Anatomy of flexible endoscopes

Almost all flexible endoscopes are identical in terms of their structure and operation. The control body is the "head" of the endoscope, which houses all control components necessary to regulate its various functions. The light guide tube (universal or umbilical cord) connects the control body to the light guide connector; it houses wiring, tubing, fiber bundles and channels. The light guide connector is the component that plugs into the light source. It incorporates the connections for suction, CO2, air/water bottle, light fiber bundle, electrical contacts, ETO venting valve (fiberscopes only) and electrical connector (videoscopes).

The angulation system is divided into three areas: the control mechanism, the insertion tube and the bending section. The angulation wires run through all three areas, and are responsible for moving the distal tip of the insertion tube. On GI endoscopes there are wires that are directed up-down and left-right, and on endoscopes such as bronchoscopes and cystoscopes, there is a wire that moves just up-down. The system is also composed of angulation knobs and locks located on the control body, and coiled wires that run the length of the insertion tube. These wires stretch with repeated use, which results in decreased movement at the distal tip, and extra "play" within the control knobs over time. The operator manual contains a diagram for angulation specifications so the user knows when it’s time to get an angulation adjustment repair or replacement.

Lubricant within the control body facilitates smooth movement of the components (knobs, angulation wires). If fluid enters the control body and contacts the lubricant, the lubricant hardens. This makes it difficult to turn the control knobs to direct the distal tip. With extreme stiffness of the controls, a grinding sound may be heard. If the knobs do not move smoothly, and you hear a grinding noise, consider the possibility of a fluid invasion having occurred.

The insertion tube is the portion of the endoscope inserted into the patient; it has graduated markings that act as reference points during the procedure. The bending section is the soft, flexible rubber sheath that covers the distal section of the scope; located at the end of the insertion tube, it is the working component and a delicate area of the scope. This section is particularly prone to damage. The insertion tube and bending section contain circular metal bands (the metal coil), that run the length of the scope to protect the internal components. A woven wire mesh covers the metal coil. The outer sheath covers the mesh, and the cover material changes to a softer rubber at the bending section, for ease of insertion. The adhesive that secures the bending rubber will wear over time. The durability of a repair to this section is determined by the quality of adhesives used by the repair company.

The strain relief boot is located on the upper section of the insertion tube, and at both ends of the light guide cord. The boot supports and stabilizes the connection between rigid components and the light guide tube and insertion tube. The boot helps prevent "buckling" at the attachment in these critical areas.

In a fiberscope, the image is viewed directly through an eyepiece. Fiber bundles carry the light for illumination, or the image for viewing. Each fiber bundle contains 3,000 to 50,000 individual glass fibers which are smaller than the diameter of a human hair. The fibers are housed inside a protective sheath.

In the video image system, the image bundle is replaced with the video camera unit. The video lens system reduces and focuses the image onto the surface of an electronic chip. The video chip (CCD) is located in the distal tip of the insertion tube. The CCD chip is attached to small wires and transforms light into electrical charges called "signals." The signals are then carried through the load wires to the electrical connector of the endoscope and produce the image on the video screen. Since this entire system is interdependent, it is important to always protect the distal tip to prevent damage to the lens and video chip.

The endoscope’s channel design is its "plumbing" system. It includes two basic components: air and water channels. The air channel carries the flow of air through the endoscope to inflate hollow cavities within the body. The water channel carries the flow of water through the endoscope to clean the lens or irrigate an area where the image needs to be improved for proper inspection. The biopsy/suction channel originates at the suction port on the light guide connector; travels to the control body, and then down the insertion tube.