Lecture 6 Flashcards
FONTANELLE
MEMBRANOUS AREA THAT HAS NOT YET OSSIFIED IN CRANIAL VAULT
*ALLOWS FOR RAPID STRETCHING/DEFORMATION OF CRANIUM AS THE BRAIN EXPANDS AND GROWS
3 MAJOR FONTANELLES
- ) METOPIC
- ) ANTERIOR
- ) POSTERIOR
CLOSURE TIMELINE OF FONTANELLES
- ) POSTERIOR (1-3 MONTHS)
- ) SPHENOID (6 MONTHS)
- ) MASTOID (6-18 MONTHS)
- ) ANTERIOR (7-19 MONTHS)
BULGING FONTANELLES
SUNKEN FONTANELLES
OCCURS W/ AN ACCUMULATION OF FLUID W/IN THE SKULL => HYDROCEPHALUS (INCREASE IN CRANIAL PRESSURE)
CAUSED BY DEHYDRATION OR MALNUTRITION
SUTURE MORPHOGENESIS AND FUSION
- ) AS BRAIN EXPANDS, BONES OF CALVERIA ARE DISPLACED CORRESPONDINGLY OUTWARD
- ) 1˚ DISPLACEMENT CAUSES TENSION IN THE SUTURAL MEMBRANES AND EDGES
- ) 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 - ) BONE FRONTS OVERLAP AND SIGNALS FROM DURA MATER SEND OSTEOGENIC SIGNALS TO THE BONE FRONTS TO PROMOTE RELEASE OF OSTEOID
- ) ONCE SUTURE IS STABILIZED, IT SIGNALS TO THE DURA MATER TO STOP PRODUCTION (NEG. FEEDBACK) OF OSTEOGENIC SIGNALS
- ) DURA MATER ALWAYS REMAINS OSTEOGENIC BUT MORE CONTROLLED… THIS YIELDS OSSEUS OBLITERATION OF SUTURE
DURA MATER –> OSTEOGENIC SIGNALS
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)
TGF-β
REGULATES PROLIFERATION AND DIFFERENTIATION OF MANY CELL TYPES (IMPORTANT ROLE IN BONE REMODELING - POTENT STIMULATOR OF OSTEOBLASTS)
FGF
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
MSX
TRANSCRIPTIONAL REPRESSOR THAT FUNCTIONS IN CRANIOFACIAL DEVELOPMENT, PARTICULARLY ODONTOGENESIS, AND ASSOCIATED W/ NON-SYNDROMIC CLEFT LIP W/ OR W/O CLEFT PALATE
TWIST
TRANSCRIPTIONAL FACTORS IMPLICATED IN CELL LINEAGE DETERMINATION/DIFFERENTIATION OF THE MESODERM
REGULATES CRANIAL SUTURE PATTERNING AND FUSION
RUNX2
TRANSCRIPTIONAL FACTOR THAT ENCODES RUNT-DNA BINDING PROTEIN AND NUCLEAR PROTEINS
REGULATES SKELETAL GENE EXPRESSION AND ESSENTIAL FOR OSTEOBLASTIC DIFFERENTIATION/SKELETAL MORPHOGENESIS
RUNX2 REGULATES OSTEOGENESIS AT 2 POINTS
- ) ACTIVATES MESENCHYMAL PROGENITOR CELLS TO BECOME PRE-ODONTOBLASTS
- ) PROMOTES OSTEOGENESIS THROUGH OSTEOBLASTIC ACTIVITY
CRANIOSYNOSTOSIS
PREMATURE CLOSURE OF SUTURES
NON-SYNDROMIC SYNOSTOSIS
WHEN SYNOSTOSIS IS NOT ASSOCIATED W/ ANY OTHER DEVELOPMENTAL DISEASES
**DUE TO IN UTERO GROWTH CONSTRAINT
1˚ SYNOSTOSIS
FUSION OF 1+ SUTURES PREMATURELY (IF 1+ THEN HIGH CHANCE OF CAUSING BRAIN DAMAGE)
2˚ SYNOSTOSIS
PREMATURE SUTURE FUSION DUE TO PRIMARY FAILURE OF BRAIN GROWTH (NORMALLY DIVIDES BONEY PLATES APART)
SYNDROMIC SYNOSTOSIS
WHEN SYNOSTOSIS IS ASSOCIATED W/ ANOTHER DEVELOPMENTAL DISEASE
- *DUE TO DE NOVO DOMINANT MUTATIONS
- *USUALLY INVOLVES FRFr AND TWIST
TYPES OF SYNOSTOSIS
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)
VIRCHOW’S LAW
W/ SYNOSTOTIC BRAINS GROWTH IS RESTRICTED PERPENDICULARLY TO SYNOSTOSIS AND ENHANCED PARALLEL TO SYNOSTOSIS
DEFORMATIONAL (FRONTAL OR POSTERIOR) PLAGIOCEPHALY
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)
MANDIBULAR DEVELOPMENT FUN FACTS
- ) 2ND BONE TO OSSIFY
- ) DEVELOPED BY IM AND EC OSSIFICATION
- ) DEVELOPMENT STARTS AT WEEK 6
IM OSSIFICATION OF MANDIBLE YIELDS…
YIELDS THE…
WHOLE BODY OF THE MANDIBLE EXCEPT THE ANTERIOR PARTS, FROM THE RAMUS TO THE MANDIBULAR FORAMEN
EC OSSIFICATION OF MANDIBLE YIELDS…
YIELDS THE…
ANTERIOR PORTION OF THE MANDIBLE, MANDIBULAR FORAMEN AND UP (CORONOID/CONDYLAR PROCESS)
IM OSSIFICATION
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)
IM OSSIFICATION CONTINUED
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)
EC OSSIFICATION
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)
DEVELOPMENTAL SEQUENCE OF CONDYLAR PROCESS
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
2˚ CARTILAGE
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
1˚ CARTILAGENEOUS JOINT
BONE + HYALIN CARTILAGE + BONE
2˚ CARTILAGENEOUS JOINT
BONE + HYALINE CARTILAGE + FIBROCARTILAGE + HYALIN CARTILAGE + BONE (I.E. TMJ - ALLOWS SIDE TO SIDE AND FRONT TO BACK PIVOTING MOVEMENTS)
CORONOID PROCESS
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
MENTAL REGION
1-2 SMALL CARTILAGES APPEAR ON EITHER SIDE OF THE MENTAL RIDGE AND OSSIFY AT 7 MONTHS IN UTERO => MENTAL OSSICLES
MENTAL OSSICLES
THIN BANDS OF MESENCHYME CELLS BETWEEN SIDES OF MANDIBLE (INCORPORATED INTO IM BONE WHEN SYMPHASIS OSSIFIES COMPLETELY DURING 1ST YEAR OF POST-NATAL LIFE)
