Suture Development

Question 1

How much of the head is taken up by the face in a newborn versus an adult?

Answer 1

1/8 newborn vs 1/2 adult

Question 2

What are the bones visible from the top of the skull called?

Answer 2

Frontal

Parietal

Question 3

What are sutures?

Answer 3

Fibrous joints between skull bones

Question 4

Why are there sutures in the skull? (2)

Answer 4

Provide elasticity and movement - mechanical stress absorbers

Growth occurs at sutures

Question 5

Are sutures normally unfused or fused at birth?

Answer 5

Unfused

Question 6

What is a fontanelle?

Answer 6

Membrane-covered spot in calvaria where three or more bones converge

Question 7

When do the fontanelles close?

Answer 7

Anterior - 2 years

Posterior, sphenoidal, mastoid - first few months

Question 8

Name the four main fontanelles.

Answer 8

Anterior fontanelle (top of head)

Sphenoidal fontanelle (posterior to eye)

Mastoid fontanelle

Posterior fontanelle (back of skull)

Question 9

What do sutures look like in young humans?

Answer 9

Straight and flat (squamous)

Question 10

What is craniosynostosis?

Answer 10

Premature fusion of sutures

Question 11

What do sutures look like in adults and why?

Answer 11

Convoluted/zigzag

Remodelling by osteoblasts and osteoclasts

Question 12

Explain what tension-adapted growth at sutures means.

Answer 12

Growth of brain pushes skull bones out resulting in tension

Induces new bone growth

Question 13

In what direction does the face grow?

Answer 13

Anteriorly and inferiorly

Question 14

What mechanical movements cause growth at facial sutures?

Answer 14

Suckling

Chewing

Breathing

Question 15

Name the facial sutures which involve the frontal bone. (3)

Answer 15

Frontonasal

Frontomaxillary

Frontozygomatic

Question 16

Name the facial sutures which involve the zygoma.

Answer 16

Zygotemporal

Zygomaxillary

Frontozygomatic

Question 17

Name the facial sutures which do not involve the frontal bone nor the zygoma.

Answer 17

Intermaxillary/median palatine

Nasomaxillary

Question 18

Where is the sagittal suture found?

Answer 18

Between the parietal bones

Question 19

Where are the coronal sutures found?

Answer 19

Between frontal and parietal bones

Question 20

Where is the interfrontal suture found?

Answer 20

Between the frontal bones

Question 21

What is another name for the interfrontal suture?

Answer 21

Metopic suture

Question 22

What part of the suture is osteogenic?

Answer 22

Cambiam layer

Question 23

What is the capsular central zone?

Answer 23

Relatively inert region containing osteocytes

Question 24

What kind of suture is the sagittal suture?

Answer 24

Interlocking

Question 25

What kind of suture is the coronal suture?

Answer 25

Overlapping

Question 26

What kind of suture is the metopic suture?

Answer 26

Fused

Question 27

Why are palatal sutures useful in orthodontics?

Answer 27

Allow palatal expansion via tension adaption/distraction osteogenesis at median palatine suture

Question 28

Name the palatal sutures.

Answer 28

Intermaxillary/median palatine Transverse palatine Interpalatine

Question 29

How does calvarial bone develop in utero? (4)

Answer 29

Starts laterally forming islands then grows apically, sandwiched between meninges and overlying skin Islands coalesce within membrane Synchronised with brain development Intramembraneous ossification

Question 30

The presence of what molecule marks the initial ossification of calvarial bone?

Answer 30

Bone sialoprotein

Question 31

What is plagiocephaly?

Answer 31

Premature fusion of one coronal suture

Question 32

What characterises plagiocephaly?

Answer 32

Raised eyebrow Asymmetry

Question 33

What is brachycephaly?

Answer 33

Premature fusion of both coronal sutures

Question 34

What is trigonocephaly?

Answer 34

Premature fusion of the metopic/interfrontal suture

Question 35

What is characteristic of trigonocephaly?

Answer 35

Ridged forehead

Question 36

What is scaphocephaly?

Answer 36

Premature fusion of the sagittal suture

Question 37

Which form of craniosynostosis is most common?

Answer 37

Scaphocephaly

Question 38

What causes Apert syndrome?

Answer 38

Too much FGF2 signalling due spontaneous mutations (autosomal dominant)

Question 39

What are the characteristics of Apert syndrome? (4)

Answer 39

Malocclusion and delayed tooth eruption Narrow lateral swellings of palate Cleft uvula or cleft soft palate SYNDACTYLY (symmetrical)

Question 40

What is Apert syndrome generally?

Answer 40

Midface malformations with plagio/brachycephaly

Question 41

What causes Crouzon syndrome?

Answer 41

Mutations in FGF2/3

Question 42

What are the characteristics of Crouzon syndrome? (5)

Answer 42

Midface hypoplasia Proptosis (shallow orbits) Crowding, crossbites, ectopic eruption of 6s Normal hands Thin calvarial bones

Question 43

What is Crouzon syndrome (sutures)?

Answer 43

Synostosis of coronal suture in combination with sagittal or lambdoid suture

Question 44

Describe the possible cellular events which occur at sutures.

Answer 44

FGF and BMP bind to cell-surface receptors triggering an intracellular messaging pathway Transcription of TWIST and MSX2 increases to induce cell proliferation and differentiation

Question 45

What do TWIST and MSX2 code for?

Answer 45

Transcription factors

Question 46

What roles does FGF signalling play in bone growth?

Answer 46

Differentiation into osteoprogenitor Differentiation into osteoblast

Question 47

Why would too much FGF potentially cause craniosynostosis?

Answer 47

Too much bone synthesis at suture

Question 48

What bones are involved in the squamosal suture?

Answer 48

Parietal Temporal

Question 49

What bones are involved in the lambdoid suture?

Answer 49

Parietal Occipital