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The eyes sit in bony cavities called the orbits, in the skull. There are six extraocular muscles that control eye movements. The front visible part of the eye is made up of the whitish sclera, a coloured iris, and the pupil. A thin layer called the conjunctiva sits on top of this. The front part is also called the anterior segment of the eye.
The lateral wall is formed by the frontal process of zygomatic and more posteriorly by the orbital plate of the greater wing of sphenoid. The bones meet at the zygomaticosphenoid suture. The lateral wall is the thickest wall of the orbit, important because it is the most exposed surface, highly vulnerable to blunt force trauma.
Crocodilian form of crurotarsal ankle. The astragalus (pink) is fixed to the tibia (green) by a suture. Adapted with permission from Palaeos. In the type of crurotarsal ankle, which is found in crocodilians and some other archosaurs, the astragalus is fixed to the tibia by a suture, and the joint bends around a peg on the astragalus, which fits into a socket in the calcaneum.
The skull is composed of three types of bone: cranial bones, facial bones and ossicles, which is made up of a number of fused flat and irregular bones. The cranial bones are joined at firm fibrous junctions called sutures and contains many foramina, fossae, processes, and sinuses.
'sieve') is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due to a spongy construction. The ethmoid bone is one of the bones that make up the orbit of the eye.
The orbital septum is an important structure that separates anterior and posterior extent of the orbit. Orbital septum acts as a physical barrier that prevents the infection of the anterior part of the eye spreading posteriorly. For example, preseptal cellulitis mainly infects the eyelids, anterior to the orbital septum.
Ocular sutures – are sutures surrounding the edges of the compound eye. Trilobites with these sutures lose the entire surface of the eyes when molting. It is common among Cambrian trilobites. Palpebral sutures – are sutures which form part of the dorsal facial suture running along the top edges of the compound eye.
The pattern is different between the inside and the outside. [1] Two anatomical landmarks are found on the sagittal suture: the bregma, and the vertex of the skull. The bregma is formed by the intersection of the sagittal and coronal sutures. The vertex is the highest point on the skull and is often near the midpoint of the sagittal suture.