General introduction and the skull and foramina Flashcards
How many bones are there in the skull?
22
What makes up the neocranium?
Frontal, 2 parietal, 2 temporal, occipital, ethmoid, sphenoid
What makes up the facial skeleton?
2 Maxilla, mandible, nasal, 2 lacrimal, vomer, 2 inferior nasal concha, 2 palatine, 2 zygomatic
Which bone has a petrous and squamous surface?
Temporal bone
What key features are there on the sphenoid bone?
Has lateral and medial pterygoid plates on either side, greater and lesser wings, sella turcica (where the pituitary gland sits), Has the foramen ovale, rotundum and spinosum all in the greater wing, as well as the superior orbital fissure and optic canal.
What are the 4 main sutures in the skull? And how do they fuse and at what age?
Sagittal suture - Between the two parietal bones
Coronal suture - Between the frontal and parietal bones
Lamda suture - Between the parietal and occipital bones
Squamous suture - Between the parietal and temporal bones
The bones interdigitate through Sharpy’s fibres and normally fuse at 2 years old.
What is the purpose of sutures and how may they differ in newborns?
Sutures allow growth and movement in the cranium. Newborns have fontanelles (soft spots) where the bones have not fused normally a frontal and occipital fontanelle.
What is a pterion?
The pterion is located just posterior to the temple, where it is the weakest point and where the sutures join together, the middle meningeal artery passes here and a blow to the head here is fatal.
What small bones are housed inside the temporal bone? And are sometimes added to the 22 bones of the skull.
The little ossicles in the ear
What is the significance of a frontal suture?
They are not meant to be there, but frontal sutures are mostly seen in children and normally fuse up. However a metopic suture (persistent), may carry on into adulthood. They show no clinical significance however are often mistaken for fractures in which they would not be so regular and straight.
What is craniostenosis?
It is premature fusion of the sutures which cause high intracranial pressure in children and babies.
What are the four main differences between the male and female skulls?
Glabella (between eyebrows) - more angles in males
Mastoid - males have a larger mastoid
Gonial angle (mandibular angle) - protrudes laterally in males
Occipital protuberance - More prominent in males
Orbital margin - sharper in females, rounded in males
Major foramina of the skull?
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Cribriform plate, optic canal , superior orbital margin, rotundum, ovale, lacerum, spinosum, internal acoustic meatus, jugular, hypoglossal, foramen magnum
What’s different about foreman lacerum?
It is filled with cartilage after birth and has no structures running through it
What foramina are located on the facial bones of the skull?
Supraorbital and infraorbital foramina. zygomaticofacial foramina, mental formaina
