cranium, meninges and brain Flashcards
bones of cranium
frontal two parietal two temporal occipital sphenoid (deep in centre) and ethmoid (above nose)
bones of facial skeleton
2 maxilla 2 zygoma (bones of cheek) 2 nasal 2 lacrimal 2 palatine (palate) 2 inferior nasal conchae (increase SA of nasal cavity to warm air)
vomer (middle of skull) mandible (jaw bone)
anterior view of skull DIAGRAM
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posterior part of skull DIAGRAM
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what are sutures
fibrous joints allowing little movement
infant skull + fontanelles DIAGRAM
anterior fontanelles close within 18 months, posterior within 2 months- thus sutures not complete as bones need to move as baby comes out of mother)
superior view of skull DIAGRAM
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pterion and clinical significance DIAGRAM
weakest region where greater wing of sphenoid, frontal, parietal and temporal bones join damage can rupture middle meningeal artery= extradural haematoma
cranial base and anterior cranial fossae DIAGRAM (bones, lobes and foramina)
can be divided into anterior, middle and posterior fossae anterior fossae is above nasal fossae, containing sphenoid, cribriform plate, foramen cecum, foramina of cribiform plate and frontal lobes
middle cranial fossae DIAGRAM
above pharynx, containing foramen lacerum, foramen ovale, foramen spinosum, foramen rotundum, greater wing of sphenoid, optic canal, superior orbital fissure, carotid canal and temporal lobes
posterior cranial fossae DIAGRAM
largest fossa containing brainstem and cerebellum, NOT occipital lobes, foramen magnum, jugular foramen, internal acoustic meatus and hypogloassal canal
foramina and nerve fibres that pass through
1- cribiform plate 2 (and opthalmic artery)- optical canal 3, 4, 5 (opthalmic nerve, 1st branch of trigeminal nerve),6 (and superior opthalmic vein)- superior orbital fissure 5 (maxillary nerve, 2nd part of trigeminal nerve)- foramen rotundum 5 (mandibular nerve, 1st part of foramen ovale)- foramen ovale middle meningeal artery+ vein- foramen spinosum internal carotid artery- carotid canal 7,8 (and labrynthine artery)- internal acoustic meatus 9, 10, 11 (and internal jugular vein)- jugular foramen 12- hypoglossal canal medulla, vertebral artery and spinal roots of 11th nerve- foramen magnum
tissue components of scalp and significance of blood supply
SCALP S- skin C- connective tissue A- aponeurosis L- loose areolar tissue P- periosteum: emissary veins can cause infection
meninges and layers of dura mater
tough dura matter, thin arachnoid mater and thin pia (attached to brain) dura mater has outer periosteal and inner meningeal layer, which separate to form intradural venous sinuses
periosteal layer lost as it fuses with skull at foramen magnum, so only inner layer goes down vertebral column
dural folds and sinuses DIAGRAM
dura mater follows shape of brain, so forms folds falx cerebri (ie cerebrum)fold- separates cerebral hemispheres tentorium cerebelli (sounds like cerebellum)- separates occipital lobes and cerebellum/brainstem
venous sinus is depression of inner layer- depression which forms falx cerebelli forms superior sagittal sinus: sinus penetrates arachnoid mater to allow CSF to be reabsorbed
transverse sinus along tentorium cerebelli, cavernous sinus are between temporal bones and sella turcica
brain herniation- what is it
increased pressure of brain due to a SPACE OCCUPYING LESION eg bleeding
causes parts of brain to shift beyond dural folds and compressing another region
subfalcine herniation DIAGRAM
frontal lobes herniate under flax cerebri- no clinical signifcance
uncal herniation
uncus of temporal lobe herniates below tentorium cerebelli, compressing midbrain/brainstem= loss of conciousness
tonsillar herniation
cerebellar tonsils move down through foramen magnum to compress medulla
CSF formation and drainage
choroid plexus in each ventricle produces CSF laterals drain into 3rd via interventricular foramina, then 4th via cerebral aqueduct, then subarachnoid space, the dural venous sinuses via arachnoid villi
blood supply of brain+ anterior supply DIAGRAM
2 types- anterior (internal carotid) and posterior (vertebro basilar) common carotid splits into internal/external at C4, and internal enters cranium via carotid canal, and has NOT branched yet then divides into anterior cerebral (supplies medial surface of hemispheres and superior part of lateral) and middle cerebral artery (main branch going through transverse fissure to supply lateral part)
posterior blood supply
vertebral arteries from subclavian arteries go through transverse foramina of cervical verebra, and divide to form anterior and posterior spinal arteries then unites to form basilar artery, which lies on pons- basilar divides into pontine arteries and posterior cerebral arteries
circle of willis DIAGRAM
connects anterior and posterior blood supplies- anterior cerebral arteries connected by anterior communicting, and middle and posterior connected by posterior communicating artery
venous drainage
cerebral veins first drain into dural venous sinuses- superior and inferior sinuses meet at confluence of sinus THEN internal jugular vein
