Download The lateral sulcus

Neuroanatomy Lectures
Lecture 4
Cerebrum
‫ ليث ثامر خزعل‬.‫د‬
Cerebrum
Subdivisions of the Cerebrum
The cerebrum is the largest part of the brain, situated in the
anterior and middle cranial fossae of the skull and occupying
the whole concavity of the vault of the skull. It may be
divided into two parts: the diencephalon, which forms the
central core, and the telencephalon, which forms the
cerebral hemispheres.
The diencephalon
consists of the third ventricle and the structures that form its
boundaries It extends posteriorly to the point where the third
ventricle becomes continuous with the cerebral aqueduct
and anteriorly as far as the interventricular foramina Thus,
the diencephalon is a midline structure with symmetrical
right and left halves
Superior view
of the
cerebral
hemispheres
Gross Features of diencephalon
inferior surface
The only area exposed to the surface in the intact
brain.
formed by hypothalamic and other structures,
which include, from anterior to posterior, the
optic chiasma, with the optic tract on either
side; the infundibulum, with the tuber
cinereum; and the mammillary bodies
superior surface of the diencephalon
is concealed by the fornix
Fornix is thick bundle of fibers that originates in the
hippocampus of the temporal lobe and arches posteriorly
over the thalamus to join the mammillary body
Sup wall formed by roof of the third ventricle
lateral surface of the diencephalon
bounded by the internal capsule of white matter
Medial surface
Since the diencephalon is divided into symmetrical halves by
the slitlike third ventricle, it also has a medial surface. The
medial surface of the diencephalon (i.e., the lateral wall of
the third ventricle) is formed in its superior part by the
medial surface of the thalamus and in its inferior part by the
hypothalamus, These two areas are separated from one
another by a shallow sulcus, the hypothalamic sulcus
The diencephalon can be divided into four major
parts:
(1) the thalamus,
(2) the subthalamus,
(3) the epithalamus,
(4) the hypothalamus
Inferior surface of the brain showing parts of the diencephalon
Sagittal section of
the brain showing
the medial
surface of the
diencephalon
Thalamus
a large ovoid mass of gray matter that forms the major part of the
diencephalon
It is a region of great functional importance and serves as a cell
station to all the main sensory systems (except the olfactory pathway)
-
The activities of the thalamus are closely related to that of the
cerebral cortex and damage to the thalamus causes great loss of
cerebral function
-
pulvinar: is the expanded posterior end of the thalamus
-
lateral geniculate body: a small elevation on the under aspect of the
lateral portion of the pulvinar
The thalamus contain many important nuclei that will be discussed in
future
As a relation,
superior surface
is covered medially by the tela choroidea and the fornix, and laterally, it
is covered by ependyma and forms part of the floor of the lateral
ventricle
The inferior surface is continuous with the tegmentum of the midbrain
medial surface of the thalamus
forms the superior part of the lateral wall of the third ventricle and is
usually connected to the opposite thalamus by a band of gray matter,
the interthalamic connection
lateral surface of the thalamus
is separated from the lentiform nucleus by the very important band of
white matter called the internal capsule
Function of thalamus
1- very important cell station that receives the
main sensory tracts (except the olfactory
pathway)
2- plays a key role in the integration of visceral
and somatic functions
Other functions will be discussed later
Subthalamus
inferior to the thalamus
between the thalamus and the tegmentum of the midbrain
craniomedially, it is related to the hypothalamus
Among the collections of nerve cells found in the subthalamus
are
- cranial ends of the red nuclei
- substantia nigra
- subthalamic nucleus involved in the control of muscle activity
- The subthalamus also contains many important tracts that
pass up from the tegmentum to the thalamic nuclei; the
cranial ends of the medial, spinal, and trigeminal lemnisci
are examples
Nuclei of the
thalamus
Epithalamus
-
consists of the habenular nuclei and their
connections and the pineal gland
Habenular Nucleus
small group of neurons situated just medial to
the posterior surface of the thalamus
Sagittal section
of the brain
showing the
medial
surface of the
diencephalon
Pineal Gland (Body)
a small, conical structure that is attached by the pineal
stalk to the diencephalon
-
Relations:
- dorsally by splenium of corpus callosum
- ventrally by midbrain
- sup, post part of 3rd ventricle
- inf, cerebellar vermis
- consist of pinealocytes and the glial cells
- Calcifications may be found normally at age of 16
- cysts may be found (pineal cyst)
Photomicrograph of a section of the pineal
gland stained with hematoxylin and eosin
Functions of the Pineal Gland
- an important endocrine gland capable of influencing the
activities of the pituitary gland. the islets of Langerhans
of the pancreas, the parathyroids, the adrenal cortex
and the adrenal medulla, and the gonads.
- Melatonin and the enzymes needed for its production are
present in high concentrations within the pineal gland
- pineal gland plays an important role in the regulation of
reproductive function
Hypothalamus
is that part of the diencephalon that extends from the
region of the optic chiasma to the caudal border of the
mammillary bodies
It lies below the hypothalamic sulcus on the lateral wall of
the third ventricle
Physiologically, there is hardly any activity in the body that
is not influenced by the hypothalamus
The hypothalamus controls and integrates the functions of
the autonomic nervous system and the endocrine
systems and plays a vital role in maintaining body
homeostasis. It is involved in such activities as
regulation of body temperature, body fluids, drives to eat
and drink, sexual behavior, and emotion
Relations of the Hypothalamus
Anterior to the hypothalamus: preoptic area
Caudally, the hypothalamus merges into the
tegmentum of the midbrain
Superiorly is the thalamus
Inferolaterally lies the subthalamic region
When observed from below, the hypothalamus is
seen to be related to the following structures,
from anterior to posterior: (1) the optic
chiasma, (2) the infundibulum and the tuber
cinereum, and (3) the mammillary bodies
Optic Chiasma
The optic chiasma
is a flattened
bundle of nerve
fibers situated
at the junction
of the anterior
wall and floor of
the third
ventricle
Tuber Cinereum
a convex mass of gray matter, as seen from the
inferior surface
It is continuous inferiorly with the infundibulum
Mammillary Bodies
two small hemispherical bodies situated side by
side posterior to the tuber cinereum
Ventricular cavities
of the brain.
A: Lateral view.
B: Superior view
Superior
view of the
cerebral
hemispheres
.
Lateral view of the right cerebral hemisphere
Lateral view of the right cerebral hemisphere
dissected to reveal the right insula
General Appearance of the Cerebral Hemispheres
the largest part of the brain; they are separated by a
deep midline sagittal fissure, the longitudinal
cerebral fissure
The fissure contains the sickle-shaped fold of dura
mater, the falx cerebri, and the anterior cerebral
arteries.
great commissure, the corpus callosum, connects
the hemispheres across the midline
A second horizontal fold of dura mater separates the
cerebral hemispheres from the cerebellum and is
called the tentorium cerebelli
To increase the surface area of the cerebral
cortex maximally, the surface of each cerebral
hemisphere is thrown into folds or gyri, which
are separated from each other by sulci or
fissures
each hemisphere are devided into lobes, which
are named according to the cranial bones
under which they lie.
The central, parieto-occipital, lateral and
calcarine sulci are boundaries used for the
division of the cerebral hemisphere into frontal,
parietal, temporal, and occipital lobes
Main Sulci
The central sulcus
(fissure of Rolanad) it begin aproximately midway between frontal and occopital pole
and terminates just above the lateral sulcus, separate between frontal and parietal,
motor (area 4) and sensory (area 1-3), precentral and postcentral gyrus
Clinically it is related to anterior (frontal) branch of the middle meningeal artery which is
important as a common site of injury during head trauma resulting in extradural
hematoma.
The lateral sulcus,
a deep cleft found mainly on the inferior and lateral surfaces of the cerebral
hemisphere, divides into the anterior horezontal ramus (anterior) and the anterior
ascending ramus (ascending) and continues as the posterior ramus
Anterir to the anterior horezontal ramus (anterior) is the pars orbitalis, between the
anterior horezontal ramus (anterior) and the anterior ascending ramus (ascending)
is the pars triangularis (motor speech area – brochas area), posterior to the anterior
ascending ramus (ascending) is pars opercularis
Clinically it is related to middle cerebral artery
An area of cortex called the insula lies at the bottom of the deep lateral sulcus and
cannot be seen from the surface unless the lips of the sulcus are separated
The parieto-occipital sulcus
begins on the superior medial margin of the hemisphere about
2 inches (5 cm) anterior to the occipital pole, It passes
downward and anteriorly on the medial surface to meet the
calcarine sulcus forming a Y shaped appearance
The calcarine sulcus
is found on the medial surface of the hemisphere
It commences under the posterior end of the corpus callosum
and arches upward and backward to reach the occipital pole
The calcarine sulcus is joined at an acute angle by the parietooccipital sulcus
Superior view of
the cerebral
hemispheres
Lateral view of the right cerebral hemisphere
Lateral view of the right cerebral hemisphere
Lateral view of the
right cerebral
hemisphere
showing the main
sulci. B: Medial
view of the right
cerebral
hemisphere
showing the main
sulci.
Lobes of the Cerebral Hemisphere
The frontal lobe
occupies the area anterior to the central sulcus and superior to the lateral sulcus
(precentral gyrus , superior frontal gyrus , middle frontal gyrus and inferior frontal gyrus )
The parietal lobe
occupies the area posterior to the central sulcus and superior to the lateral sulcus; it
extends posteriorly as far as the parieto-occipital sulcus
(postcentral gyrus, superior parietal lobule (gyrus), and the inferior parietal lobule
(gyrus).)
The superior and inferior parietal gyri are separated by the intra-parietal sulcus
The temporal lobe
occupies the area inferior to the lateral sulcus, superior and middle (inferior) temporal
sulcus devide the lobe into superior, middle, and inferior temporal gyri
The occipital lobe the occipitotemporal sulcus forms the medial and lateral
occipitotemporal gyri (on the inferior surface of the cerebrum)
The occipital lobe contain the lunate sulcus (behind which is the visual area –area 17)
on superolateral sulcus
Medial and Inferior Surfaces of the Hemisphere
many important areas that should be recognized
The corpus callosum, which is the largest commissure of
the brain, forms a striking feature on this surface
cingulate gyrus begins beneath the anterior end of the
corpus callosum and continues above the corpus
callosum until it reaches its posterior end, The gyrus is
separated from the corpus callosum by the callosal
sulcus. The cingulate gyrus is separated from the
superior frontal gyrus by the cingulate sulcus
Inferior surface of the frontal lobe (orbital surface) devided
by orbital sulci (H- shaped sulci) into anterior orbital,
posterior orbital, lateral orbital and medial orbital gyei
Medial view of the cerebral hemisphere
The precuneus:
is an area of cortex bounded anteriorly by the upturned posterior end of
the cingulate sulcus and posteriorly by the parieto-occipital sulcus
The cuneus:
is a triangular area of cortex bounded above by the parieto-occipital
sulcus, inferiorly by the calcarine sulcus, and posteriorly by the
superior medial margin.
The collateral sulcus
is situated on the inferior surface of the hemisphere. It runs anteriorly
below the calcarine sulcus.
lingual gyrus
Between the collateral sulcus and the calcarine sulcus.
Anterior to the lingual gyrus is the parahippocampal gyrus; the latter
terminates in front as the hooklike uncus