The Human Skull
Note this information is from http://www.bartleby.com
Temporal bones
You must be able to ID the parts listed
Left temporal bone. Outer surface.
Left temporal bone. Inner surface.
Coronal section of right temporal bone.
Parotid region
The parotid region (see fig. 50-2C) comprises the parotid gland and its bed, which includes muscles and part of the skull. The temporal region is on the side of the head (temple). The infratemporal region is medial to the ramus of the mandible.
Fig. 50-2. Triangles of the neck. A shows the platysma, which roofs parts of both the anterior and posterior triangles. B shows the division of the neck by the sternomastoid into anterior and posterior triangles. C and D show the subdivisions of the triangles
mastoid process - the size and form of which very somewhat; it is larger in the male than in the female. This process serves for the attachment of the Sternocleidomastoideus, Splenius capitis, and Longissimus capitis.
Styloid Procéss (processus styloideus).—The styloid process is slender, pointed, and of varying length; it projects downward and forward, from the under surface of the temporal bone. Its proximal part (tympanohyal) is ensheathed by the vaginal process of the tympanic portion, while its distal part (stylohyal) gives attachment to the stylohyoid and stylomandibular ligaments, and to the Styloglossus, Stylohyoideus, and Stylopharyngeus muscles. The stylohyoid ligament extends from the apex of the process to the lesser cornu of the hyoid bone, and in some instances is partially, in others completely, ossified.
Stylomastoid foramen - between the styloid and mastoid processes is the stylomastoid foramen; it is the termination of the facial canal, and transmits the facial nerve and stylomastoid artery
. The Zygomatic Bone
(Os Zygomaticum; Malar Bone)
The zygomatic bone is small and quadrangular, and is situated at the upper and lateral part of the face: it forms the prominence of the cheek, part of the lateral wall and floor of the orbit, and parts of the temporal and infratemporal fossæ It presents a malar and a temporal surface; four processes, the frontosphenoidal, orbital, maxillary, and temporal; and four borders.
Surfaces.—The malar surface is convex and perforated near its center by a small aperture, the zygomaticofacial foramen, for the passage of the zygomaticofacial nerve and vessels; below this foramen is a slight elevation, which gives origin to the Zygomaticus.
The temporal surface directed backward and medialward, is concave, presenting medially a rough, triangular area, for articulation with the maxilla, and laterally a smooth, concave surface, the upper part of which forms the anterior boundary of the temporal fossa, the lower a part of the infratemporal fossa. Near the center of this surface is the zygomaticotemporal foramen for the transmission of the zygomaticotemporal nerve.
Processes.—The frontosphenoidal process is thick and serrated, and articulates with the zygomatic process of the frontal bone. On its orbital surface, just within the orbital margin and about 11 mm. below the zygomaticofrontal suture is a tubercle of varying size and form, but present in 95 per cent. of skulls. The orbital process is a thick, strong plate, projecting backward and medialward from the orbital margin. Its antero-medial surface forms, by its junction with the orbital surface of the maxilla and with the great wing of the sphenoid, part of the floor and lateral wall of the orbit. On it are seen the orifices of two canals, the zygomaticoörbital foramina; one of these canals opens into the temporal fossa, the other on the malar surface of the bone; the former transmits the zygomaticotemporal, the latter the zygomaticofacial nerve. Its postero-lateral surface, smooth and convex, forms parts of the temporal and infratemporal fossæ. Its anterior margin, smooth and rounded, is part of the circumference of the orbit. Its superior margin, rough, and directed horizontally, articulates with the frontal bone behind the zygomatic process. Its posterior margin is serrated for articulation, with the great wing of the sphenoid and the orbital surface of the maxilla. At the angle of junction of the sphenoidal and maxillary portions, a short, concave, non-articular part is generally seen; this forms the anterior boundary of the inferior orbital fissure: occasionally, this non-articular part is absent, the fissure then being completed by the junction of the maxilla and sphenoid, or by the interposition of a small sutural bone in the angular interval between them. The maxillary process presents a rough, triangular surface which articulates with the maxilla. The temporal process, long, narrow, and serrated, articulates with the zygomatic process of the temporal.
FIG. 164– Left zygomatic bone in situ.
FIG. 165– Left zygomatic bone. Malar surface.
FIG. 166– Left zygomatic bone. Temporal surface. (See enlarged image)
Borders.—The antero-superior or orbital border is smooth, concave, and forms a considerable part of the circumference of the orbit. The antero-inferior or maxillary border is rough, and bevelled at the expense of its inner table, to articulate with the maxilla; near the orbital margin it gives origin to the Quadratus labii superioris. The postero-superior or temporal border, curved like an italic letter f, is continuous above with the commencement of the temporal line, and below with the upper border of the zygomatic arch; the temporal fascia is attached to it. The postero-inferior or zygomatic border affords attachment by its rough edge to the Masseter.
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Ossification.
—The zygomatic bone is generally described as ossifying from three centers—one for the malar and two for the orbital portion; these appear about the eighth week and fuse about the fifth month of fetal life. Mall describes it as being ossified from one center which appears just beneath and to the lateral side of the orbit. After birth, the bone is sometimes divided by a horizontal suture into an upper larger, and a lower smaller division. In some quadrumana the zygomatic bone consists of two parts, an orbital and a malar.
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Articulations.—The zygomatic articulates with four bones: the frontal, sphenoidal, temporal, and maxilla.
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FIG. 167– Articulation of left palatine bone with maxilla.
Squamous region
Internal auditory canal - Near the center is a large orifice, the internal acoustic meatus, the size of which varies considerably; its margins are smooth and rounded, and it leads into a short canal, about 1 cm. in length, which runs lateralward. It transmits the facial and acoustic nerves and the internal auditory branch of the basilar artery.
carotid canal
n.
A passage through the petrous part of the temporal bone that transmits the internal carotid artery.
Mandibular fossa is number 22 in the picture
External auditory canal
External auditory canal
External auditory canal
Tympanic portion:
The tympanic part of the temporal bone forms the anterior and inferior walls and part of the posterior wall of the external auditory meatus.It is separated anteriorly from the squamous bone by the tympanosquamous suture more medially from the petrous bone by the petrotympanic fissure and posteriorly from the mastoid portion of the petrous bone by the tympanomastoid fissure. The inner part of the tympanic ring is grooved and is called the tympanic sulcus, which accomodates the tympanic membrane annulus. The inferior aspect of the tympanic bone is elongated into a vaginal process immediately anterior to the styloid process.
The Occipital Bone
You must be able to ID the parts listed
Occipital bone- situated at the back and lower part of the cranium, is trapezoid in shape and curved on itself. It is pierced by a large oval aperture, the foramen magnum, through which the cranial cavity communicates with the vertebral canal.
Foramen magnum - through which the cranial cavity communicates with the vertebral canal.
Occipital condyles In the center of this picture you can see the occipital condyles protruding downward. The head sits on top of the atlas via these condyles. NOTE: there is actually two facets on each condyle, making a total of four articular surfaces. These facets correspondingly have a matching number of facets on the atlas. This fact was discovered by Dr. Earl F. Craton. In 1985
Hypoglossal canal – (anterior condyloid foramen). This begins on the cranial surface of the bone immediately above the foramen magnum, and is directed lateralward and forward above the condyle. It may be partially or completely divided into two by a spicule of bone; it gives exit to the hypoglossal or twelfth cerebral nerve, and entrance to a meningeal branch of the ascending pharyngeal artery.
External occipital protuberance - between the summit of the bone and the foramen magnum a prominence, the external occipital protuberance.
Superior and inferior nuchal lines - from the external occipital protuberance extending lateralward s on either side are two curved lines, one a little above the other. The upper, often faintly marked, is named the highest nuchal line, and to it the galea aponeurotica is attached. The lower is termed the superior nuchal line. And below it the inferior nuchal line
Jugular foramen - Extending lateralward from the posterior half of the condyle is a quadrilateral plate of bone, the jugular process, excavated in front by the jugular notch, which, in the articulated skull, forms the posterior part of the jugular foramen.
Sphenoid bone
You must be able to ID the parts listed.
Body (corpus sphenoidale).—The body, more or less cubical in shape, is hollowed out in its interior to form two large cavities, the sphenoidal air sinuses, which are separated from each other by a septum.
The Great Wings (alæ magnæ).—The great wings, or ali-sphenoids, are two strong processes of bone, which arise from the sides of the body, and are curved upward, lateralward, and backward; the posterior part of each projects as a triangular process which fits into the angle between the squama and the petrous portion of the temporal and presents at its apex a downwardly directed process, the spina angularis (sphenoidal spine).
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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
Sella turcica - A depression of the bone at the base of the skull where the pituitary gland is located (labeled Dorsum in picture)
the chiasmatic groove (optic groove), above and behind which lies the optic chiasma; the groove ends on either side in the optic foramen, which transmits the optic nerve (CNII) and ophthalmic artery into the orbital cavity
Optic foramen - for the transmission of the optic nerve (CNII) and ophthalmic artery.
foramen rotundum, for the transmission of the maxillary nerve
foramen ovale, for the transmission of the mandibular nerve, the accessory meningeal artery, and sometimes the lesser superficial petrosal nerve.
Foramen spinosum in the posterior angle, near to and in front of the spine, is a short canal, sometimes double. which transmits the middle meningeal vessels and a recurrent branch from the mandibular nerve.
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.
Hyoid bone –
Auditory ossicles
Model of the auditory ossicles
1. Stapes (stirrup)
2. Incus (anvil)
3. Malleus (hammer)
Mandible
Maxillae
Palatine
Vomer
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