breastfeeding breasts

- [voiceover] lactation is a process where milk is made and ejected from the mammary glandsinside the female breasts. besides being reallynourishing for a suckling baby, breast milk can also boosta newborn's immune system because it contains antibodies that the baby can't yet make on its own. but overall, breast milksupplies all of the nutrients that a growing infant needs

for the first six months of life. so before we look at themechanism of lacation, let's just get oriented to theanatomy of the female breast. so this is a woman's left side here. and here is her left armraised up in the air. and this here is herpectoralis major muscle. and the pectoralis major is the primary muscle of the chest. and the reason i mentionthe pectoralis major,

or the pec major, isjust because the breasts on the left and rightside overlie the pec major on the left and right side. so it's just to give you a clearer idea of where exactly the breasts lie in relation to the chest wall. and so what i've donehere is i've cut away the overlying skin on part of the breast so we can look at deep structures

on the right side of the breast and we can look at superficial structures on the left side of the breast. and remember, i meanright side and left side from the perspective of our lady here. so the breast in both females and males contains special glandscalled mammary glands. and mammary glands areactually modified sweat glands that are able to produce and eject milk.

so in women they developaround the time of puberty and in men they actuallydon't get developed. they stay pretty benign. and actually, before pregnancy, the mammary glands don't really make up a huge percentage of a woman's breast. but during pregnancy they sort of expand and branch out in a big wayin response to stimulation by hormones such asestrogen and prolactin.

and so they're actually a little bit tough to see on this drawing here. so i'll just blow themup for you a little bit. so we can get a better look at the anatomy of a mammary gland. so these mammary glands, surrounding them, almostlike a net encasing them, there are these cellscalled myoepithelial cells. and the myoepithelialcells are special cells

in that not only arethey lining the outside of the mammary glands, but they also cancontract and squeeze down on these glands tosqueeze milk out of them. so milk is drained toward the nipple through ducts called lactiferous ducts. and from there the milk can be ejected out through the nipple,through these tiny holes all over the nipple called nipple pores.

and so let's take a look atwhat this would look like on the bigger drawing here. so we've got our myoepithelial cells lining the outside ofthese mammary glands. and then they'll squeeze milkout of the mammary glands. send the milk along the lactiferous ducts, toward the nipple, and remember this is happeningin all of the mammary glands, and then it's ejectedout of the nipple through

tiny holes in the nipplecalled nipple pores. and actually, let me label this as a lactiferous duct here. and while we're in this nipple area, you might notice that that there are these dark, circular areas around the nipples. they're called areolae. and the areolae serve acouple of different functions. the first one is that theycontain these little bumps

called the areolar glands,or montgomery glands, that's the other name for them, and the areolar glands secrete a bit of an oily substancecalled lipoid fluid. and the lipoid fluidmoisturizes the nipple so it doesn't get dry orcracked during breastfeeding. the second function ismore for the baby's good. it turns out that the darkened areolae sort of give the infant a target,

something to aim for. they actually don't have the best vision when they're born, so this helps them to find their food source alittle bit easier and quicker. and actually i forgot to mention, there's some research that suggests that the lipoid fluid madeby the areolar glands, that it has a certain smellthat attracts the baby as well. so the areolae serve acouple different functions.

the breast also has a fairamount of fatty tissue, or adipose tissue, making up most of its content. the fat actually also supports all of the glandularstructures we've mentioned. so with all of this stuffgoing on in the breast, the glands and all of the fat, it can get a little heavy, especially when the mammary glands are

full of milk during lactation. so it needs these specialsuspensory ligaments, also called cooper's ligaments, that help it remainanchored to the chest wall. and that's what you see here in green. so now that we've looked at themajor anatomy of the breast, let's get to what happens in lactation. lactation begins when an infant begins to suckle on mom's breast.

but let's take a closer look, because there's some pretty cool neural pathways that are involved. so when a baby starts to suckle, special receptors calledmechanoreceptors in the nipple, they get activated andthey start to send messages up the spinal cord and into mom's brain, to the hypothalamus. and at this point, the hypothalamus,

when it receives these messages, it does two really cool things. it sends on signals to aset of oxytocin neurons in the posterior pituitary gland, telling them to make oxytocin. and so here you can seeoxytocin being produced. and the hypothalamusalso sends an off signal to a special type of neuronin the anterior pituitary that releases a hormone called

prolactin inhibiting hormone. and these neurons inthe anterior pituitary are called pih neurons. and they have a bit of a funny job. so, as their name might suggest, they inhibit other neuronsin the anterior pituitary from producing prolactin. so since they hypothalamushas turned them off, now the prolactin neuronsin the anterior pituitary

are free to make prolactinto their heart's content. and you can see themproducing prolactin here. but why is this important? well, it's importantbecause prolactin causes the mammary glands tostart producing milk. and oxytocin stimulatesthese myoepithelial cells that surround the mammary glands, oxytocin stimulates them to eject the milk out of the nipple so the baby can be fed.

so you kinda need both of themto have proper breastfeeding. and interestingly, i saidat the beginning that it is the suckling of the baby that sorta kicks off thiswhole neuronal cascade to cause the let down of milk, but remarkably, even the sound of a baby's cry and it doesn't have to be mom's own baby, it can be the baby of a complete stranger,

but when mom hears thesound of a baby's cry her hearing centers in her brain will actually triggerthis cascade from here. and will cause milk creation and ejection. and this mechanism sortaevolved as a safegaurd for our babies. to ensure that cryingbabies could still be fed by other lactating women, even if their own mother wasn't around,

so that they could stillgrow and stay healthy.