Chapter Summary

Internal Affairs (201.0K)

Organization of the Skeletal System

1. The axial skeleton consists of the skull, auditory ossicles, hyoid bone, vertebral column, and rib cage.
2. The appendicular skeleton consists of the bones within the pectoral girdle, upper extremities, pelvic girdle, and lower extremities.

Functions of the Skeletal System

1. The mechanical functions of bones include the support and protection of softer body tissues and organs. In addition, certain bones function as levers during body movement.
2. The metabolic functions of bones include hemopoiesis and mineral storage.

Bone Structure

1. Bone structure includes the shape and surface features of each bone, along with gross internal components.
2. Bones may be structurally classified as long, short, flat, or irregular.
3. The surface features of bones are classified as articulating surfaces, nonarticulating prominences, and depressions and openings.
4. A typical long bone has a diaphysis, or shaft, filled with marrow in the medullary cavity; epiphyses; epiphyseal plates for linear growth; and a covering of periosteum for appositional growth and the attachments of ligaments and tendons.

Bone Tissue

1. Compact bone is the dense outer portion; spongy bone is the porous, vascular inner portion.
2. The five types of bone cells are osteogenic cells, in contact with the endosteum and periosteum; osteoblasts (bone-forming cells); osteocytes (mature bone cells); osteoclasts (bone-destroying cells); and bone-lining cells, along the surface of most bones.
3. In compact bone, the lamellae of osteons are the layers of inorganic matrix surrounding a central canal. Osteocytes are mature bone cells, located within capsules called lacunae.

Bone Growth

1. Bone growth is an orderly process determined by genetics, diet, and hormones.
2. Most bones develop through endochondral ossification.
3. Bone remodeling is a continual process that involves osteoclasts in bone resorption and osteoblasts in the formation of new bone tissue.

Skull

1. The eight cranial bones include the frontal (1), parietals (2), temporals (2), occipital (1), sphenoid (1), and ethmoid (1).
1. The cranium encloses and protects the brain and provides for the attachment of muscles.
2. Sutures are fibrous joints between cranial bones.

2. The 14 facial bones include the nasals (2), maxillae (2), zygomatics (2), mandible (1), lacrimals (2), palatines (2), inferior nasal conchae (2), and vomer (1).
1. The facial bones form the basic shape of the face, support the teeth, and provide for the attachment of the facial muscles.
2. The hyoid bone is located in the neck, between the mandible and the larynx.
3. The auditory ossicles (malleus, incus, and stapes) are located within each middle-ear chamber of the petrous part of the temporal bone.

Vertebral Column

1. The vertebral column consists of 7 cervical, 12 thoracic, 5 lumbar, 4 or 5 fused sacral, and 3 to 5 fused coccygeal vertebrae.
2. Cervical vertebrae have transverse foramina; thoracic vertebrae have fovea for articulation with ribs; lumbar vertebrae have large bodies; sacral vertebrae are triangularly fused and contribute to the pelvic girdle; and the coccygeal vertebrae form a small triangular bone.

Rib Cage

1. The sternum consists of a manubrium, body, and xiphoid process.
2. There are seven pairs of true ribs and five pairs of false ribs. The inferior two pairs of false ribs (pairs 11 and 12) are called floating ribs.