A 7-month-old boy is brought to the pediatrician by his mother for concern about constipation for 1 week. The mother has started weaning him from breastfeeding, and soft food was introduced last week. The mother reports that he also seems to have difficulty passing flatus, and she thinks his abdomen seems distended. X-rays of the abdomen demonstrate evidence of bowel obstruction. Laboratory tests are ordered, and the patient is admitted to the hospital. Colonoscopy is performed and biopsy shows aganglionic rectal layers.
Which one of the following structures have the same embryonic origin as the structure causing the disease in this patient?
B) Cornea
This patient has Hirschsprung disease, which is the absence of ganglion cells, most often in the rectosigmoid portion of the colon (but sometimes extending proximally to the sigmoid colon) due to failure of neural crest cradiocaudal migration between 4 and 7 weeks of gestation. The cornea comes from ectoderm just like the neural crest cells.
Answer choice A: Biliary gland epithelial layer, is incorrect. The epithelial layer of gall bladder comes from endoderm.
Answer choice C: Kidney, is incorrect. The kidney comes from urogenital ridge of mesoderm.
Answer choice D: Spleen, is incorrect. The spleen is believed to be of mesoderm origin.
Answer choice E: Thymus, is incorrect. The thymus originates from endoderm.
Key Learning Point
Ectoderm is one of the embryonic germ layers that is responsible for differentiating into many body structures which include the eyes, skin, nervous system, and exocrine glands.
