These cells oppose the effects of PTH by secreting calcitonin. For 10 points each:
[10h] Name these cells that are derived from the ultimo·pharyngeal body of the fourth pharyngeal pouch in humans. Approximately 0.1 percent of the human thyroid gland is constituted by these cells.
ANSWER: parafollicular cells [or C cells; reject “follicular cells”]
[10m] In most cases, calcitonin induces a decrease in plasma calcium concentration by inhibiting the activity of these cells. Development of these macrophage-like cells is stimulated by M-CSF and RANK ligand.
ANSWER: osteoclasts [reject “osteoblasts”]
[10e] Calcitonin also opposes the effects of this vitamin that aids in calcium absorption. This vitamin can be synthesized in the skin with the help of UVB radiation.
ANSWER: vitamin D [accept vitamin D3 or cholecalciferol; accept vitamin D2 or ergocalciferol; accept calcitriol]
<Kane Nguyen, Biology>