chapter 6&9

what is most abundant mineral salt in bone extracellular matrix?

calcium phosphate

what is bone extracellular matrix made of?

-water -collagen fibers -cyrstalized mineral salts

calcitriol

-active form of vitamin D -when PTH acts on kidneys to decrease loss of Ca2+ in urine so stimulates to form it -hormone that promotes absorption of calcium from foods in the gastrointestinal tract into blood. elevates blood ca2+ level -PTHstimulates formation

bones role in calcium homeostasis

-bodys major calcium reservoir -maintain level of calcium in blood is to control rates of calcium resorption from bone to blood and calcium deposition from blood into bone -bone helps buffer the blood level= releasing Ca2+ into blood plasma (osteoclasts) when level decreases, and absorbing Ca2+(osteoblast) when level rises -Ca2+ exchange is regulated by hormones

osteoblasts

-bone building cells -synthesize and secrete collagen fibers and other organic compounds to build extracellular matrix -as osteoblasts surround in extracellular matrix the are trapped in their secretion=become osteocytes

calcification

-calcium phosphate + calcium hydroxide=hydroxyapatite -hydroxyapatite crystals form and combine with other minerals and ions(magnesium,fluoride,potassium,sulfate) -mineral salts are deposited in framework formed by collagen fibers of extracellular matrix= crystalize and tissue hardens -process is initiated by bone building cells=osteoblasts

Compact bone

-contains few spaces -strongest form of bone tissue -beneth periosteum of all bones and bulk of diaphyses -[rovides protection and support and resists the stresses produced by weight and movement -osteons

typical long bone consists of 7 things

-diaphysis- shaft/body -epiphyses-ends of bone -metaphyses- between diaphysis and epiphyses -articular cartilage- thin layer of hyaline cartilage over epiphyses that reduces friction -periosteum-layer wrapped around bone, associated with blood supply, rich in sensory nerves=pain felt -medullary cavity- yellow bone marrow -endosteum- layer of bone forming cells

osteoclasts

-from fusion of many as 50 monocytes -all concentrated in endosteum -releases powerful lysosomal enzymes and acids that digest the protein and mineral components of extracellular bone matrix=resorption -resorption =part of development, maintance, and repair of bone=breakdown of extracellular matrix

what 4 zones in epiphyseal plate?

-layer of hyaline cartilage in metaphysis of growing bone -closes when adolesnce comes to end 1.zone of resting cartilage- layer of chondrocyctes. cells do not function in bone growth, but anchor epiphyseal lpate to epiphysis bone 2.zone of proliferating cartilage- chondrocytes like stackof coins. undergo interstital growth and secrete extracellular matrix 3.zone of hypertrophic cartilage-columns of chondrocytes 4.zone of calcified cartilage-dead chondrocytes bc extracellular matrix has calcified. then endochondral ossification. then becomes new diaphysis

osteocytes

-mature bone cells -main cells in bone tissue and maintain its daily metabolism -maintains and monitors the tissue

bone remolding

-ongoing replacement of old bone tissue by new bone tissue -Bone resorption:removal of minerals and collagen fibers from bone by osteoclast. result:destruction of bone extracellular matrix -bone deposition=addition of minerals and collagen fibers to bone by osteoblasts. result=formation of bone extracellular matrix

bone resorption

-osteclast attaches tightly to bone surface at the enosteum/periosteum and forms leakproof seal at edges of ruffled border -releases protein-digesting lysosomal enzymes and acids into sealed pocket -enzymes digest collagen fibers and organic substances while acids dissolve bone minerals -osteoclasts carve out small tunnel in old bone -degraded bone proteins and extracellular matrix minerals enter an osteoclast by endocytosis, cross cell vesicles, and undergo exocytosis on opposite side of ruffled border -in interstitial fluid, products of bone resorption diffuse into nearby capillaries once small area of bone has been resorbed, osteoclasts depart and osteoblasts move in to rebuild the bone in that area

what are 4 type of cells in bone tissue

-osteogenic -osteoblasts -osteocytes -osteoclasts

ossification

-process that bones form 1.formation of bones in fetus and embyro 2.growth of bones during life until adult size 3.remodeling of bone 4.repair of fractures

endochondiral ossification

-replacement of cartilage by bone 1.development of cartilage model:mesenchyme cells crowd together in general future bone shape to develop into chondroblasts, secretes cartilage extracellular matrix=cartilage model of hyaline cartilage=perichondrium 2.growth of cartilage model:once chrondroblasts become deeply buried in cartilage extracellular matrix=chondrocytes. -insterstitial growth: growth from within-length increase-continual cell division of chondrocytes and secretion of extracellular matrix -appositional growth- deposition of extracellular matrix material on cartilage surface by new chondroblasts developed from perichondrium- thickness -as cartilage model grows, chondrocytes in midregion and extracellular matrix begin to calcify -lacunae forms of spaces from dead chondrocytes 3.development of the primary ossification center- primary ossification proceeds inward from external surface of bone. -nutrient artery penetrates perichondrium to become osteoblasts=leads to forms periosteum -Periosteum then primary ossification center where bone tissue replaces cartilage -osteoblasts deposit extracellular matrix over calcified cartilage=spongy bone trabeculae 4.development of medullary cavity: primary ossifcation grows and cavity formed from osteoclast breakdown some of spongy bone=leaves cavity=medullary cavity. then most of wall of diaphysis replaced by compact bone 5. development of secondary ossification centers. epiphyseal artery enter and 2nd ossification center develops. spongy bones remains interior of epiphyses. proceeds outward to surface of bone 6. formation of articular cartilage and epiphyseal plate. hyaline cartilage that covers epiphyses becomes articular cartilage

Functions of Bone and Skeletal System 6

1. Support- support soft tissue and attachment points for tendons 2.Protection- organs from injury 3Assistance in movement- 4.Mineral homeostasis- on demand bone releases minerals to blood 5.blood cell production- red bone marrrow produces red, white, blood cells and platelets 6.triglyceride storage- yellow bone marrow consists of adipose cells -potential energy reserve

what two events are involved for growth of lengthen in long bones?

1. interstitial growth of cartilage on epiphyseal side of epiphysea plate 2. replacement of cartilage on diaphyseal side of epiphyseal plate with bone by endochondral ossification

how is spongy different from compact bone?

1. spongy is light-reduces weight of a bone. allows bone to move more reaily when pulled by muscle 2. trabeculae supports and protects red bone marrow. also only site where red bone marrow is stored and where hemopoiesis (red blood cell production)

intramembranous ossification

1.development of the ossification center:mesenchyme cluster into osteoprogenitor=ossification center, and then into osteoblasts secrete extracellular matrix so then surrounded by it 2.calcification: secretion of extracellular matrix stops=now osteocyctes, lie in lacunae and extend narrow cytoplasmic processes into canaliculi that radiate in all directions -calcium and mineral salts are deposited and extracellular matrix hardens/calcifies 3.formation of trabeculae: as extracelluar matrix form, develops into trabeculae that fueses to form spongy bone around network of blood vessels in tissue. connective tissue in trabeculae 4.development of periosteum: along with formation of trabeculae, mesenchyme condenses at periphery of bone and develops into periosteum. then thin layer of compact bones replaces surface of spongy bone

what 2 principle effects of aging on bone tissue

1.loss of bone mass 2.brittleness- ddecerase rate of protein synthesis

factors affecting bone growth and bone remodeling

1.minerals calcium, phosphorus, magnesium, fluoride, and manganese 2. vitamins- Vitamin A=osteoblast, Vitamin C=synthesis of collagen (main bone protein) 3.hormones most important are IGFs

appositional growth (growth in thickness)

1.periosteal cells become osteoblasts and secrete collagen fiber and organic molecules to form extracellular matrix. then it becomes osteocytes=bone ridges=creates groove for periosteal blood vessel 2.ridges fold together and fuse=groove becomes tunnel that encloses blood vessel. now is endosteum that lines tunnel 3.osteoblast in endosteum deposit bone extracellular matrix=new concentric lamellae=tunnel fills in=new osteon 4.osteon forming+osteoblast desposit new circumferential lamellae=increases thickness of bone

phases to repair bone fracture

1.reactive phase-early inflammatory phase. blood leaks from torn ends of vessels forming lot=fracture hematoma. dead tissue are removed 2.reparative phase:fibrocarilaginous callus formation. 2b. reparative phase: bony callus formation. brgin to form spongy bone trabeculae trabecula join living and dead portion of original bone fragments. noe bony hard callus 3.bone remodeling phase: dead portions of original gragments gradually absorbed by osteoclasts. comapct replaces spongy

insterstitial growth

activity of epiphyseal plate is the only way the diaphysis can increase in length -as bone grows, chondrocytes proliferate on epiphyseal side of the plate -new chondrocytes replace older ones that are destroyed by calicfication -then cartilage replaced by bone on diaphyseal side of plate -when adolescence coms to an end, epiphyseal plate closes (cells stop dividing) and fades leaving the epiphyseal line

interstitial lamellae

areas between neighboring osteons with lammelae, osteocyctes, and canalicli -are fragments of older osteons that have been partially destroyed during bone rebuilding or growth

metalphyseal and epiphyseal arteries

arise from arteries that supply associated joint -ends of long bones -supply red bone marrow and bone tissue -metaphyseal connects with nutrient artery

perforating canals

blood vessels and nerves from periosteum penetrate comapct bone through this

stress fracture

bone fractures without visibly breaking -series of microscopic fissures in bone that forms without any evidence of injury or other tissue

rotation

bone revolves around its own longtiudianl axis

why excersize important?

bone tissue becomes stronger through increased deposition of mineral salts and pruction of collagen fibers by osteoblasts decrease in bone mass occurs when bone resorption by osteoclasts outpaces bone deposition by osteoblasts

fracture

break in a bone

symphyses

cartilaginous joint end of the articulating bones are covered with hyaline cartilage flat disc of fibrocartilage connects the bones

synchondroses

cartilaginous joints connecting material=hyaline cartilage immovable joint

concentric lamellae

circular plates of mineralized extracellular matrix of increasing diameter -surrounding a small network of blood vessels and nerves located in central canal -form a series of parrelel cylinders

flexion

decrease in angle between articulating bones

spongy bone

does not contain osteons -alwasy located in the interior of a bone -protected by a covering of compact bone contains trabeculae -between trabeculae are spaces filled with red and yellow bone marrow -core of epiphysiss and forms narrow rim bordering medullary cavity

fibrocartilaginous callus

fibroblasts produce collagen fibers. periosteum turn into chondroblast and produce fibrocartilage in region. it is a mass of repair tissue consiting of collagen fibers and cartilage that brudges broken ends of bone

suture

fibrous joint composed of thin layer of dense irregular connective tssue -only between bones of skull -importat for shock resitance -immovable or sligtly immovable

syndesmosis

fibrous joint in whih there is a greater distance between articulating surfaces and more dense irregular connective tissue than in sture -permits limited movement

3 structural classifications of joints

fibrous joints- no synovial cavity. dense irreglar connective tissue cartilaginous joints- no synovial cavity. cartilage holds it together snovial joints synovial cavity untied by dense irregular connective tissue of artiular capsule

what does bones hardens and flexibility depend on?

flexibility; collagen fibers hardness: crystalized inorganic mineral salts

osteoprogenitor cells

from mesenchyme=where all connective tissue is formed -unspecialized bone stem cells -only bone cells to undergo cell division=those cells develop into osteoblasts -found in periostum, endosteum, and bone canals with blood vessels

double jointed

greater flexibility in their articular capsules and ligaments

osteons

haversian systems=repeating structural units -compact bone -each concsists of concentric lamellae arranged around central canal -helpss bone resist streching and bending -organization of osteons is not static but changes over time in response to the physical demands placed on the skeleton

parathyroid hormone (PTH)

hormone that increases blood Ca2+ level -negative feedback system -detects lower levels and increase production of cyclic adenosine monophosphate (AMP) -causing PTH synthesis to speed up and mor PTH is released into blood -the presence of higher levels of PTH increaes the number and activity of osteoclasts which step up pace of bone resorption. returns blood ca2+ level to normal

calcitonin

hormone works to decrease blood ca2+ level -when levels rise parafollicular cells secrete this -CT inhibits activity of osteoclasts, speeds blood Ca2+ uptake by bone, accerates Ca2+ deposition into bones -CT promotes bone formation and decreases blood CA2+ level -effective drug for treating osteoporosis because it slows bone resorption

labrum

in ball and socket joints of should and hip fibrocartilaginous lip that from the edge of joint socket -deepens joint socket and increases area of contact between socet and ball like surface

extension

increase in angle between articulating bones

depression

inferior movement -opening mouth to depress mandible

two types of ossification in embyro

intramembranous ossification endochondral ossification both involve the replacement of preexisitng connective tissue, do not lead to difference in structure o mature bones but just different methods of bone developemt

trabeculae

lamellae that are arranged in an irregular pattern of thin columns -red bone marrow and yellow bone marrow are in the spaces between trabeculae that provide nutrients to osteocytes -each one consists of concentric lamellae, osteocyctes that lie in lacunae, and canaliculi -precisely oriented along lines of stress to resist breaking

circumferential lamellae

llamelae arranged around the entire outer and inner circumference of shaft of bone -develop during initial bone formation -outer circumferential llamenae=deep to periosteum with perforating fibers -inner circumferential lamellae=lines meduallary cavity

demineralization

loss of calcium and other minerals from bone extracellular matrix

adduction

movement of a bone toward midline frontal plane

abduction

movement of bone away from midline frontal plane

circumduction

movement of distal end of a body part in a circle

tesile strength

organic molecules and collagen fibers provide resistence to being stretched or torn apart

whats the difference of osteoblast and osteoclast?

osteoBlast Build bones osteoClast Carve out bone

insterstitial growth

part of endochondiral ossification part 2 of growth of cartilage model -cartilage model grows in length by continual cell division of chondrocyctes with further secretion of cartilage extracellular matrix -results in increase of length

appositional growth

part of endochondiral ossification part 2 of growth of cartilage model -growth of the cartilage in thickness -desposition of extracellular matrix materialmaterial on cartilage surface of model by new chondroblasts developed from perichondium -growth of outer surface

nutrient artery

passes through a hole (nutrient foramen) in compact bone near center of diaphysis -entering the medullary cavity, it divides into proximal and distal branches -supply spongy and compact bone with nutrients

canaliculi

radiating in all direction from lacunae fill with extracllular fluid -inside are slender fingerlike processes of oteocytes- neighboring ossteocytes communicate via gap junctions -they connct lancunae with one another and with central canals=provides many routes for nutrients and oxygen to reach the osteocytes and removal of wastes

hemopoiesis

red bone marrow produces red blood cells, white blood cells, and platelets

sex hormones

secretion of hormones cause dramatic effect on bone growth -estrogen and androgens =both sexes -andrenal glands produce androgens with adipose tissue convert androgens to estrogen -responsible for increased osteoblast activity, synthesis of bone extracellular matrix, and growth spurt -contribute to bone remodeling by slowing resorption of old bone and promoting deposition of new bone like promoting apoptisis of osteoclasts

articular discs

shock aborption better fit between artculating bony surfaces providing adaptable surfaces for combined movements weight distribution over a greater contact surface distribution of synovial lubricant across articular surfaces of joint cresent shaped pads of fibrocartilage

periosteal arteries

small arteries accompanied by nerves, enter diaphysis through many perforating canals and supply the periosteum and outer part of the compact bone

lacunae

small spaces between concetric lamellae -contain osteocyctes

ligaments

strength of fibers in fibrous membrane one of principal mechanical factors that fold bones close together in synovial joint

interosseous membrane

substantial sheet of dense irregular connective tissue that binds neighboring long bones -permits slight movement

elevation

superior movement of part of body closing the mouth

articular capsule

surrounds synovial joint encloses synovial cavity unites articulating bones 2 layers fibros membrane-dense irregular- permits movement, but orevents bones from dislocating inner synovial membrane-areolar connective tissue with elastic fibers

3 types of fibrous joints

sutures syndesmoses interosseous membranes

function classification of joints

synarthrosis-immovable joint amphiarthrosis-slightly moveable diathrosis-freely moveable joint

two types of cartilaginous joints

synchondroses symphyses

special structure of synovial joint

synovial cavity-allows considerable movement at joint=freely moveable articular cartilage=layer of hyaline cartilage, reducing cartilage

accessory ligaments

synovial joints extracapsular ligaments-outside articular capsule intracapsular ligaments-in articular capsule excluded from synovial cavity by folds of synovial membrane

where are veins?

they carry blood away from long bones 1 or 2 in nutrient artery many in epiphyseal and metaphyseak and small ones periosteal

tendon sheaths

tubelike bursae -wrap around certain tendons that eperience considerable frictionas they pass through tunnels formed by connective tissue inner layer=visceral layer attached to tendon outerlayer=parietal layer attached to bone

synovial fluid

what synovial membrane secretes -viscous clear or pale yellow fluid -hyaluronic acid secreted by synovial cells in membrane and interstitial fliud filtered from blood plasma -thin film over surface within articular capsule -reduces friction by lubicating joint, abosrbing shock, and supplying oxygen and nutrients to and removing carbon dioxide and metabolic wastes from chondrocyctes in articular cartilage -more fluid=less stress on joints (warm up before excersise)