Pharyngeal arches 1/14/17 Flashcards by Cutler Frandsen

What are the two general phases of pharyngeal arch development?

Formation of pharyngeal system

- Development of pharyngeal derivatives

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What is a cysts?

-Sealed cavity filled with air, pus, fluid…..

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What is a sinus?

-Cavity within a tissue, can open externally

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What is a fistula?

-Abnormal connection between 2 structures

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What does the pharyngeal apparatus consist of?

Pharyngeal arches
pharyngeal grooves
pharyngeal pouches
pharyngeal membrane

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How many pharyngeal arches are there?

1-6 but 5th doesn’t form

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When do the pharyngeal arches emerge?

-Neural tube closure around 4 weeks development

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What is another name for the 1st pharyngeal arch?

-Mandibular atch

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What is another name for the 2nd pharyngeal arch?

-Hyoid arch

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What 2 prominences do you find the the 1st pharyngeal arch?

Maxillary

- Mandibular

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T/F

The pharyngeal arches contain all of the germ layers

True

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What germ layer forms the pouch?

-Endoderm

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What germ layer forms the cleft?

-Ectoderm

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What germ layer forms the arch?

-Mesoderm

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T/F

Early arches are not continuous with each other

False

They are continuous

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Where is the floor of your gut and pharynx derived from?

-Endodermal

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What breaks down during week 4 that connects the stomodeum (mouth) to the primitive gut?

-Oropharyngeal membrane (buccopharyngeal)

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What are the four components of each of the pharyngeal arches?

Aortic arch
Cartilaginous rod
Muscular component
nerve

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What is the aortic arch component of the pharyngeal arch?

-An artery that arises from the truncus arteriosus of the primordial heart

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What is the cartilaginous rod component of the pharyngeal arch?

-It form the skeleton of the arch

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What is the muscular component of the components of pharyngeal arches?

-It differentiates into muscles in the head and neck

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What is the nerve component of the pharyngeal arches?

-Supplies the mucosa and muscles derived from the arch

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What do the components of the pharyngeal arches come from?

-Mesoderm (mesenchyme)

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Where do the aortic arches arise from?

-Mesoderm

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Where do the aortic arches bridge between?

-Truncus arteriosus and the dorsal aorta

What do the aortic arches 1 and 2 make?

- Maxillary - External carotid - Stapedial

What do the aortic arches 3,4, and 6 make?

- Common carotid - Internal carotid - Aortic - Subclavian - Pulmonary

What muscles come from arch 1?

-Muscles of mastication

What muscles come from arch 2?

-Muscles of facial expression

What muscles from from arch 3?

-Stylopharyngeus

What muscles come from arch 4?

-Pharyngeal constrictors

What muscles come from arch 6?

-Laryngeal muscles

What do the nerves from the pharyngeal arches come from?

- Neural crest | - Ectodermal

What CN comes from arch 1?

-Trigeminal

What CN comes from arch 2?

-Facial nerve

What CN comes from arch 3?

-Glossopharyngeal

What CN comes from 4-6?

- Vagus (4th arch) | - Recurrent laryngeal (6th arch)

What skeleton parts come from arch 1?

- Meckel's cartilage - Maxilla - Mandible - Malleus - incus

What skeletal parts come from arch 2?

- Stapes - Styloid process - Less horn and upper portion of hyoid

What skeletal parts come from arch 3?

-Greater horn and lower portion of body of hyoid

What does the mandibular process form?

- Lower lip - Lower face - Lower cheek regions - Chin - Mandible - Body of the tongue

What does the maxillary process form?

- Midface - upper cheek - upper lip - secondary palate - maxilla - zygomatic bone

Where arch does the mandibular process and maxillary process come from?

-Arch 1

What is the most common failure of first arch syndrome?

-Failure of the Neural crest to properly migrate

What is Treacher Collins syndrome?

- First arch syndrome - Hypoplasia of arch derived facial bones - ear deformations - Cleft palate

How many paris of pharyngeal grooves are there?

What cleft is the only one normally not obliterated in development?

Cleft 1

What does pharyngeal cleft 1 give rise to?

-External auditory meatus

If the pharyngeal clefts or grooves don't completely obliterate what occurs?

-Usually benign sinuses or cysts

What are two types of branchial sinuses, cysts, and fistulas?

- Lateral cervical | - Internal branchial

What is a lateral cervical pharyngeal cleft anomaly?

-Open externally (neck) failure of second groove or cervical sinus to obliterate

What does the first pharyngeal pouch give rise to?

-Middle ear

What does the proximal part of the first pharyngeal pouch give rise to?

-Eustachian tube

What does the second pharyngeal pouch give rise to?

-Lining of the crypts in the palatine tonsils

What are the tonsils composed mostly of?

-Mesoderm

What does the third pharyngeal pouch give rise to?

- Inferior parathyroid gland | - Thymus

What wing from the third pharyngeal pouch forms the inferior parathyroid glands?

-Dorsal wing

What does the ventral wing of the third pharyngeal pouch give rise to?

-Thymus

What does the fourth pharyngeal pouch give rise to?

- Superior parathyroid gland | - Ultimobranchial body

What does the dorsal wing give rise to in the fourth pharyngeal pouch?

-Superior parathyroid glands

What does the ventral wing give rise to in the fourth pharyngeal pouch?

-Ultimocranchial

T/F | Primordia originate at mature function sites

False | They need to migrate

What does PTH do to Ca2+ levels?

-Increases Ca 2+ levels

What does Calcitonin do to Ca2+ levels?

-Lower Ca2+ levels

What is the most common syndrome of a pharyngeal pouch ?

-DiGeorge Syndrome

What causes DiGeorge Syndrome?

-Failure of 3rd and 4th pouches to differentiate into thymus and parathyroid

What Deficits do you see in DiGeorge Syndrome?

``` -Catch 22 Cardiac abnormality Abnormal facies Thymic aplasia Cleft palate Hpocalcemia ```

What are the pharyngeal membranes?

-Form where the epithelia of the grooves and pouches approach each other

Where do you find the tympanic pharyngeal membrane?

-Derived from layer between 1st cleft and 1st pouch

What is the importance of the Hox genes?

-Involved in bodily segmentation

Where do the neural crest cells migrate to?

-Pharyngeal arches

What controls/tells the neural crest cells where do migrate?

-Hox genes

If you lose a Hox gene (Anterior posterior axis) what happens?

-It can lead to duplication of other structures

What genes are interarch patterning genes dealing with proximal from distal genes?

Dlx Genes

Where does the tongue develop from?

-Floor of the arches

What part of the tongue does arch 1 form?

-Anterior 2/3 of tongue epithelium

What part of the tongue does arch 2 form?

-Gets covered up as arch 3 grows

What part of the tongue does arch 3 form?

-Most of the remaining 1/3 of tongue epithelium

What part of the tongue does arch 4 from?

-Bit of tongue at the very back of the throat

In week 4 arch one form a median swelling called what?

-Median tongue bud

In week 5 arch 1 forms lateral swellings called what?

-Distal tongue buds

What do the median tongue buds and distal tongue buds become?

-Anterior 2/3 of tongue

In week 4 what does Arch 2 form in the tongue?

-Copula

In weeks 5-6 what is arch 2 overgrown by?

-Hypopharyngeal eminence from arches 3 and 4

What gives rise to tongue muslces?

-Occipital somites

T/F | The tongue muscles are pharyngeal in origin

False | Except palatoglossus

What is the dividing line between the oral tongue and pharyngeal tongue?

-Terminal sulcus

What is the foramen cecum on the tongue the site of?

-Thyroid primordium

Why are tongue muscles innervated by CN XII when the anterior 2/3 is derived from pharyngeal arch 1?

-Tongue muscles don't come from the arches

Where does the thyroid develop from?

-Endodermal diverticulum just posterior to floor of the 1st arch

Is the development of the thyroid bilateral?

What are some thyroid anomalies?

-Thyroglossal duct cysts and sinuses

Where does the development of the pituitary gland occur?

-Forms from upward invagination of the oral ectoderm in the stomodeum (Rathke's pouch)

How do you know whether a sinus/cyst is thyroglossal or cervical?

-Thyroglossal will be found on the midline

What forms the neurohypophysis?

-Develops from the developing brain (neural ectoderm)

What forms the adenohypophysis?

-Develops from the stomodeum roof (oral ectoderm)