Bone tissue

functions of skeleton

support, protection, movement, storage, and blood formation

bone shapes

flat, long, short, sesmoid, and irregular

flat bones

thin, curved protective plates (sternum)

long bones

levers in the limbs that produce major movements (femur)

short bones

glide across one another in multiple directions (carpels)

sesamoid bones

short bones embedded in tendons that decrease physical stress (patella)

irregular bones

odd shapes (ossicles or vertebra)

layers of long bones

periosteum and compact bone

periosteum of long bones

outer fibrous layer
inner osteogenic layer

outer fibrous layer

collagen fibers
-continuous with tendon
-perforating fibers

perforating fibers

attach periosteum to bone

compact bone of long bones

outer hard bone

spongy bone of long bones

porous bone at ends

marrow cavity

hollow area in middle where bone marrow lives

inner osteogenic layer

bone stem cells on outside of bone

endosteum

inner layer of stem cells

diaphysos

shaft/lever

epiphysis

enlarged ends covered on articular cartilage

epiphysial plate

growth plate

epiphysial line

fused growth plate (mature bone)

nutrient foramina

holes for blood vessels

flat bones layers

periosteum and compact bone

compact bone location of flat bones

outer and inner surfaces

spongy bone location in flat bones

throughout the entire middle (no marrow cavity)

how are flat bones connected

fibrous joints that limit movement

osteogenic cells

stem cells in endosteum and periosteum that form osteoblasts

osteoblasts

synthesize (build) organic matter and promote osteogenesis
-may develope into osteoclast

osteocytes

cells trapped in lacunae
-eat through bone to form gap junctions between them

osteocytes function

maintain bone density
regulate Ca/P concentrations
strain sensors

osteoclasts

osteolysis (dissolve bone)

bone remodeling steps

osteocytes detect load
osteoclasts dissolve old bone
osteoblasts create new bone

organic matter of bone matrix components

collagen, glycoaminoglycans, proteoglycans, and glycoproteins (protein carb mixture)

organic matter of bone matrix function

resists tension
sticky landing site for inorganic matter (bendy)

inorganic matter of bone matrix composition

85% HYDROOXYAPATITE

inorganic matter of bone matrix function

resist compression (tough)

osteon

structural unit

osteon components

central canal, lamallae

central canal

hole fore nerves and blood vessels

what connects the central canals

perforating canals

How do the nutrients/waste get to the rest of the cells of the osteon

diffusion through gap junctions

lamellae

concentric layers of matrix and helical collagen fibrils

What connects the lamellae

canaliculi

what separated lamellae

cement lines

circumferential lamellae

layer of osteocytes that wrap around the outside of all the osteons

interstitial lamellae

osteocytes filling in the gaps between lamellae

spicules

rods/spines of spongy bones

trabeculae

plates/beams of spongy bones

spongy bone function

provides strength while minimizing weight

red bone marrow

hematopoietic tissue

yellow marrow

stores fat

What is the make up of marrow in children

all red

What is the make up of marrow in adults

red in cranium, vertebrae, ribs, sturnum, pelvic girdle, and prox head of femur/humerus
rest yellow

what type of bone is produced from intramembranous ossification

flat bones

stages of intramembranous ossification include

osteoid deposition, calcification, periosteum and spongy bone, compact bone

osteoid deposition

mesenchymal cells line blood vessels and create osteoblasts and osteoid tissue away from blood vessel

calcification

inorganic crystals form on osteoid tissue pushing blood vessels into narrower spaces and trapping osteoblasts

WHat forms the periosteum

adjacent mesenchyme

what forms compact bone

periosteal osteoblasts

steps of endochondral ossification

early cartilage model, primary ossification, diaphysis ossification, epiphysis ossification, spongy bone, cavities merge

early cartilage model

step 1 of endochondral ossification
-mesenchyme forms hyaline cartilage
-perichondrium makes chondrocytes

primary ossification

step 2 of endochondral ossification
-chondrocytes inflate and then die leaving a thin calcified wall and central cavity
-perichondrium forms periosteum which makes osteoblasts

diaphysis ossification

step 3 of endochondral ossification
-osteoclasts remove calcified cartilage shell to create primary marrow cavity
-osteoblasts deposit bone around the cavity

metaphysis

region where cartilage turns to bone (where the action happens/part of plate)

epiphysis ossification

secondary marrow cavity is formed by osteoclast and osteoblast activity

bone elongation occurs through what process

interstitial growth

interstitial growth

-chondrocytes multiply and deposit new matrix
-osteoclasts/blasts remodel

bone widening occurs through what process

appositional growth

appositional growth

-osteoblasts deposit osteoid tissue
-calcification traps blasts
-turns into osteocyte and forms communication tunnels

Wolff's law of bone

bone architecture is determined by mechanical stresses (use)

what percentage of bone is replaced per year

10

Why does bone remodeling occur

mineral release, reshaping/repairing bones, maintenance

mineralization

blood minerals are deposited in bone as hydroxyapatite

mineralization process

-osteoblasts create collagen fibers
-hydroxyapatite seed crystals form on collagen and grow until calcified

ectopic ossification

seed crystals form in soft tissues (arteries)

mineral resorption

hydroxyapatite is dissolved to release minerals

mineral resorption process

-osteoclasts surface Ca receptors bind
-proton pumps acidify the region
-hydroxyapatite dissociates

At what pH will hydroxyapatite dissociate

below 4

Ca homeostasis level

9.2-10.4 mg/dL

what happens with hypocalcemia

muscle spasms

what happens with hypercalcemia

muscle weakness

calcitriol role

increase blood Ca

calcitonin role

decrease blood Ca

parathyroid role

increase blood Ca

Vit D synthesis

Vit D to liver > calcidiol to kidney > calcitriol to needed areas

phosphate homeostasis

not tightly regulated

what increases absorption phosphate levels

calcitriol

what promotes excretion of phosphate

parathyroid hormone

stress fracture

fracture caused by trama

pathological fracture

fracture caused by disease

open fracture

open wound in skin

closed fracture

skin remains intact

nondisplaced fracture

maintain alignment

displaced fracture

1+ pieces shifted

comminuted fracture

broken into 3+ pieces

greenstick fracture

incomplete break

steps of fracture healing

cell invasion (granulation tissue), soft callus, hard callus, remodeling

closed reduction

manipulated a fracture into place without surgery

open reduction

surgical realignment of fracture

osteoporosis

spongy bone loses matrix and becomes brittle