Skeletal System

Question 1

Compare and Contrast terms:

Osteon, Osteocyte, Osteoclast, Osteoblast, Osteoprogenitor, and Osteoid.

Answer 1

Osteon= Unit of bone, contains concentric lamellae, etc
Osteocyte = Mature bone cell, maintains matrix
Osteoclast= Dissolves bone matrix, multinucleate
Osteoblast= Immature cell, secretes osteoid
Osteoprogenitor= Stem cell for osteoblasts
Osteoid= The organic bone matrix

Question 2

The epiphysis of the femoral head is superior to the metaphysis, true or false?

Answer 2

True.

Question 3

Nearest Spongy or Compact Bone:

• Medullary cavity?
• Perforating (Volkmans canal)?
• Osteons?
• Endosteum?
• Perforating (Sharpeys Fibers)?
• Haversian systems?
• Trabeculae?

Answer 3

Spongy
Compact
Compact
Spongy
Periosteum
Compact
Spongy

Question 4

Describe the basic process of intremembranous ossification?

Answer 4

Intramembraneous ossification occurs within non-weight bearing bones, like the skull. The mesenchymal cells become osteoblasts, which become vascularized, produce osteoid which becomes matrix, and continue growing this way until osteocytes form from osteoblasts trapped in matrix, and vessels become trapped forming trabeculae. The spongy bone forms first, then periosteum forms the compact bone superficially.

Question 5

Describe the process of endochondral ossification.

Answer 5

Endochondral ossification occurs within long bones & weight bearing bones. Mesenchymal cells differentiate into chondroblasts, which divide & form a cartilage “rough draft” of bone. The inside breaks down as calcifying matrix starves ‘‘cytes, starting to form the medullary cavity. Vascularization jump starts perichondrium cells -> into osteoblasts. Increase in diameter through appositional growth, folds over vessels. Osteoclasts break down matrix which becomes spongy bone & cavity. Epiphysis vascularized & grows, taking over still dividing chondrocytes. Leaves epiphyseal plate and articular cartilage.