APPLIED ANATOMY. 



THE SKULL 



The skull is the bony framework of the head. It is divided into the bones of 

 the cranium and those of the face. The hyoid bone is usually classified with the 

 bones of the head. 



The cranium consists of the bones forming the brain case. They are the 

 occipital, two parietals, the frontal, two temporals, the sphenoid, and the ethmoid. 



The bones of the face are fourteen in number, there being two single bones 

 and six pairs. The single bones are the -inaudible, or inferior maxilla, and vomer ; 

 the pairs are the superior maxilla, malar, nasal, palate, lachrymal, and inferior 

 tnrbinated bones. 



THE SKULL IN CHILDHOOD. 



The skull of the infant is markedly different from that of the adult. At birth the 

 face is quite small and undeveloped, while the cranium is relatively large. The frontal 



and parietal eminences are very marked. 

 The vault of the skull is not entirely os- 

 sified and the sutures are not completed. 

 The bones of the base of the skull 

 originate in cartilage, while those of the 

 vault originate in membrane. This mem- 

 brane has one or more centres of ossi- 

 fication appearing in it for each bone. 

 These centres increase in size and finally 

 meet at the edges of the bone, thus form- 

 ing the sutures. At the time of birth the 

 sutures are represented by membrane, 

 which joins the adjacent bony edges. 



The frontal bone has two centres of 

 ossification; one for each side. These 

 form a suture in the median line of the 

 forehead which becomes obliterated in 

 the course of the first or second year. 

 Traces of it in the shape of a groove or 

 ridge can sometimes be seen or felt in the 

 adult skull. The frontal eminences are 

 far more marked in childhood than later 

 in life and give to children the promi- 

 nent forehead which is so characteristic. 

 A similar peculiarity is seen in the 

 parietal bones, the parietal eminences 



being quite prominent. On this account, they are often injured in childbirth, 

 sometimes being compressed by the obstetrical forceps, and are frequently the seat of 

 htzmatoma neonatorum. The cranial bones not being firmly united allow of a certain 

 amount of play or even overlapping, thus facilitating the delivery of the head at birth. 

 Fontanelles. At the juncture of the various bones are six spaces called fontan- 

 elles. Two, the anterior and posterior, are in the median line of the cranium, and 

 four, the two anterolateral and two posterolateral, are at the sides. The fontanelles 

 are situated at the four corners of the parietal bones. 



The anterior fontunelle is the largest. It is diamond-shaped and formed by the 

 frontal suture in front, the interparietal behind, and the coronal at each side. It is usu- 

 ally closed by the end of the second year, but may be delayed until the fourth. In 

 rickets and malnutrition the fontanelles remain open longer than would otherwise 

 be the case. 



The posterior fontanelle is formed by the juncture of the parietal (sagittal) suture 

 with the lambdoidal suture. It is triangular in shape with the apex forward between 

 the two parietal bones, the sides passing down, one to the right and the other to the 

 left of the top of the occipital bone. 



Anterior. 



FIG. n. Infant's skull, showing posterior and anterior 

 fontanelles. 



