Chapter 6: Skeletal System

Front 1

four components of the skeltetal system

Back 1

bones, carilage, tendons, and ligaments

Front 2

function of the skeletal system is to

Back 2

provide support and protection, allow body movements, store minerals and fats, and is site of blood cell production

Front 3

bones are good for support because

Back 3

they are rigid and strong allowing them to support major tissue in body

carilage - firm yet flexable support

ligaments - hold bones together

Front 4

ligaments

Back 4

strong bands of fiberous connective tissue. allow some movement between bones but prevent excessive movements

Front 5

bones are good for protection because

Back 5

hard thereby able to protect organs it surrounds

Front 6

bones are good for movements because

Back 6

contractions of skeletal muscle moves bondes

joints - allow movement

smooth cartilage covers ends of bones within some joints and helps allow movement

ligaments provide some movement but prevents excessive movements

Front 7

tendons

Back 7

strong bands of conective tissue

Front 8

joints

Back 8

formed where two or more bones come together and allow movement between the bones

Front 9

bones are good for storage because

Back 9

some minerals in the blood are taken to the bone and stored and then used when needed. mostly calcium and phosphorus. sometimes fats

Front 10

if needed fats are released from bone into the ___ and __.

Back 10

blood and used by other tissues as a source of energy.

Front 11

bones are good for blood cell production because

Back 11

many bones contain cavities filled with red bone marrow which gives rise to blood cells and platelets

Front 12

types of carilage

Back 12

hyaline cartilage, fibrocartilage, and elastic cartilage

Front 13

which type of carilage is most intimately associated with bone?

Back 13

hyaline cartilage

Front 14

most of the bones in the body develop from

Back 14

hyaline cartilage

Front 15

hyaline cartilage is also important to growth in bone because

Back 15

growth in length of bones and bone repair often involve the production of hyaline cartilage until it is then replaced with bone

Front 16

hyaline cartilage consistes of specialized cells that

Back 16

produce a matrix surrounding the cells

Front 17

cells that produce new cartilage matrix are called

Back 17

chondroblast

Front 18

when a matrix surrounds a chondroblast it becomes a

Back 18

chondrocyte

Front 19

a chondrocyte is

Back 19

a rounded cell that occupies a space called a lacuna within the matrix

Front 20

matrix contains __ which do ___ and ___ which do ___.

Back 20

collagen which provides strength and proteoglycans which make cartilage resilient by trapping water

Front 21

what is a perichondrum

Back 21

a double-layered connective tissue sheath covering most cartilage

Front 22

outer layer of the perichondrum is

Back 22

dense irregular connective tissue containing fibroblasts

Front 23

what do nutrients have to do to reach the chondrocytes and why

Back 23

blood vessels and nerves penetrate the outer layer of the perichondrium but do not enter the cartilage matrix so that nutrients must diffuse through the cartilage matrix to reach the chondrocytes

Front 24

the inner layer of the perichondrum differs from the outer layer in that...

Back 24

is more delicate and has fwer fibers and contains chondroblast

Front 25

articular cartilage

Back 25

is cartilage covering the ends of bones where they come together to form joints and has no perichondrium, blood vessels, or nerves.

Front 26

two ways in which cartlilage grows

Back 26

appositional growth and intersitial growth

Front 27

appositional growth

Back 27

chondroblasts in the perichondrium lay down new matrix and add new chondrocytes to outside of tissue

Front 28

interstitial growth

Back 28

chondrocytes within the tissue divide and add more matrix between the cells

Front 29

the composition of the bone matrix is responsible for

Back 29

the characterisitics of bone`

Front 30

bone cells produce the bone matrix become

Back 30

entrapped within it, break it down so that new matrix can replace the old matrix

Front 31

by weight mature bone matrix is normally what percent organic and inorganic?

Back 31

35% organic and 65% inorganic material

Front 32

organic material consists primarly of

Back 32

collagen and proteoglycans

Front 33

inorganic material consists primarily of

Back 33

calcium phosphate crystal called hydroxyapatite whos formula is Ca10(PO4)6(OH)2

Front 34

___ and ___ are responsible for the major functional characteristics of the bone

Back 34

collagen and mineral components

Front 35

bone matrix might be said to resemble

Back 35

reinforced concrete

Front 36

collagen might be said to resemble

Back 36

reinforcing steel bars, because it lends flexible strength to the matrix

Front 37

mineral components can be said to resemble

Back 37

concrete because it gives the matix compression (weight-bearing) strenght

Front 38

if all mineral is removed from a long bone..

Back 38

collagen becomes the primary consituent and bone becomes overly flexable

Front 39

if all the collagen is removed from a long bone...

Back 39

mineral becomes the main consituent and the bone becomes very brittle and is easily shattered

Front 40

bone cells are catergorized as...

Back 40

osteoblasts, osteocytes, and osteoclasts

Front 41

osteoblasts

Back 41

have extensive endoplasmic reticulum and numerous ribosomes

Front 42

osteoblast produce

Back 42

collagen and proteoglycans which are packaged into vesicles by Golgi apparatus and released from the cell by exocytosis

Front 43

osteoblasts release

Back 43

matrix vesicles

Front 44

matrix vesicles

Back 44

are membrane-bound sacs formed when the plasma membrane buds or protrudes outward and pinches off

Front 45

matrix vesicles concentrate

Back 45

Ca^2+ and PO4^3- and form needlelike hydroxyapatite crystals

Front 46

when hydroxyapatite crystals are released from the matrix vesicles

Back 46

they act as templates or "seeds" whuch stimulate further hydroxapatite formation and mineralization fo the materix

Front 47

ossification/ osteogenesis

Back 47

the formation of bone by osteoblasts

Front 48

ossification occurs by

Back 48

appositional growth on the surface of previously existing bone or cartilage

Front 49

elongated cell processed from osteoblast connect to

Back 49

cell procceses of other osteoblasts through gap junctions

Front 50

bone matrix produced by the osteoblasts cover the

Back 50

older bone surface and surrounds the osteoblast cell bodies and processes. the result is a new layer of bone.

Front 51

osteoctye

Back 51

an osteoblast that has become surrounded by bone matrix. it is now a mature bone cell

Front 52

osteocytes become relatively

Back 52

inactive compared with most osteoblast but they can produce the components needed to maintain the bone matrix

Front 53

lacunae

Back 53

the spaces occupied by the osteocyte cell bodies

Front 54

canliculi

Back 54

the spaces occupied by the osteoctye cell process

Front 55

cells and their proccessed form

Back 55

a "mold" around which the matrix is formed

Front 56

bones differ from cartilage in that

Back 56

the procceses of bone cells are in contact wih one another through canaliculi. instead of diffusing through the mineralized matrix nutrients and gases can pass through the small amount of fluid surrounding the celss in the canaliculi and lacunae or pass from cell to cell through the gap junctions connection the cell process

Front 57

osteoclasts

Back 57

large cells with several nuclei and are responsible for reorption

Front 58

reorption

Back 58

breakdown of bone

Front 59

ruffled border

Back 59

where the plasma membrane or osteoclasts contacts bone matrix and forms many projections

Front 60

osteoclasts also release

Back 60

enzymes that digest the protein components of the matrix

Front 61

through the process of endocytosis some of the breakdown products of bone resorption are

Back 61

taken into the osteoclast

Front 62

osteoclast break down bone best when

Back 62

they are in direct contact with mineralized bone matrix

Front 63

osteoblasts assist in the

Back 63

resorption fo bone by osteoclasts by production enzymes that break down the thin layer of unmineralized organic matrix normally covering bone.

Front 64

removeal of the thin layer of unmineralized organic matrix by osteoblast enables

Back 64

the obsteoclasts to come into contact with the mineralized bone

Front 65

connective tissue develops

Back 65

embryologically from mesenchymal cells

Front 66

some mesenchymal cells become

Back 66

stem cells

Front 67

stem cells can

Back 67

relicate and give rise to more specialized cell types

Front 68

osteochondral progenitor cells

Back 68

stem cells that can become osteoblast or chondroblast

Front 69

osteochondral progenitor cells are located

Back 69

in the inner layer of the perichondrium, the inner layer of the periosteum, and the endosteum

Front 70

osteoblasts are derived from

Back 70

osteochondral progenitor cells

Front 71

osteocytes are derived from

Back 71

osteoblasts

Front 72

osteoclast are derived from

Back 72

stem cells that give rise to a type of white blood cell called a monocyte

Front 73

multinucleated osteoclast probably results from

Back 73

the fusion of many stem cell descendants

Front 74

bone tissue is classified as either

Back 74

woven or lamellar bone according to the organization of collagen fibers within the bone matrix

Front 75

woven bone

Back 75

the collagen fibers are randomly oriented in many directions

Front 76

woven bone is first formed

Back 76

during fetal development or during the repair of a fracture

Front 77

remodeling

Back 77

the process of removing old bone and adding new bone

Front 78

woven bone is remodeled to form

Back 78

lamellar bone

Front 79

lamellar bone

Back 79

is mature bone that is organized into thin sheetw or layers called lamellae

Front 80

collagen fibers of one lamella lie __ to one another but ___ to the collagen fibers in the adjacent lamellae

Back 80

parallel

at an angle

Front 81

bones can also be classified according to

Back 81

the amount of bone matrix relative tot the amount of space present within the bone

Front 82

concellous bone

Back 82

consists of interconnecting rods or plates of bone called trabeculae

has less bone matrix and more space than compact bone

is sometimes called spongy bone

Front 83

between the trabeculae are spaces that

Back 83

are filled with bone marrow and blood vessels

Front 84

usually no blood vessels penetrate the trabeculae so

Back 84

osteocytes must obtain nutrients through their canaliculi

Front 85

trabeculae are located

Back 85

along the lines of stress within a bone

Front 86

compact bone

Back 86

is denser and has fewer spaces than cancellous bone

Front 87

in compact bone blood vessesls enter

Back 87

the substance of the none itself

Front 88

lamellae of compact bone are pimarily oriented

Back 88

blood vessels that run parrallel to the long axiz of the bone and are contained withine central or haversain canals

Front 89

in compact bone central cannals are lined with

Back 89

endosteum and contain blood vessels, nerves, and loose connective tissue

Front 90

concentric lamellae

Back 90

circular layers of bone latrix that surroung a common center, the central cannal

Front 91

osteon or haversain system

Back 91

a unit-- a singe central canal, its contents, and associated concentric lamellae and osteocytes--the bulls eye

Front 92

in compact bone, osteocytes are located

Back 92

in lacunae between the lamellar rings and canaliculi radiate between lacunaw accros the lamellae

Front 93

the outer surfaces of compact bone are formed by

Back 93

circumferential lamellae

Front 94

circumferential lamellae

Back 94

thin plates that extend around the bone

Front 95

in compact bone--in between osteons are

Back 95

intersitial lamellae

Front 96

intersitial lamellae

Back 96

remnants of concentric or circumferntial lamellae that were partially removed during bone remodeling

Front 97

in compact bone--osteocytes reviece nutrients and eliminate waste products through

Back 97

the canal system within compact bone

Front 98

blood vessels from the periosteum or medullary cavity enter the bone through

Back 98

perforating or Volkmann's cannals which run perpendicular to the lond axis of the bone

Front 99

perforating canals are not surrounded by concentric lamellae but

Back 99

can pass throught the concentric lamellae of osteons

Front 100

central canals recieve blood vesels from

Back 100

perforating canals

Front 101

individual bones are classified

Back 101

accorging to their shape as long, flat, or irregular

Front 102

long bones

Back 102

are longer than they are wide most of the bones of the upper and lower limbs are long bones

Front 103

short bones

Back 103

are about as broad as they are long they are nearly cube-shaped or round and are exemplified by the bones of the wrist and ankle

Front 104

flat bones

Back 104

have relativly thin, flattened shape and are usually curved. ex ribs, sternum and shoulder blades

Front 105

irregular bones

Back 105

have shapes that do not readily fit into the other three categories ex. vertebrae and facial bones

Front 106

diaphysis

Back 106

shaft of the long bone and is composed primarily of compact bone but can contain cancelous bone

Front 107

the end of the long bone is made mostly of

Back 107

cancellous bone with outer layer of compact bone

Front 108

withine joing, the end of the long bone is covered with hyaline cartilage called

Back 108

articular cartilage

Front 109

during bone formation and growth bones develop

Back 109

from centers of ossification

Front 110

primary center of ossification is in the

Back 110

diaphysis

Front 111

epiphysis

Back 111

a part of a long bone that develops from a center of ossification distinct from that of the diaphysis

Front 112

epiphyseal or growth plate

Back 112

seperates the epiphysis from the diaphysis

Front 113

growth in bone lenght occurs at

Back 113

the epiphyseal plate

Front 114

epiphyseal line

Back 114

when bone stops growing in lenght the epiphyseal plate becomes ossified and is called this

Front 115

the diaphysis of a long bone can have a large internal space called the

Back 115

medullary cavity

Front 116

cavities of cancellous bone and the medullary cavity are filled with

Back 116

marrow

Front 117

red marrow is

Back 117

the site of blood cell formation

Front 118

yellow marrow ia

Back 118

mostly adipose tissue

Front 119

in fetus spaces are mostly filled with __ marrow

Back 119

red marrow

Front 120

conversion of red marrow to yellow marrow begins

Back 120

just before birth and continues well into adulthood

Front 121

___ marrow completly replaces ___ marrow in the long bones of the limbs (ex. proximinal of arm and thigh bones)

Back 121

yellow replaces red

Front 122

which bone is used when donating red marrow?

Back 122

hip bone because it is a large bone with more marrow than smaller bones and accessed relatively easily

Front 123

periosteum

Back 123

a connective tissue membrane that covers the outer surface of a bone

Front 124

in a long bone, the outer fibrous layer is

Back 124

dense irregular collagenous connective tissue that contains blood vessels and nerves

Front 125

in a long bone, the inner layer is

Back 125

a single layer of bone cells which includes oseoblasts, osteoclasts, and osteochondral progenitor cells

Front 126

in long bones, where tendons and ligaments attach to bone

Back 126

the collagen fibers of the tendon or ligament become continuous with those of the perosteu

Front 127

perforating or Sharpey's fibers

Back 127

collagen fibers of the tendons or ligaments that penetrate the preriosteum into the outer part of the bone and they strengthen the attachment of the tendons or ligaments to the bone

Front 128

endosteum

Back 128

single layer of cells that lines the internal surfaces of all cavities within bones

Front 129

flat bones contain

Back 129

an interior framework of cancellous bone sandwiched between two layers of compact bone

Front 130

short and irregular bones have a compositions similar to the

Back 130

epiphysis of long bones

Front 131

which bones are not eglongated and have no diaphyses

Back 131

short and irregular

Front 132

which bones posses epiphyseal growth plates and therefore have small epiphyses

Back 132

some irregular

Front 133

sinuses

Back 133

air-filled spaces found is some in some of the flat and irregular bones of the skull which are lined by mucous membrane

Front 134

during fetal developemnt bone formation occurs in two patters..

Back 134

intramembranous and endochondral ossification

Front 135

intramembranous ossification takes place in

Back 135

connective tissue membranes

Front 136

endochondral ossification ossicifation takes place in

Back 136

cartilage

Front 137

both intramembranous and endochondral ossification initially produce

Back 137

woven bone which is then remodeled after remondeling

Front 138

at about the fifth week of development

Back 138

embryonic mesenchyme condenses around the developing brain to form a membrane of connective tissue with randomly oriented delicate collagen fibers

Front 139

intramembranous ossification of the membrane begins

Back 139

at about the eighth week of development and is completed by age 2

Front 140

centers of ossification

Back 140

locations in the membrane where ossification begins and they expand to form a bone by gradually ossifying the membrane

Front 141

fontanels

Back 141

the larger membrane-covered spaces between the developing skull bones that have not yet been ossified. are soft spots (bones eventually grow together and usually closed by 2 years old)

Front 142

intramembranous ossificationb begins when

Back 142

some of the mesenchymal celss in the membrane become osteochondral progenitor celss which specialise to become osteoblasts

Front 143

osteoblasts become osteocytes how?

Back 143

osteoblasts produce bone matirx that surroungs the collagen fibers of the connective tissue membrane and then the osteoblsts become osteocytes
(as a result many tiny tracevulae of woven hone develop)

Front 144

the formation of caritlage begins

Back 144

at approximately the end of the fourth week of development

Front 145

endochondral ossification of some cartilage might not begin

Back 145

until as late as age 18-20 years

Front 146

bones of the base of the skull, part of the mandible, the epiphyses of the clavivles and most of the remaining skeletal system develop

Back 146

through the process of endochondral ossification

Front 147

unlike cartilage bones cannont grow by

Back 147

interstitial growth

Front 148

bones increase in size only by

Back 148

appositional growth

Front 149

appositional growth

Back 149

the formation of new bone on the surface of older bone or cartilage

Front 150

long bones and bony projections increase in length because of

Back 150

growth at the epiphyseal plate

Front 151

in a long bone the epiphyseal plate separates

Back 151

the epiphysis from the diaphysis

Front 152

growth at the epiphyseal plate involves

Back 152

the formation of new cartilage by intersitial cartilage growth followed by apposistional bone growth on the surface of the cartilage

Front 153

what are teh 4 zones of the epiphyseal plate?

Back 153

1. zone of resting cartilage
2. zone of proliferation
3. zone of hypertrophy
4. zone of calification

Front 154

zone of resting cartilage

Back 154

nearest the epiphysis and contains randomly arranged chondrocytes that do not divide rapidly

Front 155

zone of perliferation

Back 155

the chondrocytes in this zone produce new cartilage though intersitial cartilage growth

Front 156

zone of hypertrophy

Back 156

the condrocytes produce in the zone of proliferation mature and enlarge. Thus a maturation gradient exists in each column: the cells nearer the epiphysis are younger and are actively proliferating whereas teh celss progressively nearer the diaphysis are older and are undergoing hypertrophy

Front 157

zone of calicification

Back 157

very thin and contains hypertrophied chondrocytes and calcified cartilage matrix. the hypertropheid condrocytes die and blood vessles contains osteoblasts from the endosteum. the osteoblasts line up on the surface of the calcified cartilage and through apposistional bone growth deposit new bone matrix which is later remodeled

Front 158

the process of cartilage calcification and ossification in the epiphyseal plate occurs by

Back 158

the same basic process as the calcification adn ossification of the cartilage model during endochondral bone formation

Front 159

the overall lenght of the diaphysis increases when

Back 159

new cartilage cells from in the zone of proliferation and as these celss enlarge in the zone of hyperthrophy

Front 160

why doesnt the thickness of the epiphyseal plate not increase

Back 160

because the rate of cartilage growth on the epiphyseal side of the plate is equal to the rate at which cartilage is replaced by none of the diaphyseal side of the plate

Front 161

as the bones achieve normal adult size, growth in bone length stopes because

Back 161

the epiphyseal plate is ossified and becomes the epiphyseal line (occures betweeen age 12 and 25)

Front 162

epiphyses increase in size because of

Back 162

growth at the articular cartilage

Front 163

bones that do not have an epiphysis, such as short bones, increase in size by

Back 163

growth at the epiphysis

Front 164

when epiphysis reach their full size the growth of ___ and its replaced by __ cease.

Back 164

cartilage

bone

Front 165

what type of bone doesnt stop growing?

Back 165

articular cartilage

it persists through life and doesn not become ossified like the epiphyseal plate

Front 166

when bone growth in width is rapid as in young bones or during puberty

Back 166

osteoblasts from the preiosteum lay down bone to form a series of ridges with grooves and one or more blood vessels of preiosteum lie within each groove

Front 167

when bone growth is slow

Back 167

the surface of the bone becomes smooth as osteoblast from the periosteum lay down even layers of bone to form circumferential lamellae

Front 168

potential shape and size of a bone and an idividual's final height are determined not only genetically but also by

Back 168

nutrition and hormmones

Front 169

any metabolic disorder that can affect the rate of cell proliferation or the production of collagen and other matrix can

Back 169

affect bone growth as does the avialibility of calcium or other minerals needed in the mireralization process

Front 170

arrested growth

Back 170

transverse regions of greater bone denisty crossing an otherwise normal bone

Front 171

vitamin D is nessisary in bone growth because

Back 171

it is nessiary for normal absorption of calcium from the intestines

Front 172

insufficient vitamin D in children causes

Back 172

rickets -- a disease resulting from reduced mineralization of the bone matrix

Front 173

osteomalacia

Back 173

a softening of bones as a result of calcium depletion

Front 174

____ is necessary for collagen synthesis by osteoblast

Back 174

vitamin C

Front 175

vitamin C deficancy results in

Back 175

bones and cartilage that are deficient in collagen because collagen synthesis is impaired and can result in scurvy

Front 176

scurvy

Back 176

marked by ulceration and hemorrhage in almost any area of the body because of a lack of normal collagen sythesis in connective tissues

Front 177

growth hormone

Back 177

from anterior pituitary increases general tissue growth including overall bone growth by stimulating intersitial cartilage growth and apposistional bone growth

Front 178

thyroid hormone

Back 178

required for normal growth of all tissues including cartilage--decrease in hormone can result in decrease in size of individual

Front 179

sex hormone

Back 179

can influence bone growth. decreased levels of testosterone or estrogen can prolong the growth pase of the epiphyseal plates

Front 180

bone remodeling converts ____ into ____

Back 180

woven bone

lamellar bone

Front 181

bone has a mechanical advantage as a ____ rather than a ____

Back 181

cylinder

rod

Front 182

the relative thickness of compact bone is maintained by

Back 182

the removal of bone on the inside by osteoclasts and the addition of bone to the out side by osteoblast

Front 183

basic multicellular unit (BMU)

Back 183

is a temporarry assembly of osteoclast and osteoblasts that travel through or across he surface of bone

Front 184

average life span of a BMU

Back 184

6 months

Front 185

BMU activity renews the entire skeleton

Back 185

every 10 years

Front 186

intersitial lamellae are

Back 186

remnants of osteons that were not completely removed when a BMU formed a tunnel