Ch. 6 Skeletal System Flashcards
Describe the matrix of bone
- 2% bone cells (osteocytes) within lacunae
- 2/3rds calcium phosphate
- 1/3 collagen fibers
lacunae
the space occupied by either osteocytes or chondrocytes
canaliculi
- narrow pasageways through matrix for the exchange of nutrients, waste, and gases
- contain cytoplasmic extensions of osteocytes
what type of bone does not have a periosteum?
joints/articulated
hydroxyapatite
- crystals formed from the interaction fo calcium phosphate and calcium hydroxide
- incorporate other calcium salts as they form
- withstand compression, but not bending or sudden impacts
describe the composition of spongy bone
- collagen fibers form a framework for hydroxyapatite crystals to form.
- Crystals form small plates and rods locked into collagen fibers at regular angles
- Resulting protein-cystal combination has flexibility of collagen with compressive strength/shatter resistance
What are the 4 cells of bone?
- osteocytes
- osteoblasts
- osteoprogenitor cells
- osteoclasts
osteocytes
- Mature bone cells
- only in lacunae, between lamellae
- extend through canaliculi and link by gap junctions
- Do not divide
Functions:
- To maintain protein and mineral content of matrix
- To help repair damaged bone
lamellae
layers of matrix that separate osteocytes
ossification; osteogenesis
the production of new bone matrix by osteoblasts
osteoid
- the organix matrix secreted by osteocytes before calcium salts are deposited and becomes ‘bone’
- osteoblasts elevate local calcium concentrations above solubility, triggering deposition in the organic matrix
osteoblasts
- Make and release proteins and other organic components of matrix (osteoid)
- trigger calcium deposition to form bone
- develop into osteocytes when surrounded by bone matrix
osteoprogenitor cells
- Squamous (mesenchymal) stem cells
- differentiate into osteoblasts
- located in endosteum
- medullary cavities
- passageways of compact bone matrix
- assist in fracture repair
osteoclasts
– Secrete acids and protein-digesting enzymes
– Giant, multinucleate cells (50 or more!)
– Dissolve bone matrix and release stored minerals
(osteolysis)
– Derived from stem cells that produce macrophages
osteolysis (resorption)
acids and proteolytic enzymes secreted by osteoclasts dissolve the matrix and release stored minerals
What are the five functions of the skeletal system?
- Support
- Storage of minerals and lipids
- Blood cell production
- Protection
- Leverage
What is stored in bone?
- calcium
- phosphate ions
- yellow bone marrow (lipid energy reserves)
What are the 6 categories of bone shape?
- Sutural bones (Wormian bones)
- Irregular bones
- Short bones
- Flat bones
- Long bones
- Sesamoid bones
Sutural bones
(Wormian bones)
- Small
- Flat
- Irregular shape
Between the flat bones of the skull. Jigsaw puzzle.
Irregular bones
- Complex shape
- Short, flat, notched or ridged
Location: Spinal vertebrae, bones of pelvis, some skull bones
How are bones classified?
- Shape
- Internal tissue organization
- Bone markings
Short bones
small and boxy
Ex: carpal and tarsal bones
Flat bones
thin, parallel surfaces. Provide protection for underlying soft tissuse and extensive surface area for muscle attachment
Ex: roof of skull
sternum
ribs
scapulae
Long bones
Long and slender