Anatomy of Spongy Bone/Bone Development

trabecula

small beam tissue element of spongy bone that contains several layers of lamellae

endosteum

trabeculae nutrient source

red bone marrow

found between the spaces in spongy bone

ossification/osteogenesis

process of bone formation

situations of bone formation

1) Formation of bone embryo

2) Growth of bones until adult hood

3) Remodeling of bone throughout life

4) Repair of fractures

intramembranous ossification

bone forms directly within MESENCHYME arranged in layers that resemble membranes

intramembranous ossification locations

skull bones and clavicles

endochondral ossification

bone forms within HYALINE cartilage, replacing it

endochondral ossification location

all bones from base of skull down (except the clavicles)

lengthening of bones

1) Cartilage growth on the epiphysis side of the epiphyseal plate

2) Replacement of cartilage by bone on the diaphysis side

adulthood

epiphyseal plates close and bone replaces all the cartilage leaving a bony structure called the epiphyseal line

osteoblasts

add bone tissue to the circumferential lamellae

osteoclasts

remove bone from inner diaphyseal wall at about the same rate as osteoblasts

bone resorption

- osteoclasts secrete HCl and lysosomal enzymes

- released ions (Ca2+) enter interstitial fluid and then blood

- collagen fibers and dead osteocytes are phagocytosed

bone deposition

occurs when bone is injured or added demand is placed on the bone

bone deposition process

osteoblasts lay down bone tissue and calcium salts crystallize in a pattern to reduce the risk of cracks in stressed bone