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Questions and Answers
Which component of the placental membrane is responsible for forming the endothelial lining of fetal vessels?
Which component of the placental membrane is responsible for forming the endothelial lining of fetal vessels?
What substance is deposited on the outer surface of the placental membrane to decrease permeability at the end of pregnancy?
What substance is deposited on the outer surface of the placental membrane to decrease permeability at the end of pregnancy?
Which of the following correctly describes the fetal blood flow regarding the umbilical arteries?
Which of the following correctly describes the fetal blood flow regarding the umbilical arteries?
Which process does NOT occur via the placental barrier?
Which process does NOT occur via the placental barrier?
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What are the typical components of a full-term umbilical cord?
What are the typical components of a full-term umbilical cord?
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What is the earliest stage of human development after fertilization?
What is the earliest stage of human development after fertilization?
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What happens to the zona pellucida before the early blastocyst stage?
What happens to the zona pellucida before the early blastocyst stage?
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What is the primary role of the syncytiotrophoblast during implantation?
What is the primary role of the syncytiotrophoblast during implantation?
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By which day after fertilization does the blastocyst typically begin the implantation process?
By which day after fertilization does the blastocyst typically begin the implantation process?
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Which layer of the endometrium is referred to as the decidua after implantation?
Which layer of the endometrium is referred to as the decidua after implantation?
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What is the function of the trophoblast after fertilization?
What is the function of the trophoblast after fertilization?
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Which of the following best describes the advanced morula stage?
Which of the following best describes the advanced morula stage?
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What significant change occurs in the embryonic period during organogenesis?
What significant change occurs in the embryonic period during organogenesis?
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What is a potential outcome of caudal dysgenesis?
What is a potential outcome of caudal dysgenesis?
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Which germ layer is primarily involved in forming the urogenital system?
Which germ layer is primarily involved in forming the urogenital system?
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During which week does the primitive streak begin to regress during embryonic development?
During which week does the primitive streak begin to regress during embryonic development?
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What is sacrococcygeal teratoma characterized by?
What is sacrococcygeal teratoma characterized by?
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What term describes the sensitivity of embryos to teratogens during their development?
What term describes the sensitivity of embryos to teratogens during their development?
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What consequence might result from insufficient mesoderm formation?
What consequence might result from insufficient mesoderm formation?
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Which type of embryonic folding is related specifically to the rapid growth of the central nervous system?
Which type of embryonic folding is related specifically to the rapid growth of the central nervous system?
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What is the primary focus of embryonic folding during the early stages of development?
What is the primary focus of embryonic folding during the early stages of development?
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What are the two layers into which the trophoblast differentiates during the second week of development?
What are the two layers into which the trophoblast differentiates during the second week of development?
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Which term describes the extraembryonic mesoderm that covers the yolk sac?
Which term describes the extraembryonic mesoderm that covers the yolk sac?
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Which statement best describes the potency of embryonic stem cells?
Which statement best describes the potency of embryonic stem cells?
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What occurs during the late second week of embryonic development?
What occurs during the late second week of embryonic development?
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What is a critical property of stem cells that allows them to regenerate damaged tissues?
What is a critical property of stem cells that allows them to regenerate damaged tissues?
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Which type of mesoderm is associated with the extraembryonic layer of the amnion?
Which type of mesoderm is associated with the extraembryonic layer of the amnion?
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During which developmental stage does the hypoblast begin to spread beneath the cytotrophoblast?
During which developmental stage does the hypoblast begin to spread beneath the cytotrophoblast?
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Which of the following is a source of adult stem cells?
Which of the following is a source of adult stem cells?
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What does self-renewal in stem cells refer to?
What does self-renewal in stem cells refer to?
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What is the primary function of the allantois during embryonic development?
What is the primary function of the allantois during embryonic development?
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Meckel’s diverticulum is primarily caused by which of the following?
Meckel’s diverticulum is primarily caused by which of the following?
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Which congenital anomaly results from the obliteration of the intraembryonic part of the allantois?
Which congenital anomaly results from the obliteration of the intraembryonic part of the allantois?
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How far is Meckel’s diverticulum typically located from the ileocaecal junction?
How far is Meckel’s diverticulum typically located from the ileocaecal junction?
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What abnormality is associated with the urachus after birth?
What abnormality is associated with the urachus after birth?
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Which of the following anomalies is not typically associated with the allantois?
Which of the following anomalies is not typically associated with the allantois?
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What percentage of the population is estimated to have Meckel’s diverticulum?
What percentage of the population is estimated to have Meckel’s diverticulum?
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During embryonic development, the yolk stalk's persistence is most likely to result in which condition?
During embryonic development, the yolk stalk's persistence is most likely to result in which condition?
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Which condition develops from an issue with the cloacal membrane during embryonic folding?
Which condition develops from an issue with the cloacal membrane during embryonic folding?
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What is the fate of the distal portion of the allantois after embryonic development?
What is the fate of the distal portion of the allantois after embryonic development?
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Study Notes
Fertilization, Cleavage, and Implantation
- Fertilization is the fusion of mature sperm and ovum, forming a zygote.
- Fertilization occurs in the ampullary part of the uterine tube.
- Sperm must undergo capacitation and acrosome reaction to fertilize the oocyte.
- Sperm structure includes a head (nucleus and acrosome), midpiece (mitochondria), and tail (flagellum).
- The acrosome contains enzymes (acrosin and others) to penetrate the zona pellucida.
- Sperm motility relies on mitochondria and flagella.
- Mitochondrial inheritance is solely maternal.
Phases of Fertilization
- Phase 1: Penetration of the corona radiata
- Phase 2: Penetration of the zona pellucida
- Phase 3: Fusion of oocyte and sperm cell membranes
Results of Fertilization
- Restoration of diploid number of chromosomes.
- Determination of the sex of the new individual.
- Initiation of cleavage; the oocyte usually degenerates within 24 hours after ovulation without fertilization.
Cleavage
- A series of mitotic divisions increasing the number of cells.
- Occurs in the uterine tube, medial to the ampulla.
- Stages: morula stage
Blastocyst Formation
- Morula develops into a fluid-filled blastocyst.
- Inner cell mass (ICM) forms the embryo.
- Trophoblast forms the fetal part of the placenta.
- Blastocyst implants in the uterine wall.
- Zona pellucida disappears before implantation.
Implantation
- Penetration of the blastocyst into the uterine endometrium.
- Occurs approximately 6 to 11 days after fertilization.
- Normal site is in the endometrium of the anterior or posterior wall of the uterus, near the middle line.
- Trophoblast differentiates into cytotrophoblast and syncytiotrophoblast.
- Syncytiotrophoblast erodes uterine tissues, allowing blastocyst embedding.
- Implantation completes the formation of the decidua.
The Decidua
- The endometrium after blastocyst implantation.
- Types: decidua basalis, capsularis, and parietalis.
Clinical Correlates
- Abnormal Implantation (Ectopic Pregnancy): Implantation outside the uterus (typically fallopian tube).
- Abnormal sites of implantation: Uterine ectopic pregnancy (cornu, lower segment, cervix); extra-uterine pregnancy (fallopian tube, ovary).
- Placenta previa: Implantation of the blastocyst in the lower segment of the uterus.
The Second and Third Week of Development
- Blastocyst embedding in the uterine wall.
- Trophoblast differentiates into cytotrophoblast and syncytiotrophoblast.
- Inner cell mass differentiates into epiblast and hypoblast.
- Formation of the amniotic cavity and yolk sac.
- Formation of the bilaminar disc (epiblast and hypoblast).
The Embryonic Period
- Embryonic period (3rd-8th week).
- Major organogenesis occurs.
- Folding of the embryo.
- Cephalocaudal and lateral folding.
- Somitogenesis, developing somites, paired blocks of mesoderm.
Differentiation of the Mesoderm
- Forms paraxial, intermediate, and lateral plate mesoderm.
- Paraxial mesoderm gives rise to somites.
- Development of the neural tube begins.
- Intermediate mesoderm gives rise to the excretory and reproductive systems.
- Lateral plate mesoderm gives rise to the serosal membranes and several parts of the circulatory system.
Endodermal Derivatives
- Epithelial lining of the gastrointestinal tract, respiratory tract (lungs), and urinary bladder.
- Parenchyma of the thyroid, parathyroids, liver, and pancreas.
Ectodermal Derivatives
- Central nervous system
- Peripheral nervous system
- Sensory epithelium of ear, nose, and eyes
- Skin, including hair and nails
- Pituitary, mammary, sweat glands, and tooth enamel.
Neurulation
- Formation of the neural tube (primordium of the central nervous system).
- Development of the neural crest.
Clinical Applications
- Disruption in gastrulation (sirenomelia) due to insufficient mesoderm formation.
- Sacrococcygeal teratomas.
The Fetal Membranes
- Development of chorionic villi.
- Formation of the chorionic plate, decidual plate, and intervillous spaces.
- Types of villi (primary, secondary, tertiary).
- Chorion frondosum (villi on the fetal side) and chorion laeve (smooth fetal surface).
The Placenta
- Fetal and maternal portions (chorion frondosum and decidua basalis).
- Formation of intervillous spaces.
- Nutrient and waste exchange between maternal and fetal blood.
- Placental barrier.
Umbilical Cord
- Structures: arteries, vein, and Wharton's jelly.
- Connection to the fetus and placenta.
- Formation of the umbilical cord from the body stalk.
- Obliteration of the yolk stalk and allantois.
- Components: umbilical arteries, umbilical vein, and Wharton's jelly.
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Description
This quiz explores the processes of fertilization, cleavage, and implantation in human reproduction. It covers the phases of fertilization, sperm structure, and the results after fertilization. Test your knowledge on these essential biological concepts.
