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The inner surface of the mastoid portion presents a deep, curved groove, the sigmoid sulcus, which lodges part of the transverse sinus; in it may be seen in the opening of the mastoid foramen. The groove for the transverse sinus is separated from the innermost of the mastoid cells by a very thin lamina of bone, and even this may be partly ...
The inner surface of the mastoid portion of the temporal bone presents a deep, curved groove, the sigmoid sulcus, which lodges part of the transverse sinus; in it may be seen the opening of the mastoid foramen.
On the upper surface of the jugular process is a deep groove which curves medialward and forward and is continuous with the jugular notch. This groove lodges the terminal part of the transverse sinus, and opening into it, close to its medial margin, is the orifice of the condyloid canal .
The mastoid angle is truncated; it articulates with the occipital bone and with the mastoid portion of the temporal, and presents on its inner surface a broad, shallow groove which lodges part of the transverse sinus. The point of meeting of this angle with the occipital and the mastoid part of the temporal is named the asterion.
The mastoid foramen is a hole in the posterior border of the temporal bone. It transmits an emissary vein between the sigmoid sinus and the suboccipital venous plexus , and a small branch of the occipital artery , the posterior meningeal artery to the dura mater .
The boundary between the squamous part and the mastoid portion of the bone, as indicated by traces of the original suture, lies about 1 cm. below this line. Projecting from the lower part of the squamous part is a long, arched process, the zygomatic process. This process is at first directed lateralward, its two surfaces looking upward and ...
The nuchal lines are four curved lines on the external surface of the occipital bone: . The upper, often faintly marked, is named the highest nuchal line, but is sometimes referred to as the Mempin line or linea suprema, and it attaches to the epicranial aponeurosis.
They may excavate the mastoid process to its tip, and be separated from the posterior cranial fossa and sigmoid sinus by a mere slip of bone or not at all. They may extend into the squamous part of temporal bone, petrous part of the temporal bone zygomatic process of temporal bone, and - rarely - the jugular process of occipital bone; they may thus come to adjoin many important structures ...