CHAPTER 7 (BONES)

what are living skeleton made of?

• dynamic tissues

• full of cells

• permeated with nerves

• blood vessels

osteology

the study of bone

what does the skeleton continue to do?

remodels itself and interacts with other organ system of the body

skeletal system is composed of what 3 things?

• bones

• cartilages

• ligament

orerunner of most bones; covers many joint surface of mature bone; lubricate to move easily

cartilage

ligaments

hold bones together at joints (bone to bone)

tendons

attach muscle to bone

what are the 6 functions of the skeleton?

• support

• protection

• movement

• electrolyte balance

• acid-base balance

• blood formation

support

limb bones and vertebrae support body; jaw bones support teeth; some bones support viscera

protection

• brain

• spinal cord

• heart

• lungs

movement

limb movements, breathing and other movement depend on bone

electrolyte balance

calcium & phosphate levels

acid-base balance

buffers blood against large pH changes by altering phosphate & carbonate salt levels (prevents drastic pH shift by neutralizing excess acids or bases)

blood formation

red bone marrow is the chief producer of blood cells

connective tissue with the matrix hardened by calcium phosphate & other minerals

bone (osseous tissue)

mineralization or calcification

the hardening process of bone

what do individual bones (organs) consist of?

• bone tissue

• bone marrow

• cartilage

• adipose tissue

• nervous tissue

• fibrous connective tissue

How many types of bones are there & what are they?

4

• flat bones

• long bones

• short bones

• irregular bones

flat bones

thin, curved plates; protects soft organs

long bones

longer than wide; rigid levers acted upon by muscles; crucial for movement

short bones

approximately equal in length & width; glide across one another in multiple directions (wrist & ankle)

irregular bones

elaborate shapes that do not fit into other categories (vertebrae)

compact (dense or cortical) bone

dense outer shell of bone

spongy (cancellous) bone

loosely organized bone tissue; covered by more durable compact bone

where is the spongy bone found in?

the center of ends & center of shafts of long bones & in middle of nearly all others

what fraction of the bone is compact & spongy bone by weight?

compact (3/4)

spongy (1/4)

what are the features of long bone?

• diaphysis

• epiphyses

diaphysis

middle shaft that provides leverage; has the marrow cavity (medullary cavity)

medullary cavity

space in the diaphysis of a long bone that contains bone marrow

epiphyses

enlarged ends of a long bonel; strengethen joint & anchor ligaments & tendons

layer of hyaline cartilage that covers joint surface; allows joint to move more freely

articular cartilage

minute holes in bone surface that allows blood vessels to penetrate

nutrient foramina

external sheath covering most of bone

periosteum

perforating fibers

penetrate into bone matrix

inner osteogenic layer of bone-forming cells

important to bone growth & healing of fractures

thin layer of reticular connective tissue lining marrow cavity; has cells that dissolve osseous tissue & others that deposit it

endosteum

flat bones

sandwhich like construction

what are the layers of the flat bone

2 layers of compact bone (inner & outer tables) enclosing a middle layer of spongy bone; both surfaces covered with periosteum

diploe

spongy middle layer; absorbs shock; marrow spaces lined with endosteum

bone is a connective tissue that consists of wut?

• cells

• fibers

• ground substance

what are the 4 principal types of bone cells

• osteogenic cells (stem cells)

• osteoblasts (forms bone matrix)

• osteocytes (maintains bone tissue)

• osteoclasts (resorbs bone)

osteogenic cells

stem cells found in endosteum & inner layer of periosteum

what do osteogenic cells arise from?

from embryonic mesenchyme; multiply continuosly & give rise to most other bone cell types

osteoblasts

bone-forming cells; reinforce bone

what do osetoblasts form?

single layer of cells under endosteum & periosteum

what does osteoblasts synthesizes?

soft organic matter of matrix which then hardens by mineral deposition (osteogenesis)

what does osteoblasts secrete?

hormone osteocalcin - (stimulates insulin secretion of pancreas; increases insulin sensitivity in adipocytes which limits the growth of adipose tissue

osteocytes

former osteoblasts that have become trapped in the matrix they deposited

lacunae

tiny cavities where osteocytes reside

canaliculi

little channels that connect lacunae

cytoplasmic processes of osteocytes reach into what?

canaliculi & contact processes of neighboring cells

what doe gap junctions allow?

for passage of nutrients, wastes, signals

what do some osteocytes do?

reabsorb bone matrix while others deposit it

what do osteocytes act as?

strain sensors —- when stressed, produce biochemcial signals that regulate bone remodeling (shape & density changes that are adaptive)

osteoclasts

bone dissolving cells found on bone surface

osteoclasts develop from wut?

same bone marrow stem cells that give rise to blood cells (diff origin from other bone cells)

what shape do osteoclasts form?

very large cells formed from fusion of several stem cells & have multiple nuclei in each cell

what type of border does osteoclasts have?

ruffled border (large surface area) facing bone

where do cells often reside in?

resorption bays (pits in bone surface)

osteolysis?

dissolving bone is part of bone remodeling

what is osteoporosis?

• weakens bone, making them more prone to fractures

• body loses too much bone

• makes too little bone

• decreased density & strength

rates of osteoporosis are higher in wut area?

sooty (black) highly polluted air

exposure to PM (particulate matter) less than wut can cause wut?

less than 2.5 microns & black carbon, associated with high rates of bone fracture

ground level ozone can block wut?

sunlight, decreasing vitamin D production

what are the effects of air pollution on bone?

• spur formation of free radicals

• promote inflammation & other immune responses all of which interfere with the process of replacing older tissue with newer ones

matrix of osseous tissue averages by wut?

dry weight

what fraction are organic & inorganic?

1/3 organic

2/3 inorganic

organic matter

synthesized by osteoblasts

organic matter is wut?

collagen, carbohydrate-protein complexes such as

• glycosaminoglycans

• proteoglycans

• glycoproteins

inorganic matter is what?

• 85% hydroxyapatite (crystallized calcium phosphate salt)

• 10% calcium carbonate

• other mineral (fluoride, sodium, potassium, magnesium)

bone is a composite material—- a combination of wut?

of ceramic & polymer

hydroxyapatite and other minerals are wut?

ceramic

collagen (protein) is wut?

polymer

ceramic portions allows the bones to do what?

support body weight without sagging

what is rickets?

disease caused by mineral deficiency & resulting in soft, deformed bones

polymer (protein) gives wut?

flexibility

osteogenesis imperfecta (brittle bone disease) results from wut?

a defect in collagen deposition

what is the other name for compact bone?

haversian system

concentric lamellae surround wut?

a central (haversian) canal running longitudinally

perforatiing canals

transverse or diagonal passages

circumferential lamellae fill wut?

outer region of dense bone

interstitial lamellae fill wut?

irregular regions btw osteons

what do spongy bone consists of?

lattice of bone covered with endosteum

what are the silver of bones called

spicules

what are thin plates or beams of bone called

trabeculae

what type of bone marrow are in spongy bone?

red bone marrow

what do spongy bone have less of?

few osteons and no central canals; all osteocytes close to bone marrow

what does spongy bone provide?

strength with minimal weight

trabeculae develop along wut?

bones' lines of stress