The Skull

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Objectives

When you have completed this section, you should be able to

  • name the bones of the skull and their anatomical features; and
  • describe the development of the skull from infancy through childhood.

The skull is the most complex part of the skeleton. Figures 8.3 to 8.6 present an overview of its general anatomy. Although it may seem to consist only of the mandible (lower jaw) and "the rest," in reality the skull is composed of 22 bones (and sometimes more). Most of these bones are connected by immovable joints called sutures (SOO-chures), visible as seams on the surface (fig. 8.4). These are important landmarks in the descriptions that follow.

The skull contains several prominent cavities (fig. 8.7). The largest, with an adult volume of 1,300 to 1,350 mL, is the cranial cavity, which encloses the brain. Other cavities include the orbits (eye sockets), nasal cavity, buccal (BUCK-ul) cavity (mouth), middle- and inner-ear cavities, and paranasal sinuses. The paranasal sinuses are named for the bones in which they occur (fig. 8.8)—the frontal, sphenoid, ethmoid, and maxillary sinuses. These cavities are

Saladin: Anatomy & I 8. The Skeletal System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 8 The Skeletal System 247

Table 8.2 Surface Features (markings) of Bones

Term

Description and Example

Articulations

Condyle

A rounded knob that articulates with another bone (occipital condyles of the skull)

Facet

A smooth, flat, slightly concave or convex articular surface (articular facets of the vertebrae)

Head

The prominent expanded end of a bone, sometimes rounded (head of the femur)

Extensions and Projections

Crest

A narrow ridge (iliac crest of the pelvis)

Epicondyle

A projection superior to a condyle (medial epicondyle of the femur)

Line

A slightly raised, elongated ridge (nuchal lines of the skull)

Process

Any bony prominence (mastoid process of the skull)

Protuberance

A bony outgrowth or protruding part (mental protuberance of the chin)

Spine

A sharp, slender, or narrow process (spine of the scapula)

Trochanter

A massive process unique to the femur

Tubercle

A small, rounded process (greater tubercle of the humerus)

Tuberosity

A rough surface (tibial tuberosity)

Depressions

Alveolus

A pit or socket (tooth socket)

Fossa

A shallow, broad, or elongated basin (mandibular fossa)

Fovea

A small pit (fovea capitis of the femur)

Sulcus

A groove for a tendon, nerve, or blood vessel (intertubercular sulcus of the humerus)

Passages

Canal

A tubular passage or tunnel in a bone (condylar canal of the skull)

Fissure

A slit through a bone (orbital fissures behind the eye)

Foramen

A hole through a bone, usually round (foramen magnum of the skull)

Meatus

An opening into a canal (acoustic meatus of the ear)

Chapter 8 The Skeletal System 247

Surface Features Bone

Figure 8.2 Surface Features of Bones. (a) Skull; (fa) scapula; (c) femur; (d) humerus.

Saladin: Anatomy & I 8. The Skeletal System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

248 Part Two Support and Movement

Frontal bone-

Glabella Coronal suture Parietal bone Squamous suture Sphenoid bone Lacrimal bone Nasal bone Middle nasal concha

Infraorbital foramen Vomer

Mandible

Mandible

Infraorbital Margin

Supraorbital foramen

Supraorbital margin

Temporal bone

Ethmoid bone Perpendicular plate of ethmoid bone

Zygomatic bone

Inferior nasal concha

Maxilla

Mental protuberance -

Supraorbital foramen

Supraorbital margin

Temporal bone

Ethmoid bone Perpendicular plate of ethmoid bone

Zygomatic bone

Inferior nasal concha

Maxilla

Mental protuberance -

Mental foramen

Figure 8.3 The Skull, Anterior View.

connected with the nasal cavity, lined by a mucous membrane, and filled with air. They lighten the anterior portion of the skull and act as chambers that add resonance to the voice. The latter effect can be sensed in the way your voice changes when you have a cold and mucus obstructs the travel of sound into the sinuses and back.

Bones of the skull have especially conspicuous foramina—singular, foramen (fo-RAY-men)—holes that allow passage for nerves and blood vessels. The major foramina are summarized in table 8.3 (p. 252). The details of this table will mean more to you when you study cranial nerves and blood vessels in later chapters.

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  • Geraldine Sepulveda
    What is another name for perpendicular plate?
    7 years ago

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