Development of the Face & Palate


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  • Created by: Becca
  • Created on: 28-12-13 15:04
What is the primitive mouth (stomatodeum) bounded by? What does the face form from?
Primitive mouth is bounded by large forebrain (neural tube) cranially & cardiac bulge caudally. The face forms from the fronto-nasal process & the branchial (pharyngeal) arches (branchial arches have no respiratory function)
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When during embryonic development does the pharynx start to develop? How do the branchial (pharyngeal) arches develop & what do they contain?
4-5 week embryo. Arches: mesodermal proliferation, grow ventrally, meet in midline. Each arch contains structural components (cartilage/bone/connective tissue), an artery, a nerve & a muslce
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How many arches are there? What are the 1st & 2nd arches called?
There are 6 arches but only 4 visible - 5th arch degenerates & 6th is indistinct. First arch is the maxillary & mandibular process. Second arch is the hyoid arch
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What is between the arches? What is their embryonic origin?
Pouches internally lined with endoderm. Grooves/Clefts externally lined with ectoderm
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What nerve comes out of each branchial (pharyngeal) arch?
Each arch has its own nerve which innervates the associated muscle. If the muscle migrates it takes its nerve with it. 1st arch: CN 5. 2nd: CN 7. 3rd: CN 9. 4th: CN 10 (superior laryngeal). 6th: CN 10 (recurrent laryngeal)
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What do the branchial arch arteries do? What can go wrong?
Branchial arch arteries connect paired dorsal aortae to paired ventral aortae, thus they surround the primitive gut. Double aortic arch can form around trachea & oesophagus, pulsating blood can block airway or stop the swallowing of food
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What does each branchial (pharyngeal) arch cartilage form?
1: Meckel's cartilage, incus/malleus/maxillary process/sphenomandibular lig. 2nd: Reichert's cartilage, stapes/styloid process/stylohyoid lig/upper hyoid body. 3rd: majority body of hyoid. 4th: thyroid/laryngeal cartilages. 6th: cricoid cartilage
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Which muscles are associates to each branchial (pharyngeal) arch?
1: mastication, tensor tympanictensor tympani, tensor veli palatini, myelohyoid, anterior belly of digastric. 2: Facial expression, stapedius, stylohyoid, posterior belly of digastric. 3: stylopharyngeus. 4: cricothyroid. 6: intrinsic larynx muscles
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Which groove persists? What does it form?
Only 1st arch persists, forms external auditory meatus & part of eardrum. If 2nd/3rd/4th/6th arches overgrow, may more cysts or fistulae
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What does each branchial (pharyngeal) arch pouch form?
1: middle ear cavity, eustachian tube. 2: tonsillar crypts. 3: ventral wing descends into thorax->corpuscles/epithelial reticulum of thymus, dorsal wing forms inf parathyroid. 4: ventra wing->thyroid C cells, dorsal wing->sup parathyroid. 6: nothing!
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How does the thyroid form? What may development in adulthood?
Pouch of epithelium grows down to form foramen caecum (between 1st & 2nd arches) to thyroid cartilage, forming thyroglossal duct. In adults cysts, ectopic thyroid tissue & a pyramidal lobe may form
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When does the oropharyngeal membrane break down? What features do the different embryological orgins form?
Week 4. Ectoderm: lips, gums, teeth, enamel. Endoderm: tongue epithelium. Mesoderm: elevations in floor of pharynx
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How do the branchial (pharyngeal) arches contribute to the formation of the tongue?
1st: anterior 2/3rds tongue lateral lingual swellings, medial swelling (tuberculum impar), CN V lingual branch. 3rd(+2nd/4th): hypobranchial eminence, posterior 1/3rd tongue, CN IX. 6: tracheo-bronchial groove (laryngeal opening), CN X
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What does the face develop from?
5 elevations: the fronto-nasal process, paired maxillary processes & paired mandibular processes
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What does an ectodermal thickening give rise to?
Nasal placodes which ten form nasal pits with medial and lateral nasal elevations (medial & lateral)
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What do the naso-maxillary groove & medial nasal processes become?
Naso-maxillary groove (between lateral nasal elevation & maxillary process) develops into the naso-lacrimal duct. The medial nasal processes fuse to form intermaxillary segment which extends from primary palate & incisor region out to philtrum
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What happens during palate development?
At start, free communication between oral & nasal cavity (palate then separates these except posterior oro-/naso-pharynx). Primary palate: intermaxillary segment. Palatine shelves: maxillary processes (vertical, snap to horizontal very rapidly)
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How do a cleft lip & cleft palate form?
Cleft lip: failure of the are anterior to incisive foramen to fuse (mainly males). Cleft palate: failure of the area posterior to incisive foramen to fuse (mainly females)
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What is a distinctive feature of head/face abnormalities? Give examples.
Often mid-line fusion defects. Tongue: cleft, bifid, macroglossia (large), microglossia (small). Nose: microstomia, bifid
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Front

When during embryonic development does the pharynx start to develop? How do the branchial (pharyngeal) arches develop & what do they contain?

Back

4-5 week embryo. Arches: mesodermal proliferation, grow ventrally, meet in midline. Each arch contains structural components (cartilage/bone/connective tissue), an artery, a nerve & a muslce

Card 3

Front

How many arches are there? What are the 1st & 2nd arches called?

Back

Preview of the front of card 3

Card 4

Front

What is between the arches? What is their embryonic origin?

Back

Preview of the front of card 4

Card 5

Front

What nerve comes out of each branchial (pharyngeal) arch?

Back

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