The pharyngeal pouches are balloonlike diverticula that formed on the endodermal side between the pharyngeal arches.The pairs of pouches develop in a craniocaudal sequence between the arches
During the embryonic development pharyngeal pouches develop between the branchial arches .The first pharyngeal pouches pouch is situated between the first and second branchial arches. There are 4 pairs, the 5th pouch is absent or very small.The pharyngeal pouches form on the endodermal side between the pharyngeal arches and the pharyngeal grooves or clefts form the lateral ectodermal surface of the neck region to separate the arches.The endoderm of the pharyngeal pouches and the ectoderm of the branchial grooves contact each other to form the branchial membranes and this will seperate the pharyngeal pouches and the branchial grooves.
The primordial pharynx , derived from the foregut it widens cranially where it joins the primordial mouth or stomodeum.It narrows caudally where it joins the esophagus
Derivatives of the 1st pharyngeal pouch
1st pharyngeal pouch expands into a tubotympanic recess
The expanded distal portion of the recess contacts the 1st branchial groove .It is the only branchial membrane to persist in the adult.This will be contributing to the formation of the tympanic membrane or eardrum.
Only the 1st branchial groove persists in the adult as the external acoustic meatus .
The tubotympanic recess gives rise to the tympanic cavity and the mastoid antrum.
Connection between the tubotympanic recess and the pharynx elongates to form the auditory tube.
Mandibular nerve supply derivatives of first pharyngeal pouch
Derivatives of first pharyngeal pouch
2nd pharyngeal pouch contributes to the formation of the following Palatine tonsil and epithelial lining of the fauces.The endoderm of the pouch proliferates and grows into the underlying mesenchyme,the central parts of these buds form crypts .The endoderm of the pouch forms the surface epithelium and the lining of the tonsillar crypts. At about 20 weeks the mesenchyme around the crypts differentiates into lymphoid tissue.These tissues soon organize into the lymphatic nodules of the palatine tonsil
2nd pouch derivatives are supplied by the facial nerve.
3rd pharyngeal pouch has dorsal and ventral wings and contributes to the formation of the inferior parathyroid glands (week 5- bulbar portion and the thymus (elongate portion). which migrate inferiorly past the superior parathyroid glands of the 4th pouch.
Derivatives of this pouch is supplied by glossopharyngeal nerve .
Derivatives of 3rd pharyngeal pouch
4th pharyngeal pouch contributes to the formation of the superior parathyroid gland (bulbar portion) and the parafollicular cells or calcitonin cells of the thyroid gland (elongate portion form ultimobranchial body).
Superior laryngeal nerve supply the derivatives of this pouch
Derivatives of 4th pharyngeal pouch
It is a rudimentary structure and becomes part of the fourth pouch contributing to formation of thyroid C-cells.
Derivatives of the 6th pharyngeal pouch
The sixth pharyngeal pouch does not exist. The fourth and sixth arches contribute to the formation of the musculature and cartilage of the larynx. These structurs are supplied by Recurrent laryngeal nerve.
During the embryonic development pharyngeal pouches develop between the branchial arches .The first pharyngeal pouches pouch is situated between the first and second branchial arches. There are 4 pairs, the 5th pouch is absent or very small.The pharyngeal pouches form on the endodermal side between the pharyngeal arches and the pharyngeal grooves or clefts form the lateral ectodermal surface of the neck region to separate the arches.The endoderm of the pharyngeal pouches and the ectoderm of the branchial grooves contact each other to form the branchial membranes and this will seperate the pharyngeal pouches and the branchial grooves.
The primordial pharynx , derived from the foregut it widens cranially where it joins the primordial mouth or stomodeum.It narrows caudally where it joins the esophagus
Derivatives of the 1st pharyngeal pouch
1st pharyngeal pouch expands into a tubotympanic recess
The expanded distal portion of the recess contacts the 1st branchial groove .It is the only branchial membrane to persist in the adult.This will be contributing to the formation of the tympanic membrane or eardrum.
Only the 1st branchial groove persists in the adult as the external acoustic meatus .
The tubotympanic recess gives rise to the tympanic cavity and the mastoid antrum.
Connection between the tubotympanic recess and the pharynx elongates to form the auditory tube.
Mandibular nerve supply derivatives of first pharyngeal pouch
Derivatives of first pharyngeal pouch
- Middle ear
- Mastoid antrum
- Inner layer of the tympanic membrane
- The endoderm lines the future auditory tube
2nd pharyngeal pouch contributes to the formation of the following Palatine tonsil and epithelial lining of the fauces.The endoderm of the pouch proliferates and grows into the underlying mesenchyme,the central parts of these buds form crypts .The endoderm of the pouch forms the surface epithelium and the lining of the tonsillar crypts. At about 20 weeks the mesenchyme around the crypts differentiates into lymphoid tissue.These tissues soon organize into the lymphatic nodules of the palatine tonsil
2nd pouch derivatives are supplied by the facial nerve.
Derivatives of second pharyngeal pouch
- Palatine tonsil
- Epithelial lining of the fauces
- Middle ear
3rd pharyngeal pouch has dorsal and ventral wings and contributes to the formation of the inferior parathyroid glands (week 5- bulbar portion and the thymus (elongate portion). which migrate inferiorly past the superior parathyroid glands of the 4th pouch.
Derivatives of this pouch is supplied by glossopharyngeal nerve .
Derivatives of 3rd pharyngeal pouch
- Derivatives of the dorsal wings include the inferior parathyroid glands,
- Ventral wings fuse to form the cytoreticular cells of the thymus
4th pharyngeal pouch contributes to the formation of the superior parathyroid gland (bulbar portion) and the parafollicular cells or calcitonin cells of the thyroid gland (elongate portion form ultimobranchial body).
Superior laryngeal nerve supply the derivatives of this pouch
Derivatives of 4th pharyngeal pouch
- Superior parathyroid glands
- Ultimobranchial body which forms the parafollicular C-Cells of the thyroid gland
- Musculature and cartilage of larynx (along with the sixth pharyngeal arch).
It is a rudimentary structure and becomes part of the fourth pouch contributing to formation of thyroid C-cells.
Derivatives of the 6th pharyngeal pouch
The sixth pharyngeal pouch does not exist. The fourth and sixth arches contribute to the formation of the musculature and cartilage of the larynx. These structurs are supplied by Recurrent laryngeal nerve.
