![]() ![]() The temporal bone forms a bony ridge called the petrous temporal bone that contains the middle and inner ears inside it. The body contains two important anatomical features: (1) a shallow depression anteriorly, called the suprachiasmatic sulcus that hosts the optic chiasma, and (2) a larger deeper depression posteriorly, called the sella turcica that hosts the pituitary gland inside it and is covered over by the diaphragma sellae. It has a butterfly-like appearance where the central part is formed by the body of sphenoid bone. The middle cranial fossa is formed mainly by the sphenoid bone and the temporal bones and houses the temporal lobes of the brain inside it. The cribriform plate forms the roof of nasal cavity and allows olfactory neurons to pass through it to enter the olfactory bulb situated immediately above. The orbital plates of frontal bone contribute to the roof of orbital cavity and have frontal lobes of the brain resting on top of them. The anterior cranial fossa is formed by the orbital parts of frontal bones, cribriform plate of ethmoid bone and lesser wing of sphenoid bone. The floor is sub-divided into three sub-regions, including the anterior, middle and posterior cranial fossae. The skull base comprises of bones that form the floor of the cranial cavity. Some important features which can be seen on the inner surface of the calvaria include a midline longitudinal groove that marks the position of superior sagittal sinus, and some bony pits on either side of midline which mark the position of arachnoid villi and granulations. The point of intersection of coronal and sagittal sutures is called bregma, while the intersection-point between sagittal and lambdoid suture is called lambda. A sagittal suture can be seen in the midline where the two parietal bones meet with each other and a side-to-side lambdoid suture delineates the articulation of the two parietal bones with the occipital bone. For instance, a coronal suture marks the union of frontal with two parietal bones. It comprises mainly of frontal, parietal and occipital bones, which articulate with each other to form various sutures. The calvaria is the skull cap or the dome-shaped roof of the cranial cavity. The cranial cavity (or neurocranium) further comprises of two sub-parts, which are the calvaria and the skull base: Please note that the remaining bones which contribute to the facial skeleton, form the viscerocranium (or the viscerocranial part of head). ![]() neurocranium or the neurocranial part of head). Of those which encapsulate the brain, constitute the cranial cavity (a.k.a. The bones of the skull are called the ‘cranium’. ![]()
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