The nature of Growth

Question 1

What does growth refer to?

Answer 1

Increase in size or number of a structure.

Question 2

What are the 3 terms used to describe growth?

Answer 2

Velocity: amount of growth per unit time

Direction: Vector of growth

Magnitude: Measured change in linear or angular size

Question 3

What is development?

Answer 3

Increased complexity or specialization of a structure

Question 4

How is growth documented?

Answer 4

Growth curves that demonstrate changes in anatomical size over time which allows pattern determination.

Cumulative (distance) curve: Accumulation of size increases

Incremental (velocity) growth curve: Amount of size increase per unit time.

Question 5

How does the typical incremental (velocity) curve look?

Answer 5

Greatest velocity of growth happens initially in newborns and this rate declines slowly until the adolescent growth spurt.

Question 6

What does growth pattern tell us about growth?

Answer 6

Growth pattern is similar for all healthy persons.

Pattern of growth is very important to understand and provides the change in proportions of different parts or structures.

Expression follows the same pattern in most people.

Question 7

What is the cephalocaudal gradient?

Answer 7

The cephalocaudal gradient is important to understand and means that the structures that are closest to the head develop first and that’s why 50% of baby’s body is the head of a 2 month old baby in the womb.

This is a pattern of proportional size not absolute size (percentage of total body size)

Question 8

What are scammon’s curves?

Answer 8

Growth curves for the 4 major body systems relative to their adult size.

Question 9

Where are scammon’s curve important for?

Answer 9

Important concept for orthodontics and for current environment where sleep apnea is an issue.

Question 10

Note of what we need to know about scammon’s curves:

Answer 10

Need to be able to draw them need to be able to know what’s going on. Scammon’s curves are largest in neural system whereas lowest in reproductive system.

Question 11

Does growth variability exist?

Answer 11

Growth variability can happen for healthy and unhealthy patients.

Question 12

Does growth variability exist?

Answer 12

Growth variability can happen for healthy and unhealthy patients. Variation is predictable in healthy individuals whereas in unhealthy individuals it shows different tracking compared to the growth graphs. This is known as CROSSING OF PERCENTILES.

Variation can happen in timing. Especially around adolescence with different people getting their growth spurts at different times. Quantity of growth is often about the same.

Question 13

How does timing typically affect growth?

Answer 13

Early growers tend to peak and later growers tend to grow for longer.

Question 14

How does environment affect growth?

Answer 14

The extent to which growth is attained is determined mostly by environmental factors.

All post natal influences: Nutrition, disease, climate, and orthodontic intervention

Question 15

Where do head and neck structures arise from?

Answer 15

Most of the structures of the head and neck are derived from neural crest cells

Question 16

Where is the ear derived from?

Answer 16

The ear is derived from the first and second brachial arch.

Question 17

What are the stages of craniofacial morphogenesis and formation?

Answer 17

1 Bilaminar disk formation
2 Gastrulation
3 Neurulation
4 Facial primordia
5 - 6 Facial processes migrate
7 - 8 Face forming
9 - 10 Face formed
11 - 12 Palate and TMJ formed

Question 18

What do neural crest cells do?

Answer 18

Neural crest cells peak in how the face develops.

Because of the capacity of neural crest cells to differentiate and migrate they can form the teeth the head the face the adrenal glands.

They are bilateral paired strips of cells that migrate and differentiate and form the key aspects of the teeth head and face.

Question 19

What is the embryological origin of the head?

Answer 19

Entire head from the neural crest cells except:

Muscles of facial expression and endothelial lining of blood vessels which arise from mesoderm.

From ectoderm is the epidermis, CNS, and tooth enamel.

Question 20

What are pharyngeal arches

Answer 20

Pharyngeal arches are a series of externally visible anterior tissue bands lying under the early brain where the notocord is developing and give rise to the early structures of the head and neck.

Question 21

What are the arches made up of?

Answer 21

5 arches in humans: 1 2 3 4 and 6.

Each arch is identical and made from the same components. There is an inner and outer endodermal pouch, mesenchymal core tissue containing mesoderm and neural crest, a membrane containing endoderm and ectoderm and an external cleft containing ectoderm

Question 22

What are the important arches for dentists? What do they form?

Answer 22

Arches 1 and 2 are important for us.

1: Mandibular branchial arch forms maxillary facial process, mandibular facial process, Meckel’s cartilage
2: Branchial arch (hyoid): Reicher’s cartilage (stapes)