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Figure

The horizontal portions of the palatine bones form the posterior section of the hard palate, and the perpendicular portions help form the lateral walls of the nasal cavity.

process of a temporal bone. Together these processes form a zygomatic arch (see figs. 7.21 and 7.22).

4. Lacrimal bones. A lacrimal (lak'ri-mal) bone is a thin, scalelike structure located in the medial wall of each orbit between the ethmoid bone and the maxilla (see fig. 7.21). A groove in its anterior portion leads from the orbit to the nasal cavity, providing a pathway for a channel that carries tears from the eye to the nasal cavity.

5. Nasal bones. The nasal (na'zal) bones are long, thin, and nearly rectangular (see fig. 7.19). They lie side by side and are fused at the midline, where they form the bridge of the nose. These bones are attachments for the cartilaginous tissues that form the shape of the nose.

6. Vomer bone. The thin, flat vomer (vo'mer) bone is located along the midline within the nasal cavity. Posteriorly, it joins the perpendicular plate of the ethmoid bone, and together they form the nasal septum (figs. 7.29 and 7.30).

7. Inferior nasal conchae. The inferior nasal conchae (kong'ke) are fragile, scroll-shaped bones attached to the lateral walls of the nasal cavity. They are the

Mandible

Figure 7.29

Sagittal section of the skull.

Palatine process of maxilla

Temporal bone Parietal bone

Squamosal suture

Lambdoidal suture Occipital bone

Internal acoustic meatus

Jugular foramen Sella turcica

Sphenoidal sinus Palatine bone Vomer bone Alveolar arches

Coronal suture

Frontal bone

Frontal sinus

Ethmoid bone Crista galli

Cribriform plate

Perpendicular plate (nasal septum)

Nasal bone

Inferior nasal concha

Maxilla

Palatine process of maxilla

Sphenoidal sinus Palatine bone Vomer bone Alveolar arches

Temporal bone Parietal bone

Squamosal suture

Lambdoidal suture Occipital bone

Internal acoustic meatus

Jugular foramen Sella turcica

Shier-Butler-Lewis: II. Support and Movement 7. Skeletal System © The McGraw-Hill

Human Anatomy and Companies, 2001

Physiology, Ninth Edition

Frontal bone

Crista galli of ethmoid bone

Perpendicular plate of ethmoid bone

Middle nasal concha

Maxillary sinus

Alveolar process of maxilla

Figure 7.30

Coronal section of the skull (posterior view).

Perpendicular plate of ethmoid bone

Middle nasal concha

Maxillary sinus

Alveolar process of maxilla

Cribriform plate of ethmoid bone

Ethmoid bone

Zygomatic bone

Vomer bone

Maxilla

Inferior nasal concha

Palatine process of maxilla

Cribriform plate of ethmoid bone

Ethmoid bone

Zygomatic bone

Coronoid process

Vomer bone

Maxilla

Inferior nasal concha

Palatine process of maxilla

Coronoid process Ï

Body

Figure 7.30

Coronal section of the skull (posterior view).

Coronoid process

Body

Blood Vessels Flat Man Labeled

Mandibular foramen

Mental foramen

Body

Alveolar arch

Mandibular foramen

Mental foramen

Body

Alveolar arch

Figure 7.31

(a) Lateral view of the mandible. (b) Inferior view.

largest of the conchae and are positioned below the superior and middle nasal conchae of the ethmoid bone (see figs. 7.19 and 7.25). Like the ethmoidal conchae, the inferior conchae support mucous membranes within the nasal cavity.

8. Mandible. The mandible (man'di-b'l), or lower jawbone, is a horizontal, horseshoe-shaped body with a flat ramus projecting upward at each end. The rami are divided into a posterior mandibular condyle and an anterior coronoid process (fig. 7.31).

Figure 7.32

Radiographs of the skull. (a) Frontal view and (b) lateral view.

Figure 7.32

Radiographs of the skull. (a) Frontal view and (b) lateral view.

The mandibular condyles articulate with the mandibular fossae of the temporal bones, whereas the coronoid processes provide attachments for muscles used in chewing. Other large chewing muscles are inserted on the lateral surfaces of the rami. A curved bar of bone on the superior border of the mandible, the alveolar border, contains the hollow sockets (dental alveoli) that bear the lower teeth.

On the medial side of the mandible, near the center of each ramus, is a mandibular foramen. This opening admits blood vessels and a nerve, which supply the roots of the lower teeth. Dentists inject anesthetic into the tissues near this foramen to temporarily block nerve impulse conduction and desensitize teeth on that side of the jaw. Branches of the blood vessels and the nerve emerge from the mandible through the mental foramen, which opens on the outside near the point of the jaw. They supply the tissues of the chin and lower lip.

Table 7.7 describes the fourteen facial bones. Figure 7.32 shows features of these bones on radiographs. Table 7.8 lists the major openings (foramina) and passageways through bones of the skull, as well as their general locations and the structures they transmit.

Skull Blood Vessels

Infantile Skull

At birth, the skull is incompletely developed, with fibrous membranes connecting the cranial bones. These membranous areas are called fontanels (fon"tah-nel'z), or, more commonly, soft spots. They permit some movement between the bones so that the developing skull is partially compressible and can slightly change shape. This action, called molding, enables an infant's skull to more easily pass through the birth canal. Eventually, the fontanels close as the cranial bones grow together. The posterior fontanel usually closes about two months after birth; the sphenoid fontanel closes at about three months; the mastoid fontanel closes near the end of the first year; and the anterior fontanel may not close until the middle or end of the second year.

Other characteristics of an infantile skull (fig. 7.33) include a relatively small face with a prominent forehead and large orbits. The jaw and nasal cavity are small, the paranasal sinuses are incompletely formed, and the frontal bone is in two parts. The skull bones are thin, but they are also somewhat flexible and thus are less easily fractured than adult bones.

In the infantile skull, a frontal suture (metopic suture) separates the two parts of the developing frontal bone in the midline. This suture usually closes before the sixth year; however, in a few adults, the frontal suture remains open.

Bones of the Facial Skeleton

Name and Number

Description

Special Features

Maxillary (2)

Form upper jaw, anterior roof of mouth, floors of orbits, and sides and floor of nasal cavity

Alveolar processes, maxillary sinuses, palatine process

Palatine (2)

Form posterior roof of mouth, and floor and lateral walls of nasal cavity

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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