Growth/Formation of bones

Question 1

Describe the process of appositional growth

Answer 1

-Increases the width of long bones
-Osteoprogenitor cells in the periosteum differentiate into osteoblasts, forming ridges around a periosteal blood vessel.
-Those ridges enlarge and create grooves that fuse to become a tunnel that encloses the blood vessel
-Former periosteum becomes the endosteum that lines the blood vessel
New concentric lamellae are built, creating new osteons and other structures of bone

Question 2

Describe the process of interstitial growth

Answer 2

Increases the length of long bones
Growth occurs at the epiphyseal plate, diaphysis side
Follows endochondral growth as cartilage is made anew at the epiphyseal plate and then converted to the mineralized bone via ossification
1. Zone of resting cartilage= anchors the hyaline of epiphyseal plate to epiphysis
2. zone of proliferating cartilage= actively diving mitotically and secreting ECM
3. Zone of hypertrophic cartilage= sit of large maturing chondrocytes stacked in columns
4. Zone of calcified cartilage= thin area of few calcified chondrocytes, calcified chondrocytes are converted by osteoclasts laying down new bone tissue via endochondral ossification

Question 3

Intramembranous ossification

Answer 3

-Mesenchymal cells differentiate into osteoblasts and group into ossification centers
-Osteoblasts become entrapped by the osteoid they secrete, transforming them into osteocytes
-Newly ossified bone develops in the form of trabeculate, forming spongy bone
-Blood vessels form the red marrow
-Mesenchyme condenses to become the periosteum
-multiple ossification centers

Question 4

Endochondral ossification

Answer 4

-Endochondral ossification occurs in long bones and has primary and secondary ossification centers.
-Primary ossification centers occur within the diaphysis of the long bone and are responsible for creating spongy bone and then compact bone.
-The spongy bone in the diaphysis is carved out to become the medullary cavity, then, the spongy bone gets converted into compact bone.
-Secondary ossification centers occur in the two epiphyses of the long bone and are responsible for producing just spongy bone.
-In secondary ossification, only spongy bone is created in the epiphysis.