head ana and hx

8/6/2019 head ana and hx

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development of the skull

� at birth:

± frontal and parietal eminences are especially

prominent

± skull of a newborn infant is disproportionately

large compared with other parts of the

skeleton; however, the facial skeleton is small

compared with the calvaria� newborn: ~1/8

� adult: 1/3 of the skull





� large size of the newborn's calvaria

± precocious growth & dev¶t of the brain

� smallness of the face ± rudimentary development of the maxillae,

mandible, & paranasal sinuses

± absence of erupted teeth

± small size of the nasal cavities

The rudimentary development of the face makes the orbits appear relatively large



sutures and fontanelles

� sutures

± membranous tissue spaces separating the

bones of the skull in infants

� fontanelles

± areas where the major sutures intersect in the

anterior and posterior portions of the skull



± anterior fontanelle� at birth = 4 cm to 6 cm in

diameter

� closes between 4 and 26

months of age

� 90% between 7±19 mos

± posterior fontanelle� at birth = 1 cm to 2 cm

� usually closes by 2 months



� softness of the bones and their loose connections at the sutures

± enable the calvaria to undergo changes of shape (molding) during birth

during passage of the baby

through the birth canal

frontal bone becomes flat

occipital bone is drawn out

one parietal bone slightlyoverrides the other



� Within a few days after birth, the shape of the

calvaria returns to normal.

� The resilience of the bones of the fetal skullallows it to resist forces that would produce a

fracture in adults.

� The fibrous sutures of the calvaria also permitthe skull to enlarge during infancy and

childhood.



� increase in the size of the calvaria is

greatest during the first 2 years, the period

of most rapid brain development

� person's calvaria normally increases in

capacity until 15 or 16 years of age

after this, the calvaria usually increasesslightly in size for 3 to 4 years because of

bone thickening



Age Changes in the Face

� mandible

±most dynamic of our bones

� its size and shape and the number of teeth itnormally bears undergo considerable change with

age

±newborn

� consists of two halves united in the median planeby a fibrous tissue joint, the mandibular symphysis



� The mentalprotuberance (chin) begins to

develop in the 2nd year but is not fully

developed until after puberty.

� The two halves of the mandible begin to

fuse during the 1st year and are fused by

the end of the 2nd year.



� body of the mandible in newborn infants ± mere shell lacking an alveolar process

± each half enclosing five primary (deciduous) teeth

± elongates, particularly posterior to the mental foramen, toaccommodate the development and then the bearing of eight

secondary (permanent) teeth, which begin to erupt during the 6th

year of life.

� teeth

± primary (deciduous) teeth� usually begin to erupt in infants of ~ 6 mos of age

± secondary (permanent) teeth

� begin to erupt during the 6th year of life

� not complete until early adulthood



� Rapid growth of the face during infancy and early

childhood coincides with the eruption of primary teeth.

� Vertical growth of the upper face results mainly from

dentoalveolar development.

� These changes are more marked after the secondary

teeth erupt.

� Following complete loss of teeth in old age (or younger if

care is neglected), the alveoli begin to fill in with bone

and the alveolar processes begin to resorb.



� Concurrent enlargement of the frontal and

facial regions is associated with the

increase in the size of the

paranasalsinuses.

� Most paranasal sinuses are rudimentary or

absent at birth.

� Growth of the paranasal sinuses is

important in altering the shape of the face

and in adding resonance to the voice.



Craniosynostosis and Skull

Deformities� Premature closure of the sutures of the

skull (primary craniosynostosis) results in

several skull deformities. ± incidence ~ 1 per 2000 births

± cause unknown, but genetic factors appear to be

important

± prevailing hypothesis

� abnormal development of the cranial base creates

exaggerated forces on the dura mater (outer covering

membrane of the brain) that disrupt normal cranial suture

development



± deformities are much more common in males

± often associated with other skeletal anomalies

± type of deformed skull that forms depends on

which sutures close prematurely



� Scaphocephaly

± premature closure of the sagittal suture

± anterior fontanelle is small or absent ± long, narrow, and wedge-shaped skull

± ~ 1/2 the cases of craniosynostosis

± does not produce abnormal neurological

development





� Plagiocephaly

± premature closure of the coronal or the

lambdoid suture

± occurs on one side only

± skull is twisted and asymmetrical



Plagiocephaly



� Oxycephaly or Turricephaly

± 30% of cases of skull deformity

± involve premature closure of the coronalsuture

± high, towerlike skull

± more common in females



Oxycephaly or Turricephaly

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head ana and hx