Lecture 6

Question 1

FONTANELLE

Answer 1

MEMBRANOUS AREA THAT HAS NOT YET OSSIFIED IN CRANIAL VAULT

*ALLOWS FOR RAPID STRETCHING/DEFORMATION OF CRANIUM AS THE BRAIN EXPANDS AND GROWS

Question 2

3 MAJOR FONTANELLES

Answer 2

1. ) METOPIC
2. ) ANTERIOR
3. ) POSTERIOR

Question 3

CLOSURE TIMELINE OF FONTANELLES

Answer 3

1. ) POSTERIOR (1-3 MONTHS)
2. ) SPHENOID (6 MONTHS)
3. ) MASTOID (6-18 MONTHS)
4. ) ANTERIOR (7-19 MONTHS)

Question 4

BULGING FONTANELLES

SUNKEN FONTANELLES

Answer 4

OCCURS W/ AN ACCUMULATION OF FLUID W/IN THE SKULL => HYDROCEPHALUS (INCREASE IN CRANIAL PRESSURE)
CAUSED BY DEHYDRATION OR MALNUTRITION

Question 5

SUTURE MORPHOGENESIS AND FUSION

Answer 5

1. ) AS BRAIN EXPANDS, BONES OF CALVERIA ARE DISPLACED CORRESPONDINGLY OUTWARD
2. ) 1˚ DISPLACEMENT CAUSES TENSION IN THE SUTURAL MEMBRANES AND EDGES
3. ) AT THE SAME TIME, NEW BONE FORMED ON THE FLAT SURFACES BOTH ECTO- AND ENDOCRANIALLY
   * INDUCTIVE SIGNALS FROM BONE FRONTS (OSTEOGENIC FRONTS - WHERE MESENCHYMAL DIFFERENTIATION AND CONDENSATION OCCURS) ALLOW BONE TO DEFLECT AWAY OR BUTT UP AGAINST ONE ANOTHER W/O OBLITERATING THE SUTURE
4. ) BONE FRONTS OVERLAP AND SIGNALS FROM DURA MATER SEND OSTEOGENIC SIGNALS TO THE BONE FRONTS TO PROMOTE RELEASE OF OSTEOID
5. ) ONCE SUTURE IS STABILIZED, IT SIGNALS TO THE DURA MATER TO STOP PRODUCTION (NEG. FEEDBACK) OF OSTEOGENIC SIGNALS
6. ) DURA MATER ALWAYS REMAINS OSTEOGENIC BUT MORE CONTROLLED… THIS YIELDS OSSEUS OBLITERATION OF SUTURE

Question 6

DURA MATER –> OSTEOGENIC SIGNALS

Answer 6

IF THIS SYSTEM MALFUNCTIONS AND DURA MATER STAYS ACTIVE AND CONTINUES TO PROMOTE OSTEOGENESIS IT CAN YIELD OVERABUNDANCE OF CALCIFICATION AND PREMATURE CLOSURE OF SUTURE (I.E. CRANIAL SYNOSTOSIS)

Question 7

TGF-β

Answer 7

REGULATES PROLIFERATION AND DIFFERENTIATION OF MANY CELL TYPES (IMPORTANT ROLE IN BONE REMODELING - POTENT STIMULATOR OF OSTEOBLASTS)

Question 8

FGF

Answer 8

INVOLVED IN PROLIFERATION/DIFFERENTIATION OF CELLS AND TISSUES THAT PROMOTE ANGIOGENESIS, WOUND HEALING, AND EMBRYONIC DEVELOPMENT
REGULATES GROWTH IN BONE CELLS BY LIMITING FORMATION OF BONE FROM CARTILAGE

Question 9

MSX

Answer 9

TRANSCRIPTIONAL REPRESSOR THAT FUNCTIONS IN CRANIOFACIAL DEVELOPMENT, PARTICULARLY ODONTOGENESIS, AND ASSOCIATED W/ NON-SYNDROMIC CLEFT LIP W/ OR W/O CLEFT PALATE

Question 10

TWIST

Answer 10

TRANSCRIPTIONAL FACTORS IMPLICATED IN CELL LINEAGE DETERMINATION/DIFFERENTIATION OF THE MESODERM
REGULATES CRANIAL SUTURE PATTERNING AND FUSION

Question 11

RUNX2

Answer 11

TRANSCRIPTIONAL FACTOR THAT ENCODES RUNT-DNA BINDING PROTEIN AND NUCLEAR PROTEINS
REGULATES SKELETAL GENE EXPRESSION AND ESSENTIAL FOR OSTEOBLASTIC DIFFERENTIATION/SKELETAL MORPHOGENESIS

Question 12

RUNX2 REGULATES OSTEOGENESIS AT 2 POINTS

Answer 12

1. ) ACTIVATES MESENCHYMAL PROGENITOR CELLS TO BECOME PRE-ODONTOBLASTS
2. ) PROMOTES OSTEOGENESIS THROUGH OSTEOBLASTIC ACTIVITY

Question 13

CRANIOSYNOSTOSIS

Answer 13

PREMATURE CLOSURE OF SUTURES

Question 14

NON-SYNDROMIC SYNOSTOSIS

Answer 14

WHEN SYNOSTOSIS IS NOT ASSOCIATED W/ ANY OTHER DEVELOPMENTAL DISEASES
**DUE TO IN UTERO GROWTH CONSTRAINT

Question 15

1˚ SYNOSTOSIS

Answer 15

FUSION OF 1+ SUTURES PREMATURELY (IF 1+ THEN HIGH CHANCE OF CAUSING BRAIN DAMAGE)

Question 16

2˚ SYNOSTOSIS

Answer 16

PREMATURE SUTURE FUSION DUE TO PRIMARY FAILURE OF BRAIN GROWTH (NORMALLY DIVIDES BONEY PLATES APART)

Question 17

SYNDROMIC SYNOSTOSIS

Answer 17

WHEN SYNOSTOSIS IS ASSOCIATED W/ ANOTHER DEVELOPMENTAL DISEASE

• *DUE TO DE NOVO DOMINANT MUTATIONS
• *USUALLY INVOLVES FRFr AND TWIST

Question 18

TYPES OF SYNOSTOSIS

Answer 18

1) METOPIC (TRIGONOCEPHALY)
TRIGONO- =TRIANGULAR
2) SAGITTAL (SCAPHOCEPHALY)
SCAPHO- (OR DOLICHO-) = BOAT
3.) CORONAL (PLAGIOCEPHALY)
1- POSTERIOR
2- BRACHYCEPHALY (BRACHY- = SHORT)
PLAGIOS- = SKEWED
4.) LAMBDOID (POSTERIOR PLAGIOCEPHALY)

Question 19

VIRCHOW’S LAW

Answer 19

W/ SYNOSTOTIC BRAINS GROWTH IS RESTRICTED PERPENDICULARLY TO SYNOSTOSIS AND ENHANCED PARALLEL TO SYNOSTOSIS

Question 20

DEFORMATIONAL (FRONTAL OR POSTERIOR) PLAGIOCEPHALY

Answer 20

RESULT OF REPEATED PRESSURE TO THE HEAD (NOT CAUSED BY FUSED CRANIAL SUTURES)
DFP - COMMON PRIOR TO 1991
DPP - COMMON POST 1991 DUE TO RECOGNITION OF SIDS => MOTHERS PUTTING BABIES TO SLEEP ON BACK (DECREASE IN SIDS LEAD TO AN INCREASE IN DPP)

Question 21

MANDIBULAR DEVELOPMENT FUN FACTS

Answer 21

1. ) 2ND BONE TO OSSIFY
2. ) DEVELOPED BY IM AND EC OSSIFICATION
3. ) DEVELOPMENT STARTS AT WEEK 6

Question 22

IM OSSIFICATION OF MANDIBLE YIELDS…

Answer 22

YIELDS THE…

WHOLE BODY OF THE MANDIBLE EXCEPT THE ANTERIOR PARTS, FROM THE RAMUS TO THE MANDIBULAR FORAMEN

Question 23

EC OSSIFICATION OF MANDIBLE YIELDS…

Answer 23

YIELDS THE…

ANTERIOR PORTION OF THE MANDIBLE, MANDIBULAR FORAMEN AND UP (CORONOID/CONDYLAR PROCESS)

Question 24

IM OSSIFICATION

Answer 24

SINGLE OSSIFICATION CENTER FOR EACH HALF OF THE MANDIBLE ARISES IN WEEK 6 IN UTERO IN THE REGION OF THE BIFURCATION OF THE INFERIOR ALVEOLAR NERVE AND ARTERY INTO THE MENTAL AND INCISIVE BRANCHES
MANDIBULAR NERVE SECRETES ITS OWN FACTORS THAT HELP PROMOTE OSTEOGENESIS (CLOSE ASSOCIATION BETWEEN MECKEL’S CARTILAGE AND INFERIOR ALVEOLAR NERVE)

Question 25

IM OSSIFICATION CONTINUED

Answer 25

OSSIFICATION SPREADS FROM THE CENTERS AT THE MIDLINE AND FORM THE REGION NEAR THE SYMPHASIS AND RAMUS
POSTERIOR-MOST EXTREMITY OF MECKEL’S CARTILAGE = MALLEUS, INCUS AND SPHENOMANDIBULAR LIGAMENT (DEGENERATES COMPLETELY BETWEEN THE AREA OF THE LINGULA AND MENTAL FORAMEN)

Question 26

EC OSSIFICATION

Answer 26

YIELDS THE MENTAL PROTUBERANCE, HEAD OF THE CONDYLE AND CONDYLAR CARTILAGE, CORONOID PROCESS, AND CORONOID CARTILAGE, AND MENTAL OSSICLE CARTILAGE

**ARTICULAR CALCIFIED CARTILAGE = CORONOID CARTILAGE, MENTLE OSSICLE CARTILAGE, CONDYLAR CARTILAGE (APPEARS BETWEEN 10-14 WEEKS IN UTERO)

Question 27

DEVELOPMENTAL SEQUENCE OF CONDYLAR PROCESS

Answer 27

AT WEEK 5 OF IN UTERO DEVELOPMENT, MESENCHYMAL CONDENSATION OCCURS ABOVE THE VENTRAL POINT OF DEVELOPING MANDIBLE
AT WEEK 10 A CONE-SHAPED CARTILAGE (ARTICULAR CARTILAGE REMAINS TO ACT AS UPWARD GROWTH AFTER BIRTH
AT WEEK 14 OSSIFICATION BEINGS FOLLOWED BY INFERIOR MIGRATION AND FUSION AT 4 MONTHS
*MANDIBLE GROWS IN LENGTH THROUGH PUBERTY ~20 YEARS OLD

Question 28

2˚ CARTILAGE

Answer 28

CONDYLAR, CORONOID, AND SYMPHYSEAL CARTILAGE (CONDYLAR = EQ. TO EPIPHYSEAL PLATES OF LONG BONE)
FIBROCARTILAGE THAT MEDIATES GROWTH
FORMS ON THE ORIGINAL MEMBRANE OF THE BONE
MEDIATES PERIPHERAL GROWTH IN FIBROCARTILAGE
PROLIFERATING CELLS = UNDIFFERENTIATED MESENCHYMAL CELLS
RESPONSIVE TO MECHANICAL STIMULI AND PROMOTES DIFFERENTIATION INTO CHONDROBLASTS AND NOT OSTEOBLASTS

Question 29

1˚ CARTILAGENEOUS JOINT

Answer 29

BONE + HYALIN CARTILAGE + BONE

Question 30

2˚ CARTILAGENEOUS JOINT

Answer 30

BONE + HYALINE CARTILAGE + FIBROCARTILAGE + HYALIN CARTILAGE + BONE (I.E. TMJ - ALLOWS SIDE TO SIDE AND FRONT TO BACK PIVOTING MOVEMENTS)

Question 31

CORONOID PROCESS

Answer 31

2˚ ACCESSORY CARTILAGE APPEARS BETWEEN 10-14 WEEKS IN UTERO
GROWS IN RESPONSE TO DEVELOPING TEMPORALIS MUSCLE
BECOMES INCORPORATED INTO THE EXPANDING IM BONE OF THE RAMUS AND DISAPPEARS BEFORE BIRTH

Question 32

MENTAL REGION

Answer 32

1-2 SMALL CARTILAGES APPEAR ON EITHER SIDE OF THE MENTAL RIDGE AND OSSIFY AT 7 MONTHS IN UTERO => MENTAL OSSICLES

Question 33

MENTAL OSSICLES

Answer 33

THIN BANDS OF MESENCHYME CELLS BETWEEN SIDES OF MANDIBLE (INCORPORATED INTO IM BONE WHEN SYMPHASIS OSSIFIES COMPLETELY DURING 1ST YEAR OF POST-NATAL LIFE)