Embryology of the Head and Neck: the Pharyngeal Apparatus (Branchial Apparatus) Flashcards
Define Branchial (Pharyngeal) ARCHES (‘gill arches’)
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
What is Branchial arch mesenchyme made of?
head mesoderm
Define Branchial (Pharyngeal) GROOVES (also called “CLEFTS”), what is it made of?
indentations between the branchial arches (ectoderm)
Define Branchial (Pharyngeal) MEMBRANES
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)
Define Pharyngeal pouches (‘gill pouches’)
(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
Define Branchial Arch Mesenchyme (what 2 cell types form it?)
ectoderm from branchial arch and endoderm from endoderm
Define Stomodeum
ectodermed lined pit
Define Maxillary Prominence
from branchial arch 1, gives rise to most of the upper lip and jaw
Define Mandibular Prominence
from 1st arch, give rise to all of lower lip and jaw
Define Frontonasal Prominences
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
Define Medial and lateral promiences come together to form the:
• They come together and form the nasal indentations
Define Medial Nasal Prominences
2 Medial nasal prominences
• Medial part of swelling (these bump into the maxillary prominences) to form the intermaxillary segment
Define Lateral Nasal Prominences
2 lateral nasal prominences
• Lateral nasal prominences
Define Cervical sinus (it normally goes away)
remnant between grooves 2 and 3
Define Branchial cyst, branchial sinus, and branchial fistula (persistent cervical sinus)
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
Define: DiGeorge Syndrome
failure of pouches 3 and 4 to form.
• Absence of thymus and parathyroid
• usually lethal
Define: Lingual swellings (buds) and the epiglottal swelling (thanks to the branchial arches)
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
Ankyloglossia
o too short of a frenulum – tongue tied
Maybe syndromic – means that maybe there are more abnormalities
Intermaxillary segment
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
Cleft Lip
o Cleft lip - failure of maxillary segment to fuse with intermaxillary segment
cleft Palate
- If 2 halves of maxillary segment doesn’t fuse – forms cleft palate
- Can have cleft palate and cleft lip
- Requires surgery
4 major components of the branchial arches
- Branchial arch arteries
- Branchial arch cartilage
- Branchial arch muscles cells
- Branchial arch nerves
Branchial arch arteries give rise to
aortic arch artieries, help form great vessels of the heart, out flow tracks
Branchial arch cartilage give rise to
– viscerocranium - Mesenchyme from branchial arches migrates out and you get mesenchyme processes
- Cartilages differentiate in to processes
- Forms muscles and skeleton of the face
Branchial arch muscles cells give rise to
- Most of the muscles of the face and neck come from branchial arch mesenchyme
- Neural crest – connective tissue tendons
- Head mesoderm - myoblasts
- Reciprocal induction
Branchial arch nerves give rise to
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
branchial arch 1 differentiates into
maxillary and mandibular prominences
fate of branchial arch 2
overgrows arches 3 and 4 and the branchial grooves in between = smooth neck
fate of arch 3 & 4
becomes internalized, forms cervical sinus that usually goes away
fate of 1st branchial groove (between arches 1 and 2)
forms the external acoustic meatus
fate of branchial membrane #1 (between groove 1 and pouch 1)
forms the tympanic membrane
fate of Adjacent parts of arches #1 and #2
form auricle (=pinna)
What happens it the cervical sinus does not disappear?
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
fate of pouch 1
forms the auditory (eustachian) tubes (from branchial groove 1)
fate of pouch 2
forms tympanic cavity (envelops the middle ear bones)
fate of pouch 2
helps form the palatine tonsil
fate of pouch 3
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)
fate of pouch 4
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)
What happens if pouch 3 and 4 fail to form?
DiGeorge Syndrome - Absence of thymus and parathyroid; usually lethal
Defects of pouch 3 or 4 if they don’t travel far enough?
ectopic/asscessory thymus, parathyroid glands
What is the epiglottis swellings derived from?
neural crest-derived
How is the tongue dervied?
branchial arch mesenchyme migrates under the pharynx and pushed up the lingual swellings (tongue buds)
What is branchial arch mesenchyme?
Made of head mesoderm and neural crest cells.
How does the viscerocranium form?
branchial arch mesenchyme migrates out to form condensed “processes”, then cartilage forms in the processes
What are the 5 prominences of that form the primitive face?
Frontalnasal prominance, 2 maxillary prominences and 2 mandibular prominences
mandibular promience forms?
the lower lip, form the lower boundary of the stomedeum
maxillary prominence forms?
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)
What are nasal placodes?
(epithelia swelling) nasal pits = nostrils that form in the frontonasal prominence
What do the medial nasal prominences form?
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
What are the medial and lateral nasal prominences?
4 new prominences that form on either side of the nasal placodes.
What do lateral nasal prominences form?
sides of nose
Frontonasal prominence form
the forehead (superior part of the nose)
Which prominences form the palate?
intermaxillary segment form the primary palate (houses the incisors) and meet with the extensions of the maxillary prominence.
What cause error in formation of the face?
errors in cell migration or cell fusion
What is an error in the formation of the face?
Cleft palate = failure of maxillary prominence to migrate or fuse = persistent gap = “cleft lip” through the entire upper lip and jaw.
When do paranasal sinuses differentiate?
mostly after birth (keeps head smaller before birth and lightens it after) = throat singing
What is an error in the formation of the palate?
Cleft palate or cleft palate with cleft lip
What does the branchial arch mesenchyme help form?
muscles of the face, neck (neural crest-derivatives from tendons, vasculature, connective tissue associated with the muscles; head mesoderm form the muscles.)
What nerves from form the brachial/pharyngeal arch?
trigeminial (5); facial (7th); Glossopharyngeal (9th); Vagus (10th)
