The term “obturator” appears in different contexts, referring to both a specific part of the human body and various medical tools. In anatomy, an obturator describes a particular structure associated with the pelvis. In a medical setting, an obturator refers to a device designed to close an opening or assist in a procedure. This dual usage highlights the importance of clarifying its application.
The Anatomical Obturator
In the human body, “obturator” primarily refers to an anatomical region in the hip. This area centers around the obturator foramen, a large, oval-shaped opening found in each hip bone. This opening is bordered by the ischium and pubis, two bones that form part of the pelvis. The name “obturator” originates from the Latin “obturo,” meaning “to stop or block up,” fitting its nature as it is largely covered by muscles and a fibrous sheet known as the obturator membrane.
Two muscles, the obturator internus and obturator externus, are closely associated with this foramen. The obturator internus muscle originates from the inner surface of the pelvic wall, encompassing the obturator foramen, and attaches to the greater trochanter of the femur, a prominent bony projection on the upper thigh bone.
The obturator externus muscle arises from the outer surface of the obturator foramen and its membrane. Like its counterpart, it also inserts onto the greater trochanter of the femur. The obturator nerve also traverses this region, passing through the obturator canal, a passageway within the upper part of the obturator foramen, to reach the medial compartment of the thigh.
How the Anatomical Obturator Functions
The muscles and nerve associated with the obturator foramen play distinct roles in lower limb function and sensation. The obturator internus muscle contributes to the external rotation of the thigh when the hip is extended. When the hip is flexed, this muscle assists in abducting the femur, moving the leg away from the body’s midline. It also plays a role in maintaining the stability of the femoral head within the hip socket.
The obturator externus muscle primarily acts to externally rotate the hip, whether the hip is in a neutral or flexed position. This muscle can also aid in the adduction of a flexed hip, drawing the leg toward the body. Both the obturator internus and externus muscles are categorized among the short external rotators of the hip, working in concert with other muscles to facilitate a wide range of hip movements.
The obturator nerve supplies motor signals and sensory information. It provides motor innervation to the obturator externus muscle, as well as several other muscles in the medial compartment of the thigh, allowing for movements like hip adduction. The obturator nerve also carries sensory information from the skin on the inner aspect of the thigh. The coordinated actions of these muscles, guided by the obturator nerve, contribute to the stability of the hip joint and the broad range of motion required for walking and other lower limb activities.
Obturators as Medical Tools
Beyond its anatomical meaning, the term “obturator” also refers to various medical devices. In this context, an obturator is a tool designed to close or block an opening, or to facilitate the insertion of other instruments. One common application is in dentistry, where a dental obturator might be used as a prosthetic device to close an opening in the palate.
In surgical settings, obturators serve a different but related purpose. They are often used to block the opening of an instrument being introduced into the body, acting as a guide or a protective tip. For instance, a surgical obturator might be employed to guide a trocar through tissue during laparoscopic procedures, or to create access for a bone marrow biopsy. These devices are designed to minimize tissue disruption as instruments are advanced, or to securely seal an anatomical opening.