Download Pharyngeal Apparatus

DEVELOPMENT OF
TONGUE
THYROID GLAND, FACE AND
PALATE
By Dr Samina Anjum
PHARYNGEAL ARCHES
• Taste Buds
•
•
•
•
Anterior 2/3 tongue - Cranial nerve VII
Circumvallate papillae - Cranial nerve IX
Posterior 1/3 tongue - Cranial nerve IX
Most posterior part & Epiglottis - Cranial nerve X
TONGUE TIE
Development of Thyroid
• The thyroid gland is the first
endocrine gland to develop
in embryo.
• It begins to form about 24
days after fertilization
• It develops from a median
endodermal thickening in the
floor of a primordial pharynx
• Thickening soon forms a
small outpouching called
thyroid primordium
Cont….
• As the embryo and tongue
grow, the developing
thyroid gland descends in
the neck, passing ventral to
the developing hyoid bone
and laryngeal cartilages
• For a short time the thyroid
gland is connected to the
tongue by a narrow tube, the
thyroglossal duct,
disappears later
Cont…
• At first the thyroid
primordium is hollow but it
soon becomes solid and
divides into right and left
lobes.
• The two lobes are
connected by the isthmus
of the thyroid gland.
• Isthmus lies anterior to the
developing second and
third tracheal rings.
Cont…
• By seventh week it has reached
its final site in the neck
• The proximal opening of the
thyroglossal duct persists as a
small pit in the tongue, the
foramen cecum
• A pyramidal lobe extends
upward from the isthmus in
about 50% of people
• The pyramidal lobe and the
associated smooth muscle
represent a persistent part of the
distal end of the thyroglossal
duct
Thyroglossal Duct Cysts & Sinuses
Following infection of a cyst, a perforation of the skin
occurs forming a thyroglossal duct sinus
Lingual Thyroid
DEVELOPMENT OF FACE
STOMODIUM: Is the depression between five elevations. Opposed to the
primitive pharynx by buccopharyngeal membrane, which will break down
later, then stomodeum communicates with the foregut.
Craniofascial Defects
•
•
•
•
Treacher Collin’s syndrome
Robbin’s sequence
Digeorge anomaly
Goldenhar syndrome
First Arch Syndrome
Two Major types; both result in extensive facial
abnormalites
1. Treacher Collins Syndrome
2. Pierre Robin Syndrome
Treacher Collins Syndrome
• Autosomal dominant
trait/teratogens
• Malar hypoplasia
• Mandibular hypoplasia
• Down slanting palpepebral
fissures
• Malformed external ears
Pierre Robin Syndrome
• Genetic or
envoirmental factors
• Mandibular hypoplasia
• Micrognathia
• Cleft palate
Digeorge anomaly
•Disturbance of
cervical neural crest
migration.
•Absence of thymus
and parathyroid glands
•Immunological
deficiency,
Hypocalcaemia, Poor
prognosis
DEVELOPMENT OF PALATE
Intermaxillary Segment Forms
1. Labial Components (Philtrum)
2. Maxilla Component (Alveolus + 4 Incisors)
3. Palatal Component (Triangular Primary Palate)
Secondary Palate
Congenital malformations
1) cleft lip:
a. unilateral cleft lip: results
from
failure
of
the
maxillary prominence to
merge with medial nasal
prominence on the affected
side
b. bilateral cleft lip : results from
failure of the maxillary
prominences to merge with the
medial nasal prominence on
both sides
c. median cleft lip: results from
failure of the medial nasal
prominences to merge and
form the intermaxillary
segments
2)
oblique facial cleft:
results from failure of the
maxillary prominence to
fuse with the lateral nasal
prominence