OSSIFICATION
Another way of saying…
Bone tissue formation

TWO TYPES
1.
Intramembranous ossification: in connective tissue
2.
Endochondral ossification: in cartilage
Both form woven bone, then remodeled.
After remodeling, you cannot tell the difference between these two types of ossification

INTRAMEMBRANOUS
OSSIFICATION
Starts the eighth week of development, ends after 2 years
Includes skull bones, parts of the lower jaw (mandible), collarbones (diaphyses of clavicles)

INTRAMEMBRANOUS
OSSIFICATION

FETAL DEVELOPMENT

ENDOCHONDRAL
OSSIFICATION
Cartilage formation begins at 4 th week of development
Most bones formed this way:
• Base of the skull
• Epiphysis of the clavicles
• Remaining skeletal system

ENDOCHONDRAL
OSSIFICATION

STEPS OF ENDOCHONDRAL
OSSIFICATION
1.
Hyaline Cartilage is where bone will be; periosteum is forming at the time
2.
Osteoblasts from periosteum go into cartilage, starts to form spongy bone: Primary Ossification Center
3.
Osteoblasts create wall of compact bone around primary ossification center
4.
Secondary ossification center : appears in the epiphyses
(usually one month before birth), spongy bone is created all around it
5.
Epiphyseal plate separates these two centers, bone will lengthen until the two centers meet

ENDOCHONDRAL
OSSIFICATION

EPIPHYSEAL PLATE:
-layer of young cells that are making new cells
-this is where bones lengthen
-osteoclasts come and break down the extracellular matrix
-bone lengthening only happens when the cartilaginous cells of the epiphyseal plates are active
-when ossification sites of diaphysis and epiphyses meet, no more lengthening of the bone

FLIPBOOK
1. Create a flipbook showing endochondral ossification
2. Make sure that when you flip it, it changes continuously

DO YOU UNDERSTAND?
1.
Describe the formation of spongy and compact bone during intramembranous ossification
2.
For the process of endochondral ossification, describe the formation of:
1.
Cartilage model
2.
Bone collar
3.
Calcified cartilage
4.
Primary ossification center
5.
Medullary cavity
6.
Secondary ossification center

INTRAMEMBRANOUS

ENDOCHONDRAL
1.
Hyaline cartilage shaped like bones
2.
Center of the diaphysis (cartilage breaks down), periosteum forms around diaphysis (bone collar)
3.
Blood vessels and osteoblasts invade cartilage making spongy bone
4.
Osteoblasts in periosteum makes layer of compact bone
5.
Epiphyses of developing bones are cartilaginous and grow, eventually secondary ossification centers appear
6.
Epiphyseal plates: band of cartilage remains between the two ossification centers

BONE FRACTURES

BONE HEALING

FACTORS AFFECTING
GROWTH
Nutrition
• Vitamin D: needed to absorb calcium from intestines
• Malnutrition can cause slower bone growth

Hormones
• Growth hormone: increases general growth in tissue and bone
• Thyroid Hormone: needed for growth of all tissues, including cartilage

BONES IN SPACE