Development of the cartilaginous connecting apparatuses in the fetal sphenoid, with a focus on the alar process

The human fetal sphenoid is reported to have a cartilaginous connecting apparatus known as the alar process (AP), which connects the ala temporalis (AT) (angle of the greater wing of the sphenoid) to the basisphenoid (anlage of the sphenoid body). However, how the AP develops in humans is unclear. I...

Full description

Saved in:

Bibliographic Details
Published in:	PloS one 2021-07, Vol.16 (7), p.e0251068-e0251068
Main Authors:	Yamamoto, Masahito, Abe, Hiroaki, Hirouchi, Hidetomo, Sato, Masaki, Murakami, Gen, Rodríguez-Vázquez, José Francisco, Abe, Shinichi
Format:	Article
Language:	eng
Subjects:	Biology and Life Sciences Bones Carotid arteries Cartilage Cavitation Embryogenesis Embryology Embryos Fetus Fetuses Growth Mammals Medicine and Health Sciences Morphology Perichondrium Physiological aspects Physiological research Skull Sphenoid bone
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	The human fetal sphenoid is reported to have a cartilaginous connecting apparatus known as the alar process (AP), which connects the ala temporalis (AT) (angle of the greater wing of the sphenoid) to the basisphenoid (anlage of the sphenoid body). However, how the AP develops in humans is unclear. In addition, although the AP is a common structure of the mammalian chondrocranium, little is known about whether it is really a fundamental feature in mammals. This study examined the histological sections of 20 human embryos and fetuses from 6 to 14 weeks of development, of 20 mouse embryos from embryonic days 12–18, and of 4 rats embryos form embryonic days 17 and 20. In addition, we reconsidered the definition of the AP by comparing humans and rats with mice. In humans, the AP was continuous with the basisphenoid but was separated from the AT by a thick perichondrium. Then, the AP–AT connection had a key-and-keyhole structure. Unlike a joint, no cavitation developed in this connection. In mice, there was no boundary between the AT and the basisphenoid, indicating the absence of the AP in the mouse chondrocranium. In rats, the AP was, however, separated from the AT by a thick perichondrium. Therefore, the AP can be defined as follows: the AP is temporally separated from the AT by a thick perichondrium or a key-and-keyhole structure during the fetal period. This is the first study that confirms the absence of the alar process in the mice skull, and its presence in other mammals skull should be further investigated.
ISSN:	1932-6203 1932-6203