Which landmark is described as a constructed point, not an anatomical point, located at the geometric center of the pituitary fossa?

The sella, or sella turcica, is indeed the landmark that is considered a constructed point rather than an anatomical point. It is located at the geometric center of the pituitary fossa, which is the shallow depression in the sphenoid bone of the skull where the pituitary gland rests. In cephalometric analysis, the sella serves as a critical reference point due to its consistent geometric location in relation to other anatomical landmarks, making it essential for orthodontic assessments and treatment planning.

The other landmarks listed, such as poryion, orbitale, and glabella, are anatomical points derived from specific physical features. The poryion, for instance, refers to the external auditory meatus, while orbitale is the lowest point on the orbital margin, and glabella is the smooth area between the eyebrows. These points have defined anatomical significance but do not share the constructed geometric nature of the sella, which is why the sella is distinct in its classification as a constructed point.