64 



THE SKELETON 



nasal fossae, presenting superiorly the irregular apertures of the sphenoidal 

 sinuses. 



The body is not hollowed until after the sixth year, but from that time the sinuses increase 

 in size as age advances. Except for the apertures just mentioned, they are closed below and 

 in front by the two sphenoidal conchae (turbinate bones), originally distinct, but in the adult 

 usually incorporated with the sphenoid. 



The posterior surface is united to the basilar process of the occipital, up to 

 the twentieth j'ear, by a disc of hyaline cartilage forming a synchondrosis, but 

 afterward this becomes ossified and the two bones then form one piece. 



Fig. 80. — The Left Half of the Sphenoid. 



Anterior clinoid process 



Middle clinoid process 



Posterior clinoid process 



Spine of sphenoid 

 Lateral pterygoid plate 

 Hamular process of medial pterygoid plate 



Ethmoidal spine 



'The limbus 

 Optic groove 

 Tuberculum sellae 



Dorsum sellae 

 For occipital 



The lateral surface of the body gives attachment to the two wings, and its 

 fore part is free where it forms the medial boundary of the superior orbital fissure and 

 the posterior part of the medial wall of the orbit. Above the line of attachment 

 of the great wing is a broad groove which lodges the internal carotid artery and 

 the cavernous sinus, called the carotid groove. It is deepest where it curves behind 

 the root of the process, and this part is bounded along its lateral margin by a 

 slender ridge of bone named the lingula, which projects backward in the angle 

 between the body and the great wing. 



Fig. 81, — The Sphenoid. (Anterior view.) 



Optic foramen 



Superior orbi- 

 tal fissure 



Orbital surface (the pointer 

 crosses the zygomatic 

 border; 



Lateral pterygoid plate 



Pterygoid notch 



Hamular process 



Foramen rotundum 

 Pterygoid canal 



Pterygo-palatine groove 



The small or orbital wings [alae parvse] are two thin, triangular plates of bone 

 extending nearly horizontally and laterally on a level with the front part of the 

 upper surface of the body. Each arises medially by two processes or roots, the 

 upper thin and flat, the lower thick and rounded. 



Near the jiinctif)n of the lower root with the body is a small tubercle for the attachment of 

 the common tendon of three ocular muscles — viz., the superior, medial, and upper head of 

 lateral rectus — and between the two roots is the optic foramen. The lateral extremity, slender 

 anrl pointed, approaches the (!;rcat win-j;, but, as a rule, does not actually touch it. The supe- 

 rior surface, smooth and slightly concave, forms the posterior part of the anterior fossa of the 

 craniiun. The inferior surface constitutes a portion of the roof of each orbit and overhangs 



