Bone development, Bone growth, Bone remodeling

Question 1

2 patterns of bone formation during fetal development

Answer 1

intramembranous ossification

endochondral ossification

Question 2

Intramembranous ossification

Answer 2

Bone forms from preexisting connective tissue membranes

Question 3

Endochondral ossification

Answer 3

Bone forms from a preexisting cartilage model

Question 4

Centers of ossification

Answer 4

Locations in membrane where ossifications begins

Question 5

Fontanels

Answer 5

Soft spots
Membrane covered spaces between developing skull nbones
Close by 2 years old

Question 6

Steps of intramembranous ossification (3)

Answer 6

1. Mesenchymcal cells differentiate into osteochondral progenitor cells> specialize to become osteoblasts > produce bone matrix > become osteocytes > develop trabeculae of woven bone
2. Osteoblasts gather on surface of trabeculae > produce more bone > enlarge trabeculae > Form spongy bone
3. Cells w/in spongy bone specialize and form bone marrow. Cells surrounding bone specialize and form periosteum. Periosteum lays down bone matrix to form compact bone

Question 7

Cartilage model

Answer 7

First step in endochondral ossification; has approximate shape of eventual bone

Question 8

Bone Collar

Answer 8

Made in step two of endochondral ossification

Compact bone on the surface of the cartilage model

Question 9

Hypertrophy

Answer 9

Enlargement

Question 10

Calcified cartilage

Answer 10

Simulataneous to bone collar formaiton in step 2 of endochondral ossification
Initial formation of hydroxyapatite crystals in cartilage matrix, made by chondrocytes releasing matrix vesicles.

Question 11

Calcified cartilage

Answer 11

Simultaneous to bone collar formation in step 2 of endochondral ossification
The initial formation of hydroxyapatite crystals in cartilage matrix, made by chondrocytes releasing matrix vesicles.

Question 12

Secondary ossification centers

Answer 12

Found in epiphyses of long bones

Question 13

Steps in endochondral ossification

Answer 13

1. Cartilage model formed
2. Blood vessels invade the perichondrium of the cartilage model > produce bone collar. At the same time, the cartilage model increases in size due to appositional and interstitial growth, chondrocytes hypertrophy,

Question 14

Steps in endochondral ossification

Answer 14

1. Cartilage model formed
2. Blood vessels invade the perichondrium of the cartilage model > produce bone collar. At the same time, the cartilage model increases in size due to appositional and interstitial growth, chondrocytes hypertrophy, and release matrix vesicles to form calcified cartilage.
3. Primary ossification center occurs in the diaphysis of bone, creating trabeculae and spongy bone.
4. Woven bone is converted to lamellar bone, the medullary cavity is created, and red bone marrow production begins
5. Secondary ossification centers created in epiphyses
6. Replacement of cartilage by cone continues until bones are done growing,
7. epiphyseal plate hardens to an epiphyseal line

Question 15

When is a baby full term?

Answer 15

If a secondary ossification center can be seen on a radiograph at the time of birth in either the femur, tibia, or humerus.

Question 16

4 zones of the epiphyseal plate

Answer 16

zone of resting cartilage
zone of proliferation
zone of hypertrophy
zone of calcification

Question 17

Zone of resting cartilage

Answer 17

The nearest epiphysis; contains slowly dividing chondrocytes

Question 18

Zone of proliferaiton

Answer 18

produces new cartilage through interstitial growth

Chondrocyte division looks like stacks of plates

Question 19

Zone of hypertrophy

Answer 19

chondrocytes in the zone of proliferation enlarge

Question 20

Zone of calcifcation

Answer 20

A thin area of hypertrophied chondrocytes and calcified cartilage matrix.
Hypertrophied chondrocytes die and blood vessels from diaphysis grow into that area
Osteoblasts line the surface of the calcified cartilage and deposit new bone matrix

Question 21

Growth in bone width steps (4)

Answer 21

1. Osteoblasts form ridges separated by grooves, which nest blood vessels
2. Groove changes to a tunnel when the periosteum ridges meet
3. New lamella created by appositional growth
4. More concentric lamella produced to fill in the tunnel and make a complete osteon.

Question 22

Factors affecting bone growth

Answer 22

Genetics
Nutrition
Hormones

Question 23

Nutritional factors that affect bone growth

Answer 23

Vitamin D

Vitamin C

Question 24

Rickets

Answer 24

caused by a lack of VItamin D

Can result in bowed bones or inflamed joints

Question 25

Scurvy

Answer 25

caused by lack of vitamin C

Slows growth, ulceration and hemorrhage, slow wound healing, loss of teeth.

Question 26

Vitamin D’s function

Answer 26

absorbs calcium from intestines

Question 27

Vitamin C’s function

Answer 27

required for collagen synthesis by osteoblasts

Question 28

3 hormones that impact growth

Answer 28

Growth hormone
Thyroid hormone
Reproductive hormones

Question 29

Why are females shorter than males?

Answer 29

Estrogen causes quicker closure of the epiphyseal plates

Question 30

Bone remodeling

Answer 30

When old bone is replaced with new bone

Question 31

Basic multicellular unit (BMU)

Answer 31

assembly. of osteoclasts and osteoblasts that travel through the surface of the bone to remodel bone matrix

Question 32

Average lifespan of BMU

Answer 32

6 months

Question 33

How often does BMU renew the entire skeleton?

Answer 33

Every 10 eyars

Question 34

Bone density increase and decrease is caused by

Answer 34

Changes in mechanical stress to teh bone. More stress > bone is remodeled in a stronger way; less stress > osteoclasts more active than osteoblasts, bone density is lost.