tailieunhanh - MATERNAL PHYSIOLOGIC

The extruded ovum is directed into a uterine tube by its fimbriae and the peritoneal fluid currents. Normally, a few hours after insemination, spermatozoa will have passed through the cervix and uterus into the fallopian tubes. Capacitation of the sperm (preparation for fertilization) occurs between its passage into the cervix and its reaching the midportion to outer portion of the tube. Fertilization occurs when a spermatozoon penetrates the ovum, usually in the outer portion of the fallopian tube. It is unusual for fertilization to occur more than 24 h after ovulation. Indeed, if this occurs, an ectopic pregnancy may. | MATERNAL PHYSIOLOGIC ADJUSTMENTS TO PREGNANCY FERTILIZATION AND IMPLANTATION THE PLACENTA The extruded ovum is directed into a uterine tube by its fimbriae and the peritoneal fluid currents. Normally a few hours after insemination spermatozoa will have passed through the cervix and uterus into the fallopian tubes. Capacitation of the sperm preparation for fertilization occurs between its passage into the cervix and its reaching the midportion to outer portion of the tube. Fertilization occurs when a spermatozoon penetrates the ovum usually in the outer portion of the fallopian tube. It is unusual for fertilization to occur more than 24 h after ovulation. Indeed if this occurs an ectopic pregnancy may result. The fertilized ovum rapidly develops into an embryonic blastocyst. About 3-4 days are required for this minute free-floating object to reach the uterus. Until implantation the zygote is nourished by adherent granulosa cells and tubal fluids. Progress is mainly by tubal ciliary action but peristalsis probably contributes to tubal transit. Endometrial implantation ensues 5-6 days after fertilization. The favored sites are the anterior and the posterior fundus. This is summarized as follows. Last menstrual period LMP Ovulation Fertilization Ovum transit tube to uterus Ovum free in uterus Implantation Expected period 77 Cycle days 1-7 Day 14 after LMP Day 14-15 after LMP Days 15-19 Days 19-21 Day 19-21 after LMP Missed or scanty Copyright 2001 The McGraw-Hill Companies. Click Here for Terms ofUse. 78 BENSON PERNOLL S HANDBOOK OF OBSTETRICS AND GYNECOLOGY The early developing embryo with its tissue layers is shown in Figure 4-1. The chorion or protective covering of the fertilized developing ovum has an outer ectodermal layer trophoblast The inner layer is mesenchyme. The trophoblast initially a poorly defined syncytium soon develops into two tissue types an outer confluent but differentiated plasmotrophoblast syncytio- or syntrophoblasf and an inner distinct .

TỪ KHÓA LIÊN QUAN