Pharyngeal arches Pharyngeal pouches Pharingeal grooves/cleft

Pharyngeal arches Pharyngeal pouches

Pharingeal grooves/cleft [Pharyngeal membrane]

• The pharyngeal arches contribute extensively to the formation of the face, nasal cavities, mouth, larynx, pharynx, and neck

• @ punya arteri & saraf cranial

• Pada manusia ada 5, karena yg ke-5 regresi

• 1 &2 s.d midline

• Makin caudal makin pendek

• Dipisahkan satu sama lain oleh

– Pharyngeal pouch [internal]

– Pharygeal grooves [external]

• Permukaan luar ditutupi ectoderm

• Permukaan dalam (pharyngeal) oleh endoderm; kcl 1st arcus oleh ectoderm

• INTI : sel Neural Crest , dg sekitarnya dikelilingi mesoderm.

• @ diff:

– Mesoderm otot, pembuluh darah*

– CNC tulang, cartilago, jaringan ikat.

Pharyngeal arches

The first pharyngeal arch (mandibular arch)

= Meckel cartilage

separates into two prominences :

– The maxillary prominence gives rise to the maxilla,

zygomatic bone, and a portion of the vomer .

– The mandibular prominence forms the mandible. The

proximal mandibular prominence also forms the

squamous temporal bone (os temporalis).

Pharyngeal arches

• The dorsal end of the first pharyngeal arch cartilage :

– Early in development, small nodules break away

from the proximal part of this cartilage and form

malleus and incus.

– The middle part of the cartilage regresses, but its

perichondrium forms the anterior ligament of

malleus and the sphenomandibular ligament.

• Ventral parts primordium of the mandible

The cartilage intramembranous ossification

Pharyngeal arches

Pharyngeal arches

1st arch

- Tdd processus maxillar [dorsal] & mandibular [ventral]

Pharyngeal arches

The second pharyngeal arch (hyoid arch) os hyoid, (along with parts of the third and fourth arches)

• During the fifth week, the second pharyngeal arch enlarges and overgrows the third and fourth arches, forming an ectodermal depression-the cervical sinus

Pharyngeal arches

• An independent cartilage anlage near the dorsal end of the second pharyngeal arch cartilage (Reichert cartilage), ossifies to form the stapes of the middle ear and the styloid process of the temporal bone

• The part of cartilage between the styloid process and hyoid bone regresses; its perichondrium forms the stylohyoid ligament

• The ventral end of the second arch cartilage lesser cornu (Latin, horn) and the superior part of the body of the hyoid bone

Pharyngeal arches

Pharyngeal arches

• Muscles of the hyoid arch :

– the stapedius,

– stylohyoid,

– posterior belly of the digastric,

– auricular, muscles of facial expression.

• The facial nerve, the nerve of the second arch, supplies all of these muscles.

Pharyngeal arches

2nd arch

Pharyngeal arches

The third pharyngeal arch cartilage,

greater cornu and the inferior part of the body of the hyoid bone.

– The musculature is limited to the stylopharyngeus muscles. These muscles are innervated by the glossopharyngeal nerve, the nerve of the third arch

Pharyngeal arches

• The fourth and sixth pharyngeal arch cartilages fuse laryngeal cartilages, except for the epiglottis.

– Muscles of the fourth arch (cricothyroid, levator palatini, and constrictors of the pharynx) are innervated by the superior laryngeal branch of the vagus, the nerve of the fourth arch.

– Intrinsic muscles of the larynx are supplied by the recurrent laryngeal branch of the vagus, the nerve of the sixth arch.

Pharyngeal arches

• The fifth pharyngeal arch is rudimentary (if present) and has no derivatives.

• The cartilage of the epiglottis develops from mesenchyme in the hypopharyngeal eminence, a prominence in the floor of the embryonic pharynx that is derived from the third and fourth pharyngeal arches.

Pharyngeal arches

Pharyngeal arches

Musculature derive from arcus pharynx

Pharyngeal arches Nerves Derive from the Pharyngeal Arch

Pharyngeal arches

PHARYNGEAL POUCHES

• develop in a craniocaudal sequence between the arches

• There are 4 well-defined pairs of pharyngeal pouches; the 5th pair is rudimentary or absent.

• The endoderm of the pouches contacts the ectoderm of the pharyngeal grooves the double-layered pharyngeal membranes that separate the pharyngeal pouches from the pharyngeal grooves

Pharyngeal pouches

The First Pharyngeal Pouch :

• expands into an elongate tubotympanic recess The distal part of this recess contacts the first pharyngeal groove the formation of the tympanic membrane (eardrum).

• The cavity of the tubotympanic recess tympanic cavity & antrum mastoid

• The connection of the tubotympanic recess with the pharynx gradually elongates pharyngotympanic tube (auditory tube).

Pharyngeal pouches

The Second Pharyngeal Pouch

• largely obliterated as the palatine tonsil develops,

• part of the cavity of this pouch remains as the tonsillar sinus or fossa.

• The pouch endoderm forms the surface epithelium and the lining of the tonsillar crypts.

• At approximately 20 weeks, the mesenchyme differentiates into lymphoid tissue,

Pharyngeal pouches

The Third Pharyngeal Pouch

• [6th week] : the epithelium of each dorsal part differentiate into an inferior parathyroid gland.

• The epithelium of the ventral parts come together in the median plane to form the thymus

• Each lobe has its own blood supply , lymphatic drainage, and nerve supply.

• Next : lose their connections with the pharynx.

Pharyngeal pouches

• The brain and associated structures expand rostrally while the pharynx and cardiac structures generally expand caudally the derivatives of pharyngeal pouches two to four to become displaced caudally .

• Later , the parathyroid glands separate from the thymus and lie on the dorsal surface of the thyroid gland

Pharyngeal pouches

Pharyngeal pouches

The Fourth Pharyngeal Pouch

• [6th week] :

• Ventral : ultimobranchial body, incorporated with thyroid, give rise to C cell (parafollicular cells)

• each dorsal part superior parathyroid gland, which lies on the dorsal surface of the thyroid gland.

Pharyngeal pouches

Pharyngeal pouches

Pharyngeal pouches

superior parathyroid gland

PHARYNGEAL GROOVES/cleft • on each side during the fourth and fifth weeks.

• separate the pharyngeal arches externally .

• Only one pair of grooves contributes to postnatal structures; the first pair persists as the external acoustic meatus or ear canals

• The other grooves lie in a slitlike depression-the cervical sinus-and are normally obliterated along with the sinus as the neck.

• [end of the 7th week], the second to fourth pharyngeal grooves and the cervical sinus have disappeared, giving the neck a smooth contour

PHARYNGEAL MEMBRANES

• As floors of the pharyngeal grooves.

• the epithelia of the grooves and pouches approach each other. The endoderm of the pouches and the ectoderm of the grooves are soon separated by mesenchyme.

• Only one pair of membranes contributes to the formation of adult structures; the first pharyngeal membrane, along with the intervening layer of mesenchyme, becomes the tympanic membrane.

head formation

apparatus pharyngeal

face

palata

odontogenesis

Other : tongue , salivary gland , sense organ

DEVELOPMENT OF THE FACE

• occurs mainly between the 4th and 8th week

• depends on the inductive influence of the prosencephalic and rhombencephalic organizing centers brain development.

Craniofacial growth pattern

• The first and general component—accounting for most variation—is allometric – Brain growth predominates

– flattening the cranial base

– the displacement of the nasomaxillary segment;

– growth of the orbital contents

• The second component is alveolar remodeling – depends on the presence of tooth buds or teeth

• The third component is mandibular condylar growth

Seraut wajah....

Mulut primitif

• [end 3rd week] : stomodeum (calon oral&nasal cavities)

• Berupa depresi ectoderm di bag.cephalic kontak dg endoderm = buccopharyngeal membrane/oropharygeal membrane

• buccopharyngeal membrane akan jd lokasi tonsila, memisahkan stomodeum dg foregut

face

• [4th week]: bpm ruptur komunikasi stomodeum-GIT primitif

• Note : before that: pbentukan hipofise anterior dr stomodeum ectoderm, b’evaginasi di atap mulut primitif (depan bpm). Jalur : rathke’s pouche

• Terbentuk tonjolan2 sekitar stomodeum; = facial prominences (t.u CNC & arcus pharynx I*)

face

Facial prominences

• produced mainly by the expansion of neural crest

[4th week]:

• 2 Maxillary = MXP [lateral]

• 2 Mandibular = MDP [caudal to maxillary]

• The frontonasal prominence (FNP) [upperborder of

stomodeum]

– (FNP) surrounds the ventrolateral part of the forebrain

the optic vesicles that form the eyes.

– The frontal part of the FNP forms the forehead;

face

• CNC : the major source of connective tissue components, including cartilage, bone, and ligaments in the facial and oral regions.

• myoblasts, originating from paraxial and prechordal mesoderm, contribute to the craniofacial voluntary muscles.

• The lower jaw and lower lip are the first parts of the face to form. They result from merging of the medial ends of the mandibular prominences in the median plane

face

• [end 4th week] : bilateral oval thickenings of the surface ectoderm- nasal placodes -the primordia of the nasal epithelium, have developed on the inferolateral parts of the FNP

[5th week]

• Nasal prominence : lateral & mediall (LNP & MNP)

• Mesenchyme in the margins of the placodes proliferates, producing horseshoe-shaped elevations-the medial and lateral nasal prominences.

• As a result, the nasal placodes lie in depressions the nasal pits.These pits are the primordia of the anterior nares (nostrils) and nasal cavities

face

• Proliferation of mesenchyme in the maxillary prominences (MXP) causes them to enlarge and grow medially toward each other and the nasal prominences.

• Each lateral nasal prominence is separated from the maxillary prominence by a cleft called the nasolacrimal groove.

• [end 6th sixth week], each maxillary prominence (MXP) has begun to merge with the lateral nasal prominence (LNP) along the line of the nasolacrimal groove .

• The nasal septum develops as a down growth from internal parts of the merged medial nasal prominences

face

• During the early fetal period, the nose is flat and the mandible is underdeveloped

• As the brain enlarges, the cranial vault expands bilaterally . This causes the orbits, which were oriented laterally , to assume their forward-facing orientation.

• The opening of the external acoustic meatus (auditory canal) to the auricle of the ears appears to elevate, but in reality remains stationary .

• Late embryonic periode & early fetal :

jaws (particulary mandible) exhibit

rapid anterior growth; in order to

facilitate tongue repositioning & palatal

closure

• During 2nd & 3rd trimesters, growth of

fetal head is isometric maximizing

brain size, minimizing the face.

• So, 12-15 weeks = period of flux

between allometrix to isometric

• Mandibular retrognatia is characteristic

of newborn

• @birth: Face is very small relative to the

cranium

• TMJ@condyle are very rudimentary; the

suckling motion of the mandible : limited

• The “smallness” of the face prenatally results from:

– The rudimentary upper and lower jaws

– The unerupted primary (deciduous) teeth

– The small size of the nasal cavities and maxillary sinuses

First Arch Syndrome

• Abnormal development of the components of the first pharyngeal arch results in various congenital anomalies of the eyes, ears, mandible, and palate that together constitute the first arch syndrome

• This syndrome is believed to result from insufficient migration of neural crest cells into the first arch during the fourth week.

• There are two main manifestations of the first arch syndrome:

– In Treacher Collins syndrome (mandibulofacial dysostosis), caused by an autosomal dominant gene, there is malar hypoplasia (underdevelopment of the zygomatic bones of the face) with down-slanting palpebral fissures, defects of the lower eyelids, deformed external ears, and sometimes abnormalities of the middle and internal ears.

– In Pierre Robin syndrome, an autosomal recessive disorder , is associated with hypoplasia of the mandible, cleft palate, and defects of the eye and ear are present. Many cases of this syndrome are sporadic. In the Robin morphogenetic complex, the initiating defect is a small mandible (micrognathia), which results in posterior displacement of the tongue and

head formation


face

palata

odontogenesis


DEVELOPMENT OF THE PALATE (Palatogenesis)

• The palate develops in two stages:

– The development of a primary palate

– The development of a secondary palate

• begins in the sixth week; but not completed until the 12th week.

• The critical period of palate development is from the end of the sixth week until the beginning of the ninth week.

Primary Palate

• Early in the 6th week, the primary palate-median palatal process (intermaxillary segment)-begins to develop, by merging of the medial nasal prominences

• = mass of mesenchyme between the internal surfaces of the maxillary prominences.

• The primary palate forms the anterior/midline aspect of the maxilla, the premaxillary part of the maxilla).

• It represents only a small part of the adult hard palate (i.e., anterior to the incisive fossa).

• Between the 7th and 10th weeks , As a result of medial growth of the maxillary prominences, the two medial nasal prominences merge together at the midline

• It is composed of :

– a labial componen the philtrum of the upper lip;

– an upper jaw component, which carries the four incisor teeth;

– a palatal component, the triangular primary palate.

• intermaxillary segment is continuous with the rostral portion of the nasal septum, which is formed by the frontal prominence.

Secondary Palate

• = the primordium of the hard and soft parts of the palate

• The secondary palate begins to develop early in the sixth week

• from two mesenchymal projections from the internal aspects of the maxillary prominences (lateral palatal processes/palatine shelves).

• Shelves project inferomedially on each side of the tongue.

• During the seventh and eighth weeks, the lateral palatal processes assume a horizontal position above the tongue fuse along the palatine raphe secondary palate

• Primary&secondary fuse at foramen incisivus definitive palate

• Bone develop only in primary palate & anterior part of secondary palate palatum durum (hard palate)

• The rest : soft palate & uvula

• The nasal septum develops as a downgrowth from internal parts of the merged medial nasal prominences.

• The fusion between the nasal septum and the palatal processes begins anteriorly during the ninth week and is completed posteriorly by the 12th week, superior to the primordium of the hard palate.

Suggestion reading : Cleft lip and palate: Dental care for the patient with a cleft lip and palate. Part 1: From birth to the mixed dentition stage C J Rivkin, O Keith, P J M Crawford & I S Hathorn

British Dental Journal 188, 78 - 83 (2000)

head & neck; (mouth & face incl’)


face

palata

odontogenesis


Tooth development

• arise from an epithelial-mesenchymal (derived from neural crest Cells) interaction. All CT from CNC.

• [6th week] : thickening of the epithelial lining of the oral cavity forms the dental lamina, along the length of the upper and lower jaws.

• This lamina subsequently gives rise to a number of dental buds (@10) primordia of the ectodermal components of the teeth.

• deep surface of the buds invaginates cap stage of tooth development bell stage

• A. Bud stage; 8 weeks.

• B. Cap stage; 10 weeks.

• C. Bell stage; 3 months.

• D. 6 months.

head & neck; (mouth & face incl’)


face

palata

odontogenesis


DEVELOPMENT OF THE TONGUE • Near the end of the 4th week : proliferation of mesenchyme

in ventromedial parts of the first pair of pharyngeal arches.

• a median elevation appears in the floor of the primordial pharynx, just rostral to the foramen cecum median lingual swelling (tongue bud)

• Next, two lateral lingual swellings (distal tongue buds) develop on each side of the median tongue bud.

• Most of the tongue muscles are derived from myoblasts that migrate from the occipital myotomes

• Motor innervation is supplied by the hypoglossal nerve (CN XII), except for palatoglossus muscle, which is innervated by CN X.

Oral part (anterior two thirds) of the tongue

• The lateral lingual swellings rapidly increase in size, merge with each other , and overgrow (grow FASTER) the median lingual swelling. The merged lateral lingual swellings form the anterior two thirds (oral part) of the tongue forming the median sulcus (midline groove )

• The oral part is characterized by filiform papillae (no taste buds), fungiform papillae (taste buds present), foliate papillae (taste buds present), and circumvallate papillae (taste buds present).

• General sensation from the mucosa is carried by the lingual branch of the trigeminal nerve (cranial nerve [CN] V).

• Taste sensation from the mucosa is carried by the chorda tympani branch of the facial nerve (CN VII). S

Pharyngeal part (posterior one third) of the tongue

• from the copula and hypobranchial eminence that develops in the floor of the pharynx associated with pharyngeal arches 2, 3, and 4.

• The hypobranchial eminence overgrows the copula, thereby eliminating any contribution of pharyngeal arch 2 in the formation of the definitive adult tongue.

• The line of fusion of the anterior and posterior parts of the tongue is roughly indicated by a V -shaped groove-the terminal sulcus

• The pharyngeal part is characterized by the lingual tonsil,

Pharyngeal part (posterior one third) of the tongue

• General sensation from the mucosa is carried primarily by the glossopharyngeal nerve (CN IX).

• Taste sensation from the mucosa is carried predominantly by the glossopharyngeal nerve (CN IX).

Both the anterior and posterior portions of the tongue are located within the oral cavity at birth; the posterior third descends into the oropharynx by 4 years of age.

DEVELOPMENT OF THE SALIVARY GLANDS

• [6-7th weeks] begin as solid epithelial buds from the primordial oral cavity

• The club-shaped ends of these epithelial buds grow into the underlying mesenchyme.

• The connective tissue in the glands is derived from neural crest cells.

• All parenchymal (secretory) tissue arises by proliferation of the oral epithelium.

The parotid glands submandibular glands The sublingual glands

time first to appear (early in the

sixth week

late in the sixth week eighth week, approximately 2

weeks later than the other

salivary glands

from from buds that arise from the

oral ectodermal lining near

the angles of the stomodeum

from endodermal buds in the

floor of the stomodeum

From multiple endodermal

epithelial buds in the

paralingual sulcus

mx Elongation of the jaws causes

lengthening of the parotid

duct, with the gland remaining

close to its site of origin.

Later the cords canalize-

develop lumina-and become

ducts by approximately 10

weeks. The rounded ends of

the cords differentiate into

acini

Solid cellular processes grow

posteriorly , lateral to the

developing tongue. Later they

branch and differentiate. Acini

begin to form at 12 weeks.

Lateral to the tongue, a

linear groove forms that soon

closes over to form the

submandibular duct.

buds branch and canalize to

form 10 to 12 ducts that open

independently into

the floor of the mouth

secret 18 weeks begins at 16 weeks

misc The capsule and connective

tissue develop from the

surrounding mesenchyme.

Growth of the submandibular

glands continues after birth

with the formation of mucous

acini.

DEVELOPMENT OF THE NOSE

• The specialized olfactory epithelium of the nose appears as the olfactory (nasal) placodes on the inferolateral aspects of the frontonasal prominence, toward the end of the somite period.

• The olfactory nerve cells connect with the olfactory bulb of the brain through the cribriform plate of the ethmoid bone.

DEVELOPMENT OF THE EYE • The eye is derived from surface ectoderm, neural

ectoderm, neural crest tissue, and mesoderm.

• the retina, is a direct outgrowth from the forebrain, projecting bilaterally as the optic vesicles, which are connected to the brain by the optic stalks

• the optic stalks become the optic nerves

• The neuroectodermal optic vesicles induce their overlying surface ectoderm to thicken lens

• The eyes migrate from their initially lateral positions toward the midline of the face

DEVELOPMENT OF The EAR • [end 5th week] : the primordia of the auricles (external

part of the ears) have begun to develop. Six auricular hillocks (three mesenchymal swellings on each side) form around the first pharyngeal groove (three on each side), the primordia of the auricle, and the external acoustic meatus, respectively .

• Initially the external ears are located in the neck region [as the mandible develops] located on the side of the head at the level of the eyes .

• The internal ear arises from the otic placode 1st sensory organ to begin development;

• this development is initiated by neural crest induction of surface ectoderm

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MOLECULAR SCIENCE

Molecular Regulation

• The fate of cells is regulated by signalling molecules.

Growth factors

• The growth factors involved in orofacial development belong mainly to four families that are well conserved between different species: – the Fibroblast Growth Factor (FGF) family,

– the Hedgehog (HH) family,

– the Transforming Growth Factor beta (TGF- β) family, which includes the Bone Morphogenetic Proteins (BMPs) and Activins

– the Wingless (WNT) family

• The FGF : facial epithelium and mesenchyme and mainly involved in stimulating cell proliferation

• SHH is expressed in the ectoderm of the frontonasal and maxillary processes during development. SHH is also expressed at all stages of tooth development.

• TGF signalling pathway has major role in the molecular cascade that dictates craniofacial development. – TGF pathway may be also important in lip formation

– several members of the BMP family have been shown to be expressed at various stages of tooth development.

• WNT expression is often coincident with the expression of molecules of the Hedgehog and TGF-β families – This family also includes the Bone Morphogenetic Protein

(BMP) and Activin signalling molecules

transcription factors

• Many transcription factors are important

• The transcription factors MSX1 and PAX9 are responsible for partial tooth agenesis in humans. MSX1 is induced by BMP and FGF molecules and its mutation leads to selective absence of upper lateral incisors and/or upper and lower second pre-molar teeth

• MSX1 mutations were also detected Point mutations in the TBX22 are found in 8% of cleft palate patients

• IRF6 is considered as a major gene causing approximately 12% of CL or CLP phenotypes

Terima kasih

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Pharyngeal arches Pharyngeal pouches Pharingeal grooves/cleft

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