A 38-year-old woman is brought to the emergency department after a motor vehicle collision. She sustained no injuries in the collision but is adamant that she did not see the car that hit her along the front side of her vehicle. The patient also reports that she has been having daily headaches and has not menstruated in 4 months. On physical examination, there is bitemporal hemianopsia but no other abnormalities. MRI of the brain is shown below. This patient's lesion most likely originates from which of the following embryologic layers?

Question

A 38-year-old woman is brought to the emergency department after a motor vehicle collision.  She sustained no injuries in the collision but is adamant that she did not see the car that hit her along the front side of her vehicle.  The patient also reports that she has been having daily headaches and has not menstruated in 4 months.  On physical examination, there is bitemporal hemianopsia but no other abnormalities.  MRI of the brain is shown below.  This patient's lesion most likely originates from which of the following embryologic layers?

Quizplus · Accepted Answer

11ec160b_374c_bd68_9249_6d19050a827e_MD0001_00 Bitemporal hemianopsia, amenorrhea, and enlargement of the pituitary gland on brain imaging are suggestive of a prolactin-secreting pituitary adenoma. Prolactinomas develop from lactotroph cells in the anterior pituitary (adenohypophysis). All tissues can be traced back to 3 primary germ layers: ectoderm, mesoderm, and endoderm. These germ layers form during the process of gastrulation, which occurs during week 3 of embryogenesis. Gastrulation is initiated by formation of the primitive streak, a thickening of the epiblast cell layer that appears at the caudal end of the embryo and grows cranially. Epiblast cells then undergo an epithelial-to-mesenchymal transition, causing them to lose their cell-cell adhesion properties. This allows them to migrate downward through the primitive streak to form the mesoderm (Choice B) and endoderm (Choice A) layers. The remainder of the epiblast layer forms the ectoderm. About 2 days after gastrulation begins, some of the epiblast cells migrate cranially through the primitive node (the cephalic end of the primitive streak) to form a midline cellular cord known as the notochord. The notochord induces the overlying ectoderm to differentiate into the neuroectoderm and form the neural plate. The neural plate gives rise to the neural crest and neural tube cells (Choices C and D), while the remainder of the ectoderm becomes the surface ectoderm. The anterior pituitary is derived from the Rathke pouch, an evagination of the surface ectoderm that lines the fetal oral cavity. In contrast, the posterior pituitary (pars nervosa and pituitary stalk) is derived from the infundibulum, an extension of neuroectoderm from the diencephalon. (Choice E) The notochord becomes the nucleus pulposus of the intervertebral disks in adults. Educational objective: All adult cells and tissues can be traced back to the 3 primary germ layers: ectoderm, mesoderm, and endoderm. The ectoderm gives rise to the surface ectoderm, neural tube, and neural crest.

A 38-Year-Old Woman Is Brought to the Emergency Department After