Chapter 6

General information

Bones, cartilage, ligaments

18%

Functions:

Support, protection (skull, thorax, pelvis, spine), contains 98% of all calcium, hemopoiesis, movement, mineral homeostasis, triglyceride storage

Shapes of bones

Long bones-longer than it is wide

Ex. Upper and lower appendages

Short bones

Ex. Carpels and tarsels

Flat bones- two layers of compact with spongy in the middle

Ex. Sternum scapula, os coxa, ribs, cranium

Irregular bones- no set shape

Ex. Facial, vertebrae

Parts of a long bone

Diaphysis-shaft

Epiphysis- rounded ends (enlarged)

Metaphysis- joins the diaphysis to the epiphysis

The epiphyseal plate/line is located in the metaphysis

— responsible for growth in length, actively growing cartilage (mitosis)

—14 for females is when the plate ossify (harden), 24 for males

— Articular Cartilage (hyaline)

— Perioteum- layer of Connective tissue wrapping around the diaphysis

  • fibrous layer- dense irregular

  • osteogenic- embryonic cells, repair the bone

— Sharpeys (perforating) fibers- tiny collegen threads that anchor the periosteum to the bone.

— Medullary cavity- hollow space in bones to reduce bone weight.

— Endosteum - layer of reticular Connective tissue

Matrix

15% water

30% collagen fibers

55% salts

  • Calcium phosphate-Most abundant (calcium salts deposited on collagen fibers)

  • Calcium hydroxide

  • Hydroxyapatite

Collagen Fibers-Strong

Calcification- Ca salts harden on collagen fibers

Bones Cells

Osteoprogenitor cells

  • unspecialized stem cells from mesenchyme

  • only mitotic bone cell

  • endosteum, periosteum, central canal

  • specialize into osteoblasts

Osteoblasts

  • nonmitotic

  • produce collagen fibers of matrix

  • responsible for bone deposition

Osteocytes in lacunae

  • former osteoblasts completely enclosed in matrix

  • canaliculi allow cells to remain in contact

  • gap junctions

Osteoclasts (Pac-Man)

  • Large, monocytes (White blood cells) merge to create osteoclasts

  • Activated by PTH (parathyroid hormone)

  • resorption: removing Calcium from your bones and depositing it into your blood stream

Types of Bones

Compact

  • Perforating (volkmann's) canals- holes that allow for passage of blood vessels

  • Concetric lamella: matrix in rings

  • lacunae (space), canaliculi- blood to every cell

  • Osteon'

  • Interstitial (matrix between osteons) and circumferential (matrix on the outside of the bone, smooth)

Spongy

  • Trabeculae: little shards/spikes of bone

  • lines of stress

Growth and Remodeling

Bone density- exercise increases bone density

Interstitial growth- occurs at the epiphyseal plate, growth in length

appositional growth- matrix is laid on outside, growth in width

Mechanical stress

  • pull of skelatal muscle (working out)

  • Gravity

Growth and remodeling

Bone loss for bedridden or cast: 1% of mass weekly

Facters that Affect bone remodeling

  • Minerals (Ca)

  • Vitamins (D)

  • Hormones

Exercise-both weight bearing and movement

Bone resorption

Function of the osteoclasts- results in demineralization

Women

  • Begins at age 30