pregnancy or gestation, as it's known, is when there's one or more embryos in the uterus. Now, pregnancy in humans is divided into trimesters, and during the first trimester there's a lot of interesting stuff happening following implantation. This hormone human chorionic gonadotropin hormone, or hcg, as it's often referred to, will be secreted and will actually prevent the degradation of the Corpus Ludie, Um, and halt the menstrual cycle. Interestingly, this hormone is actually what ah lot of pregnancy tests test for, and you can see an example of that right behind me. There. Now, the outer layer of the blast assist is known as the trophy blast, and this is what's going to grow into the endometrium to form the placenta. Now the placenta is an incredibly important organ. It's going to allow for the exchange of materials, nutrients and wastes between the mother and fetus. This is how the developing embryo is going thio, eat, breathe and get rid of its waste products. So very, very important. The developing fetus is connected to the placenta by umbilical cord, and this actually contains two arteries and a vein. Now the fetus is going thio or technically, the embryo is considered a fetus once it has its adult structures in their rudimentary form. And this is gonna happen through Organogenesis or the development of organs. And you can see here how the fetus is curled up inside the womb and how it has this bundle of two arteries in the vein that connects to the placenta. Now, in humans, we give birth to live offspring. This is known as or were known as vv Paris organisms for this reason, but some organisms lay eggs and this is known as over Paris. Whereas some reproductive strategies are Aviva Paris. This is when the egg will remain inside the parent until it's ready to hatch. No, With humans, we undergo labor these air uterine contractions that will expel the fetus from the uterus. And this is stimulated by the hormone oxytocin. And this is actually involved in a positive feedback loop because pressure from the head of the fetus on the cervix stimulates oxytocin, release oxytocin stimulates uterine contractions, which we're gonna increase the pressure on the cervix leading to more oxytocin release. So you can see how this is a positive feedback loop. Now we humans are considered the theory INS because we give birth to live developed offspring. There are other types of mammals, though no nas monitoring, which actually lay eggs and marsupials that give birth thio underdeveloped offspring that have to remain in this pouch that actually contains the mammary gland nipple. Now, mammary glands are what define mammals and or one of the things that defined mammals and these air going to be glands that secrete milk in a process known as lactation. The hormone proact and stimulates this milk production and oxytocin actually stimulates the secretion of milk in response to you suckling by the infant. That's all I have for this lesson. I'll see you guys next time.