The Skull Flashcards
How many bones make up the skull?
22 bones joined by sutures (fibrous joints)
The brain can be split into two parts
Neurocranium: Bony case covering the brain, has a roof (Calvaria) and a floor/base (basicranium)
Viscerocranium: The facial skeleton
Bones forming the neurocranium
Parietal bones (paired)- sides/top of skull
Temporal bones (paired)
Occipital bone (unpaired) - back of skull
Frontal bone (unpaired)
Parts of sphenoid bone (unpaired)- helps to connect the neurocranium to the viscerocranium. It is a single bone in the midline of the cranial cavity situated posterior to the frontal bone but anterior to the occipital
Functions of the skull
Encloses and protects brain (bone of braincase: sphenoid, frontal, parietal)
Attachment of muscles (occipital bone and jaws)
Jaws for biting and chewing (mandible and maxilla)
Respiratory skeleton (ethmoid and palatal bones)
Protects ear (temporal or optic bones)
Protects eye (bones of orbit)
Frontal bone
Orbital plate of the frontal bone: forms the roof of the orbital cavity.
Glabella: the brow ridge that serves as an attachment point for the frontalis muscle and superior portion of the orbicularis oculi
Supraorbital notch: nerves supplying the forehead to emerge through this aperture
Parietal bones
join in the sagittal line to form the sagittal suture. They are each joined anteriorly to the frontal bone by the coronal suture.
Occipital bone
The occipital bone is joined superiorly to the parietal bones by the lambdoidal suture. It contains an external occipital protuberance that can be felt on the back of your head.
The foramen magnum, housing the brainstem, is also a part of the occipital bone. Either side of the foramen magnum are the hypoglossal canals for cranial nerve XII.
What are the 4 main parts of the temporal Bone
Squamous
Shaped like a fish scale (for which it is named)
Contributes to the temporal fossa
Petrous
Pyramid or wedge-shaped
Densest bone in the body
Contains the internal auditory meatus for cranial nerves VII and VIII
Tympanic
Curved plate below the squamous portion
Originates as a separate bone (the tympanic bone) which fuses with the temporal bone
Contains the external auditory meatus
Mastoid
Named after its breast-like appearance
Contains the mastoid and styloid processes
Bones of viscerocranium (facial skeleton)
Nasal (paired)
Lacrimal (paired)
Inferior nasal conchae (paired)
Vomer
Zygomatic (paired)
Maxilla (paired)
Palatine (paired)
Mandible
Ethmoid bone
separates the nasal cavity from the brain.
It forms part the perpendicular plate of the osseous nasal septum.
It also contains small foramen that allow the olfactory nerve to move from within the skull to the top of the nasal cavity to sample air particles. This part of the ethmoid bone is called the cribriform plate.
Features of ethmoid bone
Crista galli- attachment for the falx cerebri
Ethmoidal air cells- paranasal sinuses
Superior and middle nasal concha- extends into the nasal cavity
Perpendicular plate- forms the superior two thirds of the nasal septum
Cribriform plate- sieve like structures which allows the olfactory nerve fibres to pass
Zygomatic bone
From what are known as ‘cheek bones’ as they articulate with the temporal bones. When you palpate your cheek bones, you are palpating your ‘zygomatic arches’
Features of the sphenoid bone
Greater wings: form the floor of the middle cranial fossa for the temporal lobe to sit in
Sella turcica: the “Turkish chair” that contains the pituitary gland
Orbital surface: forming the posterior wall of the orbit
3 large depressions of the internal surface of the cranial base
Anterior cranial fossa- formed from frontal, ethmoid and sphenoid bones
Middle cranial fossa- formed of parts of the sphenoid and temporal bones
Posterior cranial fossa’- parts of the temporal and occipital bones
Sutures
Sutures are a form of fibrous joint that are found in the skull. Fuse completely by 20 years.
