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Thursday, 8 , March, 2018

reproductive-system

Female reproductive system | about placenta, pregnancy, Ovulation

Written by jobaer , 127 Views, Date : 8 Mar, 18

Placenta- It is a flattened, discoidal mass in which blood vessels of embryo are brought into relationship with the blood of mother.

Functions of placenta-
It acts like the lungs which exchanges O2 and CO2 between maternal blood and fetus. Acts as kidney of fetus as waste products of fetus go out into maternal circulation through it.
The fetoplacental unit produces many hormones. Many drugs can also cross the placental barrier and enter fetal circulation.

Hormones of placenta-

  • Human Chorionic Gonadrotropin (HCG)
  • Human Chorionic Somatomammotropin(HCS)
  • Estrogen
  • Progesterone
  • Relaxin
  • Inhibin

Functions of placental hormones-
a. Human Chorionic Gonadrotropin (HCG)
Promotes the secretion of estrogen and progesterone
b.Human Chorionic Somatomammotropin(HCS)
Promotes the development of fetus and mothers’s breast
c. Progesterone-
Maintenance of pregnancy. Development of secretory apparatus of breast.
d.Estrogen helps to development of female sex organ and mammary gland.

Amniotic Fluid-
The fetus is bathed by a fluid known as amniotic fluid.
The fetus drinks the fluid and passes urine into it.
The volume of amniotic fluid is about 750ml.

Major functions of amniotic fluid-
Forms a sort of cushion around the fetus. Regulates temperature of fetus. Maintains the fetus in a weightless condition.

Umbilical cord-
Umbilical cord is a cord like cylindrical structure that connects the fetus with placenta. It’s length is 2 to 20 cm.

Gametogenesis-
The process of formation and development of specialized generative cells or germ cells gametogenesis. In this process diploid number of chromosomes are reduced to haploid number of chromosomes. The chromosomes are reduced by meiotic cell division. In the process sex cells are prepared for fertilization.

Gametogenesis is divided into two types-
Spermatogenesis
Oogenesis
Oogenesis-
It includes all the events by which oogonia are transformed into mature(ovum).
Step-

A. Prenatal maturation-

Primordial germ cell
Oogonia
Primary oocyte

B. Postnatal maturation-
Secondary oocyte
Mature oocyte

Ovulation-
Discharge of mature ovum from the graafian follicle by rupturing the wall of ovary is ovulation.

Fertilization-
It is the process by which male and female gametes fuse, in the ampullary region of the uterine tube.
Phases of fertilization-
Phase 1 – Penetration of the corona radiata
Phase 2 – Penetration of the zona pellucida.
Phase 3 – Fusion of oocyte and sperm cell membranes.
Completion of 2nd meiotic division of oocyte.
Formation of male pronucleus
Fusion of the male and female pronuclei

Factors necessary for a successful fertilization-
Maturation of sex cells.
Haploid number of chromosomes.
Viability of sperms and ovum.
Capacitation.
Requisite number of sperms.

Implantation-
Placement of blastocyst to the internal wall of uterus is called implantation. After 6th or 7th days after fertilization the implantation occurs.
Normal site of implantation-Posterior wall of uterus nearer to fundus.

Abnormal sites of implantation-
Pelvic cavity
Ampullary region of uterine tube
Tubal implantation
Interstitial tubal implantation.

 

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