Page 249 - My FlipBook

BLOOD-VESSEL SYSTEM OF THE HEAD, ETC. : 259
The Lateral Sinuses in either side are large, though .seldom of equal
size. This difference in calibre is caused to a certain extent by the
deflection of th*e straight sinus to one side or the other of the torcular
Herophili, and by its emptying into one or the other sinus. They
begin at the confluence of the sinuses, pass outward, forward, and
downward along the semicircular grooves to which the tentorium is
attached, and extend from the internal occipital prt)tuberance outward
over the inferior posterior angle of the parietal bone, thence along
the sigmoid groove of the mastoid process of the temporal bone, over
the jugular process of the occipital bone, and terminate in the bulb of
the internal jugular veins situated within the rounded or enlarged por-
tion of the posterior lacerated (jugular) foramen. The tributaries of
these sinuses are veins from the posterior part of the cerebrum, from
the cerebellum, diploe, superior petrosal sinus, and emissary veins pass-
ing through the posterior condyloid and mastoid foramina, which are
communicating veins between the sinuses and the veins of the external
portion of the cranium.
The Infero-anterior Group is composed of seven sinuses
Cavernous, Superior petrosal,
Spheno-parietal, Transverse,
Circular, Anterior occipital.
Inferior petrosal.
The Cavenwus Siimses (Fig. 114), two in number, receive their name
from the fact of their being crossed or interlaced by numerous filaments
of connective tissue, which give them the a})pearance of cavernous tissue.
They are situated one on each lateral surface on the body of the s})he-
noid bone, and extend from the inner portion of the anterior lacerated
foramina backward to the apex of the petrous portion of the temporal
bones. They vary in width and shape, being narrow and pointed in
front and wide behind.
Their tributaries are, anteriorly, the terminations of the ophthalmic
veins. On their proximal sui-face they conununicate with each other
through the circular sinus. A communicating branch from the ptery-
goid plexus of either side empties bypassing through the oval foramina
in both wings of the sphenoid bone. They also receive branches from
the cerebral veins, and connnunicating branches from the spheno-parie-
tal sinuses. Posteriorly they terminate by emptying into the superior
and inferior petrosal sinuses. The third, fourth, and the ophthalmic
division of the fifth nerve on either side pass for^^•ard along the outer
walls to make their exit through the anterior lacerated foramina. The
internal carotid arteries, the sixth nerves, and the parotid sympathetic
plexuses pass forward to the inner margins of the floors of the sinuses,
the arteries and nerves passing through these cavernous sinuses ; these
nerves and vessels are separated from the blood of the sinuses by their
thin lining membrane.
The Spheno-parietal Si7iuses (two in number) are situated on the
under surfaces of the lesser wnngs of the sphenoid bone. They receive
communicating branches from the middle meningeal, anterior temporal,
and diploic veins, and occasionally a small vein, the ophthalmo-menin-
geal. They terminate by emptying into the cavernous sinuses.