Bone Formation

Question 1

What are all the types of Bone Formation?

Answer 1

This includes intramembranous and endochondral Ossification.

Question 2

What is Bone Formation called?

Answer 2

This is a process called Ossification or (Osteogenesis).

Question 3

What are the 4 principle situations that bones form under?

Answer 3

These are…

1: Initial bone formation is in the Embryo and Fetus stage.
2: The bones grow in infancy, childhood, adolescence until their adult size.
3: The remodelling of bone.
4: The Repair of bone throughout life.

Question 4

What is Mesenchyme?

Answer 4

This is a type of loose cells embedded in the Extracellular matrix that gives rise to connective tissue.

Question 5

What are the types of bone growth in the Embryo and Fetus?

Answer 5

This includes Intramembranous Ossification and Endochondreal Ossification.

Question 6

What are the 4 steps to Intramembranous Ossification?

Answer 6

The Development of the Ossification centre, Calcification, Formation of the Trabeculea and Development of the Periosteum.

Question 7

What are the steps to Endochondreal Ossification?

Answer 7

1: Development of the Cartilage model
2: Growth in the cartilage model
3: Development of the primary Ossification centre
4: Development of the Medullary cavity
5: development of the secondary ossification centre
6: Formation of the Articular cartilage and Epiphyseal growth.

Question 8

What is included for Bone Growth in Childhood and Infancy?

Answer 8

This is when the bones start to grow in length and Thickness.

Question 9

What are the Steps to Bone Growth in length?

Answer 9

1: Zone of resting cartilage 2: Zone of Proliferating cartilage 3: Zone of Hypertrophic cartilage 4: Zone of Calcified Cartilage.

Question 10

What are the steps to Growth in thickness 1?

Answer 10

1: At the bones surface Periostial cells turn into Osteoblast that secrete collagen fibers that form the Extracellular matrix and then they develop into Osteocytes.
The ridges around the periosteal blood vecessl slowly enlarge and create a new groove.

Question 11

What are the steps to Growth in thickness 2?

Answer 11

The periosteal ridges fuse together forming an Endosteum lined tunnel.

Question 12

What are the steps to Growth in thickness 3?

Answer 12

Osteoblast in the Endosteum build new Concentric Lamellae inward toward centre of tunnel, forming a new Osteon.

Question 13

What are the steps to Growth in thickness 4?

Answer 13

Bone grows outward as Osteoblast in the Periosteum build new circumferential lamellae. Osteon formation repeats as a new periosteal ridge form over the blood vessels.

Overall the process is repeated after this to grow the bone in thickness.

Question 14

What is the Embryonic Skeleton Initially composed of?

Answer 14

It is composed of Mesenchyme in the general shape of bones.
This is the site where Cartilage formation and ossification occurs and the bone formation will follow in one of two ways that include…
Intramembranous and Endochondral ossification.

Question 15

What is the main purpose for the 2 forms of ossification?

Answer 15

They are both used for Replacement of preexisting connective tissue.
They both lead to the same outcome and are just different ways of bone formation.

Question 16

What are the 2 types of bone growth in Infancy - Adolescence?

Answer 16

The bones grow in thickness by processes called Appositional growth and in length called Interstitial growth.

Question 17

What is Appositional Growth in bones?

Answer 17

This is a type of bone growth in thickness

Question 18

What is Endochondral Ossification?

Answer 18

This is the Replacement of Cartilage with bone.

Most bones in the body are formed this way but is best observed in the Long bones.

Question 19

What is step 1 to Endochondral Ossification?

Answer 19

Development of the cartilage model…
Where the bone will form chemical messages cause cells in the Mesenchyme to crowd together in the bones shape and form Chondroblast that form a Cartilage model.
The cartilage model is made up of Hyaline cartilage and a covering called Perichondrium.

Question 20

What is step 2 of Endochondral Ossification?

Answer 20

Growth of the Carilage model:
Once Chondroblast form deep in the Cartilage’s extracellular matrix the cartilage model grows in length by continual cell division of chondrocytes and further secretion on extracellular matrix.
This type of growth is called Intersitial growth which results in an increase in length.

As the models Extracellular matrix grows it classifies and the chondrcytes that cant get blood flow begin to die and the spaces left behind are called Lacunea.

Question 21

What is step 3 to Endochondral Ossification?

Answer 21

Development of the primary ossification centres:
A nutrient Artery enters the Perichondrium and Stimulates the Ostioprojenitor cells to differentiate into Osteoblast and once the Perichondrium starts to form bone it is known as the Periosteum.
The growth of the Primary ossification centre is a region where bone tissue will replace most of the cartilage.
The primary ossification centres spread from the centre to both ends of the Cartilage model.

Question 22

What is step 4 to Endochondral Ossification?

Answer 22

Development of the Medullary cavities:
As the primary ossification centre grows to both ends of the bone Osteoclast break down some newly formed spongy bone trabeculea.
Leaving cavities called Medullary cavities in the Diaphysis.
Eventually most of the wall of the Diaphysis is replaced with Compact bone.

Question 23

What is step 5 to Endochondral Ossification?

Answer 23

Development of the Secondary ossification centre:
When branches of the of the Epiphyseal artery enter the Epiphysis, Secondary Ossification occurs.
The bone formation is similar to the primary ossification centre however the 2nd centre spongy bone remains in the interior of the epiphyses.

Question 24

What is step 6 to Endohondral Ossification?

Answer 24

Formation of Articular cartilage and the Epiphyseal plate:
The hyline cartilage that covers the Epiphysis becomes the Articular Cartilage.
Prior to adulthood Hyline cartilage remains between the Diaphysis and Epiphysis as the epiphyseal plate grows.

Question 25

What is the process of a bones growth in thickness called and how does it occur?

Answer 25

Appositional Growth is the bone growing in thickness by deposition of extracellular matrix material on the cartilage surface of the model by new chondroblast that develop from the Perichondrium.