1. No category

Head & neck region of 4- week human embryo resembles
fish gill region (branchial apparatus) --- no gills in human.
* pharyngeal arches (1-6 pairs) * pharyngeal pouches
* phargeneal grooves
* phargeneal membranes
Pharyngeal Apparatus
婁培人
• 1st pharyngeal arch
Lateral
Dorsal view
Lateral view
Development of
pharyngeal
apparatus (咽弓)
-thyroid gland
-tongue
-salivary gland
-face
-nasal cavities
-palate
Ventral view
maxillary prominence
maxilla, zygomatic
bone, vomer
mandibular
prominence
mandible, squamous
temporal bone
23 days
ruptured
oropharyngeal
membrane
20 week
26 days
• 2nd pharyngeal arch
Primordial mouth
(stomodeum原口)
Formation of cervical sinus
32 days
33 days
cervical sinus
Pharyngeal arch components
41 days
* Each arch
--Ectoderm-mesenchyme (core)-endoderm
neural crest cells⇒ skeleton
mesoderm ⇒ muscles, vessels
Adult derivatives of arch cartilages
24 wks
4 wks
1st
2nd
Malleus, incus,
Stapes, styloid process,
anterior ligament of stylohyoid ligament,
malleus, sphenolesser cornu &
mandibular ligament, superior part of body of
mandible.
hyoid bone.
3rd
4th & 6th
Greater cornu &
inferior body of
Laryngeal
hyoid bone.
cartilages.
3rd & 4th arches
mesenchyme in
hypopharyngeal eminence
cartilage of epiglottis.
Definitive structures
formed by various
pharyngeal arches
Muscles derived from pharyngeal arches
Derivatives of pharyngeal arch nerves
20 wks
Superficial distribution of CN V
4 wks
maxillary
division
4 wk
mandibular
division
20 wk
fetus
1st:
muscles of
mastication
2nd:
muscles of
facial
expression
4 & 6th:
3rd:
stylopharyngeus laryngeal, pharyngeal muscle
Deep distribution of
sensory nerves
pharyngeal pouches
Balloon-like
diverticula
1st , 2nd , 3rd,
4th, 5th pouch
(rudimentary)
I
II
III
III
thymus
7 weeks
IV
IV
6 wk
5 wk
*
1st pouchelongate tubotympanic recess
tympanic membrane
tympanic cavity, mastoid antrum
pharyngotympanic tube (auditory tube)
2nd pouch-
*
tonsillar sinus, palatine tonsil
3rd pouchinferior parathyroid gland; thymus
*
*
4th pouch-
*
20 week
Pharyngeal Grooves
1st groove-external acoustic meatus
2-4 grooves⇒ cervical sinus⇒ obliterated
superior parathyroid gland;
ultimobranchial body, fuses with thyroid gland
parafollicular cells (C cells)--calcitonin
Pharyngeal Membrane
• endoderm of pouch+ectoderm of pharyngeal
groove
24 days
4 wk
*
7 wk
Pharyngeal apparatus
1st pharyngeal membrane
• Arches-[1-6]
-cartilages bones & cartilages.
-muscles
facial expression, mastication
-nerves
CN 5,7,9,10.
-aortic arches
arteries of head & neck.
• Pouches—tympanic cavity, palatine tonsil, sup.
& inf. parathyroid gland, C cells, thymus.
• Membranes– tympanic membrane.
• Grooves– external acoustic meatus.
7 weeks
Anomalies of head and neck
Possible sites of branchial cysts and
openings of branchial sinuses & fistulas
*
2nd pharyngeal groove
First Arch Syndrome
Results from insufficient migration
of neural crest cells into the 1st arch
during the 4th week.
-Deformed auricle
-preauricular appendage
-defect in cheek
-hypoplasia of mandible
-macrostomia
4 wks
Development of
Thyroid Gland
4 wks
Development of
Thyroid Gland
- a median
endodermal
thickening
*
*
5 wks
6 wks
*
adult
*
Congenital anomalies of thyroid gland,
parathyroid gland, thymus
Ectopic Thyroid Gland
≈7 wks
Pyramidal lobe:
in 50% people
Thyroglossal duct cyst
- may form anywhere along the course
followed by the thyroglossal duct during
descent of the primodial thyroid gland
from the tongue
4th wk
Development of Tongue
3 lingual swelling (1st arch)
Copula (連合) (2nd arch)
Hypopharyngeal eminence (3rd & 4th)
Lateral lingual swelling
Median lingual swelling
Hypopharyngeal
eminence
Midline groove
Midline groove: fusion of distal tongue buds is indicated by a middle groove
Terminal sulcus: the line of fusion of ant. and post. parts of tongue
8th wk Lingual papillae
vallate & foliate
CN IX
Chorda tympani
fungiform
filiform (10-11 wk)
Taste buds (11-13 wk)
CN X
Development of Salivary Glands
*solid epithelial proliferations
(from primordial oral cavity)
*connective tissue
(from neural crest cells)
CN IX
Parotid glands
early 6th week
Submandibular glands
late 6th week
Sublingual glands
8th week.
Palatoglossus (CN X)
Chorda tympani
Development of Face
• 5 facial primordia (prominence
around the stomodeum)-4-8weeks
1 frontonasal prominence
forehead, nose
2 maxillary prominences
upper lip, upper cheek
2 mandibular prominences
chin, lower lip, lower cheek
30-32 days
medial nasal prominence
lateral nasal prominence
Development of Nasal Cavity
The end of 4th week—
Nasal placodes: bilateral oval thickening of surface ectoderm
pits
nasal sacs
nasal cavities
nasal
Medial
Lateral
28 days
33 days
Mesenchyme in
the margins
of the placodes
proliferates
*
6 auricular hillocks(丘)(primordia of auricles) appear.
The nasolacrimal duct develops from a rodlike
thickening of the ectoderm in the floor of
nasolacrimal groove
5 wks
B
C
54 days
*
Merging of medial nasal prominences
Philtrum of the lip
segment
*
Primary palate
Intermaxillary
10 weeks
Developing
maxilla
*
E
* Median palatal process
(intermaxillary segment)
F
* Philtrum of lip
Primordium of
premaxillary part
of maxilla
Summary of Facial Development
FNP forehead and dorsum & apex of nose
Lateral nasal prominences sides of nose
Medial nasal prominences nasal septum
Maxillary prominences upper cheek & most upper lip
Mandibular prominences chin, lower lip, lower cheek.
Bones develop from the mesenchyme in facial
prominences.
1st Arch -Maxillary prominence maxilla, zygomatic bone
& squamous part of temporal bone.
-Mandibular prominence mandible.
-Muscles of mastication.
2nd Arch
- Superior hyoid bone, styloid process of temporal bone.
- Muscles of facial expression.
14 weeks
Oronasal membrane
-ruptures by 6th week, the continuity of nasal and oral cavities
Primordial choanae
- continuity between nasal and oral cavities
post. to primary palate
*
5 wks
6 wks
7 wks
12 wks
Development of Palate
hard palate
palatine processes of maxillae+
horizontal plates of palatine bones
Primary palate
* the deep part of intermaxillary segment of
the maxilla ⇒ median palatine process ⇒
primary palate ⇒the premaxillary part of
maxilla (a small part in adult hard palate)
Secondary palate
* internal aspects
of maxillary prominences ⇒ lateral
palatine processes
+ palatine bones
hard & soft palate
lateral palatine processes
--approach each other & fuse in the median
plane.
--fuse with nasal septum & posterior part of
primary palate.
Roof of mouth
6th wk
Development of nasal septum
Gingiva
Developing gingiva
7-8th wk
medial nasal prominences
*
*
12 weeks
roof of mouth
Nasopalatine canal (in the median plane of the palate between premaxillary part
of maxilla and palatine process of maxilla) ⇒ incisive fossa in adult
Palatal process
development during
the 8th week
(frontal sections)
54 days
20 wk fetus
Young
adult
the end of 8th wks
Various types of cleft lip and palate
Normal
Unilateral cleft of
secondary palate
Bilateral cleft of
secondary palate
5 wks
Cleft lip & primary palate
*
*
6 wks
Unilateral cleft
Bilateral cleft
Cleft lip, primary palate & secondary palate
7 wks
10 wks
Embryological
basis of complete
unilateral cleft lip
Face, Nasal Cavities, Palate
Face develops from 5 facial prominences: FNP,
2 Maxillary & 2 Mandibular (1st Arch).
Nasal Cavities develops from nasal placode
[FNP].
Palate
deep part of intermaxillary segment of the maxilla
⇒ median palatine process ⇒ primary palate ⇒the
premaxillary part of maxilla (a small part in adult
hard palate)
internal aspects of maxillary prominences ⇒
lateral palatine processes (secondary palate)
+ palatine bones
hard & soft palate