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C H A P T E R 3 The Skeletal System 1 Around 206—some people develop varying numbers of miscel- laneous bones, either sesamoid bones , which form within some tendons as a response to stress (such as the patella) or sutural bones , which develop within the sutures of the skull. C H E C K P O I N T : Overview: Skeletal System 1. The average human adult has ___________ bones in their body, while the average new- born has ___________ bones in theirs. 2. Explain the difference. 49 C H A P T E R 3 The Skeletal System Overview: Skeletal System We are born with 270 bones in our bodies, and even more bones form during childhood. By the time we reach adulthood though, several separate bones have fused together so that the number of our bones has decreased to around 206 1 , which make up the adult skeletal system. An example of this reduction occurs in each half of our pelvis, where three separate bones— the ilium, the ischium, and the pubis—fuse into one single bone called the os coxa . The skeletal system is further divided into the axial skeleton, consisting of the bones of the skull, vertebral column, and the thoracic cage; and the appendicular skeleton, which con- sists of the bones of the upper and lower extremi- ties along with their associated girdles (Table 3.1). Naming Bony Processes and Other Landmarks Bony landmarks are various ridges, spines, depres- sions, pores, bumps, grooves, and articulating struc- tures on the surface of bones. These structures allow for the passage of blood vessels and nerves; for joints between bones; and for the attachment of liga- ments, muscles, and tendons. Therefore, a working knowledge of the names of these structures will be a valuable asset when considering the structure and function of these surface features. Some of the most commonly encountered bony landmarks are listed in Table 3.2. Table 3.1 Summary of the Bones of the Adult Skeletal System Axial Skeleton—80 Bones Appendicular Skeleton—126 Bones Skull and Hyoid 23 bones Pectoral Girdle 4 bones Inner Ear Ossicles 6 bones Upper Extremities 60 bones Vertebral Column 26 bones Pelvic Girdle 2 bones Sternum and Ribs 25 bones Lower Extremities 60 bones Total – 206 Bones Bonus Question: Using this information as a reference, how would this table appear if it was a list of the bones for a newborn? bro78143_03_49-144.QXD 9/17/07 2:11 PM Page 49
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C H A P T E R 3 The Skeletal System 50 Table 3.2 Common Bony Landmarks FEATURE DESCRIPTION EXAMPLE Landmarks of Articulation: Condyle: Smooth, rounded knob occipital condyle of skull Facet: Smooth, flat, slightly concave or convex articular facets of vertebrae articular surface Head: Prominent expanded end of a bone, head of the femur sometimes rounded Elevated Landmarks: Process: Any bony prominence mastoid process of the skull Spine: Sharp, slender, or narrow process spine of the scapula Crest: Narrow ridge iliac crest of the pelvis Line: Slightly raised, elongated ridge nuchal lines of the skull Tuberosity: Rough surface tibial tuberosity Tubercle: Small, rounded process greater tubercle of the humerus Trochanter: Massive processes unique to the femur
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  • Fall '13
  • JessicaKrol
  • Bones of the head and neck, ___________________________________________, ____________________________________________

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