Bone Formation & Growth: Osteoblasts, Ossification, and Regulation

Osteoblast

Bone-forming cell

Osteoclast

Bone-remodeling cell

Intramembranous ossification

Bone formation from connective tissue; how the bones of the skull form

Endochondral ossification

Bone formation from a hyaline cartilage model; how the rest of the bones of the body form

Hyaline cartilage model

The cartilage template of the future bone that endochondral ossification starts from

Primary ossification center

Site in the center of the cartilage model that blood vessels invade first, bringing in osteoblasts

Secondary ossification center

Site in each epiphysis that blood vessels invade after the primary center, where osteoblasts replace cartilage with spongy bone

Diaphysis

The shaft of a long bone; osteoblasts migrate along it converting cartilage to bone

Epiphysis

The end of a long bone; site of the secondary ossification center

Epiphyseal plate

Region of cartilage left in the epiphyses after calcification; where bones grow in length

Spongy bone

Bone type deposited first by osteoblasts in both forms of ossification

Compact bone

Dense bone tissue deposited by osteoblasts around the spongy bone

Calcium phosphate

Nonliving material formed from calcium and phosphorus that makes up most bone tissue

Calcium and phosphorus

Minerals that form calcium phosphate; the more stored in bone, the stronger it is

Vitamin D

Needed for bone tissue to absorb calcium

Vitamin A

Needed to mature cartilage cells

Somatotropin

Growth hormone secreted by the pituitary gland that regulates the epiphyseal plates

When bone formation occurs

Before birth and continues for the rest of a person's life

When a baby's bones calcify

Within the first month of life; bones are not completely calcified at birth

Bone remodeling is based on demand

The body only maintains a level of bone density based on need

How bones grow in length

Cartilage cells in the epiphyseal plates divide, old cells are pushed away from the center, then calcify and become bone

How bones grow in diameter

Bones widen over time; the larger the diameter, the stronger the bone

Steps of intramembranous ossification

Connective tissue cells become osteoblasts, osteoblasts deposit spongy bone around themselves, then deposit compact bone around the spongy bone

Steps of endochondral ossification

Cartilage model forms, blood vessels invade the primary center, osteoblasts replace cartilage with bone, secondary centers form in the epiphyses, and epiphyseal plates remain

Bone-forming cell

Osteoblast

Bone-remodeling cell

Osteoclast

Bone formation from connective tissue; how the bones of the skull form

Intramembranous ossification

Bone formation from a hyaline cartilage model; how the rest of the bones of the body form

Endochondral ossification

The cartilage template of the future bone that endochondral ossification starts from

Hyaline cartilage model

Site in the center of the cartilage model that blood vessels invade first, bringing in osteoblasts

Primary ossification center

Site in each epiphysis that blood vessels invade after the primary center, where osteoblasts replace cartilage with spongy bone

Secondary ossification center

The shaft of a long bone; osteoblasts migrate along it converting cartilage to bone

Diaphysis

The end of a long bone; site of the secondary ossification center

Epiphysis

Region of cartilage left in the epiphyses after calcification; where bones grow in length

Epiphyseal plate

Bone type deposited first by osteoblasts in both forms of ossification

Spongy bone

Dense bone tissue deposited by osteoblasts around the spongy bone

Compact bone

Nonliving material formed from calcium and phosphorus that makes up most bone tissue

Calcium phosphate

Minerals that form calcium phosphate; the more stored in bone, the stronger it is

Calcium and phosphorus

Needed for bone tissue to absorb calcium

Vitamin D

Needed to mature cartilage cells

Vitamin A

Growth hormone secreted by the pituitary gland that regulates the epiphyseal plates

Somatotropin

Before birth and continues for the rest of a person's life

When bone formation occurs

Within the first month of life; bones are not completely calcified at birth

When a baby's bones calcify

The body only maintains a level of bone density based on need

Bone remodeling is based on demand

Cartilage cells in the epiphyseal plates divide, old cells are pushed away from the center, then calcify and become bone

How bones grow in length

Bones widen over time; the larger the diameter, the stronger the bone

How bones grow in diameter

Connective tissue cells become osteoblasts, osteoblasts deposit spongy bone around themselves, then deposit compact bone around the spongy bone

Steps of intramembranous ossification

Cartilage model forms, blood vessels invade the primary center, osteoblasts replace cartilage with bone, secondary centers form in the epiphyses, and epiphyseal plates remain

Steps of endochondral ossification