Embryology of the Head and Neck: the Pharyngeal Apparatus (Branchial Apparatus)

Question 1

Define Branchial (Pharyngeal) ARCHES (‘gill arches’)

Answer 1

bulges off the bugle off the face and the neck, if we were fish they form the gills, they come from the head folding stage, there a four we can see on the outside and 2 vestigeal ones on the inside, comes from ectoderm (from NC) and head mesoderm

Question 2

What is Branchial arch mesenchyme made of?

Answer 2

head mesoderm

Question 3

Define Branchial (Pharyngeal) GROOVES (also called “CLEFTS”), what is it made of?

Answer 3

indentations between the branchial arches (ectoderm)

Question 4

Define Branchial (Pharyngeal) MEMBRANES

Answer 4

formed by mesoderm forming in between the endoderm and ectoderm that prevent fusion of the branchial grooves and branchial pouches, prevents formation of the gills (Endoderm and ectoderm meet in fish and break down in fish to form gills)

Question 5

Define Pharyngeal pouches (‘gill pouches’)

Answer 5

(endoderm) outpounchings pushing off the pharynx, they push out where grooves are intending in. endoderm pushing out. (diverticula of the endoderm), we don’t see them because they are in the interior side

Question 6

Define Branchial Arch Mesenchyme (what 2 cell types form it?)

Answer 6

ectoderm from branchial arch and endoderm from endoderm

Question 7

Define Stomodeum

Answer 7

ectodermed lined pit

Question 8

Define Maxillary Prominence

Answer 8

from branchial arch 1, gives rise to most of the upper lip and jaw

Question 9

Define Mandibular Prominence

Answer 9

from 1st arch, give rise to all of lower lip and jaw

Question 10

Define Frontonasal Prominences

Answer 10

from 1st brachial arch (specifically the maxillary) forms placodes (epithelia swelling) – start with epithelia cells swell up and change shape to form this. – Center part of placodes form nasal pits – that eventually form nasal indentations. Forms the forehead and dorsal part of the nose

Question 11

Define Medial and lateral promiences come together to form the:

Answer 11

• They come together and form the nasal indentations

Question 12

Define Medial Nasal Prominences

Answer 12

 2 Medial nasal prominences

• Medial part of swelling (these bump into the maxillary prominences) to form the intermaxillary segment

Question 13

Define Lateral Nasal Prominences

Answer 13

 2 lateral nasal prominences

• Lateral nasal prominences

Question 14

Define Cervical sinus (it normally goes away)

Answer 14

remnant between grooves 2 and 3

Question 15

Define Branchial cyst, branchial sinus, and branchial fistula (persistent cervical sinus)

Answer 15

 Cervical sinus does not disappear: branchial cleft abnormality – forms cysts – sometimes fistula develops together this gives rise to branchial sinus – which can lead to discharge/infection – can also come from fistula that punches through the pharynx
 Sinus shouldn’t have drainage
 Fistual needs to be present before you get to a sinus

Question 16

Define: DiGeorge Syndrome

Answer 16

failure of pouches 3 and 4 to form.
• Absence of thymus and parathyroid
• usually lethal

Question 17

Define: Lingual swellings (buds) and the epiglottal swelling (thanks to the branchial arches)

Answer 17

o Lingual swelling (forms the connective tissue of the tongue) while head mesoderm from the muscles of the tongue – forms the tongue
o Epiglottis swelling – is branchial mesenchyme swelling around the glottis
 Slit in larynx (glottis) – transforms
• Branchial mesenchyme (endoderm and ectoderm meeting) migrates under the floor of the pharynx, some branchial mesenchyme migrate around the glottis (swelling) to form the epiglottis
• Branchial arch mesenchyme – migrates under endodermal structures and makes vocal cord

Question 18

Ankyloglossia

Answer 18

o too short of a frenulum – tongue tied

 Maybe syndromic – means that maybe there are more abnormalities

Question 19

Intermaxillary segment

Answer 19

fusion of medial nasal prominences to form intermaxilary segment (sits between maxillary segments) of upper lip and jaw, forms the midline of the midline of the upper lip and jaw and primary palate

Question 20

Cleft Lip

Answer 20

o Cleft lip - failure of maxillary segment to fuse with intermaxillary segment

Question 21

cleft Palate

Answer 21

• If 2 halves of maxillary segment doesn’t fuse – forms cleft palate
• Can have cleft palate and cleft lip
• Requires surgery

Question 22

4 major components of the branchial arches

Answer 22

• Branchial arch arteries
• Branchial arch cartilage
• Branchial arch muscles cells
• Branchial arch nerves

Question 23

Branchial arch arteries give rise to

Answer 23

aortic arch artieries, help form great vessels of the heart, out flow tracks

Question 24

Branchial arch cartilage give rise to

Answer 24

– viscerocranium - Mesenchyme from branchial arches migrates out and you get mesenchyme processes

1. Cartilages differentiate in to processes
2. Forms muscles and skeleton of the face

Question 25

Branchial arch muscles cells give rise to

Answer 25

• Most of the muscles of the face and neck come from branchial arch mesenchyme
• Neural crest – connective tissue tendons
• Head mesoderm - myoblasts
• Reciprocal induction

Question 26

Branchial arch nerves give rise to

Answer 26

major cranial nerve branches
•Branch of cranial nerves and keeps the pattern of innervation
•Neural crest cells break the rules – ectoderm – but it acts like mesoderm or endoderm

Question 27

branchial arch 1 differentiates into

Answer 27

maxillary and mandibular prominences

Question 28

fate of branchial arch 2

Answer 28

overgrows arches 3 and 4 and the branchial grooves in between = smooth neck

Question 29

fate of arch 3 & 4

Answer 29

becomes internalized, forms cervical sinus that usually goes away

Question 30

fate of 1st branchial groove (between arches 1 and 2)

Answer 30

forms the external acoustic meatus

Question 31

fate of branchial membrane #1 (between groove 1 and pouch 1)

Answer 31

forms the tympanic membrane

Question 32

fate of Adjacent parts of arches #1 and #2

Answer 32

form auricle (=pinna)

Question 33

What happens it the cervical sinus does not disappear?

Answer 33

forms cysts – sometimes fistula develops, gives rise to branchial sinus – which can lead to discharge/infection – can also come from fistula that punches through the pharynx (what i wrote from lecture)

Branchial Fistula - An abnormal canal that opens internally and externally on the side of the neck; fistula ascends from its opening in the neck, through the subcutaneous tissue and the platysma muscle, to reach the tonsillar sinus.

Cervical Cysts - Remnants of parts of the cervical sinus, the second pharyngeal groove, or both may persist and form a spherical or elongated cyst; do not become apparent until late childhood or early adulthood, when they produce a slowly enlarging, painless swelling in the neck ;enlarge because of the accumulation of fluid and cellular debris derived from desquamation of their epithelial linings

Question 34

fate of pouch 1

Answer 34

forms the auditory (eustachian) tubes (from branchial groove 1)

Question 35

fate of pouch 2

Answer 35

forms tympanic cavity (envelops the middle ear bones)

Question 36

fate of pouch 2

Answer 36

helps form the palatine tonsil

Question 37

fate of pouch 3

Answer 37

swells up, forms a bulbous end, and buds off; migrates down to form thymus, and bulbous end of pouch #3 form the inferior parathyroid glands (migrate further than pouch 4’s bulbous ending)

Question 38

fate of pouch 4

Answer 38

swells up, forms a bulbous end and buds off to form superior parathyroid glands (bulbous ending doesn’t go as far as pouch 3’s bulbous ending)

Question 39

What happens if pouch 3 and 4 fail to form?

Answer 39

DiGeorge Syndrome - Absence of thymus and parathyroid; usually lethal

Question 40

Defects of pouch 3 or 4 if they don’t travel far enough?

Answer 40

ectopic/asscessory thymus, parathyroid glands

Question 41

What is the epiglottis swellings derived from?

Answer 41

neural crest-derived

Question 42

How is the tongue dervied?

Answer 42

branchial arch mesenchyme migrates under the pharynx and pushed up the lingual swellings (tongue buds)

Question 43

What is branchial arch mesenchyme?

Answer 43

Made of head mesoderm and neural crest cells.

Question 44

How does the viscerocranium form?

Answer 44

branchial arch mesenchyme migrates out to form condensed “processes”, then cartilage forms in the processes

Question 45

What are the 5 prominences of that form the primitive face?

Answer 45

Frontalnasal prominance, 2 maxillary prominences and 2 mandibular prominences

Question 46

mandibular promience forms?

Answer 46

the lower lip, form the lower boundary of the stomedeum

Question 47

maxillary prominence forms?

Answer 47

most of the upper lip and cheeks and secondary palate; but never really meet. Try to come together but bump into the intermaxillary segment (fills the filtrum (above your lip)

Question 48

What are nasal placodes?

Answer 48

(epithelia swelling) nasal pits = nostrils that form in the frontonasal prominence

Question 49

What do the medial nasal prominences form?

Answer 49

fuse to make the intermaxillary segment (sits between maxillary segments) of upper lip and jaw, forms the midline of the midline of the upper lip (philtrum) and jaw and primary palate

Question 50

What are the medial and lateral nasal prominences?

Answer 50

4 new prominences that form on either side of the nasal placodes.

Question 51

What do lateral nasal prominences form?

Answer 51

sides of nose

Question 52

Frontonasal prominence form

Answer 52

the forehead (superior part of the nose)

Question 53

Which prominences form the palate?

Answer 53

intermaxillary segment form the primary palate (houses the incisors) and meet with the extensions of the maxillary prominence.

Question 54

What cause error in formation of the face?

Answer 54

errors in cell migration or cell fusion

Question 55

What is an error in the formation of the face?

Answer 55

Cleft palate = failure of maxillary prominence to migrate or fuse = persistent gap = “cleft lip” through the entire upper lip and jaw.

Question 56

When do paranasal sinuses differentiate?

Answer 56

mostly after birth (keeps head smaller before birth and lightens it after) = throat singing

Question 57

What is an error in the formation of the palate?

Answer 57

Cleft palate or cleft palate with cleft lip

Question 58

What does the branchial arch mesenchyme help form?

Answer 58

muscles of the face, neck (neural crest-derivatives from tendons, vasculature, connective tissue associated with the muscles; head mesoderm form the muscles.)

Question 59

What nerves from form the brachial/pharyngeal arch?

Answer 59

trigeminial (5); facial (7th); Glossopharyngeal (9th); Vagus (10th)