This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
[{'content': 'The tonsils are derived from which of the following branchial pouch? \nSelect and explain. \nA. 1st branchial pouch, B. 2nd branchial pouch, C. 3rd branchial pouch, D. 4th branchial pouch', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Endoderm of the second pharyngeal pouch forms the stratified squamous, nonkeratinized epithelium lining the tonsillar crypts on pharyngeal surface of tonsil. The mesoderm forms lymphoid tissue, fibrous capsule, and connective tissue elements of tonsil. Pharyngeal pouch derivatives:First pouch: eustachian tube, tympanic cavity, endodermal lining of eardrumSecond pouch: palatine tonsilsThird pouch: thymus and inferior parathyroid glandsFouh pouch: superior parathyroid, pa of thymusFifth pouch: parafollicular cells of thyroidRef: Textbook of Clinical Embroyology By Vishram Singh page 116. A Textbook of Neuroanatomy By Maria Patestas.', 'role': 'assistant'}]