Dissection guide

Question 1

dissection 1

define leptomeninges

Answer 1

arachnoid + pia

Question 2

dissection 1

name the three layers of the dura

Answer 2

periosteal, meningeal and thin layer of border cells (the weakest portion)

Question 3

dissection 1

Id the sinuses in the brain

Answer 3

superior sagittal sinus: (where the falx cerebri merges with the dura)

inferior sagittal sinus: (along the free (lower) edge of the falx cerebri)

straight sinus: where the falx cerebri meets the tentorium cerebelli.

transverse sinus: where the tentorium joins the dura of the skull

Question 4

dissection 1

what is the tentorium cerebelli

Answer 4

seperates the cerebrum from the cerebellum. It wraps aroundthe brainstem with a notch (tentorial notch) which seperates the cranial cavity into a supratentorial and infratentorial space (posterior fossa)

Question 5

dissection 1

what does the infundibulum connect

Answer 5

hypothalamus to the pituitary

it penetrates the diaphragma sellae which is a small sheet of dura that covers the sella turcica

Question 6

dissection 1

what borders both limit brain movement and can contribute to compression of the brain

Answer 6

falx cerebri and tentorium

Question 7

dissection 1

where the the middle meningial arteries located and what can they lead to

Answer 7

they are embedded within the dura and they can lead to an epidural hematoma

Question 8

dissection 1

what do the trabeculae connect

Answer 8

the arachnoid to the pia

Question 9

dissection 1

are there free nerve endings within the brain, arachnoid, pia

Answer 9

only in the pia

Question 10

dissection 1

what is a delayed consequence of this exposure to extravascular blood in the subarachnoid space

Answer 10

cerebral artery vasospasm and possible hydrocephalus, resulting from blood interfering with reabsorption of CSF through the arachnoid villi into the dural sinuses.

Question 11

dissection 1

what is the significance of bridging veins

Answer 11

they can tear as a result of trauma and lead to a subdural hematoma since the dural border is the weakest and this is where they penetrate and are prone to tear

Question 12

dissection 2

ID the two main sulcuses and what they seperate

Answer 12

lateral and central sulcus….

central sulcus is bordered by the precentral gyrus (with motor cortex), anteriorly, and the postcentral gyrus (with sensory cotext), posteriorly.

damage to the central sulcus can present with contralateral motor damage and sensation loss

Question 14

dissection 2

ID the two main fissures

Answer 14

longitutenal and transverse

Question 15

dissection 2

what is the significance of the superior temporal gyrus

Answer 15

superior temporal gyrus contain the primary auditory cortex, the first place within the cerebral hemispheres that processes auditory input.

The superior temporal gyrus within the dominant hemisphere is involved in processing of spoken language (you may have heard of Wernicke’s area). I

t is clinically important to understand that “dominant” refers to the hemisphere that is dominant for language, not handedness. Almost all right-handed people and the large majority of left-handed people are left hemisphere dominant.

angular and supramarginal gyrus in parietal lobe can also be important for language

Question 16

dissection 2

what is an uncal lobe herniation

Answer 16

medial temporal lobe herniation, this occurs if a large supratentorial mass takes up enough space that the brain is forced downward past the tentorium

Question 17

dissection 2

Explain the information carried by each optic nerve and tract

Answer 17

optic nerve- carries information from a single eye

optic tract- carries information from a single visual field

Question 18

dissection 2

what area of the brain are mammillary bodies in

Answer 18

only visible part of the diencephalon in the uncut brain

Question 20

dissection 2

explain cerebral and cerebellar peduncles and corticospinal/corticobulbar tracts

Answer 20

cerebral peduncles- axons from cell bodies from the motor cortex

cerebellar peduncles- axons from cell bodies into and out of the cerebellum

corticospinal- axons that begin in the cerebral cortex and terminate in spinal cord

corticobulbar-axons that begin in the cerebral cortex and terminate in brainstem

Question 21

dissection 2

where are the 2 places that UMN reside

Answer 21

cerebral cortex and brainstem

Question 22

dissection 2

what would damage to corticospinal tract axons that originate in the left motor cortex cause

Answer 22

It is important to understand that the corticospinal tract axons that originate in the left motor cortex pass through the anterior midbrain within the left cerebral peduncles, continue through the left side of the base of the pons (anterior, but not visible to us on the surface) and are again visible as the left medullary pyramid on the anterior surface of the medulla. Each cerebral hemisphere is primarily concerned with movement of the opposite side of the body. So damage to the left motor cortex, left cerebral peduncle, left side of pontine base, or left medullary pyramid should affect the right side of the body.

Decussation occurs at the VERY CAUDAL medulla then the UMN continue and connect to LMN on anterior horn of spinal cord

damage to either medullary pyramid will cause contralateral paresis or paralysis since this damage disrupts the ability of the ipsilateral cerebral hemisphere to communicate motor commands to the contralateral body.

Question 23

dissection 2

ID the flow of the corticospinal tract

Answer 23

n the cerebral cortex, these axons form a wide spray referred to as the corona radiate (‘ ). As they all bundle tightly together to squeeze past deep structures, including the thalamus, they form part of a sheet of axons termed the ). They then pass along the anterior surface of the midbrain as part of the ), on though the and finally they bundle onto the anterior surface of the medulla as a medullary pyramid

Question 24

name the 2 sets of arteries that blood supply can enter the brain

Answer 24

internal carotid

vertebral arteries

Question 25

where do the 2 internal artreries and the 2 vetebral arteries enter the cranial cavity

Answer 25

internal carotid- foramen lacernum

vetebral- foramen magnum

Question 26

ID the blood flow from the internal carotid (anterior circulation)

Answer 26

internal carotid 3 branches then bifurcates: opthalmic, anterior choroidal and posterior communicating

bifurcates–> ACA and MCA

Question 27

ID the blood flow through the vetebral arties ( posterior circulation/ vertebral-basilar)

Answer 27

2 veterbal –> basillar –> posterior cerebral arteries

supplies brainstem and inferior temporal and occipital lobes

Question 28

name the arteries that branch off of the vetebral before it becomes the basilar and a syndrome associated with damage to one of the branches

Answer 28

the anterior spinal

the posterior spinal

(both medial)

the posterior inferior cerebral artery (PICA)

lateral

Loss of vertebral/PICA perfusion causes lateral medullary syndrome, a combination of several sensory and motor deficits that reflects the large array of tracts and nuclei in this area. PICA is a major site of aneurysms

PICA supplies important perfusion to dorsolateral medulla, which contains several significant tracts (e.g. spinothalamic, spinal trigeminal, descending sympathetic) and cranial nerve nuclei (including nucleus ambiguus, which is important to speech and swallowing).

Question 29

what structures supply the medulla, pons, cerebellum, midbrain, inferior temporal lobe & occipital lobe

Answer 29

medulla- ASA, PSA, vetebral, posterior inferior cerebellar arteies

pons-basillar and anterior inferior cerebellar arteries

cerebellum- each half supplied by one superior and two inferior cerebellar arteries

midbrain- superior basillar & superior cerebellar arteries.

inferior temporal lobe & occipital lobe- PCA

Question 30

what do the ACA, MCA and anterior choroidal artery arteries supply

what is their clinical relevance

Answer 30

Supply

ACA-

medial and dorsal aspect of cerebral hemisphere ( orbital and medial surfaces of frontal lobe)
MCA-

anterior thalamus and corpus striatum (a portion of the basal nuclei), motor, somatosensory, auditory and language areas

anterior choroidal artery-

choroid plexus of lateral ventricle, globus pallidus, internal capsule, amgydala, hippocampus

landmarks

ACA-

longitudinal cerebral fissure
MCA-

lateral sulcus

anterior choroidal artery-

clinical relevance

ACA-

strokes in its field can cause sensory and motor deficit in the contralateral lower body as well as urinary incontinence
MCA-

motor, sensory and language impairment

anterior choroidal artery-

the anterior choroidal artery is a particularly long and narrow vessel that is more prone than some to aneurysms and vascular occlusion. Since it supplies the hippocampus, transient amnesia could occur if it becomes temporarily occluded

Question 31

draw out the circle of willis

Answer 31

Question 32

ID the venous flow and consequence of its occlusion

Answer 32

inferior cerebral veins –> caverus sinus and tranverse sinus

superior cerebral veins –> superior saggital sinus

(deep ) internal cerebral veins –> great cerebral vein –> inferior saggital sinus

Venous drainage of the brain can be divided into two parts: superficial and deep. The cerebral veins arising from capillaries traverse the subarachnoid space and empty into a system of inter-communicating channels, called dural sinuses which are located between the meningeal and periosteal layers of the dura. These sinuses include the superior sagittal, the inferior sagittal, the transverse, the rectus (or straight), and th ecavernous. In turn, the sinuses drain into the internal jugular veins, which return blood to the heart. It is clinically important that the major veins and sinuses drain multiple territories of the brain. Occlusion of one of these can lead to edema, increased intracranial pressure, herniation, and death.

Question 33

What divides the occipital lobe and what is superior and inferior to it

what side of your brain prosseses visual input fron the right side

what gyrus processes things above or below the point of focus

Answer 33

divided by the calcarine sulcus

suprior- The cuneate gyrus

inferior- lingual gyrus

the primary visual cortex of the left hemisphere

above- calcarine gyrus

below- lingual gyrus

Question 34

what is the clinical signifiance of the consensual pupullary light response

Answer 34

Axons running through posterior commissure support the consensual pupillary light response (the constriction of one pupil when light is shown into the other pupil only). Compression of the dorsal pretectal area (possibly due to hydrocephalus or, rarely, to a pineal tumor) can cause loss of the consensual light reflex. (“Pretectal” refers to just the region rostral to the tectum; tectum is a term for the midbrain dorsal to the aqueduct.)

Question 35

what is the flow of CSF

Answer 35

Lateral ventricles –> interventricular foramina (of Monro) –> third ventricle –>cerebral aqueduct (of Sylvius) –> fourth ventricle –> median and lateral apertures (foramina of Magendie and Luschka) –> subarachnoid space.

Question 36

name the clinically relevant landmark that marks the midline of the hemispheres and can be pushed off center if lateral ventricles are compresed

Answer 36

septum pellucidum