Embryology - Part 1 Flashcards
During embryonic development, what event occurs on day six?
Implantation in the uterine wall
What is the gene that is expressed at the base of limbs in a zone of polarizing activity?
Sonic hedgehog (SHH) gene
The sonic hedgehog gene regulates patterning along the _____ (anterior-posterior or cranial-caudal) axis.
anterior-posterior
Name 2 genes expressed at the apical ectodermal ridge (the thickened ectoderm at the distal end of each developing limb).
Wnt-7 and FGF
What is the gene responsible for proper organization along the dorsal-ventral axis?
Wnt-7
What gene is responsible for the lengthening of limbs?
FGF
Which embryonic layer responds to products of the FGF gene?
The mesoderm
How does the FGF gene cause limbs to lengthen?
It stimulates mitosis of the underlying mesoderm
What phenotype would be seen if there was a mutation in the homeobox gene?
There would be defects in segmental organization
Day 0 of fetal life is marked by the _____ of an ovum by a sperm.
Fertilisation
What is formed when a sperm fertilizes an ovum?
The zygote
At what stage of fetal development does implantation occur?
The blastocyst stage
The embryo exists as a _____ disk during the second week of development.
Bilaminar
What two layers make up the bilaminar disk?
The epiblast and the hypoblast
During fetal development, the process of _____ occurs during the third week, which gives rise to a trilaminar disk.
Gastrulation
If an embryo has a notochord and the neural plate is beginning to form, how many weeks old is the embryo?
3 weeks old
If an embryo has a primitive streak, how many weeks old is the embryo?
3 weeks old
During what part of embryonic development does organogenesis occur?
Weeks 3-8
In an embryo, the neural tube forms from a neural plate between which days?
Days 18-21
The embryo is most susceptible to teratogens during what time period?
Weeks 3-8
During what week of development does the heart of an embryo begin to beat?
Week 4
During what week of embryonic development do the upper and lower limb buds begin to form?
Week 4
When is the first time the fetus begins to move and looks like a baby?
Week 8
During what week of development do embryos first have genitalia with either male or female characteristics?
Week 10
During embryonic development, what stage begins on day 2?
The zygote stage (2 haploid cells form a single diploid cell)
During embryonic development, what stage begins on day 3?
The morula stage (morula is latin for mulberry and occurs after the 16-cell stage)
During embryonic development, what stage begins on day 5?
The blastocyst stage (containing an outer layer of cells and an inner cell mass)
During embryonic development, what event occurs on day 6?
Implantation
What embryonic structure implants itself into the uterine wall on day 6?
The blastocyst
After the primitive streak, name three structures formed by neural precursor tissue.
Neural plate, neural crest, and neural tube
The alar plate is on the _____ side of the neural tube, while the basal plate is on the _____ side.
dorsal ; ventral
What is the function of the neurons derived from the alar plate?
Sensory
What is the function of the neurons derived from the basal plate?
Motor
What are the two cell layers that are present during the second week of embryonic development?
The epiblast and the hypoblast (remember: 2germ layers at 2weeks)
What are the two cavities that are present during the second week of embryonic development?
The amniotic sac and the yolk sac (remember: 2cavities at 2weeks)
What are the two components of the placenta that are present during the second week of development?
The cytotrophoblast and the syncytiotrophoblast
remember: 2 components of the placenta at 2 weeks
What three cell layers are present during the third week of embryonic development?
Ectoderm, mesoderm, and endoderm
remember: 3 germ layers at 3 weeks
When is the earliest you expect to see four heart chambers?
At 4 weeks
remember: 4 heart chambers at 4 weeks
When do the four limb buds appear?
At 4 weeks (remember: 4 limb buds at 4 weeks)
An embryo with three germ cell layers is known as a _____.
Gastrula
During fetal development, what cell layer of the bilaminar disk gives rise to the ectoderm?
The epiblast
During fetal development, the _____ of the bilaminar disc invaginates during the process of gastrulation to form the _____ _____.
Epiblast; primitive streak
Name two germ layers that arise from cells of the primitive streak.
Endoderm and mesoderm
During fetal development, the adenohypophysis is derived from the _____ _____, and the neurohypophysis is derived from the _____.
Surface ectoderm; neuroectoderm
During fetal development, what germ layer gives rise to the lens of the eye?
The surface ectoderm
What germ cell layer gives rise to the cells in the retina?
The neuroectoderm
During fetal development, _____ typically forms the CNS and brain, while _____ typically forms the PNS and non-neural structures nearby.
neuroectoderm; neural crest cells
During fetal development, what germ layer gives rise to the epithelial linings of the oral cavity, eye, ear and nose, and to the epidermis?
The surface ectoderm
What germ cell layer gives rise to salivary, sweat, and mammary glands?
The surface ectoderm
During fetal development, what germ layer gives rise to central nervous system neurons?
The neuroectoderm
During fetal development, the supporting cells of the central nervous system (the oligodendrocytes, the astrocytes, and the ependymal cells) are all derived from the _____, except for the microglia, which arise from the _____.
Neuroectoderm; mesoderm
During fetal development, what germ cell layer gives rise to the pineal gland?
The neuroectoderm
What cell type ultimately gives rise to the autonomic nervous system?
The neural crest cells
During fetal development, the dorsal root ganglia are derived from _____.
Neural crest cells
During fetal development, central nervous system neurons are derived from the _____, whereas the cranial nerves are derived from _____.
neuroectoderm; neural crest cells
During fetal development, central nervous system neurons arise from the _____, whereas autonomic nervous system neurons arise from _____.
neuroectoderm; neural crest cells
During fetal development, epidermal cells are derived from the _____, whereas melanocytes are derived from _____.
ectoderm; neural crest cells
During fetal development, the chromaffin cells of the adrenal medulla are derived from the _____, and the adrenal cortex is derived from the _____.
neural crest cells; mesoderm
During fetal development, the pia and arachnoid are derived from the _____, whereas the dura mater is derived from the _____.
neural crest cells; mesoderm
During fetal development, the celiac ganglia are derived from the _____.
neural crest cells
During fetal development, Schwann cells are derived from the _____, whereas oligodendrocytes are derived from the _____.
neural crest cells; neuroectoderm
During fetal development, odontoblasts are derived from the _____.
Neural crest cells (remember: odonto = teeth; think Crest toothpaste)
During fetal development, the follicular cells of the thyroid are derived from _____, whereas the parafollicular cells (C cells) are derived from the _____.
endoderm; neural crest cells
During fetal development, cartilage is generally derived from the _____, except for the laryngeal cartilage, which arises from the _____.
mesoderm; neural crest cells
During fetal development, bones are generally derived from the _____, except for the bones of the skull, which arise from the _____.
mesoderm; neural crest cells
During fetal development, what germ layer gives rise to the muscle?
The mesoderm
During fetal development, what germ cell layer gives rise to the heart?
The mesoderm
During fetal development, what germ cell layer gives rise to the blood vessels?
The mesoderm
During fetal development, what germ cell layer gives rise to the lymphatics?
The mesoderm
During fetal development, what germ cell layer gives rise to the cellular elements of the blood?
The mesoderm
During fetal development, what germ cell layer gives rise to the urogenital structures?
The mesoderm
During fetal development, what germ cell layer gives rise to the serous linings of body cavities, such as the peritoneal membranes?
The mesoderm
During fetal development, the kidney arises from what germ cell layer?
The mesoderm
During fetal development, the spleen arises from what germ cell layer?
The mesoderm, from the foregut mesentery
During fetal development, what germ cell layer gives rise to the gastrointestinal tract epithelium?
The endoderm
During fetal development, what germ cell layer gives rise to the lung epithelium?
The endoderm
During fetal development, what germ cell layer gives rise to the pancreas?
The endoderm
During fetal development, what germ cell layer gives rise to the thymus?
The endoderm
During fetal development, the follicular cells of the thyroid are derived from the _____, the parafollicular (C) cells are derived from the _____, and the cells of the parathyroid are derived from the _____.
endoderm; neural crest cells, endoderm
During fetal development, the notochord induces the formation of what other germ cell layer?
The neuroectoderm
What germ cell layer is the notochord derived from?
The mesoderm
What structure in the adult body is derived from the notochord?
The nucleus pulposus of the intervertebral disk
An infant is born with a truncus arteriosus malformation; what germ layer is normally responsible for the aorticopulmonary septum?
Neural crest cells
An infant is born with vertebral defects, anal atresia, and limb defects; what internal organ systems are you concerned about?
Cardiac, renal, and tracheoesophageal defects
(remember VACTERL: Vertebral defects, Anal atresia, Cardiac defects, Tracheo-Esophageal fistula, Renal defects, Limb defects)
What are common abnormalities seen in a neonate with defects in embryogenesis involving the mesodermal germ layer?
VACTERL: Vertebral defects, Anal atresia, Cardiac defects, Tracheo-Esophageal fistula, Renal defects, Limb defects
A 2-week-old embryo is exposed to a teratogen; what is the likely effect on development?
Before week 3 there is usually an all-or-none effect: either embryonal demise or no abnormalities
What embryonic process is occuring when the fetus is most susceptible to teratogens?
Organogenesis, between the 3rd and 8th weeks of pregnancy
A fetus is exposed to a teratogen after 8 weeks of pregnancy; will organogenesis be affected?
No; typically after 8 weeks, growth and function are affected but not organogenesis
What teratogen is the leading cause of mental retardation in children?
Alcohol
True or False: Alcohol can cause birth defects and mental retardation in children, and it produces fetal alcohol syndrome.
True
Angiotensin-converting enzyme inhibitors can lead to damage of what organ in the fetus?
The kidney
True or False: Maternal cocaine use can result in fetal addiction.
True
What placental pathology are cocaine-using mothers susceptible to?
Placental abruption
Exposure to diethylstilbestrol in utero leads to an increased incidence of what type of cancer?
Vaginal clear cell adenocarcinoma
A young woman is diagnosed with clear cell carcinoma of the vagina. This cancer is associated with exposure to what teratogen in utero?
Diethylstilbestrol
Name 2 teratogenic effects of iodine deficiency or excess in utero.
Congenital goitre or hypothyroidism
What birth defects might result if the acne treatment 13-cis-retinoic acid is taken during pregnancy?
Spontaneous abortions, cleft palate, cardiac abnormalities
What teratogen is known for causing limb defects that are known as “flipper” limbs?
Thalidomide; the defect is known as phocomelia
True or False: Tobacco use during pregnancy is associated with preterm labor.
True
True or False: Tobacco use during pregnancy has no effect on the placenta during development.
False; tobacco is associated with placental problems such as IUGR
True or False: Tobacco use during pregnancy is associated with attention-deficit/hyperactivity disorder in children.
True
Which is a better choice for a woman who needs anticoagulation during pregnancy: heparin or warfarin?
Heparin; warfarin use during pregnancy is associated with bone deformities, fetal hemorrhage, and abortion
True or False: X-rays can cause multiple anomalies in the offspring of women who are irradiated during pregnancy.
True
An infant is born with discolored teeth; what was the fetus exposed to in utero?
Tetracyclines
A woman undergoes chemotherapy with alkylating agents during her pregnancy; what fetal abnormalities are you concerned about?
Multiple anomalies, including absence of digits
What should you be sure to test for in an infant exposed to aminoglycosides in utero?
Deafness; aminoglycosides can cause CN VIII toxicity
What birth defect might result if the mother is taking valproic acid?
Valproic acid is a folate antagonist, which may cause neural tube defects
True or False: Infection and certain antibiotics during pregnancy can produce congenital malformations.
True
What is the leading cause of congenital malformations in the United States?
Fetal Alcohol SYndrome
True or False: Newborns of mothers who consumed significant amounts of alcohol during pregnancy have an increased incidence of congenital abnormalities.
True
What teratogen is commonly associated with microcephaly, facial abnormalities, limb dislocation, and heart and lung fistulas?
Fetal Alcohol Syndrome
True or False: Fetal alcohol syndrome is associated with an increased incidence of deafness.
False; fetal alcohol syndrome is associated with developmental retardation, microcephaly, holoprosencephaly, facial abnormalities, limb dislocations, and heart and lung fistulas
What is a possible mechanism of congenital malformation in fetal alcohol syndrome?
There may be an inhibition of cell migration
On what day of fetal development is the amnion formed?
Day 8
On what day of fetal development is the chorion formed?
Day 3
If twinning occurs before 3 days, what is the amniotic and chorionic status of the gestation?
The twins will be dichorionic and diamniotic
If twinning occurs between day 3 and day 8, what is the amniotic and chorionic status of the gestation?
The twins will be monochorionic and diamniotic
If twinning occurs after day 8, what is the amniotic and chorionic status of the gestation?
The twins will be monochorionic and monoamniotic
At which point is the risk greatest for conjoined twins: if twinning occurs before 3 days, between 3 and 8 days, or after 8 days?
After day 8 there is an increased risk for conjoined twins
How many chorions and amniotic sacs do conjoined twins have?
1 chorion and 1 amniotic sac
True or False: Twins who are born with two amniotic sacs but a single common chorion and placenta are always monozygotic twins.
True; one zygote split evenly and formed all of the structures listed
True or False: Twins who are born with two placentas (which may or may not be fused), separate chorions, and separate amniotic sacs are always dizygotic twins.
False; monozygotic twins may also form two placentas, two chorions, and two amniotic sacs
True or False: The placenta is the primary site of nutrient and gas exchange between mother and fetus.
True
The fetal component of the placenta consists of which two cell types?
Cytotrophoblast; syncytiotrophoblast
The cytotrophoblast composes what layer of the chorionic villi?
Inner
The syncytiotrophoblast composes what layer of the chorionic villi?
Outer
Which layer of the chorionic villi secretes human chorionic gonadotropin?
Outer layer (the syncytiotrophoblast)
What placental cell type secrete hCG?
Syncytiotrophoblast
Is the decidua basalis derived from the maternal or fetal component of the placenta?
Maternal
True or False: The decidua basalis is derived from the endometrium.
True
True or False: Blood from fetal capillaries in the branch villus is oxygenated directly by maternal capillaries.
False; the fetal branch villus is oxygenated by pooled maternal blood within lacunae of the decidua basalis
The umbilical cord contains how many umbilical arteries and umbilical veins?
Two arteries and one vein
Do the umbilical arteries carry oxygenated or deoxygenated blood?
Deoxygenated blood
The umbilical arteries return blood to the placenta via which fetal vessels?
The fetal internal iliac arteries
Does the umbilical vein carry oxygenated or deoxygenated blood?
Oxygenated blood
The _____ functions to remove nitrogenous waste from the fetal bladder.
urachus
True or False: A single umbilical artery is associated with congenital and chromosomal anomalies.
True
What connects the fetal bladder with the allantois?
The urachus
What fetal structure removes nitrogenous waste, like a urethra?
The urachus
From what fetal structure are the umbilical arteries and veins derived?
The allantois
What is the term for a fistula between the umbilicus and terminal ileum?
Vitelline fistula
What is the term for a fistula between the umbilicus and the bladder?
Urachal fistula
A ______ (vitelline/urachal) fistula results in fecal discharge.
vitelline
A ______ (vitelline/urachal) fistula results in urinary discharge.
urachal
In the embryonic heart, the truncus arteriosus gives rise to what two vessels?
Ascending aorta and pulmonary trunk
What embryonic structure gives rise to the ascending aorta?
The truncus arteriosus
What embryonic structure gives rise to the pulmonary trunk?
The truncus arteriosus
In the embryonic heart, the bulbus cordis gives rise to the _____ (smooth/trabeculated) part of ______ (right/left/both) ventricle(s).
Smooth; both
In the embryonic heart, the primitive ventricle gives rise to the _____ (smooth/trabeculated) part of ______ (right/left/both) ventricle(s).
Trabeculated; both
In the embryonic heart, the smooth part of the ventricles is derived from the ______, whereas the trabeculated part is derived from the _____.
Bulbus cordis; primitive ventricle
In the embryonic heart, the primitive atria give rise to the _____ (smooth/trabeculated) part of the ______ (right/left/both) atrium(a).
Trabeculated; both
In the embryonic heart, the left horn of the sinus venosus gives rise to what structure?
The coronary sinus
In the embryonic heart, the coronary sinus is derived from what structure?
The left horn of the sinus venosus
In the embryonic heart, the right horn of the sinus venosus gives rise to what structure?
The smooth part of the right atrium
In the embryonic heart, the smooth part of the right atrium is derived from what structure?
The right horn of the sinus venosus
In the embryonic heart, the trabeculated part of the right atrium is derived from the _____, and the smooth part of the right atrium is derived from the _____.
primitive atria; right horn of the sinus venosus
In the embryonic heart, the right common cardinal vein and the right anterior cardinal vein jointly give rise to what vein in the adult?
The superior vena cava
What is the opening called in the early muscular ventricular septum?
The interventricular foramen
_____ divides the truncus arteriosus into the aortic and pulmonary trunks.
The aorticopulmonary septum
The aorticopulmonary septum meets and fuses with the muscular ventricular septum to form the _____.
membranous interventricular septum
______ forms to close the interventricular foramen and separate the two ventricles.
The membranous interventricular septum
What two components make up the interventricular septum?
The muscular septum and the membranous septum
During development of the interatrial septum, the _____ narrows as the septum primum grows toward the endocardial cushion.
Foramen primum
During development of the interatrial septum, perforations in the septum primum form the ______ as the foramen primum disappears.
Foramen secundum
During development of the interatrial septum, the _____ maintains the right-to-left shunt as the septum secundum begins to grow.
Foramen secundum
What is the direction of the shunt maintained by the foramen secundum?
Right-to-left
During development of the interatrial septum, what is the name of the opening in the septum secundum that is patent throughout fetal life?
Foramen ovale
During development of the interatrial septum, as the ______ enlarges, the upper part of the septum primum degenerates.
Foramen secundum
Near the end of fetal heart development, the remaining portion of the septum primum is called the valve of the ______.
Foramen ovale
Near the end of fetal heart development, what composes the valve of the foramen ovale?
The remaining portion of the septum primum
What is a spinal neural tube defect where there is a tuft of hair present?
Spina bifida occulta
