Dissection guide Flashcards
dissection 1
define leptomeninges
arachnoid + pia
dissection 1
name the three layers of the dura
periosteal, meningeal and thin layer of border cells (the weakest portion)
dissection 1
Id the sinuses in the brain
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
dissection 1
what is the tentorium cerebelli
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)
dissection 1
what does the infundibulum connect
hypothalamus to the pituitary
it penetrates the diaphragma sellae which is a small sheet of dura that covers the sella turcica
dissection 1
what borders both limit brain movement and can contribute to compression of the brain
falx cerebri and tentorium
dissection 1
where the the middle meningial arteries located and what can they lead to
they are embedded within the dura and they can lead to an epidural hematoma
dissection 1
what do the trabeculae connect
the arachnoid to the pia
dissection 1
are there free nerve endings within the brain, arachnoid, pia
only in the pia
dissection 1
what is a delayed consequence of this exposure to extravascular blood in the subarachnoid space
cerebral artery vasospasm and possible hydrocephalus, resulting from blood interfering with reabsorption of CSF through the arachnoid villi into the dural sinuses.
dissection 1
what is the significance of bridging veins
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
dissection 2
ID the two main sulcuses and what they seperate
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
dissection 2
ID the two main fissures
longitutenal and transverse
dissection 2
what is the significance of the superior temporal gyrus
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
dissection 2
what is an uncal lobe herniation
medial temporal lobe herniation, this occurs if a large supratentorial mass takes up enough space that the brain is forced downward past the tentorium
dissection 2
Explain the information carried by each optic nerve and tract
optic nerve- carries information from a single eye
optic tract- carries information from a single visual field
dissection 2
what area of the brain are mammillary bodies in
only visible part of the diencephalon in the uncut brain
dissection 2
explain cerebral and cerebellar peduncles and corticospinal/corticobulbar tracts
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
dissection 2
where are the 2 places that UMN reside
cerebral cortex and brainstem
dissection 2
what would damage to corticospinal tract axons that originate in the left motor cortex cause
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.
dissection 2
ID the flow of the corticospinal tract
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
name the 2 sets of arteries that blood supply can enter the brain
internal carotid
vertebral arteries
where do the 2 internal artreries and the 2 vetebral arteries enter the cranial cavity
internal carotid- foramen lacernum
vetebral- foramen magnum
ID the blood flow from the internal carotid (anterior circulation)
internal carotid 3 branches then bifurcates: opthalmic, anterior choroidal and posterior communicating
bifurcates–> ACA and MCA
ID the blood flow through the vetebral arties ( posterior circulation/ vertebral-basilar)
2 veterbal –> basillar –> posterior cerebral arteries
supplies brainstem and inferior temporal and occipital lobes
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
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).
what structures supply the medulla, pons, cerebellum, midbrain, inferior temporal lobe & occipital lobe
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
what do the ACA, MCA and anterior choroidal artery arteries supply
what is their clinical relevance
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
draw out the circle of willis
ID the venous flow and consequence of its occlusion
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.
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
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
what is the clinical signifiance of the consensual pupullary light response
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.)
what is the flow of CSF
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.
name the clinically relevant landmark that marks the midline of the hemispheres and can be pushed off center if lateral ventricles are compresed
septum pellucidum
