"EOLOGY 



of the vaginal process and the medial border of the scaphoid fossa is named the 

 pterygoid tubercle, and immediately above this is the posterior opening of the 

 pterygoid canal. On the under surface of the vaginal process is a furrow, which 

 is converted into a canal by the sphenoidal process of the palatine bone, for the 

 transmission of the pharyngeal branch of the internal maxillary artery and the 

 pharyngeal nerve from the sphenopalatine ganglion. The pharyngeal aponeurosis 

 is attached to the entire length of the posterior edge of the medial plate, and the 

 Constrictor pharyngis superior takes origin from its lower third. Projecting 

 backward from near the middle of the posterior edge of this plate is an angular 

 process, the processus tubarius, which supports the pharyngeal end of the auditory 

 tube. The anterior margin of the plate articulates with the posterior border of 

 the vertical part of the palatine bone. 



The Sphenoidal Conchee (concha? sphenoidales; sphenoidal turbinated processes}, 

 The sphenoidal conchse are two thin, curved plates, situated at the anterior 

 and lower part of the body of the sphenoid. An aperture of variable size exists 

 in the anterior wall of each, and through this the sphenoidal sinus opens into the 

 nasal cavity. Each is irregular in form, and tapers to a point behind, being broader 

 and thinner in front. Its upper surface is concave, and looks toward the cavity 

 of the sinus; its under surface is convex, and forms part of the roof of the corre- 

 sponding nasal cavity. Each bone articulates in front with the ethmoid, laterally 

 with the palatine; its pointed posterior extremity is placed above the vomer, 

 and is received between the root of the pterygoid process laterally and the rostrum 

 of the sphenoid medially. A small portion of the sphenoidal concha sometimes 

 enters into the formation of the medial wall of the orbit, between the lamina 

 papyracea of the ethmoid in front, the orbital plate of the palatine below, and the 

 frontal bone above. 



Ossification. Until the seventh or eighth month of fetal life the body of the sphenoid consists 

 of two parts, viz., one in front of the tuberculum selte, the presphenoid, with which the small 

 wings are continuous; the other, comprising the sella turcica and dorsum sellse, the postsphenoid, 



with which are associated the great 

 wings, and pterygoid processes. The 

 greater part of the bone is ossified in 

 cartilage. There are fourteen centers 

 in all, six for the presphenoid and eight 

 for the postsphenoid. 



Presphenoid.- About the ninth week 

 of fetal life an ossific center appears for 

 each of the small wings (orbitosphenoids) 

 just lateral to the optic foramen; shortly 

 afterward two nuclei appear in the pre- 



FIG. 148. Sphenoid bone at birth. Posterior aspect. sphenoid part of the body. The sphe- 



noidal conchaj are each developed from 



a center which makes its appearance about the fifth month; 1 at birth they consist of small 

 triangular laminae, and it is not until the third year that they become hollowed out and cone- 

 shaped; about the fourth year they fuse with the labyrinths of the ethmoid, and between the 

 ninth and twelfth years they unite with the sphenoid. 



Postsphenoid. The first ossific nuclei are those for the great wings (ali-sphenoids) 2 . One makes 

 its appearance in each wing between the foramen rotundum and foramen ovale about the eighth 

 week. The orbital plate and that part of the sphenoid which is found in the temporal fossa, as 

 well as the lateral pterygoid plate, are ossified in membrane (Fawcett) 3 . Soon after, the centers 

 for the postsphenoid part of the body appear, one on either side of the sella turcica, and become 

 blended together about the middle of fetal life. Each medial pterygoid plate (with the exception 

 of its hamulus) is ossified in membrane, and its center probably appears about the ninth or tenth 

 week; the hamulus becomes chondrified during the third month, and almost at once undergoes 



1 According to Cleland, each sphenoidal concha is ossified from four centers. 



2 Mall, Am. Jour. Anat., 1906, states that the pterygoid center appears first in an embryo fifty-seven days old. 



3 Journal of Anatomy and Physiology, 1910, vol. xliv. 



