Suture Development

Question 1

What part of an infants skull is closest to adult size?

Answer 1

The neurocranium (cranial vault).

Question 2

Which part of the infant skull grows the most?

Answer 2

The viscerocranium.

Question 3

The newborn face is only an —- of the head. This changed to —- in adulthood.

Answer 3

An eighth.

A half.

Question 4

What are sutures?
What are the 3 sutures in the brain?

What are the 4 main bones in the skull?

Answer 4

Sutures are fibrous joints between the skull bones. They provide some elasticity and movement. At birth, they are generally unfused.

• Sagittal suture
• Coronal suture
• Interfrontal or metopic suture

Parietal, frontal, temporal, occipital.

Question 5

What is the name of the soft stop in the middle of the brain?

Answer 5

Anterior fontanelle.

Question 6

What are infant skulls made up of?

What are the edges of flat bones?

Answer 6

Series of flat bones.

They are osteoblasts (bone-forming tissues). The edges are the part called the suture.

Question 7

What are fontanelles?

Compare their size.

Answer 7

Membrane covered spots in the calvaria (top part of the skull) where three or more bones converge.

They are larger than sutures at birth but diminish in size as calvarial bones grow.
They grow and replenish quickly and have 3 joints instead of 2.

Question 8

What are the names of the sutures in the head called?

Answer 8

Coronal suture, sqaumosal suture, lambdoid suture.

Question 9

What are 3 main facts about sutures?

Answer 9

They are sites of bone growth.
Articulations to provide some elasticity and movement.
Mechanical stress absorbers.

Question 10

What controls bone mass being constantly increased and decreased?

Answer 10

Tension and growth factors (signals from circulation).

Question 11

What does continuous growth of the skull depend on?

What does premature fusion of cranial sutures lead to?

Answer 11

Relies on sutures remaining patent (open and unfused).

Craniosynotosis.

Question 12

What processes cause the convoluted shape (zig-zag) in adult skulls?

Answer 12

Sutures are tension adapted. Growth of the brain pushes the skull bones out and this results in tension at the sutures which induces new bone growth.
Deposition and reabsorption of bone are ongoing process.
Growth factors controls bone formation (cellular and tissues).

Question 13

What determines the direction of facial growth?

Answer 13

The orientation of the sutures.

Question 14

Which sutures are most active during adolescence?

Answer 14

Facial sutures.

Question 15

Why does the face mainly grow outwards?

Answer 15

The grows outwards, can be due to activity of the mouth in the baby.

Question 16

Give some features of a mature suture structure?

Answer 16

Mesenchymal cells in the centre (where the suture is).
Wrapping underneath means a strong suture.
The suture is a site for new bone formation.
The cambian layer is osteogenic.

Question 17

Give the names the of the 3 stages a cell goes through in osteogenesis
What type of ossification is this?

Answer 17

1. Undifferentiated mesenchymal cell
2. Osteoprogenitor
3. Mature osteoblast

Intramembranous (no cartilage)

Question 18

What are the 3 types of sutures?

Answer 18

• Sagittal
• Coronal (overlapping)
• Posterior frontal (coming together and fusing)

Question 19

Sutures of the palate:
What are the two bones here?
What kind of suture is it?

Answer 19

Maxilla and palate.

Open sutures (not fused). Palatine bones fuse later in life.

Question 20

What can happen with palatal expansion?

Answer 20

Tension adaptation - open suture means you can have treatment to make the face wider.

Question 21

Palatal expansion using distraction osteogenesis, what is this?

What can an expansion screw be used for here?

Answer 21

Making a longer bone from a shorter one.

It can separate the two halves of the maxillary complex. Tension induced bone growth and deposition at the intermaxillary/palatine suture results in maxillary expansion.

Question 22

Why does development of the skull start laterally?

Answer 22

Due to neural crest cells.

Expansion then eventually occurs upwards.

Question 23

Give details on calavarial bone development

Answer 23

Ossification starts at the side of the brain and expands backwards.
Expression of bone sialoprotein (in matrix) marks in the initial ossification of calavarial bone.
Growth occurs in apical direction sandwiched between the meninges and the overlying skin.

Question 24

What is calavarial bone development synchronized with?

Answer 24

Brain development

Question 25

What happens when a cranial suture fuses prematurely?

Answer 25

Growth of the skull is restricted. The expansion of the underlying brain is now accommodated by growth at other sutures. Catastrophic is there is no space for the brain to grow.

Question 26

What receptors are important in craniosynostosis?

Answer 26

Fibroblast growth factor receptors.

Question 27

Why do we use mice to study human disease?

Answer 27

• Can examine function by observing consequences of disrupting a gene in a mammalian system
• Make mutations that mimic human genetic mutations
• Easy to do experiments: small, easy to grow
• Mutant mouse serves as a reagent for basis studies pharmaceutical application.

Question 28

What is our hypothesis for what is occurring at the suture?

Answer 28

FGF (fibroblast growth factor) ligand and BMP (bone morphogenetic protein) bind to a FGF receptor. This leads to transcription.