Which of the following structures would allow you to know that you were upside down, even if you were in total darkness? a. utricle and saccule c. semicircular canals b. cochlea d. tectorial membrane.

The ear has three main parts: the outer ear, the middle ear and the inner ear. The structures mentioned in the exercise (utricle and saccule, semicircular canals, cochlea, and tectorial membrane) are all parts of the inner ear. The function of each structure is different.

a. Utricle and saccule: These are small sacs within the inner ear that contain small calcified stones called otoliths. They are sensitive to linear acceleration and gravity, helping us detect changes in head position and movements. c. Semicircular canals: There are three semicircular canals, which are oriented orthogonal to each other and filled with a fluid called endolymph. They are responsible for detecting rotational movements or angular acceleration. b. Cochlea: The cochlea is a spiral-shaped tube that converts sound waves into electrical signals, which are then transmitted to the brain. It is responsible for helping us hear and doesn't play a role in maintaining balance. d. Tectorial membrane: The tectorial membrane is a gel-like structure in the organ of Corti, within the cochlea. It plays a role in the process of converting sound waves into electrical signals but is not involved in maintaining balance or detecting body orientation.

Based on their functions, the semicircular canals (c) are the structures that help us detect the orientation of our body when rotating our head or when we are upside down. Although the utricle and saccule play a role in detecting linear acceleration and head position changes, they are less sensitive to specific body orientations. So, the correct answer is: c. semicircular canals