Lecture 10- Embryology of the head and neck Flashcards
Label
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how many pharangeal arches
- 5 (1 to 6 (5th doesn’t form in humans))
- 1st arch is the largest- get progressively smaller
- Each arch associated with
artery, cranial nerve and cartilage
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what forms the ehad and neck region
frontal nasal prominence and pharangeal arches
- (over ½ of embryo at week 4)
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structure of a pharangeal arch
- Structure
- Core= mesenchyme
- Outer covering= ectoderm (epidermic of skin)
- Inner covering= endoderm in the pharynx
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helpful images to help get your head around the pharangeal arches
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Development of pharyngeal region
- Segmental
- Each arch (body segment) has a neurovascular plan
- Develops muscles and skeletal elements and associated with particular nerve
Development of the gut tube in the pharynx
- Endoderm tube
- Modification
- Glandular development
- Parathyroids, thymus, palatine tonsils, thyroid
Grooves and clefts
Simultaneously, a number of outpocketings appear on the lateral wall of the pharynx – the pharyngeal pouches. The pouches separate the arches on the internal (endodermal) surface whilst the clefts separate the arches on the external (ectodermal) surface.
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Clefts=
grooves on the outside
what happens to pharangeal clefts during development
Most clefts will obliterate (2ND PHARNGEAL ARCH grows down to cover THE other CLEFTS)
1st cleft is the only one to persist
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failure to obliterate clefts gives rise to
branchial cysts and fistual
branchial cysts
- Branchial cysts (fluid filled remnant of 1st pharyngeal cleft) or branchial fistulae (opening of fluid filled remnant into neck) can occur if there are remnants
- Key landmark for looking for these abnormalities = SCM
- E.g. anterior border= branchial cyst
what does the 1st cleft that persists become
external auditory meatus
Pouches
- First one- ET and middle ear
- Glandular tissue e.g. palatine tonsil, PT and thymus, thyroid etcccccc
Each arch associated with a
CN, cartilaginous structures, blood vessels and muscles
gross anatomy of Ph A1 (pharangeal arch 1)
Made up of 2 bumps- first bump (dorsal- maxillary), second bump (ventral- mandibular)
Maxillary prominence
- Dorsal portion
- Becomes future maxilla zygomatic bone and temporal bone
- Associated with maxillary cartilage- gives rise to incus
Mandibular prominence
- Ventral portion
- Becomes future mandible
- Associated with Meckel’s cartilage
summarise Ph A1 cartilage
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Maxillary cartilage (first bump)
- Gives rise to incus
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Meckel’s cartilage (second bump)
- Mandible cartilage
- Gives rise to malleus
- Mandible cartilage
arterial supply of Ph A1
- Becomes the terminal portion of the maxillary artery- branch of external carotid
CN associated with Ph A1
- CN 5- trigeminal
- Sensory filed
- Skin on face
- Lining of mouth and nose
- General sensation
- Anterior 2/3 of tongue
- Sensory filed
Ph A1 Associated muscles
- Muscles of mastication
- Mylohyoid
- Anterior belly of digastric
- Tensor veli palatani
- Tensor tympani
summarise Ph A2 cartilage
- Reichert’s
- Stapes
- Styloid process
- Stylohyoid ligament
- Upper part of hyoid
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arterial supply of Ph A2
- Stapedial artery- regresses before birth
- Hyoid artery- gives rise to corticotympanic artery in adult
CN associated with Ph A2
- CN 7 – facial nerve
- Special sensory- taste of anterior 2/3 of tongue (via chorda tympani)
Ph A2 associated muscles
- Muscles of facial expression
- Stapedius (nerve to stapedius)
- Stylohyoid
- Platysma
- Posterior belly of digastric
Summarise Ph A3 cartilage
- Remainder of hyoid
arterial suppy of Ph A3
- Internal carotid
CN associated with Ph A3
- CN 9- glossopharyngeal
- Sensory function- taste and general sensation to posterior 1/3rd of tongue
Ph A3 associated muscles
Stylopharngeus
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Ph A4 Cartilage
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- Cartilage of the larynx
- Thyroid cartilage
- Corniculate cartilage
- Cuneiform cartilage
Ph A4 arterial supply
- Arch of aorta (L) and subclavian artery(R)
Ph A4 CN
- CN 10- Vagus (superior laryngeal branch)
Ph A4 associated muscles
- Pharyngeal constrictors
- Cricothyroid
- Levator palatini
Ph A6 Cartilage
Cartilage of the larynx
Ph A6 Arterial supply
- Pulmonary arch
- Pulmonary arteries (R)
- Ductus arteriosus (L)
Ph A6 associated CN
- CN 10- Vagus
- Recurrent laryngeal branch
- Sensory field
- Taste sensation from epiglottis and pharynx
- General sensation in pharynx, larynx, oesophagus, tympanic membrane, externa auditory meatus and part of the external ear
- Gag reflex
- Parasympathetic innervation to viscera
- Sensory field
- Recurrent laryngeal branch
Ph A6 associated muscles
- Pharyngeal constrictors
- Intrinsic muscle of the larynx (except cricothyroid)
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pharangeal pouch associated with 1st arch derivatives
eustachian tube and middle ear cavity
pharangeal pouch associated with 2st arch derivatives
lining of the palatine tonsils
pharangeal pouch associated with 3rd arch derivatives
- dorsal- inferior parathyroid gland
- ventral- thymus
pharangeal pouch associated with 4th arch derivatives
dorsal- supeiror parathyroid glands
ventral- ultimobranchial body (C cells)
What does the 1st pharyngeal cleft form?
External auditory meatus
Which pharyngeal arch contributes to Reichert’s cartilage?
- 2nd
Which of the following is NOT associated with the 4th pharyngeal arch?
- Aortic arch
- Laryngeal cartilages
- Superior laryngeal nerve
- Recurrent laryngeal nerve
- Aortic arch
- Laryngeal cartilages
- Superior laryngeal nerve
- Recurrent laryngeal nerve
summary of the cartilages associated with each arch
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1.
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development of head and neck
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B
CN associated with arches 1-6
to feel good so regularly
arch 1: CN V (trigeminal)
arch 2: CN VII (facial)
arch 3: CN IX (glossopharyngeal)
arch 4: CN X (superior laryngeal branch of the vagus)
arch 6: CN X (recurrent laryngeal branch of the vagus)