![]() The wing-like squamous portion of this bone articulates superiorly with the parietal bone and anteriorly with the greater wing of the sphenoid. The temporal bones form the lateral portions of the middle cranial fossa and the anterior portion of the posterior cranial fossa ( Figure 3.2 ). A strong roughly horizontal ridge runs along the back of the occipital bone onto which the occipital muscle inserts. Superiorly it joins the parietal bones along a complex suture line, and laterally it articulates with the temporal bones. The base of the occipital bone articulates anteriorly with the body of the sphenoid bone. It has a large opening on its inferior surface, the foramen magnum, through which the spinal cord passes. The occipital bone forms the posterior portion of the posterior cranial fossa and the posterior segment of the skull base ( Figure 3.2 ). The foramen spinosum is located near the posterior edge of the greater wing and carries a branch of the middle meningeal artery and the recurrent branch of the mandibular nerve (V 3 ). The foramen ovale is slightly larger and more posterior on the greater wing, and transmits the mandibular branch of the trigeminal nerve (V 3 ). The foramen rotundum lies anterior between the body of the sphenoid and the root of the greater wing, and transmits the maxillary branch of the trigeminal nerve (V 2 ). Three additional foramina are found in the greater wing. The longitudinal space between the greater and lesser sphenoid wings is the superior orbital fissure, a major conduit between the middle cranial fossa and the posterior orbit. The latter communicates with the orbit via the inferior orbital fissure. Inferiorly, the small pterygoid process projects downward from the greater wing near its base, where it joins the palatine bone to form the lateral wall of the pterygopalatine fossa. They articulate with the frontal bones anteriorly, the temporal and parietal bones posterolaterally, and the zygomatic bones anterolaterally. The greater wings of the sphenoid bone arise from the body and project laterally. The small canal that is formed between the body and lesser wing of the sphenoid is the optic canal. The lesser wings of the sphenoid bone, one on either side, arise as a narrow strut from the sphenoid body and project superiorly and laterally to articulate along their anterior surface with the ethmoid bone centrally and with the frontal bones. The central portion of the sphenoid bone is a hollow cavity, the sphenoid sinus.įrom the body of the sphenoid bone two pairs of thin plates extend laterally. It is bounded anteriorly by paired elevated ridges called the anterior clinoid processes, and posteriorly by a horizontal raised ridge, the posterior clinoid process. A small depression is located on the intra-cranial surface of the sphenoid body, the sella turcica or pituitary fossa. More inferiorly the anterior sphenoid contacts the maxillary and palatine bones. Posteriorly the body of the sphenoid bone abuts the occipital bone, and anteriorly it articulates with the ethmoid bone centrally and with the frontal bones just lateral to the midline. The base of the skull is formed primarily by the unpaired sphenoid and occipital bones ( Figure 3.1 ). The orbit is made up of portions of both the cranial and the facial skeletal systems. The face is attached anteriorly and consists of two unpaired bones, the vomer and mandibular bones, and six paired bones, the nasal, maxillary, zygomatic, palatine, lacrimal, and inferior turbinate bones. The cranium is the major portion and it consists of three unpaired bones, the sphenoid, occipital, and ethmoid bones, and three paired bones, the frontal, parietal, and temporal bones. The skull is composed of two segments, the cranium and the face.
0 Comments
Leave a Reply. |