[SOUND] So a glass of milk. White, seems to be fairly homogeneous. But I think that hides a lot of the complexity of this particular biological fluid. So in this module on milk composition we're going to try to start kind of disassembling this. And then starting to take a look at some of the components, and some of the various elements of those components. So let's get started with that. So typically when we think of milk, a glass of milk, or something like that, we're usually thinking in terms of nutrients. It's a nutrient source for us. It's a nutrient source for the neonatal, the mammal, that's suckling the lactating animal. Again, lactation evolved to provide those nutrients as well as other factors for the newborn mammal, the neonate, for the mammal. And so we'll oftentimes think about nutrients. So let's go ahead and start from that standpoint. Even though that's only one element of this whole thing of milk composition. So what do we have? We have, and a nutrient that very frankly a lot of times we kind of tend to overlook. Because we get interested in some of these other things that I'm going to put on my list here. And that nutrient is water. So, getting back to my glass of milk here, this is milk from a cow. Approximately 87% of what's in this glass is water. And water is very, very important. And again we'll get to that here in some of the other videos that are coming up. What else did we think of? Well, when you think about nutrients, one of other types of nutrient that we think about are carbohydrates. And milk has a sugar. It's called lactose. It's a sugar, a disaccharide. And again we'll dissect that later on in one of the other videos. This is far and away the major carbohydrate, that is the major sugar, in milk of most mammalian species but not all species. So there are some differences there. What else do we have? We have protein. So, proteins in milk are ingested by the neonate, broken down to amino acids. Those amino acids are absorbed in the intestines. And provide amino acids for the basically the building blocks for the production of proteins within the growing neonate. So protein's very, very important. Fourth on our list are fats. And we can also call those lipids. So milk fat is very, very important. Again, providing energy, different kinds of specialized nutrients, and so on and so forth. And again we will look at those more carefully. Well, what else do we have? So let's see, we can put down minerals. So everybody I think understands that milk is full of calcium and phosphate. For bone growth, bone development, as well as soft tissue growth and development. But there are many other minerals as well. And again, we'll examine those here later on. Vitamins, pretty much all vitamins are found in milk. Fat soluble vitamins, A, D, E, and K. There's not a lot of K in milk. A little bit, but not very much. Water soluble vitamins, the B vitamins, vitamin C, you're going to find all those in milk, but we're not going to stop there. There's another group of things that are found in milk. And that is cells, white blood cells, epithelial cells from the mammary gland. So there are going to be cells in milk. And then another one, another grouping I'm going to put down here. I'm just going to call it Other. And here really kind of we're shifting gears, well there are some other components. For example, nucleotides that you might find in DNA or RNA, the building blocks of DNA and RNA, they could be under Other. They don't really fit so much in these other areas. [COUGH] But here really what I'm kind of talking about is more the functionality. So immunoglobulins, antibodies, are proteins. And they provide some nutrition but they really provide a protective factor for the neonate. Some specialized fats don't necessarily provide energy. But they provide, again, some specialized functionality in the neonate. So, again, Other becomes more of a functional sort of way of thinking about things. Rather than the nutrient sort of way of thinking about things. This still is a very, very simplistic list. So, just to kind of give you a feel for the relative proportions of some of these things. What are we talking about in terms of mass? We have this glass of milk. What are we kind of talking about here? I want to go to the other studio and kind of break that down. And just give you a rough idea of kind of how we're thinking the different levels or amounts of these in milk. So let's go over the other studio and take a look at that.