anatomyphysiologyblog - Cranial Dura Mater together with Dural Venous Sinuses
Objectives:
Describe the features (and reflections/foldings) of cranial dura mater.
Describe the intracranial dural venous sinuses.
The encephalon is covered from exterior inwards past times iii meningeal layers namely
i) Dura mater
ii) Arachnoid mater as well as
iii) Pia mater.
Dura Mater:
It is tough as well as consists of
outer endosteal/periosteal layer which serves as inner periosteum (covering within of the bones that cast the calvaria of skull) as well as
inner meningeal layer which is a rigid fibrous membrane that is continuous at the foramen magnum amongst the spinal dura mater roofing the spinal cord.
The meninegeal layer is fused amongst the endosteal layer all over except where it projects inwards inwards the cast of 4 folds – falx cerebri, tentorium cerebella, falx cerebella as well as diaphragm sellae.
Reflections of (cranial) dura mater
The internal meningeal layer of dura mater is a supporting layer that reflects away from the external endosteal/periosteal layer of dura to cast dural infoldings (reflections). The dural infoldings include:
Cerebral falx (Latin –falx cerebri)
Cerebellar tentorium (L. tentorium cerebelli)
Cerebellar falx (L. falx cerebelli)
Sellar diaphragm (L. diaphragmasellae)
The cerebral falx (L. falx, a sickle-shaped structure), the largest dural infolding, lies inwards the longitudinal cerebral cleft that separates the correct as well as left cerebral hemispheres.
Attaches inwards the median plane to the internal surface of the calvaria as
Anteriorly - the frontal crest of the frontal os as well as crista galli of the ethmoid os
Posteriorly - the internal occipital protuberance
It ends past times becoming continuous amongst the cerebellar tentorium.
The cerebellar tentorium, is a broad crescent shaped septum that separates the occipital lobes of the cerebral hemispheres from the cerebellum.
Attachments –
Rostrally to the clinoid processes of the sphenoid,
Rostrolaterally to the petrous purpose of the temporal bone, as well as
Posterolaterally to the internal surface of the occipital as well as purpose of the parietal os
The cerebral falx attaches to the cerebellar tentorium as well as holds it up, giving it a tent-like appearance (L. tentorium, tent). The cerebellar tentorium divides the cranial cavity into supratentorial as well as infratentorial compartments.
The cerebellar falx is a vertical dural infolding that lies inferior to the cerebellar tentorium inwards the posterior purpose of the posterior cranial fossa.
It is attached to the internal occipital crest as well as partially separates the cerebellar hemispheres.
The sellar diaphragm, the smallest dural infolding, is a circular canvass of dura that is suspended betwixt the clinoid processes forming a partial roof over the hypophysial fossa inwards the sphenoid bone. The sellar diaphragm covers the pituitary gland inwards this fossa as well as has an aperture for passage of the infundibulum as well as hypophysial veins.
Intracranial dural venous sinuses
The dural venous sinuses are endothelium-lined spaces betwixt the endosteal as well as the meningeal layers of the dura except the inferior as well as straight sinuses which social club alone within the plication of meningeal layer.
Large veins from the surface of the encephalon empty into these sinuses as well as almost of the blood from the encephalon ultimately drains through them into the internal jugular veins. The dural venous sinuses are:
Unpaired Paired
Superior sagittal Transverve
Inferior sagittal Sigmoid
Straight Cavernous
Occipital superior petrosal
Anterior intercavernous Inferior petrosal
Posterior intercavernous spheno-parietal
Basilar venous plexus petro-squamous
Middle meningeal
1) The superior sagittal sinus lies inwards the convex attached edge of the cerebral falx. It begins at the crista galli as well as ends close the internal occipital protuberance at the confluence of sinuses, a coming together house of the superior sagittal, straight, occipital, as well as transverse sinuses.
The superior sagittal sinus receives the superior cerebral veins as well as communicates on each side through slit-like openings amongst the lateral venous lacunae.
2) The inferior sagittal sinus runs inwards the inferior concave gratuitous edge of the cerebral falx as well as ends inwards the straight sinus.
3) The straight sinus (L. sinus rectus) is formed past times the spousal human relationship of the inferior sagittal sinus amongst the peachy cerebral vein. It runs inferoposteriorly along the trouble of attachment of the cerebral falx to the cerebellar tentorium, where it joins the confluence of sinuses.
4) The transverse sinuses operate past times laterally from the confluence of sinuses, coursing along the posterolateral attached margins of the cerebellar tentorium as well as and then decease the sigmoid sinuses. Blood received past times the confluence of sinuses is drained past times the transverse sinuses, but rarely equally. Usually the left sinus is larger.
5) The sigmoid sinuses follow S-shaped courses inwards the posterior cranial fossa, forming deep grooves inwards the temporal as well as occipital bones. Each sigmoid sinus turns anteriorly as well as and then continues inferiorly as the Internal Jugular Vein.
6) The occipital sinus lies inwards the attached edge of the cerebellar falx as well as ends superiorly inwards the confluence of sinuses. It communicates inferiorly amongst the internal vertebral venous plexus.
7) The cavernous sinus is located on each side on the upper surface of the trunk of the sphenoid. The cavernous sinus consists of a venous plexus of extremely thin-walled veins that extends from the superior orbital cleft anteriorly to the apex of the petrous purpose of the temporal os posteriorly. It receives blood from the superior as well as inferior ophthalmic veins, superficial middle cerebral vein, as well as sphenoparietal sinus. The venous channels inwards these sinuses communicate amongst each other through venous channels anterior as well as posterior to the stem of the pituitary glands - the intercavernous sinuses as well as sometimes through veins inferior to the pituitary gland. The cavernous sinuses drain posteroinferiorly through the superior as well as inferior petrosal sinuses as well as emissary veins to the pterygoid plexuses.
The structures passing through the cavernous sinus:
Inside each cavernous sinus is the internal carotid artery amongst its little branches, surrounded past times the carotid plexus of sympathetic nerve(s), as well as the abducent nervus (CN VI) . The oculomotor (CN III) as well as trochlear (CN IV) nerves, addition 2 of the iii divisions (ophthalmic as well as maxillay) of the trigeminal nervus (CN V) are embedded inwards the lateral wall of the sinus.
8) The superior petrosal sinuses run from the posterior ends of cavernous sinus to the transverse sinuses. Each superior petrosal sinus lies inwards the anterolateral attached margin of the cerebellar tentorium, which attaches to the superior edge (crest) of the petrous purpose of the temporal bone.
9) The inferior petrosal sinuses as good commence at the posterior terminate of the cavernous sinus inferiorly. Each inferior petrosal sinus runs inwards a groove betwixt the petrous purpose of the temporal os as well as the basilar purpose of the occipital bone. The inferior petrosal sinuses drain the veins of the lateral cavernous sinus straight into the rootage of the IJVs.
10) The basilar plexus connects the inferior petrosal sinuses as well as communicates inferiorly amongst the internal vertebral venous plexus.
REFERENCES:
Following resources are used spell preparing this postal service (readers are strongly recommended to decease through them for to a greater extent than details):
Gray's Anatomy
K. L. Moore's Clinically Oriented Anatomy
R. Snell's Clinical Anatomy