Kalpesh J Gadhvi is teaching live on Unacademy Plus
Human reproduction Presented by Kalpesh gadhvi
About me Myself Kalpesh gadhvi I am pursuing MBBS at PDU MEDICAL COLLEGE RAJKOT My hobbies are playing cricket and listen music You can follow me on unacademy by pressing follow button on my profile If you like my courses than you can rate review recommend and share it. . . . . .
Fertilization and implantation
During coitus, the semen is released into the vagina, passes through the cervix of the uterus and reaches the ampullary-isthmic junction of the fallopian tube. . The ovum is also released into the junction for fertilisation to occur. . The process of fusion of the sperm and the ovum is known as fertilisation. . During fertilisation, the sperm induces changes in the zona pellucidaand blocks the entry of other sperms. This ensures that only one sperm fertilises an ovum. . The enzymatic secretions of acrosome help sperm in penetration to ovum cytoplasm.
. This causes the completion of meiotic division of the secondary oocyte, resulting in the formation of a haploid ovum (ootid) and a secondary polar body. . Then, the haploid sperm nucleus fuses with the haploid nucleus of the ovum to form a diploid zygote. . Mitosis starts as the zygote moves through the isthmus of the oviduct (cleavage) and forms 2, 4, 8, 16 daughter cells called blastomeres. The 8-16 cell embryo is called a morula,which continues to divide to form the blastocyst. The morula moves further into the uterus.
e The cells in the blastocyst are arranged into an outer trophoblast and an inner cell mass. . The trophoblast gets attached to the uterine endometrium, and the process is called implantation. This leads to pregnancy. . The inner cell mass gets differentiated to form the embryo.
Pregnancy, parturition and lactation
Pregnancy e After implantation, the trophoblast forms finger-like projections called chorionic villi, surrounded by the uterine tissue and maternal blood. . The chorionic villi and the uterine tissue get integrated to form the placenta, which helps in supplying the developing embryo with oxygen and nutrients, and is also involved in the removal of waste.
. The placenta is connected to the embryo by the umbilical cord. The placenta acts as an endocrine gland, and produces the human chorionic gonadotropins, human placental lactogen, oestrogen, progesterone and relaxin (later stages of pregnancy) . These hormones support foetal growth and help in the maintenance of pregnancy. Hormones like oestrogen, progestogen, cortisol, prolactin, etc., are increased several folds in the maternal blood. . Immediately after implantation, the inner cell mas:s (embryo) gets differentiated into the ectoderm, mesoderm and endoderm, which give rise to the different tissues. This ability of the inner cell mass is due to the presence of multi-potent cells called stem cells.
. Most of the major organs are formed at the end of 12 weeks of pregnancy; during the 5th month, the limbs and body hair are formed; by the 24th week, the eyelids separate and eyelashes are formed. At the end of nine months, the foetus is fully formed.
. This causes the release of oxytocin from the pituitary, which causes stronger uterine contractions. . This leads to the expulsion of the baby along with the placenta. . During pregnancy, the mammary glands undergo differentiation, and milk is produced during the end of pregnancy . The milk produced during the first few days of lactation is known as colostrums.lt contains several antibodies that aid the newborn to develop resistance.