Endocrine Glands And Cranial Base Flashcards
What is the ossification of the Neurocranium?
Skull cap and skull base
Chondrocranium (cranial base) = endochondral ossification
Membranous neurocranium = intramembranous ossification
What bones make up the skull base?
Ethmoid, sphenoid, occipital, paired frontal, paired temporal
What are bones anterior to the sella turcica derived from (of the skull base)?
Bones anterior to sella turcica are derived from neural crest cells
What are bones behind/posterior to the sella turcica derived from (of the skull base)?
Bones behind the sella turcica are derived from paraxial mesoderm
How is the anterior pituitary gland developed embryonically?
Diverticulum develops from the embryonic buccal cabvity. It has finger-like projections going upwards, lodging itself around the bones of the Chondrocranium as they form around it. This Rathke’s pouch becomes the anterior pit gland.
How is the posterior pituitary gland developed embryonically?
Finger-like downward projection from the diencephalon. This becomes the posterior pit gland.
How do the anterior and posterior parts form the pituitary gland?
When both upward and downward projections meet, they come together at around the level of the 3rd ventricle, forming the pituitary gland.
What bones are found in each cranial fossa?
Anterior - upper surface of ethmoid bones, orbital plate of frontal bone, lesser wings of sphenoid
Middle - sphenoid, temporal
Posterior - occipital
Main features of ethmoid bone
Cribiform plate where olfactory nerves come through
Crista galli, a continuation of the perpendicular plate and attachment for falx cerebri
Ethmoidal air cells, collecting to form the ethmoidal bulla
What can happen when the ethmoid bone fractures?
Tearing of the meninges from the crista galli
Anosmia
CSF rhinorrhoea - leaking through the subarachnoid space through the nose.
How do you diagnose CSF rhinorrhoea?
If product is collected it forms a chromatographic separation of blood and CSF.
Main features of the sphenoid
Body
Greater and lesser wings
Pterygoid processes downwardly projecting
Dorsum sellae
Posterior and anterior clinoid processes - important for attachment of meninges
Sella turcica holding pituitary gland in hypophyseal fossa by the meninges
What does the diaphragma sellae allow?
The attachment of the meninges around the sphenoid body seals off the area to allow the pituitary gland to sit in place through the diaphragma sella. There is a puncture in the membrane allowing pituitary stock to emerge through that.
Main features of temporal
Petrous part (seen from inside), squamous part, mastoid part, tympanic part (opening into external auditory meatus), styloid process, zygomatic process, internal acoustic meatus
Where do the meninges attach to the temporal bone?
Petrous part
What are fissures usually filled with?
Soft tissues
Only demonstrable in dry bones
Key fissures of the skull base
Petrosphenoidal fissure
Petrooccipital fissure
Key sutures of the skull base
Sphenosquamous suture
Occipitomastoid sutures
What is the outer part of the foramen lacerum covered by?
A cartilaginous plate
How does the foramen lacerum relate to the carotid canal?
ICA enters region of the cavernous sinus through the petrous temporal bone through the carotid canal, and exits via the foramen lacerum.
What does the ICA bring with it through the foramen lacerum and carotid canal?
Sympathetic fibres ride on the ICA and use it as a sympathetic drive to the head. Comes in as a blood vessels carrying sympathetic nerves, which come together to form the deep petrosal nerve.
Describe how fibres from the pterygopalatine ganglion become the greater petrosal nerve
Pterygopalatine ganglion receives preganglionic parasympathetic fibres from the greater petrosal nerve, starting from the brain and passing without terminating through the geniculate ganglion. Fibres eventually become the greater petrosal nerve - parasympathetic fibres which terminate in the pterygopalatine fossa.
How does the vidian nerve form?
Nerve of vidian canal/pterygoid canal
Forms by the confluence of the greater petrosal nerve and the deep petrosal nerve
What is the main point of weakness of the cranial base?
Line from the pterygopalatine fossa all the way to the jugular foramen. High energy image causes damage to the cranial base here.
