Neuroanatomy

Question 0

Clinical: Scalp

Answer 0

Scalp infection
Loose CT layer: blood and pus build up in this layer, passing into cranial cavity via emissary veins.
Infection or fluid can enter the eyelid from the scalp- frontalis m insertions into skin and subcutaneous tissue not bone.

Scalp lacerations
Bleed profusely due to numerous anastomoses between carotid aa
Black eyes: injury to scalp and forehead

Question 1

Layers of the Scalp

Answer 1

Skin: good arterial supply and venous and lymphatic drainage
Connective Tissue layer : cutaneous nerve supply, highly vascular used
Aponeurosis (Epicranial Aponeurosis) : formed by the frontal is and occipitalis muscle.
Loose CT: has potential spaces I.e infection, allows for free movement of the first three layers
Pericranium: is continuous with the fibres of the cranial sutures and this can’t be removed easily from there. Forms external periosteum of the cavaria

Question 2

Name the parts of the brain that are directly related to the floor of each of the cranial Fossae

Answer 2

Ant Cranial Fossa: frontal lobes
Middle cranial fossa: hypophysis, temporal lobes
Post Cranial fossa: brainstem, cerebellum

Question 3

Meningeal arrangement

Answer 3

1. Dura mater: external layer, fused with endosteum of the skull
2. Arachnoid mater: middle layer, in direct contact with dura, numerous arachnoid trabeculae cross the space to reach the pia mater
3. Pia mater: innermost layer, invests brain closely

Question 4

Meningeal spaces

Answer 4

Epidural space: between skull and dura mater, potential space

Subdural space: dura and archanoid, potential space

Subarachnoid space: between arachnoid and pia mater, actual space- contains CSF, trabecular cells, arteries and veins

Question 5

Dural venous sinuses: Location

Answer 5

Sup Sagittal: in attached border of flax cerebri
Inf Sagittal: free border of falx cerebri
Straight sinus: along line of falx cerebri to tentorium cerebelli
Transverse sinus: occipital and parietal(bone) attachment of tentorium cerebelli
Sup petrosal sinus: attachment of tentorium cerebelli to sup border of petrous temporal bone
Inf petrosal sinus: junction of petrous temporal bone and the clivus
Sigmoid sinus: descends along occipital bone to bulb of IJV
Sphenoparietal sinus: along lesser wing of sphenoid bone
Cavernous sinus: lat to body of sphenoid bone
Marginal sinus: surrounds foramen magnum
Occipital sinus: attachment of falx cerebelli to occipital bone

Question 6

Blood flow through venous sinuses

Answer 6

Diploic vv, sup cerebral vv, deep cerebral vv drain into the dural venous sinuses.
Sup Saggital sinus -> right transverse sinus ➡️
Inf saggital sinus + great cerebral v➡️ straight sinus ➡️ tranverse sinus ➡️ sigmoid sinus ➡️ IJV
Sup petrosal sinus joins post cavernous sinus with transverse and sigmoid sinus
Inf petrosal connects cavernous sinus with IJV
Sphenoparietal sinus ➡️ ant cavernous sinus
Intercavernous sinus connects the two cavernous sinus
Occipital sinus ➡️ confluence of sinuses

Question 7

Cerebral hemisphere

Answer 7

Superficial layer of grey matter : cerebral cortex
Sulci and gyri
Two hemispheres are joined by the corpus collosum
Axons from cells form white matter
Nuclear masses buried within white matter

Question 8

Insula

Answer 8

In depths of lateral sulcus
Opercula: parts of frontal, temporal and parietal lobes overlying the insula
Short gyri (3) - ant
Long gyri (2) - post
Central sulcus between them
Circular sulcus surrounds them
Gyri come together as the limen insulae

Question 9

Lat Surface of cerebrum

Answer 9

Lat sulcus:

• Ant(horizontal), asc & post rami
• lie between the portions of the inf frontal gyrus

Inf frontal gyrus:
Opercular: post
Triangular: middle
Orbital: ant

Intraparietal sulcus: separates the sup and inf lobules (supmarginal gyrus:upturned end of lat sulcus and angular gyrus: upturned end of sup temporal sulcus)

Question 10

Med surface of cerebrum

Answer 10

Cingulate gyrus (fibers= cingulum)
-directly sup to corpus collosum

Paracentral lobule:

• surrounds extension of central sulcus to the med surface
• lies post to paracentral sulcus and ant to marginal sulcus
• extension of pre & post central gyri onto the med surface

Med frontal gyrus
Cingulate sulcus
Callosal sulcus/ sulcus of corpus callosum
Parieto-occipital sulcus
Calcarine sulcus
Cuneus
Precuneus

Question 11

Inf surface of cerebrum

Answer 11

Olfactory tract lies in sulcus rectus/olfactory sulcus

Gyrus rectus/Straight gyrus lies med to it

Lat occipito-temporal gyrus continues with the inf temporal gyrus

Question 12

Primary motor cortex

Answer 12

Location: precentral gyrus
Contralat 1/2 of body represented in somatotopic fashion
Motor homunculus
Head controlled by the most inf part of primary motor cortex on lat surface
Lower limb controlled by med surface of primary motor cortex gyrus
//Area of cortex devoted to body part proportional to degree of precise movement possible

Question 13

Premotor cortex

Answer 13

Brodmann 6
Ant to precentral gyrus
Medial surface -> supplementary motor cortex
Programming of movement and control of posture

Question 14

Frontal eyefield

Answer 14

Brodmann 8
In middle frontal gyrus
Controls voluntary conjugate deviation of the eyes

Question 15

Primary somatosensory cortex

Answer 15

Brodmann 1, 2, 3
Parietal association cortex post to it
Interpretation and understanding

Question 16

Primary auditory cortex

Answer 16

Brodmann 41 & 42
Sup surface of sup temporal gyrus
Transverse temporal gyri = Heschl's gyri
Mostly hidden in lateral sulcus
Auditory association cortex
Auditory info is interpreted 
In dominant hemisphere the auditory association cortex is known as Wernicke's Area

Question 17

Primary visual cortex

Answer 17

Brodmann 17
Med surface occipital lobe
Gyri immediately sup and inf to calcarine sulcus
Rest of occipital lobe : visual association cotrex
Interpretation of visual images

Question 18

Primary olfactory cortex

Answer 18

Uncus and subjacent amygdala
Extends into limen insulae
Olfactory association cortex: ant part of the parahippocampal gyrus
Primary and association cortexes = pyriform cortex
Olfactory projection not via the thalamus

Question 19

Taste (gustatory area)

Answer 19

Adjacent to general sensory area of tongue (inf end of postcentral gyrus)
Extends to insula
Insula may be a site of integration of smell and taste

Question 20

Language Areas

Answer 20

Receptive language area: auditory assoc cortex (Wernicke’s area) and inf parts of supramarginal and angular gyri

Broca’s area (expressive speech area): opercular and triangular parts of inf frontal gyrus (brodmann 44 & 45)

Two areas are in communication with each through arcuate fasiculus

Question 21

White matter cerebrum

Answer 21

Association fibres: connect cortical areas within ONE hemisphere e.g. Arcuate fasciculus, cingulum

Commissural fibres: connect FUNCTIONALLY related structures between TWO hemispheres e.g corpus collosum, ant commisure

Projection fibres: between cerebral cortex and subcortical structures e.g internal capsule

Question 22

Cisterns

Answer 22

Cisterns: exist between regions of the pia mater and arachnoid mater, on regions where the brain does not conform exactly to the shape inside of the cranium

-pools of CSF in subarachnoid space.
Main cisterns:
- cistern of lat fossa
⭕️ Formed where arachnoid mater bridges the lat fissure and
contains middle meningeal a
- pre and post chiasmatic cisterns
⭕️ related to the optic chiasm
- interpeduncular cistern: formed where arachnoid mater bridges the cerebral peduncles, contains arterial circle of Willis
- cisterna ambiens, found on either side of midbrain,
‼️contains CNIV, post cerebral a, ant choroidal a, optic tract, basal vein of Rosenthal
- sup cistern: located between the splenium of corpus collosum and sup cerebellar surface, contains great cerebral v and pineal body

Cisterna ambiens + sup cistern = cisterna of great cerebral v

• pontine cistern: located ant to pons, contains vertebral a and basilar a and its branches
• cisterna magna/ cerebellomedullary cistern: extensive cistern where arachnoid mater spans between inf cerebellar surface and medulla,

Question 23

Lateral ventricle comprises of

Answer 23

Frontal horn: frontal lobe anterior to inter ventricular foramen

Central part: parietal lobe posterior to interventricular foramen stretching to the entrance of the temporal horn

Occipital horn: in occipital lobe surrounded by white matter

Temporal(inferior) horn: temporal lobe

Question 24

Describe the boundaries of the frontal horn

Answer 24

Lateral wall: head of the caudate nucleus Roof: corpus callosum Anterior wall: genuine of the corpus callosum limits the frontal horn anteriorly Medial wall: septum pellucidum *Floor: doesn't exist because the medial and lateral walls meet

Question 25

Boundaries of Central part (body)

Answer 25

Floor: - dorsal surface of the thalamus - with the tail of the caudate nucleus forming a ridge along the lateral border of the floor. - stria terminalis (originating in the amygdaloid body and going to the the septal area) and the thalamostriate vein lies medial to the tail of the caudate nucleus - Medially it is completed by the body of the fornix - choroid plexus is attached to the margins of the choroid fissure, which intervenes bettween the fornix and the thalamus Roof: corpus callosum

Question 26

Boundaries of Occipital horn

Answer 26

Medial wall: - There are two elevations on the medial wall - The upper one is the bulb of the occipital horn (produced by the fibers of forceps majour) - The lower one is calcar avis ( caused by calcarine sulcus )

Question 27

Boundaries of the temporal horn

Answer 27

Floor : - includes the hippocampus(inside), which is an extension of the parahippocampal gyrus (outside) "rolled into the floor" - pes hippocampi - fimbria of the fornix/fimbria of hippocampus is found along the medial border of the hippocampus - dentate gyrus is located medial to the hippocampus, hidden by the fimbria of the fornix - lateral to the hippocampus is a triangular area called the collateral triangle ( were the temporal and occipital horns diverge ) - in this area there is a bulge called the collateral eminence, caused by the collateral sulcus on the exterior Roof: - tail of the caudate nucleus with stria terminalis and thalamostriate vein medial to it - tail of the caudate nucleus extends to the amygdaloid body, which is also in the roof (just superior to the pes hippocampi)

Question 28

What is the pes hippocampi

Answer 28

The anterior expanded end of the hippocampus

Question 29

Third ventricle

Answer 29

- interventricular foramina connect it to the lateral ventricals - boundaries of the interventricular foramina are the columns of the fornix anteriorly and the anterior end of the thalamus posteriorly - the third ventrical is narrow slit bettween the two thalami and the two hypothalami

Question 30

Boundaries of the the third ventricle

Answer 30

Anterior wall: is the lamina terminalis and anterior commissure Lateral walls: thalamus and hypo thalamus with the hypothalamic sulcus separating them - thalamus has a bundle of fibers running across it named the stria medullaris thalami Floor: optic chiasma anteriorly, median eminence posteriorly, optic recess is found anterior to the optic chiasma, and posterior to that is the infundibular recess, that extends into the median eminence and proximal part of the pituitary stalk, posterior to that the floor slips upward to the cerebral aqueduct Roof: membranous and is attached along the stria medullares thalami - in the roof is a small choroid plexus is suspended from the roof - posteriorly in the roof habenular commissure, pineal recess, posterior commissure (which is just above the entrance to the cerebral aqueduct)

Question 31

Roof of the fourth ventricle

Answer 31

Filled with CSF Tent shaped Covered by the cerebellum The rostral part formed by sup cerebellar peduncles with the sup medullary velum stretching between them The caudal part of the roof is formed by the thin inf medullary vellum (often adheres to the cerebellum) Opening of the inf medullar velum is the median aperture (foramen Magendi) Median aperture opens into Cisterna Magna The choroid plexus is suspended from the inf medullary velum and extends into the lat recess The lateral walls Include the inf cerebellar peduncles Lat recesses extend around the medullar and open ventrally in the subarachnoid space as the lat apertures (foramina of Luschka) of the fourth ventricles The lat apertures are located at the junction of the pons, medulla and cerebellum (cerebellopontine angles) A small piece of choroid plexus usually extends through each lat aperture

Question 32

Production of CSF

Answer 32

Produced by choroid plexus of the ventricles Most CSF produced in lat ventricles Choroid plexus is formed by invaginations of vascular pia mater into the ventricles, taking along a layer of ependyma (lines ventricles on the inside)

Question 33

Circulation of CSF

Answer 33

Lateral ventricle -> third ventricle via interventricular formina -> fourth ventricle via cerebral aqueduct -> median aperture of the fourth ventricle -> cerebellomedullary cistern (cisterna manga, keep in mind that cisterns are part of subarachnoid space) -> lateral apertures of fourth ventricles -> subarachnoid space The CSF circulates around the brain and spinal cord A small amount of CSF enters the central canal of the spinal cord (the central canal and fourth ventricle are continuous)

Question 34

Absorption of CSF

Answer 34

Absorbed into venous system by passing into the dural venous sinuses The sup sagittal sinus is the main site of absorption The arachnoid mater invaginate into dural venous sinuses as arachnoid villi With age arachnoid villi become hypotrophic and is then called arachnoid granulations

Question 35

Why does absorption occur?

Answer 35

Hydrostatic pressure is higher in subarachnoid space than in the lumen of sinuses Colloid osmotic pressure of venous blood is greater than that of CSF

Question 36

Clinical Applications of CSF: hydrocephalus

Answer 36

Accumulation of CsF in the ventricular system Overproduction is rare Is usually the result of obstruction of normal CSF circulation The result is: dilation of ventricles Cause in the majority of cases in obstruction of the apertures of the fourth ventricle (Luschka and Magendi)

Question 37

Clinical Applications of CSF: menigitis

Answer 37

Can cause hydrocephalus Leptomenigeal adhesions may compromise CSF circulation at the level of ventricular outlets and/or arachnoid granulations.

Question 38

Clinical Applications of CSF: Brain Tumours

Answer 38

Can cause hydrocephalus An e.g a tumour that obstructs one of the interventricular foramina will result in a dilated lat ventrical on that side The obstruction can be bypassed by inserting a shunt that connects the ventricles to the IJV or abdominal cavity