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Chapter 7

Chapter 7. The Skeletal System: The Axial Skeleton. I. The Axial Skeleton and Homeostasis The bones of the axial skeleton contribute to homeostasis by protecting many of the body’s organs It provides support It regulates calcium storage and release. II. Divisions of the Skeletal System

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Chapter 7

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  1. Chapter 7 The Skeletal System: The Axial Skeleton

  2. I. The Axial Skeleton and Homeostasis • The bones of the axial skeleton contribute to homeostasis by protecting many of the body’s organs • It provides support • It regulates calcium storage and release

  3. II. Divisions of the Skeletal System A. Axial Skeleton • Consists of 80 of the 206 total bones • Consists of the bones that lie around the longitudinal axis

  4. B. Appendicular Skeleton • Consists of the remaining 126 bones • Consists of the bones of the upper and lower limbs, plus the bones forming the girdles that connect the limbs to the axial skeleton

  5. III. Types of Bones • Based on shape A. Long Bones • Have greater length than width • Slightly curved for strength • Absorbs the stress of the body’s weight • Includes the femur, tibia, fibula, humerus, ulna, radius, phalanges

  6. B. Short Bones • Nearly equal in length and width; cube shaped • Includes most carpal and tarsal bones

  7. C. Flat Bones • Generally thin • Provide areas for muscle attachment • Includes the cranial bones, sternum, ribs, and scapulae

  8. D. Irregular Bones • Complex shapes • Includes vertebra, hip bones, and some facial bones

  9. E. Sesamoid Bones • Shaped like a seasame seed • Develop in certain areas where there is considerable friction, tension, and physical stress • Protect tendons from excessive wear and tear • Includes the patella (kneecaps)

  10. F. Sutural bones • Based on location • Tiny bones located in sutures (immovable joints in adults) between certain cranial bones • Vary in number from person to person

  11. IV. Bone Surface Markings • Structural features adapted for specific functions A. Depressions and Openings - Allow the passage of soft tissues - Form joints

  12. B. Processes - Projections or outgrowths - Help form joints - Serve as attachment points for connective tissue

  13. V. Skull • Includes 22 bones • Rests on the superior end of the vertebral column A. General Features and Functions • Contains several smaller cavities - Nasal septum - Orbits (eye sockets) - Paranasal sinuses

  14. Cranial bones stabilize the positions of the brain, blood vessels, lymphatic vessels, and nerves through the attachment of their inner surfaces to meninges • Other surfaces provide attachment for some muscles that produce facial expressions • Immovable joints called sutures fuse most of the skull bones together

  15. Facial bones provide support for the entrances to the digestive and respiratory systems • Protect delicate special sense organs for vision, taste, smell, and others

  16. B. Paranasal Sinuses • Not present at birth, but develop during the prepubescent years • Lined with mucous membranes that are continuous with the lining of the nasal cavity • Secretions of these membranes drain into the nasal cavity • Increase the production of mucus to help moisten and cleanse inhaled air • Serve as resonating chambers that intensify and prolong sounds of your voice

  17. C. Fontanels • “Soft spots” of a newly formed embryo that are made of cartilage or mesenchyme • Present between cranial bones • Gradually ossification occurs and they become sutures

  18. 1. Anterior fontanel - Between the two parietal bones and the frontal bone - Usually closes between 18 and 24 months after birth 2. Posterior fontanel - Between the two parietal bones and the occipital bone - Usually closes about 2 months after birth

  19. 3. Anterolateral fontanels (2) - Between the frontal, parietal, temporal, and sphenoid bones - Usually close about 3 months after birth 4. Posterolateral fontanels (2) - Between parietal, occipital, and temporal bones - Usually close by 12 months

  20. IV. Hyoid Bone • Supports the tongue • Provides attachment for some tongue muscles, and for muscles of the neck and pharynx

  21. VII. Vertebral Column • Makes up about 2/5 of your total height • Functions as a strong, flexible rod • Encloses and protects the spinal cord • Supports the head • Serves as a point of attachment for the ribs, pelvic girdle, and muscles of the back and upper limbs

  22. A. Normal Curves of the Vertebral Column • Four slight bends • Curves are relative to the front of the body 1. Convex curves (bulging out) - Also known as secondary curves because they form several months after birth

  23. a. Cervical – develops at about 3 months when an infant starts holding its head up b. Lumbar – develops when the child starts sitting up, standing, and walking

  24. 2. Concave curves (cupping in) - Also known as primary curves because they form during fetal development a. thoracic b. sacral

  25. B. Intervertebral Discs • Found between the bodies of adjacent vertebrae • Consists of an outer fibrous ring, the annulus fibrosus, and an inner highly elastic material, the nucleus pulposus

  26. Form strong joints, permit various movement, and absorb vertical shock • Compress throughout the day • Rely on blood vessels from vertebrae to obtain oxygen and nutrients and remove wastes

  27. C. Parts of a Typical Vertebra 1. Body • Superior and inferior surfaces are roughened for the attachment of intervertebral disk • Lateral surfaces contain openings through which blood vessels deliver nutrients and oxygen and remove carbon dioxide and wastes from bone tissue

  28. 2. Vertebral Arch • Surrounds the spinal cord • Single spinal nerves pass to specific regions of the body through the intervertebral foramen

  29. D. Regions of the Vertebral Column 1. Cervical Region • The transverse foramen of the cervical vertebrae allow the vertebral artery and vein and nerve fibers to pass

  30. Atlanto-occipital joints formed from the articulation of the superior articular facets of the atlas and the occipital condyles of the occipital bone permit you to nod your head • The atlanto-axial joint formed from the dens process of the axis and the vertebral foramen of the atlas allows you to pivot your head and move side to side

  31. 2. Sacrum • Serves as a strong foundation for the pelvic girdle • Four pairs of anterior and posterior sacral foramina allow passage of nerves and blood vessels

  32. VIII. Thorax • Refers to the entire chest • Thoracic cage is formed by the sternum, ribs, and the bodies of thoracic vertebrae • The thoracic cage encloses and protects the organs in the thoracic and superior abdominal cavities • Provides support for the bones of the upper limbs • Plays a role in breathing

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