Chapter 8 - Bone Flashcards
1
Q
Functions of bone
A
- support
- protection
- movement
- storage of Ca2+ and PO4 2-
- hematopoiesis
2
Q
General characteristics of bone
A
- vascularized
- innervated
- contains cells
- matrix contains organic and inorganic components
- covered by periosteum
- endosteum lines marrow cavities
3
Q
What are the 3 cells in bone?
A
osteoblasts, osteocytes, osteoclasts
4
Q
OsteoBLASTS
A
- secrete organic components of bone matrix
- abundant RER
- does not make bones hard, mineralization occurs later
- cuboidal, but become flat/spindle-shaped as becomes more quiescent
5
Q
OsteoCYTES
A
- mature osteoblasts
- nonmitotic
- reside in lacunae
- much less active in synthesizing matrix than osteoblasts
- have long cellular processes that contact other osteocytes
6
Q
OsteoCLASTS
A
- resorb bone matrix - contain many lysosomes
- only in spongy bone
- ver large cells - multinucleated and contain microvilli
- H+ pump in osteoclasts membrane acidifies matrix in the area of resorption
- bone resorption under hormonal control
- ruffled border and obvious clearing of bone matrix
- derived from macrophages
7
Q
Matrix
A
- organic components are secreted by osteoblasts (collagen type 1 and glycoproteins)
- calcification occurs after organic components are released
- 50% dry weight of bones
- 99% of the body’s Ca2+ is in bone
8
Q
Compact bone/Secondary/Mature/Lamellar
A
- cortical region of long bone
- extremely strong/dense
- structural unit is the osteon
- regular, ring like arrays of matrix w/ osteocytes
- osteocytes are in lacunae
- cellular processes of osteocytes lie in canaliculi
- each osteon has a central canal (Haversian canal) containing blood vessels
- osteons oriented to the bones long axis
9
Q
Trabecular bone/Spongy/Cancellous/Primary/Woven
A
- random weave of coarse collagen fibers
- lines marrow cavities
- found at epiphyses of long bones
- first type of bone to develop (later remodeled into compact bone)
- first type laid down at a fracture site
- osteocytes and osteoblasts present
- irregular pattern of collagen fiber deposition produces a meshwork of rods or plates of bone
- can sometimes see osteoclasts
10
Q
What does PTH do?
A
- stimulates osteoblasts to secrete osteoclasts-stimulating factor
- blood calcium increases
- osteocalsts-stimulating factor increases osteoclast activity, so Ca2+ is released
11
Q
What does Calcitonin do?
A
- decreases levels of calcium
- directly inhibits osteoclasts
12
Q
What hormones stimulate bone formation and closure of epiphyseal plates?
A
estrogens and androgens
