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Ortho #1 > #1 Theories of Growth > Flashcards

#1 Theories of Growth Flashcards

1
Q

Growth = ?

A

Increase in size or number

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2
Q

Develoment = ?

A

Increase in organization, complexity or specialization.

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3
Q

How are deviations from “normal” growth plotted?

A

on a Standard growth chart that shows height and weight.

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4
Q

What is anthropometry?

A

A measurement of head circumference

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5
Q

What is interstitial skeletal growth?

A

Interstitial = “inside the tissues”, growth that occurs by a combination of hyperplasia, hypertrophy, and secretion of extracellular matrix.
*Occurs at all points within the tissue.

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6
Q

What are some examples of interstitial growth?

A
  • All soft tissues
  • Cartilage
  • Cranial base formation
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7
Q

What is appositional skeletal growth?

A

“Addition to surfaces” Growth that occurs by a combination hyperplasia, hypertrophy, and secretion of extracellular matrix.

  • Occurs through the activity of cells in the periosteum.
  • Occurs only at SURFACE of bones.
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8
Q

What are some examples of appositional growth?

A
  • Bony surfaces of cranial vault

- Bony surfaces of maxilla and mandible

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9
Q

Can interstitial growth occur within bone?

A

No

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10
Q

Once cartilage is transformed into bone it continues to grow only by_______.

A

Appositon

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11
Q

What is Endochondral skeletal growth?

A

Bone growth within cartilage

  • ossification centers occur within cartilage
  • Cartilage is transformed into bone
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12
Q

What are some examples of Endochondral skeletal growth?

A
  • Chondrocranium (skull base) = ethmoid, sphenoid and basioccupital bones.
  • Epiphyseal plate cartilage of long bones.
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13
Q

What is Intramembranous skeletal growth?

A

Secretion of bone matrix within and between connective tissue membranes.
* No intermediate formation of Cartilage, nor does it replace cartilage.

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14
Q

What are some examples of Intramembranous growth?

A

Desmocranium: cranial vault, maxilla and mandible.

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15
Q

The Mandible forms via ____________.

A

Intramembranous bone formation just lateral to Meckel’s cartilage.

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16
Q

Where does condylar cartilage of the mandible come from?

A

It develops from an independent secondary cartilage and fuses with the mandibular ramus.
*Not from meckels cartilage.

17
Q

What is surface remodeling?

A

Change in shape of bones.

- The result of bone removal (resorption) in one area and bone addition (apposition) in another.

18
Q

Where does surface remodeling occur?

A

Occurs at the SURFACES of growing endochondral and intramembranous bones!

19
Q

What is Internal Remodeling?

A

Vascular channels within bones bring osteocytes to the area (allows the bone to adapt to mechanical stress)

20
Q

Does internal remodeling change shape of bone or induce growth?

A

No

21
Q

Describe the growth of the cranial vault….

A
  • Flat bones formed by intramembranous formation from ossification centers.
  • No Cartilaginous precursors
  • Periosteal activity results in bone remodeling both at sutures and at inner and outer surfaces
22
Q

Describe growth at the Cranial base….

A
  • Bones of the base of the skull formed by endochondral ossification
  • Formed initially in cartilage then transformed to bone.
  • Ossification centers result in ethmoid, sphenoid and basioccipital bones.
23
Q

What is a Synchondroses?

A

Cartilaginous immovable joint

24
Q

What are the 3 most important synchondrosis?

A
  1. Spheno-ethmoidal
  2. Inter-sphenodial
  3. Spheno-occiptial
25
Q

At the cranial base, ______ growth occurs within the synchondroses.

A

Endochodral

*This lengthens the area of the cranial base.

26
Q

What are the main differences between synchodroses and sutures?

A

While both are junctions between adjacent bones:

  • Syn. are cartilage and sutures are CT.
  • Syn. have endochodral ossification while sutures have direct ossification
  • Syn. = active growth, while sutures = reactive growth.
27
Q

Describe the growth of the nasomaxillary complex…

A
  • Formed entirely by intramembranous ossification.
  • No Cartilaginous precursor
  • Growth occurs by apposition and surface remodeling
28
Q

How does translation of the maxilla occur?

A

The Maxilla is translated downward and forward (away from the cranial base) by the apposition of bone that occurs at circus-maxillary sutures which elongates the maxilla.

29
Q

How does surface remodeling occur in the maxilla?

A
  • Bone in Ant. surface of the maxilla is resorbed and Apposition of bone occurs at the maxillary tuberosity
  • Bone also resorbed in the floor of the nose and apposition of bone occurs at the palate and alveolar process. (this makes palate move downward and widen transversely.
30
Q

How does the mandible grow?

A
  1. Endochondral growth occurs at the cartilage that cover the mandibular condyle.
  2. All other areas grow by surface appositon and remodeling.
31
Q

What directions is the mandible translated?

A

Downward and forward

32
Q

Where are the primary growth sites for mandibular translation?

A

Posterior surface of the rams and the condylar and coronoid processes.

33
Q

Ultimately, what effect does surface remodeling have on the mandible?

A
  1. Body of mandible grows longer
  2. Ramus grows taller
    = more room in the body of the mandible for molars to erupt.
34
Q

What is the difference between a growth center and growth site?

A

Site of growth = location at which growth occurs.

Growth center = location at which independent growth occurs.

*All growth centers are growth sites, but the reverse is not true.

35
Q

Are Sutures growth centers?

A

No! They are growth sites. They react rather than act independently. *the suture theory of growth control is not true.

36
Q

What are the conclusions of the Cartilage theory of growth control?

A
  • Cranial base synchondroses and nasal septum act as independent growth centers, pushing the maxilla forward.
  • Mandibular condyle is merely a growth sites.
37
Q

What are the principles of the Functional matrix theory of growth control?

A
  • Heredity and genes play NO role int he growth of craniofacial skeleton.
  • Growth of the face occurs in response to functional needs mediated by the soft tissue in which bone are embedded.
  • ALL tissues that form bone are nearly growth sites!
38
Q

What is Mandibular Ankylosis?

A

Mechanical restriction due to scarring that prevents the growth of the mandible. (supports the functional matrix theory)

Ortho #1 (9 decks)

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