Anatoma del hueso temporal

1.- Squamous Bone Above the level of the zygomatic process, the vertical portion of the squamous bone extends upward to cover part of the temporal lobe of the brain. The zygomatic process is actually part of the squamous portion of the bone. It originates anterior to the external auditory canal at the level of the junction of the vertical and horizontal parts of the squamous bone. The root of the zygomatic process shows an initial swelling known as the posterior zygomatic tubercle. Traced anteriorly, the root thins out to form the glenoid fossa for the articulation of the head of the mandible, and then thickens again to form the anterior zygomatic tubercle. Posterior to the external auditory canal, the zygomatic process can be traced as a somewhat faint line, the supramastoid crest, indicating the level of the middle cranial fossa.

The squamous part of the temporal bone also forms the superior parts of both the anterior and posterior walls of the bony external auditory canal. On the posterosuperior border of the canal, the spine of Henle can be seen

2.- Tympanic Bone The gutter-shaped tympanic bone forms the inferior wall and major parts of the anterior and posterior walls of the bony external auditory canal. Two sutures between the elementary structures that form the temporal bone appear in the canal: The tympanosquamous suture is located anterosuperiorly The tympanomastoid suture posteroinferiorly. The temporomandibular joint is located just anterior to the canal and is separated from the canal only by a thin bony shell. The lateral border of the tympanic bone is roughened for the attachment of the cartilaginous part of the external auditory canal, which forms the outer two-thirds of the canal. The inferior edge of the tympanic bone expands to form the vaginal process where the styloid process lies.

3.- Mastoid Process The process serves as the anterior part of the attachment of the sternocleidomastoid muscle. On its medial surface lies the digastric groove, from which the posterior belly of the digastric muscle originates. On the posteromedial end of the groove, an impression of the occipital artery can be seen. The stylomastoid foramen, from which the main trunk of the facial nerve exits the temporal bone, can be seen at the anterior border of the digastric ridge posterior to the styloid process. The temporal component of the jugular foramen can be seen anteromedial to the stylomastoid foramen and medial to both the tympanic bone and the styloid process. From the lateral border of the foramen, the jugular spine of the temporal bone can be seen extending into the foramen toward its occipital counterpart and separating the foramen into the what are known as the vascular and nervous compartments. Through the fossa and at a more superior level, the dome of the jugular bulb can be seen. Posteriorly lies the small canal for the passage of Arnolds nerve (the auricular branch of the vagus nerve), while anteriorly the end of the groove of the in- ferior petrosal sinus can be seen lateral and anterior to the opening of the cochlear aqueduct. The foramen of the internal carotid artery is separated from the anterior border of the jugular foramen by a thin wedge of bone called the jugulo- carotid spine, through which a canal for the passage of Jacobsons nerve (the tympanic nerve) to the tympanic cavity lies.

4.- Petrous Bone The most prominent feature of the medial aspect of the temporal bone is the petrous part. Shaped like a pyramid, this part protrudes in an anteromedial direction, with the base located laterally and formed by the semicircular canals, vestibule, cochlea, and carotid artery. The apex of this bone forms part of the anterior foramen lacerum. Through the apex, the internal carotid artery exits the petrous bone to the anterior foramen lacerum, where it curves superiorly on its way to the cavernous sinus. T he end of the bony part of the eustachian tube, the isthmus, is also located in the apex anterior to the carotid opening and just medial to the spine of the sphenoid. The superior surface of the petrous bone forms part of the middle cranial fossa. It begins from the arcuate eminence and ends at the foramen lacerum. The groove of the greater petrosal nerve can be seen coursing close to the bone near the anterior border of this surface; in 10 % of cases, the nerve can be traced posteriorly into a dehiscent geniculate ganglion. The bisection of the angle formed by this groove and the arcuate eminence marks the position of the internal auditory canal. Near the foramen lacerum, the impression of Meckels cavity can be seen. The posterior border of this surface is marked by the groove for the superior petrosal sinus, which separates the superior and posterior surfaces. The posterior surface of the petrous bone forms part of the posterior cranial fossa. The opening for endolymphatic duct and sac can be seen at the lateral end of this surface. This opening represents an important landmark for the posterior semicircular canal in procedures using the retrosigmoid ap- proach. The most important feature of the posterior surface is the internal auditory meatus.

Forma piramidal cuadrangular con dos caras endocraneales (superiores) y dos caras exocraneales (inferiores) Cara anterosuperior o cerebral: Ancha hacia la base Eminencia arcuata (determinado por el conducto semicircular superior) Por delante de la eminencia arcuata esta el Tegmen Tympani Lo ms medial es la fosita de Gasser para el ganglio trigmino (esta a 52 mm del CAE) Entre ambas estructuras, 2-3 orificios: El hiato de falopio y sus accesorios. Para los nervios petrosos superficial mayor y menor y los profundos mayor y menor. Cara Posterosuperior o cerebelosa Canal del seno petroso inferior y CAI Orificio del CAI mide 6-10 mm Una cresta supraauditiva: la fosita subarcuata (esta por encima y por fuera del CAI), en relacin a la eminencia arquata: canal petromastoideo de Chatellier, atraviesa por el camino del domo al canal semicircular superior (remanente embrionario de unas comunicaciones de la arteria cerebelar entre la fosa posterior y la zona del peasco, se atrofia en el post nacimiento) Mas hacia lateral se encuentra la fosita ungueal (como una impresin con el pulgar, forma una cresta por encima que se llama el oprculo) con una hendidura para el acueducto del vestbulo. Lo seo se llama acueducto y lo membranoso son los conductos. Mas hacia lateral se encuentra el canal del seno lateral (su porcin descendente)

Cara postero inferior: En relacin con la superficie mas exterior de la base de crneo. En la zona ms externa: Punta de la apfisis mastoidea. La apfisis estiloides El agujero estilo mastoideo (por detrs y por fuera de la apfisis estiloidea). Esto es importante en la parte quirrgica al abordar la partida, si llegan al estiloides es por que pasaron de largo y el facial se les qued atrs. Por delante y por fuera otro pequeo orificio el conducto posterior de la cuerda del tmpano. La faceta yugular que se articula con la apfisis yugular del occipital. En la zona media: La fosa yugular para el golfo de la yugular interna (estructura ms predominante) En la pared externa pequeo orificio para el ramo auricular del X par o ramo de la fosa yugular de Cruveilhier. En la zona mas interna: Orificio del conducto carotideo: cartida interna. Se va a ver ms adelante hacia la punta, y antes se denominaba agujero rasgado posterior. Orificio del conducto cartico timpnico (vasos cartico timpnica y filete simptico al nervio de Jacobson) En el angula del conducto carotideo y la fosa yugular est el Conducto de Jacobson (rama del IX) Por detrs del conducto carotideo: Fosita piramidal o petrosa para el acueducto coclear o canal de Cotugno. Orificio anterior del conducto carotideo.