Parasphenoid

Parasphenoid

The Parasphenoid is a bone found in the skulls of many vertebrates, and is considered part of the cranial skeleton. It is located on the ventral side of the skull, between the basal plate and the palate. The parasphenoid plays a crucial role in the structural support of the skull and is involved in the formation of the braincase.

File:Parasphenoid bone in fish skull.png

Parasphenoid bone in a fish skull

Structure

The parasphenoid is a single, unpaired bone that is typically elongated and flat. It is often fused with the basisphenoid bone in mammals, forming the sphenoid bone. In many fish and amphibian species, the parasphenoid extends towards the rear of the skull, forming a 'spike' known as the parasphenoid rostrum.

Function

The parasphenoid provides structural support to the skull and contributes to the formation of the braincase. It also forms part of the roof of the mouth in many species, contributing to the structure of the palate.

Evolution

The parasphenoid is thought to have evolved from the ventral part of the ancestral vertebrate's chondrocranium, which was originally composed of cartilage. Over time, this cartilage became ossified, forming the parasphenoid bone.

Clinical significance

In humans, the parasphenoid is often fused with the basisphenoid bone to form the sphenoid bone. Abnormalities in the development of these bones can lead to conditions such as Crouzon syndrome and Apert syndrome, which are characterized by craniofacial deformities.

See also

• Sphenoid bone
• Cranial bones
• Chondrocranium