Final answer:
Smooth muscle tissue regulates the movement of substances through body openings, is involuntary, and lacks voluntary control. It is found in the walls of internal organs and passages.
Step-by-step explanation:
The muscle tissue that forms valves to regulate the passage of substances through internal body openings is smooth muscle. Smooth muscle is found in the walls of internal organs such as the intestines, stomach, urinary bladder, and around passages like the respiratory tract and blood vessels. Unlike skeletal muscles which are under voluntary control, smooth muscle actions are involuntary and are controlled by the autonomic nervous system as well as various hormones and physiological factors. Each cell in smooth muscle tissue is spindle-shaped with a single nucleus and lacks striations. These characteristics allow smooth muscle to perform its role of regulating the movement of substances through body openings efficiently.