The lesser pelvis, also known as the true pelvis, is the lower part of the pelvic cavity located below the pelvic brim. It is bordered by the pelvic bones and contains important structures such as the bladder, rectum, and reproductive organs. The lesser pelvis plays a crucial role in childbirth, as it provides the passage through which a baby moves during delivery. The shape and size of the lesser pelvis can vary between individuals and is often categorized into different types, such as the gynecoid, android, platypelloid, and anthropoid shapes. These variations can influence factors like labor and delivery, making the study of the lesser pelvis important in fields like obstetrics and gynecology.