The Skeletal System

1. The Skeletal System • Organs – bones, joints, cartilage, ligaments

2. Functions A. Support – hard framework that supports and anchors all soft organs of the body – Ex. Legs act as pillars to support trunk, rib cage supports thorax wall B. Protection – skull protects brain, ribs protect heart/lungs, zygomatic arch protect the eye C. Movement – skeletal muscles, attached to bone by tendons, used the bones as levers to move the body and it’s parts; arrangement of bones and the design of joints determine the types of movement possible

3. Functions (con’t) D. Storage • Fat stored in the internal cavities • Bone matrix stores minerals (Ca+2) – “deposits” and “withdrawals” of minerals to and from bones goes on almost continuously E. Blood cell formation (hemopoiesis) • Carried on in red bone marrow; hemopoietic tissue – Fig. 6-5 • Hemopoietic tissue is found in the ends of long bones • Transformed to yellow bone marrow, an inactive fatty tissue, as person ages

4. Classification of Bones A. Classified according to shape B. Contain different proportions of 1. Compact bone (smooth & homogeneous) 2. Spongy (cancellous) bone – spaces & trabeculae (beams)

5. Classification of Bones • Long bones 1. Longer than they are wide 2. Consists of a shaft plus two ends 3. Primarily compact bone; but may contain substantial amounts of spongy bone

6. Classification of Bones D. Short bones 1. Roughly cube-like – ex. Wrist/ankle 2. Mostly spongy bone; compact bone only provides a thin surface

7. Classification of Bones E. Flat Bone 1. Thin, flattened and usually a bit curved – sternum, ribs, most skull bones 2. Two roughly parallel compact bone surfaces with a layer of spongy bone between

9. Classification of Bones F. Irregular bones – some skull, hip, vertebrae 1. Fit none of the preceding classes 2. Complex shapes 3. Mainly spongy bone enclosed by thin layers of compact bone G. Sesamoid bones –a special type of short bone embedded within a tendon; ex. - patella

11. Bone Structure – 2 levels A. Gross Anatomy – What you can see with the naked eye - Fig. 6-1 B. Microscopic Anatomy – Fig. 6-2, 6.3

12. Gross Anatomy Long Bone – most have the same basic structure 1. diaphysis (shaft) – hollow tube of hard compact bone 2. medullary cavity – hollow area; contains yellow bone marrow 3. epiphyses – bone end or extremities; usually more expanded than diaphysis; thin layer of compact bone forms exterior; interior spongy bone filled with red bone marrow 4. epiphyseal line/plate – remnant of cartilage present at junction of diaphysis & epiphyses in young bones; growth are that allows bones to lengthen 5. articular cartilage – found where long bones articulate (join); cushions the bone ends and absorbs stress during joint movement 6. periosteum – outer surface of diaphysis; richly supplied with nerve fivbers, lymphatic vessels, and blood vessels which enter via nutrient canals 7. endosteum – fibrous membrane that lines medullary cavity

13. Gross Anatomy

14. Microscopic Anatomy Compact bone – Fig. 6-2, 6-3 1. Haversian system – structural unit; circular 7 tubelike; composed of calcified matrix arranged in multiple layers (one inside the other – like an onion) 2. osteocytes (bone cells) – regulate the removal of calcium from bone matrix Osteocyte (within lacuna)

15. Microscopic Anatomy Spongy bone 1. Trabeculae – structural unit 2. Osteocytes – only a few cell layers thick; no Haversian system 3. Nutrients reach osteocytes by diffusion

16. Microscopic Anatomy Cartilage – Fig. 6-4 1. Fibers embedded in gel (not calcified matrix) 2. Chondrocytes (cartilage cells) 3. Cartilage contains no blood vessels; nutrients diffuse through matrix 4. Function a. supports & reinforces b. cushioning properties c. resists compressive stress (articular cartilage)

17. Microscopic Anatomy

18. Bone Development(osteogensis) – Fig. 6-5 A. Intramembranous ossification – flat bones form from fibrous membrane – ex. Skull, clavicle, ribs B. Endochondral ossification – bone formation from hyaline cartilage structures; most bones form this way; osteoblasts – bone forming cells osteoclasts – bone reabsorbing cells

19. EndochondralOssifcation – Fig. Cartilage model is the starting point

20. EndochondralOssifcation – Fig. Formation of a bone collar around the shaft of the hyaline cartilage model

21. EndochondralOssifcation – Fig. Cartilage matrix calcifies; chondrocytes die

22. EndochondralOssifcation – Fig. Invasion of internal cavities by periosteal bud and spongy bone formation (3 mo. embryo)

23. EndochondralOssifcation – Fig. As the primary ossification enlarges, osteoclasts break down spongy bone & form medullary cavity

24. Ossification of epiphyses - development of secondary ossification centers in epiphyses; cartilage begins to become bone - when complete cartilage remains only at epiphyseal surfaces (articlular cartilage) and at the epiphyseal plate

25. EndochondralOssifcation – Fig. 6-5 Bone growth continues during infancy & youth - long bones lengthen at epiphyseal plate - long bones thicken by a process called appositional growth (inside breaks down at a slower rate than exterior builds up) - some facial bones (nose, mandible) grow throughout life

26. EndochondralOssifcation – Fig. 6-5

27. The Skeleton – 206 bones Axial skeleton – forms long axis of body & includes the bones of the skull, vertebral column, and rib cage Appendicular skeleton – bones of upper and lower extremeties and girdles (shoulder/hip)

28. The Axial Skeleton – 80 bones A. Skull – body’s most complex bony structure – Fig. 6-8 1. Cranial bones (8) a. site of attachment of head muscles b. enclose & protect brain & organs of hearing & equilibrium

29. Cranial Bones (red highlight)

30. The Axial Skeleton – 80 bones 2. Facial bones (14) a. form framework of face b. hold eyes in an anterior position c. provide cavities for the organs of taste & small and openings for the passage of air & food d. secure teeth e. anchor the facial muscles of expression

31. Facial Bones (black & nasal concha)

32. The Axial Skeleton – 80 bones 3. Middle ear bones (6) – used in sense of hearing

33. The Axial Skeleton – 80 bones 4. Sutures – interlocking joints of skull bones

34. The Axial Skeleton – 80 bones B. Vertebral column – 26 irregular bones that form a flexible curved rod that supports the body trunk 1. Provides attachment points for ribs & muscles of back 2. Division of spine – curvature increases strength, resilience & flexibility of spine, making it function like a spring rather than a rod

35. Vertebral Column

36. The Axial Skeleton – 80 bones C. Thorax – 12 pairs of ribs (both male & female), sternum, thoracic vertebrae, costal cartilage 1. Forms protective cage around thoracic organs 2. Supports shoulder girdles & upper limbs 3. Provides attachment points for the muscles of the back, chest, & shoulders 4. Intercostal spaces – occupied by inter- costal muscles which elevate & depress during breathing

37. Rib Cage

38. The Appendicular Skeleton 126 bones A. Adapted to carry out movement B. Pectoral (shoulder) girdle – clavicle, scapula C. Arm/hand – humerus, radius, ulna, carpals, metacarpals, phalanges D. Pelvic girdle – coxal bones (ilium, ischium, pubic) E. Leg/feet – femur, tibia, fibula, patella, tarsals, metatarsals, phalanges

39. The Appendicular Skeleton Pectoral Girdle

40. The Appendicular Skeleton Arm/hand

41. The Appendicular Skeleton Pelvic Girdle

42. The Appendicular SkeletonLeg/feet

43. Male & Female Skeletal Differences A. Most male skeletons are larger (no great functional importance) B. Structural difference in pelvis 1. Male - narrower 2. Female – structured to cradle baby; broader, shallower, lighter, rounder C. Pelvic brim 1. Male – basically heart shaped 2. Female – wider, oval from side to side D. Coccyx 1. Male – narrow, longer; less movable; curves ventrally 2. Female – wider, shorter; more movable; straighter

44. Male & Female Skeletal Differences

45. Male & Female Skeletal Differences

46. Articulations (joints) • Two different ways to classify Structural classification – based on material that binds fibrous cartilaginous synovial Functional classification – based on amount of movement

47. Articulations Synarthroses – immovable joints; fibrous connective tissue grows between the articulating bones; - ex. Sutures of cranial bones

48. Articulations Amphiarthroses – slightly moveable; cartilage or fibrous tissue connects articulating bones – ex. Symphysis pubis, ligaments, fibrous membrane between radius & ulna

49. Articulations Diarthroses – allow considerable movement; Fig. 6-20, 6-21, Table 6-7 1. Ball & socket a. shoulder & hip joints b. this type of joint permits the widest range of motion

50. Articulations • Diarthroses – allow considerable movement; Fig. 6-20, 6-21, Table 6-7 2. Hinge joints a. elbow & knee, fingers, toes b. movement in 2 directions – flexion (bending), extension (straightening)