## Superior sagittal sinus
Position
<ul>
 <li>Between the inner dura and the outer endosteum</li>
 <li>Begins above the foramen caecum</li>
 <li>Runs between the layers of the falx cerebri, backwards, and grooves the skull vault</li>
 <li>Deviates at the internal occipital protuberance</li>
 <ul>
 <li>
 Becomes continuous with the transverse sinus on whichever side it deviates too (typically the
 right)
 </li>
 <li>There is a slight dilation at this joining of the sinuses</li>
 </ul>
</ul>
Functions
<ul>
 <li>Drains the upper surface of the cerebral hemispheres&nbsp;</li>
 <li>Receives the superior cerebral veins</li>
 <li>Contains arachnoid villi through which CSF is absorbed into the bloodstream</li>
 <ul>
 <li>
 NB: the rate of CSF production is independent of intracranial pressure across the normal range
 but the rate of absorption is dependent on ICP
 </li>
 </ul>
</ul>
## Inferior sagittal sinus
<ul>
 <li>At the lower free margin of the falx cerebri</li>
 <li>Travels backwards to join the great cerebral vein</li>
 <li>Together they form the straight sinus&nbsp;</li>
</ul>
Function
<ul>
 <li>Drains the lower parts of the medial surface of each hemisphere</li>
</ul>
## Straight sinus
<ul>
 <li>Formed by inferior sagittal sinus and great cerebral vein (of Galen)</li>
 <ul>
 <li>Also receives the left and right basilar veins</li>
 </ul>
 <li>Runs backwards to drain into the transverse sinus (usually the left)</li>
</ul>
## Transverse sinus
<ul>
 <li>Paired structure</li>
 <li>Lies between the inner dura and outer endosteum</li>
 <li>
 As above, the right is usually continuous with the superior sagittal sinus and the left with the
 straight sinus
 </li>
</ul>
## Sigmoid sinuses
<ul>
 <li>Continuations of the transverse sinuses</li>
 <li>Grooves the mastoid part of the temporal bone</li>
</ul>
<ClinicalCorrelate>
 
 Their proximity to the mastoid air cells means mastoiditis can lead to thrombosis in the sinus
 
</ClinicalCorrelate>
<ul>
 <li>Become continuous with the internal jugular vein</li>
 <li>The internal jugular</li>
 <ul>
 <li>Separated from the sympathetic chain by the prevertebral fascia</li>
 <li>Lies anterolateral to the sympathetic chain</li>
 <li>Separated from the inferior petrosal sinus by the 9th, 10th and 11th cranial nerves</li>
 </ul>
</ul>
## Occipital sinus
<ul>
 <li>A small sinus at the margin of the falx cerebri</li>
</ul>
## Cavernous sinus
Position
<ul>
 <li>
 In the middle cranial fossa on each side of the body of the sphenoid and the sella turcica&nbsp;
 </li>
 <li>
 Extends from the superior orbital fissure anteriorly to the apex of the temporal bone
 posteriorly
 </li>
 <li>The interior is crossed by trabeculae</li>
 <li>Formed by layers of dura</li>
 <li>Internal carotid with sympathetic plexus and abducens nerve run along the floor</li>
 <li>
 CNs III, IV, V1 and V2 run in the lateral wall (in that order from top to bottom) between the
 endothelial lining and the dura
 </li>
</ul>
Functions
<ul>
 <li>Receives</li>
 <ul>
 <li>Superior ophthalmic vein</li>
 <li>Inferior ophthalmic vein (but this usually drains directly into superior)</li>
 <ul>
 <li>
 NB: the facial veins indirectly communicate with the sinuses via the superior and inferior
 ophthalmic veins
 </li>
 </ul>
 <li>Sphenoparietal sinus</li>
 <li>Inferior and superficial middle cerebral veins</li>
 </ul>
 <li>
 Drains into the superior and inferior petrosal sinuses posteriorly and the pterygoid venous
 plexus inferiorly.
 </li>
</ul>
<Note>
 
 There are no valves in this venous system so the direction of blood flow depends purely on
 pressure gradients
 
</Note>

Superior sagittal sinus Position Between the inner dura and the outer endosteum Begins above the foramen caecum Runs between the layers of the falx…

Neuroanatomy

Venous Sinuses

Intro

FRCOphth Part 1 Study Notes

Orbit and ocular adnexae

Orbit

Extraocular Muscles

Orbital Blood Vessels

Paranasal Sinuses

Lacrimal Glands

Tear Film

Eyelids

Blinking

Anterior segment - ocular surface

Conjunctiva

Conjunctivitis

Sclera

Cornea

Corneal Structure And Development

Corneal Physiology

AC to Lens

Angle

Ciliary Body

Aqueous Humour Dynamics

Iris

Pupil

Lens

Posterior segment

Choroid

Vitreous

Retinal Macrostructure

Neurosensory Retina

Retinal Pigment Epithelium

Cerebral Ventricles

Cerebral Blood Supply

Supranuclear Gaze Pathways

Head And Neck Autonomic Nervous Supply

Head And Neck Glands

Osteology

Nerves

Muscles And Pharyngeal Arches

Extraocular Nerves

Sensory Nerves

Physiology

Physics Of Blood Flow

Neuronal Control Of Blood Vessels

Oxygen-Haemoglobin Dissociation Curve

Cytochrome p450

Pituitary Gland

Thyroid Hormone Production

Insulin

Glucagon

Parathyroid Hormone

Corticosteroids

Catecholamines

Cardiac Cycle

Renal Physiology

Fluid Balance

Acid-Base Balance

Muscle Physiology

Sensory Fibres

Cutaneous Receptors

Endocytosis

Glycosaminoglycans

Condensed Ocular Biochemistry

Eye Movements

Accomodation

Vision

Visual Cycle And Phototransuction

Visual Pathway

Visual Acuity

Colour Vision

Binocular Vision

Pathology

Collagen

Tissue Damage

Inflammation

Disease Entities

Wound Healing

Thrombosis / Atherosclerosis

Cell Growth

Neoplasia

Histopathology

Nystagmus

Free Radicals And Antioxidants

Immunology

Ocular Immunology

Microbiology

Viral Infections

Bacterial Infections

Fungal Infections

Protozoa

Nematodes

Antimicrobials

Genetics

Chromosomes

Mitosis

Meiosis

Genes

Polypeptide Synthesis

Histones

MicroRNA

Hardy-Weinberg Equilibrium

Mutations

Chromosome Defects

Autosomal Inheritance

X-Linked Inheritance

Mitochondrial Inheritance

Multifactorial Inheritance