bladder
胱 refers specifically to the bladder, the organ that stores urine.
胱 combines the flesh radical ⺼ (body part) with 光, which likely provides the sound コウ. The character was created to name the bladder as a bodily organ.
The flesh radical ⺼ signals a body part, and 光 (light) suggests something that fills and empties like a container. Imagine the bladder as a fleshy pouch that holds liquid until it's time to release it.
For コウ, picture a bladder glowing with light (光) as it fills: the light cues コウ, and the flesh radical reminds you it's a body part.
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urinary bladder; urinary cyst; vesica urinaria; bladder
artificial bladder; artificial urinary bladder
acute cystitis
sphincter muscle of urinary bladder
cystitis; inflammation of the bladder
bladder cancer
bladder stone; vesical calculus; cystolith
cystography; cystogram
cystoscope