chap 7 bone tissue

skeletal system

its the sturdy internal frame composed of bone, cartilage, and ligaments

Support of weight of the body with limb bones and vertebrae; teeth are supported by jaw

Function of skeleton

pRotection of delicate tissues like brain, spinal cord, heart, lungs, and more

fUnction of skeleton 

moVement limb movements, breathing, abdominal other movements depend on bone

fuNction of skeleton 

eleCtrolyte balance its a reservoir for calcium and phosphate levels

funCtion of skeleton

acid-Base balance buffers blood against large pH charges

funcTion of skeleton

blood Formation, red bone marrow is the chief producer of blood cells 

functIon of skeleton

bone can =

osseous tissue

bone can also =

an organ that consists of osseous tissue, blood, cartilage, adipose and, nerve tissue, and connective tissue

flat bones

thin, curved plates

flat bones function 

protect soft organs 

long bones

loger than wide, rigid levers acted upon by muscles

long bones function

crucial for movement

short bone

approximately equal in length and width, glide across one another in multiple directions

short bone ex

wrist and ankle

irregular bone

elaborate shapes that do not fit into other categories

Compact bone

dense outer shell of bone that encloses marrow cavity

marrow cavity (medullary cavity)

space that contains bone marrow

at end of long bone the central space is occupied by

spongy (cancellous) bone

nutrient foramina 

minute holes in bone surface that allows blood vessels to penetrate 

periosteum

external sheath covering bone, consisting of outer fibrous layer of collagen and inner osteogenic cells

endosteum

thin layer of reticular connective tissue lining marrow cavity

endosteum contains

osteogenic cells

osteogenic cells

stem cells that give rise to other bone cells

diaphysis 

shaft of long bone

diaphysis function

provide leverage

epiphysis

enlarged end of long bone

epiphysis function

stregthen joint and anchors ligaments and tendons

articular cartilage

layer of hyaline cartilage that covers joint surface

what does the articular cartilage allow the joint to do 

move more freely 

epiphyseal plate (growth plate)

area of hyaline cartilage that separates epiphyses and diaphysis of childern’s growth

epiphyseal line

in adults, a bony scar that makes where growth plate used to be

bone tissue is ___ and consists of

connective; cells, fibers, and ground substance

how many types of bone cells

4

osteogenic cells

stem cells that will become osteoblasts

osteoblasts

bone forming cells that synthesize hard bone matrix 

osteocytes

former osteoblasts that can reabsorb/deposit bone

osetoclasts

bone dissolving cells on bone surface formed by fusion of stem cells

bone matrix

the ground substance of osseous tissue

what is bone matrix

hard, dense substance we think of when we think of bone

what is bone matrix composed of

organic, and inorganic matter

organic matter (1/3)

collagen, carbohydrates, protein complexes, and glycoproteins

organic matter gives bone

degree of flexibility, without it becomes brittle

inorganic matter (2/3)

85% hydroxyapatite, 10% calcium carbonate and other minerals

inorganic matter gives bone 

strength and rigidity, without it becomes soft 

osteon

one central canal surrounded by lamellae (onion like)

concentric lamellae surround a ___ and run longitudinally

central (Haversian) canal

perforating (volkman) canal

diagonal ducts that join central canals or nutrient foramina

collagen fibers lined in

helical arrangements like threads of a screw, corkscrewing in one direction in one lamella and opposite in the other

lacunae 

cavities where osteocytes reside situated between adjacent lamella 

canaliculi

tiny ducts that connect lacunae to one another

osteocytes communicate

transmitting nutrients, and gases, through gap junctions

spongy bone consists of

lattice of delicate silvers (spicules) and trabeculae

spicules

discontinuous slivers of bone

trabeculae

thin plates of beams

spaces between bone are filled with

red bone marrow

trabeculae develop along

bone’s lines of mechanical stress, impairing strength to bone without adding a lot of weight

what is bone marrow

soft tissue occupying marrow cavities of long bones and small spaces of spongy bone

red marrow contains

hematopoietic tissues (produces blood cells)

red marrow found 

nearly in every bone in a child

red marrow found where in adults

skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur

in adults most red marrow in extremities is replaces by

fatty yellow marrow

fatty yellow marrow doesn’t

produce blood cells, basically adipose tissue

two methods of brain formation

intramembranous and endochondral

intremembranous

forms flat bones of skull and clavicle

endochondral

forms most other bones

endochondral ossification begins when

at week 6 of fetal development in a series of steps

1st and 2nd step in endochondral ossification

beginning with a body of hyaline cartilage

where is the 1st and 2nd step of endochondral ossification located

primary ossification center

what is the 1st and 2nd step of endochondral ossification surrounded by

bony collar deposited by osteoblasts

step 3 in endochondral ossification

blood vessel s bring osteoclasts that digest calcified tissue

what does step 3 of endochondral ossification form

primary marrow cavity 

in step 3 of endochondral ossification, osteoblasts work

to thicken the epiphyseal chondrocytes to inflate/die then calcify

after the osteoblasts thicken the epiphyseal chondrocytes to inflate/die, then calcify they create a

secondary ossification center

metaphysis forms 

a region of transition from cartilage to bone and forms at the each end of long bone

secondary marrow cavity forms with

metaphysis

through childhood, epiphyses fill with

spongy bone

throughout childhood cartilage remains

to cover ends of the bones and at the epiphyseal plate

by early 20’s. the epiphyseal plate

converts to bone, ceasing growth

where do bones grow

epiphyseal plate 

the epiphyseal plate is surrounded by

a transition plate the metaphysis, where cartilage is replaced by bone

how do bones grow

chondrocytes facing marrow cavity stop multiplying, minerals are deposited, calcifying the cartilage. then osteoclasts dissolve calcified cartilage while osteoblasts deposit bone, adding to bone length, as the plates at each bone end move further apart

what controls bone lengthening 

two hormones - growth, sex 

continual bone growth in diameter and thickness =

appositional growth

how does appositional growth happen

thin layer of osteoblasts at inner surface of periosteum deposit osteoid tissue that calcifies

while appositional growth happens osteoclasts of endosteum

enlarge marrow cavity by resorption

osteoblasts lay down matrix in layers parallel to surface forming

circumferential lamellae

once bone is formed

mature bone undergoes constant remodeling

remodeling repairs

micro fractures

remodeling releases/absorbs

minerals from bloodstream

remodeling changes

the shape, size, and/or strength of bone, including to develop bony features

remodeling reshapes

bone as determined by mechanical stresses places upon it and bone adapts to withstand its stressors

Wolffs law of bone 

bone is shaped by the functional experience

remodeling depends on

collaborative action of osteoblast and osteoclast activity

remodeling can go out of

whack when bone deposition rate does not = reabsorption rate

ex of remodeling going out of whack

osteoporosis occurs when prolonged osteoclast activity

extent of remodeling depends on

nutritional status, weight, work/exercise, habits, and medical history

a mature bone remains

a metabolically active organ

a metabolically active organ is involved in

its own maintenance of growth and remodeling

a metabolically active organ exerts a

profound influence over the rest of the body by exchanging minerals with tissue fluid