Skeletal Structure

1. Skeletal Structure

2. Primary Functions of Bone • supports the soft tissues of the body so that the form of the body and an erect posture can be maintained • protects delicate structures • blood cell production- RBC, WBC, & platelets produced in red marrow • storage for calcium & phosphorus; reserve lipid in yellow marrow • lever system with muscles-directs forces generated by muscles

3. Classified by Shape • long bones: longer than wide, shaft with 2 ends (femur, humerus) • short bones: length equals width (carpals, tarsals) • flat bones: thin and flat (cranium, sternum, ribs, scapula) • irregular bones: complex shapes (vertebrae, middle ear bones) • sesamoid bones: small bones formed in tendons (patella)

4. Structure • diaphysis: shaft; epiphyseal line separates it from the epiphysis • epiphysis: end; contains red bone marrow • articular cartilage: hyaline cartilage on joint surfaces to resist friction

5. Structure (cont) • periosteum: dense, white, fibrous covering around the remaining surface of the bone • outer layer: composed of connective tissue containing blood vessels • inner osteogenic layer: contains elastic fibers, blood vessels, and osteoblasts (cells responsible for forming new bone during growth and repair) • medullary cavity: space within the diaphysis that contains the fatty yellow marrow in adult bones

6. Structure (cont) • endosteum: layer of osteoblasts that lines the medullary cavity and contains scattered osteoclasts (cells that may assume a role in the removal of bone) • nutrient foramen: opening allowing vessels to enter the medullary cavity supplying the shaft of the bone (arteries to the epiphysis generally arise from the joint capsule)

7. Bone Density • Compact bone: dense bone of the diaphysis consisting of repeating patterns of solid bone tissue organized into concentric layers (long bones) • Spongy or cancellous bone: latticework (large spaces) arrangement packed with red marrow; resists stresses of weight & postural changes as well as muscular development (short, flat, irregular, and epiphysis of long bones)

9. Joint Structure

10. Classification of Joints • Fibrous (synarthroses): lacks a joint cavity and the articulating bones are held very closely together by fibrous connective tissue; they permit little or no movement • sutures • syndesmoses • gomphoses

11. Sutures • found between the bones of the skull and are united by a thin layer of dense fibrous connective tissue

12. Syndesmoses • fibrous connective tissue forms an interosseous membrane or ligament (distal articulation of the tibia and fibula, shafts of radius and ulna)

13. Gomphoses • cone-shaped peg fits into a socket (teeth)

14. Classification of Joints • Cartilaginous (amphiarthroses): lacks a joint cavity and the articulating bones are tightly connected by cartilage • synchrondrosis • symphyses

15. Synchrondrosis • connecting material is hyaline cartilage (epiphyseal plate)

16. Symphyses • connecting material is a broad, flat disc of fibrocartilage (pubic symphysis; bodies of vertebrae)

17. Classification of Joints • Synovial (diarthroses): joint cavity (space between the articulating bones) is present; freely movable. • Gliding • Hinge • Pivot • Ellipsoidal • Saddle • Ball and socket

18. Gliding • side-to-side and back-and-forth movements (biaxial); articulating surfaces are usually flat (intercarpal, intertarsal, sternum and clavicle)

20. Hinge • motions are flexion/extension (monoaxial); convex surface of one bone fits into the concave surface of another (elbow, knee)

22. Pivot • rotational movement (monoaxial); rounded, pointed, or concave surface fits into a ring formed partly by bone and partly by a ligament (atlas and axis)

24. Ellipsoidal • side-to-side and back-and-forth movements (biaxial); oval shaped condyle fits into an elliptical cavity (wrist)

26. Saddle • side-to-side and back-and-forth movements (biaxial); articular surfaces concave in one direction and convex in opposite direction (CMC of thumb)

28. Ball and socket • movement in 3 planes (triaxial); ball like surface fits into a cuplike depression (shoulder and hip)

30. Components of Synovial Joints • articular cartilage: covers surfaces of articulating bones but does not bind them together • articular capsule: surrounds the articular surfaces and encloses the joint cavity • outer layer (fibrous capsule): attached to the periosteum of articulating bones at a variable distance from the edge of the articulating cartilage • inner layer (synovial membrane): secretes synovial fluid which lubricates the joint and provides nourishment for the articular cartilage

31. Components of Synovial Joints • joint (synovial) cavity: enclosed space that surrounds the 2 articulating surfaces; contains the slippery lubricating fluid called synovial fluid • ligaments: thickened collagenous bands connecting bone to bone • extracapsular ligaments are outside of the articular capsule (MCL, LCL) • intracapsular ligaments directly attach the 2 articulating surfaces (ACL, PCL)

32. Components of Synovial Joints • articular discs (menisci): pads of fibrocartilage that lie between the articular surfaces of the bones; help maintain the stability of a joint and direct the flow of synovial fluid to areas of greatest friction; not all synovial joints have them

33. Components of Synovial Joints • bursae: saclike structures that contain synovial fluid to help reduce friction between: • skin and bone • tendons and bones • muscles and bones • ligaments and bones

36. Body planes • midsagittal: divides body down the middle • frontal (coronal): divides body to front and back • transverse: divides body into top and bottom half

37. transverse midsaggital coronal

38. Anatomical directions • superior: nearer the head • inferior: nearer the feet • lateral: away from the midline • medial: towards the midline

40. Anatomical directions • anterior: toward the front • posterior: toward the rear or back • proximal: nearer to the center • distal: farther from the center

43. http://www.loni.com/anat/dirmov/dat1.htm

44. Joint Movements • Flexion: decrease in the angle between the anterior (may be posterior--knee) surfaces of the articulating bones • Extension: increase in the angle between the anterior (may be posterior--knee) surfaces of the articulating bones • Hyperextension: continuation of extension beyond the anatomical position

45. Joint Movements • Dorsiflexion: flexion of the foot at the ankle joint • Plantarflexion: extension of the foot at the ankle joint

46. Joint Movements • Inversion: movement of the sole of the foot inward at the ankle joint • Eversion: movement of the sole of the foot outward at the ankle joint

47. Joint Movements • Abduction: movement of a bone away from the midline of the body • Adduction: movement of a bone toward the midline of the body

48. Joint Movements • Internal (medial) rotation: rotary motion in the transverse plane toward the midline • External (lateral) rotation: rotary motion in the transverse plane away from the midline • Circumduction: movement in which the distal end of a bone moves in a circle while the proximal end remains stable

49. Joint Movements • Elevation: movement in which a part of the body moves upward • Depression: movement in which a part of the body moves downward

50. Joint Movements • Protraction: movement forward on a plane parallel to the ground • Retraction: movement backward on a plane parallel to the ground