Bones and Ligaments

Question 1

Bones

Answer 1

Specialized for supporting wt
Dynamic, constant reorg
Highly vasc/innervated CT
major mineral storage area (Ca++)

Question 2

Bone comp

Answer 2

67% inorganic (Ca++)

33% organic (mostly collagen)

Question 3

Cortex/Medullary bone

Answer 3

Cortex- outer, compact

Medullary- inner, spongy

Dense outer cortical bone, w irregular medullary space

Question 4

Periosteum

Answer 4

CT that contains cells that maintain/change/repair external cortical surface
Also BV, nerves, fibrous tissue contiguous w tendons/ligs/JC

Adherent to cortical surface by Sharpey’s fibers (P to cortical bone)

Question 5

Periosteum parts

Answer 5

Outer (fibrous)- fibroblasts/cytes

Inner (osteogenic)- osteognic cells such as osteoblasts

Question 6

Osteogenic cells (aka BLC/endosteum)

OB

OC

Osteoclasts

Answer 6

Cells that could become osteoblasts to form bone, also line medullary spaces/Haversian space

rise from BLC in vascular sites (can become chondroblasts if avascualr), deposit osteoid

Trapped w/in osteoid that mineralizes, mature, cannot divide/secrete matri

multinucleated, fusion of monocytes, bone remodeling- break down lots of mineralized bone

Question 7

OB

Answer 7

Immature, secrete osteoid (matrix) mostly made of T1 collagen to provide strength, as well as chondroitin sulfate (ground substance)
Control mineralization of matrix
Non-dividing, form synctium

Question 8

OB produces

Inactive OB

Answer 8

T1 Collagen and Proteoglycans, RANKL, osteocalcin (bone mineralization), osteopontin (sealing zone), bone sialoprotein (binding of OB to ex matrix

becomes BLC, cover bone

Question 9

OB shape

Answer 9

Cuboidal, but become columnar when secreting osteoid

Inactive- flattened, cover non-remodeling surfaces of compact/spongy bone

Question 10

OB progeny

Trapped OB

Answer 10

two OB specific genes control differentiation
Also control expression of osteocalcin (secretory protein in term osteocytes)

Osteocyte

Question 11

Osteocyte

Answer 11

found in lacuna

project canaliculi to touch adjacent bony canals

Question 12

Osteoclasts fn

Answer 12

fused monocytes

resorb bone in Howship’s lacuna (subosteoclastic compartment)

Question 13

Osteoclast surface

SZ

Answer 13

Smooth (outer, inactive)
Ruffled (inner, secrete enzymes)
Hydrolytic enzymes digest matrix but leave behin collagen

compartmentalizes working area from surrounding bone- actin filaments connected to osteopontin

Question 14

Osteoid vs bone

Answer 14

bone has Ca++

Question 15

Osteoblasts regulate osteoclasts

Answer 15

Monocytes w MCSF on surface
Become macro, express RANK and binds to OB w RANKL, osteoclastogenesis
Becomes multinucleated Oclast, leaves OB and is mature

Question 16

Calcium and Hormones

Answer 16

Calcitonin- released by parafollicular cells of thyroid helps to dec blood Ca level
Inhibits rate at which Ca leaves bone tissue

PTH- secreted by principal cells of PT gland, inc blood Ca by causing bone to release Ca, acts on kidneys to retain Ca and intestine to absorb Ca

Question 17

Osteocytes communicate

Answer 17

via gap junctions

Bathed in bone fluid in lacuna/canaliculi
Forms a separate compartment to control plasma Ca levels

Question 18

Bone fluid and Canaliculi

Answer 18

Ca enters BF through channels
PTH inc Ca into BLC and toward ECF

Gap junctions allows passage of ions

Question 19

Spongy bone

Answer 19

Spicules (spines) and trabeculae (shelves)

constantly remodeled

Question 20

Compact bone, Osteon, VC

Answer 20

Lined w endosteum
Osteon- circular arrangement
center= BV, (haversian canal), LV, nerve

Linking parallel HC= VC

Question 21

Sharpey’s fibers

Answer 21

bundles of collagen fibers from periosteum tat become inserted into matrix of lamellae
adheres periosteum to the bone

Question 22

Ligaments

Answer 22

Few cells (inactive fibroblasts)
Low ground substance to cell ratio
Avascular
Thick collagen in parallel, resists tension in 1 direction

Question 23

Ligaments/Tendons

Answer 23

Use collagen to insert into epi/perineurium of muscle or periosteum of bone

allows for tight adherence