Growth And Development Of The Skull Flashcards
What are the two types of ossification of the skull
Intramembranous - mesenchymal cells differentiate into osteaoblasts which secrete osteoid and cells called osteocytes form when trapped ossify during fetal period and starts at the centre and ossifies outwards
Endochondral - cartilage model artery through bone impregnates Cartilage with calcium primary and secondary centres
Where does each of the ossifications of the skull occur
Intramembranous ossification
- flat bones of skull
- parietal frontal
- Easily modified by environmental factors (hydrocephaly)
Endochondral ossification
- bones of the base of the skull
- more complex
- ethmoid and sphenoid
- Tight genetic control
- deformity is achondroplasia
Which sinus is absent at birth
Frontal sinus
What is hydrocephaly
Water on the brain
Brain grows in cav like balloon
Increasing brain volume = lifts membrane bones apart applying tension to the sutures
When is the cranial growth depicted
Dictated in-utero
Why is the brain ~25% formed at birth
To perform essential protective qualities for life such as suckling and coughing
What is special about fontanelles
Soft spots which is a gap where no bone has been developed yet
Anteriofontanelle
Can move and moulded during giving birth to help mother
What does the neonate minimal development have as a positive
Non essential parts are not fully formed so the neonate has small jaws and nose
This all has to do with the compromise of giving birth compromise
Where are both of the fontanelles and when does one close
Anterior and posterior, posterolateral fontanelle
Anterior closes at ~18 months
What is an eminence
Bone that protrudes slightly frontal and parietal
Converted of ossification
How can a baby not hold up its head
Structures such as mastoid process not fully developed so postural muscles such as scm cannot support neck as muscle is unsupported
What is the difference between the pelvic inlet and outlet
Inlet - transverse diameter > AP diameter
Outlet - transverse diameter
What’s it the ratio of skull:face for a neonate and adult
Neonate - 8:1
Adult - 2.5:1
What influences the growth of the jaw
The development and eruption of teeth
Wisdoms don’t
How are various processes of the skull formed
As muscles attach to bones pull on them developing processes
What kind of hormones influence skull growth
Sex hormones
Males - bulkier stronger skull
Female - tensile and delicate
What does the primary cartilaginous joint allow
Synchondroses
In base of skull allow face to be carried forward as it grows
What are the two synchondroses of the skull
Spheno-ethmoidal synchondrosis close at 6
Spheno-occipital activated at birth and close at 25
How is the adult skull light
Lightness optimised by Diploe Orbits Cavities Paranasal sinuses
What are the paranasal sinuses
Air filled spaces Maxilla Sphenoid Frontal Ethmoid
How is the adult skull strong
Near spherical shape
Suture joints crack stoppers
Has a crumple zone and incorps Le fort fractures and buttress syst
What is diploe
Sandwich
Has outer and inner compact bone
And light cancellous centre which is the diploe
This is light and strong
Many holes filled with fatty marrow
Shock absorber
What are the endentulous changes
Alveolar processes resorb from the maxilla and mandible due to loss of teeth
What are the three conformational changes of the skull
Neonate - before birth and of small infant
Adult - usual
Old age - may end up Edentulous
