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
Cleft lip and Cleft palate - types and explanation? Stats? Epith remnants?
Types:
- Unilateral; failure of maxillary processes to fuse, with the merged medial nasal process
- Bilateral; failure of mesenchymal masses in both max process to meet and unite with the merged medial nasal process
- Median: mesenchymal deficiency
Stats:
- 1/2500, females
- caused by multifactorial
Epith remnants:
- in palatine midline might lead to form of midline palatine cyst
Development - Eye? Induction?
Eye development: results from a series of inductive signals and from the following structures;
- neuroectoderm of forebrain
- surface ectoderm of head
- mesoderm between the above 2 layers
- neural crest
Development - stages 1 of eye development? (Begins? Appear? Evaginate? Contact?)
Begins: - at 4th week Appear: - optic groove appear in neural folds Evaginate: - to form optic vesicles and optic stalks Contact: - optic vesicles contact the surface ectoderm
Development - stages II of eye development? (Thickens? Formation? Invaginate? Lose connect?)
Thickens:
- surface ectoderm thickens to form lens placodes
Formation:
- lens pits and lens vesicles form from the lens placodes
Invagination:
- optic vesicles invade to form double-walled optic cups
Lose connect:
- lens vesicles lose connect with the surface ectoderm and enter the cavities of the optic cup
Development - stages III of eye development? (Develop? Angio? Degen? Transform?)
Develop:
- retinal fissures develop on optic cups and stalks
Angio:
- mesenchymak tissueninnthe fissure develop hyaloid vessels
Degen:
- distal part of hyaloid vessel degen
Transform:
- proximal part persists as central artery of retina and vein
Development of eye - retina? (Formation? Layers and anatomy/description?)
Formation: - walls of optic cup Layers: - outer thin layer (retinal pig epith) - inner thick layer (neural retins) Anatomy: - photoreceptor (rods and cons), develop from the neural retina under influence of develop lens - intraretinal splace (cavity of optic cup), disappears as 2 layers of retina fuse
Development of the eye - ciliary body? (Anatomy/Description?)
Anatomy:
- ciliary body (wedge shaped extension of choroid)
- clilary processes (medial processes or ciliary body)
- pig portion of ciliary epith (derived from the outer layer of optic cup)
Development of the eye - iris? (Develop from? Derived?)
Develop from:
- rim of optic cup
Derived:
- stroma of iris derived form neural crest tissue
- dilator pupillae and sphincter pupillae are derived from the neuroectoderm of optic cup
Development of the eye - lens - develops from? Lining? Form/obliterate? Produce?)
Develop from:
- lense vesicles (derivatives of surface ectoderm)
Lining:
- ant wall of vesicles lined by cuboidal epith (lens epith)
Form/obliterate:
- tall columnar epith of post wall will from primary lens fibres and obliterate cavity of lense vesicles
Produce:
- cells of equatorial zone produces secondary lense fibres
Development of the eye - choroid, sclera and cornea - date? Surrounded? Differentiates? Forms? Develops? Form from?)
End of week 5
Surrounded:
- eye primordium is surrounded by loose mesenchyme
Differentiates:
- differentiates into an inner and outer layer
Forms?
- inner layer forms vascularised pig layer of choroid
Develops:
- and outer develops sclera
Forms from:
- cornea from surface ectoderm, mesoferm and neural crest cells
Development of the eye - aqueous chambers - relation to eye? Develops? Drain? Complications?
Relation to eye:
- ant and post chamber of eye
Develops:
- left like space develops in mesenchyme between lens and cornea
Drains:
- both chambers drain via canal of schlemm
Complications:
- congenital glaucoma (abnormal drainage/rubella)
Development of the eye - vitreous humor - primary/secondary vitreous - (location? Forms from? Vasc?) And (formed from? Vasc? Role?)
Primary: Location: - between developing lens and retina Forms from: - mesenchyme Vasc: - yes
Secondary: Formed from: - retina Vasc: - no Role: - pushes vasc of primary into centre
Development of the eye - eyelids? Nasolacrimal duct? Lacrimal duct? Overview?
Eyelids:
- develop from reduplication of the surface ectoderm
Nasolacrimal duct:
- derived from ectoderm of the nasolacrimal furrow
Lacrimal duct:
- develops fro number of solid buds from the surface ectoderm
Overview:
- all small and font fucntion until 6 weeks after birth
Development of the eye - congenital anomalies - retinal detachment (fuse)? Colobima of retina/iris (close)?
Retinal detachment:
- failuren of outer and inner layers of optic cups to fuse
Coloboma of retina/iris:
- failure to close retinal fissure
Development of the eye - summary of derivations - neuroectoderm of forebrain? Surface ectoderm? Mesoderm?
Neuroectoderm:
- retina, optic nerve fibres, muscle of iris, epith of iris and ciliary body, sphincter and dilator muscles of iris
Surface ectoderm:
- lens, epith of lacrimal glands, conjunctiva, cornea and eyelids
Mesoderm:
- eye muscles, at CT and vasc of corneaz iris, ciliary body, choroid and sclera
Development of the ear - internal ear stage I - date? Inductive? Thickening? Invaginates?
Date:
- early 4th week
Inductive:
- influence of notochord and paraxial mesoderm
Thickening:
- of surface ectoderm (optic placode) appears on each side of causal part of hindbrain
Invaginates:
- optic placode invaginates to form otic pit and otic vesicles (primordium of mem labyrinth)
Development of the ear - internal ear stage II - (loose connection? Elongate? 2 regions?)
Loose connection:
- otic vesicles looses with the surface ectoderm
Elongate:
- form endolymphatic duct and sac
2 regions:
- dorsal utricular part and ventral saccular part
Development of the ear - internal ear III - grow? Fuse/disappear? Grows/coils? Differentiates?
Grow:
- three disc-like diverticula grow out from the utricular part
Fuse/disappear:
- central parts fuse and disappear and peripheral unfused parts from semicircular ducts
Grows/coils:
- from saccular part cochlear duct grows and coils to form membranous cochlea
Differentiates:
- spiral organ differentiates form cells in the wall of the cochlear duct
Development of the ear - spiral organ and perilymphatic space - surrounded? Develop/formation? Filled with/surrounded? Form with?
Surrounded:
- cochlear duct surrounded by cartilagenous otic capsule
Develop/formation:
- vacuoles develop in the otic capsule leading to form of scala tympani and vestibuli
Filled with/surrounded:
- perilymphatic fluid and surrounded by bone (bony labyrinth)
Form with:
- cochlear duct forms organ of corti with hair cells
Development of the ear - external ear and middle ear?
External acoustic meatus:
- dorsal part of first groove
Tympani membrane: from 3 sources;
- ectoderm (1st groove), endoderm (tubotympanix recess and mesoderm (1st and 2nd arches)
Auricle:
- mesenchymal prilid of 1st and 2nd arches
Development of the ear - middle ear - develop from?
Develop from:
- auditory tube, tympanic cavity and mastic tantrum develops from tubotymapnic recess
- malleus and Incus from 1st arch cartilage
- staples from 2nd arch cartilage
Development of the ear - congenital anomalies?
Deafness:
- genetic, first arch syndrome, rubella infection (affects the development of spinal organ and deafness)
Auricular abnormalities:
- auricular appendages (skin tags) - development of accessory auricular hillocks
Placodes - what are they? names?
What are they: - discrete patches of thickening embryonic epith associated with development of embryonic structures Placodes: - Lens - Otic - Olfactory - Trigeminal - Geniculate - Petrosal - Nodose
