I'm talking about is macrostructure,so looking at the gland from the outside and then a little bit of what the gland looks like at a macro level on the inside. But also then in some of the videos we're going to explore the microstructure, so more of the histology, getting down to that microscopic level of how the mammary gland is organized and what it looks like. So let's start off with some very basic concepts. First of all where are we going to find the mammary gland. We're going to find the mammary gland on the ventral surface of the animal, on either side of the midline. And in fact as the mammary gland develops on the fetus it usually develops along the line like this. So we're always going to find them here. We're not going to find them up here or on the back and those sorts of things. So we're always going to find the mammary gland on the ventral surface. The second really important concept is it's a skin gland. It's outside the body wall. And we need to kind of keep that in the back of our minds as we think about thinks like blood flow, and how the mammary gland works, and those kind of things. So what I'm going to do is to draw a real simplistic view of skin, and to assure we understand kind of how it fits in with this idea of the skin gland. So we just kind of put a layer here and that's the skin, it's the outside of the skin, and this is called the epidermis. Underneath that there's another layer, a bit bigger. This is called the dermis. And then underneath that, Was something called the hypodermis. This is where we find kind of the subcutaneous fat, so the fat underneath the skin. You got this middle layer here, called the dermis and the hypodermis. And what we want to think about here is, how does the mammary gland develop? So very, very fast, thinking about that. There are three layers in the embryo. This actually represent only two of those three layers. The outer layer is called the ectoderm, and that what it give rise the epidermis. The middle layer is called mesoderm, and then the endoderm is something that really isn't that involved in mammary development. And what we find in the fetus is that this ectodermal layer starts to develop and sink into the mesoderm. And just like any other skin gland, we're going to find the skin glands down in here. So you can see them on the surface. So hair, we can see on the surface. Let's use the green for hair. So a hair follicle would come down, and the actual hair follicle will be down in this dermis and hypodermis area. Sebaceous glands, a type of skin gland. Sweat glands, another type of skin gland and mammary glands. Just again, several types of skin glands. And so the gland itself is here even though the glandular part that is the part that's creating the secretion in the case of hair it's a solid secretion essentially. Arose from cells sinking down and developing those different kinds of glands. So again, it's a skin gland. It's outside the body wall. The body wall would be here. The mammary gland we'd find here, but again, the glandular part is connected to the outside. So we've seen that the mammary gland is a skin gland, and remember they got the epidermis, the dermis, and the hypodermis, where you have that sub cutaneous fat. So let's go to the first slide and kind of take a look at that real quick. So this is a gilt mammary gland, prepubertal gilt, so it hadn't developed very much. What we've done is here is we've removed the dermis and the epidermis, and so really kind of we have that hypodermis. So this is all a fat pad down here. We can see the base of the nipple, so the nipple would be up in here. And again, there are two openings to this particular teet. We're going to get back to that in a little bit and talk about the number of openings per teet depending upon the species. So let's compare that then with the back fat. And so what I've done here is the same idea, it's just a different animal this particular one would be postpubertal. We're starting to develop some mammary lobials down in here. But really to think about how organized this connective tissue is and the fat pad compared to down here in the back fat. So the mammary fat pad is going to be organized differently, even though it's subcutaneous fat, compared to say back fat or fat anywhere else on the body of the animal. Again, the mammary glands are skin glands, so we need to think about that in the context of blood flow, nerves, etc., etc., coming out of the body wall and somehow feeding that gland, wherever the gland is on the ventral surface. This is a thermographic image of a mammary gland of a cow. And so you can see the cow here, kind of lighter blue, which means it's a cooler color. So she's not radiating as much heat up here compared to the mammary gland. So it's almost 103 degrees right there, at that point, that's a lot of blood flow, right coming out here. The main artery coming out of the mammary gland's coming out right about here. So again, the mammary gland is a very, very metabolically active tissue, a tremendous amount of blood flow coming through the mammary gland, and that's why it's showing up a little bit hotter here. Another example would be a pig. And so here we've got piglets down here, and again, you can see the leg of the sow here, it's a little bit cooler. Again, up in this range here, in the high 90s Fahrenheit versus the mammary gland, which is going to be a little bit warmer. Again, because of all the blood flow coming through there, very highly metabolically active.
