PHARYNGEAL ARCHES This diagram shows the development of pharyngeal arches
. At what stage of development do these structures appear? . Why were these structures called branchial arches initially? . How many pharyngeal arches develop in an embryo? . Which pharyngeal arch does not give rise to any derivatives? . List the three components which make up the pharyngeal arches. . What does each component form? . Which two structures contribute towards the formation of the first pharyngeal arch? . Which pharyngeal arches are responsible for the formation of the three bony ossicles of the ear? This diagram shows the development of the pharyngeal pouches
. What do each of the pouches form? . What does the tubotympanic recess contribute to? This diagram shows the embryonic development of the tongue
. At what stage of development does the tongue develop? . From which pharyngeal arch does the anterior two-thirds of the tongue develop? . Which pharyngeal arches are responsible for the formation of the posterior third of the tongue? . Identify the abnormality depicted in the two pictures. . Identify the abnormality depicted in the two pictures. This diagram shows the formation of the thyroid
. From which germ layer does the thyroid gland derive? . Where does the thyroid gland originate? . When does the thyroid gland become functional? This diagram shows the migratory pathway of the thyroid gland from foramen cecum
. Describe this pathway. This diagram shows the formation of thyroglossal cysts
. What results in the formation of these cysts? . At what level in the neck region are these cysts commonly found? Short essay questions
. Describe the embryonic development of the tongue. (8 marks)
. Describe the embryonic development of the thyroid gland. (5 marks)
Multiple choice questions
. Cartilage of the second pharyngeal arch
a. Is known as Meckel’s cartilage. b. Gives rise to the stapes of the ear. c. Gives rise to the styloid process of the temporal bone. d. Gives rise to the malleus of the ear. e. Is also known as hyoid arch cartilage.
. With regards to the third pharyngeal pouch
a. The ventral wing forms the thymus. b. The dorsal wing forms the superior parathyroid gland. c. It gives rise to the ultimobranchial body. d. It gives rise to the palatine tonsil. e. It differentiates into the tubotympanic recess. Match the embryonic structures in column A with their frontrunners in column B
COLUMN A COLUMN B
1) Meckel’s cartilage a) Tubotympanic recess 2) Second pharyngeal arch b) External auditory meatus 3) Second pharyngeal pouch c) Incus and malleus 4) First pharyngeal groove d) Stapes 5) First pharyngeal pouch e) Palatine tonsil 6) Intra embryonic mesoderm f) Parafollicular cells 7) Lateral lingual swellings g) Inferior parathyroid gland 8) Third pharyngeal pouch h) Posterior third of the tongue 9) Copula i) Skeletal muscles 10) Ultimobranchial body j) Body of tongue