Create an account
Bone cells (3)
1. Osteoblasts - not trapped by matrix (under endosteum or periosteum
2. Osteocytes - trapped by matrix
3. Osteoclasts - break down
breaks down matrix thru lysosome (which breaks down enzymes)
If you break bone you can rebuild matrix
Bone growth & remodeling (7)
1. Bones grow in length at epiphyseal plate
2. Bones grow in diameter by the combined action of osteoclasts and osteoblasts
3. Osteoclasts enlarge the diameter of the medullary cavity
4. Osteoblasts from the periosteum build new bone around the outside of the bone
5. Bone formation = bone destruction in early to middle years
6. Remodeling activity important in homeostasis of blood calcium levels.
7. Remodeling occurs throughout life
women stop growing around the time of the start of their period, in case they get pregnant. don't want to compete w/baby for calcium.
males have denser bones
Bone marrow (3)
1. Myeloid (myelo=bone marrow) tissue
2. In medullary cavity (long bone) and among trabeculae (spongy bone)
3. Site for the production of blood cells
a. Red marrow
i. In vertebrae, ribs, sternum, pelvic girdle and proximal heads of femur and humerus in ADULTS
b. Yellow marrow
i. Fatty marrow of long bones in adults
Note: kids have RBC in marrow in long bones b/c still growing
1. Matrix dominates (calcium, calcium phosphate, sodium...)
2. Inorganic salt - hydroxyapatite
calcium phosphate (gives bones hardness)
3. Organic matrix - protein fibers = gives you flexibility
Note 1: need both organic and inorganic btw cells.
Note 2: if calcium phosphate is the only thing in the bones then brittle bones and they shattered.
Note 3: is only organic then osteoporosis
high blood calcium levels results in stimulation of osteoblasts and inhibit osteoclasts
Cancellous or spongy bone (3)
helps the bone not be so heavy. Line up the points of stress, not across.
1. Sponge like appearance formed by plates of bone called trabeculae
2. Trabeculae have few osteons or central canals
- No osteocyte is far from blood of bone marrow
3. Provides strength with little weight
- Trabeculae develop along bone's lines of stress
Development of bone (3)
2. Intramembranous ossification - replaces membrane
a. Occurs within a connective tissue membrane
b. Apposition growth
i. Adds bone tissue to outer surface (inside to outside) "suture" is where the bones grew together w/bone cells.
3. Endochondral ossification - replace cartilage
a. Occurs within a cartilage model
b. Bone is deposited by osteoblasts
c. Appositional and Interstitial growth
i. Increases in diameter and length
endochondral ossification 1/2
1. Most bones develop this process
2. Formation of primary ossification center and marrow cavity in shaft of model
a. Bony collar developed by osteoblasts
b. Chondrocytes swell and die
c. Stem cells give rise to osteoblasts and clasts
d. Bone laid down and marrow cavity created
epiphysis - needs to be remodeled (reshaped)
bone grows on the outside and then an inner layer disappears by osteoclasts. this is so the bones don't get too heavy
endochondral ossification 2/2
1. Secondary ossification centers and marrow cavities form in ends of bone
2. Cartilage remains as articular cartilage and epiphyseal (growth) plates
a. Growth plates provide for increase in length of bone during childhood and adolescence
b. Disappear when growth stops
Factors affecting bone growth (8)
1. Deficiency of Vitamin A - retards bone development
2. Deficiency of Vitamin C - results in fragile bones (collagen/fiber in connective tissue)
3. Deficiency of Vitamin D - rickets, osteomalacia - softening of bones, vit D makes bones solid
4. Insufficient Growth Hormone - dwarfism
5. Excessive Growth Hormone - gigantism (beofre fusion), acromegaly (after bone fusion)
6. Insufficient Thyroid Hormone - delays bone growth
7. Sex Hormones - promote bone formation; stimulate ossification of epiphyseal plates
8. Physical Stress - stimulates bone growth (b/c of remodeling)
Functions of bone (5)
to make RBCs
1. Support (ex. to stand up)
2. Protection (ex. cover vital organs)
3. Movement - muscles covers - movement
4. Mineral storage - calcium, 98% of calcium is stored in bone. (too much calc. in blood, then store in bones - like a bank, can add to bank until 30-35)
5. Hematopoiesis (blood formation) - formation of blood cells, RBC, WBC, Platelets
can't live w/o calc.
osteoblasts & osteoclast & calcium
1. during bone formation osteoblasts remove calcium from blood, lowering its circulating levels
2. when osteoclasts are active and breakdown of bone predominates, calcium is released into blood & circulating levels will increase.
osteoclasts, if the level of calcium in the blood is low & vitamin D systhesis (which increases the efficiency of absorption of calcium in the intestines)
no calcium. deterioration of vertebral support.
1. Bones lose mass and become increasingly brittle and subject to fractures
2. More prevalent in women - postmenopausal
3. Men develop later in life - senile
genetics, diet & exercise
parts of long bone (7)
1. Diaphysis - shaft
2. Epiphysis - bulby ends, where muscles attach
3. Epiphyseal plate or disk - cartilage, plate=still growing, line=stopped growing (white line)
4. Medullary or marrow cavity - hollow, living bone has marrow
5. Periosteum - around the bone
6. Endosteum - lines the cavity, inside
7. Articular cartilage - covers head & bottom
Repair of fractures 1/2
1. Fracture tears and destroys blood vessels that carry nutrients to osteocytes
2. Vascular damage initiates repair sequence
3. Callus - specialized repair tissue that binds the broken ends of the fracture together
4. Rapidly growing callus tissue effectively collars broken ends and stabilizes fracture so healing can proceed.
repair of fractures 2/2
1. Normally 8 - 12 weeks (longer in elderly)
2. Stages of healing
a. Fracture hematoma - clot forms, then osteogenic cells form granulation tissue
b. Soft callus
i. Fibroblasts produce fibers and fibrocartilage
c. Hard callus
i. Osteoblasts produce a bony collar in 6 weeks
d. Remodeling in 3 to 4 months
i. spongy bone replaced by compact bone
stages of ossification
cartilage gets blood flow from surface.
ossified the ends - so you can walk
ossified at shaft & cartilage is in between.
(see slide #16)
structure of the osteon (3 & 5 components)
bone tissue can repair itself due to blood supply
1. AKA Haversian systems
2. Permit delivery of nutrients and removal of waste products
a. Lamella - layers, rings, aka matrix
b. Lacunae - dimples (osteon sits in lacunae)
c. Canaliculi - like like little cracks, actually canals
d. Central or Haversian canal - blood vessels, lymphatic vessels
e. Volkmann's or Perforating canals - mainly blood vessels. connects central canals (ex. if one central canal gets clogged then get from here)
types of bone (6)
1. Cancellous (Spongy) Bone - inside bone
2. Compact Bone - outside
3. Long Bones - femur, tibia & humerous
4. Short Bones - carpals, tarsals
5. Flat Bones - skull, sternum
6. Irregular Bones - pelvis
Please allow access to your computer’s microphone to use Voice Recording.
Having trouble? Click here for help.
We can’t access your microphone!
Click the icon above to update your browser permissions and try again
Reload the page to try again!Reload
Press Cmd-0 to reset your zoom
Press Ctrl-0 to reset your zoom
Please upgrade Flash or install Chrome
to use Voice Recording.
For more help, see our troubleshooting page.
Your microphone is muted
For help fixing this issue, see this FAQ.
Star this term
You can study starred terms together