Development/Landmarks Flashcards
neural groove and folds
depression in neural plate (2nd event) edges start to grow dorsally creating folds
neural tube
formed by fusion of neural folds. hollow part of the tube develops into ventricular system (cavities within adult brain filled with CSF)
Neural crest derivatives
- dorsal root ganglia = spinal ganglia (collection of cell bodies outside the CNS)
- sensory ganglia of certain nerves
- autonomic ganglia - inside walls of viscera (collection of cell bodies)
- adrenal medulla
Prosencephalon
primary vesicle stage, rostral end of tube
front of brain = forebrain
Mesencephalon
primary vesicle - midbrain
rhombencephlon
primary vesicle - hindbrain, caudal end of tube
telencephalon and Diencephlon
secondary vesicles that originate from the prosencephalon and make up the forebrain
mesencephalon (2)
secondary vesicle originating from mesencephalon with very little differentiation, keeps cylindrical shape
metencephalon and myelencephalon
secondary vesicles that originate from the rhombencephalon and make up the hindbrain, most caudal portion of the brainstem
lateral ventricles
within telecephalon, C-shaped, left and right lateral ventricles are connected by a T-shaped intersection called the interventricular foramen (left = I, right = II)
Third ventricle
in diencephalon found at the midline, a large circle
Mesencephalic aqueduct
midline structure within mesencephalon
fourth ventricle/rhomboid fossa
under the cerebellum that lies over the met/myelencephalon
contains:
Lateral apertures - foramen of luschka
Median aperture - foramen of Magendie - ONLY in primates, empties into cisterna magna (space between lining of CNS) to provide cushioning effect
(CSF goes thru into subarachnoid space)
rostral neuropore
anencephaly (without brain) - front opening of neural tube fails to close leading to error in brain development
caudal neuropore
spina bifida (without spinal cord) - back opening of neural tube fails to close
brain flexures
- midbrain - cranial ventral surface, most rostral
- pontine - dorsal surface
- cervical - caudal ventral surface, most caudal, does not flex much in most animals (180 degrees)
- primates/upright animals - 90 degree angle
division of the nervous system
- CNS - brain and spinal cord
- PNS (outside CN) - ganglia and cell processes = nerve fibers
- ANS - features of both CNS and PNS
histologic development of the spinal cord
- marginal layer - becomes white matter, lateral most white matter of cord = cell processes/axons (myelinated)
- Mantle layer - becomes gray matter = cell bodies
- germinal layer - ependymal cells, medial most, lining of ventricular system and central canal of spinal cord
sulcus limitans
“Limiting groove”
outpouching in middle of neural tube, divides neural tube b/w alar and basal, sensory and motor
Alar plate - sensory, dorsal
basal plate - motor, ventral
central nervous system components: Brain
Gray matter: cortical - surface of brain cerebrum, 6 layers
Subcortical - under the surface, pockets of cell bodies
white matter: under the cortical gray, tracts and pathways
(depending on location cell bodies have different function)
central nervous system components: spinal cord
gray matter: under the surface, columns and horns
white matter: surface bundles, form tracts (fasciculus=small bundle, funiculus=large bundle)
neural plate
thickening of tissue from ectoderm layer
peripheral nervous system
cell bodies = ganglia
cell processes = nerve fibers
PNS gray and white matter
Gray matter = cell bodies:
dorsal root ganglia, autonomic ganglia (walls of viscera, around abdominal aortic blood vessels), ganglia of sensory cranial nerves
White matter = cell processes:
nerve fiber bundles ex: radial nerve
landmarks of myelencephalon
- trapezoid body = rostral limit
- fourth ventricle - caudal half of rhomboid fossa
landmarks of metencephalon
- transverse fibers of the pons - ventral surface
- cerebellum - dorsal surface
- cerebellar peduncles - middle (most lateral), caudal (middle), rostral (most medial) - named in relation to cerebellum and consist of 3 stalk like structures that pass between brainstem and cerebellum
- fourth ventricle - rostral half of rhomboid fossa
landmarks of mesencephalon
- crus cerebri - left and right bundles
- corpora quadrigemina - roof of mesencephalon, consists of rostral colliculus (paired) and caudal colliculus (paired)
- tectum - roof/dorsal portion
- tegmentum - floor/ventral portion
- mesencephalic aqueduct - determines dorsal and ventral portions
diencephalon subdivisions
- thalamus - oval, rostral to optic tract, makes up majority of Di
- epithalamus - area of pineal body and 3rd ventricle
- metathalamus - 2 geniculate bodies
- subthalamus - internalized structure, connects Di rostrally and Mesencephalon caudally
- hypothalamus - ventral portion
landmarks of diencephalon
- optic chiasm - rostral limit where CN II fibers meet and cross
- mamillary bodies - caudal limit, at back of hypothalamus
- optic tract - carries visual info to brain, over lateral surface
- geniculate bodies = metathalamus (lateral has 2 lt and rt = site of termination of optic tract; medial has 2 lt and rt)
- third ventricle - circular, wraps around brainstem with pineal body located on midline (area of epithalamus)
landmarks of telencephalon
- cerebrum containing left and right cerebral hemispheres
- lateral ventricles - left side is ventricle I and right side is ventricle II
Origin and clinical terms of telencephalon and Diencephalon
origin - prosencephalon
clinical - forebrain
-thalamocortex - interconnection of Tel and Di with cerebral hemispheres
Origin and clinical terms of mesencephalon
origin - mesencephalon
clinical - midbrain
Origin and clinical terms of metencephalon and myelencephalon
Origin - rhombencephalon
clinical - hindbrain
-metencephalon - pons=brainstem and cerebellum
-myelencephalon - medulla
anatomic brain
Cerebrum + brainstem
cerebellum = telencephalon
brainstem = Di, Mes, Met, Myencephalon
site of termination of the spinal cord in various species
dog = L5
horse = S1 or S2
Bovine and feline = L6
what is the cervical intumescence
enlargement between C6 and T2 - area of brachial plexus
what is the lumbar intumescence
enlargement at L5 to S1 - fibers innervating pelvic limb
conus medullaris
end of spinal cord with meningeal covering
layers of meniges
1) dura mater
2) arachnoid
3) pia mater (deepest and in contact with nerve fibers)
filum terminale
terminal thread, extension of dura mater that travels down midline of spinal canal to anchor spinal cord
cauda equina
literally means horse tail, all roots of spinal nerves traveling down caudal space of canal until they reach their specific foramina
Spinal nerve roots correspond to what white matter structure
Funiculus
Spinal nerve rootlets correspond to what white matter structure
Fasciculus
Radicular signs mean that what are being affected
Spinal nerve roots
Major white matter structures (3)
Dorsal, lateral, and ventral funiculi
Major gray matter structures (3)
Dorsal, ventral, and lateral horns
portions of mesencephalon
tectum=roof/dorsal portion
tegmentum=floor/ventral portion
dorsal and ventral portions determined by mesencephalic aqueduct
Nuclear “columns” of spinal cord neurons (4)
GSA - general somatic afferent GVA - general visceral afferent (Sulcus limitans) GVE - general visceral efferent GSE - general somatic efferent
Function of afferent fibers
Sensory
Function of efferent fibers
Motor
Myelencephalon - ventral structures (4)
- pyramids
- pyramidal decussation
- olive
- trapezoid body
Pyramids of myelencephalon
L and R on ventral midline
Pyramidal motor pathway
groove b/w = ventral median fissure
origin = cerebrum
Pyramidal decussation
Fibers cross at site of synapse
75% fibers cross to descend as lateral corticospinal tract
25% continue ipsilaterally into spinal cord as ventral corticospinal tract
(Ex. 75% that start on L and R = contralateral, 25% stay on same side as origin = ipsilateral)
Olive
Small bump about halfway down myelencephalon, *site of synapse in extrapyramidal motor system
Trapezoid body
Rostral limit of myelencephalon, involved in auditory system
Myelencephalon - dorsal structures (4)
- fasciculus gracilis
- fasciculus cuneatus
- spinal tract of trigeminal n.
- obex
Dorsal surface of myelencephalon
Characterized by tracts and ventricle 4 - “open” in rostral portion
Fasciculus gracilis
Conscious proprioception from pelvic limb area
Most medial compared to dorsal median sulcus, paired L and R
(Proprioception = knowing where your limbs are)
Fasciculus cuneatus
Conscious proprioception from thoracic limb area
Lateral to fasciculus gracilis, paired L and R
Bundle of white matter
Spinal tract of the trigeminal n.
Pain and temp sensation from head and face areas
Lateral to fasciculus cuneatus, paired L and R
Obex
Landmark at caudal angle of 4th ventricle, where bundles meet at the “V”
Myelencephalon - ventricular system structures (4)
- 4th ventricle (caudal half)
- caudal medullary velum
- sulcus limitans
- dorsal median sulcus
Caudal medullary velum
Thin layer of ependyma and pia mater so ventricle not actually “open;” roof of 4th ventricle
Sulcus limitans (myelencephalon ventricular system)
Groove in lateral wall of 4th ventricle
Dorsal median sulcus
Continuation from spinal cord in midline of ventricular floor
Cranial nn. in myelencephalon
CN 6-12 (most of any part of brain)
Metencephalon - ventral structures (2)
- transverse fibers of the pons
- longitudinal fibers of the pons
Transverse fibers of the pons
Pyramidal motor fibers going into cerebellum - become middle cerebellar peduncle as they take info to cerebrum (originate on midline)
Longitudinal fibers of the pons
Pyramidal motor fibers going through brainstem and into spinal cord
Metencephalon - dorsal structures (2)
- cerebellum
- cerebellar peduncles
Cerebellum
Coordinates, integrates, and regulates motor activity with sensory info
Cerebellar penducles
Middle, caudal, and rostral pairs
Connect cerebellum to brainstem
Carry sensory and motor
Metencephalon - ventricular system structures (2)
- 4th ventricle (rostral half)
- rostral medullary velum
Rostral medullary velum
Layers of ependyma and pia mater
Cranial nn. in metencephalon
CN 5 (the big one)
Mesencephalon - ventral structures (2)
- crus cerebri
- interpeduncular fossa
Crus cerebri
Descending pyramidal motor pathway
2 columns, L and R
Forms floor of mesencephalon
Mesencephalon - dorsal structure
Corpora quadrigemina (site of synapse) or rostral and caudal colliculi *rostral colliculus (L and R) - visual reflexes; caudal (L and R) - auditory
Mesencephalon - ventricular system structure
Mesencephalic aqueduct - interconnects 3rd and 4th ventricles
Cranial nn. in mesencephalon
CN 3 (oculomotor) and CN 4 *CN 4 only CN that's dorsal (others ventral)
Diencephalon - ventral structures (4)
- mammillary bodies
- tuber cinereum
- optic chiasm
- optic tract
Mammillary bodies
Site of synapse for emotions and ANS
Caudal limit of diencephalon, on floor of hypothalamus
Tuber cinereum
Site of attachment for pituitary gland
Optic chiasm
Site of decussation for vision
Crossing for CN 2
Rostral limit of diencephalon
Optic tract
Visual pathway
Come up laterally after crossing and form lateral geniculate body
Diencephalon - dorsal structures (2)
- lateral geniculate body
- medial geniculate body
- together form the metathalamus
Lateral geniculate body
Termination of optic tract -> site of synapse in visual pathway
Medial geniculate body
Site of synapse in auditory pathway
Diencephalon - ventricular system structures (3)
- 3rd ventricle - wraps around medial geniculate body (?)
- interthalamic adhesion
- pineal body
Interthalamic adhesion
Cut surface of thalamus as seen on midline (topographic term)
Pineal body
Melatonin to regulate sleep patterns and circadian rhythm
Forms epithalamus, midline structure rostral to geniculate bodies
Cranial nn. in diencephalon
CN 2 (rostral limit)
Telencephalon - ventral structures (2)
- olfactory bulb
- pyriform lobe
Olfactory bulb
Site of synapse in olfactory pathway
Oval-shaped, at very rostral end
Cell bodies start in nose and axons go to brain
Pyriform lobe
Olfactory cortex, where smell is perceived
Telencephalon - dorsal structures (3)
- gyrus/gyri - ridges of gray matter
- sulcus/sulci - grooves
- cerebral hemispheres
Cerebral hemispheres
L and R, split by longitudinal cerebral fissure
Transverse cerebral fissure divides cerebrum and cerebellum
Telencephalon - ventricular system structures (2)
- lateral ventricles
- interventricular foramen
Lateral ventricles
Left = I, right = II in each hemisphere
Interventricular foramen
Connection b/w lateral ventricles, also connects to 3rd ventricle -> “T” connecting L, R, and 3rd ventricles
Cranial nn. in telencephalon
CN 1 (olfactory)
Telencephalon fiber systems (3)
- projection fibers (ascending and descending)
- association fibers
- commissural fibers
Association fibers
Long fibers = interlobar - b/w lobes (cingulum)
Short = intralobar - b/w adjacent gyri
Commissural fibers
Corpus callosum - commissural bundle
Cross the midline
