-

A. In the gonads at week 4 of embryonic development
B. In the yolk sac at week 4 of embryonic development
C. In the gonads at month 5 of embryonic development
D. In the yolk sac at month 5 of embryonic development
E. In the gonads at puberty
Medcloud™
Case #14
Subject: Embryology
The correct answer is B
Primordial germ cells, the predecessors to gametes, are first seen in the wall of the yolk sac at
week 4 of embryonic development, and they migrate into the gonads at week 6.
Medcloud™
Case #15
Subject: Embryology
A 2200-g (4-lbs 13-oz) female newborn is delivered at term to a 37-year-old gravida 2, para 1 woman. The newborn is at the 10th percentile for length, 14th percentile for weight, and 3rd percentile for head circumference. Examination shows “punched-out“ skin lesions on the scalp, cleft lip, and a small chin. There is a convex-shaped deformity of the plantar surface of the feet. Auscultation shows a holosystolic murmur heard best at the left lower sternal border. Some of her intestines protrude through the umbilicus, covered by a thin membranous sac. An MRI of the brain shows a single ventricle and a fusion of the basal ganglia. Which of the following additional findings is most likely to be seen in this patient?
A. Polydactyly
B. Webbed neck
C. Single palmar crease
D. Overlapping fingers
E. Hypoplastic philtrum
Medcloud™
Case #15
Subject: Embryology
The correct answer is A [ 61% ]
Polydactyly of the hands and sometimes feet (typically hexadactyly) is a characteristic finding in children with trisomy 13. Features in addition to those seen in this newborn include low-set, malformed ears, microphthalmia/anophthalmia, colobomata, polycystic kidney disease, and capillary hemangiomata.
Approximately 80% of affected children have a congenital heart defect, as suspected in this newborn, whose heart murmur is consistent with a ventricular septal defect. Only supportive treatment is available for infants with trisomy 13, and the prognosis is usually very poor (only 5% of infants survive past 6 months of age).
Medcloud™