1. Skeletal System
Chapter 7
Pages

2. Ch. 7 Wordbytes: ax- = axis -blast = bud carp- = wrist -clast = break
condyl- = knob
corac- = a crow's beak
cribr- = sieve
crist- = crest
fov- = pit
glen- = joint socket
meat- = passage
odont- = tooth
poie- = make/produce

3. Classification of Bones
There are 206 bones in the body grouped into two divisions:
Axial relating to the head, neck, and trunk—protect, support, or carry other body parts
E.g. head, hyoid, ribs, sternum, & vertebrae
Appendicular bones of upper & lower limbs plus girdles that connect them—help us get from place to place and to manipulate our environment

4. Figure 6.6

5. Types of Bones
Long bones- longer than wide, has shaft + 2 ends, includes all bones of limbs (- patella, wrist, ankle)
e.g. thigh, leg, arm, forearm, fingers & toes
Short bones- almost cube shaped
Most wrist & ankle bones, sesamoid bones
Flat bones- thin & extensive surface
e.g. Cranial bones, sternum, ribs & scapulae
Irregular bones- don’t fit above
e.g. vertebrae, some facial bones, hip bone

6. Bone Function Support Protection Movement Mineral homeostasis
Esp. Calcium and Phosphate
Blood cell production
Hematopoiesis in red bone marrow
Triglyceride Storage
In yellow bone marrow

7. Bone Textures Compact bone dense outer layer—looks smooth and solid
Spongy bone internal layer—honeycomb of small, needle-like pieces = trabeculae
Open spaces filled with red/yellow marrow

8. Gross Structure Parts of a long bone:
Diaphysis shaft; the long, cylindrical, main portion of the bone
Medullary cavity hollow space within diaphysis that contains yellow bone marrow
Epiphysis the distal and proximal ends of the bone
Articular (hyaline) cartilage covers joint surface to cushion and absorb stress
Metaphysis
Mature bone = where diaphysis joines epiphysis
Growing bone = contains epiphyseal plate to allow diaphysis to grow

9. Membranes:
Periosteum dense irregular tissue that surrounds bone surface where not covered by articular cartilage
Endosteum thin membrane lining medullary cavity that contains bone-forming cells

10. Figure 6.1a

11. Figure 6.1b

12. Throw me a bone!
Using the piece of paper, draw the size of your humerus!
Using a pen, please label the following:
Diaphysis
Metaphysis x2
Epiphysis x2
Articular cartilage x 2
Type of bone (long/short/flat/irregular)
Outside texture of bone
On the back of the bone, record the 6 functions of bones!

13. Parts of short, irregular, and flat bones
Thin plates of periosteum-covered compact bone on the outside, endosteum-covered spongy bone within
Not cylindrical = no epiphyses
Bone marrow (between trabeculae), but no marrow cavity.
Flat bones have diploë = internal layer of spongy bone

14. Hematopoiesis
Newborns medullary cavity and all areas of spongy bone contain red bone marrow
Adults medullary cavity extends into epiphysis, and little red marrow present in spongy bone of long bones
Blood cells produced in head of femur and humerus (long), sternum (flat), hip (irregular)
Yellow can revert to red if needed

15. Microscopic Structure of Compact Bone
Osteon structural unit of compact bone=group of hollow tubes (lamellae) of bone matrix
Haversian canal runs through the center of the osteon; contains blood vessels and nerve fibers to support cells
Volkmann’s canals connect blood and nerve supplies

16. Microscopic Structure
Matrix=
25% water, 25% collagen fibers (flexibility and strength), 50% crystallized mineral salts (hardness/resist compression)
Osteogenic cells in periosteum Osteoblasts secrete collagen fibers-
Build matrix and become trapped in lacunae
Become osteocytes- maintain bone
Osteoclasts (“bone breakers”)
Digest bone matrix for normal bone turnover

17. Compact Bone Structure
Lacunae- “lakes”; contain osteocytes
Canaliculi- little canals that allow nutrient flow from canals and between osteocytes

18. Figure 6.2a

19. Spongy Bone
Units containing trabeculae to resist stress—only a few cell layers thick
Spaces between trabeculae often contain Red Marrow
No osteons but include lacunae & canaliculae

21. Figure 6.2b
Pg. 179 Fig. 6.5

22. Bone Markings

23. Bone Development p. 133-135 Ossification 1. Formation of Bony Skeleton
2. Intramembranous Ossification
3. Endochondral Ossification
4. Postnatal Bone Growth
5. Growth in length and width

24. Bone Development
Osteogenesis and Ossification indicate the process of bone tissue formation
In embryos this leads to formation of the bony skeleton
Bone growth goes on until early adulthood
Ossification in adults is mainly for remodeling and repair of bones

25. Formation of Bony Skeleton
Mesenchyme model - replaced with bone
1. Intramembranous - Bone forms directly in mesenchyme layers (membrane like) -membrane bone
2. Endochondral - forms within hyaline cartilage developed from mesenchyme- cartilage or endochondral, bone

26. Intramembranous Ossification pg. 133 (Fig. 7.4)
Development of ossification center-
Cells differentiate=> osteogenic=> osteoblasts
Osteoblasts secrete organic matrix
Calcification- cells become osteocytes
In lacunae they extend cytoplasmic processes to each other
Deposit calcium & other mineral salts
Formation of trabeculae- spongy bone
Blood vessels grow in and marrow is formed
Mesenchyme=> periosteum
Bone Collar of compact bone forms and red marrow appears

27. Endochondrial Ossification pg. 134 Figure 7.5
Uses hyaline cartilage “bones”
Cartilage must break down as process proceeds
Primary Ossification Center
Center of hyaline cartilage shaft
Blood vessels fill perichondrium
The mesenchymal cells specialize into osteoblasts

28. Figure 6.3

29. Endochondrial Ossification
Bone Collar forms around diaphysis of hyaline cartilage
Cartilage in center of diaphysis calcifies and forms cavities
Periosteal bud invades internal cavities spongy bone forms
Diaphysis elongates and a medullary cavity forms
The epiphyses ossify

30. Figure 6.8
Fig. 7.5 pg. 134

31. Postnatal Bone Growth
Length- chondrocytes in the epiphyseal plate divide and increase cartilage layer – zone 1 - Growth
On diaphyseal side they die and are replaced by bone - zone 2 – transformation
Eroded by osteoclasts, then quickly covered with bone matrix, forming
spongy bone – zone 3 – osteogenic
Stops during adolescence
Periosteum supports surface growth for thickness – bones widen as they lengthen

32. Hormonal Regulation of Bone Growth
A symphony of hormones regulate bone growth during youth
Infancy and childhood – growth hormone – released by pituitary gland this is regulated by Thyroid hormones (T3 and T4)
Puberty – testosterone and estrogen promote adolescent growth spurt
Excess or deficits of hormones result in abnormalities – gigantism or dwarfism

33. Bone Homeostasis Remodeling & Repair
5 to 7% of bone mass recycled weekly
½ gram of calcium may enter or leave the skeleton each day
Spongy bone replaced every 3 to 4yrs.
Compact bone every 10 years

34. Bone Remodeling = Bone deposits and bone resorption
Bone deposit & bone resorption (removal) occur at the periosteal and endosteal surfaces.
Coordinated by “packets” of osteoblasts called remodeling units
Occurs where bone is injured or added strength is needed
Optimal bone deposit = diet of protein, adequate minerals (Ca, Mg, P), and Vitamins A, C, D

35. Bone resorption Done by osteoclasts= large multinucleate cells
Osteoclasts move along bone digging pits, resorption bays, breaking down bone matrix
The ruffled border secretes lysosomal enzymes and acids
These break down the organic matrix and calcium salts into a solution that can be transported into the interstitial fluid then the blood

36. Classification of Fractures
1. Nondisplaced or displaced
2. Complete (bone in two or more pieces) or Incomplete (partial break (crack))
3. Orientation of break – linear or transverse
4. Closed (simple)- not through skin or Open (compound)- broken ends break skin

37. Types of Fractures pg
Greenstick incomplete break (children—more matrix = more flexibility)
Fissured incomplete longitudinal break
Comminuted bone fragments into 3 or more pieces (elderly—brittle bones)
Transverse complete, with break at right angle to axis of bone

38. Types of Fractures pg
Oblique occurs at an angle other than a right angle
Compression bone crushed (porous bones—extreme trauma)
Spiral ragged break from twisting forces (sports fracture)
Epiphyseal separates along epiphyseal plate
Depressed broken bone pressed inward (skull fracture)

39. Repair of Fractures Involves 4 major phases
1. Hematoma formationmass of clotted blood forms at the fracture point
2. Fibrocartilaginous callus formation for debris cleanup, bone reconstruction, bone splint
3. Bony callus formation 3-4 weeks after injury to 2-3 months later
4. Bone Remodelingexcess material removed, compact bone reconstructed

41. Homeostatic Imbalances of bone
Imbalances between bone formation and bone resorption underlie nearly all diseases that influence the adult skeleton
1. Osteomalacia – inadequately mineralized bones
2. Rickets – analogous disease, but in children, very severe

42. Homeostatic Imbalances of bone
3. Osteoporosis – refers to a group of disorders in which bone resorption outpaces bone deposit
Occurs most often in aged, most often in postmenopausal women
Traditionally treated with calcium and vitamin D supplements

43. Figure 6.28
Pg. 190 – fig – similar photo

44. Homeostatic Imbalances of bone
4. Paget’s Disease – excessive bone formation and breakdown
Often discovered by accident when X rays taken for another reason
“Spotty” weakening of bone
Can affect any part of the skeleton
Spine, pelvis, femur & skull most commonly affected

45. Exercise & Bone Tissue Bone strengthened in response to use
Reabsorbed during disuse
e.g. Bone loss during bed rest, fractures in cast, astronauts with no gravity

46. Compact bone ground
Osteon
(with osteocyte inside)
Pg. 179 Fig. 6.5

47. Bone decalcified Periosteum Spongy bone Compact bone Red marrow
(spaces)
Skeletal Muscle
Blood vessels

48. Partner up! Both you and your partner should each have 13 note cards.
Pick a side (right or left)—these will be the terms that you write on your cards.
When both of you have finished recording the terms, try your best to match them up (they’re not in the correct order)!
You will be quizzed on these terms in class next time!

49. Write these terms, one per card: Left: Right:
ax-
-blast
carp-
-clast
condyl-
corac-
cribr-
crist-
fov-
glen-
meat-
odont-
poie-
Axis
Break
Bud
Crest
Crow’s beak
Joint socket
Knob
Make/produce
Passage
Pit
Sieve
Tooth
Wrist

50. Let’s see how you did!
Also, don’t forget to write the correct corresponding term on the other side of your note card to study from!