Neuro Anatomy
Lec.1 د.عبد الجبار الحبيطيThe meninges: -
Three membranes cover the brain & the spinal cord. They are arranged as outer dura, and then arachnoid & inner layer is the pia mater. The cranial dura mater is formed of two layers, an endosteal & Meningeal (the dura of the spinal cord is only one layer). The two layers are firmly fused together, except at certain sites where they separate to enclose between them venous sinuses.The inner layer of dura is thick, fibrous, tough & strong, being stretched at certain places to form the dural folds (4 in number) they divided the intracranial cavity into a freely communicating compartment, which contain the different parts of the brain.
These folds are: -
Falx cerebri: -
Is sickle shaped fold occupying the median longitudinal cerebral fissure, between the two cerebral hemispheres, its pointed anterior end attaches to crista galli & internal frontal crest, while its broad posterior extremity fuses with the superior layer of tentorium cerebelli. The flax cerebri has an outer fixed convex border related to the inner aspect of sagittal suture, while its inner border is free & related to corpus callosum (which connects the two cerebral hemisphere) at the bottom of the cerebral fissure.
The flax cerebri enclose three venous sinuses: -
Superior sagittal sinus: - on the fixed outer border of flax cerebri.
Inferior sagittal sinus: - on the inner free border of flax cerebri.
Straight (rectus) sinus: - along the line of fusion of posterior extremity of flax cerebri & tentorium cerebella.
Tentorium cerebelli: -
Is a tent shaped fold which roofs the posterior cranial fosse & its contents; it separates the superior surface of the cerebellum from inferior surface of the occipital lobe of cerebrum. It has two borders (attached & free). The attached border, extend from the posterior clinoid process, apex of the petrous bone, border of petrous bone & along the groove for the transverse sinus on the circumference of the occipital bone on each side. The free border is U shaped & surround the mid brain, it is called the tentorial hiatus (tentorial notch), the two ends of the U cross the fixed part at posterior clinoid process on each side to be affixed at the anterior clinoid process, between the two parts, there is a slit like gap for the passage of occulomotor & trochlear nerves to reach the cavernous sinus on their way to the superior orbital fissure.
Three venous sinuses are enclosed within the tentorium cerebelli includes: -
Rectus (straight) sinus.
Superior petrosal sinus: - on the attached border of petrous bone (superior petrosal sulcus).
Transverse sinus: - lies in the attached border in the groove for transverse sinus on the circumference of occipital bone from inside.
Falx cerebelli: -
Is a small median fold attached to the internal occipital crest & fuses to the inferior layer of tentorium cerebelli, it indents the cerebellum from behind between the two cerebellar hemispheres, it encloses the occipital venous sinus.
Diaphragma sellae: -
Is a circular fold that roofs the sella turcica (as a diaphragm) where it covers the pituitary gland. It is perforated at its center by the infundibulum (pituitary stalk) which connects the pituitary gland to the hypothalamus. The diaphragma sellae enclose the anterior & posterior intercavernous sinuses.
The dura mater of spinal cord is separated from the wall of the vertebral canal by the epidural (extradural) space & from the arachnoid mater by subdural space. It is attached to the following areas: -
Circumference of foramen magnum.
Bodies of 2nd & 3rd cervical vertebrae.
Back of the coccyx.
Intervertebral foramina (loose attachment).
Posterior longitudinal ligament (loose attachment).
The spinal dura mater tube is continuous above with the cranial dura mater & ends below at the 2nd sacral vertebra where it forms a sheath around the filum terminale.
It sends sleeves around the roots of the spinal nerves as they approach the intervertebral foramina. The epidural space lies between it & the wall of the vertebral canal. It contain: -
Loose areolar tissue.
Internal vertebral plexus of veins.
Fine arterial branches.
Venous sinuses: -
These are venous spaces present either between the outer & inner layers of the dura mater or within the meningeal layer only (i.e related to folds of the dura). They receive the venous blood from the brain, meninges & diploi veins of skull bones & drain them eventually in to the bulb of the internal jugular veins. They possess no valves they include singled & paired sinuses.
Paired sinuses include: -
Spheno parietal: - related to the lesser wing of sphenoid.
Cavernous sinus: - on either side of body of sphenoid, extending from medial end of S.O.F to the apex of the petrous bone.
Superior petrosal sinus (S.P.S): - on the upper border of petrous bone.
Inferior petrosal sinus (I.P.S): - runs on the petro occipital sulcus.
Transverse sinus: - runs transversely from internal occipital protuberance in a groove within the circumference of the occipital bone.
Sigmoid sinus (S- shaped): - starts at the base of the petrous temporal bone, as a continuity of the transverse sinus.
Singled sinuses include: -
Superior sagittal sinus (S.S.S): - on the convex, outer fixed margin of the falx cerebri.
Inferior sagittal sinus (I.S.S): - on the inner, free border of falx cerebri.
Straight (rectus) sinus: - at the line of fusion of broad posterior end of falx cerebri with the superior layer of tentorium cerebelli.
Occipital sinus: - in the attached margin of falx cerebelli at the internal occipital crest. It communicates with the internal vertebral venous plexus (in the vertebral canal) & also communicates with the confluence of sinuses at the internal occipital protuberance.
Confluence of venous sinuses.
Basilar venous plexus.
The cavernous sinus: -
It contains the following structures: -
Within the lumen: -
Internal carotid artery.
Internal carotid sympathetic plexus.
Abducent nerve.
On the wall of the cavernous sinus: -
Occulomotor nerve.
Trochlear nerve.
Ophthalmic division of trigeminal nerve.
Maxillary division of trigeminal nerve.