Development of the Head Flashcards
Development of Face - 4 week in utero? Separates and forms? bilaminar membrane? Anatomy? Stomodeum bounded by?
Separates and forms: - buccopharyngeal membrane separates the oral cavity from the pharynx Bilaminar membrane: split 2 - outer ectodermal layer - inner endodermal layer Anatomy: - stomotodeum - buccopharygneal membrane - cardiac bulge - gut - frontal prominence - first arch Bounded by 5 swellings: - Frontonasal process - 2 mand/max processes
Development of Face - 5 week in utero? form placodes? form of nasal processes? oronasal membranes (separate and rupture)? nasal fin (definition)? maxillary isthmus (defintion)
Placodes:
- nasal and optic placodes arise from thickening of the ectoderm
- nasal placodes sink into mesenchyme forming 2 nasal pits
Form of nasal processes:
- prolif of mesenchyme from the frontonasal process around the openings of the nasal pits delineating the medial and lateral nasal processes
Oronasal membranes:
- separate the primitive nasal and oral cavities
- rupture by week 5 to produce communication between
Nasal fin:
- a sheet of epith in front of each nasal pit
Maxillary isthmus:
- bridge of mesenchyme that joins the max and medial nasal processes
Development of Face - 6 week in utero? mandibular processes (action)? Max/Mand process? Max process growth? naso-optic furrow form (location)? form of nasolacrimal duct? form bucconasal groove?
Mandibular processes:
- fuse forming the lower jaw
Max/MAnd processes meet at the angle of the mouth
Max process growth:
- from those corners, grow inwards beneath the lateral nasal processes towards the medial nasal processes
Naso-optic furrow:
- is formed between the max and the lateral nasal processes
- for each furrow an ectodermal rod of cells sinks below the surface and canalises to form the nasolacrimal duct
Bucconasal groove:
- maxillary process from the medial nasal process
Development of Face - 7 week in utero? Anatomy of the face?
Anatomy of the face:
- lateral and mesial nasal process
- naso-optic groove
- maxillary process
- bucconasal groove
Development of Face - Upper lip development - 2 theories?
2 theories:
- maxillary processes outgrow the medial and nasal processes and meet in the midline
- maxillary processes meet the medial nasal processes, thus the middle third of the lip is derived from the frontonasal process
Summary of facial development?
- Frontonasal process forms forehead, dorsum and apex of the nose
- Lateral nasal prominences from the alae (sides) of the nose
- Medial nasal prominences form the nasal septum, ethmoid bone and cribriform plate
- Maxillary prominences form the upper cheek regions and the upper lip
- Mandibular prominences give rise to the chin, lower lip and lower cheek regions
Development of the palate - 6 weeks in utero - palate develops from? nasal cavity separation? separation of nasal and oral? frontonasal process forms? secondary palate (lateral palatal shelves, derived from), 2nd nasal septum? Palatal anatomy?
- Palate develops from: 2 primordia
- primary palate and secondary palate
Nasal cavities are separated by a nasal septum
Nasal cavities are separated from the oral cavity by the primary palate
Frontonasal process form the nasal septum and the primary palate
Secondary palate: - 2 lateral palatal shelves develop behind the primary palate
- lateral palatal shelves are derived from the maxillary processes
- secondary nasal septum develops behind the primary septum
Palatal anatomy: - nasal septum
- tongue
- palatal shelves
- mandibular bone
- meckel’s cartilage
Development of the palate - 7 weeks in utero - primary oral cavity (filled)? palatal shelves?
Primary oral cavity:
- filled with the developing tongue
Palatal shelves:
- keep on growing till they lies vertically
Development of the palate - 8 weeks in utero - stomodeum? tongue? palatal shelves? formation?
Stomodeum:
- enlarges
Tongue:
- drops due to a change in shape and mandibular growth
Palatal shelves:
- become horizontal and contact each other
Their contact forms the secondary palate
Development of the palate - 8-12 weeks in utero - secondary and primary palate (action)? fusion? shelves (action, fusion)? Ossification of? Intramembranous ossification (4 centres)
Secondary and primary palate:
- 2nd contact the 1st to divide the nasal cavity from the oral cavity
Fusion:
- completed during 12 week
Shelves:
- behind the 2nd nasal septum, shelves form the soft palate and the uvula
- epith at medial edges of shelves fuse to form the epith seam
- seam disintegrates to allow mesenchymal continuity cross the secondary palate
Ossification:
- of the hard palate starts once the palatal shelves fusion is completed
Intramembranous ossification:
- one in each develop maxilla
- one in each palatine bone
Development of the palate - 7-9 week summary of action?
7: initial disposition of palatine shelves on each side of the tongue
8: elevation coincident with the depression of the tongue
9: final fusion
Development of the mandible - location? Meckel’s cartilage (definition)? centre of ossification? future mandible body? separation (plates)
Location:
- initially intramembranously, but layer with the appearance of secondary cartilages
Meckel’s cartilage:
- is a rod of cartilage that develops from the first branchial arch (6w), acts as framework for bone formation
Centre of ossification:
- appears in the fibrous tissue near the future mental foramen (7w)
Bone formation spreads backwards, forwards and upwards
Development of the mandible - formation - plate, separation, growth, tooth bud, bundle, contained, ossifies, bone form, inner and outer wall, ramus, 3 secondary cartilages?
Formation:
- develops as a dense fibrous band around Meckel’s cartilage
- form of plate of bone lateral to the cartilage (future mandible body)
- plates on both sides do not meet and are separated by fibrous tissue thus forming the midline symphysis
- continued bone form leads to increased size
- form alveolar process around developing tooth bud
- neurovasc bundle starts to be surrounded by bone
- Meckel’s cartilage resorbs
- neurovasc bundle becomes contained within bony canal
- most dorsal Meckel’s ossifies to form the ear ossicles
- perichondrium of cart forms ligaments
- alveolar bone forms around tooth germs
- bone resorp on inner wall (Howship’s lacunae)
- bone deposit on outer wall (osteoblast/oid)
- interdental septa
- interradicular bone
- ramus develops as a fibro-cellular condensation (cont with body)
- backward spread ossific
- 3 2nd carts (10-14w)
- condylar cartilage (assoc with coronoid process, region of symphysis)
Development of the Maxilla - location? growth affected? different processes? maxilla growth? sutural growth (how)?
outpocketing?
Location:
- develops intramembranously with the centre of ossification (8w)
- growth affected by development of orbit, nasal and oral cavities
- different processes: palatine, zygomatic, frontal and alveolar
- maxilla grows by remodelling and suture growth
- eyeballs, nasal septum and orbital pad of fat provide forces that separate the maxilla from adj bones, allowing sutural growth
- outpocketing of middle meatus of the nose results in maxillary sinus (4m)
Clinical considerations - failure of fusion of facial processes - types?
Types:
- Median cleft lip
- Bilateral cleft lip
- Oblique facial cleft
- Lateral facial cleft
- Median mandibular cleft
