Ch. 7.3/7.4- Cartilage Growth and Bone Formation

Question 1

Appositional Growth

Answer 1

Widthwise growth of cartilage

Question 2

Interstitial Growth

Answer 2

Lengthwise growth of cartilage

Question 3

What are the steps of interstitial growth?

Answer 3

1) Chondrocyte within lacunae begins to exhibit mitotic activity.
2) Two chondroblasts are produced by mitosis from the single chondrocyte and inhabit the single lacunae.
3) Each chondroblast produces new matrix and begins separating from the other cell in the lacunae. At this stage each cell is now called a chondrocyte.
4) Cartilage continued to grow internally.

Question 4

What are the steps for appositional growth?

Answer 4

1) Mitotic activity begins within stem cells within the perichondrium.
2) New undifferentiated stems cells and committed cells that differentiate into chondroblasts are formed. Chondroblasts produce new matrix at the periphery.
3) A a result of matrix formation, the chondroblasts push apart and become chondrocytes. Chondrocyte continue to produce more matrix at the periphery.

Question 5

Ossification or osteogenesis

Answer 5

The formation and development of bone connective tissue.

Question 6

Intramembranous ossification’s other names and bones it makes…

Answer 6

Dermal ossification

flat bones of skull, facial bones, mandible, central part of clavicle.

Question 7

When does intramembranous ossification begin?

Answer 7

When mesenchyme becomes thickened and condensed with a dense supply of blood capillaries.

Question 8

What is step one of intramembranous ossification?

Answer 8

1) Ossification centers from within thick regions of mesenchyme (8 weeks of development). Some cells within the dense mesenchyme begin dividing and committed cells formed from this cell division differentiate into osteoprogenitor cells. Some osteoprogenitor cells become osteoblasts and begin secreting osteoid. Multiple ossification centers form as osteoblast increase in number.

Question 9

What is step two of intramembranous ossification?

Answer 9

Osteoid undergoes calcification. Calcium salts are deposited onto the osteoid where they crystalize. When calcification entraps osteoblasts inside lacunae inside the matrix, they become osteocytes.

Question 10

Step three of intramembranous ossification?

Answer 10

Woven bone and its surrounding periosteum form. Initially, the new formed boned is not well organized and is called woven bone (primary bone). Woven bone is replaced by lamellar bone(secondary bone). Mesenchyme that still surround woven neon begins to thicken and then organizes to form the periosteum. Mesenchyme cells grow and develop to form additional osteoblast. Newly formed blood vessels branch through this region. Calcified and intratrabecular spaces are made of spongy bone.

Question 11

Step four of intramembranous ossification?

Answer 11

Lamellar bone replaces trabeculae of woven bone. Internal and external surfaces, the spaces between trabeculae are filled to form compact bone. Internally, the trabeculae are modified slightly and produce spongy bone.

Question 12

What does endochondral ossification start with? What does it produce?

Answer 12

Endochondral ossification starts with hyaline cartilage and produces most of the bones of the skeletal system including upper and lower limbs, pelvis, vertebrae, and the ends of the clavicles.

Question 13

Step one of endochondral ossification

Answer 13

Fetal hyaline cartilage model develops.
Weeks 8-12 of development.
Chondroblast secret cartilage matrix and hyaline cartilage model.
Chondrocytes trapped in lacunae 
Perichondrium surrounds cartilage model.

Question 14

Step two of endochondral ossification

Answer 14

Cartilage calcifies and parietal bone collar forms.
In center of cartilage model, chondrocytes hypertrophy and begin to resorb some of surrounding matrix.
Cartilage matrix beings to calcify.
Chondrocytes in calcified regions die (no nutrient access)
Blood vessels grow toward cartilage while calcifying and penetrates perichondrium.
Stems cells in perichondrium divide to form osteoblasts.
Perichondrium becomes periosteum
Osteoblasts in periosteum secrete osteoid.
Osteoid hardens and becomes pariosteol bone collar around formed shaft.

Question 15

Step three of endochondral ossification

Answer 15

Woven bone and it’s surrounding periosteum form.
Initially newly formed bone is woven bone- not well formed
Woven bone (primary bone) is replaced by lamellar bone (secondary bone)
Mesenchyme around woven bone thickens and forms periosteum.
Mesenchymal cells for additional osteoblasts.
Newly formed blood vessels branch through this area.
Calcified trabecular and intratrabecular spaces are composed of spongy bone.

Question 16

Step found of endochondral ossification

Answer 16

Lamellar bone replaces compact bone as compact and spongy bone form.
Lamellar bone replaces trabeculae of woven bone.
On the internal and external surfaces, spaces between trabeculae are filled and woven bone becomes compact bone.
Internal trabeculae are modified and produce spongy bone.