The internal structures of sex dolls have seen significant advancements, aiming to replicate human anatomy and movement as closely as possible. Most high-quality dolls feature a skeletal frame made of metal or durable composites, providing stability and flexibility. Joints are often designed to allow a wide range of natural poses, with mechanisms that mimic human joint movement, such as shoulders, elbows, hips, and knees. Some models incorporate internal cavities and gel-filled areas to simulate the weight and softness of flesh, enhancing tactile realism. For added realism, certain dolls include internal wiring or servos for remote-controlled movements or voice responses, although these are more common in highly advanced models. The internal design also considers hygiene, with removable or washable components that facilitate cleaning and maintenance. While no internal structure can perfectly replicate the complexity of human musculature and tissue, modern engineering has achieved impressive levels of realism. The degree of authenticity varies depending on the doll’s price point and technological features. Nonetheless, current internal structures successfully provide natural movement, support, and a convincing feel that enhances the overall experience.