Download Gross Anatomy of the Brain - Dr. Leichnetz

Gross Anatomy of the Brain
George R. Leichnetz, Ph.D.
There are five divisions of the brain which correspond to the embryonic brain vesicles from which
their component parts are derived: telencephalon, diencephalon, mesencephalon, metencephalon,
and myelencephalon.
Three large brain subdivisions: the cerebrum (two cerebral hemispheres containing diencephalon
and telencephalon), cerebellum and brainstem (midbrain, pons, medulla).
I.
TELENCEPHALON: cerebral cortex, subcortical white matter and basal ganglia
A. Lateral Aspect: the cerebrum has five lobes: frontal, parietal, temporal, insular, and
occipital lobes
Central Sulcus - separates frontal and parietal lobes
Lateral Sulcus - separates frontal and parietal lobes from temporal lobe
Preoccipital Notch- indentation on inferior margin of hemisphere, delineates temporal
from occipital lobe
Frontal, Parietal, Occipital and Temporal Lobes
Frontal, Parietal, and Temporal Poles
Precentral Gyrus- vertical gyrus in front of central sulcus, caudal frontal lobe;
primary motor cortex
Postcentral Gyrus- vertical gyrus behind central sulcus, rostral parietal lobe;
primary somatosensory cortex
Insula (Insular Lobe)- hidden deep to lateral sulcus
Superior and middle frontal gyri
Inferior frontal gyrus- pars orbitals, triangularis, and opercularis
(Triangularis + Opercularis = Broca’s Motor Speech area)
Superior parietal lobule
Intraparietal sulcus- horizontal sulcus, separates superior and inferior parietal lobules
Supramarginal gyrus- rostral part of inferior parietal lobule
Angular gyrus- caudal part of inferior parietal lobule
Superior, middle and inferior temporal gyri
Superior transverse temporal gyri (of Heschl)- two parallel gyri running transversely on
the superior aspect of the temporal lobe; primary auditory cortex
Lateral occipital gyri
Noback et al. The Human Nervous System
B. Inferior Aspect- (Ventral Aspect of cerebrum)
Frontal lobe:
Olfactory Bulb and Tract (associated with C.N. I)
Orbitofrontal gyri- on the orbital (inferior) surface of the frontal lobe
Temporal lobe:
Inferior temporal gyrus and sulcus- visual discrimination
Occipitotemporal (fusiform) gyrus- recognition of faces
Collateral sulcus- separates occipitotemporal and parahippocampal gyri
Parahippocampal gyrus- gyrus on ventromedial temporal lobe, overlies hippocampus
Uncus- bump over amygdala/hippoc. on parahippocampal gyrus, ventromedial
aspect of temporal lobe
Noback et al. The Human Nervous System
C. Medial Aspect- (see mid-sagittal section below)
Corpus callosum- rostrum, genu, body, splenium; largest commissure of the brain;
interconnects lobes
Septum pellucidum- vertical membrane between lateral ventricles in hemispheres
Fornix- major tract from hippocampus to hypothalamus (mammillary body)
Lateral ventricles- ventricle within each cerebral hemisphere
Choroid plexus- vascular tufts in ventricle; produces cerebrospinal fluid (CSF)
Caudate nucleus- elevation in lateral wall of lateral ventricle
Stria terminalis- tract with terminal vein, delineates caudate from thalamus in floor of
lateral ventricle
Anterior commissure- interconnects temporal lobes
Lamina terminalis- vertical lamina between anterior commissure and optic chiasm;
closes embryonic anterior neuropore of neural tube
Limbic lobe- subcallosal, cingulate and parahippocampal gyri
Calcarine fissure- separates cuneus and lingual gyri, divides visual cortex
Cuneus gyrus- above calcarine fissure ____ primary visual cortex
Lingual gyrus- below calcarine fissure
Paracentral lobule- continuation of pre- and post-central gyri; representation of leg
Parieto-occipital sulcus- separates parietal and occipital lobes
Noback et al. The Human Nervous System
II.
DIENCEPHALON: thalamus, hypothalamus, epithalamus (pineal) and subthalamus
A. Ventral Aspect
Optic nerves (cranial nerve II)- originate from the retina (carry visual information)
Optic chiasm (crossing of optic nerves)
Optic tracts- tracts beyond optic chiasm, carry retinal (visual) input to thalamus
Tuber cinereum- elevation on the ventral aspect of the hypothalamus (contains median
eminence); infundibulum (pituitary stalk) comes off tuber cinereum
Mammillary bodies
B. Medial AspectThalamus- two egg-shaped structures in lateral walls of third ventricle; major relay in
sensory & motor pathways to cortex
Massa intermedia- (interthalamic adhesion)
Third ventricle- midline space separating thalami
Hypothalamus- in walls of vent. part of third ventricle; coordinates viscero-endocrine
functions
Pineal body (part of epithalamus)- produces melatonin; involved in biological rhythms
Posterior commissure- interconnects structures in rostral midbrain (pretectum)
C. Dorsal (Caudal) Aspect
Pulvinar- caudal end of “egg-shaped” thalamus
Medial geniculate body- auditory relay nucleus on caudal end of thalamus
Lateral geniculate body- visual relay nucleus on caudal end of thalamus (optic tract ends
here)
III. MESENCEPHALON: (or Midbrain)
A. Dorsal Aspect (see dorsal aspect of brainstem figure below)
Corpora quadrigenima- four elevations on dorsal midbrain
(2 superior colliculi, 2 inferior colliculi)
Superior colliculi- involved in orientation/ attention; reflexive eye and head movements
Inferior colliculi- major relay in auditory pathway
Trochlear nerve (Cranial nerve IV)- innervates superior oblique eye muscle
B. Ventral Aspect
Cerebral peduncles (right and left crus cerebri)- large bundles carrying cerebral efferent
tracts
Interpeduncular fossa- depression between cerebral peduncles
Oculomotor nerve (C.N. III)- innervates all extraocular muscles, except lat. rectus and sup.
oblique
C. Medial Aspect- (refer to midsagittal section above)
Cerebral aqueduct of Sylvius- small channel, connects third ventricle to fourth ventricle
Tectum of midbrain- above aqueduct, contains superior and inferior colliculi
Tegmentum of midbrain- below aqueduct contains red nucleus, midbrain reticular
formation and substantia nigra
Kiernan, The Human Nervous System
IV.
METENCEPHALON: consists of cerebellum and pons
A. Dorsal Aspect of Cerebellum
Lateral hemispheres of cerebellum
Vermis of cerebellum- midline worm-like convolution
B. Lateral Aspect
There are three pairs of cerebellar peduncles, large white fiber bundles that connect the
cerebellum to the brainstem.
Inferior cerebellar peduncle (restiform body and juxtarestiform body)- carries afferents
from medulla to cerebellum
Middle cerebellar peduncle (brachium pontis)- carries afferents from pons to cerebellum
Superior cerebellar peduncle (brachium conjunctivum)- carries efferents from
cerebellum to midbrain
Trigeminal nerve (C.N. V)- somatosensory for head/face; motor to muscles of
mastication
C. Medial AspectAnterior medullary velum- membrane forms roof over rostral fourth ventricle; between
superior cerebellar peduncles
IVth ventricle- ventricular space above pons and medulla
Tegmentum of pons, basilar pons
Vermis of cerebellum- midline cerebellum; contains ten sublobules
Anterior lobe of cerebellum- concerned with proprioception (position sense)
Primary fissure- separates anterior and posterior lobes
Posterior lobe of cerebellum- largest lobe of cerebellum; concerned with coordination of
movement
Posterolateral (prenodular) fissure- separates posterior lobe and flocculonodular lobe
Nodule- vermal portion of flocculonodular lobe (of cerebellum)- flocculus + noduleoldest part of cerebellum; concerned with vestibular sense
D. Dorsal Aspect of Pons and MedullaRhomboid fossa- diamond-shaped floor of IVth ventricle
Median sulcus- midline groove in rhomboid fossa
Sulcus limitans- rostrocaudally running groove in mid-lateral rhomboid fossa,;
embryological remnant; separates motor nuclei (medial) from sensory nuclei (lateral)
Facial colliculus- elevation over abducens nucleus and int. genu of facial nerve
Vestibular area- elevation over vestibular complex
Stria medullaris of IVth ventricle- fibers divide fossa into two triangles; rostral over
pons, caudal over medulla
Lateral recesses of IVth ventricle, foramen of Luschka- CSF leaves 4th ventricle into
subarachnoid space
Obex- caudal most point of rhomboid fossa (4th ventricle)
V.
MYELENCEPHALON: medulla oblongata
A. Dorsal Aspect- (refer to dorsal brainstem figure above)
Rhomboid fossa (floor of IVth ventricle)
Dorsal median sulcus- midline groove in rhomboid fossa
Fasciculus gracilis and gracile tubercle (clava)- elevation over nucleus gracilis
Dorsal intermediate sulcus- groove between fasciculus gracilis and fasiculus cuneatus
Fasciculus cuneatus and cuneate tubercle- elevation over nucleus cuneatus
Tuberculum cinereum (elevation over spinal tract and nucleus of the trigeminal V)
B. Ventral Aspect
Ventral median fissure- contains anterior spinal artery; supplies ventromedial medulla
Pyramids- large tracts running on either aide of the ventral median fissure; over
pyramidal (voluntary motor) tracts
Pyramidal decussation (motor decussation)- crossing of pyramidal tracts, disrupts vent.
median fissure
Olive- elevation over inferior olivary nucleus
Ventrolateral (preolivary) sulcus- ventromedial to olive; exit of hypoglossal nerve roots
(C.N. XII)
Hypoglossal Nerve- cranial nerve XII- innervates tongue muscles
Pontomedullary Junction- horizontal groove between pons and medulla
Cerebellopontine angle- lateral corners of pontomedullary junction between cerebellum
and pons
Abducens nerve- Cranial nerve VI- exits pontomedullary junction; innervates lat. rectus
Facial nerve- Cranial nerve VII- exits cerebellopontine angle- innervates facial muscles,
taste buds on ant. 2/3 of tongue
Vestibulocochlear (acoustic nerve)- Cranial nerve VIII- exits cerebellopontine angle;
vestibular and auditory divisions.
Postolivary sulcus- dorsolateral to olive; exit of cranial nerves IX, X and bulbar roots of
XI
Glossopharyngeal nerve- Cranial nerve IX; supplies stylopharyngeus muscle of
pharynx; taste post. 1/3 of tongue; carotid sinus and carotid body
Vagus nerve- C.N. X- innervates laryngeal muscles, visceral sensation from g.i. tract
Spinal Accessory nerve- C.N. XI- innervates sternocleidomastoid and trapezius muscles
Kiernan, The Human Nervous System