Pharyngeal Arch Embyo

Question 1

Pharyngeal Arch

Parts and Germ Layers

Answer 1

Arch core made of Neural Crest cells (mesenchyme)
Can contain mesoderm as well

Pouch (internal) made of endoderm

Groove (external) made of ectoderm
aka Pharyngeal Cleft

Question 2

Mesoderm

Types and General Derivatives

Answer 2

Paraxial Mesoderm makes skeletal muscle primordia

Lateral Plate Mesoderm makes angioblasts

Question 3

Neural Crest Cell

General Derivatives

Answer 3

Makes Connective Tissue (cartilage), Smooth Muscle and Dermis

Question 4

First Pharyngeal Arch Derivatives

Cartilages (5) and Muscle

Answer 4

Meckel’s Cartilage
Ventral makes primitive mandible
Dorsal makes malleus, incus
Perichondrium makes Anterior L. of malleus and Sphenomandibular L

Makes muscles of mastication

Question 5

First Pharyngeal Arch Innervation

Answer 5

Innervated by V2 and V3 of Trigeminal N

Question 6

Second Pharyngeal Arch Derivatives

Cartilages (4) and Muscles (2)

Answer 6

Riechert’s Cartilage
Dorsal makes Stapes and Temporal Styloid Process
Ventral makes Lesser horn of hyoid
Perichondrium makes Stylohyoid L

Stapedius M
Muscles of facial expression

Question 7

Second Pharyngeal Arch Innervation

Answer 7

Innervated by Facial N

Question 8

Third Pharyngeal Arch Derivatives

Cartilages (2), Muscle, Blood Vessels

Answer 8

Makes Greater Horn of Hyoid
Makes Hypopharyngeal eminence
(which makes hyoid body)

Makes Stylopharyngeus M

Makes Common and Internal Carotid As

Question 9

Third Pharyngeal Arch Innervation

Answer 9

Innervated by Glossopharyngeal N

Question 10

Fourth Pharyngeal Arch Derivatives

Cartilages and Muscles (3)

Answer 10

Fuses with PA6 to form Laryngeal cartilages

Cricothyroid M
Levator Veli Palatini M
Pharyngeal Constrictor Ms

Question 11

Sixth Pharyngeal Arch Derivatives

Cartilages and Muscles

Answer 11

Fuses with PA4 to form Laryngeal cartilages

Intrinsic Larynx Ms

Question 12

Fourth/Sixth Pharyngeal Arch Innervation

Answer 12

Both innervated by Vagus N and Recurrent Laryngeal N

Question 13

Endoderm

General Derivatives

Answer 13

Makes pharyngeal pouches and their derivatives

Question 14

Ectoderm General Derivatives

Answer 14

Makes pharyngeal grooves and their derivatives

Question 15

First Pharyngeal Pouch Derivatives (4)

Answer 15

Makes Tubotympanic recess
Recess forms Tympanic cavity and mastoid antrum
Recess forms pharyngotympanic tube

Question 16

Second Pharyngeal Pouch

Derivatives (3) with Associated Germ Layers

Answer 16

Forms tonislar sinus
Makes tonsilar crypts from Endoderm
Makes tonsils from Neural Crest Cells

Question 17

Third Pharyngeal Pouch

Parts (2) and Derivatives

Answer 17

Dorsal makes Inferior Parathyroid Glands

Ventral makes Thymus

Question 18

Fourth Pharyngeal Pouch Derivative

Answer 18

Dorsal part makes Superior Parathyroid Glands

Question 19

First Pharyngeal Groove Derivative

Answer 19

Makes External Acoustic Meatus

Question 20

Ultimopharyngeal Body

Derivative with Germ Layer

Answer 20

Forms thyroid Parafollicular Cells from Neural Crest cells

Question 21

Thyroid Development

Germ Layer and Migration

Answer 21

Thyroid primordium formed in pharynx from endoderm

Migrates down thyroglossal duct to final position

Question 22

First Pharyngeal Arch Syndrome

Cause and Effects

Answer 22

Caused by neural crest cell migration issues

Leads to malformation of eyes, ears, mandible and palate

Question 23

Treacher-Collins Syndrome

Cause and Effects

Answer 23

Mutation in TCOF1 gene that leads to cranial NCC apoptosis

Causes malar hypoplasia and eye/ear defects

Question 24

Pierre Robin Sequence

Answer 24

Causes micrognathia (mandibular hypoplasia) that leads to bilateral cleft palate