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Chapter 8 Skeletal System

Chapter 8 Skeletal System. Introduction. Skeletal tissues form bones—the organs of the skeletal system The relationship of bones to each other and to other body structures provides a basis for understanding the function of other organ systems

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Chapter 8 Skeletal System

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  1. Chapter 8Skeletal System

  2. Introduction • Skeletal tissues form bones—the organs of the skeletal system • The relationship of bones to each other and to other body structures provides a basis for understanding the function of other organ systems • The adult skeleton is composed of 206 separate bones

  3. Divisions of Skeleton (Figure 8-1; Table 8-1) • Axial skeleton—the 80 bones of the head, neck, and torso; composed of 74 bones that form the upright axis of the body and six tiny middle ear bones • Appendicular skeleton—the 126 bones that form the appendages to the axial skeleton; the upper and lower extremities

  4. Axial Skeleton • Skull—made up of 28 bones in two major divisions: cranial bones and facial bones (Figures 8-2 to 8-7; Table 8-3) • Cranial bones • Frontal bone (Figure 8-8, C) • Forms the forehead and anterior part of the top of the cranium • Contains the frontal sinuses • Forms the upper portion of the orbits • Forms the coronal suture with the two parietal bones

  5. Axial Skeleton • Cranial bones (cont.) • Parietal bones (Figure 8-8, A) • Form the bulging top of the cranium • Form several sutures: lambdoidal suture with occipital bone; squamous suture with temporal bone and part of sphenoid; and coronal suture with frontal bone

  6. Axial Skeleton • Cranial bones (cont.) • Temporal bones (Figure 8-8, B) • Form the lower sides of the cranium and part of the cranial floor • Contain the inner and middle ears

  7. Axial Skeleton • Cranial bones (cont.) • Occipital bone (Figure 8-8, D) • Forms the lower, posterior part of the skull • Forms immovable joints with three other cranial bones and a movable joint with the first cervical vertebra

  8. Axial Skeleton • Cranial bones (cont.) • Sphenoid bone (Figure 8-8, E) • A bat-shaped bone located in the central portion of the cranial floor • Anchors the frontal, parietal, occipital, and ethmoid bones and forms part of the lateral wall of the cranium and part of the floor of each orbit (Figure 8-7) • Contains the sphenoid sinuses

  9. Axial Skeleton • Cranial bones (cont.) • Ethmoid bone (Figure 8-8, F) • A complicated, irregular bone that lies anterior to the sphenoid and posterior to the nasal bones • Forms the anterior cranial floor, medial orbit walls, upper parts of the nasal septum, and sidewalls of the nasal cavity • The cribriform plate is located in the ethmoid

  10. Axial Skeleton • Facial bones (Table 8-4) • Maxilla (upper jaw) (Figure 8-8, H) • Two maxillae form the keystone of the face • Maxillae articulate with each other and with nasal, zygomatic, inferior concha, and palatine bones • Forms parts of the orbital floors, roof of the mouth, and floor and sidewalls of the nose • Contains maxillary sinuses

  11. Axial Skeleton • Facial bones (cont.) • Mandible (lower jaw) (Figure 8-8, M) • Largest, strongest bone of the face • Forms the only movable joint of the skull with the temporal bone • Zygomatic bone (Figure 8-8, I) • Shapes the cheek and forms the outer margin of the orbit • Forms the zygomatic arch with the zygomatic process of the temporal bones

  12. Axial Skeleton • Facial bones (cont.) • Nasal bone (Figures 8-8, L, and 8-10) • Both nasal bones form the upper part of the bridge of the nose, whereas cartilage forms the lower part • Articulates with the ethmoid bone, nasal septum, frontal bone, maxillae, and the other nasal bone

  13. Axial Skeleton • Facial bones (cont.) • Lacrimal bone (Figure 8-8, K) • Paper-thin bone that lies just posterior and lateral to each nasal bone • Forms the nasal cavity and medial wall of the orbit • Contains groove for the nasolacrimal (tear) duct • Articulates with the maxilla and the frontal and ethmoid bones

  14. Axial Skeleton • Facial bones (cont.) • Palatine bone (Figure 8-8, J) • Two bones form the posterior part of the hard palate • Vertical portion forms the lateral wall of the posterior part of each nasal cavity • Articulates with the maxillae and the sphenoid bone

  15. Axial Skeleton • Facial bones (cont.) • Inferior nasal conchae (turbinates) • Form lower edge projecting into the nasal cavity and form the nasal meati • Articulate with ethmoid, lacrimal, maxillary, and palatine bones • Vomer bone (Figure 8-8, G) • Forms posterior portion of the nasal septum • Articulates with the sphenoid, ethmoid, and palatine bones and maxillae

  16. Axial Skeleton • Eye orbits (Figure 8-7) • Right and left eye orbits • Contain eyes, associated eye muscles, lacrimal apparatus, blood vessels, and nerves • Thin and fragile orbital walls separate orbital structures from cranial and nasal cavities and paranasal sinuses • Traumatic injuries may result in “blowout fractures” (Figure 8-7, C) • “Raccoon eyes”—clinical sign of blowout fracture (Figure 8-7, D)

  17. Axial Skeleton • Fetal skull (Figure 8-11) • Characterized by unique anatomic features not seen in adult skull • Fontanels or “soft spots” (4) allow skull to “mold” during birth process and permit rapid growth of brain (Table 8-5)

  18. Axial Skeleton • Fetal skull (cont.) • Permits differential growth or appearance of skull components over time • Face—smaller proportion of total cranium at birth (1/8) than in adult (1/2) • Head at birth is ¼ total body height; at maturity is about 1/8 body height • Sutures appear with skeletal maturity (Table 8-5) • Paranasal sinuses—change in size and placement with skeletal maturity (Figure 8-9) • Appearance of deciduous and, later, permanent teeth

  19. Axial Skeleton • Hyoid bone (Figure 8-12) • U-shaped bone located just above the larynx and below the mandible • Suspended from the styloid processes of the temporal bone • Only bone in the body that articulates with no other bones

  20. Axial Skeleton • Vertebral column (Figure 8-13) • Forms the flexible longitudinal axis of the skeleton • Consists of 24 vertebrae plus the sacrum and coccyx • Segments of the vertebral column: • Cervical vertebrae, 7 • Thoracic vertebrae, 12 • Lumbar vertebrae, 5 • Sacrum—in adult, results from fusion of five separate vertebrae • Coccyx—in adult, results from fusion of four or five separate vertebrae

  21. Axial Skeleton • Vertebral column (cont.) • Characteristics of the vertebrae (Figure 8-14; Table 8-6) • All vertebrae, except the first, have a flat, rounded body anteriorly and centrally, a spinous process posteriorly, and two transverse processes laterally • All but the sacrum and coccyx have vertebral foramen • Second cervical vertebra has upward projection, the dens, to allow rotation of the head • Seventh cervical vertebra has long, blunt spinous process • Each thoracic vertebra has articular facets for the ribs

  22. Axial Skeleton • Vertebral column (cont.) • Vertebral column as a whole articulates with the head, ribs, and iliac bones • Individual vertebrae articulate with each other in joints between their bodies and between their articular processes

  23. Axial Skeleton • Sternum (Figure 8-15) • Dagger-shaped bone in the middle of the anterior chest wall made up of three parts: • Manubrium—the upper, handle part • Body—the middle, blade part • Xiphoid process—the blunt cartilaginous lower tip, which ossifies during adult life

  24. Axial Skeleton • Sternum (cont.) • Manubrium articulates with the clavicle and first rib • Next nine ribs join the body of the sternum, either directly or indirectly, by means of the costal cartilage

  25. Axial Skeleton • Ribs (Figures 8-15 and 8-16) • Twelve pairs of ribs, with the vertebral column and sternum, form the thorax • Each rib articulates with the body and transverse process of its corresponding thoracic vertebra • Ribs 2 through 9 articulate with the body of the vertebra above

  26. Axial Skeleton • Ribs (cont.) • From its vertebral attachment, each rib curves outward, then forward and downward • Rib attachment to the sternum: • Ribs 1 through 8 join a costal cartilage that attaches it to the sternum • Costal cartilage of ribs 8 through 10 joins the cartilage of the rib above to be indirectly attached to the sternum • Ribs 11 and 12 are floating ribs, because they do not attach even indirectly to the sternum

  27. Appendicular Skeleton • Upper extremity (Table 8-7) • Consists of the bones of the shoulder girdle, upper arm, lower arm, wrist, and hand • Shoulder girdle (Figure 8-17) • Made up of scapula and clavicle • Clavicle forms only bony joint with trunk, the sternoclavicular joint • At its distal end, clavicle articulates with the acromion process of the scapula

  28. Appendicular Skeleton • Upper extremity (cont.) • Humerus (Figures 8-18 and 8-19) • The long bone of the upper arm • Articulates proximally with the glenoid fossa of the scapula and distally with the radius and ulna

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