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Example Question #22 : Reproductive System
What were the effects of thalidomide on pregnant women when it was used to treat morning sickness during the 1950’s?
Limb deformities
Carcinogenicity of the fetus
Maternal-fetal incompatibility
Miscarriage
Limb deformities
During the 1950’s, thalidomide was an over-the-counter drug advertised and used to treat morning sickness in pregnant women. Thalidomide was later found to cause limb and skeletal deformities in resulting fetuses. Subsequently, the sale and use of the drug has ended.
Example Question #21 : Reproductive Physiology
Which of the following contributes to the formation of the blastocoel during blastula development?
Cell polarization
Compaction of trophoblasts
All of these
Gap junctions between embryoblasts
All of these
The blastocoel is a fluid-fill cavity region of the blastocyst. The blastocoel is formed through cell polarization, when trophoblasts and embryoblasts differentiate. The trophoblasts are the outer layer of cells that compact to become watertight. Embryoblasts polarize to one end of the cell and form gap junctions for cell-cell communication and developmental coordination. The trophoblasts then secrete fluid into the cavity, which forms the blastocoel.
Example Question #30 : Reproductive System
Which of the following cell types secrete fluid into the cavity during the formation of the blastocoel during blastula development?
Embryoblast
Trophoblast
Synctiotrophoblast
Epiblast
Trophoblast
The blastocoel is a fluid-filled cavity that is a part of the blastocyst. A compacted trophoblast cell layer surrounds the cavity, making it watertight. Trophoblast cells then secret fluid into the cavity.
Example Question #22 : Reproductive Physiology
Which of the following best describes when the zona pellucida disintegrates?
After implantation into the uterine wall
Immediately following fertilization as a result of the cortical reaction
After an increase in blastocyst size and subsequent zona pellucida "hatching"
Before the onset of cleavage to allow for growth
After an increase in blastocyst size and subsequent zona pellucida "hatching"
The zona pellucida is a glycoprotein layer secreted by follicle cells that surrounds the released oocyte and developing embryo. Once the blastocoel grows in size during blastula development, the blastocyst “hatches” out of the zone pellucida, which then disintegrates.
Example Question #23 : Reproductive Physiology
Which of the following steps does not precede blastocyst implantation in the uterine wall?
Initial loose contacts between the blastocyst and the uterine wall
Breakdown of the endometrial extracellular matrix
Irreversible connections between the blastocyst and the uterine wall
"Hatching" from the zona pellucida
Irreversible connections between the blastocyst and the uterine wall
Implantation is the process in which a blastocyst adheres to the female uterine wall. This is preceded by the exit of the blastocyst form the zona pellucida as well as the degradation of the endometrial extracellular matrix by proteolytic enzymes secreted by the blastocyst and initial loose connections with the endometrium. The blastocyst then adheres to the uterine wall through ligand-receptor systems and cell invasion.
Example Question #24 : Reproductive Physiology
Which of the following is the leading cause of implantation failure?
Decreased uterine receptivity
Embryo abnormalities
Medication
Foreign substance interference
Decreased uterine receptivity
The leading cause of implantation failure is decreased uterine receptivity. Other causes include problems with the developing embryo. Certain medications can be administered to increase chances of successful implantation.
Example Question #34 : Reproductive System
Which of the following cell layers both ingressions and invaginates during gastrulation?
Trophoblast
Hypoblast
Blastocoel
Epiblast
Epiblast
The epiblast is an inner cell layer in the blastocoel that sits above the hypoblast. The epiblast ingresses to form the mesoderm and invaginates to form the endoderm.
Example Question #35 : Reproductive System
Which of the following is established by the primitive streak during gastrula development?
Bilateral symmetry
Cranial/caudal axes
Left/right axes
All of these
All of these
The primitive streak is an arrangement of cells that forms during gastrula development. The location of the primitive streak establishes the left/right axes, cranial/caudal axes, and bilateral symmetry of the developing embryo.
Example Question #36 : Reproductive System
The process of ingression forms which of the following germ layers during gastrula development?
None of these
Mesoderm
Endoderm
Ectoderm
Mesoderm
In gastrulation, the process of ingression forms the mesoderm. In this process, the epiblast ingresses at the primary streak into the area between the epiblast and hypoblast cell layers.
Example Question #261 : Systems Physiology
During which of the following stages of embryonic development does the process of invagination occur?
Blastula development
Implantation
Gastrulation
Fertilization
Gastrulation
Invagination is the infolding of the epiblast cell layer to form the endoderm germ layer. This process takes place during gastrulation.
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