chapter 6 P2

Hormones

-IGFs, 产于liver，骨细胞, 生产 osteoblasts, proteins needed to build new bones. -Thyroid hormones promote bone growth -hormone insulin／pancreas／ increase bone proteins.

Initial bone formation

-Intramembranous ossification -Endochondral ossification

Vitamins

-Vitamin A stimulate activity of osteoblasts -Vitamin C needed for synthesis of collagen, the main bone protein. -Vitamin D build bone by increasing the absorption of calcium form food -Vitamin K and B12 synthesized bone proteins

where else PTH act on?

-acts on kidney to decrease loss of calcium ion in the urine. -stimulate formation of calcitriol( the active form of Vitamin D), a hormone that promotes absorption of calcium from foods in the GI into the blood.

Reparative phase(fibrocartilaginous callus formation)

-blood vessel ／fracture hematoma -cells ／chondroblasts ／produce fibrocartilage -fibrocartilageinous callus／ mass of repair tissue consisting of collagen fibers and cartilage that bridges the broken ends of the bone.

what is the role of bone in calcium homeostasis?

-buffer the blood calcium ion level. -release ca2+ into blood plasma( osteoclasts when the level decrease. -absorb Ca2+(osteoblasts) when the level rises.

zone of calcified cartilage

-consist mostly of dead chondrocytes(EM calcified) -osteoclasts dissolve the calcified cartilage and osteoblasts and capillaries from the diaphysis invade the area. -lay down bone EM.replace the calcified cartilage by the process of endochondral ossification. -zone of calcified cartilage becomes the new diaphysis

zone of hypertrophic cartilage

-consist of large, maturing chondrocytes arranged in columns.

Bone remodeling phase

-dead portions of original fragments of broken bone are gradually resorbed by osteoclasts. -compact bone replace spongy bone around periphery of the fracture.

who have higher levels of estrogens?and androgens?

-female have higher level of estrogens -male have higher level of androgens

what happen if calcium ion exceed 9and 11mg/100ml range?

-heart may stop(concentration high) -respiratory rest（concentration low)

four principal situation for bone formation:

-initial formation of bones in an embryo -the growth of bones -remodeling of bone repairs of fractures throughout life

what is the two major events involve in the growth of long bone?

-interstitial growth of cartilage on the epiphyseal side of the epiphyseal plate -replacement of cartilage on the diaphysial side of the epiphyseal plate with bone by endochondral ossification.

Minerals

-large amount of calcium and phosphorus are needed when bones are growing and remodeling.

why bone become brittle?

-loss of collagen fibers in organic part of bone EM makes bone less tensile -in elders, collagen fibers synthesis slows, dues to diminished production of human growth hormone.

Reactive phase

-mass of blood clotted in the fracture site (fracture hematoma) -nearby cells die -phagocyte an osteoclasts begin to remove the dead tissue

factors affect bone growth and remodeling:

-minerals -vitamins -hormones

zone of resting cartilage

-nearest the epiphysis -consist of small, scattered chondrocytes -cell do not function in bone growth -anchor epiphyseal plate to the epiphysis of the bone

function of calcium ion:

-nerve and muscle cell -blood clotting -cofactor in enzyme

what is the benefits of bone remodeling?

-new bone will grow stronger as it grow thicker subject to heavy load. - shape of bone can be altered for proper support based on the stress pattern experience during remodeling process. -new bone is more resistant to fracture than old bone.

Bone remodeling

-ongoing replacement of old bone tissue by new bone tissue. -involve bone resorption, deposition

Reparative phase(Bony callus formation)

-osteogenitor ／osteoblasts／spongy bone trabeculae. -trabeculae join ／original bone fragments -fibrocartilage／spongy bone and the callus is then referred to as bony callus

what hormone work to decrease blood ca2+ level?

-parafollicular cells in the thyroid gland secrete calcitonin. -CT inhibit activity of osteoclasts, speeds blood cat2+ UPTAKE BY BONE. AND ACCELERATES CA2+ DEPOSITION INTO BONES. -PROMOTE BONE FORMATION, DECREASE BLOOD CA2+ LEVEL.

appositional growth of bone:

-periosteal cells differentiate into osteoblasts, secrete collagen fibers and other that form EM. -osteoblast turn to osteocytes -form bone ridge on either side of a periosteal blood vessel. -ridge enlarge and create groove for the periosteal blood vessel. -ridge fold and fuse groove enclose blood vessel -former periosteum becomes endosteum that lines the tunnel -osteoblast in endosteum deposit bone EM form new concentric lamellae. -osteon form,osteoblast deposit new circumferential lamellae increase bone thickness.

what is the cause of stress fracture?

-repeated, strenuous activities such as running, jumping -can result form disease process.(osteoporosis)

zone of proliferating cartilage

-slightly larger chondrocytes arranged like stacks of coins -chondrocytes undergo interstitial growth as they divide and secrete EM. chondrocytes divide to replace those that die at the diaphysial side of the epiphyseal plate.

what is the effect of bone mass loss?

-susceptibility to fractures -deformity -pain -loss of height -loss of teeth

what it mean that epiphyseal cell close?

-the epiphyseal cartilage cells stop dividing -bone replaces all remaining cartilage. -epiphyseal plate fades -leaving epiphyseal line

four zones of epiphyseal plate:

-zone of resting cartilage -zone of proliferating cartilage -zone of hypertrophic cartilage -zone of calcified cartilage

Endochondral ossification step 5

1. branches of the epiphyseal artery enter the epiphyses. 2.secondary ossification centers develop (time of birth) 3.proceed outward from the center of the epiphysis toward the outer surface of the bone.

what response does path make when ca2+ decrease?

1. parathyroid gland(receptor) increase molecule known as cyclic adenosine monophosphate(cyclic AMP) 2. the gene for pth within parathyroid gland(control center) detect the intracellular increase in cyclic AMP (the input) 3.pth synthesis speed up and more pth is released into the blood(the output) 4. higher level of pth increase the number and activity of osteoclasts(effector) which increase the pace of bone absorption. 5. when bone release ca2+ into blood, return blood CA2+ levels to normal.

Endochondral ossification steps:

1.Development of the cartilage model 2.Growth of the cartilage model 3.Development of the primary ossification center 4.Development of the medullary cavity 5.Development of the secondary ossification centers 6.Formation of articular cartilage and the epiphyseal plate

intramembranous ossification steps:

1.Development of the ossification center 2.Calcification 3.Formation of trabeculae 4. Development of the periosteum

Intramembranous ossification step 3

1.EM develop into trabeculae 2.fuse with one another to form spongy bones 3.connective tissue associated with the blood vessels in the trabeculae differentiates into red bone marrow.

phase of repair of bone fracture:

1.Reactive phase 2.Reparative phase 3.Bone remodeling phase

Intramembranous ossification step 1

1.change from osteoprogenitor cells and into osteoblasts 2.osteoblasts secrete the organic extracellular matrix of bone until they are surrounded by it.

Endochondral ossification step 2

1.chondroblasts turn to chondrocytes as they are bury in the cartilage EM. 2.cartilage model grow in length by cell division and accompany by secretion of EM (interstitial (endogenous) growth) 3.growth of cartilage in thickness due to the deposition of EM on the cartilage surface. (appositional(exogenous) growth) 4. As cartilage model continues to grow , chondrocytes begins to calcify other chondrocytes within the calcifying cartilage dies because nutrients can no longer diffuse quickly enough through EM. As these chondrocytes die the space turned to lacunae

Endochondral ossification step 6

1.hyaline cartilage that covers epiphyses becomes the articular cartilage

Intramembranous ossification step 4

1.mesenchyme condenses at the periphery of bone 2.develops into periosteum 3.layer of compact bone replaces the surface layers of the spongy bone.

Endochondral ossification step 1

1.mesenchyme crowd together in the general shape of the future bone. 2.develop into chondroblasts 3.Chondroblasts secrete cartilage EM, producing a cartilage model consisting of hyaline cartilage. 4. A covering called perichondrium develops around the cartilage model.

Endochondral ossification step 3

1.ossification proceed inward 2.nutrient artery penetrates perichondrium and the calcifying cartilage model through a nutrient foramen. stimulating osteoprogenitor cells in the perichondrium to differentiate into osteoblasts. 3.perichondrium turn to periosteum when it starts to form bone 4.periosteal capillaries grow into the disintegrating calcified cartilage induce the growth of a primary ossification center., region where bone tissue will replace most of the cartilage. osteoblasts begin to deposit bone EM over the remnants of calcified cartilage, forming spongy bone trabeculae. ossification spread toward both ends of the cartilage model.

Endochondral ossification step 4

1.osteoclast break down some of the newly formed spongy bone trabeculae. 2. form medullary cavity in the diaphysis 3. walls of the diaphysis is replaced by compact bone.

Intramembranous ossification step 2

1.secretion of EM stops 2.osteoblasts turn to osteocytes 3.calcium and minerals are deposited , EM hardened.

what is the renewal rate for spongy bone?

20%

what is the renewal rate for compact bone per year?

4%

what percent of the total body mass is being remodeled?

5%

what part of the body involve 25% of stress fracture?

Tibia

what digest minerals during bone resorption?

acids

what convert androgens to estrogens?

adipose tissue

what gland produce androgens?

andrenal gland of both sex

what is the growth of bone in thickness during infancy, childhood?

appositional growth

when does bone mass loss for male begin?

begin after age 60.

what happen when there is no mechanical stress?

bone does not remodel properly, bone resorption occur more quickly than bone formation.

stress fracture can be diagnose through what test?

bone scan reveal fracture, X-ray can't.

what happen as new bone tissue is deposited on the outer surface?

bone tissue lining medullary cavity is destroyed by osteoclasts in the endosteum so as bone increase in thickness the cavity enlarge.

what happen when bone is replace under stress?

bone tissues become stronger through increased deposition of mineral salts and collagen fibers by osteoblasts.

Intramembranous ossification

bones forms directly within mesenchyme, occur in flat bones of skull,mandible,

orthodontics

branch of dentistry concerned with the prevention and correction of poorly aligned teeth.

open(compound fratures)

broken end of bone protrude through the skin

what is a effective drug for treating osteoporosis?

calcitonin harvested from salmon because it slows bone resorption.

what cause brittleness?

decreased rate of protein synthesis

what loss of bone mass results from

demineralization, loss of calcium and other minerals.

what are some factors that triggered remodeling of bone?

ecxercise, sedentary lifestyle, change in diet.

what digest collagen fibers during bone resorption?

enzyme

what hormone promote change in widening of pelvis?

estrogens

what typical hormone shut down growth at epiphyseal plate? and the effect of it on female compare to male?

estrogens, because female have more estrogen the bone growth cease earlier.

who is more susceptible to the loss of bone mass in old age?

female, usually begin after age 30, likely to get osteoporosis

when does epiphyseal plate close in female and male?

female-18 male-21

colles fracture

fracture of the distal end of the lateral forearm bone(radius) in which the distal fragment is displaced posteriorly.

pott fracture

fracture of the distal end of the lateral leg bone(tibia), with serious injury of the distal tibial articulation.

how does bone fracture affect the length of bone growth?

fractured bone may be shorter , damage to cartilage accelerate closure of epiphyseal plate

closed reduction

fractured end are brought into alignment by manual manipulation

open reduction

fractured end are brought to alignment by surgical procedure

reduction

fractured ends must brought into alignment

what is the function of parathyroid hormone?

increase blood ca2+ level

what is the growth of long bone by length

interstitial growth

what is the two principal effects of aging on bone tissue?

loss of bone mass and brittleness.

if ct is absent will it cause any symptoms?

no

impacted fracture

one end of fractured bone is forcefully driven into the interior of the other.

what happen after osteoclast depart?

osteoblast moved in and rebuild bone in that area.

what gland secret PTH?

parathyroid gland

what hormone regulate CA2+?

parathyroid hormone

greenstick fracture

partial fracture in which one side of bone is broken and other side is bended, occur in children

ossification(osteogenesis)

process by which bone forms

epiphyseal plate

region responsible for the lengthwise growth of long bone

stress fracture

series of microscopic fissures in bone that forms without any evidence of injury to other tissues.

what is repressible for the sudden growth spurt in teenage year?

sex hormone

bone deposition

the addition of mineral and collagen fibers to bone by osteoblasts

comminuted fracture

the bone is crushed into pieces, small bone fragments lie between.

bone resorption

the removal of mineral and collagen fibers from bone by osteoclasts

Endochondral ossification

the replacement of cartilage by bone, most of the bones in body are form this way

how you detect trace of bone fracture?

thickened area on the surface of the bone

pth operate via a negative feedback system

true

what activity help retain bone mass?

walking, moderate weight lifting, help build and retain bone mass.

an open epiphyseal plate indicate that the person is?

young