The development
of the head and neck
Carnegie 13 (28 – 32 days)
4 – 6 mm, 30 somites
Vývoj hlavy, krku
pharyngeal
arches
• lips
• oral cavity
– vestibule
•
•
•
•
•
•
teeth
tongue
hard palate
soft palate
pharynx
larynx
• parotid gland
• submandibular
gland
• sublingual
gland
• thyroid gland
• parathyroid gland
– 4 bodies
• thymus
http://www.mayoclinic.com/images/image_popup/pthyroid.jpg
Development of the digestive tube
• primitive gut
• formed during the 4th week, as the head, tail and
lateral folds incorporate a part of the yolk sack into
the embryo
– foregut (preentereon) – separated from the
stomodeum (primitive mouth) by membrana
oropharyngea, protrusion of the base of the
lower respiratory tract
– midgut (mesenteron) – distally from the liver
bud to ductus vitellinus
– hindgut (metenteron) – further, separated from
proctodeum (anal pit) by membrana cloacalis
Origin of the mesenchyme
• paraaxial mesoderm (non-segmented)
– bones of the base of the skull and some of the bones of
calvaria
– all the skeletal muscles
– dermis and fibrous tissue on the dorsal part of the head
• ectomesenchyme (from the neural crest)
– skeleton of the face and pharyngeal arches
• ectodermal placodes (thickened areas of ectoderm)
• pharyngeal arches
• occipital segments (basis et condyli ossis occipitalis)
Pharyngeal apparatus
•
•
•
•
pharyngeal arches (arcus pharyngei)
pharyngeal pouches (sacci pharyngei)
pharyngeal grooves (sulci pharyngei)
pharyngeal membranes (membranae
pharyngeae)
Thomas W. Sadler, Langman´ Medical embryology, 10th edition
Pharyngeal arches (arcus pharyngei)
• paired structures
• begin to develop in the 4th-5th week
• separation of the columns of the mesenchyme:
– there are pharyngeal grooves on the outer side (depressions in the
ectoderm)
– there are pharyngeal pouches on the inner side (formed by the
endoderm of the primitive larynx)
– grooves and pouches never merge (no gills form)
• the mesenchyme of neural crest cells is streaked by paraaxial
mesoderm and in each pharyngeal arch gives rise to muscles
• cartilages and skeleton of the arches are differentiated from the
ectomesenchyme
• each arch is innervated by a cranial nerve and has its own artery (aa.
arcuum pharyngeorum = aortic arches)
• 5th arch does not arise
Aortic arches
(Aa. arcuum pharyngeorum)
Derivatives of the pharyngeal arch arteries I
• 1st pair – arteria maxillaris + carotis externa
• 2nd pair – arteria stapedia
• 3rd pair – proximally - arteria carotis communis
- distally - arteria carotis interna
Derivatives of the pharyngeal arch arteries II
• 4th pair –
– left – part of arcus aortae
– right – a. subclavia dx.
• distal part of a. subclavia dx. comes from aorta dorsalis dextra
– a. subclavia sin. is not a derivative of arcus aortae, but of
the 7th intersegmental artery
Derivatives of the pharyngeal arch arteries III
• 5th pair - Ø
• 6th pair –
– left
– right
prox. arteria pulmonalis sinistra
dist. ductus arteriosus (Botali)
prox. arteria pulmonalis dextra
dist. Ø
arch
1. mandibular
(maxillary
and
mandibular
process)
nerve
n. trigeminus
muscles
muscles of mastication
(m. temporalis, m.
masseter, m.
pterygoideus medialis et
lateralis)
m. mylohyoideus, venter
anterior m. digastrici
m. tensor tympani
m. tensor veli palatini
skeletal structures
premaxilla, maxilla, os
palatinum, os
zygomaticum, squama
ossis temporalis,
Meckel´s cartilage,
mandibula, malleus,
incus
ligaments
lig. mallei ant.,
lig.
sphenomandibulare
arteries
a. maxillaris
2.
hyoid
n. facialis
stapes,
processus styloideus,
cornua minora et
corpus ossis hyoidis
(upper part)
lig. stylohyoideum
a. stapedia
3.
arch
n.glossopharyngeus
muscles of facial
expression
(m. buccinator, mm.
auriculares, m. frontalis,
platyzma, m. orbicularis
oris et oculi)
m. stapedius
m. stylohyoideus, venter
posterior m. digastrici
m. stylopharyngeus
4.
left
n. laryngeus superior
(n.X)
6.
right
left
right
m. cricothyroideus, m.
levator veli palatini, m.
constrictor pharyngis
med. et inf.,
n. laryngeus recurrens intrinsic muscles of
larynx
(fibres from n.
striated muscles of the
accessorius using n.
oesophagus
vagus)
cornua majora et
corpus ossis hyoidis
(lower part)
a. carotis communis
a. carotis interna
(proximal part of pars
cervicalis)
5th arch is missing
cartilaginous parts of the
4th and 6th arch merge
into a common base of
the cartilages of the
larynx
arcus ortae from a.
carotis communis sin. to
a. subclavia sin
cartilago thyroidea,
cricoidea, arytenoidea,
corniculata,
cuneiformis
prox. part of a.subclavia dx.
a.pulmonalis sin., ductus
arteriosus
a.pulmonalis dx.
First pharyngeal arch
(arcus pharyngeus primus)
• 2 processes
– maxillary (cranially)
– mandibular (caudally)
• contains the Meckel´s cartilage (gives rise to malleus
and incus)
• formation of the lower jaw
– merging of the right and left mandibular process,
subsequent membranous ossification
Thomas W. Sadler, Langman´ Medical embryology, 10th edition
Second pharyngeal arch
(arcus pharyngeus secundus)
• cartilage (= Reichert´s cartilage)
• by merging of the right and left arch in the
midline a part of the body and lesser horns of
a hyoid bone are formed
Thomas W. Sadler, Langman´ Medical embryology, 10th edition
Third pharyngeal arch
• cornua majora + caudal part of corpus ossis
hyoideum
• innervation: n. IX
Fourth pharyngeal arch
• merges with the 6th arch
• cartilago cricoidea + thyroidea
• muscles of larynx, palate (apart from m.
tensor veli palatini), pharynx (apart from m.
stylopharyngeus)
• innervation: n. X (n. laryngeus sup.)
Fifth pharyngeal arch
• does not arise in human
Sixth pharyngeal arch
• merges with the 4th arch
• muscles of larynx
• innervation: n.X (n. laryngeus recurrens –
contains the fibres from n.XI)
Pharyngeal pouches (sacci pharyngei)
• human embryo has 5 pouches
• their endoderm gives rise to branchiogenic
organs
Thomas W. Sadler, Langman´ Medical embryology, 10th edition
First pharyngeal pouch
• recessus tubotympanicus (tubotympanic
recess)
– blind recess (toward the 1st pharyngeal groove)
• its end is broaden into the primitive tympanic
cavity
• medial part remains straight
– tuba auditiva Eustachii
• together with the 1st pharyngeal groove
participates in formation of an eardrum
(membrana tympanica)
Second pharyngeal pouch
• base of the palatine tonsil (tonsilla palatina)
• fossa supratonsillaris
http://biology.clc.uc.edu/fankhauser/labs/microbiology/strep_detection/strep_test.htm
Third pharyngeal pouch
• dorsal part
– inferior parathyroid bud
• ventral part
– thymic bud
• bases migrate caudally
Fourth pharyngeal pouch
• dorsal part
– superior parathyroid bud
• ventral part
– rudimentary
– ultimopharyngeal body (corpus ultimopharyngeum
/ ultimobranchiales)
• cells from the neural crest
• differentiate into the parafolicular C-cells of the thyroid
gland (calcitonin)
Pharyngeal grooves
• 4 paires of grooves are formed within the 5th
week
• dorsal part of the 1st groove persists as the
external acoustic meatus (meatus acusticus
externus)
– epithelium on the floor creates the outer surface
of an eardrum (membrana tympanica)
• other grooves come to lie in a depression 
sinus cervicalis (cervical sinus)
• sinus cervicalis is obliterated as the neck
develops, lateral cervical cysts may persist 
fistulae
Lateral cervical fistula
http://www.ultratwistersgym.com/Resources/Head/Head%20and%20Neck.html
http://journals.tums.ac.ir/full_text.aspx?org_id=59&culture_var=en
&journal_id=4&issue_id=1293&manuscript_id=11415&segment=en
Tongue - innervation
• n. V3
– n. lingualis
• n. VII
– chorda tympani
• n. IX.
• n. X.
Development of the tongue I
• 4th week: on the inner side of the pharyngeal pouches
(primordia lingualia)
• 1st arch: tuberculum impar (wears off) + 2 tubercula
lingualia lateralia  apex + dorsum linguae (n.V3)
• 2nd arch: copula (wears off) - n.VII - chorda tympani
(taste)
• 3rd-4th arch: eminentia hypobranchialis  radix linguae
(n.IX, n.X)
– sulcus terminalis (separates the body and the root of the
tongue)
• 4th arch epiglottis (n. X)
• muscles:
– from myotomes of the occipital somites (n. XII)
– from the 4th arch (n. X - m. palatoglossus)
Development of the tongue II
Thomas W. Sadler, Langman´ Medical embryology,
10th edition
Congenital abnormalities of the tongue
• cysts and fistulae – remnants of the
thyroglossal duct
• ankyloglossia (tongue-tie)
– short frenulum linguae
• macroglossia
• microglossia
• glossoschissis (= cleft tongue)
– rare, incomplete cleft
Ankyloglossia
http://www.ghorayeb.com/TongueTie.html
Macroglossia x Microglossia
http://www.consultantlive.com/display/article/10162/43839
http://dentallecnotes.blogspot.cz/2011/08/developmental-disturbances-of-tongue.html
Development of the thyroid gland
• the growth of the epithelium between tuberculum
impar and copula (later location of foramen
caecum)
• growths in front of the pharynx in a caudal
direction
• within the descent is connected to the tongue
thanks to ductus thyroglossus
• progressive descent in front of the hyoid bone and
the cartilages of the larynx
• within the 7th week gets to its final place in front
of the trachea
• gets functional at the end of the 3rd month
Congenital abnormalities of
the thyroid gland
• thyroglossal duct cysts
– may form anywhere along the course of it during
the descent of the thyroid gland from the tongue
• thyroglossal duct fistulae
– communication of the cysts with the outer space
• ectopic thyroid gland
– along the course of the descent
– most often at the root of the tongue
– this tissue may be functional
Thyroglossal duct cysts
http://www.surgical-tutor.org.uk/defaulthome.htm?tutorials/thyroglossal.htm~right
http://www.learningradiology.com/archives06/COW%20231Thyroglossal%20Duct%20Cyst/tgdccorrect.html
Processus pyramidalis glandulae
thyroideae
• the most common congenital abnormality
• along the course of the descent
• 40 %
http://www.anatomyatlases.org/AnatomicVariants/OrganSystem/Images/82.shtml
DiGeorge‘s syndrome
Aplasia thymoparathyroidea
microdeletion 22q11.2
1:3000
Development of the face I
• facial primordia appear at the end of the 4th week
(neural crest ectomesenchyme of the 1st pharyngeal
arch) around the stomodeum
– maxillary prominences laterally
– mandibular prominences caudally
– frontonasal prominence cranially
• on each side develop bilateral oval thickenings of
the surface ectoderm  nasal placodes
–they depress within the 5th week  nasal pits
–pits are bordered by horseshoe-shaped
elevations = medial and lateral nasal
prominences
Development of the face II
Thomas W. Sadler, Langman´ Medical embryology, 10th edition
Development of the face III
• maxillary prominences enlarge (cheeks and upper jaw)
and growth medially – pressing medial nasal
prominences to the midline, then they merge
• upper lip is formed by the maxillary prominences and
medial nasal prominences
• lower lip and jaw are formed by mandibular
prominences that merge in the midline
• nose arises from 5 sources:
– frontonasal prominence, 2 medial nasal
prominences, 2 lateral nasal prominences
Development of the
oral and nasal cavity
stomodeum
• a pit lined with ectoderm
boundaries:
• lower processes of the 1st pharyngeal arch –
mandibula
• on sides upper processes of the 1st pharyngeal arch
– maxilla
• frontonasal prominence with nasal placodes from
above ( pits, vesicles, open into the primitive oral
cavity), medial and lateral nasal prominences
• membrana oropharyngea (buccopharyngea) breaks
up on the 26th day
Development of the palate I
• primary palate
– from intermaxillary segment (by merging of both
medial nasal prominences)
•
•
•
•
lip component  philtrum
component for the upper jaw (carries 4 incisors)
palatine component (forms the primary palate)
passes continuously into the nasal septum (from the
frontonasal prominence)
• secondary palate
– by merging of the palatine processes of the maxillary
process (6th week)
– fusion with the primary palate (os incisivum) in front
Development of the palate II
Thomas W. Sadler, Langman´ Medical embryology, 10th edition
Separation of the oral and nasal cavity
Thomas W. Sadler, Langman´ Medical embryology, 10th edition
Cleft malformations of the
face and the palate I
• lack of fusion of the structures (1:550)
• anterior palate clefts (cheiloschisis, cheilognathoschisis)
– lateral cleft lip, clet upper jaw, cleft between the
primary and secondary palates
– partial or complete lack of fusion of the maxillary
prominence with the medial nasal prominence on one
or both sides
• posterior palate clefts (palatoschisis)
– cleft secondary palate, cleft uvula
• combination of clefts lying anterior as well as posterior to
the incisive foramen (cheilo-gnatho-palatoschisis)
• oblique facial clefts
– failure merging of the maxillary prominence with its
corresponding lateral nasal prominence
• median (midline) cleft lip
– rare abnormality
– incomplete merging of the two medial nasal
prominences in the midline
Cleft malformations of the
face and the palate II
http://blog.johnrchildress.com/2011/06/0
7/real-leadership-and-hope/
Thomas W. Sadler, Langman´ Medical embryology, 10th edition
http://www.craniofacial.net/cleft-lip-cleft-palate-only
Cleft malformations of the
face and the palate III
http://www.rodina.cz/clanek3188.htm
before
before
after
after
Development of the salivary glands
• epithelial pouches of the oral cavity (6th – 8th
week)
• the intergrowth into the adjacent
ectomesenchyme  its connective tissue
comes from the neural crest
• parenchyme ( secretion) comes from the
proliferating oral epithelium
– ectoderm  gl. parotis
– endoderm  gl. submandibularis et sublingualis
Development of the teeth I
• 6th week: proliferation of the oral epithelium
(ectoderm) into the surrounding
ectomesenchyme
– dental lamina (parallell to labiogingival crest)
– ectoderm → enamel organ
• outer enamel epithelium
• stratum intermedium, stellate reticulum
• inner enamel epithelium - ameloblasts
– ectomesenchyme → dental papilla - odontoblasts
Development of the teeth II
• production of the dentin
– odontoblasts: procollagen - predentin - dentin
• with thickening of the dentin layer, odontoblasts retreat into the
dental papilla, leaving a thin cytoplasmic processes – dental
processes (Tomes´ fibres)
• production of the enamel
– basal surface of the ameloblasts is becoming secretory:
• enamel matrix (organic - mineralisation)
• development of the roots
• dental epithelial layers penetrate into the underlying mesenchyme
 root sheath, mesenchymal cells on the outside of the tooth and
in contact with dentin of the root differentiate into cementoblasts
• permanent teeth
• secondary dental lamina is located lingually to the primary one
Development of the teeth III
Thomas W. Sadler, Langman´ Medical embryology, 10th edition