1. Skeletal System Anatomy & Physiology

2. The Skeletal System Your skeleton comprises ~ 20% of your total body mass There are 206 bones in your body, separated into 2 divisions: –1. Axial skeleton: head, vertebrae and rib cage –2. Appendicular Skeleton: pelvis, scapulae and limbs

3. Axial: pink Appendicular: green

4. 5 Functions of Bones 1. Support: legs support the weight of body, ribs support thoracic cavity 2. Protections: protects all soft tissue organs 3. Movement: muscles use bones as levers, allowing for movement 4. Storage: fat stored in internal cavities of bones; calcium and phosphorus also stored 5. Blood Cell Formation: hematopoesis; the production of blood cells within marrow cavities

5. Bone Types There are two types of bones: –1. Compact bone: dense bone which is smooth and solid; surrounds all bone; appears dense –2. Spongy bone: internal portion of bone; consists of small needle-like projections of bone called trabeculae with many open spaces filled with marrow

6. Bone Types

7. Bone Classification Bones come in many shapes and sizes and are classified into 4 distinct groups: 1.Long Bones oLonger than wide oBuilt to absorb stress oConsists of a shaft and 2 heads at each end oMostly compact but some spongy bone internally oExamples: all bones of limbs except patella, carpals and tarsals

8. Long Bone: the femur

9. Bone Classification 2. Short Bones oRoughly cube-like oContains mostly spongy bone oThin layer of compact bone on surface oExamples: carpals and tarsals oSesamoid bone: a bone embedded in a tendon; varies in size and numbers/each individual; act to alter the pull of a tendon; i.e. patella

10. Short Bones: carpals of the wrist

11. Bone Classification 3. Flat Bones oThin, flattened and usually curved o2 parallel compact surfaces with a spongy layer between oexamples: sternum, ribs and skull bones

12. Bone Classification 4. Irregular Bones oDo not fit any other classification oComplicated shapes oMostly spongy with thin compact layer o Examples: vertebrae and hip bones

13. Anatomical Structure of a Long Bone Diaphysis: shaft of long bone; walls made of compact bone Periosteum: fibrous sheath that covers long bones –Highly vascularized –Functions in bone nourishment and attachment sites

14. Anatomical Structure of a Long Bone Sharpey’s Fibers: connective tissue fibers that secures the periosteum to underlying bone Epiphyses: ends of long bones –Enlarged for muscle attachment –Predominately spongy bone

15. Anatomical Structure of a Long Bone Articular Cartilage: covers ends of epiphyses and provides a slippery surface that decrease friction at joint surfaces Medullary Cavity: holds marrow in center of diaphysis –Yellow marrow: fat storage in adults, found in medullary cavity –Red marrow: found in diaphysis of infants, in flat bones & epiphyses of adults; makes red blood cells

16. Anatomical Structure of a Long Bone Endosteum: sheath covering medullary cavity

17. Bone Composition Bone contains inorganic & organic components –Inorganic calcium carbonate & calcium phosphate; provides hardness –Organic collagen: to further reinforce the matrix

18. Osteoporosis: brittle bones Normal Spongy Bone Osteoporotic Spongy Bone

19. Bone Cells: 3 Types Osteoblasts: arise from embryonic cells and found on outer surfaces of adult bones; aid in matrix production Osteocytes: mature bone cells; trapped in lacunae Osteoclasts: secretes substances that dissolve mineral salt crystals

20. Bone – cell types “Ruffled” Border Note locations of Osteoclasts & osteoblasts

21. Microscopic Anatomy of Bone Lacunae: cavities in bones where osteocytes are found Lamellae: a circular layer of bone

22. Microscopic Anatomy of Bone Haversion Canals: a system of interconnecting canals in adults compact one; runs lengthwise through bone, carrying blood vessels and nerves to all areas of bones Canaliculi: tiny canals that connect all the bone cells to the nutrient supply; radiate outward from Haversion Canals

23. Microscopic Anatomy of Bone Volkmann’s Canals: communication system from exterior of bone to interior; runs at right angle to diaphysis Osteon/Haversion Systems: each haversian canal with lamellae, osteocytes and caniliculi

24. Haversion Systems

25. Bone Development Embryonic Skeleton: predominately hyaline cartilage Fontanels: in skull at birth –Allows for growth of brain

26. Bone Development Young child to late adolescence: cartilage replaced by bone –Epiphyseal Growth Plates: allows for interstitial growth (lengthwise) –Cartilage near the epiphyses regenerates –Cartilage near the diaphysis hardens to bone eventually they’ll meet, halting lengthwise growth

27. Epiphyseal Growth Plate

28. Epiphyseal Growth Plates

29. Bone Development & Growth

30. Ossification The replacement of cartilage by bone Cartilage is covered by osteoblasts Cartilage is “eaten” away, leaving the medullary cavity open within the bone

31. Appositional Growth Outward growth of bone during adulthood –Bones change based on calcium levels & muscles acting on the skeleton –Decreased blood calcium leads to bone breakdown –Increased demand by muscles on bones causes bone to thicken –Weight gain also increase bone diameter –Adult bone constantly remodels (breakdown & growth) to help maintain homeostasis of blood mineral levels

32. Skeletal System Axial Skeleton

33. Includes 80 bones of the skull, vertebral column and bony thorax Functions: –Supports head, neck & trunk –Protects brain, spinal cord and thoracic organs

34. Skull Composed of flat bones Function: –Used for attachment of head muscles & protects the brain

35. Sutures of the Skull Sutures: interlocking joints that unite skull bones –Coronal: where parietal bones meet frontal –Sagittal: where 2parietal bones meet superiorly –Squamos: where parietal and temporal bones meet on lateral aspects of skull –Lambdoidal: where parietal bones meet occipital bones meet posteriorly

36. Vertebral Column aka the Spine Location: runs from the base of the skull to the coccyx (tailbone) Function: –Surrounds and protects the spinal cord –Provides attachment sites for ribs and back muscles

37. Vertebral Column Characteristics –26 interconnected irregular bones –Provides a flexible, curved structure –Serves as axial support of the trunk

38. Vertebral Column Curvatures of the Spine: –S-shaped to prevent shock to head in motion –Allows for trunk flexibility –Increases resiliency & flexibility of the spine –Functions like a spring, not a rod Cervical & Lumbar Curves: concave posteriorly Thoracic & Sacral Curves: convex posteriorly

39. Curvatures of the Spine

40. Abnormal Curvatures of the Vertebral Column Lordosis: aka sway back –An accentuated lumbar curve Kyphosis: aka hunchback –An exaggerated thoracic curve Scoliosis: the twisted disease –An abnormal lateral curvature in the thoracic region –Typical in girls in late childhood

41. Lordosis & Kyphosis

42. Scoliosis

43. Cervical Vertebrae 7 total extending from base of skull to ~ shoulder line Numbered C1-C7 Smallest & lightest vertebrae Unique vertebrae –Atlas or C1: no body; holds the occipital bone, allows nodding motion (“yes”) –Axis or C2: acts as a pivot for rotation; shake head (“no”)

44. Thoracic Vertebrae 12 total; runs through mid-back Numbered T1-T12 Larger than cervical Longer, palpable spinous processes Ribs attach here posteriorly

45. Lumbar Vertebrae 5 total Numbered L1-L5 Huge bodies and short spinous processes Holds most of body weight & stress; very sturdy

46. Sacrum & Coccyx Sacrum –Formed from 5 fused vertebrae –Numbered S1-S5 –Makes up posterior wall of pelvis –Strengthens & stabilizes pelvis Coccyx –4 fused vertebrae

47. Ligaments of the Spine There are several; only 2 you need to know –Anterior Longitudinal Ligament: resists back hyperextension –Posterior Longitudinal Ligament: resists back flexion

48. Intervertebral Discs Cushion-like pads between vertebrae Asts as shock absorbers during motion Makes up ~25% of length of column Flattens during the day

49. Intervertebral Discs

50. Ribs Flat bones 12 total pairs Attach posteriorly to thoracic spine Function: –Protect thoracic organs True Ribs: the superior 7 pairs –Attach directly to sternum by costal cartilage False Ribs: the inferior 5 –8-10: join each other by cartilage and indirectly attach to sternum –11& 12: the floating ribs, no anaterior attachment

51. Rib Cage

52. Pelvis Has 2 regions: true and false pelvises False pelvis superior to true pelvis True pelvis dimensions are a concern to child-bearing women Pelvic structure differs between men and women

54. Gender Difference of Pelvis Men –Narrow outlet –Heavier & thicker bone structure –Ilia less flared, more vertical –Sacrum long and curved –Ischia close together –Less rounded pubic arch Women –Inlet circular & large –Pelvis shallow, lighter & thinner –Ilia flare laterally –Sacrum shorter & less curved –Ischia farther apart & shorter –Pubic arch is more rounded