Anatomy Skull PDF

Anatomy Skull ‫ اﯾﻤﺎن ﻏﺎﻧﻢ‬.‫د‬ Objective of this lecture Skull and cranium  View = Norma of skull Norma frontalis Norma occipitalis Norma lateralis  Sutures of the Skull Sutures are a type of f...

Anatomy Skull ‫ اﯾﻤﺎن ﻏﺎﻧﻢ‬.‫د‬ Objective of this lecture Skull and cranium  View = Norma of skull Norma frontalis Norma occipitalis Norma lateralis  Sutures of the Skull Sutures are a type of fibrous joint that are unique to the skull. They are immovable and fuse completely around the age of 20. These joints represent points of potential weakness in the skull. The main sutures in the adult skull are: ✔ Coronal suture – fuses the frontal bone with the two parietal bones. ✔ Sagittal suture – fuses both parietal bones to each other. ✔ Lambdoid suture – fuses the occipital bone to the two parietal bones. In neonates, the incompletely fused suture joints give rise to membranous gaps between the bones, known as fontanelles. The two major fontanelles are: ❖ Frontal fontanelle ( bregma)– located at the junction of the coronal and sagittal sutures ❖ Occipital fontanelle ( lambda)– located at the junction of the sagittal and lambdoid sutures  Floor of the Skull The floor of the skull is divided into three cranial fossae: anterior, middle, and posterior. ✔ The anterior cranial fossa is separated from the middle cranial fossa by the lesser wing of the sphenoid, ✔ and the middlecranial fossa is separated from the posterior cranial fossa by the petrous part of the temporal bone. The anterior cranial fossa The floor of the fossa is formed by the orbital plates of the frontal bone laterally and by the cribriform plate of the ethmoid medially. The small perforations in cribriform plate are for the olfactory nerves. Stigmata The frontal crest The cribriform plate The crista galli The anterior clinoid process  Middle Cranial Fossa The sphenoid bone resembles a bat having a centrally placed body with greater and lesser wings that are out stretched on each side. The body of the sphenoid contains sphenoid air sinuses Stigmata ✔ sella turcica ✔ Optic canal A rounded foramen medial to the anterior clinoid process (Lesser wing of sphenoid) leads from the MCF to the orbit ✔ The superior orbital fisure (between the lesser and the greater wings) ✔ The foramen rotundum (situated behind the medial end of the superior orbital fisure ✔ The foramen ovale lies posterolateral to the foramen rotundum ✔ The small foramen spinosum lies posterolateral to the foramen ovale ✔ The large and irregularly shaped foramen lacerum between the apex of the petrous part of the temporal bone and the sphenoid bone ✔ The carotid canal opens into the side of the foramen lacerum.  Posterior Cranial Fossa Stigmata The internal occipital crest runs upward in the midline posteriorly from the foramen magnum to the internal occipital protuberance The foramen magnum occupies the central area of the floor and transmits the medulla oblongata The hypoglossal canal is situated above the anterolateral boundary of the foramen magnum The jugular foramen lies between the lower border of the petrous part of the temporal bone and the condylar part of the occipital bone The internal acoustic meatus pierces the posterior surface of the petrous part of the temporal bone  basalis externa )Inferior View If the mandible is discarded, 1- the anterior part of this aspect is formed by the hard palate(The palatal processes of the maxillae and horizontal plates of the palatine bones) In the midline anteriorly is the incisive foramina. Postero laterally are the greater and lesser palatine foramen 2- Above the posterior edge of the hard palate are the choanae (posterior nasal apertures seperated by vomer are bounded laterally by the medial and lateral pterygoid plates of temporal bone sphenoid 3-. Posterolateral to the lateral pterygoid plate, the greater wing of the sphenoid is pierced by the large foramen ovale and the small foramen spinosum 4- The mandibular fossa of the temporal bone 5-petrous part of the temporal bone , the carotid canal can be seen on the inferior surface of petrous bone. The medial end of the petrous part there is foramen lacerum 6-between the styloid and mastoid processes, stylomastoid foramen 7- jugular foramen ( between petrous and occipital ) 8- foramen magnum 9-occipital condyles 10-Superior to the occipital condyle is the hypoglossal canal