1. Chapter 7
Skeletal System

2. Functions of Skeletal System: 1. Support 2. Protection 3
Functions of Skeletal System: 1. Support Protection 3. Produces blood cells Stores inorganic materials

3. Classification – bones classified by shape:
1. Long
2. Short
3. Flat
4. Irregular
5. Sesamoid

4. Structure of Long Bone
Epiphysis- expanded portion at end, forms joint.
Epiphyseal disk (line)-growth plate
Diaphysis- shaft of bone
Medullary cavity-hollow chamber in center
Spongy bone- cancellous bone, found mainly in epiphysis
Compact bone-tightly packed tissue
Periosteum-tough, vascular covering
Endosteum- membrane of bone forming cells
Articular cartilage-layer of hyaline cartilage on epiphysis of bone

5. Structure of a Long Bone
Red marrow- formation of red blood cells, white blood cells and platelets.
Found in flat bones and epiphysis
Yellow marrow- stores
fats, no blood cell
production.
Found in diaphysis

6. Compact vs. Spongy Bone Perforating(Volkmann’s)
canal- Connects central
canals
Trabeculae-bony plates
of spongy bone
Canaliculi- canals btwn
osteocytes
Osteocyte-Bone cells
Lacunae- space in bone
containing osteocytes

7. Compact vs. Spongy Bone

8. Bone Structure Animation
structure of bone animation

9. Osteoblast vs. Osteoclast
Osteoblast- bone forming cells which deposit Calcium and Phosphorous into the dense collagen framework.
Osteoclast- Large multinucleated cells formed from fusing white blood cells.
Secrete an acid which breaks down the bony matrix
Both work together over a person’s lifetime to remodel bone and allow for resorption on minerals.

10. Osteoblast vs osteoclast
osteoblast osteoclast animation

11. Homeostasis of Bone Tissue

12. Bone Development – 2 Types:
1. Intramembranous ossification (changing cartilage to bone) (ex. - skull)
layers of undifferentiated connective tissue appear at sites of future bone
connective tissue cells differentiate into osteoblasts (cells that build bone) around blood vessels
osteoblasts become osteocytes (mature bone cells) when completely surrounded by a bony matrix
Connective tissue on surface forms the periosteum

13. Intramembranous Ossification

14. Intramembranous Ossifiction

15. 2. Endochondral ossification (remainder of skeleton)
Hyaline cartilage models form
at sites of future bone
Cartilage cells degenerate
over time
osteoblasts form bone over
cartilage
osteoblasts become
osteocytes when completely
surrounded by a bony matrix

16. Ossification Animation

17. Endochondral Ossification

18. Bone Development
In a long bone, hyaline cartilage is replaced by bony tissue in the center of the diaphysis first (primary ossification center)
Bone develops from this point towards the end of the bone
Secondary ossification centers appear in the epiphysis last.

19. Bone Development

20. Growth of Bones 1. Epiphyseal disk – area of
growth; separates epiphysis
from diaphysis; 4 layers:
1. Resting cells – closest to
end; do not add length but
act as anchor
2. Reproducing cells -
as they reproduce, they
lengthen the bone 1.

21. Growth of Bones 3. Mature cells – growing and accumulating Ca
4. Degenerating cells &
osteoblasts depositing
bony tissue

22. Epiphyseal Plate Video

23. Epiphyseal disk Bones continue to lengthen until epi. disks
are ossified (approx. 21
yrs. of age)
Bones thicken through-
out life as compact bone
is added under peri-
osteum
Hyaline cartilage on ends remains

24. Bone Growth Video

25. Epiphyseal disk
1. Radial growth plate→ 2. Fracture – distal end of radius → Digital growth plate (in fingers) (2 ½ yr. old)→

26. Fractures Greenstick- incomplete break in convex surface
Fissured- incomplete longitudinal break
Comminuted-complete, fragments bone
Transverse- complete break at right angle
Oblique- complete at angle other than right angle
Spiral- complete, caused by twisting of bone

27. Fracture Repair 4 stages
Blood escapes from blood vessels and from hematoma.
Spongy bone forms near blood vessels, fibrocartilage forms in distant regions (within days to weeks)
Bony callus forms from cartilaginous callus similar to bone formation
Osteoclasts remove excess bone to restore to original

28. Bone Fracture Video

29. Factors Affecting Bone Growth (Nutrients)
Deficiency
Effect
Vit D (for Ca absorption)
dehydrocholesterol
soft bones (rickets/osteomalacia)
Vit A (for osteoblast & osteoclast activity)
slow bone development
Vit C (for collagen synthesis)
fragile bones

30. Rickets/Osteomalacia

31. Factors Affecting Bone Growth (Hormones)
Deficiency Effect Pituitary growth Pituitary dwarfism hormone (excess – pituitary (stimulates cell division gigantism/acro- in the epi. disks) megaly) Thyroid hormone premature disk (stimulates cartilage ossification-growth replacement in disk) stunt ed

32. Pituitary dwarfism

33. Acromegaly Yao Defen is 34 yrs. old & The world’s tallest
female at 7ft. 8 in!!

34. Factors Affecting Bone Growth (Hormones & Exercise)
Deficiency Effect Sex hormones stimulate ossifi- (cause growth of cation of disks; long bones; estrogen stop bone length stronger than androgen) Physical stress bone thins & weak- (stimulates bone width; ens; atrophy hypertrophy)

35. 2 divisions of skeleton:
Axial –
skull, vertebrae, sternum, ribs (thorax), hyoid bone
Appendicular –
pectoral & pelvic girdles, upper & lower limbs
Human Skeleton – composed of 206 bones (extra – sutural)

36. Axial vs. Appendicular Skeleton

37. Surface Markings on Bone
Surface of bones have various structural features for specific functions
Depressions & Openings:
Foramen
Meatus
Sinus

38. Foramen
Opening for b.v., nerves, ligaments (ex.-foramen magnum)

39. Meatus
Tubelike passageway (ex.-external auditory meatus)

40. Sinus
Cavity within a bone (ex.-frontal sinus)

41. Surface Markings on Bone
Processes that Form Joints:
Condyle
Head
Facet

42. Condyle
Rounded process for articulation w/another bone (ex. – mandibular condyle)

43. Head
An enlargement at the end of a bone (ex.-head of femur)

44. Facet
Small, nearly flat surface where 2 bones articulate (ex.-vertebral facet)

45. Surface Markings on Bone
Processes that Connective Tissue Attaches To:
Tuberosity
Spine
Trochanter
Crest
Process

46. Tuberosity
Knoblike process (ex.-ischial tuberosity)

47. Spine
Thornlike ridge or projection (ex.-spine of scapula)

48. Trochanter
Large process or projection (ex.-trochanter of femur)

49. Crest
Ridgelike projection (ex.-iliac crest)

50. Process
Prominent projection on a bone (ex.-spinous process)

51. Surface Markings – Misc.
Suture - Interlocking lines where bones meet (ex.-coronal suture)