Final answer:
The urinary bladder is the hollow organ characterized by elastic fibers and involuntary muscle tissue. It is specifically designed to expand and contract due to its smooth muscle composition and transitional epithelium, accommodating varying volumes of liquid without losing tone.
Step-by-step explanation:
The hollow organ with elastic fibers and involuntary muscle is known as the urinary bladder. The urinary bladder is comprised of smooth muscle called the detrusor muscle, which is not under voluntary control and is characterized by a lack of striations. This musculature is implicated in the organ's ability to expand and contract, accommodating a significant range of volume changes. The bladder's interior is lined with transitional epithelium, specialized to handle the fluctuating volumes without tearing, changing from a columnar to a squamous appearance as it stretches. The organ's ability to maintain a tone even during the empty state helps prevent it from becoming flaccid.
In summary, the urinary bladder is an example of a hollow organ composed of involuntary muscle designed for distensibility and constant tone, illustrating the unique structural and functional adaptations of organs that are part of the body's systems for storing and conveying fluids.