Bones are classified according to shape and structure, and they have a variety of bone markings PDF

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Bones are classified according to shape and structure, and they have a variety of bone markings...

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Bones are classified according to shape and structure, and they have a variety of bone markings Bones are categorized by their general shape and structure. We begin our discussion with bone shapes, turn our attention to the bumps, grooves, and openings associated with bones, and then close with bone structure. Bone Shapes The adult skeleton typically contains 206 major bones. We can divide these into the following six broad categories according to their individual shapes (Figure 6–1): ■ Sutural bones, or Wormian bones, are small, flat, irregularly shaped bones between the flat bones of the skull (Figure 6–1a). There are individual variations in the number, shape, and position of the sutural bones. ■ Irregular bones have complex shapes Short bones are boxy, with approximately equal dimensions (Figure 6–1c). ■ Flat bones have thin, parallel surfaces, which produce a flattened shape (Figure 6–1d). ■ Long bones are relatively long and slender, consisting of a shaft with two ends that are wider than the shaft (Figure 6–1e). ■ Sesamoid bones are usually small, round, and flat, and shaped somewhat like a sesame seed (Figure 6–1f). They tend to develop within tendons. Except for the patellae (pa-TEL-e . ; singular, patella, a small shallow dish), or kneecaps, there are individual variations in the location and number of sesamoid bones. These variations, along with varying numbers of sutural bones, account for individual differences in the total

number of bones in the skeleton. (Sesamoid bones may form in at least 26 locations.) Bone Markings The surfaces of each bone in your body have characteristic bone markings or surface features. Examples include projections, openings, and depressions. Projections form where muscles, tendons, and ligaments attach and where adjacent bones form joints. Openings and depressions in bone are sites where blood vessels or nerves lie alongside or penetrate the bone. Detailed examination of bone markings can yield an abundance of anatomical information. For example, anthropologists, criminologists, and pathologists can often determine the size, age, sex, and general appearance of an individual on the basis of incomplete skeletal remains. Figure 6–2 introduces the prominent bone markings. It illustrates specific anatomical terms for the various projections, depressions, and openings. These bone markings provide fixed landmarks that can help us determine the position of the softtissue components of other organ systems....