SUTURES OP THE SKULL. 97 



Articulations. "With the glenoid fossas of the two temporal bones. 



Attachment of Muscles. By its external surface, commencing at the symphysis^ 

 and proceeding backwards : Levator menti, Depressor labii inferioris, Depressor' 

 auguli oris, Platysma myoides, Buccinator, Masseter. By its internal surface, com- 

 mencing at the same point; Genio-hyo-glossus, Genio-hyoideus, Mylo-hyoideus, 

 Digastricus, Superior constrictor, Temporal, Internal pterygoid, External pterygoid. 



THE SUTUEES. 



The bones of the cranium and face are connected to each other by means of 

 sutures. The dentations by which they are joined are confined to the external 

 table, the edges of the internal table lying merely in apposition with the contiguous 

 bone. The Cranial Sutures may be divided into three sets: 1. Those at the ver- 

 tex of the skull. 2. Those at the side of the skull. 3. Those at the base. 



The sutures at the vertex of the skull are three, the sagittal, coronal, and lamb- 

 doid. 



The Sagittal Suture (interparietal) is formed by the junction of the two parietal 

 bones, and extends from the middle of the frontal bone, backwards to the superior 

 angle of the occipital. In childhood, and occasionally in the adult, when the two 

 halves of the frontal bone are not united, it is continued forwards to the root of the 

 nose. This suture sometimes presents, near its posterior extremity, the parietal 

 foramen on each side ; and in front, where it joins the coronal suture, a space is 

 occasionally left, which incloses a large Wormian bone. 



The Coronal Suture (^fr onto -parietal) extends transversely across the vertex 

 of the skull, and connects the frontal with the parietal bones. It commences at 

 the extremity of the great wing of the sphenoid on one side, and terminates at the 

 same point on the opposite side. The dentations of this suture are more marked 

 at the sides than at the summit, and are so constructed that the frontal rests on the 

 parietal above, whilst laterally the frontal supports the parietal. 



The Lambdoid Suture (occipito-parietal), so called from its resemblance to the 

 Greek letter A, connects the occipital with the parietal bones. It commences on 

 each side at the mastoid portion of the temporal bone, and inclines upwards to the 

 end of the sagittal suture. The dentations of this suture are very deep and dis- 

 tinct, and are often interrupted by several small Wormian bones. 



The sutures at the side of the skull are also three in number: the spheno-parietal, 

 squamo-parietal, and masto-parietal. They are subdivisions of a single suture, 

 formed between the lower border of the parietal, and the temporal and sphenoid 

 bones, and which extends from the lower end of the lambdoid suture behind, to 

 the lower end of the coronal suture in front. 



The Spheno-parietal is very short ; it is formed by the tip of the great wing of 

 the sphenoid, which overlaps the anterior inferior angle of the parietal bone. 



The Squamo-parietal, or squamous suture, is arched. It is formed by the 

 sfc[uamous portion of the temporal bone overlapping the middle division of the 

 lower border of the parietal. 



The Masto-parietal is a short suture, deeply dentated, formed by the posterior 

 inferior angle of the parietal, and the superior border of the rnastoid portion of the 

 temporal. 



The sutures of the base of the skull are, the basilar in the centre, and, on each 

 side, the petro-occipital and masto-occipital, the petro-sphenoidal and the squamo- 

 sphenoidal. 



The Basilar Suture is formed by the junction of the bpsilar surface of the 

 occipital bone with the posterior surface of the body of the sphenoid. At an earl y 

 period of life, a thin plate of cartilage exists between these bones; but in the adult 

 they become inseparably united. Between the outer extremity of the basilar suture, 

 and the termination of the lambdoid, an irregular suture exists which is subdivided 

 into two portions. The inner portion, formed by the union of the petrous part of 

 the temporal with the occipital bone, is termed the petro-occipital. The outer 

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