Chapter 8 - Bone

Question 1

Functions of bone

Answer 1

• support
• protection
• movement
• storage of Ca2+ and PO4 2-
• hematopoiesis

Question 2

General characteristics of bone

Answer 2

• vascularized
• innervated
• contains cells
• matrix contains organic and inorganic components
• covered by periosteum
• endosteum lines marrow cavities

Question 3

What are the 3 cells in bone?

Answer 3

osteoblasts, osteocytes, osteoclasts

Question 4

OsteoBLASTS

Answer 4

• 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

Question 5

OsteoCYTES

Answer 5

• mature osteoblasts
• nonmitotic
• reside in lacunae
• much less active in synthesizing matrix than osteoblasts
• have long cellular processes that contact other osteocytes

Question 6

OsteoCLASTS

Answer 6

• 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

Question 7

Matrix

Answer 7

• 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

Question 8

Compact bone/Secondary/Mature/Lamellar

Answer 8

• 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

Question 9

Trabecular bone/Spongy/Cancellous/Primary/Woven

Answer 9

• 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

Question 10

What does PTH do?

Answer 10

• stimulates osteoblasts to secrete osteoclasts-stimulating factor
• blood calcium increases
• osteocalsts-stimulating factor increases osteoclast activity, so Ca2+ is released

Question 11

What does Calcitonin do?

Answer 11

• decreases levels of calcium
• directly inhibits osteoclasts

Question 12

What hormones stimulate bone formation and closure of epiphyseal plates?

Answer 12

estrogens and androgens