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Growth of the Cranial Base HHiH
Published in D. Dixon Andrew, A.N. Hoyte David, Ronning Olli, Fundamentals of Craniofacial Growth, 2017
The cranial base is derived from the primitive chondrocranium (De Beer, 1937), and comprises the midline bones and the cranial fossae — anterior, middle and posterior — which in large part also originate in the chondrocranium, with additions, in certain bones, ossifying in membrane. The midline bones are the basioccipital, sphenoid — comprising at various stages in different animals and man a basisphenoid (or postsphenoid) and a presphenoid — and the ethmoid at the junction of base and face. The anterior cranial fossa is roofed-in in front by the frontal bone, whose orbital plates form most of the floor of the fossa, meeting the cribriform plate of the ethmoid in the midline, and the lesser wings of the sphenoid behind. The sphenoid bone could be said to be the linch-pin of the middle fossa, with its greater wing extending laterally to floor the fossa, anteriorly to wall in the orbit posterolaterally, and further laterally to share with the squamosal the wall of the temporal fossa. Separating the middle from the posterior fossa is the obliquely lying petrous part of the temporal bone (see Chapter 12). The parts of the occipital bone derived from the chondrocranium complete the floor and walls of the posterior fossa, surrounding the foramen magnum — the basioccipital, here forming with the posterior aspect of the sphenoid bone the clivus, the exoccipitals, and the supraoccipital. The membranous interparietal bone which joins with supraoccipital to form the occipital squama belongs more properly to the skull vault, and will not be considered here.
Head and Neck
Published in Rui Diogo, Drew M. Noden, Christopher M. Smith, Julia Molnar, Julia C. Boughner, Claudia Barrocas, Joana Bruno, Understanding Human Anatomy and Pathology, 2018
Rui Diogo, Drew M. Noden, Christopher M. Smith, Julia Molnar, Julia C. Boughner, Claudia Barrocas, Joana Bruno
As will be discussed in detail in Chapter 6, all somites look similar, yet the vertebrae that they form have unique shapes in each part of the body. The first four true somites do not form vertebrae at all; they form the occipital bone. These somites initially look like all the others, but their sclerotomes (a division of the somite that also forms vertebrae) all fuse together to form a single elongated body, the basioccipital, around the notochord. Lateral and dorsal parts of the occipital cartilage are also formed by fusion of adjacent sclerotomes and all the parts of the occipital cartilage undergo endochondral ossification to form the occipital bone. Instead of articular facets, the caudal surface of the occipital bone has large, convex occipital condyles. The articulation between the occipital condyles and the 1st cervical vertebra, called the atlas (described in the next paragraph), restricts movement to extension/flexion (i.e., this is the “yes” joint) (see also Section 6.1 for descriptions of form, function, and development of vertebrae). The adult occipital bone forms much of the back and base of the skull. In addition to the occipital condyle, it has a protuberance called the pharyngeal tubercle to which the pharyngeal raphe attaches. Openings in the occipital bone include the foramen magnum (the “big hole” through which pass the medulla oblongata, spinal roots of accessory nerve (CN XI), and vertebral arteries), and the paired hypoglossal canals for the passage of the hypoglossal nerve (CN XII) (Plate 3.11).
Developmental Anatomy of the Pituitary Fossa
Published in John C Watkinson, Raymond W Clarke, Louise Jayne Clark, Adam J Donne, R James A England, Hisham M Mehanna, Gerald William McGarry, Sean Carrie, Basic Sciences Endocrine Surgery Rhinology, 2018
The bony landmarks around the fossa are as follows (Figure 54.6): The optic canal lies between the roots of the lesser wing and the body of the sphenoid medially. It descends slightly anterolaterally, and it contains the optic nerve, ophthalmic artery and meninges.The anterior clinoid process is the posterior projection from the lesser wing of the sphenoid.The tuberculum sellae is a midline ridge in the anterior slope of the sella turcica.The dorsum sellae is the posterior wall of the sella turcica. The superolateral projections of the dorsum form the posterior clinoid processes.The groove for the internal carotid artery is formed as the artery turns anteriorly from the foramen lacerum. The groove can be seen on the sphenoid lateral to the sella turcica.The middle clinoid process is a small elevation in the median edge of the groove. In approximately 10% of skulls the middle and anterior clinoid processes are joined to form a continuous ring called the carotico-clinoid foramen.10The lingula is a small projection arising on the posterolateral aspect of the carotid groove.The clivus is made up of the body of the sphenoid bone behind the dorsum sellae and the basioccipital bone. The upper part of the pons lies adjacent to the clivus. In approximately 2% of skulls there is a bony bridge joining the anterior clinoid and posterior clinoid processes called the tinea interclinoidea. In approximately 1% of skulls there is a bony projection in the floor of the sella called the sella spine. It is a bony spicule that projects from the junction of the anterior and inferior walls of the sella towards the middle of the hypophyseal fossa and it is usually 1 mm in diameter and 2–5 mm in length. It probably represents an ossified remnant of the notochord.11
Canalis basalis medianus with cerebrospinal fluid leak: rare presentation and literature review
Published in British Journal of Neurosurgery, 2019
Sami Khairy, Abdulaziz Oqalaa Almubarak, Ahmed Aloraidi, Khalid Omar Awad Alahmadi
Canalis Basalis Medianus (CBM) is a rare congenital anatomically variant of the clivus. It is a midline canal of the basioccoiput anterior to foramen magnum without established clinical significance. It was first described by Gurber 1880 in dry skulls.1 The anomaly lies on the intracranial surface of the clivus, particularly on its basioccipital portion, anterior to foramen magnum. CBM is classified into either complete or incomplete types.1