Bone Development and Calcification Dr. Jack L. Haar Department of Anatomy Sanger Hall 9-064

Mechanisms of bone formation Intramembranous. 1 Mechanisms of bone formation Intramembranous 1. Ossification with mesenchymal origin Woven bone with low mineral content

b. Growth and appearance Spicules anastomose forming spongy bone

c. Conversion of spongy to compact bone. Lamellation continues c. Conversion of spongy to compact bone Lamellation continues Primitive Haversian system lined by endosteum results

Ossification with connective tissue origin Ossification with connective tissue origin Periosteal band forms in this way

Some bones develop entirely intramembranously However, intramembranous ossification is partially responsible for development of most other bones

Endochondral bone formation Hyaline cartilage model forms Regressive changes in cartilage Increased vascularization to perichondrium Periosteal band forms Periosteal bud supplies blood vessels and osteoblasts to interior

B. Endochondral bone formation Bone is deposited on calcified cartilage Looks like spongy bone

B. Endochondral bone formation Newly formed bone looks like spongy bone It formed on calcified cartilage spicules

Importance of Endochondral Ossification Allows bones to grow in length Due to interstitial growth of the cartilage

Primary center of Ossification in diaphysis Forms the Epiphyseal plates Cells form recognizable zonation

Resting zone – zone of reserve cartilage Zone of proliferation

Zone of maturation – cells hypertrophy

Zone of calcification, degeneration,

Area of bone ossification and resorption

In epiphysis (secondary center for ossification) Articular cartilage remains

Bone Growth Long bones grow in length from epiphyseal plate Long bones grow in width from periosteum or endosteum

Flat bone growth Deposition at the sutures Deposition on the convex surface and Resorption from the concave surface

Remodeling of bone: Deposition and resorption involved

III. Remodeling of bone

III. Remodeling of bone

III. Remodeling of bone

Remodeling of bone Occurs constantly as shown in microradiograph of bone from a healthy 19-year-old male

C. Fracture repair Fibroblasts and capillaries form granulation tissue Dense CT forms followed by cartilage Periosteum and endosteum form new bone Remodeling of bone

IV. Joints A. Synarthroses – limited or no movement

IV. Joints B. Diarthroses

B. Diarthrosis Synovial membrane (synovium) Sqamous or cuboidal epithelial cells Supplied with vessels nerves, lymphatics Fibrous capsule continuous with periosteum

Synovial fluid Filtrate of blood High in Hyaluronic acid Lubricant for cartilage Provides nutrients to cartilage

http://www. path. uiowa. edu/virtualslidebox/ Table of Contents http://www.path.uiowa.edu/virtualslidebox/ Table of Contents Skeletal System Bone Developing #12 Endochondral ossification (no number)