Podcast
Questions and Answers
What is the cavity formed in the blastocyst stage?
What is the cavity formed in the blastocyst stage?
- Trophectoderm
- Endoderm
- Amniotic cavity
- Blastocele (correct)
What is the function of proteolytic enzymes secreted by syncytiotrophoblasts?
What is the function of proteolytic enzymes secreted by syncytiotrophoblasts?
- To prevent menstruation
- To stimulate uterine contractions
- To produce human chorionic gonadotropin
- To implant the embryo in the uterus (correct)
During which phase of the menstrual cycle does the uterine endometrium prepare for implantation?
During which phase of the menstrual cycle does the uterine endometrium prepare for implantation?
- Proliferative phase
- Menstrual phase
- Secretory phase (correct)
- Ovulation phase
What is the function of human chorionic gonadotropin (hCG) secreted by syncytiotrophoblasts?
What is the function of human chorionic gonadotropin (hCG) secreted by syncytiotrophoblasts?
What is the term for the outer cell mass that forms the epithelial wall of the blastocyst?
What is the term for the outer cell mass that forms the epithelial wall of the blastocyst?
During which day of pregnancy do the trophoblastic cells begin to penetrate the uterine mucosa?
During which day of pregnancy do the trophoblastic cells begin to penetrate the uterine mucosa?
During which stage of development does fertilization occur?
During which stage of development does fertilization occur?
Where does fertilization typically occur?
Where does fertilization typically occur?
What is the purpose of the acrosome reaction?
What is the purpose of the acrosome reaction?
What is the result of ovulation?
What is the result of ovulation?
What is the function of capacitation?
What is the function of capacitation?
During which day of a regular 28-day menstrual cycle does ovulation occur?
During which day of a regular 28-day menstrual cycle does ovulation occur?
What is the correct order of the phases of fertilization?
What is the correct order of the phases of fertilization?
What is the term for the period from 0-2 weeks of development?
What is the term for the period from 0-2 weeks of development?
What is the role of the enzymes in the acrosome?
What is the role of the enzymes in the acrosome?
What happens to the oocyte if it is not fertilized within 24 hours of ovulation?
What happens to the oocyte if it is not fertilized within 24 hours of ovulation?
What is the result of the cortical and zona reactions?
What is the result of the cortical and zona reactions?
What is the significance of the diploid number of chromosomes being restored?
What is the significance of the diploid number of chromosomes being restored?
What is the result of the resumption of the second meiotic division?
What is the result of the resumption of the second meiotic division?
What is the term for the series of mitotic divisions that occur after fertilization?
What is the term for the series of mitotic divisions that occur after fertilization?
What is the term for the cells that result from cleavage?
What is the term for the cells that result from cleavage?
What is the stage of development that occurs approximately 3 days after fertilization?
What is the stage of development that occurs approximately 3 days after fertilization?
What is the process called when syncytiotrophoblasts erode the endometrium and the blastocyst burrows into the compact layer of endometrium?
What is the process called when syncytiotrophoblasts erode the endometrium and the blastocyst burrows into the compact layer of endometrium?
What is the structure that forms from the hypoblast?
What is the structure that forms from the hypoblast?
What is the most common type of ectopic pregnancy?
What is the most common type of ectopic pregnancy?
What is the layer of the endometrium that the blastocyst burrows into during implantation?
What is the layer of the endometrium that the blastocyst burrows into during implantation?
What is the membrane that forms from the epiblast?
What is the membrane that forms from the epiblast?
When does the completion of implantation occur?
When does the completion of implantation occur?
What is the most common type of ectopic pregnancy?
What is the most common type of ectopic pregnancy?
What is the role of Early Pregnancy Factor (EPF)?
What is the role of Early Pregnancy Factor (EPF)?
During In Vitro Fertilization, what is the purpose of hormonal stimulation?
During In Vitro Fertilization, what is the purpose of hormonal stimulation?
What is the result of dispermy?
What is the result of dispermy?
What is the stage of development after fertilization?
What is the stage of development after fertilization?
What is the purpose of an assay of HCG and Progesterone?
What is the purpose of an assay of HCG and Progesterone?
What is the term for a pregnancy that attaches to the mesenteric blood vessels?
What is the term for a pregnancy that attaches to the mesenteric blood vessels?
What is the stage of development where the zygote is transferred to the uterine cavity?
What is the stage of development where the zygote is transferred to the uterine cavity?
Study Notes
Stages of Prenatal Development
- Zygotic (or Germinal) Stage: 0-2 weeks
- Embryonic Stage: 2-8 weeks
- Fetal Stage: 9-40 weeks
Ovulation
- Event in which a mature oocyte is expelled from the ovary
- Occurs 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:
- Phase 1: Penetration of the corona radiata
- Phase 2: Penetration of the zona pellucida
- Phase 3: Fusion of the oocyte and sperm cell membranes
Capacitation
- Only capacitated sperm can pass through the corona cells and undergo the acrosome reaction
- Acrosome reaction: Release of enzymes needed to penetrate the zona pellucida, including acrosin and trypsin-like substances
Results of Fertilization
- Restoration of the diploid number of chromosomes
- Determination of the sex of the new individual
- Initiation of cleavage
Cleavage
- Series of mitotic divisions, increasing the number of cells
- Cells, known as blastomeres, become smaller with each cleavage division
- Approximately 3 days after fertilization, cells divide again to form a 16-cell morula
Blastocyst Formation
- Fluid penetrates the zona pellucida, forming a single cavity, the blastocele
- Embryoblast and outer cell mass, or trophoblast, flatten and form the epithelial wall of the blastocyst
- Zona pellucida disappears, allowing implantation to begin
Implantation
- Trophoblastic cells over the embryoblast pole begin to penetrate between the epithelial cells of the uterine mucosa
- Approximately 6th day after fertilization
Syncytiotrophoblasts
- Show villous projections and lacunar spaces
- Secrete:
- Proteolytic enzymes, which erode the endometrium to implant
- HCG, which sustains the corpus luteum
Uterus at Time of Implantation
- Uterine endometrium passes through three stages:
- Menstrual phase
- Proliferative phase (influenced by estrogen)
- Secretory phase (influenced by progesterone produced by the corpus luteum)
Ectopic Pregnancy
- Most common type: Tubal pregnancy
- May secondarily attach itself to mesenteric blood vessels and continue as abdominal pregnancy
- Rarely: Falls into the pouch of Douglas
Pregnancy Tests
- Early Pregnancy Factor (EPF): appears in 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 5th week
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Description
Learn about the stages of development from conception to birth, including ovulation, fertilization, cleavage, and implantation. Test your knowledge of prenatal development.
