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COM Neuroendocrine > Embryology of the Pharyngeal Apparatus > Flashcards

Embryology of the Pharyngeal Apparatus Flashcards

1
Q

Pharyngeal arch development

A

Develop in early 4th week as neural crest cells, migrate into the future head and neck
1st pair of arches- primordial jaws, appear lateral to developing pharynx
Arches 2-4 soon appear as ridges on each side of the future head and neck regions
5th and 6th arches- rudimentary and not visible on surface of embryo

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2
Q

Arches consists of

A

Core of mesoderm with ectoderm covering and endoderm internally

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3
Q

Mesenchyme is derived from ___ while head mesoderm forms ___

A

Mesenchyme derived from migrating neural crest cells and forms all CT in the head
Head mesoderm forms paraxial mesoderm which populates each arch to form musculature

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4
Q

Pharyngeal arch functions

A

Support the lateral wall of the primordial pharynx

Give rise to prominences of tissue that contribute to craniofacial development

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5
Q

What forms the endothelium

A

Lateral plate mesoderm gives rise to angioblasts that differentiate into endothelium

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6
Q

What forms the extraocular musculature

A

Prechordal plate mesoderm

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7
Q

What plays an important role in regulating the development of the arches

A

Pharyngeal endoderm!!

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8
Q

Structures contained in pharyngeal arches

A

Cartilaginous rod- forms skeletal elements
Muscular component- forms head/neck muscles
Cranial nerves
Arch artery- derived from truncus arteriosus/aortic sac of primordial heart, enters dorsal aorta

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9
Q

Meckels cartilage

A

Cartilage of arch 1
Dorsal portion forms malleus and incus
Perichondrium forms anterior ligament of malleus and sphenomandibular ligament
Ventral parts form primordium of mandible

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10
Q

Riecherts cartilage

A

Cartilage of arch 2
Dorsal region contributes to stapes and styloid process of temporal bone
Perichondrium forms stylohyoid ligament
Ventral end ossifies and forms lesser cornu/horn of hyoid bone

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11
Q

Third arch cartilage

A

Forms greater cornu of hyoid bone

Body of hyoid is formed by hypopharyngeal eminence- a prominence in floor of embryonic pharynx from 3/4 arches

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12
Q

4th arch cartilage

A

Laryngeal cartilages including epiglottis (NCC derived)

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13
Q

6th arch cartilage

A

Laryngeal cartilages, but origin is uncertain

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14
Q

What forms musculature of pharyngeal arch

A

Paraxial mesoderm and prechordal plate (ocular muscles)

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15
Q

First arch muscles and derived from what

A 
Muscles of mastication
Mylohyoid
Anterior belly of digastric
Tensor veli palatini
Tensor tympani
Head mesoderm
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16
Q

Second arch muscles and derived from what

A

Stapedius and muscles of facial expression
Posterior belly of digastric
Stylohyoid
Head mesoderm

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17
Q

Third arch muscles and derived from what

A

Stylopharyngeus

Head mesoderm

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18
Q

Fourth arch muscles and derived from what

A

Cricothyroid
Levator veli palatine
Constrictors of pharynx
Occipital somites

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19
Q

Sixth arch muscles and derived from what

A

Intrinsic muscles of larynx

Occipital somites

20
Q

Trigeminal nerve supplies

A

First arch
Principle sensory for head and neck
Motor nerve for mastication muscles

21
Q

Facial nerve supplies

A

Second arch

Muscles of facial expression

22
Q

Glossopharyngeal nerve supplies

A

Third arch

Stylopharyngeus

23
Q

Vagus nerve supplies

A

4th-6th arches
4th supplied by superior laryngeal branch and its recurrent laryngeal branch
Constrictors of pharynx and intrinsic muscles of larynx supplied by vagus

24
Q

Arch artery

A

5 pairs of arteries forming basket like structure, each arise from aortic sac and connect to dorsal aorta

25
Q

First pharyngeal groove

A

Forms external acoustic meatus
Pharyngeal grooves are externally located b/w pharyngeal arches
Grooves consist of ectoderm

26
Q

Grooves 2-4 lie where

A

Cervical sinus

27
Q

Pharyngeal pouches

A

Line the pharynx internally

28
Q

Cervical cysts

A

Branchial abnormality
Remnants of cervical sinus and/or 2nd groove
Persist and form a slowly enlarging, painless, free lying cyst in the neck, inferior to angle of the mandible
Accumulation of fluid and cellular debris derived from desquamation of their epithelial linings

29
Q

Cervical sinus

A

Branchial abnormality
Failure of the 2nd pharyngeal arch groove and cervical sinus to obliterate
Detected due to discharge of mucus
Typically bilateral and commonly associated with auricular sinuses

30
Q

Cervical fistula

A

Branchial abnormality
Abnormal canal that opens into the tonsillar sinus and externally in the side of the neck
Persistence of parts of 2nd groove/pouch

31
Q

First pharyngeal membrane forms

A

Pharyngeal membranes formed where pouch endoderm contacts groove ectoderm
Pharyngeal membranes are quickly infiltrated by mesenchyme
Forms tympanic membrane

32
Q

First pharyngeal pouch forms

A

Tubotympanic recess- tympanic cavity and mastoid antrum
Pharyngotympanic tube
Endoderm contacts first pharyngeal groove and contributes to tympanic membrane
Pouches are endoderm

33
Q

Second pharyngeal pouch forms

A

Portion of it forms tonsillar sinus
Endoderm proliferates and forms tonsillar epithelium
Mesenchyme differentiates into lymphoid nodules of palatine tonsil

34
Q

Third pharyngeal pouch forms

A

Dorsal portion differentiates into inferior parathyroid gland
Ventral portions form thymus
Caudally migrate due to growth of brain/cardiac regions

35
Q

Fourth pharyngeal pouch forms

A

Dorsal portion forms superior parathyroid glands

Forms ultimobranchial body which fuses with thyroid gland and gives rise to parafollicular cells

36
Q

Thymus development

A

Develops from PA3 endoderm, comprised of epithelial cords

37
Q

Function of epithelial cords in thymus development

A

Grow into surrounding mesenchyme to form thymic lobules
Become arranged around a central point to form thymic corpuscles
Form an epithelial reticulum for housing lymphocytes

38
Q

Thyroid gland development

A

First endocrine gland to develop ~24 days
Forms a median endodermal thickening in floor of primordial pharynx
Descends in the neck with tongue growth and passes ventral to developing hyoid bone and laryngeal cartilages
Connected to tongue by thyroglossal duct

39
Q

First pharyngeal arch syndrome

A

Abnormal development of components of PA1
Malformation of eyes, ears, mandible, palate
Multiple different manifestations and causes, each with different names discussed in next cards
Results from insufficient migration of NCC into 1st arch during 4th week

40
Q

Treacher-Collins syndrome (mandibulofacial dysostosis)

A

Malar hypoplasia w/down slanting palpebral fissures, defects of lower eyelids, deformed external ears and sometimes middle/internal ears
Autosomal dominant
Mutation in gene that encodes for TREACLE protein, involved in ribosome biogenesis
Truncation mutation

41
Q

Pierre Robin sequence

A

Occurs de novo
Associated with hypoplasia of mandible, cleft palate and defects in eyes and ears
Initiating defect is small mandible (micrognathia), results in posterior displacement of the tongue and obstruction of full closure of the palate which results in bilateral cleft palate

42
Q

Thyroid hemiagenesis

A

Unilateral failure of formation, left lobe is more commonly absent
Mutations in receptor for TSH is usually involved

43
Q

DiGeorge syndrome

A

Breakdown of signaling from PA endoderm to NCC
Agenesis of thymus and parathyroid glands
Congenital hypoparathyroidism
Shortened philtrum of upper lip, low set and notched ears
Nasal clefts, thyroid hypoplasia
Cardiac abnormalities

44
Q

Arch arteries for PA1-PA3

A

PA1- terminal branch of maxillary artery
PA2- stapedial artery (embryonic), caroticotympanic artery (adult)
PA3- common carotid artery, root of internal carotid

45
Q

Arch arteries for PA4

A

Arch of aorta- left side
Right subclavian artery- right side
Original sprouts of pulmonary arteries

46
Q

Arch arteries for PA6

A

Ductus arteriosus

Roots of definitive pulmonary arteries

COM Neuroendocrine (46 decks)

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