36 Questions
What is the normal site of fertilization?
Ampullary region of the uterine tube
What is the result of the acrosome reaction?
Release of enzymes needed to penetrate the zona pellucida
During which stage of development does the fertilized egg begin to implant in the uterus?
Zygotic Stage
What is the function of capacitation in sperm?
To facilitate penetration of the corona radiata
During which day of a regular 28-day menstrual cycle does ovulation occur?
14th day
What is the term for the process of fertilization?
Fusion
What is the purpose of the zona pellucida?
To facilitate fertilization by blocking polyspermy
What is the term for the stage of development from 2-8 weeks?
Embryonic Stage
What is the primary function of syncytiotrophoblasts during implantation?
To erode the endometrium and allow the blastocyst to burrow into the compact layer
During which days does the process of implantation occur?
5th to 10th day
What is the name of the membrane that forms from the hypoblast layer?
Exocoelomic membrane
What is the most common type of ectopic pregnancy?
Tubal pregnancy
What is the name of the cavity that forms from the epiblast layer?
Amniotic cavity
What is the name of the structure that closes the entrance to the blastocyst in the uterine cavity?
Closing plug
What is the characteristic of cells until the 8-cell stage?
They are totipotent
What is the stage of development when the cells are arranged in a hollow sphere?
Blastocyst
What is the outer layer of the blastocyst that will eventually form the placenta?
Trophoblast
At what stage does the zona pellucida disappear?
By day 5-6
What is the stage of development when the cells are in a compact, solid ball of cells?
Morula
What is the rate of cell division after 72 hours?
32 cells
What is the structure that surrounds the oocyte and the early embryo?
Zona pellucida
When does the morula reach the uterus?
By day 3
What is the primary function of the syncytiotrophoblasts during implantation?
Secreting proteolytic enzymes to erode the endometrium
During which stage of the uterine endometrium does implantation typically occur?
Secretory phase
What is the primary function of human chorionic gonadotropin (hCG) produced by the syncytiotrophoblasts?
Sustaining the corpus luteum
What is the term for the fluid-filled cavity that forms during blastocyst formation?
Blastocele
What is the primary function of the trophoblast during blastocyst formation?
Forming the epithelial wall of the blastocyst
At which stage of embryonic development have the cells not yet specialized for function?
Undifferentiated stage
What is the rare location where an ectopic pregnancy may fall into?
Pouch of Douglas
What is the timeframe by which Early Pregnancy Factor (EPF) appears in maternal serum?
24-48 hours
What is the stage at which a zygote is transferred to the uterine cavity during In Vitro Fertilization?
4-8 cell stage
What is the result of dispermy during fertilization?
Triploidy
What is the purpose of hormonal stimulation during In Vitro Fertilization?
To form several mature follicles
What is the timeframe by which pregnancy can be confirmed using ultrasonogram?
By the end of 5th week
What is the type of ectopic pregnancy that can secondarily attach to mesenteric blood vessels?
Abdominal pregnancy
What is the type of implantation that occurs at the internal os?
Cervical implantation
Study Notes
Stages of Prenatal Development
- Divided into three stages: Zygotic (0-2 weeks), Embryonic (2-8 weeks), and Fetal (9-40 weeks)
Ovulation
- Event in which a mature oocyte is expelled from the ovary, occurring on the 14th day of a regular 28-day menstrual cycle
Fertilization
- Process by which male and female gametes fuse, occurs in the ampullary region of the uterine tube
- Phases of fertilization:
- Penetration of the corona radiata
- Penetration of the zona pellucida
- Fusion of the oocyte and sperm cell membranes
- Capacitation: only capacitated sperm can pass through the corona cells and undergo the acrosome reaction, releasing enzymes needed to penetrate the zona pellucida
Cleavage
- Mitotic division resulting in blastomeres, with totipotency until the 8-cell stage
- Rate of cell division:
- 36 hours: 2 cells
- 48 hours: 8 cells
- 72 hours: 32 cells
- 96 hours: 70 cells
Blastocyst Formation
- Fluid begins to penetrate through the zona pellucida into the intercellular spaces of the inner cell mass, forming a single cavity, the blastocele
- The embryoblast is at one pole, and the outer cell mass, or trophoblast, flattens and forms the epithelial wall of the blastocyst
- The zona pellucida has disappeared, allowing implantation to begin
Implantation
- The trophoblastic cells over the embryoblast pole begin to penetrate between the epithelial cells of the uterine mucosa around the sixth day
- Syncytiotrophoblasts secrete proteolytic enzymes which erode the endometrium to implant and human chorionic gonadotropin (hCG) which sustains the corpus luteum
Uterus at Time of Implantation
- The uterine endometrium passes through three stages during the menstrual cycle: menstrual phase, proliferative phase, and secretory phase
Ectopic Pregnancy
- Most common type is tubal pregnancy, which may secondarily attach itself to mesenteric blood vessels and continue as abdominal pregnancy
- Rarely, it may fall into the pouch of Douglas
Pregnancy Tests
- Early Pregnancy Factor (EPF) appears in the maternal serum by 24 to 48 hours
- Assay of hCG and progesterone by the end of the second week
- Confirmation of pregnancy by ultrasonogram by the end of the fifth week
This quiz covers the stages of development from ovulation to implantation in the first week of pregnancy, including fertilization, cleavage, and implantation.
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