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The superior
petrosal sinus (sinus petrosus superior) (Fig. 570)
small and narrow, connects the cavernous with the transverse
sinus. It runs lateralward and backward, from the posterior end
of the cavernous sinus, over the trigeminal nerve, and lies in
the attached margin of the tentorium cerebelli and in the
superior petrosal sulcus of the temporal bone; it joins the
transverse sinus where the latter curves downward on the inner
surface of the mastoid part of the temporal. It receives some
cerebellar and inferior cerebral veins, and veins from the
tympanic cavity. |
| The inferior petrosal sinus (sinus petrosus
inferior) (Fig. 570) is situated in the inferior petrosal
sulcus formed by the junction of the petrous part of the
temporal with the basilar part of the occipital. It begins in
the postero-inferior part of the cavernous sinus, and, passing
through the anterior part of the jugular foramen, ends in the
superior bulb of the internal jugular vein. The inferior
petrosal sinus receives the internal
auditory veins and also veins from the medulla oblongata, pons,
and under surface of the cerebellum. |
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| The exact relation of the parts to one another in the
jugular foramen is as follows: the inferior petrosal sinus lies
medially and anteriorly with the meningeal branch of the
ascending pharyngeal artery, and is directed obliquely downward
and backward; the transverse sinus is situated at the lateral
and back part of the foramen with a meningeal branch of the
occipital artery, and between the two sinuses are the
glossopharyngeal, vagus, and accessory nerves. These three sets
of structures are divided from each other by two processes of
fibrous tissue. The junction of the inferior petrosal sinus with
the internal jugular vein takes place on the lateral aspect of
the nerves. |
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| The basilar plexus (plexus basilaris; transverse
or basilar sinus) (Fig. 571) consists of several interlacing
venous channels between the layers of the dura mater over the
basilar part of the occipital bone, and serves to connect the
two inferior petrosal sinuses. It communicates with the anterior
vertebral venous plexus. |
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| Emissary Veins (emissaria).—The emissary veins
pass through apertures in the cranial wall and establish
communication between the sinuses inside the skull and the veins
external to it. Some are always present, others only
occasionally so. The principal emissary veins are the following:
(1) A mastoid emissary vein, usually present, runs through the
mastoid foramen and unites the transverse sinus with the
posterior auricular or with the occipital vein. (2) A parietal
emissary vein passes through the parietal foramen and connects
the superior sagittal sinus with the veins of the scalp. (3) A
net-work of minute veins (rete canalis hypoglossi)
traverses the hypoglossal canal and joins the transverse sinus
with the vertebral vein and deep veins of the neck. (4) An
inconstant condyloid emissary vein passes through the condyloid
canal and connects the transverse sinus with the deep veins of
the neck. (5) A net-work of veins (rete foraminis ovalis)
unites the cavernous sinus with the pterygoid plexus through the
foramen ovale. (6) Two or three small veins run through the
foramen lacerum and connect the cavernous sinus with the
pterygoid plexus. (7) The emissary vein of the foramen of
Vesalius connects the same parts. (8) An internal carotid plexus
of veins traverses the carotid canal and unites the cavernous
sinus with the internal jugular vein. (9) A vein is transmitted
through the foramen cecum and connects the superior sagittal
sinus with the veins of the nasal cavity. |
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