Bone Quiz 1/2 (Development and on is quiz 2) Flashcards
Bone compostion
- organic component
- inorganic component
- all bones, regardless of shape have the same composition
organic component of bones
- mineralized
- 25% of dry weight
- tensile strength (tension, torsional)
- allows bones to bend a bit without snapping
- osteoid (collagen) primary component
- cells and fibers
- cells secondary component:
- osteoblasts- bone forming, lays down osteoid
- osteocytes- maintenance
- osteoclasts- resorption
osteocytes
- become trapped in the bone matrix (lacunae)
- maintain bone health
osteoclasts
- removes bones so it can be replaced
- important for bone health
- so it doesnt become brittle
- macrophages
inorganic component of bone
- 65% of dry weight
- ground substance
- compressional strength- thick, strong
- calcium primary component
- crystalline structure
- hydroxyapatite crystals
if 65% of bone weight is inorganic ground substance and 25% includes fibers and cells, what does the other 10% represent
- water
- fluid
- fibers
- cells
- ground substance
- bone is connective tissue
organic component: cells
-osteoregenerator
form osteoblast
-osteocyte forms after being trapped in lacunae
-osteoclast
organic component: osteoid
- before it is mineralized
- collagen fibers
- mineralization occurs between the collagen fibers and takes the crystalline structure form
inorganic component: crystalline structure
- after mineralization
- crystalline structure
- hydroxyapatite crystals
bone is dynamic
- responds to growth and sex hormones (growth)
- responds to fracture (healing)
- responds to plasma calcium levels (Ca homeostasis)
- responds to stress (modeling and remodeling)
- it is able to be so dynamic bc it is dynamic
bone structure
- structural support for the rest of the body
- a substrate to act upon: movement, breathing
- space for hemopoiesis- blood cell formation
which of the following bones serve to protect thorax organs like the lungs
- ribs
- sternal
bone protection
- skull: brain, sense organs..
- ribcage: thorax organs
- pelvis: pelvic organs
hemopoiesis
- formation of blood cellular components
- stem cells within RED marrow can differentiate into many cell types
- erythrocytes- RBC
- leukocytes- WBC
- osteoclasts- bone resorbing cells (macrophages)
- YELLOW marrow is mostly a site of fat storage
- red marrow is found in cancellous portions of flat bones, vertebral bodies, and long bone epiphyses
Calcium homeostasis
- Ca is necessary for many biological functions
- hormone synthesis
- motor nerve function
- muscle contraction
- bone is the major reservoir of calcium
- low circulating calcium levels will trigger bone resorption to release calcium
- low plasma Ca level: parathyroid releases parathyroid hormone -> produces osteoclasts
- high plasma Ca level: thyroid releases calcitonin -> produces osteoblasts
structural failure
- fractures
- joint reconstruction
- disorders/diseases
fractures
-millions of fractures per year in the US with 5-10% represnetion difficult fractures
joint reconstruction
- 250,000 hip replacement per year
- 300,000 knee replacement per year
disorders/diseases-
- related to serum minerals (calcemias, parathyroidis,. thyroidism)
- abnormal bone remodeling (osteoporosis, osteopetrosis)
- genetic/developmental
- extracellular calcification
osteoporosis
- high osteoclast activity
- low bone density- amount of matter per cm
- reduce resorption rate by exercise
- fracturally greater resorption than formation
osteopetrosis
- no osteoclast activity
- thick walls of the bone
- thinner cavity
- albers-schonberg disease: neurological complications, clotting issues, increased incidence of fracture
osteopetrosis might result from lack of hormone production from which structure
parathyroid
macroscopic structure
- cortical (compact) bone- high density and strength, found at outer surface
- cancellous (spongy) bone- network of bone that transmits stressed to cortical bone (epiphyses and center of bones)
cancellous (spongy) bone
- transmits forces to the cortical bone
- absorbs shock
- deform without breaking easily
- network of bone that transmits stressed to cortical bone (epiphyses and center of bones)
epiphysis
ends of long bone
- cancellous and cortical bone
- formed from secondary ossification center
diaphysis
- midshaft of a long bone
- cortical bone
- formed from primary ossification center
metaphysis
-location of fused growth plate between epiphysis and diaphysis
haversian canal
-central canal of the osteon with blood vessels and nerves
osteon
- circular layers of bone surrounding central canal
- layed down by osteoblasts
- circle of bone with osteocyte in the middle
perisoteum
- superficial fibrous layer and site of bone formation
- outer layer
- fibrous connective tissue and bone forming cells
- lamina are layed down to increase radius
lacunae
- osteocyte locations between bone layers
- osteocytes are trapped here
canaliculi
-little canals that contain osteocyte dendrites
cancellous (spongy) bone
- organic and inorganic
- collagen fibers
- calcium hydroxyapetite
- layers of lamellae
- form thinner trabeculae network
- without osteons
development of bone
- intramembranous ossification
- endochondral ossification
intramembranous ossification
- mesenchymal cells to bone
- no cartilage intermediate
- mesenchymal differentiate into osteoblasts -> form osteons
- woven bone -> remodeled
endochondral ossification
- go from compact cells that differentiate into cartilage which is then replaced by bone
- more common
- mesenchymal differentiate into chondrobalsts
- cartilage forms at the center
- perichondrium
- chondroblasts get trapped and become chondrocytes
- chondrocytes go through hypoxia -> call on oxygen
- chondroclasts come and remove cartilage -> replaced by bone by osteoblasts
- primary ossification center- diaphysis
- secondary ossification center- ossification in epiphysis
mesenchymal cells
- cartilage and bone cell progenitors
- migratory
- can differentiate into many different things
- form within compact regions
periosteal apposition growth
- bone diameter increases through bone deposition at the periosteum
- intramembranous
- thickness of cortical bone typically stays the same through equal resorption and growth
- radial expansion of long bone is intramembranous although longitudinal growth is endochondral
endochondral growth ex
- site of bone length increase
- fracture healing
Which part of long bone represents the location of growth plate fusion
-metaphysis
remodeling
- sequential resorption of bone by osteoclasts and replacement by osteoblasts
- resorption and replacement at the exact same site of the bone
- can be in response to:
1. hormones (loss of estrogen during menopause)
2. low plasma Ca levels (Ca homeostasis)
3. microdamage caused by physical stress
4. mechanical disuse (bone loss)
microdamage
- can damage the osteocyte
- picked up by the dendrites
- call osteoclasts to the site
- forms a new osteon
- remodeling
wolffs law: remodeling
- structural organization of bone reflects its function
- tends to form more bone in high stress areas
- structural organization of bone reflects its function
- trabeculae forms parallel to direction of greatest mechanical loads
- trabeculae oriented to directions of stresses (loads)
- repeated activity of high stress can cause increase in bone mass
- ex. tennis player dominant arm bone will have higher bone mass/density
mechanical disuse
- ex. astronauts- 1-2% of bone mass is lost per month of space flight
- you need some level of stress to maintain healthy bone
