[其它考试]妊娠生理.ppt

Physiology of Reproduction(II) Teng Yincheng M.D., Ph.D., Professor Department Of Obstetrics Gynecology Renji Hospital Affiliated to SJTU School of Medicine Pregnancy occurs when a mature liberated ovum is fertilized by a mature capacitated spermatozoon The Sperm: The spermatozoa leave the testis carrying 23 chromosomes but not yet capable of fertilization. Their maturation is completed through their journey in the 6 meters of the epididymis and when mixed with the seminal plasma from the epididymis, seminal vesicle and prostate gland. The Sperm: After semen is ejaculated, the sperms reach the cervix by their own motility within seconds leaving behind the seminal plasma in the vagina The Sperm: At time of ovulation, the cervical mucous is in the most favourable condition for sperm penetration and capacitation as: It becomes more copious, less viscous and its macromolecules arrange in parallel chains providing channels for sperms passage. Its contents from glucose and chloride are increased. The Sperm: The sperms ascent through the uterine cavity and Fallopian tubes to reach the site of fertilization in the ampulla by: Its own motility, and by Uterine and tubal peristalsis which is aggravated by the prostaglandins in the seminal plasma. The Sperm: The sperms reach the tube within 30-40 minutes But they are capable of fertilization after 2-6 hours. This period is needed for sperm capacitation. Capacitation of sperms Is the process after which the sperm becomes able to penetrate the zona pellucida,that surrounding the ovum and fertilize it. The cervical and tubal secretions are mainly responsible for this capacitation. Capacitation of sperms Capacitation is believed to be due to : Increase in the DNA concentration in the nucleus, Increase perme