Skull and cranial cavity Flashcards
State the vascular layers of the SCALP
Also give its innveration
Skin Connective tissue Aponeurotic layer Loose connective tissue Pericranium
Innervated by the trigeminal nerve and spinal cutaneous nerves
State the foramina of the brain and what passes through
Cribriform plate- olfactory nerve (CN1)
Optic canal- ophthalmic artery, optic nerve (CN2)
Superior orbital fissure- superior ophthalmic vein, ophthalmic nerve (CN3), trochlear nerve (CN4), Lacrimal, frontal and nasociliary branches of ophthalmic nerve (CNV1), abducent nerve (CN6)
Foramen rotundum- Maxillary nerve (CNV2)
Foramen ovale- Mandibular nerve (CNV3)
Foramen spinsum- MMA
Internal acoustic meatus- facial nerve (CN7), vestibulocochlear nerve (CN8)
Stylomastoid foramen- Stylomastois artery
Foramen lacerum- Internal carotid artery
Foramen jugular- IJV, Glossopharyngeal (CN9), Vagus (CN10), Accessory (CN11)
Hypoglossal canal- Hypoglossal nerve (CN12)
Foramen magnum- Vertebral arteries, Medulla and meninges, Accessory nerve (spinal division), Dural veins
Anterior and posterior spinal arteries
What is the function of the the meninges? What are its layers?
Pia mater + Arachnoid mater + dura mater
The dura mater is an endosteal layer, meaning it lines skull and meninges cover spinal cord (including roots)
Protection
Support network for blood vessels
Form a fluid filled cavity (subarachnoid space) to cushion and nourish the brain, the brain has to float to prevent crushing
State the innervation and blood supply of the meninges
INNERVATION
Cranial nerves 5, 10
Spinal nerver C1-C3
And sympathetic innervation
Middle meningeal artery
How are the dura mater is arranged?
In folds (septa) which divide cranial cavity and prevent/restrict brain movement
Falx cerebri (crescent shaped)- seperates cerebral hemispheres, attaches anteriorly to crista galli of ethmoid bone and frontal crest of frontal bone. Posteriorly, attaches to tentorium cerebelli.
Tentorium cereblli (horizontal projections)- seperates cerebellar hemispheres from posterior cerebeal hemispheres.
Falx cerebelli (small midline projection)- seperates cerebellar hemispheres
Subdural space is a POTENTIAL space, only filled pathologically.
Cite three clinical applications of dura mater
- Dura sensitive to stretch- anatomical basis of headache
- Damage to MMA= extradural haematoma
- Tentorial herniation= space occupying lesion causes herniation of temporal lobe
Describe the appearance and function of the arachnoid mater
Thin, avascular
Loosely applies layer with projections
All structures passing to/from brain enter subarachnoid space. Its function is to provide buoyancy to brain, protecting it from mechanical force (e.g. blow).Subarachnoid space contains CSF produced by choroid plexus in brain ventricles.
Arachnoid granulations look like alveolar sacs and affect the transfer of CSF to venous sinuses. (CSF to venous sinuses to kidney –> excretion)
500ml of CSF is made/day
Describe the appearance and function of the pia mater
Delicate, vascular membrane
Closely follows gyri/sulci
Cerebral arteries enter brain carrying sheath of pia mater
What is Leptomeningitis?
An infection and inflammation in the leptomeninges (pia and arachnoid). If it enters subarachnoid space ==> blood stream ==> septicaemia
Outline the location, function and structure of he dural sinuses
Location- between the dural fold
Function- drain blood and CSF from brain via cerebral veins; communicate with veins of the skull and scalp
Structure- thick walled endothelium (IJV), no smooth muscle or valves
Without describing the circle of willis, describe the entry of blood into the brain
Vertebral artery (posterior)- passes through cervical vertebrae –> foramen magnum –> unite to form basilar artery
Common carotid artery (anterior) which divides into the internal and external branches.
Internal carotid artery branches anastomose to form Circle of Willis
Inside the skull= two terminal branches
- The anterior cerebral artery
- Middle cerebral artery
Outline the Circle of Willis
Anterior cerebral artery Anterior communicating artery Middle cerebral artery - Internal carotid artery Posterior communicating artery Posterior cerebral artery Superior cerebellar artery Basilar artery Anterior inferior cerebellar artery Vertebral artery
Consider the cerebral artery, state what each part supplies.
Anterior- supplies medial and superior surfaces of brain and frontal lobe
Middle- supplies lateral surfaces of brain and temporal pole
Posterior- supplies inferior surfaces and occipital pole
Briefly describe what happens in a stroke
Stroke: caused by an embolism in a cerebral artery, no anastomosis of cerebral arteries once inside brain hence neurological deficit
Pressure from ICA and vertebral artery is same, no mixing in posterior communicating artery unless if ICA or vertebral artery occluded - blood passes back / forth across PCA to compensate for reduced blood flow
