Bone Cells

Osteogenic Cell

• Are Stem Cells

• Only type of bone cell that does mitosis

• Divide to form osteoblasts

• Located in the periosteum and endosteum

Osteo

means bone

Gen

means produce

Osteoblast

• build new bone

• Get trapped and become osteocytes

• Located on the periosteum and epiphyseal plates

Osteoid

Bone matrix (calcium + collagen + water)

Osteocyte

• mature bone cells

• Located in compact bone and spongy bone

• Perform daily functions of bone

Cyte

means cell

Osteoclast

• Clean away bone 

• Located on the periosteum and endosteum

• Used during fracture repair and bone growth (clean way old bone from the medullary cavity)

Clast

means break

Endochondral Ossification

• The formation of bone form cartilage

• Starts in the embryo

Cartilage Model Forms

• First Step

• Starts 6-8 weeks after conception

• Chondrocytes are created to form a model of where the bone will eventually be

• The model is made of hyaline cartilage

Perichondrium & Periosteum 

• 2nd Step

• A perichondrium membrane around the cartilage) forms around the model

• The perichondrium turns to bone and is now called the periosteum 

• Cut off form nutrients by the periosteum, the chondrocytes on the inside start to die and are replaced by bone

Primary Ossification Center

• 3rd Step

• Blood Vessels enter the center of the diaphysis forming the primary ossification center (where ossification of the diaphysis begins)

• With ingredients from the blood, osteoblasts begin building osteoid in the primary ossification center

• Ossification of the diaphysis occurs from the inside-out, starting at the primary ossification center and extending toward the ends of the bone

Medullary Cavity

• 4th Step

• Osteoclasts clean away some newly formed bone in the diaphysis, for

Secondary Ossification Centers

• 5th Step

• Around the time of birth, blood vessels enter the epiphyses forming the secondary ossification centers (where ossification of the epiphyses begins)

• With ingredients form the blood, osteoblasts begin building osteoid in the secondary ossification centers

• Ossification of the epiphyses occurs from the inside-out

Ossification is complete

• 6th Step

• The only cartilage left at the end of endochondral ossification is the articular cartilage and the epiphyseal plates