Before you start reading this sheet I would like to notify you with the following :
 numbers of pages I referred to in the sheet are from GRANTS atlas of anatomy (twelfth
edition ) it show some structures we are talking about .
IN THE NAME OF GOD
As in the case of spinal cord the brain is also protected by several means or by several
layers, those are the following :
1.bony skull (bony cranium) :
Recall that the spinal cord is also present inside a bony canal which is termed the
vertebral canal.
2.the three layers of
meninges :
The meninges surround the brain and extend down through foramen magnum to
surround the spinal cord as well. the three layers from out to in are :
A. Dura mater
B. arachnoid mater
C. pia matter (inner-most)
3. CSF (cerebrospinal fluid):
The CSF is present inside the CNS within several spaces:
1. subarachnoid space : Which is the space between arachnoid and pia mater
2. central canal **
3. ventricles
The following was not mentioned in the recording :
Wikipedia: The central canal is the cerebrospinal fluid-filled space that runs
longitudinally through the length of the entire spinal cord. The central canal is
contiguous with the ventricular system of the brain.
-so the central canal is not present inside the brain but only in the spinal cord
and it was mentioned above as one of the spaces that contain the CSF not as
one of the spaces inside the brain.
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Dura mater and it’s fold
it is one of the meninges, it has several parts or folds: (page 638 A)
A. FALX CEREBRI: a Sickle shaped part (or fold) of Dura mater that separates the
two hemispheres of the cerebrum , it passes through the longitudinal fissure **
B_ called FALX CEREBELLI: a part (or a fold) of Dura mater that separates the two
hemispheres of the cerebellum .
C_TENTORIUM CEREBELLI: a tent shaped fold of Dura mater that separates the
two cerebral hemispheres (anteriorly) and the cerebellum (inferiorly and
posteriorly
**The following was not mentioned in the recording
Wikipedia: longitudinal cerebral fissure, or longitudinal fissure, or interhemispheric
fissure) is the deep groove which separates the two hemispheres of the vertebrate
brain. The falx cerebri, a Dural brain covering, lies within the medial longitudinal
fissure.
Google: the arrows are pointing at the longitudinal fissure:
-Anterior view -
-Superior view-
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Major parts of brain:
1-cerebrum (largest part)
2-brain stem
3-cerebellum
4-diencephalon
Cerebrum
-largest part of the brain
-located within anterior and middle cranial fossa
(recall: cerebellum is located within the posterior cranial fossa )
-a coronal section in the brain will show that the outer layer of cerebrum is composed
of gray mater (the CEREBRAL CORTEX) and the interior of the cerebrum is composed
of white mater (CORE of the brain) (page 731 A)
-ventricles: spaces inside the brain, full of CSF (cerebrospinal fluid), these spaces are
divided into three ventricles:
1. Lateral ventricles: (page 724 B)
-are two in number (page 724 A)
-the two ventricles communicate with each other’s
-one is located in the right side and the other is in the left side (one is
in the right hemisphere and one is in the left hemisphere)
The 3rd ventricle.
-C shaped cavity , one in each hemisphere
-Divided into body, anterior, posterior , and inferior horns.
-the body is located inside the parietal lobe .
-anterior horn: located inside the frontal lobe
-Posterior horn: located inside the occipital lobe
-Inferior horn: located inside the temporal lobe
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2. Third ventricle. (Page 723 D)
-is a slit like cleft or cavity between the two thalami
-Recall: - the major part of diencephalon is the thalamus
-thalamus is an egg shaped gray mater present in both hemispheres
-one thalamus in each hemisphere
-thalami communicate through inter-thalamic communication
-inter-thalamic communication or adhesion is composed of white mater
-between the two thalami there is a space through which passes the inter-thalamic
connection this I space is the THIRD VENTRICLE.
-Third ventricle has communications with lateral ventricles and the fourth ventricle
** the following is not related the 3rd ventricle but it was mentioned here in the
recording :
-There is a communication between the central canal and the fourth ventricle
-CSF is not static but rather is dynamic; that is it has a circulation:
-From lateral ventricle → to 3rd ventricle → to 4th ventricle → to central canal
-So all the above communicate with each other’s.
Regarding The next topic communications and boundaries of third ventricle it’s really
recommended that you study the information while looking at a figure (you can use
figure D page 723):
-note: what we see is a mid-sagittal section so you can see one thalamus only
Boundaries of the (THALAMUS):
Anterior –inferior : hypothalamus (the 2nd part of diencephalon)
Medial : 3rd ventricle
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Boundaries of the ( 3rd VENTRICLE ):
-Anterior boundary: anterior commissure (considered as commissural fibers, to be
discussed later in this lecture)
Anterior commissure is part of the commissural fibers which are part of the white
mater of cerebrum that connect different parts of the cortex together ,and in the case
of the anterior commissure it connects the two temporal lobes of the cerebral cortex
(more details are mentioned later).
-Posterior boundaries:
1-the duct that connects the 3rd ventricle with the 4th ventricle
2-above the duct there is the posterior commissure
3-above the posterior commissure there is the pineal gland
4-above the pineal gland there is the habenular commissure or habenular nucleus
-Superior boundaries:
1-Choroid plexus: a plexus in the roof of the 3rd ventricle that secretes CSF
2-superior to the plexus there is the FORNIX
3-superior to the fornix there is corpus callosum
the CSF inside the 3rd ventricle is secreted by:
1- EPINDULAR cells found in the roof of the 3rd ventricle
2-choroid plexus
-Inferior boundaries:
1-optic chiasm: related to optic nerve (to be discussed later)
2-posterior part of pituitary gland
3-mammillary bodies
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Lateral boundaries from both sides :
1-superiorly: thalamus
2-inferiorly: hypothalamus
.so: superior part of lateral wall is formed by the thalamus and inferior part of the lateral wall
is formed by the hypothalamus
Communications of the 3rd ventricle: (page 724 A )
-3rd ventricle communicates anteriorly with lateral ventricle through the INTER-VENTRICULAR
FORAMENA or FORAMEN OF MONRO (after the scientist who discovered it )
- posteriorly with fourth ventricle through a small duct called AQUEDUCT OF
MIDBRAIN(because it pass through the midbrain), other names of this duct:
1- CEREBRAL AQUEDUCT(related to cerebrum)
2- MESENCEPHALIC AQUEDUCT
3- AQUEDUCT OF SYLVIUS (after the scientist who discovered it)
(Aque-): because it contains CSF; which is an aqueous material
A student: how can we differentiate between boundaries of 3rd ventricle and
boundaries of diencephalon ?
Dr.3alia :We can’t separate the 3rd ventricle from diencephalon ,next week when we
talk about diencephalon You will see that it’s defined as : the structures surrounding
3- 4th ventricle :
-diamond in cross section
-located within the Pons and upper part of medulla
-CSF inside the 4th ventricle will continue down to reach the central canal inside the
spinal cord
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White mater inside the cerebrum ( the core of cerebrum) is composed of myelinated
axons along with neuralgia cells (glial cells) the white mater is divided into the
following according to their functions:
1-commissural tracts
2-association tracts
3-projecection tracts
commissural tracts :
-tracts or fibers (collection of axons) that connect the corresponding regions of the
two hemispheres
Examples:
1.corpus callosum: (the largest commissural tract) connects the two hemispheres
2.anterior commissure: connects the right temporal lobe to the left temporal lobe
3.posterior commissure
4.habenular commissure : connection between the two habenular nuclei in each side
5.fonix:
- it has more than one part
-it’s body of the fornix is located at the under surface of corpus callosum
-between the fornix and corpus callosum there is a membrane called septum pellucidum
-septum pellucidum: is a membrane composed of white mater and gray mater stretched between
Body of fornix and corpus callosum ,it also separates the anterior horns of the lateral ventricles
-connects the right hippocampus and the left hippocampus .
association tracts:
-fibers or tracts that connect different parts of the cortex in the same hemisphere
-for example : connect the frontal area and temporal area in the same hemisphere
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-Association vs. Commissural fibers:
Commissural fibers: connect corresponding regions (same regions) in the two
hemispheres
Association fibers: connect different regions of the cortex in the same
hemisphere .
Projection tracts:
-fibers that originate from different parts of brain stem (midbrain, Pons , and medulla
oblongata )
-it connect the brain stem to all regions in the cerebral cortex (of left and of right
hemispheres)
-it will pass through all the areas in the hemisphere to go be inserted in the cortex
-examples: CORONA RADIATA and INTERNAL CAPSULE
DONE BY NOURA ODEH
BEST OF LUCK ^_^
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