This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pectoral Region, Axilla & Brachial Plexus, Subject name: Anatomy
[{'content': 'Axillary sheath is an extension of? \nSelect and explain. \nA. Pre tracheal fascia, B. Prevertebral fascia, C. Carotid sheath, D. Investing layer of deep cervical fascia', 'role': 'user'}, {'content': "Answer: B \nExplanation: ANSWER: (B) Prevertebral fasciaREF: Gray's anatomy 40th ed ch: 28, 46The axillary sheath is a fibrous sheath that encloses the first portion of the axillary artery, together with the axillaryvein andthebrachial plexus. It is an extension of the prevertebral layer of the deep cervical fasciaDeep fascia in the neck is organized into an investing layer, prevertebral fascia, and pretracheal fascia. The carotid sheath is a non-membranous layer of fascia that is conventionally described as part of the deep cervical fascia.", 'role': 'assistant'}]