IIYOW BOXE AM) STYLOID PROCESS 67 



Ligaments : — 



Tliyro-hyoid. Stylo-hyoid; and the thyro-hyoid membrane. 



Blood-supply. — The hyoid receives twifrs from the arti'rics supplying the 

 n)uscles attached to it, in addition to direct supply from the superior thyroid and 

 linjfual art<Tics. 



Ossification. — At the third month the hyoid consists of hyaline cartilage; it 

 is directly continuous with the styloid process. In the fourth month, a nucleus 

 aj)i)ears on each side of the middle line; they become quickly confluent to form the 

 l)ody of the bone. In the fifth month each greater cornu has a conspicuous 

 nucleus. The centres for the lesser cornua are delayed until the second year. 



The greater cornua remain separate from the body until after middle life. The 

 lesser cornua rarely ankylose with the body of the bone. As a rule, they are small 

 and inconsi)ieuous; occasionally they are very long, and are sometimes continuous 

 with tlie styloid i)rocess of their respective sides. 



The styloid process is a thin cyHndrical spike of bone wedged in between the 

 tympanic plate and the petrosal immediately anterior to the stylo-mastoid foramen. 

 It consists of two parts: a tympano-hyal segment which in the adult is hidden 

 behind the tympanic plate, and a free projecting portion of variable length. As a 

 rule it varies from five to fifty millimetres. When short it is hidden by the vaginal 

 process, but it may reach to the hyoid bone. Its base forms the anterior boundary 

 of the stylo-mastoid foramen. The free portion gives origin to the following 

 muscles: The stijlo-phnryngeits arises from the base posteriorly; the stylo-hyoid from 

 the outer aspect near the middle; and the stylo-glossus from the front near the tip. 

 The extremity of the process is continuous with the stylo-hyoid ligament. A band 

 of fibrous tissue — the stylo-mandibular ligament — passes from the process below 

 the origin of the stylo-glossus to the angle of the mandible. 



Muscles attached to the styloid process : — Ligaments : — 



Stylo-glossus. Stylo-hyoid . 



Stylo-hyoid. Stylo-mandi bu la r. 



Stylo-pharyngeus. 



The morphology and development of this process are described on })ag(' 90. 



The malleus. — This is the most external of the auditory ossicles, and comes 

 in relation with the tymj^anic membrane. Its upper portion, or head, is lodged in 

 the attic of the tympanum. It is of rounded shape, and presents posteriorly an 

 elliptical depression for articulation with the incus. Below the head is a constricted 

 portion or neck. From beneath the neck three processes diverge. The largest is 

 the handle or manubrium, Avhich is slightly twisted and flattened. It forms an 

 obtuse angle with the head of the bone, and lies between the membrana tympani 

 and the mucous membrane covering its inner surface. 



The tensor tympani tendon is inserted into the manubrium near its junction Mith 

 the neck on the inner side. The slender process (gracilis or Folian) is a long, 

 slender, delicate spiculum of bone (rarely seen of full length except in the foetus), 

 projecting nearly at riglit angles to the anterior aspect of the neck, and extending 

 obli({uely downwards. It lies in the Glaserian fissure, and in the adult usually 

 l)ecomes converted into connective tissue, except a small basal stump. The short 

 process is a conical projection from the outer aspect of the base of the manubrium. 

 Its apex is connected to the upper part of the tympanic memln'ane, and its base 

 receives the external ligament of the malleus. The malleus also gives attachment 

 to the suspensory ligament, and to the long anterior ligament of the malleus which 

 Avas formerly descrilied as the laxator tympani muscle. 



The incus. — This bone is situated between the malleus externally, and the 

 stapes internally. It presents for examination a body and two processes. The 

 body is deeply excavated anteriorly for the reception of the head of the malleus. 

 The short process projects backwards, and is connected by means of ligamentous 

 fibres to the posterior wall of the tympanum, near the entrance to the mastoid 

 antrum. The long process is slender, and directed downwards and inwards; it 



