Small Diameter Flexible Endoscope Anatomy: The Outside
Each small diameter flexible endoscope has five basic sections that make up the outer shell and structure of the scope. Each of these sections is constructed differently but all provide a protective outer layer and are hollow inside. The hollow areas inside contain the delicate internal systems.
Light Guide Connector
The light guide connector is the solid end of the scope, which connects to the light source or video cart system. It is typically constructed of metal or molded plastic components and has no moveable parts. Some models have detachable light cables and for those scopes, the light guide connector is on one end of the detachable cable. Other models may utilize a small, battery light source that connects directly to the control body of the scope. Very little wear and tear occurs in this area of the scope. Damage here is typically from poor handling practices.
Light Guide Tube
Sometimes called the universal cord, this tube runs from the light guide connector to the control body of the scope. This hollow flexible tube is comprised of multiple layers of material. The innermost layer is a flat metal coil covered with stainless steel mesh. Over the mesh is the visible rubber tubing. The outermost layer is a very thin, clear chemical-resistant polymer coating. This tubing is fluid resistant and protects the light transmission device inside. The metal structure can withstand loose coiling and minimal external pressure. However, over-coiling or twisting the tube will damage the metal structure and the light fibers inside. Additionally, it is easy to pinch the tube if pressure is applied from items stacked on top to the tube. The light guide tube of video scopes also houses the wiring harness for the remote switches and CCD.
For scopes with detachable light cables, the light guide tube may not always have an internal metal coil and may provide even less protection from coiling, twisting, or pinching actions.
Control Body
This area of the instrument contains the physician controls. These typically include the angulation control lever, the suction valve, the remote video switches on video scopes, the eyepiece on fiberoptic scopes, and the biopsy port. This section is comprised mostly of metal and molded plastic components that protect the internal components.
Insertion Tube
The insertion tube is the long flexible tube inserted into a natural orifice of the patient's body. The length and diameter of the insertion tube varies by model and original intended use. It is constructed similarly to the light guide tube in that it has a metal coil skeleton wrapped with steel mesh fibers. Covering these is a rubber tube and usually includes a very thin, clear polymer outer coating. The polymer coating provides the shiny, chemical-resistant seal. The rubber tube is often marked with lines and or numbers representing metric distances from the distal tip. These markings allow the physician to know exactly how far into the body the scope has been inserted.
The insertion tubes are hollow and protect the delicate internal components contained inside. The thicknesses of the metal coil and of the rubber tube are dependent upon the overall diameter of the insertion tube. The smaller the diameter of the tube, the thinner the metal and rubber materials become. As a result, the insertion tubes are more prone to buckles, dents, and internal component damage.
Depth of insertion from the distal tip.
Bending Section
The bending section is the area of the scope at the distal end of the insertion tube. This section rotates when the angulation control lever is manipulated. The overall length of the bending section varies by model but is usually around 2-3" long.
The bending section is most commonly constructed of articulating metal ribs riveted together, but some manufacturers use tabs instead of rivets or cut tubing made of a memory metal to create a bending section. Regardless of the construction, this inner skeleton structure allows the scope to achieve its designed range of angulating movement. The ribs are often covered with either a stainless steel or fiber mesh material. The outer layer is a thin walled flexible rubber tube. The rubber tube provides no structural support but does provide a fluid and chemical resistant covering. The rubber tube is called the "bending rubber" or "bending sheath" and is most often an extruded Viton™ material.
The bending section is hollow and protects multiple internal components. At the end of the bending section is the distal cap or distal tip. This is the termination point for the internal components including the glass lens systems for light and image. This section of the scope is especially prone to impact and laser damage.
Many scopes have a white distal tip protector to allow for reflection opposed to absorption of laser beams.
Next Page: Small Diameter Flexible Endoscope Anatomy: The Inside
