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 .