osteology, cranial fossa, meninges, sinuses & intracranial bleeds Flashcards
What are the 2 key parts of the skull?
- the neurocranium
- the** viscerocranium**
what bones does the **neurocranium **contain?
- 2** parietal** bones
- 2 **temporal **bones
- **occupital **bone
* sphenoid bone (behind eyes) - ethmoid bone (nose)
- frontal bone
what is the function of the neurocranium?
- to enclose and protect the brain, meninges,cerebral nerves and vessels
What is the neurocranium subdivided into (2 things)?
- cranial roof (calvarium)
- cranial base
what bones are present in the calvarium?
- 2 parietal bones
- frontal
- occipital
What bones are present in the cranial base?
(think of superior view of the skull)
- frontal
- ethmoid
- sphenoid
- occipital
- 2 temporal bones
What bones does the viscerocranium (facial skeleton) contain?
- 2 maxilla (upper jaw)
- 2 nasal bones
- 2 lacrimal bones
- 2 inferior nasal concha
- 2 palatine bones (near maxilla)
- 2 zygomatic bones (cheek bones)
- vomer
- mandible - connected to skull via TMJ
what is the Pterion?
- a H shaped junction ** where the temporal, frontal, pariteal and sphenoid bone join**
what can happen if the pterion region is fractured?
- can cause a epidural haemorrhage (bleeding in the brain between the dura mater and skull)
What are sutures?
- a type of immobile fibrous joint that is unique to the cranium
What are the different sutures of the skull?
*** coronal **(between frontal and parietal)
* sagittal (between the 2 parietal bones)
* lambdoid (occipital and parietal)
* squamosal (temporal and parietal)
What are the different cavities of the skull?
- **nasal **cavity
- **orbital **(eyes)
- **cranial **( for brain)
- paranasal sinuses
-
oral cavity
* middle and inner ear
what are the 3 terms for the ‘openings/ holes’ of the skull & what is their purpose/function?
- foramina
- canals
- fissures
function : for **passage of nerves and blood vessels **
what are the 4 main parts of the sphenoid bone?
ie the WASP bone - looks like wasp
- body
- greater wing
- lesser wing
- lateral pterygoid process
what is the clinoid process of the sphenoid bone and what is it attached to?
- attaches onto a reflecion of dura mater
- tentorium cerebelli
what important openings (fissures, foramina etc) does the sphenoid bone contain?
- superior orbital fissure
- optic canal
- foramen rotundum
- foramen ovale
- foramen spinosum
what bones does the sphenoid hone articulate with?
- neurocranium - frontal, parietal, temporal, ethmoid, occipital
- viscerocranium - palatie, vomer , zygomatic bone
What is the function of the ethmoid bone?
protects vital organs in this region and supports the nose and orbits
What are the parts of the ethmoid bone?
- the** perpendicular plate** (forms part of the nasal septum that separates the 2 nasal cavities)
- superior nasal concha &** middle nasal concha** - important for warming air
- crista gali - on each side of it - there are foramina (holes) which is called the **cribriform plate **
what does the crista galli of the ethmoid bone attach onto?
it attaches onto the dura mater
* the falx cerebri
what bones does the ethmoid bone articulate with?
- neurocranium - frontal & sphenoid bone
- viscerocranium - nasal bone, maxillae, lacrimals,vomer, palatines and inferior nasal concha
What are the different parts of the temporal bone & briefly what do they contain?
- **squamous part **- zygomatic process & TMJ surface
* tympanic part- houses middle ear cavity & chain of 3 auditory ossicles (malleus, incus and stapes) - petrous part -houses inner ear cavity
- mastoid process- anchoring point for neck muscles and ligaments
what bones does the temporal bone articulate with?
- sphenoid
- parietal
- occipital
- zygomatic
- mandible (note only one viscerocranial bone)
what muscle does the external occipital protuberance attach to?
the trapezius muscle
How many cranial nerves are there?
- 24
- 12 PAIRED nerves
what is the function of cranial nerves?
- sensory and motor innervation to structures of head & neck
What are the 12 pairs of cranial nerves
Oh Oh Oh Tiny Tits Are Fun And Give Virgins Awkward Hips
- Olfactory nerve
- Optic
- Oculomotor (eyelid/ pupil movement)
- Trochlear (eye movement)
- Trigeminal (sensation to maxialle, mandible region)
- Abducens (eye movement)
- Facial (motor to muscles of facial expression)
- Vestibulocochlear (hearing and balance)
- Glossopharyngeal (special sensations)
- Vagus (throat, throax & abdomen)
- Accessory
- Hypoglossal (motor to tongue - speech and swallowing)
what artery is behind the pterion & why is this clinically important?
-branch of the middle meningeal artery - runs just underneath
-extradural haematoma can happen as a result of a skull fracture in this area
what is the bregma?
junction between the junction between the frontal and parietal bone in the midline
what is the lambda?
junction between the parietal and occipital bone in the midline
what are the 3 cranial fossa?
-anterior
-middle
-posterior
what bones make up the posterior cranial fossa?
-temporal bone (petrous part)
-occipital bone
-foramina - internal acoustic meatus, magnum, jugular & hypoglossal
what bones make up the anterior cranial fossa?
-frontal
-ethmoid - crista galli, cribiform plate
-lesser wing of sphenoid bone
what bones make up the middle cranial fossa?
-body, greater wings, sella turcica, foramen (rotundum, ovale, spinosum)
-petrous and squamous part of temporal bone
what are the 3 meninges?
-dura mater
-arachnoid mater
-pia mater
what is the function of the meninges?
-protect the brain and spinal cord from mechanical trauma,
- to support the blood vessels
-form a continuous cavity through which the cerebrospinal fluid (CSF) passes
which 2 layers does the CSF pass through and what is the name for these 2 layers together?
-between the Pia and arachnoid mater which together are called the leptomeninges
what are the 2 layers of the dura?
-periosteal layer
-meningeal layer
what is the subdural space?
space between the dura and arachnoid layers
what is the subarachnoid space?
space between the arachnoid and the Pia mater
what are the meninges of the spinal cord?
-dura (note no real subdural space)
-arachnoid mater
-pia mater
what is the falx cerebri?
-strong crescent-shaped sheet that represents an invagination of the meningeal layer of the dura mater into the longitudinal fissure
-attached to the crista Galli and the internal occipital protuberance
what structures lie between the 2 layers of the cranial dura?
venous sinuses
what is the tentorium cerebelli?
-invagination of the meningeal layer of the dura mater that separates the occipital and temporal lobes of the cerebral hemispheres from the cerebellum and brainstem
-attached onto the clinoid process of the sphenoid bone
what are dural venous sinuses ?
-major vascular channels contained between the meningeal and periosteal layers of the dura mater.
-includes the superior sagittal sinus, inferior sagittal sinus, straight sinus, transverse sinus, sigmoid sinus and superior petrosal sinus.
what is the cavernous sinus?
-part of the brains dural venous system that sits on either side of the body of the sphenoid (middle cranial fossa)
-has a close relationship with lots of important structures in the head
what important vessels and nerves travel through the cavernous sinus?
-internal carotid artery
-abducens nerve
-oculomotor nerve
-trochlear nerve
- ophthalmic nerve (V1)
-maxillary nerve (V2)
why are the arachnoid granulations important & where are the largest ones located?
-tufts of arachnoid membrane invaginated into the dural sinuses through which cerebrospinal fluid (CSF) enters the venous system.
-largest ones along the superior sagittal sinus
what is meningitis?
inflammation of the pia mater
what is an extradural haemorrhage and what would cause it?
-bleeding in the extra dural space (between dura mater and the skull)
-caused by skull fracture that tears arterial vessels in the extradural space eg middle meningeal artery
what is a subdural haemorrhage?
a bleed between the dura and the arachnoid mater
what is a subarachnoid haemorrhage and what are examples of symptoms?
-bleed in the subarachnoid space
-symptoms : sudden onset headache, nausea or vomiting etc
what shapes would a subdural vs epidural/extradural haemorrhage have?
-subdural - crescent
-epidural/extradural - lemon shape
what is brain herniation?
-brain herniation occurs when there is an increased cranial pressure causing the brain to be pushed sideways & downwards through small openings in the tissue that divide the brain up
what is an uncus herniation?
-herniation of the uncut (part of limbic system of brain)
-presses on CN III - esp the parasympathetic fibres
-causes a sluggish light reflex (ie pupils dont respond properly to light)
what is cerebellar tonsil herniation?
-the cerebellar tonsil can be pushed into the foramen magnum - pressing on the medulla & causing abnormal cardioresp centre
-eg BP rises, pulses fall, hyperventilation, cheyne stokes respiration
what is cheyne stokes respiration?
-abnormal pattern of breathing - progressively deeper & faster breathing and followed by a temporary stop in breathing called apnoea
what is an example of a cause & possible presentation of a patient with a subdural bleeding?
-cause: cerebral atrophy with stretched cerebral veins (minimal trauma needed to tear these)
-eg presentnaion - elderly patient w/ fall but no direct blow - gradual increase in confusion
what is an example of a cause of a sub-arachnoid bleeding and how would a patient present?
-example of cause: ruptured berry aneurysm on circle of willis
-presentation- sudden severe headache
