Floor of the pharynx
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The floor of the pharynx gives rise to two structures - the tongue and thyroid gland. The tongue develops from the endoderm of the pharyngeal floor. Its anterior two-thirds come from the first pharyngeal arch while its posterior one-third comes from the second, third, and fourth arches. The muscles of the tongue, except for one, develop from occipital myotomes. The thyroid gland also arises from the pharyngeal floor endoderm between the first and second arches. It descends through the thyroglossal duct until reaching its final location in the neck by the seventh gestational week. Persistence of parts of the thyroglossal duct can result in congen
![Development of cells of thyroid gland:
1. Thyroid follicles
diverticulum.
endoderm of thyroid
2. Para follicular cells
endoderm of ultimo
branchial body[ from 6th pharyngeal pouch].
N.B
: inner capsule ct. septa
mesoderm.](https://image.slidesharecdn.com/floorofthepharynx-131109155038-phpapp02/85/Floor-of-the-pharynx-13-320.jpg)
Floor of the pharynx
- 1. Floor of the pharynx
- 2. Floor of the pharynx Development of the tongue. Development of thyroid gland.
- 3. 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.
- 4. Development of tongue Muscles Mucosa Anterior 2/3 Of tongue Posterior 1/3 Of tongue
- 5. Mucosa : Anterior 2/3 of tongue: It developed from endodermal floor of the pharynx. In region of 1st pharyngeal arch. 3 Swellings appear: Median swelling tuberculum imper RT. and Lt. lateral swellings.
- 6. Mucosa Posterior 1/3 of tongue: 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 Posterior part. post. Part of tongue. Epiglottis.
- 7. Stages of tongue development
- 8. Muscles All muscles of tongue except: palatoglossus m. are developed from 2nd,3rd,4th occipital myotomes.
- 9. Congenital anomalies Macro glossia Bifid tongue Tie tongue Aglossia Micro glossia
- 10. 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.
- 11. Development of thyroid gland It developed from endodermal floor of the pharynx. between 1st,2nd pharyngeal arches. Thyroid primordium thyroid diverticulum thyroglossal duct. 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
- 13. Development of cells of thyroid gland: 1. Thyroid follicles diverticulum. endoderm of thyroid 2. Para follicular cells endoderm of ultimo branchial body[ from 6th pharyngeal pouch]. N.B : inner capsule ct. septa mesoderm.
- 14. Fate of thyroglossal duct Upper end foramen caecum. apex of sulcus terminalis . Intermediate part degenerates. Lower end pyramidal lobe glandulae thyroidae. levator
- 15. Pyramidal lobe In up to 50% of people. Persistance of the tower end of thyro glossal duct. Attached to hyoid bone by levator glandulae thyroidae.
- 16. 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
- 17. 2. Thyroid agenesis: apsent gland >>>>>>> cause cretinism. 3.Ectopic thyroid: common in the back of tongue >>>>>>>> lingual thyroid .