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3 types of cartilage and their locations

1. Hyaline cartilage: costal cartilages
2. Elastic Cartilage: epiglottis
3. Fibrocartilage: pubic symphysis


5 functions of bone

1. Support
2. Protection
3. Movement
4. Mineral and growth factor storage
5. Blood cell formation

- fat storage
- hormone production


4 classifications of bone and examples of each

1. Long bone: femur
2. Irregular bone: vertebra
3. Flat bone: sternum
4. Short bone: talus


Compact Bone

Smooth looking outer layer, has osteons, lamellar, canaliculi, and central canal


Spongy bone

Internal to compact bone also called trabecular bone, honey comb like, little flat prices of bone called trabeculae (little beams) in living bones the open spaces are filled with yellow or red marrow


Structure of a long bone list all parts

1. Diaphysis: shaft
2. Medullary cavity: center of diaphysis
3. Epiphyses: ends of bone
4. Articular cartilage: cartilage covering the epiphysis
5. Spongy bone: porus bone tissue found at epiphyses
6. Epiphyseal plate/line: where growth cartilage is at bottom of epiphyses
7. Endosteum: membrane that covers the inside of bones
8. Periosteum: membrane covering outside of bones
9. Perforating fibers: connects periosteum to bones
10. Nutrient arteries: deliver nutrients to bones
11. Yellow bone marrow: found in adult medullary cavity
12. Red marrow: found in epiphyses of long bones (femur and humerus)


Microscopic structure of compact bone

1. Central canal: big hole in osteon
2. Osteon: lamella+central canal
3. Circumferential lamellae: lamellae forming outer layer of bone
4. Perforating canal: verticle canal next to central canals
5. Nerve,vein and artery
6. Canaliculi: cracks around lacuna
7. Osteocytes: bone cells in lacuna


Chemical composition of bone

Organic: bone cells and osteoid
- ostegenic cells, osteocytes, osteoblasts, osteoclasts. Osteoid=Glycoproteins,proteoglycans and collagen fibers

Inorganic: mineral salts
Calcium phosphate crystals


Endochondral ossification

A bone developes by replacing hyaline cartilage. The resulting bone is called a cartilage or endochondral bone

Except for clavicle all bones inferior to base of skull are formed by endochondral ossification


Intramembranous ossification

A bone develops from a fibrous membrane and the bone is called a membrane bone.

Forms the cranial bones and (frontal, parietal, occipital, and temporal bones) as well as clavicles. Most bones formed by this process are flat bones


How does endochondral ossification happen

1. Bone collar forms around diaphysis of the hyaline cartilage model. Primary ossification center in mid diaphysis

2. Cartilage in middle of diaphysis calcifies and develops cavities

3. The periosteal bud invades the internal cavities and spongy bone forms

4. The diaphysis elongates and a medullary cavity forms. Secondary ossification centers appear in the epiphyses

5. During childhood and adolescence epiphyses ossify and the only cartilage left is in the epiphyseal plates and articular cartilage


How does intramembranous ossification happen?

1. Mesenchymal cells cluster together and turn into osteoblasts. Ossification centers appear in the fibrous connective tissue membrane, osteoblasts make the first trabeculae of spongy bone.

2. Osteoblasts secrete osteoid which calcifies in a few days. Osteoblasts become trapped and become osteocytes

3. Bone forms in a woven manner instead of lamellae. Vascularized mesenchyme condenses on the outside of woven bone and becomes the periosteum

4. Lamellar bone replaces woven bone just deep to the periosteum. The spongy bone's vascular tissue becomes red marrow



Build bone



Bone cells located in lacuna of compact bone. Maintains bone tissue



Break down bone. Look like snails


Bone growth

During infancy and youth bones lengthen by interstitial growth by growth of the cartilage of the epiphyseal plate until bone growth ends during or after puberty and the epiphyseal plate becomes the epiphyseal line


When and how does bone growth stops

At the end of adolescence chondrocytes in epiphyseal plate divided less often. The plates become thinner and thinner until they are entirely replaced by bone tissue. Longitunal bone growth ends when epiphysis and diaphysis fuse (called epiphyseal closure) only articular cartilage


When does epiphyseal closure happen

18 yrs in females, 21 in males


Bone remodeling

Also called Appositional growth. Is regulated by hormones and stress on the bone. Osteocytes detect stress osteoblasts secrete osteoid on one side of the bone which becomes calcified while on the other side osteoclasts reabsorb bone. Remodeling goes on through out life


Types of fractures

1. Comminuted
2. Compression
3. Spiral
4. Epiphyseal
5. Depressed
6. Greenstick


Comminuted fracture

- bone fragments into 3-4 pieces. Common in aged and brittle boned people


Compression fracture

-Bone is crushed
-Common in porous bones subjected to extreme trauma, such as a fall


Spiral Fracture

-ragged break occurs when excessive twisting forces are applied to a bone

-common sports fracture


Epiphyseal fracture

- Epiphysis and diaphysis separate at epiphyseal plate
- occurs where cartilage cells are dying and matrix is calcifying


Depressed fracture

- Broken bone portion is pushed inward
- typical of skull fracture


Greenstick fracture

- Bone breaks only part way like a green twig. Other side bends

- common in children whose bones are more flexible and contain organic matrix


Repair of fractures

1. A hematoma forms
2. Fibrocartilage callus forms
3. Bony callus forms
4. Bone remodeling occurs


Fracture classification

- position of the bone ends after fracture (non displaced and displaced fractures)

- completeness of break. If broke is broken through (complete fracture) if not (incomplete fracture)

- wether bone ends penetrate skin if fracture does it is a compound/ open fracture if not it is a simple/ closed fracture


Treatment of a fracture

- Reduction: put back in place
- in closed reduction bone is popped back in place

- in open reduction the bone is surgically put together with pins or wires.
- After a broken bone is reduced it is immobilized by a cast or traction to allow healing



Means soft bones. Includes a number of disorders in which bones are poorly mineralized. Osteoid is produced but mineral salts are not adequately deposited resulting in soft weak bones. It is called rickets in children. Causes pain on weight bearing bones. Results in bowed legs and other deformities in children. Caused by insufficient calcium or vitamin D in diet