I. Bones, Part 1: the Axial Skeleton (Pp. 149 150, Fig. 7.1)

Chapter 7

Bones, Part 1: The Axial Skeleton

I. Bones, Part 1: The Axial Skeleton (pp. 149–150, Fig. 7.1)

A.The 206 bones of the body are grouped into the axial and appendicular skeletons.

1.The axial skeleton is composed of the skull, vertebral column, and thorax.

2.The appendicular skeleton is made up of the upper and lower limbs, including the pectoral and pelvic girdles.

II. The Skull (pp. 150–165, Table 7.1, Figs. 7.2–7.11)

A.The skull is the most complex bony structure in the body; it is formed from the cranial and facial bones.

1.The cranium, or calvaria, is the bony cavity protecting the brain. Several cranial bones are paired, while others occur singly. 8 major bones form the calvaria (frontal, parietal, occipital, temporal, sphenoid, and ethmoid bones). (pp. 150–158, Figs. 7.2–7.10)

2.14 facial bones form the cheeks, nose, and chin (mandible, maxillae, zygomatic, nasal, lacrimal, palatine, vomer, and inferior nasal conchae). (pp. 158–160, Figs. 7.2–7.11)

B.Sutures are located between the bones of the skull. We look at sites at which the parietal bones articulate with other cranial bones. These are the four largest sutures.

1.Coronal suture

2.Squamous suture

3.Sagittal suture

4.Lambdoid suture

C.Restricted regions of the skull are formed by many parts of the skull.

1.The orbits

2.The nasal cavity

3.Paranasal sinuses

4.Hyoid bone

III. The Vertebral Column (pp. 165–173, Figs. 7.13–7.18)

A.The spinal column or spine consists of 24 individual vertebral bones, plus the two composite bones, the sacrum and the coccyx.

B.Intervertebral discs separate the 24 individual vertebrae and function as shock absorbers; they also contribute to the flexibility of the spine.

C.The 70 cm vertebral column has 5 major regions.

1.7 cervical vertebrae are in the neck

2.12 thoracic vertebrae form the rib cage

3.5 lumbar vertebrae support the lower back

4.The sacrum articulates with coxal bones

5.The tiny coccyx is the most inferior portion

D.All vertebrae have several common structural features.

1.Body (centrum)

2.Vertebral arch

3.Pedicles

4.Laminae

5.Spinous process

6.Transverse processes

7.Superior and inferior articular processes

8.Intervertebral foramina (between adjacent vertebrae)

E.Vertebral structure shows regional variations.

1.C1 – C7 are the smallest/lightest, and possess a bifid spinous process and transverse foramina; atlas, axis, and vertebra prominens are unique cervical vertebrae. (p.170, Fig. 7.17)

2.T1 – T12 articulate with ribs 1–12. Only T1 – T10 articulate directly or indirectly with the sternum.

3.L1 – L5 are massive with blunt spinous processes that face posteriorly.

4.S1 – S5 fuse to form the sacrum and shape the posterior wall of the pelvis.

5.The coccyx (or tailbone) is 3–5 variously fused vertebrae.

IV. The Thoracic Cage (pp. 173–175, Figs. 7.19–7.20)

A.The protective bony framework of the chest (thorax) includes the sternum and costal cartilages, the 12 pairs of ribs, and the thoracic vertebrae.

1.The sternum articulates with the clavicles, rib pairs 1 and 2, and costal cartilages of rib pairs 3–7.

2.The 12 pairs of ribs are classed as true or false ribs and articulate with thoracic vertebrae.

V. Disorders of the Axial Skeleton (p. 175, Fig. 7.21)

A.Abnormalities of the vertebral column include scoliosis, kyphosis, lordosis, and stenosis.

VI. The Axial Skeleton Throughout Life (pp. 176–177, Fig. 7.22)

A.Beginning with ossification of skull bones late in month 2, skull bones change throughout life. Changes are most dramatic during childhood.

B.Primary curvatures of the vertebral column are well developed at birth; secondary curvatures are usually evident by year 1.

C.Aging results in loss of bone mass.

SUPPLEMENTAL STUDENT MATERIALS to Human Anatomy, Fifth Edition

Chapter 7: Bones, Part 1: The Axial Skeleton

To the Student

Chapter 7 is an introduction to the bones of the axial portion of the human skeleton. Of the 206 total bones in the body, this chapter covers the bones of the skull, vertebral column, and rib cage that form the long axis of the body. The next chapter covers the remaining bones of the appendicular skeleton. In this chapter you will master new terminology and learn how the bones of the skull articulate with one another. Also, you will be introduced to special bone marks and features of the skeletal bones—features that you will relate in later chapters to facts about muscles, tendons, nerves, and blood vessels. For example, remembering that the lesser wings of the sphenoid bone of the skull house the optic foramina will make it easier for you to understand the passage of the pair of optic cranial nerves from the eyeball to the base of the brain. The surface markings of bones also relate to the foundations of understanding muscle attachments and movements.

Step 1: Distinguish between the axial skeleton and the appendicular skeleton.

-List the bones of the axial skeleton.

-List the bones of the appendicular skeleton.

Step 2: Understand general characteristics, bones, major sutures, and cavities of the skull.

-List all the bones of the skull and name all the other bones with which each skull bone forms an articulation.

-Distinguish among the four major sutures of the skull.

-Distinguish between cranial and facial bones.

-Describe in detail the bony framework of the orbit and the nasal cavity.

-List bones that contain paranasal sinuses. Indicate which are evident in a midsagittal view of the skull.

Step 3: Understand the general structure, functions, and parts of the vertebral column.

-Describe the general structure of the vertebral column.

-List the bones of the vertebral column.

-Explain the functions of spinal curvatures and intervertebral discs.

-Describe the general gross anatomy of a typical vertebra.

-Distinguish among cervical, thoracic, and lumbar vertebrae by listing the special characteristics of each.

-Distinguish between the intervertebral foramina and vertebral canal and explain which structures pass through each.

Step 4: Understand the general structure and functions of the bony thorax.

-Define thorax.

-List the bones that compose the bony thorax.

-Describe the gross anatomy of a rib and the sternum.

-Distinguish between a right rib and left rib.

-Distinguish between true, false, and floating ribs.

Step 5: Understand general structure of the fetal skull.

-Define fetal.

-Define fontanel.

-List the fontanels of the fetal skull and their specific locations.

-Explain the advantages an infant receives from incompletely formed skull bones and fontanels.