The bones that compose the adult skeleton are divided into five categories based on their shapes Figure. Their shapes and their functions are related such that each categorical shape of bone has a distinct function. Long Bones A long bone is one that is cylindrical in shape, being longer than it is wide. Keep in mind, however, that the term describes the shape of a bone, not its size. Long bones are found in the arms humerus, ulna, radius and legs femur, tibia, fibula , as well as in the fingers metacarpals, phalanges and toes metatarsals, phalanges.
Long bones function as levers; they move when muscles contract. A short bone is one that is cube-like in shape, being approximately equal in length, width, and thickness. The only short bones in the human skeleton are in the carpals of the wrists and the tarsals of the ankles.
Short bones provide stability and support as well as some limited motion. Examples include the cranial skull bones, the scapulae shoulder blades , the sternum breastbone , and the ribs. Flat bones serve as points of attachment for muscles and often protect internal organs. An irregular bone is one that does not have any easily characterized shape and therefore does not fit any other classification. These bones tend to have more complex shapes, like the vertebrae that support the spinal cord and protect it from compressive forces.
Many facial bones, particularly the ones containing sinuses, are classified as irregular bones. Short bones provide stability and support as well as some limited motion.
The term flat bone is somewhat of a misnomer because, although a flat bone is typically thin, it is also often curved. Examples include the cranial skull bones, the scapulae shoulder blades , the sternum breastbone , and the ribs. Flat bones serve as points of attachment for muscles and often protect internal organs. An irregular bone is one that does not have any easily characterized shape and therefore does not fit any other classification.
These bones tend to have more complex shapes, like the vertebrae that support the spinal cord and protect it from compressive forces. Many bones of the face, particularly the jaw bones that contain teeth, are classified as irregular bones. Tendons are a dense connective tissue that connect bones to muscles and sesamoid bones form where a great deal of pressure is generated in a joint. The sesamoid bones protect tendons by helping them overcome excessive forces but also allow tendons and their attached muscles to be more effective.
Sesamoid bones vary in number and placement from person to person but are typically found in tendons associated with the feet, hands, and knees. Table 6. Bones can be classified according to their shapes. Long bones, such as the femur, are longer than they are wide. Why are our bones full of fat? The secrets of bone marrow adipose tissue. The Endocrinologist. Anatomy, joints. Updated July 26, Moffitt Cancer Center. What is bone marrow? Chapter 4. Blood, lymphoid tissues and haemopoiesis.
Maffei FA. Intraosseous cannulation. Updated April 11, Classifications in brief: Salter-Harris classification of pediatric physeal fractures. Clin Orthop Relat Res. Chapter Ankle and foot. Wrist and hand. Your Privacy Rights. To change or withdraw your consent choices for VerywellHealth. At any time, you can update your settings through the "EU Privacy" link at the bottom of any page.
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Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Related Articles. The Anatomy of the Radius. More than Adults. The Anatomy of the Femur. The Anatomy of the Fibula. Bone Marrow: Anatomy, Function, and Treatment. The Anatomy of the Tibia. Anatomy and Common Injuries of the Feet or Ankles. The Anatomy of the Patella. How Hypophosphatasia Is Diagnosed. The Anatomy of the Cranium.
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