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Floor of the pharynx
Floor of the pharynx
• Development of the tongue.
• Development of thyroid gland.
Tongue• Largest single muscular organ in oral
cavity.
• It is important for taste sensation so it is innervated by 3 nerves : 7th ,9th
,10th cranial nerves.
• It is important in speech and its muscles are innervated by 12th
cranial nerve.
Development of tongue
MusclesMucosa
Posterior 1/3
Of tongue
Anterior2/3
Of tongue
Mucosa :
• It developed from endodermalfloor of the pharynx.
• In region of 1st pharyngeal arch.
• 3 Swellings appear:
Median swelling tuberculum imper
RT. and Lt. lateral swellings.
Anterior 2/3 of tongue:
Mucosa
•
• It develops from endodermal floor
of the pharynx.
• In regions of 2nd,3rd,4th pharyngeal arches.
• Only one swelling called hypo branchial eminence
• Anterior part post. Part of tongue.
• Posterior part. Epiglottis.
Posterior 1/3 of tongue:
Stages of tongue development
Muscles
• All muscles of tongue except: palatoglossus m.
are developed from
2nd,3rd,4th occipital
myotomes.
Congenital anomalies
Macro glossiaBifid tongue
Aglossia Micro glossia
Tie tongue
Thyroid gland• 1st endocrine gland.
• Very important gland.
thyroid H.is very important for
development of neonatal brain.
• Its development starts ;24th day of gestation.
Development of thyroid gland
• It developed from endodermalfloor of the pharynx.
• between 1st,2nd pharyngeal arches.
• Thyroid primordium thyroid diverticulum thyroglossalduct.
• Thyro glossal duct descends ant. To hyoid bone then ant. To larnyx.
• Its lower end proliferates to form thyroid lobes ithmus.
• Descent COMPLETE at 7th
gestational week
Development of cells of thyroid gland:
1. Thyroid follicles endoderm of thyroid diverticulum.
2. Para follicular cells endoderm of ultimo branchial body[ from 6th pharyngeal pouch].
: inner capsule ct. septa mesoderm.
N.B
Fate of thyroglossal duct
• Upper end foramen caecum.
apex of sulcus terminalis .
• Intermediate part degenerates.
• Lower end pyramidal lobe levatorglandulae thyroidae.
Pyramidal lobe
• In up to 50% of people.
• Persistance of the tower end of thyro glossal duct.
• Attached to hyoid bone by levator glandulaethyroidae.
Congenital anomalies
• thyro glossal duct if persists can form a sinus or fistulae or cyst.
1. Thyro glossal cyst: persistant of
a part of this duct.
Many sites for thyro glossal cyst.
Commonest site
2. Thyroid agenesis: apsentgland >>>>>>> cause cretinism.
3.Ectopic thyroid: common in the back of tongue >>>>>>>> lingual thyroid .