05a: Pharyngeal Arches Flashcards by Nuna H

Pharyngeal arches have a core of (X) tissue, surrounded by (Y) tissue on outside and (Z) tissue on inside.

X = mesenchymal (paraxial and lateral plate mesoderm, neural crest cells)
Y = surface ectoderm
Z = endodermal epithelium

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T/F: neural crest cells migrate only into specific pharyngeal arches.

False - migrate into all of them

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First pharyngeal arch has (X) number of prominence(s) formed by (Y). List them.

X = 2
Y = migrating neural crest cells

Maxillary prominence
Mandibular prominence

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Which pharyngeal arch never forms?

Fifth

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Pharyngeal (X) partially separate the pharyngeal arches.

X = grooves (clefts) and pouches

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Pharyngeal grooves/clefts are composed of (X) tissue. Pharyngeal pouches are (external/internal) outpockets of (Y) tissue.

X = ectoderm
Internal;
Y = endoderm

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The pharyngeal membranes are (X)-layered structures of (Y) tissue.

X = 2
Y = ectoderm and endoderm

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Each pharyngeal arch contains which structures?

Cartilaginous skeletal and muscle component
CT component
Cranial nerve
Aortic arch artery

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T/F: All pharyngeal arches form simultaneously.

False - cranial to caudal fashion

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Face bones and skull form via (X) bone formation, meaning the bone develops in:

X = intramembranous

Develops in well vascularized mesenchyme

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Limbs/weight-bearing bones form via (X) bone formation, meaning the bone develops in:

X = endochondral (intra-cartilaginous)

Develops in pre-existing cartilage model

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Maxillary prominence of (X) pharyngeal arch has which cartilage? The cartilage has large contribution to (Y).

X = first;
Palatopterygoquadrate cartilage
Y = nothing (regresses; no remnants)

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Mandibular prominence of (X) pharyngeal arch has which cartilage? The prominence has large contribution to (Y).

X = first
Meckel’s cartilage;
Y = face

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Incus and Malleus form from (X), part of (Y) pharyngeal arch. They form via (Z) bone formation.

X = Meckel's cartilage (of mandibular prominence)
Y = first
Z = endochondral

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The perichondrium of Meckel’s cartilage forms:

Anterior ligament of malleus

2. Sphenomandibular ligament

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Maxillary prominence of (X) pharyngeal arch forms (Y) bones via (Z) process of bone formation.

X = first
Y = Temporal (squamous part), maxillary, zygomatic, palatine
Z = intramembranous

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Mandible forms from (X), part of (Y) pharyngeal arch. It form via (Z) bone formation.

X = mandibular prominence
Y = first
Z = intramembranous

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T/F: All bones formed from first pharyngeal arch mesenchyme via intramembranous ossification are derived from neural crest cells.

True

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Muscles of first pharyngeal arch, with innervation from (X) nerve.

X = trigeminal

Mastication muscles (4)
Tensor veli palatini
Tensor tympani
Anterior digastric
Mylohyoid

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Second pharyngeal arch has (X) cartilage that gives rise to:

X = Reichert’s

Stapes
Styloid process
Stylohyoid ligament
Lesser horn and upper body of hyoid

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Muscles of second pharyngeal arch, with innervation from (X) nerve.

X = facial

Facial expression muscles
Stapedius
Stylohyoid
Posterior digastric

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Third pharyngeal arch gives rise to (X) bones via (Y) process.

X = lower body and greater horn of hyoid
Y = endochondral ossification

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Muscles of third pharyngeal arch, with innervation from (X) nerve.

X = glossopharyngeal

Stylopharyngeus

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(X) and (Y) pharyngeal arches merge together and form (Z) via which ossification process?

X = fourth
Y = sixth
Z = laryngeal cartilages

No ossification process

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(X) cartilages of fourth and sixth pharyngeal arches are the only ones that form from (Y).

``` X = laryngeal; Y = lateral plate mesoderm ```

Muscles of fourth pharyngeal arch, with innervation from (X) nerve.

X = vagus (pharyngeal branch) 1. Soft palate muscles (except TVP) 2. Pharyngeal muscles (except stylopharyngeus)

Muscles of sixth pharyngeal arch, with innervation from (X) nerve.

X = vagus (recurrent laryngeal branch) 1. Intrinsic laryngeal muscles 2. Upper esophagus

First pharyngeal arch artery

Maxillary

Second pharyngeal arch artery

Stapedial and hyoid arteires

Third pharyngeal arch artery

Common carotid and proximal ICA/ECA

Fourth pharyngeal arch artery

Left: Aortic arch and left subclavian Right: Right subclavian

Sixth pharyngeal arch artery

Pulmonary arteries and ductus arteriosus

Pharyngeal pouches and clefts are (cranial/caudal) to same-numbered arch.

Caudal

(X) pharyngeal pouch forms stalk-like extension that expands toward (Y). What do the proximal and distal portions of the pouch form?

``` X = first Y = first pharyngeal cleft; ``` Distal: epithelial lining of tympanic cavity Proximal: narrows to form eustachian tube

Second pharyngeal pouch forms (X) in adult.

X = epithelium of palatine tonsil

Which specific tissue type proliferates in (X) to eventually form epithelium of palatine tonsil?

X = second pharyngeal pouch Epithelial lining (endoderm)

Third pharyngeal pouch forms (X) and (Y) regions. What does each become?

``` X = dorsal; Y = ventral ``` Dorsal: Inferior parathyroid (glandular epithelial cells) Ventral: Stroma of thymus

T/F: The glandular epithelial cells of parathyroid formed from pharyngeal pouch are the chief cells that secrete PTH.

True

Fourth pharyngeal pouch forms (X) and (Y) regions. What does each become?

``` X = dorsal; Y = ventral ``` Dorsal: Glandular epithelial cells of superior parathyroid Ventral: Ultimobranchial body (parafollicular cells in thyroid, surrounding thyroid follicles)

Only adult derivates of pharyngeal grooves.

First pharyngeal groove becomes external auditory meatus

Only adult derivates of pharyngeal membrane.

Tympanic membrane

Tongue develops as a result of proliferation of (X) tissue.

X = endoderm and mesenchyme (of pharyngeal floor)

Anterior (X) portion of tongue forms from swellings of mesenchyme beneath (Y) tissue of (Z) pharyngeal arch. List the swellings and star those that contribute to adult tongue.

``` X = 2/3 Y = endodermal epithelium Z = first ``` 2 lateral swellings* and 1 median swelling

Posterior (X) portion of tongue forms from swelling of mesenchyme beneath (Y) tissue of (Z) pharyngeal arch. This swelling is formally called:

``` X = 1/3 Y = endodermal epithelium Z = third and fourth ``` Hypobranchial/hypopharyngeal

During tongue development, the (X) arch(es) overgrow the (Y) arch and fuse with anterior portion at (Z) landmark.

``` X = third and fourth Y = second Z = terminal sulcus ```

Muscles of tongue arise from (X) that migrate forward to developing tongue. The (Y) nerve follows during migration to innervate (most/all) tongue muscles.

X = occipital somites Y = hypoglossal Most (not palatoglossus)

List tongue muscles. Star those innervated by common CN (X).

1. Palatoglossus 2. Styloglossus* 3. Hyoglossus* 4. Genioglossus*

General sensation to anterior 2/3 tongue provided by (X) branch of CN (Y).

``` X = lingual Y = 5 ```

Special (taste) sensation to anterior 2/3 tongue provided by (X) branch of CN (Y).

``` X = chorda tympani Y = 7 ```

General sensation to posterior 1/3 tongue provided by CN (X).

X = 9 and 10 (small portion)

Special (taste) sensation to posterior 1/3 tongue provided by CN (X).

X = 9

First endocrine gland to develop is (X). It's first seen as thickening of (Y) tissue on floor of (Z), between which pharyngeal arches?

``` X = thyroid gland Y = endoderm Z = upper pharynx ``` 1st and 2nd arches

T/F: The thyroid diverticulum forms epithelial lining of thyroid and glandular cells migrate in.

False - diverticulum forms glandular cells of thyroid

A mass of proliferating endoderm at foramen cecum of developing (X) will eventually migrate in which directions to become (Y)?

X = tongue Migrates caudally and ventrally; Y = thyroid gland

In adult, the foramen cecum is a remnant of (X) that persists as pit in (Y).

``` X = proximal thyroglossal duct Y = tongue (junction between anterior 2/3 and post 1/3) ```

T/F: The entire thyroid gland develops from thyroid diverticulum.

False - Parafollicular cells develop from ultimobranchial body (4th pharyngeal pouch)

A branchial cyst/fistula will be located (laterally/midline) along (X) border of (Y) muscle.

Laterally; X = anterior Y = SCM

A thyroglossal cyst is remnant of (X) and can be found (laterally/midline) at (Y).

X = thyroglossal duct; Midline; Y = any point of migration path of thyroid gland

Treacher Collins Syndrome is manifestation of a (X) syndrome that presents in which symptoms?

X = first arch 1. Malar (zygomatic) and mandibular hypoplasia 2. Ear/eye malformation

Robin Syndrome is manifestation of a (X) syndrome that presents in which symptoms?

X = first arch Triad complex (sequential): 1. Mandible hypoplasia 2. Posteriorly placed tongue 3. Cleft palate

DiGeorge Syndrome is result of failure of (X) to differentiate. It presents in which symptoms?

X = third and fourth pharyngeal pouch 1. Hypoplasia or absent thymus (immune deficiencies) 2. Absence of parathyroids 3. CV and facial abnormalities

The five facial prominences consist primarily of (X)-derived (Y) tissue. List these prominences.

``` X = neural crest cell Y = mesenchyme ``` 1. Maxillary (bilateral) 2. Mandibular (bilateral) 3. Frontonasal (midline)

Thickenings of surface ectoderm appear on both sides of frontonasal prominence and are called (X). These eventually invaginate to form (Y), surrounded by (Z).

``` X = nasal placodes Y = nasal pits Z = nasal prominences (medial and lateral) ```

The (medial/lateral) nasal prominence is separated from the maxillary prominence by (X).

Lateral; | X = nasolacrimal groove

(X) tissue on the floor of the nasolacrimal groove forms (Y) cord that eventually becomes (Z).

``` X = ectoderm; Y = epithelial Z = nasolacrimal duct ```

Maxillary prominences proliferate and grow (outward/inward).

Inward (toward each other)

As development continues, the medial nasal prominences will undergo (superficial/deep) compression and form (X). Which structures will develop from (X)?

Both superficial and deep; X = intermaxillary segment 1. Philtrum (of upper lip) 2. Premaxilla (with 4 incisor teeth) 3. Primary palate

T/F: The intermaxillary segment, once formed, is fused to maxillary prominences on each side of it.

True

Secondary palate forms which part(s) of adult palate?

Majority of hard palate and all of soft palate

Primary palate forms which part(s) of adult palate?

Small part of adult hard palate

Secondary palate forms by fusion of (X), which are internal projections of (Y).

``` X = lateral palatine shelves Y = maxillary prominences ```

During development of (primary/secondary) palate, which structure may initially be in the way of palatine shelf fusion?

Secondary; the tongue

The nasal septum develops as (upward/downward/medial) growth of which structure?

Downward; frontonasal prominence

In order for normal development of adult palate, which key fusions must occur?

Lateral palatine shelves with each other and with: 1. Primary palate 2. Nasal septum

Bone develops in (hard/soft) palate(s) by (X) ossification.

Hard; | X = intramembranous

Soft palate has (bone/cartilage) and muscle that migrates from (X).

Neither; | X = pharyngeal arches

The incisive fossa is a persistent (X) between (Y).

``` X = canal; Y = premaxilla and palatine parts of the maxilla ```

(X) is dividing landmark between anterior and posterior cleft deformities.

X = incisive fossa

T/F: Three categories of cleft palate/lip, depending on whether lip, palate, or both is/are affected.

True