4.1: Anatomy of the Skeleton: Overview and Axial Skeleton: Essential Human Anatomy and Physiology I

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BIOD 151Pages4.1: Anatomy of the Skeleton: Overview and Axial Skeleton!4.1: Anatomy of the Skeleton: Overview and Axial SkeletonSkeletal Func!onThe skeleton, comprised of a network of bones held together at joints, has many func!ons. The skeleton protects vital internal organs. For example, theskull forms a protec!ve encasement for the brain. The rib cage provides protec!on for the heart and lungs. Flat bones, such as those of the skull, ribs,and breastbone, produce blood cells.All bones are storage areas for inorganic calcium and phosphorus salts. Bones also provide sites for a"achment of muscle, tendons, and ligaments. Thelong bones, par!cularly those of the legs and the arms, permit flexible body movement. The large, heavy bones of the legs support the body against thepull of gravity.There are five types of bones, each with a dis!nct shape and form (seeFigure 4.1). The shape of a bone determines its func!on.Long bonesare longand thin, designed to support body weight and enable movement. Examples of long bones include the humerus, ulna, radius,!bia, fibula, metacarpals,and metatarsals.Flat bones(such as in the cranium) form the roof of the skull to protect the brain.Short bonesare small and cube-shaped. The carpalsin the hand and tarsals in the foot are short bones.Irregular bonesare varied in structure with ridges or irregular surfaces. The vertebrae are irregularbones designed to protect the spinal cord as well as enable spinal movements. The pelvic bones (ilium, ischium, and pubis) are also irregular bones.Sesamoid bonesare small and flat, reinforcing tendons. The patella is an example of a sesamoid bone.Figure 4.1 The five basic bone shapesFigure 4.1 The five basic bone shapes: Long, flat, short, irregular, and sesamoidBone LandmarksBones are not simply smooth surfaces. Each bone has dis!nct markings, ridges, grooves, or holes calledbone landmarks. Bone landmarks serve severalfunc!ons. Some bone landmarks allow for tendons to a"ach. Other markings indicate where nerves and blood vessels run alongside the bone orpenetrate the bone to provide blood and nervous supply. Major bone landmarks on individual bones will be discussed throughout this module. Thefollowing list of terms will help to provide a descrip!on of the types of bone landmarks:Foramen, canal, fissure -openings in bone to allow for nerves, blood supply, or a passagewaySinus -hollow chamber in bone, usually filled with airProcess, ramus -eleva!ons in boneTrochanter, tuberosity, tubercle, crest, line, spine -processes or projec!ons for tendon or ligament a"achmentHead, neck, condyle, trochlea, facet -processes designed for ar!cula!on with adjacent bonesFossa, sulcus -depressions in boneOverview of the SkeletonThe human skeleton has two main divisions: the axial skeleton and appendicular skeleton. Theaxial skeletonlies on the midline of the body andconsists of the skull, vertebral column, sternum, laryngeal skeleton, and thoracic (rib) cage (seeFigure 4.2andFigure 4.3).
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Vertebra, ethmoid bone, Cervical vertebrae, Bone Landmarks

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