Outline
Development of the Branchial Region and Portions of the Head and Neck
Dr. Bennett-Clarke
General Information:  All these developmental aspects are happening at the same time (4th – 10th week)
• In the human embryo the primitive mouth (stomodeum) is a shallow depression at the cephalic end of the
pharyngeal foregut.
• It is separated from the pharyngeal foregut by the buccopharyngeal membrane.
• During the fourth week of development the buccopharyngeal membrane starts to degenerate, after this the
mouth will be open to the amniotic cavity.
-The Pharyngeal arches will wrap around and touch each other and form the pharyngeal apparatus
• At the same time, out-pouchings of the pharyngeal foregut develop just posterior to the degenerating
buccopharyngeal membrane (called the pharyngeal pouches).
• Four pairs of grooves develop between the pouches (pharyngeal grooves)
• Interposed between the grooves and the pouches are condensations of mesenchyme called the pharyngeal
arches.
• The pharyngeal arches are invaded by neural crest cells from the developing mid- and hindbrain regions of the
neural tube.
• The arches continue to develop and grow until they meet in the midline and completely surround of the
pharyngeal portion of the foregut.
The pharyngeal apparatus:
The pharyngeal apparatus is made up of the pharyngeal arches, pouches and grooves. The
pharyngeal apparatus contributes extensively to the formation of the face, nasal cavities, mouth,
larynx, pharynx and viscera of the neck.
Pharyngeal arches- five bars of mesenchymal tissue forming the ventral region of the developing
pharyngeal foregut.
Pharyngeal arch components
Initially each arch is composed
1. Outer ectoderm 
2. Core mesoderm  has two types
-Core Mesoderm = from para-axial mesoderm = Muscles & Endothelium of Blood
Vessels
- Neural crest cells = skeletal elements & other structures
Failed migration = deformities of the face
3. Inner endoderm  for developing pharynx/ foregut
A typical pharyngeal arch contains
1. Artery – off Dorsal Aorta
2. Cartilaginous Rod
3. Nerve = will be Cranial Nerves
Numbering of the Pharyngeal arches – Develop
Sequencially
First arch = Mandibular arch
Second arch = Hyoid Arch
Third arch = No Name
Fourth Arch = No Name
Fifth Arch = Rudimentary
Sixth = Small & Caudal
Fourth and sixth arches- (there is no fifth arch in
human and the sixth arch is only rudimentary)-
Derivatives of the pharyngeal arches
Arch
Skeletal
Muscle
Meckel's CartilageTemporalis, Masseter,
First Arch =
Will completely
Medial Pterygoid,
Mandibular Arch
Regress
Lateral Pterygoid,
Mylohyoid, Anterior
-Will turn into
Incus, Malleus, &
Digastric, Tensor
Mandibular &
Sphenomandibular
Tympani, & Tensor Veli
Maxillary Process
Ligament develop
Palatini
here
Reichert's
Cartilage – Mostly
Regress
Muscles of facial
Expression, Posterior
Second arch
Styloid Process,
Digastric, Stylohiod, &
Stylohyoid
Stapedius
Ligament, &
Superior part of
hyoid
Nerve
Blood Vessel
CN V = Mandibular
Branch
Maxillary artery
CN VII = Facial Nerve
Stapedial artery
Third arch
Inferior Part of
Hyoid, & Small
cartilages of the
larynx
Stylopharyngeus
CN IX =
Glossopharyngeal
Nerve
Internal Carotid
Fourth & Sixth
arches
Large Cartilages of
the Larynx
Muscles of the soft
palate, Muscles of the
pharynx, & Muscles of
the Larynx
CN X = Vagus
Left = Aortic arch
Right = Subclavian
Pharyngeal pouches- these are “balloon-like” diverticula that develop between the arches.
• There are four pair of well defined pouches.
• The pouches are lined with endoderm from the developing pharyngeal foregut.
Derivatives for the pharyngeal pouches
1. First pouch (between arch 1 and 2)  Will elongate
2. Second pouch (between arch 2 and 3)  Will be invaded by lymphatic tissue
3. Third pouch (between arch 3 and 4)  Expands into dorsal & ventral diverticula
4. Fourth pouch (between arch 4 and 6)  Expands into dorsal & ventral diverticula
5. Fifth pouch – not well developed
Derivatives for the pharyngeal pouches
Pouch
First pouch (between arch 1 & 2)
Second pouch (between arch 2 & 3)
Derivatives
Elongates and forms:
 Tympanic cavity
 Auditory Tube
 Internal aspect of tympanic
membrane
Forms Tonsilar bed:
Invaded by lymphatic tissue that forms the
tonsil
Dorsal Diverticula:
 Inferior Parathyroids
Third pouch (between arch 3 & 4)
Ventral Diverticula
 Thymus
Dorsal Diverticula:
 Superior Parathyroids
Fourth pouch (between arch 4 & 5)
Fifth pouch (between arch 5 & 6)
Ventral Diverticula
 Ultimobranchial Body
 Invades thyroid & gives rise to
parafollicular cells (C-Cells)
Never Forms
Pharyngeal grooves (clefts)- depression that separate the arches externally.
Only one pair of grooves exists as an adult structure, the first pharyngeal groove.
Derivatives of the pharyngeal grooves:
1. First groove (between arch 1 and 2)
2. Second through fourth grooves Arches two, three, & four overgrows
 Covers over all the other pharyngeal grooves
o Makes surface of neck smooth
Forms cervical sinus/cyst & Then Regresses
Derivatives of the pharyngeal grooves
Groove
Derivatives
First groove (between arch 1 & 2)
Lengthen to form:
External acoustic meatus
External aspect of tympanic membrane
Second through fourth grooves
Forms Cervical Sinus/Cyst
Will then regress
Anomalies of pharyngeal pouches or grooves
1. Branchial sinuses
 Blind pouch/recess on the inside (internal = remnant of pouches) or outside (external =
remnant of groove)
-- Usually at 2nd pouch or groove = may find in Tonsilar bed
2. Branchial cysts
 Persistent Cervical sinus/cyst
3. Branchial fistulas
 Opening either onto the skin (External) or into the pharynx (Internal)
Structures that develop in the floor of the pharynx:
Tongue- The tongue develops as a series of swellings in the floor of the pharynx.
1. Median tongue bud (tuberculum impar)
 On the floor of pharynx along 1st arch
2. Lateral lingual swellings/ Distal Tongue
Buds
Floor of 1st arch
Increase in size & move midline
Overgrow median bud
forms anterior 2/3rd of tongue
3. Copula
floor of the 2nd arch
4. Hypobranchial/pharyngeal eminence
Posterior to Copula from 3rd, 4th
(Mostly), & 6th arches
Overgrows Copula
Forms Posterior 1/3rd of tongue
5. Terminal sulcus
Junction between anterior 2/3rd &
Posterior 1/3rd of tongue
Only visible once tongue buds has met
**Muscles of the tongue do not originate in
the pharyngeal wall but migrate there from
the occipital somites.
Thyroid gland- The thyroid gland is the first endocrine organ to develop in the embryo.
1. Thyroid diverticulum  pouch in the developing tongue
a. Migrates anterior to hyoid and thyroid cartilages
2. Thyroglossal duct
a. As the diverticulum migrates it drags the duct with it
b. Will regress (in almost all cases)
3. Foramen cecum  Spot on the tongue where the thyroid diverticulum is/was
Ectopic Thyroid Tissue- can be anywhere along its course (Tongue, neck, laryngeal cartilages)
 Can have a pyramidal lobe of the thyroid = from Thyroglossal duct
Thyroglossal duct cysts- These are cysts that form anywhere along the course of the former
thyroglossal duct, in the tongue, anterior neck or anterior to the laryngeal cartilages.
Formation of the face- The face develops between the 4th and 8th weeks of development.
There are five faces primordial
1. Frontonasal prominence2. Maxillary prominences3. Mandibular prominencesThe frontonasal prominence- surrounds the developing forebrain. Develops into the forehead,
majority of the nose and a portion of the upper lip.
• Frontonasal prominence develops two lateral thickened areas- the nasal placodes.
• The lateral and medial rims of this enlarge and in the center there is a depression the nasal pit.
• The lateral rim is called the lateral nasal swellings or processes and the medial is the medial nasal
swellings or processes.
• The medial nasal swellings meet in the midline to form the intermaxillary segment. This will
give rise to the philtrum of the upper lip, and portions of the upper jaw, nasal septum and palate
(primary palate).
The maxillary and mandibular prominences develop from the first pharyngeal arch. The prominences
are produced by a proliferation of neural crest cells that migrate there from the lower midbrain and
hindbrain regions of the developing neural tube.
The maxillary prominences
• Grow toward the lateral nasal swellings and meet at the nasolacrimal groove.
• Result in the formation of the lateral portion of the upper lip, upper cheek, most of the
maxilla and the palate.
The mandibular prominences
• Meet the maxillary prominence laterally & the opposite mandibular process in the midline.
• Result in the formation of the adult lower lip, lower cheek, chin and mandible.
The mesenchyme from the second pharyngeal arch invades the areas of these two prominences and
forms the muscles of facial expression.
Development of the palate- the palate develops during the 5th week of the embryonic period.
The palate develops from two primordia
The primary palate
The secondary palate
• The primary palate develops from the intermaxillary segment. (remember this came from the
frontonasal prominence.) The primary palate forms only the most anterior portion of the adult hard
palate, anterior to the incisive foramen.
• The secondary palate develops as two processes from the internal surface of the maxillary
prominences. These are the lateral palatine processes. Gradually the processes enlarge and grow to
meet in the midline. They also fuse with the developing nasal septum. The anterior portion of these
processes contributes to the hard palate and the posterior portion to the soft palate.
• The incisive foramen marks the junction of the primary and secondary palates. The midline raphe
marks the junction of the lateral palatal processes.
Cleft palate and lip- These are two of the most common defects of the face. Where
intermaxillary segment met the maxillary process
Cleft lip - occurs about 1 in 900 births, more in boys than girls.
Happens just adjacent to the philtrum
1. Unilateral (B) - failure of the fusion of the maxillary and intermaxillary segments to fuse.
2. Bilateral (D) - failure of fusion on both sides
Cleft palate - 1 in 2,500 births, more in girls and than boys.
1. Anterior (primary; C & D)- failure of the primary palate to meet the secondary palate.
2. Posterior (secondary; E))-failure of the lateral palatine processes to fuss together and with the
nasal septum.
3. Complete (F)- the most severe clefting combination of both the anterior and posterior