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Reminder of what you should know!
Thursday, February 25,, 2010
Suzanne S. Stensaas, Ph.D.
EMBRYOLOGY, VENTRICLES, CSF and VASCULAR SUPPLY
Note on the objectives: it is not the intent of this course to cover all the objectives during
lecture. Reading outside of class is required. The purpose of the objectives is to guide
your studying or focus your attention on the important content and concepts that you
will be tested on.
Objectives:
1. Describe where CSF is produced and how it circulates and is removed
including the venous drainage.
2. Name the most likely sites of obstruction of CSF circulation and the
consequences.
3. Explain what the meninges cover and what spaces they surround?
4. What is meant by anterior and posterior circulation? What are the
consequences of a thrombotic event in one or the other?
I.
THE CENTRAL NERVOUS SYSTEM DEVELOPMENT.
A. Embryological Divisions of neural tube into 3 vesicles and then 5 vesicles. The
center of the tube is the neural canal and it will become the ventricular system.
Quick review of neural tube closure and the creation of:
1.
Rhombencephalon (Hindbrain)
a. Myelencephalon (Medulla older term the "bulb")
b. Metencephalon (Pons and Cerebellum)
2.
Mesencephalon (Midbrain)
3.
Prosencephalon (Forebrain)
a. Diencephalon (Thalamus, Hypothalamus, Pineal, Eye, Posterior lobe
pituitary)
b. Telencephalon (Basal Ganglia, Olfactory Bulb, and Cerebral Cortex)
B. Brain Stem = Medulla, Pons, Midbrain = Rhombencephalon+Mesencephalon
(Image: John Sundsten )
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II. THE VENTRICLES
The importance of the ventricles as an internal structure to relate other structures to. A
very obvious internal landmark. Try to visualize them and rotate them within the
brain. Ventricles are a very obvious internal landmarks. They will form the “wire
frame” for our orientation to the brain. Rotating holograms can be found at
http://library.med.utah.edu/diganat/neuroanat/
Drawing by David Morton, PhD, University of Utah ©
A.
B.
C.
D.
Lateral Ventricles - names of regions related to overlying cortical
lobes/bones. Associated with the hemispheres.
Third Ventricle –boundaries of the “box” best studied from midsagittal
section, which we will do in Lab 2 (=HyperBrain Ch 2). Think of it as a
narrow slit trapped between the two halves of the brain with many nooks and
crannies. This ventricle is associated with the thalamus and hypothalamus.
Aqueduct associated with midbrain = mesencephalon
Fourth Ventricle associated with the pons and medulla. It terminates
at the caudal portion of medulla. Is normally closed and does not
extend into the spinal cord. Ependymal cells line all parts of the
ventricular system. There are ependymal cells in the spinal cord; they
line the remnants of the neural canal. The canal is not open in the cord.
Some textbooks are misleading.
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III. THE PRODUCTION, CIRCULATION, AND RESORPTION OF CSF
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Drawings by David Morton, PhD, University of Utah ©
A. Sites of production: Choroid Plexus (lateral ventricles, III ventricle, IV ventricle,
lateral recess of the IV ventricle). 450-600 cc/day. Ventricles hold 150 cc with
another 75 cc in the cisterns and 50 in the subarachnoid space (=275 cc)..
B. “Circulation” of CSF, refer to diagram
C. Communication between ventricles and subarachnoid space in region of medulla
1. Lateral Aperture = Luschka
2. Median Aperture = Magendie
D. Cisterns (wells) such as cisterna magna, quadrigeminal, and cerebellopontine
angle cisterns are pools of CSF and so have been given names. All are
continuous with the subarachnoid space. You need not memorize their names.
E. CSF returns to the venous system (no lymphatics)
a. Arachnoid granulations
b. Sinuses particularly the superior sagittal
F. Function: Flotation, buoyancy protection, and constant milieu.
G. Obstruction of ventricles, aqueduct, lateral and median apertures,
subarachnoid space and arachnoid granulations result in:
1. Communicating (non-obstructive) hydrocephalus with blockage in
Subarachnoid Space or granulations.
2. Non-communicating (obstructive hydrocephalus) with blockage in
ventricular system.
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IV. THE CEREBRAL VASCULATURE
Drawings by David Morton, PhD, University of Utah ©
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V. COVERINGS AND SPACES- MENINGES
Suzanne S. Stensaas ©
Dura mater surrounding spinal cord
1. Dura
2. Leptomeninges: Arachnoid and Pia
Leptomeninges (=pia+arachnoid) thin and glistening. CSF gone and subarachnoid
space collapsed after removal from cranium. The small vessels run between the two
layers.
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VI. Major Planes and Terminology
Sagittal Plane
Frontal
Coronal
(Coronal)
Plane
Plane
Dorsal
Superior
Rostral
Rostral
Frontal
Anterior
Caudal
Caudal
Occipital
Posterior
Ventral
Inferior Superior
Posterior
Dorsal
Anterior
Ventral
Rostral
Midbrain
Pons
Medulla
Spinal Cord
Caudal
Caudal
Inferior
Transverse
PlanePlane
Axial (Horizontal)
Transverse plane as used by neuroanatomists means perpendicular to the long axis
of the CNS, i.e. coronal in the cerebrum and axial in the spinal cord.
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