Reference > Anatomy of the Human Body > Page 151
Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
internal surface, for articulation with the sphenoidal angle of the parietal bone; this region is named the pterion. Medial to this is a triangular, serrated surface, for articulation with the frontal bone; this surface is continuous medially with the sharp edge, which forms the lower boundary of the superior orbital fissure, and laterally with the serrated margin for articulation with the zygomatic bone.

The Small Wings (alæ parvæ).—The small wings or orbito-sphenoids are two thin triangular plates, which arise from the upper and anterior parts of the body, and, projecting lateralward, end in sharp points (Fig. 145).

Surfaces.—The superior surface of each is flat, and supports part of the frontal lobe of the brain. The inferior surface forms the back part of the roof of the orbit, and the upper boundary of the superior orbital fissure. This fissure is of a triangular form, and leads from the cavity of the cranium into that of the orbit: it is bounded medially by the body; above, by the small wing; below, by the medial margin of the orbital surface of the great wing; and is completed laterally by the frontal bone. It transmits the oculomotor, trochlear, and abducent nerves, the three branches of the ophthalmic division of the trigeminal nerve, some filaments from the cavernous plexus of the sympathetic, the orbital branch of the middle meningeal artery, a recurrent branch from the lacrimal artery to the dura mater, and the ophthalmic vein.

Borders.—The anterior border is serrated for articulation with the frontal bone. The posterior border, smooth and rounded, is received into the lateral fissure of the brain; the medial end of this border forms the anterior clinoid process, which gives attachment to the tentorium cerebelli; it is sometimes joined to the middle clinoid process by a spicule of bone, and when this occurs the termination of the groove for the internal carotid artery is converted into a foramen (carotico-clinoid). The small wing is connected to the body by two roots, the upper thin and flat, the lower thick and triangular; between the two roots is the optic foramen, for the transmission of the optic nerve and ophthalmic artery.

Pterygoid Processes (processus pterygoidei).—The pterygoid processes, one on either side, descend perpendicularly from the regions where the body and great wings unite. Each process consists of a medial and a lateral plate, the upper parts of which are fused anteriorly; a vertical sulcus, the pterygopalatine groove, descends on the front of the line of fusion. The plates are separated below by an angular cleft, the pterygoid fissure, the margins of which are rough for articulation with the pyramidal process of the palatine bone. The two plates diverge behind and enclose between them a V-shaped fossa, the pterygoid fossa, which contains the Pterygoideus internus and Tensor veli palatini. Above this fossa is a small, oval, shallow depression, the scaphoid fossa, which gives origin to the Tensor veli palatini. The anterior surface of the pterygoid process is broad and triangular near its root, where it forms the posterior wall of the pterygopalatine fossa and presents the anterior orifice of the pterygoid canal.

Lateral Pterygoid Plate.—The lateral pterygoid plate is broad, thin, and everted; its lateral surface forms part of the medial wall of the infratemporal fossa, and gives attachment to the Pterygoideus externus; its medial surface forms part of the pterygoid fossa, and gives attachment to the Pterygoideus internus.

Medial Pterygoid Plate.—The medial pterygoid plate is narrower and longer than the lateral; it curves lateralward at its lower extremity into a hook-like process, the pterygoid hamulus, around which the tendon of the Tensor veli palatini glides. The lateral surface of this plate forms part of the pterygoid fossa, the medial surface constitutes the lateral boundary of the choana or posterior aperture of the corresponding nasal cavity. Superiorly the medial plate is prolonged on to the under surface of the body as a thin lamina, named the vaginal process, which articulates in front with the sphenoidal process of the palatine and behind this with the ala of the vomer. The angular prominence between the posterior margin


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