Question

In human female explain :
(1) Implantation and development. (2) Placenta and
(3)child birth.

(answer in detail in approximately 4 marks i.e. about 8 points) ​

Answer 1

1) Implantation is the stage of pregnancy at which the embryo adheres to the wall of the uterus. Implantation consists of three stages:

• The blastocyst contacts the implantation site of the endometrium (apposition). At this stage of prenatal development, the conceptus is called a blastocyst. It is by this adhesion that the embryo receives oxygen and nutrients from the mother to be able to grow.
• trophoblast cells of the blastocyst attach to the receptive endometrial epithelium (adhesion)
• invasive trophoblast cells cross the endometrial epithelial basement membrane and invade.

2) The outermost layer of the placenta, the chorion, comes into contact with the endometrium; it is composed of two layers of cells - inner cytotrophoblast and outer syncytiotrophoblast. The chorion and allantois fuse to form the chorioallantoic membrane. The placenta is an organ that develops in your uterus during pregnancy. This structure provides oxygen and nutrients to your growing baby and removes waste products from your baby's blood. The placenta attaches to the wall of your uterus, and your baby's umbilical cord arises from it.

3) Childbirth, also known as labour and delivery, is the ending of pregnancy where one or more babies leaves the uterus by passing through the vagina or by Caesarean section. It involves three stages of labour: the shortening and opening of the cervix, descent and birth of the baby, and the delivery of the placenta. Most babies are born head first; however about 4% are born feet or buttock first, known as breech. Typically the head enters the pelvis facing to one side, and then rotates to face down. During labour, a woman can generally eat and move around as she likes. However, pushing is not recommended during the first stage or during delivery of the head, and enemas are not recommended.