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USMLE STEP 1 QUESTIONS AND ANSWERS FULL TEST BANK
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USMLE STEP 1 QUESTIONS ANDANSWERS FULL TEST BANK
what germ layer are odontoblasts derived from? Correct Answer
neural crest (Crest toothpaste)
symptoms of mesoderm defects Correct Answer VACTERL:
Vertebral defects
Anal atresia
Cardiac defects
Tracheo-Esophageal fistula
Renal defects
Limb defects
at which days in fetal development do the amnion and chorion
form? Correct Answer chorion forms at day 3
amnion forms at day 8
what are the components of the umbilical cord? Correct Answer 2
umbilical arteries
1 umbilical vein
urachus
all surrounded by Wharton's jelly
structures that perform fetal erythropoiesis during development, in
order Correct Answer Young Liver Synthesizes Blood:
Yolk sac (3-8 wk)
Liver (6-30 wk)
Spleen (9-28 wk)
Bone marrow (28+ wk)
what is the adult derivative of the umbilical arteries? Correct
Answer umbiLical arteries become mediaL umbilical ligaments
,what is the adult derivative of the allantois/urachus? Correct
Answer allaNtois becomes mediaN umbilical ligaments
what is the adult derivative of the 1st aortic arch? Correct Answer
part of the MAXillary artery (1st arch is MAXimal)
what are the adult derivatives of the 2nd aortic arch? Correct
Answer Stapedial artery (Second arch) and hyoid artery
what are the adult derivatives of the 3rd aortic arch? Correct
Answer common Carotid artery and internal Carotid artery (C is
3rd letter of alphabet)
what are the adult derivatives of the 4th aortic arch? Correct
Answer aortic arch and right subclavian artery (4th arch = 4 limbs
= systemic circulation)
what is the defect in spina bifida occulta?
- in meningocele?
- in myelomeningocele? Correct Answer bony spinal canal fails to
close, but no herniation
- meninges herniate through
- meninges and spinal cord herniate through
what is Chiari type II? Correct Answer cerebellar tonsils herniate
through foramen magnum
what is Dandy-Walker? Correct Answer large posterior fossa,
absent cerebellum, enlarged 4th ventricle
what is the defect in holoprosencephaly? Correct Answer
cerebral hemispheres do not separate across midline
what is the defect in syringomyelia?
,- symptom? Correct Answer enlarged central canal of spinal cord
- damages crossing fibers of spinothalamic tract
- so bilateral loss of pain and temperature sense
what germ layers are the different parts of the branchial apparatus
derived from? Correct Answer CAP covers outside from inside:
Clefts = ectoderm
Arches = mesoderm
Pouches = endoderm
innervations and general functions of derivatives of each
branchial arch Correct Answer arch 1 - CN V2 and V3 - chewing
arch 2 - CN VII - facial expression
arch 3 - CN IX - stylopharyngeus
arch 4 - CN X - swallowing
arch 6 - CN X - speaking
name some derivatives of branchial arch 1 Correct Answer
Meckel's cartilage (Mandible, Malleus, incus, sphenoMandibular
ligament)
Muscles of Mastication (temporalis, Masseter, lateral and Medial
pterygoids)
Mylohyoid, anterior belly of digastric, tensor tympani, tensor veli
palatini, anterior tongue
what is the defect in Treacher Collins syndrome?
- symptoms? Correct Answer 1st arch neural crest fails to
migrate
- mandibular hypoplasia, facial abnormalities
name some derivatives of branchial arch 2 Correct Answer
Stapes, Styloid process, lesser horn of hyoid, Stylohyoid ligament
muscles of facial expression, Stapedius, Stylohyoid, posterior
belly of digastric
, name some derivatives of branchial arch 3 Correct Answer
greater horn of hyoid, stylopharyngeus (innervated by
glossopharyngeal nerve)
what are the derivatives of the 3rd branchial pouch? Correct
Answer 3rd pouch contributes to 3 structures:
thymus and inferior parathyroids
what is the defect in DiGeorge syndrome?
- symptoms? Correct Answer aberrant development of 3rd and
4th branchial pouches (form thyroid and parathyroids)
- T-cell deficiency and hypocalcemia
what ear bones and muscles derive from the 1st branchial arch?
- from the 2nd? Correct Answer 1st: Malleus/incus, tensor
tyMpani
2nd: Stapes, Stapedius
embryologic components of diaphragm Correct Answer Several
Parts Build Diaphragm:
Septum transversum
Pleuroperitoneal folds
Body wall
Dorsal mesentery of esophagus
innervation of diaphragm Correct Answer C3,4,5 (keeps the
diaphragm alive)
what is the defect in gastroschisis? Correct Answer failure of
lateral body folds to fuse, causes extrusion of abdominal contents
what is the defect in Potter's syndrome?
- symptoms? Correct Answer bilateral renal agenesis in utero
(due to malformed ureteric bud) causes oligohydramnios (babies
with Potter's can't Pee in utero)
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