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Neuro Endocrine > Embryology of the Pharyngeal apparatus > Flashcards

Embryology of the Pharyngeal apparatus Flashcards

1
Q

What does the Pharyngeal Apparatus give rise to

A

consists of pharyngeal arches (PA), pouches, grooves (clefts) and membranes

Contribute to the formation of nasal cavities, mouth, larynx, pharynx, and neck

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2
Q

When do the Pharyngeal arches develop and where?

A

4th week as neural crest cells migrate into the future head and neck

1st pair of arches (primodial jaws) appear lateral to developing larynx

Arches 2-4 appear as ridges on each side of future neck and head regions

5/6 arches are rudimentary and not visible

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3
Q

What does each pharyngeal arch consists of embrylogically?

A

core of mesoderm and mesenchyme

covered externally by Ectoderm

and covered internally by endoderm

(mesenchyme is derived from migratory NCC)
(head mesoderm forms from paraxial mesoderm)

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4
Q

What do the Pharyngeal arches give rise to and function?

A

Support the lateral walls of the primordial pharynx

give rise to the prominences of tissue that contribute to craniofacial development

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5
Q

What are the 4 embryological Pharyngeal arch components and what do they give rise to

A

NCC derived Mesenchyme: forms all the connective tissue in the head including the dermis and smooth muscle

Paraxial Mesoderm: Populates each arch to form Pharyngeal arch musculature

Lateral Plate Mesoderm: Angioblasts that differentiate into the endothelium

Prechordal Plate Mesoderm: Extraocular musculature

Pharyngeal endoderm plays an essential role inregulating the development of the arches

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6
Q

The pharyngeal arch contains 4 st ructures

A

Cartilaginous rod: forms the skeletal element

Muscular component: differentiates into the muscles in the head and neck

Cranial Nerves: sensory and or motor components

Arch Artery: arising from the truncus arteriosus of primodial heart, it passes around the primordial pharynx to enter the dorsal aorta

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7
Q

Pharyngeal Arch 1: Cartilage

A

Meckels cartilage

Dorsal portion forms the malleus and incus

Perichondrium: makes anterior ligament of malleus and sphenomandibular ligament

Ventral parts: primordium (model) of the mandible the bone will form laterally to meckels

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8
Q

Pharyngeal Arch 2: Cartilage

A

Riecherts Cartilage

Dorsal region contributes to the stapes and styloid process of the temporal bone

Perichondrium: stylohyoid ligament

ventral end ossifies and forms the lesser cornu/horn of hyoid bone

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9
Q

Pharyngeal Arch 3: cartilage

A

Ossifies and forms the greater cornu of hyoid bone

Body of the Hyoid bone is formed by the hypopharyngeal eminence via PA3 and PA4

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10
Q

Pharyngeal Arch 4 cartilages

A

laryngeal cartilages including the epiglottis (NCC derived

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11
Q

Pharyngeal Arch 6 cartilages

A

Laryngeal cartilages, but orgin is uncertain

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12
Q

Pharyngeal Arch 1 Muscles

A

Muscles of Mastication (CN V)

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13
Q

Pharyngeal Arch 2 Muscles

A

Stapedius and muscles of facial expression (CN VII))

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14
Q

Pharyngeal Arch 3 Muscles

A

Stylopharyngeus Muscle (CN IX)

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15
Q

Pharyngeal Arch 4 Muscles

A

Cricothyroid, levator veli palatini, constrictors of pharynx (CN X)

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16
Q

Pharyngeal Arch 6 muscles

A

Intrinsic muscles of the larynx (CN X)

17
Q

What nerve supplies the 1st PA

A

Trigeminal Nerve: supplies the first arch

principle sensory to the head and neck

Motor nerve for the muscles of mastication

18
Q

What nerve supplies the 2nd PA

A

Facial Nerve which will supply the muscles of facial expression

19
Q

What nerve supplies the 3rd PA

A

Glossopharyngeal nerve (CN IX)

also supplies the stylopharyngeus m

20
Q

What nerve supplies the 4th-6th Arch

A

Vagus Nerve (CN X)

4th arch supplied by the superior laryngeal branch of CN X and its recurrent laryngeal branch

also supplies the constrictors of pharynx and intrinsic muscles of the larynx

21
Q

what do the arch arteries arise from?

A

5 pairs of arteries arise from the Aortic sac

it is a basket like structure arising from the dorsal aorta that gets remodeled into the great arteries of the thorax and head/neck

arteries arising from the 1st -3rd aortic arch are bilateral and 4th and 6th are asymmetrical

come from mesoderm

22
Q

What are Pharyngeal Grooves and what do they give rise to

A

Located between the pharyngeal arches

covered with ectoderm

first groove gives rise to the external acoustic meatus

grooves 2-4 lie in the cervical sinus and these will eventually go away

23
Q

What are Pharyngeal pouches

A

Pharyngeal endoderm lines the pharynx internally and create pharyngeal pouches

5 pairs of pouches that develop between the craniocaudal sequence between the arches

24
Q

Cervical Cysts branchial anomaly

A

Remnants of cervical sinus and or the 2nd groove

persist to form a slowly enlarging painless free lying cyst in the neck inferior to the angle of the mandible

Accumulation of fluid and cellular debris derived from desquamation of their epithelial linings

25
Q

Cervical sinus branchial anomaly

A

failure of the 2nd PA groove and cervical sinus to obliterate

detected due to discharge of mucus

typically bilateral and commonly associated with auricular sinuses

26
Q

Cervical Fistula branchial anomaly

A

Abnormal canal that opens into the tonsillar sinus and externally in the side of the neck

persistence of parts of 2nd groove and pouch

27
Q

What is the pharyngeal membrane, and what gives rise from the pharyngeal membrane

A

form where the pouch endoderm contacts ectoderm of the pharyngeal

quickly infiltrated by mesenchyme

1st pharyngeal membrane plus the intervening mesenchyme forms the tympanic membrane

28
Q

What does the first pouch form

A

expands into the tubotympanic recess creating the tympanic cavity and the mastoid antrum

elongates to form pharyngotympanic tube

29
Q

What does the 2nd pouch form

A

Portion of the tonsillar sinus

Endoderm proliferates to form the tonsillar epithelium

mesenchyme differentiates to form the lymphoid nodules of palatine tonsil

30
Q

What does the 3rd pouch form

A

Dorsal portion forms the inferior parathyroid gland

ventral portion forms the thymus (this will caudally migrate due to growth of brain and cardiac regions

31
Q

What does the 4th pouch form

A

Dorsal portion differentiates into the superior parathyroid glands

Ultimobranchial body fuses with the thyroid gland to give rise to the para follicular cells

(this will stay put as the contents of the third pouch will migrate inferiorly past)

32
Q

Thymus development, and the function of the three epithelial cords

A

Thymic primordium develops from PA3 endoderm composed of epithelial cords

these function:
grow into surrounding mesenchyme- thymic lobules

Become arranged around a central point- forming thymic corpscule

Form an epithelial reticulum for housing lymphocytes

growth is still very active during childhood

33
Q

Thyroid Gland Development

A

First endocrine gland to develop - thyroid primordium

Forms from 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 a narrow tube- thyroglossal duct but this will then disintegrate

34
Q

First Arch Syndromes

A

abnormal development of the first arch

malformation of the eyes, ears, mandible, and palate

results from insufficient migration of NCC into the 1st arch during 4th week

35
Q

Treacher-Collins Syndrome (mandibulofacial dysostosis

A

Malar hypoplasia with down slanting palpebral fissures, defects of lower eyelids, deformed external ears, and sometimes middle and internal ears

Autosomal dominant disorder due to mutations in Treacher Collins Franceschetti syndrome 1 gene (TCOF 1)

encodes for the protein TREACLE involved in ribosome biogenesis

truncated in TCS leading to increased apoptosis of Cranial NCC

36
Q

Pierre Robin sequence

A

hypoplasia of the mandible, cleft palate, and defects of the eyes and ears

initiating defect is a small mandible (micrognathia) which results in posterior displacement of the tongue and obstruction of full closure of the palate resulting in bilateral cleft palate

37
Q

Agenesis of thyroid gland

A

absence of a thyroid gland or one of its lobes

38
Q

Thyroid hemigenesis

A

unilateral failure of formation usually the left lobe

mutations in the receptor for the thyroid stimulating hormone are likely involved

39
Q

DiGeorge Syndrome

A

Breakdown of signaling from the PA endoderm to NCC

agenesis of the thymus and the parathyroid glands

congenital hypothyroidism

shortened philitrum of upper lip, low set and notched ears

nasal clefts, thyroid hypoplasia

cardiac abnormalities due to defects of the aortic arch

Neuro Endocrine (20 decks)

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