The   maxillary  bones   form  the  upper  jaw,  the anterior roof of the mouth, the floors of the orbits, and the sides and floor of the nasal cavity. The small holes on   each   side   of   the   nasal   opening   are   called   the infraorbital foramina (sing. foramen). The maxillary bones contain large cavities called maxillary sinuses. The  palatine  bones  are  L-shaped  bones  located behind the maxillary bones. They form the posterior section  of  the  hard  palate  and  the  floor  of  the  nasal cavity. The   zygomatic  bones   are   responsible   for   the prominence of the cheeks. The zygomatic bones serve as part of the posterior section of the hard palate and the floor of the nasal cavity. The  lacrimal bones  provide a pathway for a tube that carries tears from the eye to the nasal cavity. The lacrimal bone is a thin, scalelike structure located in the medial wall of each orbit. The   nasal  bones   have   cartilaginous   tissues a t t a c h e d   t o   t h e m .   T h e s e   t i s s u e s   c o n t r i b u t e significantly to the shape of the nose. The nasal bones are long, thin, and nearly rectangular in shape. They lie side by side and are fused together to form the bridge of the nose. The vomer bone is connected to the ethmoid bone, and  together  they  form  the  nasal  septum  (the  wall separating the two nasal cavities). The   middle  and  inferior  nasal  conchae   are fragile,  scroll-shaped  bones  that  are  attached  to  the lateral  wall  of  the  nasal  cavity.  The  inferior  nasal concha   provides   support   for   mucous   membranes within the nasal cavity. The  lower  jawbone  is  called  the  mandible.  The mandible   is   horseshoe-shaped   with   flat,   bony projections on each end. The two small holes on the jawbone   are   called   the   mental   foramina.   The mandible's   main   function   is   mastication   (chewing food). VERTEBRAL  (SPINAL)   COLUMN.—The vertebral   column   consists   of   24   movable   or   true vertebrae; the sacrum; and the coccyx, or tail bone (fig. 1-17).  The  vertebrae  protect  the  spinal  cord  and  the nerves  that  branch  out  from  the  spinal  cord.  Each vertebra has an anterior portion, called the body, which is the large solid segment of the bone (fig. 1-18). This vertebral  body  supports  not  only  the  spinal  cord  but other structures of the body as well. At the bottom of the spinal column is the sacrum and the coccyx. Many of the main muscles are attached to the vertebrae. The  vertebral foramen  is a hole directly behind the body of the vertebrae that forms the passage for the spinal   cord.   The   vertebral   projections   are   for   the attachments   of   muscles   and   ligaments   and   for facilitating  movement  of  one  vertebra  over  another. The spinal column is divided into five regions in the following   order:   cervical   (neck),   thoracic   (chest), 1-9 HM3F0116 PARIENTAL BONE FRONTAL BONE LACRIMAL BONE ETHMOID BONE SQUAMOSAL SUTURE TEMPORAL BONE SPHENOID BONE PERPENDICULAR PLATE OF THE ETHMOID BONE INFRAORBITAL FORAMEN VOMER BONE MANDIBLE MENTAL FORAMEN MAXILLA INFERIOR NASAL CONCHA ZYGOMATIC BONE MIDDLE NASAL CONCHA SPHENOID BONE NASAL BONE Figure 1-16.—Facial bones.