A bank of of multiple choice Embryology questions
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A Bank of Embryology Questions 1. Concerning fertilization fertilization normally occurs shortly after the ovum enters the uterus sperm are able to fertilize a mature ovum immediately after they are deposited in the vagina immediately after release from the ovary, the ovum is surrounded by a zona pellucida that must be shed before a sperm can reach the ovum the mean time of birth is 38 weeks following fertilization none of the above 2. Concerning fertilization the mean time of birth is 40 weeks following fertilization fertilization normally occurs in the ampullary region of the uterine tube immediately after release from the ovary, the ovum is surrounded by a zona pellucida and a corona radiata, which is composed of cytotrophoblast if mixed with an ovum in vitro, the sperm in fresh ejaculate are competent to fertilize it the viability of an ovum is 4 hours or less 3. The average duration of gestation measured from the first day of the last normal menstrual period (LNMP) is 34 weeks 38 weeks 40 weeks 42 weeks Determined by adding nine months to the first day of the LNMP (i.e., if first day of LNMP was Oct.31, the baby is due on July 31) 4. Fertilization of an ovum by two sperm is the most common cause of ectopic pregnancy is more likely to occur if the sperms have not been capacitated is usually prevented by a change in the properties of the corona radiata soon after the first sperm enters the ovum is more likely to occur in the ampullary region of the uterine tube than in its isthmus increases in frequency with paternal age 5. Concerning fertilization fertilization normally occurs shortly after the ovum enters the uterus on average, fertilization occurs 14 - 15 days after the onset of the preceding menstrual period the mean duration of a pregnancy is 40 weeks from the day of fertilization immediately after release from the ovary, the ovum is surrounded by a zona pellucida that must be shed before a sperm can reach the ovum sperm are not able to fertilize an ovum until the ovum has been capacitated Page 1 6. Fertilization of an ovum by two sperm occurs most frequently if sperm reach the ovum more than 24 hours following ovulation increases in frequency with maternal age and tends to run in families is the second leading cause of monochorionic monoamnionic twins is usually prevented by a change in the properties of the zona pellucida is more likely to occur if an ovary releases two ova or if the right and left ovaries release ova simultaneously 7. Concerning fertilization immediately after release from the ovary, the ovum is surrounded by a zona pellucida and a corona radiata, which is composed of ovarian cells fertilization normally occurs in the ampullary region of the uterine tube the viability of an ovum is 24 hours or less if mixed with an ovum in vitro, the sperm in fresh ejaculate could not fertilize it all of the above 8. Implantation requires contact of embryoblast with uterine epithelium usually occurs on the 3rd day after fertilization cannot occur outside the uterus usually occurs when the embryo is in the 32-cell stage none of the above 9. The zona pellucida plays an important role in producing amniotic fluid the formation of the prochordal plate neural crest migration embryonic blood production preventing premature implantation 10. Implantation of the blastocyst cannot occur without prior differentiation of syncytiotrophoblast hatching from the zona pellucida fragmentation of the primary yolk sac development of amnioblast formation of the chorion 11. Implantation is preceded by an increase in ovarian hCG secretion usually occurs near the end of the first week following fertilization requires contact of the zona pellucida with uterine epithelium cannot occur outside the uterus and uterine tubes leads to the development of the inner cell mass Page 2 12. Syncytiotrophoblast secretes chorionic gonadotropin gives rise to the decidua basalis begins to develop on the 4th day postfertilization is derived from the zona pellucida degenerates once cytotrophoblast takes over its function 13. Normal implantation occurs at a site that will later form the decidua parietalis requires contact of amnioblast with uterine epithelium is associated with the onset of human chorionic gonadotropin production usually occurs on or about the 9th day after fertilization usually occurs when the embryo is at the early primitive streak stage 14. Concerning the first week of development implantation usually occurs 12 - 24 hours after the morula enters the uterus implantation occurs by means of adherence of the zona pellucida to the uterine epithelium at the time of implantation, the embryo has reached the blastocyst stage the morula forms within the uterine tube and enters the uterine lumen on the 5th day postfertilization all of the above 15. Somites are the source of cells in the nucleus pulposus give rise to cardiac muscle give rise to the cartilages of the branchial arches are derived from the paraxial mesoderm none of the above 16. Cells in somites give rise to all nuclei pulposi of the abdominal diaphragm bones of the skull paravertebral ganglia skeletal muscles of the trunk 17. Concerning dermomyotomes they are the source of cells for the nucleus pulposus of intervertebral discs they are derived from cells migrating out of the primitive node they are the source of cells for the mandible the are the source of cells for the sternohyoid all of the above Page 3 18. Concerning somites they give rise to the nucleus pulposi of intervertebral discs they give rise to the dorsal root and autonomic ganglia failure to form in the sacrococcygeal region leads to the condition known as spinal dermal sinus they give rise to all the striated muscles of the trunk they form as a result of segmentation of the lateral plate mesoderm 19. Cells in somites give rise to dorsal root ganglia the mandible vertebrae cardiac muscle none of the above 20. Cells in somites give rise to dorsal root ganglia sympathetic ganglia the mandible the liver ribs 21. Concerning the primitive streak it is the source of striated muscle cells of the abdominal wall it consists primarily of proliferating hypoblast it is the source of most of the body's epidermis it is induced to form by the underlying notochord it is the source of most of the cells in the neural tube 22. The abdominal diaphragm is derived partly from the pleuropericardial membranes is derived entirely from mesoderm is derived partly from the caudal portion of the septum transversum is derived partly from the 3rd-5th cervical epaxial dermomyotomes all of the above 23. The primitive streak is derived from epiblast first appears in the roof of the amniotic cavity gives rise to ectomesenchyme of the 1st branchial arch gives rise to the allantois none of the above Page 4 24. Concerning the primitive streak it consists solely of proliferating epiblast it is the source of the body's epidermis its failure to form leads to anencephaly its first appearance coincides with the initiation of implantation it is induced to form by the underlying notochord 25. Which of the following events is most closely associated with the fourth week of development (postfertilization) commencement of blood circulation mesoderm formation obliteration of uterine cavity by the expanding chorion commencement of hCG (human chorionic gonadotropin) secretion neural tube closure 26. The septum transversum gives rise to a part of the abdominal diaphragm gives rise to the lesser omentum and falciform ligament gives rise to the capsule and connective tissue of the liver is derived from mesodermal cells lying cranial to the pericardial portion of the coelom prior to embryonic folding all of the above 27. Concerning development of the lungs the fetal lungs become capable of functioning between the 24th and 28th weeks of pregnancy, as measured from the last normal menstrual period the major determinant of whether or not the fetal lungs can sustain life outside the womb is the completion of pulmonary autonomic innervation the laryngotracheal diverticulum is an outpocketing of the stomodeum the laryngotracheal diverticulum joins the lung buds, which arise from the mesoderm dorsal to the heart tubes none of the above 28. Concerning the primitive streak it is the source of most of the cells in autonomic ganglia it appears just prior to implantation it is derived from proliferating trophoblast it is the source of most of the cells in the neural tube none of the above Page 5 29. The primitive node (Hensen's node) is the chief source of cells for somites sclerotomes paraxial mesoderm lateral plate mesoderm none of the above 30. The abdominal diaphragm is comprised of contributions from the caudal portion of the septum transversum hypaxial dermomyotomes C3 - C5 pleuropericardial membranes ventral mesentery of the esophagus all of the above 31. Concerning the umbilical cord it is surrounded by the fluid of the extraembryonic coelom its outer layer is skin Ladd's bands may be produced when it tears it provides room for development of most of the small intestine its outer layer is chorion 32. The outer layer of the umbilical cord is continuous with, and similar in structure to the chorionic membrane amniotic membrane syncytiotrophoblast cytotrophoblast allantoic diverticulum 33. Concerning fetal membranes the amnion usually remains separated from the chorion by the extraembryonic coelom until shortly before delivery the chorion is composed of syncytiotrophoblast lined by extraembryonic mesoderm the chorion is avascular the amniotic fluid is the recipient of shed fetal skin cells and fetal urine all of the above 34. Concerning the chorion the villous chorion has the same DNA as the fetus, not the mother it is composed of trophoblast lined by connective tissue derived from extraembryonic mesoderm the chorionic cavity is ultimately obliterated the chorionic cavity is derived from the extraembryonic coelom all of the above Page 6 35. Concerning fetal membranes all fraternal and most identical twins have separate chorions the amniotic cavity is the recipient of shed fetal intestinal epithelial cells chorionic cells have the DNA complement of the fetus, not the mother the amnion usually remains separated from the chorion by the extraembryonic coelom until shortly before delivery the chorion forms the outer layer of the umbilical cord 36. Concerning the placenta it is fed by fetal arteries that travel along the secondary yolk sac it is derived primarily from amnioblast and allantois it is comprised of villous chorion and decidua basalis it begins to secrete chorionic gonadotropin at the end of the first month all of the above 37. Concerning fetal membranes the cavity surrounded by the chorion is ultimately obliterated the amnion forms the outer layer of the umbilical cord the chorion is composed of trophoblast lined by connective tissue derived from extraembryonic mesoderm the amnion is not a major source of gonadotropins all of the above 38. Dizygotic twins are never conjoined have separate chorions and amnions occur at a frequency that is genetically influenced are approximately twice as common as monozygotic twins all of the above 39. Concerning twins dizygotic twins share, on average, 25% more genes in common that do the average pair of siblings the likelihood of having monochorionic diamnionic twins is partly determined by maternal genotype mortality of dichorionic diamnionic twins is approximately twice that of monochorionic monoamnionic twins all of the above none of the above Page 7 40. Concerning twins the likelihood of having either fraternal (dizygotic) or identical (monozygotic) twins is significantly influenced by age of the mother dizygotic twins never share a common amnion monozygotic twins never share a common placenta dizygotic twins share 25% more genes in common than do the average pair of siblings none of the above 41. Concerning twins the likelihood of having identical twins is significantly influenced by genetic factors in the mother fraternal twins most often share a single amnion identical twins usually arise by splitting of the morula live births of identical twins and fraternal twins are almost equally common none of the above 42. Monozygotic twins sometimes have a shared chorion occur when two sperm fertilize a single ovum have separate placentae less than 5% of the time usually occur by formation of two morulae none of the above 43. Concerning twins the tendency to have fraternal (dizygotic) is independent of maternal genotype monozygotic twins usually share a common placenta dizygotic twins share 25% more genes in common than do the average pair of siblings the likelihood of having identical (monozygotic) twins is significantly influenced by age of the mother dizygotic twins usually share a common amnion 44. Concerning twins live births of identical twins and fraternal twins are almost equally common identical twins usually arise by formation of two inner cell masses (embryoblast clumps) fraternal twins most often share a single amnion the likelihood of having identical twins is significantly influenced by genetic factors in the mother all of the above 45. Concerning twins monozygotic twins never share a common placenta dizygotic twins share 25% more genes in common than do the average pair of siblings the likelihood of having identical twins is significantly influenced by age of the mother dizygotic twins never share a common amnion all of the above Page 8 46. Concerning conjoined twins they must be of the same sex they share a common amnion but have separate chorions they arise from the incomplete splitting of the morula they increase in frequency with the age of the mother all of the above 47. Concerning twin-twin transfusion syndrome it may occur in the most common type of identical twins but not in dizygotic twins the recipient of the "transfusion" is polyhydramniotic and prone to suffer cardiac problems the donor of the "transfusion" is oligohydramniotic and undersized all of the above none of the above 48. Concerning twin-twin transfusion syndrome the recipient of the "transfusion" is oligohydramniotic it is the result of a placental arteriovenous anastomosis the donor of the "transfusion" is prone to develop heart failure the recipient of the "transfusion" is oliguric occurs with equal frequency in fraternal and identical twins 49. Conjoined twins joined at the head may have separate fathers placentae amnions chorions umbilical cords 50. In which kind of twin is twin-twin transfusion syndrome the greatest threat to proper development Monochorionic monoamnionic Dichorionic monoamnionic Dichorionic diamnionic monozygotic Dichorionic diamnionic dizygotic Monochorionic diamnionic 51. The intraembryonic coelom it is lined by endoderm normally contains only fluid becomes the pleural and peritoneal, but not the pericardial, cavities all of the above none of the above Page 9 52. The intraembryonic coelom is formed just prior to the primitive steak is lined by specialized ectoderm is connected to the amniotic cavity via the umbilical cord is the precursor of the subarachnoid space none of the above 53. The intraembryonic coelom is the progenitor of the cavity of the heart tube degenerates during the tenth week of development is derived initially from the blastocyst cavity is lined by an epithelium derived from mesoderm normally does not communicate with the extraembryonic coelom 54. Concerning the intraembryonic coelom it is lined by specialized endoderm the thoracic portion becomes divided into pleural and pericardial cavities the abdominal portion becomes incorporated into the lumen of the midgut it is sealed off from the extraembryonic coelom during the fourth week of development all of the above 55. The intraembryonic coelom is lined by a layer of cells derived from cuboidal hypoblast is sealed off from the extraembryonic coelom during the 5th week of development initially contains only fluid, but later is a repository of meconium all of the above none of the above 56. Complete failure of the pleuroperitoneal membrane to form on the left side is caused by failure of cell migration from the left C3-C5 hypaxial dermomyotomes results in a omphalocele is of little immediate threat to survival of the newborn all of the above none of the above 57. A possible consequence of Bochdalek hernia esophageal atresia inflammation of the small intestine pleuropericardial fistula pulmonary hypoplasia none of the above Page 10 58. From the structures listed below, pick the one whose absence will most likely lead to birth of a full term neonate with pulmonary hypoplasia interatrial septum pleuropericardial membrane interventricular septum amniochorionic membrane pleuroperitoneal membrane 59. Failure of the pleuroperitoneal membrane to form on the left side is most likely to result in the newborn facing the following problem obstructed small intestine paralysis and anesthesia below the C5 spinal segment difficulty oxygenating its blood left ventricular hypoplasia none of the above 60. Concerning the intraembryonic coelom it is the chief source of amniotic fluid improper development of the pleuroperitoneal membranes may lead to congenital umbilical hernia improper development of the pleuropericardial membranes may lead to poorly oxygenated fetal blood it persists as a set of fluid-filled spaces even into postnatal life none of the above 61. Concerning partitioning of the coelomic cavity failure of the pleuroperitoneal fold to form on the left is associated with underdeveloped lungs failure of the pleuropericardial fold to form on the left is associated with Bochdalek hernia open communication of the pleural and peritoneal cavities will occur if myotome cells from the 3rd-5th cervical somites fail to enter the septum transversum failure of the pleuroperitoneal fold to form on the right is associated with right ventricular hypoplasia all of the above 62. Concerning the intraembryonic coelom it is the chief source of amniotic fluid it is largely obliterated during the later stages of fetal development improper development of the pleuropericardial membranes is usually asymptomatic improper development of the pleuroperitoneal membranes may lead to congenital umbilical hernia none of the above Page 11 63. Failure of the pleuroperitoneal membrane to form on the left side is most likely to result in the newborn having respiratory problems pericarditis an umbilical hernia a lumbocostal trigone an inflamed small intestine 64. Concerning the intraembryonic coelom improper development of the pleuroperitoneal membranes may ultimately be fatal it is sealed off from the extraembryonic coelom during the fourth week of development it is incorporated into the central canal of the spinal cord improper development of the pleuropericardial membranes may lead to tracheo-esophageal fistula none of the above 65. Concerning amniotic fluid (poly)hydramnios is defined as 120% the amount of amniotic fluid as is normal for a particular developmental stage esophageal atresia is a cause of diminished amniotic fluid anencephaly is a cause of diminished amniotic fluid renal agenesis is a cause of excess amniotic fluid none of the above 66. Which of the following is associated with oligohydramnios tracheo-esophageal fistula renal agenesis myelomeningocele anencephaly loose joints 67. Which of the following may be associated with polyhydramnios (i.e., may cause polyhydramnios or may result from it) duodenal atresia anencephaly proximal jejunal atresia esophageal atresia all of the above Page 12 68. Concerning amniotic fluid failure of fetal kidneys to develop is one possible cause for an increase in amniotic fluid volume too much amniotic fluid interferes with proper joint development failure of the fetus to absorb swallowed amniotic fluid is one factor that might cause its volume to decline too little amniotic fluid interferes with proper lung development too much amniotic fluid causes pressure on the umbilical cord that can lead to fetal death 69. Concerning amniotic fluid anencephaly is a cause of diminished amniotic fluid renal agenesis is a cause of excess amniotic fluid esophageal atresia is a cause of excess amniotic fluid oligohydramnios is defined as twice the amount of amniotic fluid as is normal for a particular developmental stage all of the above 70. Amniotic fluid volume can be expected to rise above normal if the fetus has esophageal atresia has a Bochdalek hernia has renal agenesis has Hirschsprung's disease has open myelomeningocele 71. Concerning amniotic fluid it normally contacts the bowel during the period of physiologic umbilical herniation (poly)hydramnios may cause improper development of the neural tube, particularly in the cranial region from the second trimester on, fetal urine no longer contributes significantly to amniotic fluid volume volume is increased in cases where a developmental defect interferes with fetal swallowing oligohydramnios is one of the sequelae of esophageal atresia 72. Which of the following may be associated with oligohydramnios (i.e., may cause oligohydramnios or may result from it) fused femur and tibia pulmonary hypoplasia renal agenesis umbilical artery occlusion all of the above Page 13 73. Concerning neural folds they are induced to form by the cytotrophoblast they form during the 2nd week of development they give rise only to that part of the CNS caudal to the myelospinal boundary their fusion occurs during the 4th week of development from their crests come cells that give rise to somatic motor neurons 74. Neural crest gives rise to most of the cardiogenic mesoderm is derived from the primitive streak becomes smooth muscle cells within the wall of the bowel induces development of syncytiotrophoblast is the source of most of the mesenchyme of the head 75. Concerning neural folds they form during the 3rd week of development they join to form a tube that give rise to the brain and spinal cord they are induced to form by the underlying notochord from their crests come cells that give rise to dorsal root ganglia all of the above 76. Which of the following structures are derived from the neural crest somatic motor neurons sclerotomes preganglionic sympathetic neurons cells of the adrenal cortex none of the above 77. Concerning neural folds they are induced to form by the prochordal plate they begin to form during the 3rd week of postfertilization development from their crests come cells that give rise to somatic motor neurons all of the above none of the above 78. Concerning spinal dysraphisms the most serious spinal dysraphisms are associated with polyhydramnios if it were not for the possibility of rupture (and for cosmetic reasons), there would be no need to remove meningoceles myelomeningocele (in clinical terminology) is usually not harmful if it occurs superior to the intergluteal fold myelocystocele involves the medulla of the brain and the cervical spinal cord a spinal dermal sinus is usually not harmful if it occurs in the intergluteal fold Page 14 79. Open myelomeningocele (in clinical terminology) is the spinal cord's equivalent of encephalocystocele is one of the major fetal causes of polyhydramnios is the only spinal dysraphism associated with release of alpha-fetoprotein into amniotic fluid is usually not harmful if it occurs superior to the intergluteal fold arises from a failure of neural crest cells to differentiate into dorsal portions of vertebral arches 80. Maternal serum alpha-fetoprotein increases if the fetus has oligohydramnios Bochdalek hernia Ladd's bands anencephaly meningocele 81. ated maternal serum alpha-fetoprotein is a possible indicator of renal agenesis patent ductus arteriosus anencephaly all of the above none of the above 82. Myelomeningocele (using clinical terminology) is most common at the tip of the coccyx leaves the affected individual with paralyzed upper limbs but able to walk is caused by a failure of the neural folds to meet and fuse is undetectable by the results of amniocentesis all of the above 83. The most common type of neural tube defect arises from an abnormality most likely occurring during days 10 - 19, measured from time of fertilization days 1- 9, measured from time of fertilization weeks 22 - 26, measured from first day of last normal menstrual period weeks 7 - 10, measured from first day of last normal menstrual period days 22 - 29, measured from time of fertilization 84. Concerning meningocele the fundamental problem is an error in neural crest migration it is accompanied by a defect in vertebral arch formation it is associated with muscle weakness or paralysis at birth all of the above none of the above Page 15 85. Open myelomeningocele (in clinical terminology) is the only spinal dysraphism associated with release of alpha-fetoprotein into amniotic fluid is the spinal cord's equivalent of what in the brain is called Arnold-Chiari malformation is a form of spina bifida occulta is less often associated with neonatal paraplegia (paralyzed lower limbs) than is myelocystocele arises when the roof of the neural tube herniates dorsally through the space between vertebral arches 86. Concerning anomalies of neural tube development most often meningocele is accompanied by elevated levels of maternal serum alpha-fetoprotein meningomyelocele (clinical terminology) is associated with motor and sensory deficits in body segments caudal to the defect anencephaly is the head's equivalent of myelocystocele spina bifida occulta is usually revealed by the development of minor neurological defects as the child reaches puberty all of the above 87. Concerning early heart development the cardiogenic mesoderm is derived from the mesenchyme within the septum transversum the primitive heart does not begin to pump blood until the internal nerve conducting system develops the muscular wall of the heart (myocardium) is derived from the extraembryonic mesoderm although two endocardial heart tubes develop, only one contributes to heart development the primitive heart is initially a long tube and the direction of blood flow is caudal to cranial 88. Early heart development begins within the extraembryonic mesoderm begins in the sixth week of embryonic life begins caudal to the prochordal plate is not completed until the third trimester begins ventral to the developing pericardial cavity prior to embryonic folding and bending 89. Concerning early heart development the cardiogenic mesoderm is initially located cranial to the future oropharyngeal membrane the cardiogenic mesoderm is derived from the primitive pit the right and left sides of the heart are derived from the right and left endocardial heart tubes, respectively the developing heart comes into a close relationship with the future pericardium only after embryonic folding development begins in the second week of embryonic life Page 16 90. Concerning early heart development prior to embryonic folding the developing heart is ventral to the future pericardial cavity although two endocardial heart tubes develop, only one contributes to heart development the primitive heart does not begin to pump blood until the internal nerve conducting system develops the cardiogenic mesoderm is derived from the mesenchyme within the septum transversum the muscular wall of the heart (myocardium) is derived from the splanchnic mesoderm of the pericardium 91. Concerning early heart development it starts in an area cranial to the oropharyngeal membrane the cardiogenic mesoderm is derived from the primitive pit it is not completed until the third trimester the endocardial heart tubes give rise to the muscular wall of the heart it begins in the mesoderm dorsal to the future pericardial cavity prior to embryonic folding 92. Concerning the primitive heart chambers the primitive atrium mainly contributes to the adult left atrium the bulbus cordis will eventually be divided to form the beginning parts of the arch of the aorta and pulmonary trunk the primitive ventricle will become the aortic vestibule of the adult left ventricle the only adult remnant of the sinus venosus is the coronary sinus the truncus arteriosus is divided by the formation of the spiral septum 93. Concerning the primitive heart chambers the adult right ventricle is derived mainly from the primitive ventricle the adult left atrium is largely derived from the sinus venosus the bulbus cordis will contribute to both the conus arteriosus and aortic vestibule the primitive atrium mainly contributes to the adult left atrium none of the above 94. Which one of the follow statements concerning development of the heart is FALSE cardiac development begins in the intraembryonic mesoderm anterior to the prochordal plate during the 3rd week of development the bulboventricular loop bends toward the left producing the leftward position of the ventricles in adult heart anatomy failure of the truncal ridges to spiral results in transposition of the great vessels the sinus venarum is the smooth walled part of the right atrium derived from the sinus venosus the foramen primum is normally obliterated during embryonic development Page 17 95. Concerning development of the heart closure of the foramen ovale after birth is accomplished by fusion of the septum secundum to the endocardial cushions the interatrial septum is formed by fusion of the septum primum and septum secundum the only remnant of the primitive atrium in the adult is the auricle of the left atrium the adult left ventricle is derived entirely from the primitive embryonic ventricle the embryonic bulbus cordis gives rise to the ascending aorta in the adult 96. Concerning the division of the heart chambers: the septum secundum becomes the membranous part of the adult interventricular septum the primitive interventricular septum of the embryo has no adult derivative the endocardial cushions contribute to the division of the atrioventricular canal and ventricles the septum primum is involved in dividing the atrioventricular canal all of the above 97. Concerning development of the atria the auricles of the adult right and left atria are both derived from the primitive embryonic atrium the embryonic atrium is separated into two chambers by the development of an interatrial septum derived from the sinus venosus the embryonic atrium becomes the adult right atrium, and the sinus venosus is the principle source for the adult left atrium most blood entering the left atrium flows into the right atrium up until the time of birth none of the above 98. Concerning development of the ventricles the interventricular septum is derived from the embryonic septum secundum the embryonic bulbus cordis contributes to both the right and left adult ventricles the embryonic sinus venosus forms the membranous part of the interventricular septum the embryonic bulboventricular loop normally bends to the left explaining why the heart is on the left side of the body the primitive ventricle is the last embryonic heart chamber to form 99. The right atrium is separated from the left atrium by growth of the endocardial cushions has a smooth walled portion derived from the sinus venosus receives deoxygenated blood from the inferior vena cava in fetal circulation drains its blood into the bulbus cordis through the foramen ovale is derived from the cranial end of the right endocardial heart tube Page 18 100. The left ventricle is separated from the right ventricle by growth of the septum spurium pumps deoxygenated blood out the aorta in fetal circulation has rough inner walls composed of pectinate muscles begins early development outside of the pericardial cavity is derived from the primitive ventricle and left wall of the bulbus cordis 101. Concerning development of the ventricles the embryonic bulboventricular loop normally bends to the left explaining why the heart is on the left side of the body the embryonic bulbus cordis contributes to both the right and left adult ventricles the primitive ventricle is the last embryonic heart chamber to form the wall between the right and left ventricles is derived from the septum secundum none of the above 102. Concerning development of the atria while the adult right atrium is derived from the embryonic atrium, the adult left atrium is mostly derived from the sinus venosus the foramen secundum is normally obliterated by fusion of the septum secundum to the endocardial cushions closure of the foramen ovale after birth is accomplished by fusion of the septum secundum to the septum primum the embryonic atrium is separated into two chambers by the development of an interatrial septum derived from the endocardial cushions the smooth walled portions of the adult right and left atria represent the main adult remnants of the embryonic atrium 103. Concerning development of the atria the foramen primum is normally obliterated by fusion of the septum primum to the endocardial cushions the embryonic atrium becomes the adult right atrium, and the sinus venosus is the principle source for the adult left atrium the inferior margin of the septum secundum forms an opening between the right and left fetal atria called the foramen secundum the auricles of the adult right and left atria represent the main adult remnants of the bulbus cordis the embryonic atrium is separated into two chambers by the development of an interatrial septum derived from the endocardial cushions 104. Concerning development of the ventricles the embryonic bulboventricular loop normally bends to the right the conus arteriosus (also called infundibulum) is the outflow track of the left ventricle the primitive ventricle first appears within the septum transversum, but soon moves into the pericardial cavity the embryonic bulbus cordis becomes the adult left ventricle the division of the right and left ventricles is completed by the fusion of the septum primum and septum secundum Page 19 105. Concerning cardiac malformations since cardiac function is so critical to survival, cardiac malformations are rarely seen in live births probe patent foramen ovale is the most common cause of blue babies (i.e., poor oxygenation of circulating arterial blood) ventricular septal defects most commonly occur in the membranous portion of the septum atrial septal defects are usually the result of the failure of the truncal ridges to develop in a spiral fashion none of the above 106. Tetralogy of Fallot consists of: transposition of the great vessels, atrial septal defect, right ventricular hypertrophy, and mitral valve defects pulmonary stenosis, atrial septal defect, persistent truncus arteriosus, and left ventricular hypertrophy mitral valve defects, pulmonary stenosis, right ventricular hypertrophy, and overriding aorta ventricular septal defect, left ventricular hypertrophy, overriding aorta, and persistent ductus arteriosus pulmonary stenosis, ventricular septal defect, overriding aorta, and right ventricular hypertrophy 107. Concerning cardiac malformations ventricular septal defects most commonly occur in the membranous portion of the septum Tetralogy of Fallot includes aortic stenosis, right ventricular hypertrophy, interventricular septal defect, and patent ductus arteriosus since cardiac function is so critical to survival, cardiac malformations are rarely seen in live births all of the above none of the above 108. The most common type of cardiac defect is: tetralogy of Fallot membranous type ventricular septal defect secundum type atrial septal defect (i.e., the foramen secundum is too large) atrioventricular septal defect muscular type ventricular septal defect 109. Concerning cardiac malformations ventricular septal defects most commonly occur in the membranous portion of the septum since cardiac function is so critical to survival, cardiac malformations are rarely seen in live births atrial septal defects are usually the result of the failure of the truncal ridges to develop in a spiral fashion probe patent foramen ovale is the most common cause of blue babies (i.e., poor oxygenation of circulating arterial blood) Tetralogy of Fallot is failure to develop of the septum primum, septum secundum, foramen primum and foramen secundum Page 20 110. Concerning cardiac malformations ventricular septal defects usually occur in the muscular portion of the septum postductal coarctation of the aorta can lead to a weak femoral pulse and hypertrophied intercostal arteries even very small atrial septal defects are typically fatal in newborns because the heart is so critical to survival, live births with cardiac malformations are very rare Tetralogy of Fallot refers to disruption in the development of the atrioventricular septum 111. Concerning cardiac malformations: transposition of the great arteries is usually the result of the failure of the truncal ridges to develop in a spiral fashion ventricular septal defects are the most frequently occurring cardiac malformations ventricular septal defects most commonly occur in the membranous portion of the interventricular septum Tetralogy of Fallot includes pulmonary stenosis, ventricular septal defect, overriding aorta, and hypertrophy of the right ventricle all of the above 112. Concerning cardiac malformations Tetralogy of Fallot is failure to develop of the septum primum, septum secundum, foramen primum and foramen secundum ventricular septal defects most commonly occur in the muscular portion of the septum atrioventricularis communis is frequently associated with Downs syndrome probe patent foramen ovale is the most common cause of blue babies (i.e., poor oxygenation of circulating arterial blood) none of the above 113. Tetralogy of Fallot is a set of cardiac defects stemming from an unequal division of the truncus arteriosus. The set of defects are: pulmonary stenosis, left ventricular hypertrophy, interatrial septal defect, and overriding aorta aortic stenosis, right ventricular hypertrophy, interventricular septal defect, and patent ductus arteriosus pulmonary stenosis, right ventricular hypertrophy, interventricular septal defect, and overriding aorta aortic stenosis, left ventricular hypertrophy, interventricular septal defect, overriding aorta pulmonary stenosis, interatrial septal defect, patent ductus arteriosus, and overriding pulmonary trunk 114. The aortic arch in the adult is derived from: a combination of portions of the truncus arteriosus, aortic sac and embryonic left fourth aortic arch a combination of portions of the left dorsal aorta and left seventh intersegmental artery a combination of portions of the first, second and third embryonic aortic arches on the left side a combination of portions of the truncus arteriosus, aortic sac and embryonic left sixth aortic arch the embryonic left third aortic arch Page 21 115. The aortic arch in the adult is derived from a combination of portions of the left dorsal aorta and left seventh intersegmental artery a combination of portions of the first, second and third embryonic aortic arches on the left side a combination of portions of the embryonic fifth and sixth aortic arches on the left side a combination of portions of the truncus arteriosus, aortic sac and embryonic left fourth aortic arch the embryonic left dorsal aorta 116. Concerning the embryonic aortic arches the fourth pair disappear during the course of development the left third embryonic aortic arch forms the ascending and horizontal portion of the adult aortic arch the first pair will become the adult common carotid arteries the subclavian arteries are largely derived from the fifth pair of embryonic aortic arches the sixth pair will contribute to the formation of the pulmonary arteries 117. Concerning adult derivatives of embryonic vessels the embryonic umbilical artery has no adult derivative the embryonic ductus venosus gives rise to the adult ductus venosus the embryonic truncus arteriosus contributes to both the ascending aorta and pulmonary trunk the embryonic ductus arteriosus gives rise to the adult brachiocephalic artery all of the above 118. Concerning adult derivatives of embryonic vessels the embryonic umbilical artery has no adult derivative the embryonic ductus venosus is incorporated into the adult right atrium the embryonic umbilical vein gives rise to the adult ligamentum venosum the embryonic truncus arteriosus contributes to both the ascending aorta and pulmonary trunk none of the above 119. The embryonic aortic arches connect the developing heart to the developing circulatory system. the fourth pair of embryonic aortic arches disappear during the course of development the first pair of embryonic aortic arches will become the adult common carotids the sixth pair of embryonic aortic arches will contribute to the formation of the pulmonary arteries the left third embryonic aortic arch forms the ascending and horizontal portion of the adult aortic arch the subclavian arteries are largely derived from the fifth pair of embryonic aortic arches Page 22 120. The embryonic aortic arches connect the developing heart to the developing circulatory system. the left third embryonic aortic arch forms the ascending and horizontal portion of the adult aortic arch the subclavian arteries are largely derived from the fifth pair of embryonic aortic arches the sixth pair of embryonic aortic arches will contribute to the formation of the pulmonary arteries the first pair of embryonic aortic arches will become the adult common carotids the fourth pair of embryonic aortic arches disappear during the course of development 121. Concerning the embryonic aortic arches the sixth aortic arches contribute to the pulmonary arteries the right and left third arches give rise to the right and left common carotid arteries the left fourth arch gives rise to that segment of the aortic arch just distal to the origin of the left common carotid artery the right fourth arch give rise to that segment of the right subclavian artery just distal to the origin of the right common carotid artery from the brachiocephalic trunk all of the above 122. Concerning the adult derivatives of embryonic and fetal vessels the ductus arteriosus gives rise to the adult ligamentum teres the umbilical artery gives rise to the adult ligamentum venosum the ductus venosus gives rise to the adult sinus venosus the truncus arteriosus contributes to both the ascending aorta and pulmonary trunk all of the above 123. Concerning the adult derivatives of embryonic and fetal vessels the umbilical artery gives rise to the adult ligamentum venosum the ductus venosus gives rise to the adult sinus venosus the truncus arteriosus contributes to both the ascending aorta and pulmonary trunk all of the above none of the above 124. Concerning the levels of oxygenation in the blood of fetal vessels oxygenation of blood in the right ventricle is higher than that in the left ventricle oxygenation of blood in the ascending aorta is higher than that in the descending aorta oxygenation of blood in the ductus arteriosus is equal to that in the ductus venosus oxygenation of blood in the right atrium is higher than that in the left atrium oxygenation of blood entering the heart from the superior vena cava is higher than that of blood entering from the inferior vena cava Page 23 125. Concerning fetal circulation the blood in the right ventricle has a higher oxygen content than that in the left ventricle the umbilical arteries carry oxygenated blood from the placenta back to the heart the ductus arteriosus allows most of the blood from the placenta to bypass the celiac and superior mesenteric arteries the ductus venosus allows most of the blood from the right ventricle to bypass the lungs most of the blood entering the left atrium comes through the foramen ovale 126. Concerning the levels of oxygenation in the blood of fetal vessels oxygenation of blood entering the heart from the inferior vena cava is higher than that of blood entering from the superior vena cava oxygenation of blood in the ascending aorta is higher than that in the descending aorta oxygenation of blood in the left ventricle is higher than that in the right ventricle oxygenation of blood in the left atrium is higher than that in the right atrium all of the above 127. Concerning fetal circulation the direction of blood flow through the fetal heart is the opposite of that of the adult heart the blood from the superior vena cava mostly passes through the foramen ovale into the left atrium the ductus arteriosus allows most of the blood from the placenta to bypass the celiac and superior mesenteric arteries the umbilical vein carries oxygenated blood from the placenta back to the heart the ductus venosus allows most of the blood from the right ventricle to bypass the lungs 128. Concerning fetal circulation the ductus venosus allows most of the blood from the right ventricle to bypass the lungs the umbilical arteries carry oxygenated blood from the placenta back to the heart the direction of blood flow through the fetal heart is the opposite of that of the adult heart the ductus arteriosus allows most of the blood from the placenta to bypass the celiac and superior mesenteric arteries the blood from the inferior vena cava mostly passes through the foramen ovale into the left atrium 129. The following structures are secondarily retroperitoneal inferior mesenteric vein celiac ganglion inferior vena cava kidney none of the above Page 24 130. One of the reasons most of the pancreatic secretory volume normally enters the duodenum at the same site as does bile is the uncinate process of the pancreas is derived from the ventral pancreas the dorsal pancreas and liver arise from a common diverticulum the final stage of normal pancreatic development results in migration of the common bile duct opening onto the dorsal surface of the duodenum the duct of the ventral pancreas establishes a connection with the duct of the dorsal pancreas the entire second part of the duodenum is derived from the foregut 131. Concerning development of the mesenteries the greater omentum is a derived from a fusion of the dorsal mesenteries of the midgut and hindgut the dorsal mesogastrium is largely lost when the pancreas becomes secondarily retroperitoneal the mesentery of the small intestine is the only portion of the dorsal mesentery to retain its embryonic midline attachment the ventral mesentery of the stomach persists as the hepatogastric and hepatoduodenal ligaments none of the above 132. Concerning the midgut from its dorsal surface arises the dorsal pancreatic diverticulum its connection to the allantois may persist as a Meckel's diverticulum most of the bowel derived from it becomes secondarily retroperitoneal its derivatives receive arterial blood through branches of the superior mesenteric artery none of the above 133. Concerning development of the pancreas the accessory pancreatic duct is a vestige of the duct of the ventral pancreas the dorsal pancreatic diverticulum is an outgrowth of the same structure that will give rise to the liver and gall bladder its secretory cells are derived from the endoderm of the foregut annular pancreas is the symptomatic version of pancreatic divisum its body is primarily retroperitoneal whereas its head is secondarily retroperitoneal 134. The dorsal mesogastrium contributes to the greater omentum is invaded by the dorsal pancreatic diverticulum maintains its original midline root even in the adult passes the umbilical vein between its layers all of the above Page 25 135. Concerning development of the gut the superior mesenteric artery supplies structures derived from the mid- and hindguts the dorsal pancreatic diverticulum is an outgrowth of the midgut the celiac artery supplies structures derived from the foregut the hepatopancreatic diverticulum is an outgrowth of the midgut all of the above 136. Concerning development of the liver the stem of the hepatopancreatic diverticulum becomes the common bile duct the liver develops a bare area as a result of the pancreas becoming secondarily retroperitoneal the hepatic part of the hepatopancreatic diverticulum grows into the mesogastrium the hepatopancreatic diverticulum is most often an outpocketing of the midgut wall the liver arises from the same diverticulum as the body and tail of the pancreas 137. Concerning development of the mesenteries the lower mesogastrium gives rise to the gastrocolic ligament the mesentery ventral to the developing liver is resorbed, leaving no adult derivative the sigmoid mesocolon is the only part of the dorsal mesentery to retain its original embryonic root the pancreas is a primarily retroperitoneal structure whose tail becomes secondarily mesenteric the connection between the lesser sac and greater sac becomes restricted to the epiploic foramen as a result of the spleen developing within the upper mesogastrium 138. Concerning development of the liver the visceral peritoneum on the cranial surface of the developing liver fuses to the parietal peritoneum on the caudal surface of the diaphragm to create the coronary ligament. the liver arises from the same diverticulum as the body and tail of the pancreas the hepatic diverticulum is of mesoderm origin the hepatic diverticulum grows into the septum transversum all of the above 139. The root of the transverse mesocolon runs from side to side because it is associated with the transversely oriented pronephros the ascending and descending colons become secondarily retroperitoneal it is derived from the septum transversum the transverse colon is the first part of the gut to reenter the abdominal cavity this path is primitive for the hindgut dorsal mesentery Page 26 140. Which of the following developmental events causes the entrance to the lesser sac of the peritoneal cavity to be restricted to the epiploic foramen development of the spleen within the upper mesogastrium with formation of the lienorenal ligament attachment of the falciform ligament to the anterior abdominal wall and coronary ligament fusion of the dorsal and ventral pancreatic diverticula fusion of the anterior and posterior sheets of the lower mesogastrium inferior to the transverse colon fusion of visceral peritoneum on the liver to parietal peritoneum on the inferior vena cava 141. No doubt there is some slight variation in the precise site on the gut from which the hepatopancreatic diverticulum arises. This accounts for the occurrence of an hepatic artery arising from the SMA the location of Cantlie's line dividing the physiological right and left lobes of the liver the size of the inferior recess of the lesser sac the persistence of a duct of Santorini independent of the duct of Wirsung whether or not there occurs a Meckel's diverticulum 142. Concerning development of the mesenteries the dorsal mesogastrium persists as the lesser omentum the ventral mesentery of the stomach is resorbed, leaving no adult derivative the dorsal mesentery of the hindgut persists as the sigmoid mesocolon the dorsal mesentery of the midgut maintains its embryonic midline attachment throughout development none of the above 143. Concerning development of the mesenteries the ventral mesentery of the hindgut persists as the sigmoid mesocolon the connection between the lesser sac and greater sac becomes restricted to the epiploic foramen when the falciform ligament develops the transverse mesocolon is the only part of the dorsal mesentery to retain its original embryonic root the upper mesogastrium gives rise to the lesser omentum the lower mesogastrium gives rise to the greater omentum 144. The developmental reason that the superior mesenteric artery is the source of the right hepatic artery in ~25% of adults is the right lobe of the liver may be derived from the segment of the midgut caudal to the vitelline duct the liver grows into the septum transversum, which is supplied by the superior mesenteric artery the arterial supply to the liver is established after the duodenum becomes retroperitoneal the liver arises from a diverticulum adjacent to the cranial border of the midgut the superior mesenteric artery is the main supply of the caudal one-quarter of the abdominal foregut Page 27 145. Concerning Hirschsprung's disease (congenital megacolon) it occurs more commonly in males than in females it is a defect in migration of neural crest cells to their proper sites the enlarged portion of the colon is actually the normal portion may be revealed by delayed passage of meconium and painful defecation all of the above 146. Concerning anomalies of gastrointestinal development failure of the hindgut to rotate to the left leads to subhepatic cecum esophageal atresia is one of the main causes of meconium aspiration syndrome failure of the vitelline duct to degenerate leads to jejunal stenosis failure of the midgut to enter the umbilical cord during the fifth week of embryonic life leads to the condition known as omphalocele failure of neural crest cells to migrate into the colon leads to congenital megacolon 147. Hirschsprung's disease is accompanied by perinatal (i.e., within a few days of birth) diarrhea results in meconium entering amniotic fluid is associated with abdominal distension leads to pancreatic divisum is caused by failure of the descending colon to become retroperitoneal 148. Hirschsprung's disease is associated with absence of parasympathetic ganglion cells in the wall of the rectum pale meconium and regurgitation of milk during the first two weeks after birth diarrhea beginning in infancy dilatation of the rectum all of the above 149. Failure of the vitelline duct (yolk stalk) to completely regress may lead to umbilical vein occlusion gastroschisis duodenal stenosis Meckel's diverticulum subhepatic cecum 150. Concerning anomalies of gastrointestinal development failure of the midgut to recanalize leads to epispadias failure of the midgut to return from the umbilical cord leads to omphalocele Hirschsprung's disease is primarily a defect in rotation of the midgut loop failure of growth of the "oblique" colon leads to subsplenic caecum failure of the vitelline duct to degenerate leads to congenital megacolon Page 28 151. Omphalocele is associated with increased maternal serum alpha-fetoprotein is associated with temporary inflammation of the ileum is usually not diagnosed until infant feeding problems arise is associated with polyhydramnios has a better prognosis than umbilico-ileal fistula 152. Concerning pancreatic divisum it is a failure of normal development of the main pancreatic duct it is frequently associated with duodenal obstruction leading to neonatal vomiting it occurs more frequently if the hepatopancreatic diverticulum arise from the midgut all of the above none of the above 153. Concerning anomalies of gastrointestinal development gastroschisis is the name given to a condition in which failure of the stomach to recanalize causes its lumen to open into the peritoneal cavity umbilico-ileal fistula arises from persisting patency of the vitelline duct and is asymptomatic in 80 - 90% of cases, duodenal atresia presents no signs or symptoms until shortly (~1 week) after birth failure of the midgut to enter the umbilical cord during the fifth week of embryonic life leads to the condition known as omphalocele none of the above 154. Omphalocele is associated with an abnormal protein in the amniotic fluid is usually not diagnosed until infant feeding problems arise has a better prognosis than gastroschisis is the result of an error in hindgut development is associated with temporary inflammation of the ileum 155. Concerning Meckel's diverticulum it results from a defect in neural crest migration into the midgut it attaches to the antimesenteric border of the ileum its presence is associated with cardiac defects it may contain splenic tissue it is an inconsistent remnant of the allantoic duct 156. With respect to the normal development of the urinary system: the ureteric bud gives rise to the ureter, renal pelvis, calyces and pyramids the mesonephros develops into the adult kidney the kidneys and suprarenal glands develop and ascend together the urinary bladder is derived from the processus vaginalis none of the above Page 29 157. With respect to the normal development of the kidney and urinary bladder: the ureters are derived from the urogenital sinus the ureteric bud grows into the pronephros to initiate kidney formation the Rathke and Tourneux folds partition the cloaca into the bladder and anal canal the kidney and suprarenal gland form together via process of mutual induction all of the above 158. With respect to normal development of the urinary system: as the kidneys ascends, their hili rotate to face medially most nephrons are formed at the time of birth the adult kidney is derived from the ureteric bud and the metanephric blastema the cloaca is partitioned into the urinary bladder and the anal canal all of the above 159. With respect to the normal development of the kidney and urinary bladder: an outgrowth from the mesonephric duct becomes the collecting system of the kidney the urinary bladder is derived from the allantois the kidney and gonads are derived from the lateral plate mesoderm the true (hind)kidney begins to function at birth none of the above 160. With respect to developmental errors in the urinary system: "pancake" kidneys result from supernumerary kidneys supernumerary renal veins are more common than supernumerary renal arteries there are both dominant and recessive autosomal variants of polycystic kidney disease the urachus is a type of fistula between rectum and urinary bladder all of the above 161. With respect to developmental abnormalities of the urinary system: supernumerary renal vessels are rare. a urachal fistula is an abnormal communication between rectum and bladder. a "horseshoe-shaped" kidney is trapped in the pelvis by the median sacral artery renal agenesis can result if the ureteric bud fails to develop. all of the above 162. With respect to developmental errors in the urinary system: ureteric duplication is a more serious condition in males than females improper division of the cloaca can result in fistulas between urinary bladder and rectum supernumerary renal vessels never have clinical (health-related) consequences polycystic kidneys cause exstrophy of the urinary bladder none of the above Page 30 163. With respect to developmental abnormalities of the urinary system: a "horseshoe-shaped" kidney is trapped in the pelvis by the inferior mesenteric artery a urachal fistula can connect the umbilicus to the urinary bladder supernumerary renal arteries are common (> 10%) ectopic ureteric orifices (via ureteric duplication) can be associated with urinary incontinence in females all of the above 164. With respect to normal development of the gonadal-genital system: the gubernaculum of the testes and the round ligament of the uterus are developmental homologues mesonephric excretory tubules develop into seminiferous tubules in males the vestibule of the vagina and most of the penile urethra both derive from urogenital sinus the vagina is derived from both urogenital sinus and the uterovaginal primordium all of the above 165. With respect to normal development of the gonadal-genital system: penis length is uncorrelated with stature (body height) in adult males the round ligament of the uterus in females is homologous with the vas deferens of males primordial germ cells invade the indifferent gonad and initiate the formation of either testes or ovaries (depending on karyotype) erectile tissues of the external genitalia derive primarily from ectoderm the mesonephric duct differentiates into uterine tubes, uterine body and the proximal portion of the vagina in females 166. During normal development of the gonadal-genital system: the testis is primarily an elaboration of the indifferent gonadal cortex the mesonephric duct gives rise to prostate gland and seminal vesicles in males the penile urethra in males is homologous with the vagina in females the vagina is derived from both urogenital sinus and paramesonephric ducts the genital tubercle gives rise to the labia majora in females 167. During normal development of the gonadal-genital system: the mesonephric duct gives rise to the uterus and fallopian tubes in females the ovary is derived primarily from the medulla of the indifferent gonad the male scrotum and female labia minora are developmental homologues the paramesonephric duct becomes the vas deferens and seminal vesicles in males none of the above Page 31 168. With respect to developmental errors in the gonadal-genital system: hypospadias is a defect in the ventral closure of the penile urethra the ovaries are normal in females with Turner's Syndrome (XO) vaginal duplication occurs if the mesonephric ducts fail to fuse properly clitoral hypertrophy is common in the Testicular Feminization Syndrome (androgen insensitivity syndrome) none of the above 169. With respect to abnormal development of the gonadal-genital system: hypospadias is usually associated with exstrophy of the bladder the XO karyotype results in a completely normal female phenotype persisting elements of the paramesonephric ducts give rise to Gartner's duct cysts in females testicular feminization is a form of female (XX) pseudo-hermaphroditism none of the above 170. With respect to developmental errors in the gonadal-genital system: Gartner's duct cysts develop from persisting remnants of the mesonephric ducts in females epispadias can be associated with exstrophy of the urinary bladder a persisting urogenital sinus is one possible symptom of congenital adrenal hyperplasia (adrenogenital syndrome) in females partial and complete duplication of the uterus can occur if the paired paramesonephric ducts fail to fuse and canalize properly all of the above 171. With respect to abnormal development of the gonadal-genital system: hypospadias of the penis can occur anywhere along the dorsal surface of the penis if the primordial germ cells fail to migrate into the indifferent gonads, the default phenotype is superficially male vaginal agenesis results if the paired mesonephric ducts fail to fuse in the midline penile agenesis (Stern's Syndrome) occurs when the urogenital sinus fails to develop clitoral enlargement and fusion of the labia majora can result due to excessive production of androgens by the adrenal cortex in female 172. The middle ear ossicles are derived form the ectomesenchyme of: the first and second somitomeres the first branchial arch only the opercular process the second branchial arch only none of the above Page 32 173. Concerning branchial arches the mesenchyme filling all arches is derived predominantly from Hensen's node (the primitive node) the striated muscles of the first arch are innervated by the facial nerve the endoderm of the 2nd arch becomes the epidermis of the external auditory meatus the ectoderm on the external surfaces of the 3rd-6th arches becomes the epidermis of the lateral neck the cartilage of the first arch gives rise to the malleus and incus 174. The anterior two thirds of the tongue derives primarily from the ectomesenchyme between the second branchial arches one median tongue bud the hypobranchial eminence two lateral tongue buds the copula 175. Concerning branchial arches the external surfaces of the 3rd-6th arches become buried beneath the skin of the neck the cartilage of the first arch gives rise to the malleus and incus the striated muscles derived from somitomere cells entering the second arch become muscles innervated by C.N. VII the mesenchyme filling all arches is derived predominantly from neural crest all of the above 176. Concerning branchial arches they are filled with mesenchyme derived primarily from neural crest the muscles of facial expression derive from ectomesenchyme of the second branchial arch the cartilage of the first arch gives rise to malleus, incus, and stapes all of the above none of the above 177. Concerning the branchial arches the cartilage of the second arch gives rise to the three middle ear ossicles the ectoderm of the third arch forms the epidermis innervated by the transverse cervical nerve they are filled with mesoderm derived chiefly from the primitive node because the branchial arches are primarily concerned with development of the neck, defects in their development do not result in major facial malformations none of the above Page 33 178. Concerning the branchial arches the cartilage of the second arch gives rise to the body of the mandible but not its ramus the ectoderm of the third and fourth arches forms the epidermis over the skin innervated by the transverse cervical nerve even though branchial arches are primarily concerned with development of the neck, defects in their development are often associated with malrotations of the gut the cartilage of the first arch gives rise to incus and malleus, but not the stapes all of the above 179. A branchial cyst occurs because the opercular process of the 2nd branchial arch fuses with the external surface of the 3rd branchial arch instead of the epipericardial ridge the fourth pharyngeal pouch on one side breaks loose of the pharynx and fills with fluid the laryngotracheal diverticulum detaches from the pharyngeal floor and its proximal opening seals off the openings of the cervical sinus seal but the sinus space remains fluid-filled none of the above 180. Concerning anomalies of branchial arch development they may be associated with abnormalities of septation of the truncus arteriosus due the role of ectomesenchyme in both branchial and truncal development they may be associated with extraocular muscle absence due to origin of these muscles from the ectomesenchyme of the first and second branchial arches branchial fistulas usually connect the middle ear cavity to the pharyngeal recess as a result of cervical sinus persistence a bifid tongue results if the copula fails to migrate cranially, contact, and fuse with the median tongue bud none of the above 181. With which of the following structures do the inferior parathyroid glands have their closest development relationship the epiglottic swelling the thymus the fourth pharyngeal pouches the laryngotracheal diverticulum the superior parathyroid glands 182. Concerning pharyngeal pouches the first pouches have no adult derivatives the second pouches become the thyroid gland the third pouches become the thymus and the inferior parathyroid glands the fourth pouches fuse bilaterally to become the transverse sinus of the pericardial cavity none of the above Page 34 183. Concerning derivatives of pharyngeal pouches the first pouch becomes the lining of the external auditory meatus the sixth pouch becomes a lung the fourth pouch becomes the nonlymphoid part of the thymus each third pouch becomes a lobe of the thyroid gland the second pouch becomes the epithelium overlying the palatine tonsil 184. Concerning pharyngeal pouches the first pouch becomes the epithelial lining of the tympanic cavity and auditory tube the second pouch becomes the epithelial lining of the palatine tonsil the nonlymphoid part of the thymus is derived from the third pouch all of the above none of the above 185. Concerning pharyngeal pouches the third pouch becomes the C-cells (calcitonin secreting cells) of the thyroid the second pouch becomes the laryngeal ventricle the first pouch becomes the tympanic cavity and auditory tube the fourth pouch becomes the inferior parathyroid glands all of the above 186. Concerning pharyngeal pouches the fourth pouch gives rise to the superior parathyroid glands the second pouch gives rise to the auditory tube the first pouch gives rise to the thyroid gland the third pouch gives rise to the C-cells (calcitonin secreting cells) of the thyroid all of the above 187. Which of the following is a recognizable anomaly of parathyroid development mediastinal location of parathyroids derived from the 3rd pharyngeal pouch esophageal atresia associated with tracheo-esophageal fistula the presence of supernumerary parathyroids arising from the 5th pharyngeal pouch lingual location of parathyroids derived from the 4th pharyngeal pouch a midline parathyroglossal cyst 188. Which of the following is a recognizable anomaly of parathyroid development absence of parathyroids associated with an enlarged thymus location of the superior parathyroids deep to the cricothyroid membrane location of the inferior parathyroids deep to the manubrium origin of parathyroids from ectoderm instead of endoderm the presence of accessory parathyroids arising from the 5th pharyngeal pouch Page 35 189. Which of the following is a recognizable anomaly of thyroid development extension of thyroid tissue from the isthmus into the lumen of the trachea a midline mass posterior to the pharynx at the level of the hyoid bone bilateral cysts located at the level of the greater cornua of the hyoid bone uptake of I123 by tissue in the midline of the tongue none of the above 190. Which of the following is a recognizable anomaly of structures arising from the dorsal portions of the 3rd pharyngeal pouches location of the superior parathyroids in the posterior mediastinum location of the inferior parathyroids deep to the manubrium location of the inferior parathyroids superficial to the thyroid gland location of the thymus in the posterior mediastinum location of the superior parathyroids deep to the cricothyroid membrane 191. A major structure arises as an outpocketing of the floor of the pharynx between the copula caudally and the median tongue bud cranially. rs in its development is likely to cause a midline mass just below the hyoid bone I123 uptake in masses on either side of the cricoid cartilage hypocalcemic tetany an external branchial sinus an internal branchial sinus 192. Concerning the thyroid diverticulum it arises from a site that becomes the lingual frenulum its failure to migrate caudally is associated with defects of aorticopulmonary septation improper regression of the thyroglossal ducts may lead to bilateral swellings on the lateral surfaces of the neck all of the above none of the above 193. A major structure arises as an outpocketing of the floor of the pharynx between the copula caudally and the median tongue bud cranially. An error in its development is likely to cause I123 uptake in masses on either side of the cricoid cartilage pathologically low levels of blood calcium a midline mass just below the hyoid bone fluid leaking from a tiny hole on the side of the neck along the anterior border of sternocleidomastoid a fistula connecting the tonsillar bed to the trachea Page 36 194. Which of the following is the most common anomaly arising from a defect in development of the thyroid diverticulum the aberrant occurrence in the thymus of tissue that concentrates I123 a cyst located beneath the skin of the anterior surface of the neck, just inferior to the hyoid bone a sinus extending from the thyrohyoid membrane to the deep surface of the sternohyoid muscle just inferior to its insertion a cyst located at the anterior edge of the sternocleidomastoid at the level of the cricoid cartilage a fistula between the trachea and the esophagus immediately below the cricoid cartilage 195. Concerning development of the face, the following statement is FALSE the intermaxillary segment is formed by the merger of the two medial nasal prominences the lateral nasal prominences give rise to the alae of the nose the epithelial lining of the nasal cavity is derived from ectoderm the maxillary prominences meet in the midline to form the philtrum of the upper lip and the nasal septum the mandibular prominences form the caudal boundary of the stomodeum 196. Concerning the maxillary prominences they give rise to the entire upper lip they form the lower one-third of the nasal septum they merge with both the medial and lateral nasal prominences they contain the developing nasal placodes during the 5th week they contribute to the primary palate 197. Concerning development of the face the nasolacrimal groove lies between the lateral nasal prominence and the maxillary prominence the nasal cavities originate as evaginations of the endoderm cranial to the first pharyngeal pouch the intermaxillary segment is formed by fusion of the two frontonasal prominences the secondary palate derives from the fused palatine processes of the medial nasal prominences the mandible is derived from ectomesenchyme of the second branchial arch whereas the maxilla is derived from ectomesenchyme of the first branchial arch 198. Which one of the following statements is FALSE the nasal septum is derived from somitomere cells that migrate between the nasal sacs the fused medial nasal prominences give rise to the philtrum of the lip, premaxilla, and primary palate the maxillary and mandibular prominences are produced by mesenchyme derived from neural crest cells the soft palate is derived from the lateral palatine processes (palatine shelves) the lining of the nasolacrimal duct is derived from ectoderm between the maxillary prominence and the lateral nasal prominence Page 37 199. Clefts of the secondary palate result from: failure of the median palatine process to fuse with the nasal septum failure of the lateral palatine processes to fuse with each other and the nasal septum failure of the median palatine processes to fuse with the lateral palatine processes failure of the median palatine processes to fuse with the intermaxillary segment none of the above 200. Concerning clefts of the face and palate, the following statement is FALSE clefts of the primary palate result from failure of the intermaxillary segment to unite with the maxillary segment(s) clefts of the secondary palate are more common in males than in females, whereas clefts of the lip are equally distributed among sexes clefts of the primary palate always occur between the lateral incisors and the canines clefts of the soft palate result from failure of the lateral palatine processes to unite posteriorly clefts of the secondary palate result from failure of the lateral palatine processes to unite with one another and the nasal septum 201. Concerning development of the face, which of the following is true unilateral cleft lip is due to failure of the medial nasal prominences to merge with one another the most common facial anomaly is cleft palate cleft palate results from failure of the primary palate to fuse with the nasal septum oblique facial cleft results from failure of the lateral nasal prominence to merge with the medial nasal prominence none of the above 202. Unilateral cleft upper lip is due to: a failure of the maxillary prominence to merge with the medial nasal prominence of the affected side a failure of the two medial nasal prominences to merge into the intermaxillary segment a failure of the frontonasal prominence to merge with the mandibular prominence on the affected side a failure of the maxillary prominence to merge with the lateral nasal prominence of the affected side none of the above 203. Which of the following is true of a lateral lip cleft it results from the failure of the medial nasal prominences to merge together it results from failure of the maxillary prominence to merge with the lateral nasal prominence it occurs approximately half as frequently as cleft palate usually exposes the nasolacrimal duct to the surface of the face it is more common in males than females Page 38 204. Concerning cleft lip and cleft palate although median cleft lip is more common than median cleft palate, it is less often associated with other developmental anomalies it is very unusual for the two conditions to occur together in the same neonate cleft lip is more common in females, while cleft palate is more common in males cleft lip occurs more frequently than cleft palate none of the above 205. Cleft of the secondary palate is associated with (poly)hydramnios microform cleft lip extended position of the neck in fetal life early descent of the tongue into the floor of the mouth oligohydramnios Page 39
