Unit 6: External Brain Flashcards
How are the bones of the skull formed and joined?
Formed by intramembranous ossification
Joined by sutures (a fibrous joint)
What is the cranium?
The superior aspect of the skull.
Protects the meninges, brain and cerebral vasculature
Split into the cranial roof and the cranial base
What makes up the cranial roof?
The frontal, occipital and two parietal bones.
Also known as the valvarium
What is the cranial base?
The frontal, sphenoid, ethmoid, occpital, parietal and temporal bones.
Articulate with C1, facial bones and mandible.
What are of the skull is particularly dangerous for cranial fractures?
The pterion
A H-shaped junction between the temporal, parietal, frontal and sphenoid bones.
Overlies the middle meningeal aretery, a fracture could damage the artery causing an axtradural haematoma
What is the facial skeleton?
12 bones that support the soft tissue of the face.
Lacrimal (2)
Nasal (2)
Inferior nasal conche (2)
Palatine (2)
Maxilla
Vomer
mandible
Also known as the viscerocranium
What is the joint between the mandible and the cranium called?
Temporomandibular joint
What is the strength of cranial sutures like?
Sutures are immovable, become more fused with age, fusing completely around the age of 20.
Despite there srtength they are still sites of potential weakness within the skull.
What are the different cranial suture?
Coronal suture - fuses frontal bone with parietal bones
Sagittal suture - fuses parietal bones together
Lambdoid suture - fuses occipital bones to parietal bones.
What are fontanelle in the skull?
Found in neonates
Areas of weakness where the suture have not yet fused together
Membranous gaps
Frontal fontanelle
Occipital fontanelle
Hows does the brains oxygen demand compare to other structures?
Very high oxygen demand
Very sensitive to oxygen deprivation, ischemic cell death within minutes.
What are the two main arteries responsible for supplying the brain?
The vertebral arteries - posterior circulation
The internal carotid arteries - anterior circulation
What vessels supply the pons, medullar and brains stem?
Branches of the vertebral arteries - pontine arteries from the basilar artery.
Explain the origin of the internal carotid arteries.
Common carotid arteries travel within the carotid sheath.
At C4 level the common carotid artery bifurcates into the internal and external carotid artery.
Enters the brain via the carotid canal of the temporal bone
Pass anteriorly to the cavernous sinus, distally give off branches then continue as the middle cerebral artery.
What are the different branches of the internal carotid arteries?
Ophthalmic artery
Posterior communicating artery
Anterior choroidal artery
Anterior cerebral artery.
(OPAA)
What does the ophthalmic artery supply?
The structures of the orbit (eye socket)
What does the posterior communicating artery supply?
Is an anastomotic connecting vessel in the circle of willis
What does the anterior choroidal artery supply?
Structures in the brain important for motor control and vision
What does the anterior cerebral artery supply?
Parts of the cerebrum
Describe the origin of the vertebral arteries?
Division of the subclavian arteries, travel up the posterior aspect of the neck through the formen transversarium.
Enter the cranail cavity through the foramen magnum.
Give off branches then continue as the basilar artery, which also branches then terminates by bifurcating into the posterior cerebral arteries.
What are the branches of the vertebral arteries before they become the basillar artery?
Meningeal branch - supplies the falx cerebelli
Anterior and posterior spinal arteries - supply the full length of the spinal cord
Posterior inferior cerebellar artery - supplies the posterior lobe of the cerebellum.
What does the basilar artery supply?
Travel up the ventral brain stem, branches supply the cerebellum and the pons.
What is the circle of willis?
Why is it important?
where is it found?
Anastamoses of the terminal branches of the vertebral and internal carotid arteries.
Safeguard to stroke by allowing multiple routes of blood supply to the brain
Found just anterior to the brain stem and inferior to the cerebrum
What are the differenct vessels that make up the circle of willis?
Main paired vessels
- anterior cerebral arteries
- internal carotid arteries
-posterior cerebral arteries
Paired support vessels
- anterior communicating artery
-posterior communicating artery
Draw a diagram to represent the circle of willis.
Label the blood vessels involved.
Yellow is the circle
internal carotids then travel out of the page toward us.
What regions of the brain do the different cerebral arteries supply?
Anterior cerebral artery - anteromedial cerebrum
Middle cerebral artery - lateral cerebrum
Posterior cerebral arteries - posterior cerebellul and inferior lateral edge.
What arteries supply the spinal cord?
Three longitudinal arteries:
1. Anterior spinal atery - branch of vertebral, travels in anterior median fissure, give rise to sulcal arteries which enter the spinal cord
2 +3 posterior spinal arteries - orignate from vertebral artery or the posterioinferior cerebellar artery, anastamose in the pia mater.
How does blood supply to the spinal cord change inferior the cervical level?
Supply from the three longitudinal arteries is insufficient.
Support from anastomoses of the segmental medullary and radicular arteries
Give an overview of segmental medullary arteries.
Anterior and posterior segmental medullar arteries
Dervied from spinal branches of arteies entering the spinal canal through the intervertebral foramina
What is the great anterior segmental artery of adamkiewicz?
Reinforces blood circulation to the inferior 2/3 of the spinal cord, found on the left in most individuals.
Give an overview of radicular arteries?
Supply and follow the paths of anterior and posterior nerve roots
May also help supply the spinal cord.
What is an embolism?
An obstruction of a blood vessels by an embolus formed elsewhere in the circulatory system.
Moves through the circulatory system until it blocks a vessel that is too small for it to pass through.
What is the cribriform plate?
Structure of the ethnoid
Acts a bit llike a siv (many small holes)
Transmits the olfactory nerve CN1
What are the different formania of the sphenoid bone?
Form nose to occipital:
-optic canal
-Superior orbital fissue
-foraman rotandum
-forman ovale
What is the function of the optic canal?
Is one of the formanin a in the sphenoid bone
Transmits the optic nerve CN2
What is the superior orbital fissure?
One of the formaninia in the sphenoid bone
Transmits the oculomotor nerve CN3,
Trochlear nerve CN4, Ophthalmic branch of trigeminal nerve CN5 and the abducens nerve CN6
What is formen rotundum?
One of the formanina of the sphenoid bone
Transmits the maxillary branch of the trigeminal nerve CN5
What is the formen ovale?
One of the foramina of the sphenoid bone
Transmits the mandibular branch of the trigeminal nerve CN V3
What is the internal acoustic meatus?
Structure in the temporal bone for the passage of the facial nerve CNVII and the vestibulocochlear nerve CNVIII out of the cranium.
What is the stylomastoid foramen?
Where the facial nerve is transmitted out of the cranium
part of the temporal bone
Links up to the internal acoustic meatus
What is the jugular foramen?
Sits between the temporal and occipital bone inferiorly
Transmits the Glassopharahgnea; nerve CN9, vagus nerve CN10 and accessory nerve CN11.
What is the hypoglossal canal?
A structure for the passage of the hypoglossal nerve CNXII out of the cranial cavity
Found within the occipital bone
What are the dural venous sinuses?
Endothelial lined cavities between the periosteal and meningeal layers of the dura.
Large veins empty into these sinuses, drain into the internal jugular vein.
How does the arachnoid layer relate to the dural venous sinuses?
Arachnoid granulations into the dural venous sinuses, used as sites for the CSF to drain back into cardiovascular circulation
What are the main dural sinuses and where are they found? in the brain
The superior sagittal sinus - superior edge of the falx cerebri
The inferior sagittal sinus - inferior edge of the falx cerebri
The straight sinus - the fusion of the ISS and the great cerebral vein, runs along the attachment between the falx cerebri and the tentorum cerebelli
The occipital sinus - posteriorly to the cerebellum to the external occipital protuberacne
Transverse sinus - runs along the occipital bone to the edge of the parietal bone
Sigmoid sinus - continuation of the transverse sinus, runs along the temporal bone until in meets the internal jugular vein
Cavernous sinus - lateral to the sella turcica drains into superior petrosal sinus onto the inferior jugular vein by the interior petrosal sinus.
What is the confluence of sinuses?
Region in the brain close to the external occipital protuberance where the dural sinuses merge together, blood flow can take many directions
What is the clinical importance of the cavernous sinus?
Many cranial nerves pass out of the skull near the cavernous sinus, thrombosis in this sinus may exert pressure on the nerves causing damage and cranial nerve palsy.
What structure is shown in the image?
External occipital protuberance
What structure is shown in the image?
Internal occipital protuberance
What structure is shown in the image?
Imprints from dural venous sinuses
What structure is the large hole shown in the image?
The foramen magnum
What structure is shown in the image?
Petrous portion of the temporal bone
What structure is shown in the image?
The squamous portion of the temporal bone
What structure is shown on the image?
The mastoid process on the temporal bone
What structure is shown in the image?
External acoustic meatus of the temporal bone
What structure is shown in the image?
The styloid process of the temporal bone
What structure is shown in the image?
In dark green
The lesser wing of the sphenoid bone
What structure is shown in the image?
The greater wing of the sphenoid bone
What structure is shown in the image?
The clivus of the sphenoid bone
Links with the Clivus on the occipital bone for resting of the brain stem
What structure is shown in the image?
The sella turcica of the sphenoid bone
What structure is shown in the image?
The pterygoid process of the sphenoid bone
Made of a medial and lateral plate
What structure is shown in the image?
The ciribiform plate of the ethmoid bone
What is shown in the image below?
The superior and medial nasal conchae bones - part of the ethmoid bone
The inferior nasal conchae bones,
Note all structures are bilateral
What is shown in the image below?
The zygomatic bone
What structure is shown in the image?
In the large red circle
The pterion region
Deep to this is the middle meníngeas artery
What is the red hole called?
The optic canal
What is the green hole called?
The superior orbital fissure
What is the red hole called?
In the sphenoid bone
The optic canal
What is the green bone in the sphenoid bone called?
The supraorbital fissure
What is the dark blue hole called?
The foramen rotundum
What is the yellow hole called?
Internal acoustic meatus
What is the light blue hole called?
Foramen ovale
What are the large red circles called?
The jugular foramen
What is the pink structure called?
The hypoglossal canal
Note is bilateral
What are the little red holes next to foramen ovale?
The foramen spinosum - contains the middle meníngeas artery
What is the green structure next for Forman ovale?
The foramen lacerum
Does not contain any structures but is passed over anteriorly by the internal corotid artery
Where do the vertebral arteries enter the cranium?
Via the foramen magnum
What three arteries supply the cerebellum?
The superior cerebellar
The anterior inferior cerebellar
The posterior inferior cerebellar
What is the labyrinthine arteries?
Branches of the anterior inferior cerebellar artery
Supplies structures in the ear
What are the ophthalmic arteries?
Branches of the internal carotid arteries
Supply the eyelids, conjunctiva and the lacrimal gland
What area of the primary motor cortex are supplied by which cerebral arteries?
What areas of the primary sensory cortex are supplied by which cerebral arteries?
What are the different lobes of the brain?
Green - frontal
Yellow - temporal
Red - parietal
Blue - occipital
Where is the central sulucs of the brain?
Seperates the frontal and the parietal lobe
Where is the lateral/sylvian sulucs of the brain?
Seperates the temporal lobe from the frontal and the parietal lobe
Where is the longituidinal fissure of the brain?
Seperates the left and right cerebral hemispheres
Where is the transverse fissure of the brain?
Seperates the cerebellum from the cerebrum
Where is the prefrontal cortex found?
The anterior part of the frontal lobe
Where is the primary motor cortex found?
Just anterior to the central sulcus
Where is the pimray somatosesnory cortex found?
Just posterior to the central sulcus
Where is the primary visual cortex found?
Posterior and inferior aspect of the occipital lobe
Where is Brocas area found?
Part of the frontal lobe
Roughly half way along the lateral sulucs
Where is Wernickes area found?
At the junction between the temporal and parietal lobes
What are the layers of the scalp?
S - skin
C - dense connetive tissue
A - aponeurotic layer - muscle and aponeurosis
L - loose connective tissue
P - pericranium
What type of skin is found on the scalp?
Hair is present on a large amount of it
Thickest skin on the body
Why does the scalp bleed a lot when it is injured?
First three layers are well fused together, often all removed during injury
Dense connective tissue under the skin containg the blood vessels, holds the blood vessel open, causes prolonged bleeding
Where do blood vessels supplying the meninges run?
What type of hemorrhage would this cause?
Located in the subarachnoid space
Results in a subarachnoid hemorrhage or an epidural hematoma
Where do the blood vessels supplying the brain run?
What type of hemorrhage would this cause?
Run under the pia mater on the brain tissue
Causes an intraparenchymal hemorrhage
What is the cerebrum also known as?
The tencephalon
What are these five different regions of the brain?
Thalamus
Hypothalamus
Midbrain (mesencephalon)
Pons (Metencephalon)
Medulla oblangata (myencephalon)
What is the flow of blood in the main dural venous sinuses?
The inferior sagittal sinus drains into the great cerebral vein into the straight sinus.
The occipital sinus and superior sagittal sinus also drains into the confluence of sinuses.
This drains into the confluence of sinuses
This drains into the transverse sinus, into the sigmoid sinus into the internal jugular vein
How is blood from the opthalmic veins drained?
Drained into the cavernous sinus into the internal jugular vein
F
And what is it?
Part of the limbic system, help regulates emotions and pain
What is the superior colliculus?
D
Integrates visual, auditory and somatosensory information to orientate the head, neck and eyes to identify the source of information
What is the corpus callosum?
Connects left and right cerebral hemispheres
Identify the cerebellar arteries
A = superior cerebellar
B= anterior inferior cerebellar
C = posterior inferior cerebellar artery
Label the different cranial nerves
