Bio Chapter 6 Skeletal system
interstitial lamellae
between the osteons are remnants of concentric or circumferential lamellae that were partially removed during bone remodeling
Volkmann canals
blood vessels from the periosteum or medullary cavity enter the bone through this canal -runs perpendicular to the length of the bone "perforating canals" -NOT surrounded by concentric lamellae->pass through the concentric lamellae of osteons -nutrients enter haversain's canal, pass into the canaliculi, and move peripheral cells at the edge of each osteon -waste products are removed in the reverse
rheumatoid arthritis
autoimmune, attacks small joints (fingers) bilateral effect
medullary cavity
large hollow cavity within diaphysis
zone of calcification
number four in the picture -closest to diaphysis side -very thin and contains hypertophied chodrocytes and calcified cartilage matrix -hypertrophied chondrocytes die, blood vessels from the diaphysis grow into the area
zone of resting cartilage
number one in the picture -closest to epiphyseal side -contains slowly dividing chondrocytes
lacuna
space within the matrix
lacunae
spaces occupied without matrix but occupied by the osteocyte cell bodies
haversian canals
"central canal" -lined with endosteum and contain blood vessels, nerves, and loose CT -receive blood vessels from Volkman canals
osteocyte
"once an osteoblast has secreted enough bone matrix to become surrounded by it the cell -retain connections via cell extensions -mature bone cells -stellate -lacunae and canaliculi -nutrients diffuse through tiny amount of liquid surrounding cell and filling lacumae and canaliculi ->transfers from one cell to the next via gap junction LOCATED: in lacunae between the lamellar rings, and canaliculi radiate between lacunae across the lamellae
cartilage
(hyaline, fibrocartilage and elastic) CONSISTS: -specialized cells that produce matrix (chonddroblasts and chondrocytes) -perichondrium that covers the cartilage at articulations -articular -covers bones at joints GROWTH: appositional interstitial
bone repair
-Hematoma formation. localized mass of blood released from blood vessels but confined within an organ or space, clot formation -callus formation: callus internal:blood vessels grow into a clot in hematoma external: collar around opposing ends. periosteal osteochondral progenitor cells
tendons
-band or cord of dense CT that connects muscle to a bone or another structure "strong bands of CT contain: bundles of collagen fibers, few nerve/blood vessels
osteoblasts
-bone forming cells CONSISTS: -extensive ER and numerous ribosomes FUNCTION: -produce collagen and proteoglycans (packed into vesicles by Golgi and released via exocytosis) -release matrix vesicles -form new bone via ossification
effects of aging on skeletal system
-bone matrix decreases-> more brittle due to lack of collagen; but also less hydroxyapatite -bone mass decreases (men denser due to testosterone and greater weight)(african and hsipanics have higher bone masses that caucasians and asians) -increased bone fractures -bone loss causes deformity, loss of height, pain, stiffness --stooped posture --loss of teeth
lamellar bone
-mature bone in sheets called lamellae -fiber are oriented in one direction in each layer, but in different directions in different layers for strength
factors that affect bone growth
-nutrition -vitamin D - important for Ca absorption -vitamin C - important for collagen synthesis -hormones - GH, T3/T4, sec hormones
remodeling
-removing old bone and adding new -woven bone is remodeled into lamellar bone
calcium homeostasis
2 hormones help regulate Ca in blood -bone is major storage site calcium -the level of calcium in the blood depends upon movement of calcium into or out of bone: -enters bone when osteoblasts create new bone; calcium leaves bone when osteoclasts break down bone -two hormones control blood calcium levels-parathyroid hormone and calcitonin
bone matrix
35% organic and 65% inorganic material CONSISTS: organic: collagen (flexible strength) and proteoglycans (traps water) inorganic: hydroxyapatite -found at articular surfaces -replaced by bone in fetal skeleton -avascular - nutrients reach chondrocytes by diffusing through matrix GROW: appositional and interstitial
skeletal system
COMPONENTS: bones, cartilage, tendons, and ligaments FUNCTIONS: -body support : for bearing weight, cartilage firm yet flexible support within certain structures -organ protection -body movement: tendons full of connective tissue, joints -storage: Ca and P stored then released as needed adipose tissue stored in marrow cavities -blood cell protection: gives rise to blood cells and platelets
periosteum
CT membrane covering the outer surface of a bone -outer fibrous layer is dense irregular collagenous CT that contains blood vessels and nerves -inner layers is a single layer of bone cells (osteoblasts, osteoclasts, osteochondral progenitor cells
exocrine glands
Glands that secrete their products into ducts are called
gigantism
abnormally increased body size due to excessive growth at the epiphyseal plates -increase in childern
pituitary dwarfism
abnormally small body size to to improper growth at the epiphyseal plats -decrease GH children
GH abnormailties
age dependent disorders
green stick
bone fragments still attached -incomplete fracture that occurs on the convex side of the curve of a bone
osteomyelitis
bone inflammation often due to a bacterial infection that may lead to complete destruction of the bone
when collagen is removed
bone is britte
complete fracture
bone is broken in two pieces
compound fracture (open)
bone pierces through skin; or bone break with open wound
woven bone
bone that osteoblasts form during ossification is fairly weak bone -collagen fibers randomly oriented in many directions -after forming osteoclasts break down the _______ bone and osteoblasts build new matrix -immature bone, -replaed by mature bone will collagen fibes organized to form lamellae (remodeling)
osteogenesis imperfecta
brittle bones that fracture easily due to insufficient or abnormal collagen
chondrocytes
by the time the matrix surrounds a chondroblast the cell differentiates -round cell that occupies a space within the matrix
callus ossification
callus replaced by woven spongy bone -bone is fractured, blood vessels in the bone and surrounding periosteum are damaged and a hematoma forms -
interstitial growth
cells within tissue divide and add more matrix from the inside - chondrocytes in the center of the tissue divide and add more matrix in-between the existing cells
cartilage model
chondroblasts produce this hyaline____ _____ having the approximate shape of the bone that will later be formed
concentric lamellae
circular layers of bone matrix that surround the central canal
comminuted fractures
complete with break into more than two pieces
lamellae
concentric sheets or layers of mature bone -collagen fibers lay parallel to one another by at an angle to the collagen fibers in the adjeacent lamella
articular cartilage
covers bones; has no perichondrium -hyaline cartilage covers ends of bones where they come together to form joints, has no perichondrium, blood vessels, or nerves GROWTH: increases sizes of bones with no epiphyses: short bones -chondrocytes near the surface are similar to those in zone of resting cartilage
simple fracture
damge localized within skeletal system
osteoporosis
demineralization of bone -> brittle bone -seen primarily in postmenopausal women, -treated with Ca supplements, citamins C &D exercise, hormone therapy
compact (cortical) bone
dense bone arranged into osteons -found throughout diaphysis and covering spongy cones of epiphyses -more matrix and denser; lesser pores -blood vessels enter the bone itself
incomplete fracture
doesn't extend across the bone
perichondrium
double layer of dense fibrous CT, covers outer bone surface -inner layer has osteoblasts, site of growth in bone diameter -2 layered CT membrane covering the outer surface of bone except where articular cartilage is present; ligaments and tendons attach to bone through this section; blood vessels and nerves from the section supply the bone; where bone grows in diameter
epiphysis
ends of long bone -part of the bone that develops from the center of ossification distinct from the diaphysis
yellow marrow
fat stored within medullary cavity
external callus
forms around a collar around the opposing ends of the bone fragments -osteochondral progenitor cells from the periosteum become osteoblasts-> produces bone and chondroblasts, which produce cartilage -collar around opposing ends -periosteal osteochondral progenitor cells-> osteoblasts and chondroblasts -bone/cartilage collar stabilizes two pieces
internal callus
forms between the ends of the broken bone, as well as the marrow cavity if the fracture occurs in the diaphysis of a long bone -blood vessels grow into clot in hematoma -macrophages clean up debris, osteoclasts break down dead tissue, fibroblasts produce collagen and granulation tissue -chondroblasts from osteochondral progenitor cells of periosteum and endosteum produce cartilage within the collagen -osteoblasts invade -> new bone is formed
cancellous (spongy) bone
found within epiphyses arranged in trabeculae -bone having many small spaces; found mainly in the epiphysis; arranged into trabeculae
red marrow
found within spaces of cancellous bone, site of hemtaopoeisis -CT in the spaces of spongy bone or in the medullary cavity; the site of blood cell production
osteon
functional unit of a long bone (haversian system) -composed: concentric rings of matrix ->surround a central tunnel and contain osteocytes
papillary layer
gives rise to fingerprints
rickets
growth retardation due to nutritional deficiencies in minerals or vitamin D: results in bones that are soft, weak, and easily broken
thyroid hormone
hormone required for normal growth of all tissues, including cartilage; therefore a decrease in this hormone can result in a smaller individual
epiphyseal plate
hyaline cartilage between epiphysis and diaphysis -site of vertical bone growth, endochondral ossification -area of hyaline cartilage between the diaphysis and epiphysis; cartilage growth followed by endochondral ossificatioon results in growth in bone length
chondroblasts
hyaline cartilage that produces a matrix surrounding themselves
secondary ossification center
in long bones -the primary ossificiation center and additional sites of ossificaiton, are created in the epiphyses by osteoblasts that migrate into the epiphysis -spaces in the epiphyses do not enlarge to form a medullary cavity as in the diaphysis
hairline fracture
incomplete fracture where two sections of bone do not separate. common in skull fractures
acromegaly
increase GH in adults
dermis
inner layer of skin below the epidermis
rickets
insufficient vitamin D in children -a disease resulting from reduced mineralization of the bone matrix (bowed bones and inflamed joints)
trabeculae
interconnected rods or plates of bone -oriented along the lines of mechanical stress within a bone -can realign itself with the new lines of stress if force on bone changes
fontanels
large membrane-covered spaces between developing skull bones; unossified "soft spots" - incomplete intramembraneous ossification in fetal/newborn skull
mucous membranes
lines cavities in the body
serous membrane
lines cavities in the body
synovial membrane
lines joints of the body
endosteum
lining of marrow cavity, contains osteoblasts -thin CT membrane lining the inner cavities of bone
hematoma formation
localized mass of blood released from blood vessels from blood vessels but confined within an organ or a space -forms a clot, -> fibrous proteins that stop the bleeding
centers of ossification
locations in membrane where ossification begins
long bones
longer bones than they are wide -most upper and lower limbs are long bones
osteomalacia
low vitamin D levels can be one cause of "adult rickets" -softening of the bones due to calcium depletion
reticular layer
main fibrous layer
hypodermis
main site of fat in the skin
parathyroid hormone(PTH)
major regulator of blood Ca levels -secreted from the glands when blood Ca levels are too low, stimulates and increase in the number of osteoclasts , which break bone and elevate blood Ca levels -stimulates osteoblasts to release enzymes that break down the layer of unmineralized organic bone matrix covering bone, thereby making the mineralized bone matrix available to osteoclasts
callus
mass of tissue that forms at a fracture site and connects the broken ends of the bone
tumors
may be malignant or benign and cause a range of bone defects
perichondrium
most cartilage is covered by a protective CT sheath -double-layered outer layer of dense irregular CT (fibroblasts) -inner has fewer fibers and has chondroblasts -outer: blood vessels and nerves penetrate the outer layer *do not enter the cartilage matrix
vitamin D
necessary for absorption of calcium from intestines -can be eaten or manufactured in the bone -rickets -osteomalacia
vitamin C
necessary for collagen synthesis by osteoblasts -scurvy: causes wounds not to heal, teeth to fall out
appositional growth
new matrix/cells added to outside of tissue -chondroblasts in the perichondrium add new cartilage to the outside edge of the existing cartilage -> then chondroblast lay down new matrix and add new chondroCYTES to the outside of tissue
zone of hypertrophy
number three in the picture -the chondrocytes produce in the zone of proliferation mature and enlarge
zone of proliferation
number two in the picture -the chondrocytes produce new cartilage through interstitial cartilage growth -they divide and form columns resembling stacks of plates or coins
impacted fractures
one fragment is driven into spongy portion of the other fragment classified on basiss of direction of fracture: -linear -transverse -spiral -oblique -dentate
bone cells
osteoblasts osteocytes, and osteoclasts
bone collar
osteoblasts produce compact bone on the surface of the cartilage model
matrix vesicles
osteoblasts release this -high concentrations of Ca2 and PO4
osteoprotegerin
osteoclasts production is inhibited by this which is secreted by osteoblasts and other cells
circumferential lamellae
outer surfaces of compact bone -thin plates that extend around the bone
bone remodeling
process where bone that becomes old is replaced with new bone -osteoclasts remove old bone and osteoblasts deposit new bone (woven ->lamellar) CONSISTS: osteoblasts and osteoclasts -formation of new osteons in compact bone -relative thickness of bone changes as bone grows caused by migration of Basic Multicellular Units --groups of osteoclasts and osteoblasts that remodel bones
endochondral ossification
produces long bones -bones develop from within catilage model/template -cartilage is then calcified and dies -osteoblast form bone on calcified cartilage -> spongy bone -outer surface of compact bone is formed beneath periosteum -1 degree ossificiation centers from in diaphysis during fetal development -2 degree ossifciation centers form in epiphyses-> epiphyseal plate -epiphyseal plate closes completely between 18-21 years of age. no vertical possible -articular cartilage remains at ends of bones
osteoporosis
reduction in overall quantity of bone tissue
flat bones
relatively thin, flattened shape and are usually curved
osteoclasts
resorption of bone; bone-destroyed cells FUNCTIONS: -perform reabsorptiom -ruffled border: where cell membrane borders bone and resportion is taking place -H ions pumped across membrane, acid forms, eats away bone -releases enzymes that digest the bone -derived from monocytes -> stems cells in red bone marrow -multinucleated and probably arise from fusion of a number of cells
intramembranous ossification
results in flat bones -occurs within membranes, osteoblasts produce cancellous bone -beneath periosteum, osteoblasts lay down compact bone to form outer shell -fontanels -beings at approximately the eighth week of embyronic development (completed in 2 years)
dentate
rough, toothed, broken ends
short bones
round or nearly cube-shaped -carpal and tarsal bones
diaphysis
shaft of long bone
calcitonin
stabilizes osteoclasts, promotes osteoblast activity -secreted from the thyroid gland when blood Ca levels are too high -inhibits osteoclast activity by binding to receptors on osteoclasts
osteochondral progenitor cells
stem cells that can become osteoblasts or chondroblasts LOCATION: inner layer of the perichondrium and layers of CT that cover cone -potential source of new osteoblasts or chondroblasts
mechanical stress
stress causes bone remodeling to -increase bone mass (density) -align trabeculae with stress changes caused by: osteoblast activity--increases with stress
ligaments
strong bands of fibrous CT that hold bones together contain: bundles of collagen fibers, few nerves/blood vessels
-blast
suffix that means seed or bud -immature cell names q
primary ossification center
the area of bone formation
fibroclasts
the cell type that breaks down fibrous connective tissue is termed ___
zona occluden
the component of the tight junction that prevents passage of materials between cells is termed____
true
the dermis is a vascular tissue? (t/f)
ossification
the formation of new bone by osteoblasts (ostrogenesis -occurs by appositional growth on the surface of previous material 1) elongated cell extensions from osteoblasts connect to cell extension through gap junctions 2) bone matrix is produced by osteoblasts covers the older bone surface and surrounds the cell bodies and extensions ***osteoblasts make oranic matrix and minerals are added ***intramembranous and endochondral process form both spongy and compact bone
callus formation
the internal callus forms between the ends of the bones, and the external callus forms a collar
canaliculi
the spaces occupied by the osteocyte cell extensions
compact
the type of bone found on the periphery of all bones and the shafts of long bones
bone growth
this grows by either appositional or endochondral processes (can not grow via interstitial method)
reproductive hormones
this hormone also influences bone growth initially stimulate bone growth, which accounts for the burst of growth at puberty when production of these hormones increases -
growth hormone
this hormone is very important in bone growth from anterior pituitary increase general tissue growth , including overall bone growth, by stimulating interstitial cartilage growth and appositional bone growth
tuberculosis
typically, a lung bacterium that can also affect bone
irregular bones
vertebrae an facial bones -shapes that do not fit into the other three categories
scurvy
vitamin C deficiency can result in this-> marked by ulceration and hemorrhage in almost any area of the body because normal collagen synthesis is not occuring in CT
product of blood cells
what is hemopoiesis?
demineralized bone
when a bone is bendable
epiphyseal line
when bone growing in length stops the epiphyseal plate becomes ossified
ruffled border
where cell membrane borders bone and resorption is taking place -osteoclast cell membrane then further differentiates into a highly folded form
osteoarthritis
with aging, articular cartilage lost, bone spurs develop -usually attacks larger joint (hip, knee)
