4* • Pharingeal grooves/cleft : 4 • [Pharyngeal membrane]
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Transcript of 4* • Pharingeal grooves/cleft : 4 • [Pharyngeal membrane]
Tdd : • Pharyngeal arches :
5* • Pahryngeal
pouches : 4* • Pharingeal
grooves/cleft : 4 • [Pharyngeal
membrane] : 4
Pharyngeal apparatus
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 primordial mandible
The cartilage intramembranous ossification
Pharyngeal arches
The second pharyngeal arch (hyoid arch) os hyoid, (along with parts of the third and fourth arches)
• During the 5th 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 ventral end of the second arch cartilage lesser cornu (Latin, horn) and the superior part of the body of the hyoid bone
• The part of cartilage between the styloid process and hyoid bone regresses; its perichondrium forms the stylohyoid ligament
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
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 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 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
The First Pharyngeal Pouch :
• expands & elongate
• forms a stalk-like diverticulum, the
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
• At approximately 20 weeks, the mesenchyme differentiates into lymphoid tissue,
• The pouch endoderm forms the surface epithelium and the lining of the tonsillar crypts.
• part of the cavity of this pouch remains as the tonsillar sinus or fossa.
• largely obliterated as the palatine tonsil develops
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 4th 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
• The brain and associated structures expand rostrally while the pharynx and cardiac structures generally expand caudally
• the derivatives of pharyngeal pouches 2 to 4 to become displaced
• Later , the parathyroid glands separate from the thymus and lie on the dorsal surface of the thyroid gland
Pharyngeal pouches
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 (MDP) 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]
• Mesenchyme in the margins of the placodes proliferates, producing horseshoe-shaped elevations-the medial and lateral nasal prominences. Nasal prominence : lateral & mediall (LNP & MNP)
• 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
apparatus pharyngeal
face
palata
odontogenesis
Other : tongue , salivary gland , sense organ
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 7th and 8th 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 down growth 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’)
apparatus pharyngeal
face
palata
odontogenesis
Other : tongue , salivary gland , sense organ
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
head & neck; (mouth & face incl’)
apparatus pharyngeal
face
palata
odontogenesis
Other : tongue , salivary gland , sense organ
DEVELOPMENT OF THE TONGUE • Near the end of the 4th week :
• 1st : 2 lateral lingual swellings and 1 medial swelling (tuberculum impar). These three mesodermal swellings originate from the 1st pharyngeal arch
• Next : A 2nd median swelling (copula &hypobranchial eminence) by mesoderm of the second, third, and part of the fourth arch
• 3rd median swelling, by the posterior part of the 4th arch epiglottis
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)., mandibular arch.
• Taste sensation from the mucosa is carried by the chorda tympani branch of the facial nerve (CN VII).
Pharyngeal part (posterior one third) of the tongue
• from the copula & 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,
• 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).
Pharyngeal part (posterior one third) of the tongue
• Most of the tongue muscles are derived from myoblasts from the occipital myotomes, carrying the hypoglossal nerve along with it Motor innervation. (CN XII).
• except for palatoglossus muscle, which is innervated by CN X
• 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
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. (SHH plays a role in cell growth, cell specialization, and the normal shaping (patterning) of the body.)
• 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