Distinct delayed development of the basisphenoid-ethmoid interface in human fetuses: a histological study using human...

Area of Science:

• Developmental biology
• Craniofacial anatomy
• Histology

Background:

• The presphenoid-ethmoid synchondrosis (PSept) is a key midline skull base growth center in non-human primates.
• The existence of a human developmental analogue to the PSept has remained unclear.

Purpose of the Study:

• To investigate the basisphenoid-ethmoid (SPH-ETH) junction in human fetuses.
• To determine if a human counterpart to the primate PSept exists.

Main Methods:

• Histological examination of sagittal sections from 20 human fetuses (11-39 weeks gestation).
• Analysis of cellular density, extracellular matrix, and structural organization at the SPH-ETH junction.
• Comparison of findings with primate PSept morphology.

Main Results:

• A distinct low-density chondrocyte zone (<8 cells per 0.1 mm²) was identified anterior to the pituitary fossa in human fetuses from 15-16 weeks.
• This zone exhibited altered morphology, increased extracellular matrix, and fibrous structures in late-term fetuses (≥29 weeks).
• Two late-term fetuses showed an anterior ossification center, creating a bipolar ossification pattern analogous to the primate PSept.

Conclusions:

• A reproducible, sparsely populated, fiber-containing cartilage region exists at the human SPH-ETH junction.
• This region, often associated with an anterior ossification center, is proposed as the human analogue of the PSept.
• The 'transient presphenoid' likely integrates into the definitive ethmoid during late fetal development.