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Skull and Facial Muscles - Anatomy & Physiology (view source)
Revision as of 12:27, 30 July 2008
, 12:27, 30 July 2008no edit summary
The viscerocranium is the pharyngeal skeleton. It is derived only from the neural crest and undergoes endochondral and intramembranous ossification.
The viscerocranium is the pharyngeal skeleton. It is derived only from the neural crest and undergoes endochondral and intramembranous ossification.
The shape and size of the skull varies widely, not only between species but also with age, breed and sex of similar species.
==Structure==
==Structure==
===Occipital Bone===
===Occipital Bone===
*
*Forms the nuchal wall
*Forms the foramen magnum
*Basilar part (pars basilaris)
**Caudal base of the cranium
**Rostral to foramen magnum
**Joined by cartilagenous suture to basisphenoid bone
**Muscular tubercules on ventral surface where the flexors of the head and neck attach
**Caudal cranial fossa enclose the pons and medulla oblongata
*Squamous part (pars squamosa)
**Dorsal to lateral parts and occipital condyles
**Nuchal crest present
***Easily palpable
***Landmark for collection of cerebrospinal fluid (CSF)
**External occipital protuberances present which provide muscle attachment sites for the nuchal ligament
*Lateral parts (partes laterales)
**Lateral borders of foramen magnum
**Occipital condyles present which articulate with the atlas to form the atlanto-occipital joint
**Paracondylar process present which provides muscle attachment sights for muscles of the head
**Hypoglossal canal
===Sphenoid Bone===
===Sphenoid Bone===
===Mandible===
===Mandible===
==Foramen==
*Jugular Foramen
**Located either side of basilar part of occipital bone
**Adjacent to tympanic bulla
*Foramen Magnum
**Formed by occipital bones
*Hypoglossal Canal
**Between paracondylar and condylar processes on lateral part of occipital bone
==Species Differences==
==Species Differences==
*2 halves of the mandible do not fuse allowing some movement
*2 halves of the mandible do not fuse allowing some movement
*External sagittal crest arises from nuchal crest
[[Image:Lion skull.jpg|thumb|right|150px|Feline skull (Lion) - Copyright RVC]]
[[Image:Lion skull.jpg|thumb|right|150px|Feline skull (Lion) - Copyright RVC]]
*2 halves of the mandible do not fuse allowing some movement
*2 halves of the mandible do not fuse allowing some movement
*Weak sagittal crest
*Weak external sagittal crest arises from nuchal crest
[[Image:Horse Skeleton.jpg|thumb|right|150px|Horse Skeleton - Copyright Nottingham]]
[[Image:Horse Skeleton.jpg|thumb|right|150px|Horse Skeleton - Copyright Nottingham]]
===Equine===
===Equine===
*Weak sagittal crest
*Weak external sagittal crest arises from nuchal crest
*Long skull length
*Long skull length
*[[Anatomy & Physiology of the Horn|Cornual]] process on frontal bone
*[[Anatomy & Physiology of the Horn|Cornual]] process on frontal bone
*Nuchal crest reduced to nuchal line
*Prominent temporal line
*Prominent temporal line