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Questions and Answers
During which stage of development does the amniotic cavity appear?
During which stage of development does the amniotic cavity appear?
Which of the following processes is responsible for the formation of the primitive streak and primitive node?
Which of the following processes is responsible for the formation of the primitive streak and primitive node?
What is the primary function of the chorionic villi?
What is the primary function of the chorionic villi?
Which of the following is NOT a function of the amniotic fluid?
Which of the following is NOT a function of the amniotic fluid?
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Which of the following is a characteristic of a dizygotic twin pregnancy?
Which of the following is a characteristic of a dizygotic twin pregnancy?
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The primitive streak establishes the craniocaudal axis of the embryo.
The primitive streak establishes the craniocaudal axis of the embryo.
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The notochord is a permanent structure that forms the basis for the vertebral column.
The notochord is a permanent structure that forms the basis for the vertebral column.
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The splanchnic mesoderm forms the lining of the body cavities, including the pleura and peritoneum.
The splanchnic mesoderm forms the lining of the body cavities, including the pleura and peritoneum.
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The yolk sac is responsible for the formation of the entire digestive system.
The yolk sac is responsible for the formation of the entire digestive system.
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The chorion is a fetal membrane that directly contributes to the formation of the placenta.
The chorion is a fetal membrane that directly contributes to the formation of the placenta.
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What is the name of the process that involves the epiblast cells migrating through the primitive streak to form the three germ layers?
What is the name of the process that involves the epiblast cells migrating through the primitive streak to form the three germ layers?
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What is the function of the amnioectodermal junction?
What is the function of the amnioectodermal junction?
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Name the embryonic structure that eventually gives rise to the vertebral column.
Name the embryonic structure that eventually gives rise to the vertebral column.
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What are the three types of placenta previa?
What are the three types of placenta previa?
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What are the two types of twins?
What are the two types of twins?
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Name the three germ layers that form during gastrulation.
Name the three germ layers that form during gastrulation.
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What is the function of the connecting stalk?
What is the function of the connecting stalk?
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What are the two main components of the placenta?
What are the two main components of the placenta?
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What is the name of the jelly-like substance found in the umbilical cord?
What is the name of the jelly-like substance found in the umbilical cord?
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What is the name of the structure that connects the yolk sac to the midgut?
What is the name of the structure that connects the yolk sac to the midgut?
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What are the two main types of chorionic villi?
What are the two main types of chorionic villi?
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What is the name of the structure that forms the roof of the primitive pit during notochord formation?
What is the name of the structure that forms the roof of the primitive pit during notochord formation?
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What is the name of the condition where the umbilical cord is attached to the placenta at a point other than its center?
What is the name of the condition where the umbilical cord is attached to the placenta at a point other than its center?
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What is the name of the membrane that separates the amniotic cavity from the chorionic cavity?
What is the name of the membrane that separates the amniotic cavity from the chorionic cavity?
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What is the name of the condition where twins are joined at some point in their bodies?
What is the name of the condition where twins are joined at some point in their bodies?
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What is the name of the condition where the placenta is abnormally implanted in the lower segment of the uterus?
What is the name of the condition where the placenta is abnormally implanted in the lower segment of the uterus?
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What is the name of the process by which the embryonic disc folds upon itself to form a cylindrical shape?
What is the name of the process by which the embryonic disc folds upon itself to form a cylindrical shape?
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What are the three main parts of the lateral plate mesoderm?
What are the three main parts of the lateral plate mesoderm?
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What is the name of the condition where a pregnant woman has more than one baby?
What is the name of the condition where a pregnant woman has more than one baby?
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What is the name of the membrane that separates the fetal blood from the maternal blood in the placenta?
What is the name of the membrane that separates the fetal blood from the maternal blood in the placenta?
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What is the name of the process by which the embryonic disc transforms from a bilaminar disc into a trilaminar disc?
What is the name of the process by which the embryonic disc transforms from a bilaminar disc into a trilaminar disc?
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What is the name of the structure that forms the boundary between the amniotic cavity and the yolk sac?
What is the name of the structure that forms the boundary between the amniotic cavity and the yolk sac?
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What is the name of the condition where the umbilical cord is abnormally short?
What is the name of the condition where the umbilical cord is abnormally short?
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What is the name of the process by which the embryonic disc is divided into three germ layers?
What is the name of the process by which the embryonic disc is divided into three germ layers?
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What is the name of the temporary sac that replaces the blastocele of the blastocyst?
What is the name of the temporary sac that replaces the blastocele of the blastocyst?
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What is the name of the disorder that occurs due to the partial deletion of chromosome 15?
What is the name of the disorder that occurs due to the partial deletion of chromosome 15?
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What is the name of the process by which cells differentiate into specialized cells?
What is the name of the process by which cells differentiate into specialized cells?
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Study Notes
General Embryology
- Images show the stages of fetal development at (A) 3rd month, (B) 5th month, and (C) at birth.
Male and Female Gametes
- Gametes (sperm and ova) are reproductive cells formed from primordial germ cells.
- Spermatogenesis occurs in males, starting at puberty and continuing throughout life.
- Oogenesis starts in females during prenatal life, is arrested, and continues from puberty to menopause.
- Ovulation occurs roughly on day 14 of the ovarian cycle.
- Sperm is approximately 55 microns long and has a head, neck, middle piece, and tail. The head contains the condensed nucleus with hereditary material and acrosomal cap with enzymes for fertilization.
- The middle piece contains mitochondria for energy.
- The tail directs movement towards the ovum.
- The mature ovum is about 120 microns in diameter and contains the ootid (mature oocyte) with the nucleus carrying the mother's hereditary material (22 autosomes and X), cytoplasm as a nutrition source, zona pellucida (glycoprotein coat for sperm attraction), and corona radiata (outer layer formed of follicular cells).
First Week of Development
- Fertilization is the union of a sperm and egg to form a zygote. It occurs in the ampulla of the uterine tube.
- Sperm capacitation involves removing the glycoprotein coat from the acrosomal region of the sperms, taking about 7 hours to be completed
- Sperm penetration through the corona radiata and zona pellucida occurs.
- The sperm fuses with the oocyte's cell membrane and releases its contents (nucleus, neck, middle piece, and axial filament), while the sperm cell membrane remains on the oocyte surface.
- Cortical and zona reactions prevent polyspermy.
Second Week of Development
- Implantation is the embedding of the blastocyst within the endometrium, starting from day 7 and completing by day 11.
- The endometrium is in the secretory phase during implantation, characterized by increased thickness, increased number and size of endometrial cells, and spiral arteries.
- Abnormal implantation sites include ectopic pregnancies (tubal, ovarian, or omental).
- Placenta previa is a pathological condition involving implantation of the fertilized ovum in the lower segment of the uterus, potentially posing risks to both mother and child.
Third Week of Development
- Gastrulation: Blastocyst undergoes restructuring
- Formation of primitive streak triggers the formation of 3 primary germ layers (endoderm, ectoderm, and mesoderm).
- Formation of the chorion, a fetal membrane, begins
- Formation of the chorionic villi, which are crucial for placental function, begins.
Fourth to Eighth Week of Development
- Organogenesis: The formation of most major organs begins.
- Neural crest cells generate a variety of tissues and organs.
- Neural tube development leads to the central nervous system.
- Formation of the brain, spinal cord, and peripheral nerves.
- Formation of the heart and blood vessels.
- Formation of limbs and other anatomical structures.
Fetal Membranes
- The chorion, amnion, and yolk sac are fetal membranes providing nourishment, gas exchange, and protection.
- The placenta, an organ composed of both maternal and fetal tissue, provides metabolic exchange that includes nutrients, oxygen, and waste products.
- Formation of umbilical cord connecting fetus and placenta.
Umbilical Cord
- The umbilical cord has three structures (two arteries and one vein) enclosed in a gelatinous matrix called Wharton's jelly.
- Crucial for fetal development, nutrition, and waste removal during pregnancy.
Yolk Sac
- Blastocyst undergoes a transformation from an inner cell mass to three germ layers.
- The yolk sac produces primordial germ cells for the development of various structures and organs.
Fetal Period and Birth Defects
- Fetal period encompasses the period extending from week 9 of gestation to birth and marked by the rapid maturation of tissues and organs.
- Birth defects result from environmental factors, chromosomal abnormalities, and genetic conditions.
- Different types of twins have differing placental and developmental issues.
Environmental Factors and Chromosomal Abnormalities
- Environmental factors during pregnancy, such as infections, radiation, drugs, and chemicals, can cause birth defects and harm the developing fetus.
- Chromosomal abnormalities like Down syndrome can affect the growth and function of various organ systems.
Fetal Therapy
- Medical interventions during pregnancy can provide treatment for fetal abnormalities or disorders.
- Stem cells therapy and gene therapy are experimental techniques for treating defects and disorders.
Folding
- During the third and fourth weeks of development, the embryo undergoes essential folding for creating its three-dimensional form.
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Description
This quiz covers key concepts in general embryology, focusing on fetal development stages and the processes of male and female gamete formation. Learn about spermatogenesis, oogenesis, and the characteristics of sperm and ova. Test your knowledge on the developmental timeline and cellular structures involved in reproduction.
