Stethoscopes are medical instruments used to listen to the sounds from the chest cavity, especially the heart and the lungs. Sphygmomanometers are another very common medical device, which use a pressure cuff to measure the patient's blood pressure. They have both been part of doctors' toolkits for many years, and are quite simple devices that nonetheless, deliver important results. A trained doctor can hear if the lungs are functioning properly, identify problems with the heart and avoid future problems by monitoring the patient's blood pressure. As simple devices, it is quite simple to identify their parts.
Identifying Parts of a Stethoscope
Lay the stethoscope out on the table. It will have a disk, connected by a flexible rubber tube to two rigid metal tubes.
Look at the ends of the metal tubes for small rubber pieces. These are the ear tips or earpieces that allow the user to hear the sounds coming through the stethoscope tube. One tip is placed in each ear of the person using the stethoscope, ideally in a forward position in the ear canal.
Follow the rigid tubes down from the ear pieces. These metal pieces are called the binaural tubes (binaural meaning "two ears") and can often be rotated to give the earpieces the best fit in the ears of the user.
Look at the end of the binaural tubes opposite from the earpieces. They are connected to flexible black tubing that merges into a single tube that connects to and carries sounds from the stethoscope disk. This tubing is made from PVC, neoprene, or other synthetic materials. There are two types of tube: single tubes that split into two when they go to the earpiece, and double tubes that are separated all the way down to the disk.
Follow the flexible tubing away from the earpieces. It joins to a circular piece called the "chestpiece" or "head" of the stethoscope. This head contains a metal diaphragm the vibrates with sounds from the chest, amplifying them to be transmitted up the tube. There are two types of chestpiece: single-sided and double-sided. Double-sided models have a flatter side for catching high-frequency sound and a bell-shaped side for low frequencies.
Look closely at the metal chestpiece. It is normally wrapped in a rubber ring. This is called a "chill ring" and forms a barrier between the often-cold metal disk of the stethoscope and the skin of the patient. (reference 1)
Identifying the Parts of a Sphygmomanometer
Look for a large, plastic piece containing a clear plastic or glass tube. This is the mercury column. It contains mercury that rises in the tube in response to pressure placed by the blood on a blood pressure cuff. This piece is identifiable by the numbered lines alongside it that are used for gauging the exact blood pressure; it will have two leather disks at each end to keep the mercury in while letting air escape.
Follow the mercury column down to the bottom. Below the "0" mark is a small container. This is the mercury reservoir, where mercury sits when the sphygmomanometer is not in use.
Look for a rubber tube connected to the mercury reservoir, and follow it to a large fabric cuff. This is the blood pressure cuff. It is wrapped around the patient's arm and inflated until rigid. Once inflated, the pressure of the patient's blood flow will push air out of the cuff, moving the mercury up in the measuring column and giving blood pressure.
Find the point on the cuff where another rubber tube connects to a black rubber bulb. At the joint between the bulb and tube there will be a valve with a rotating cap. This valve allows air in to inflate the cuff when the bulb is squeezed, then can be unscrewed to release the air and remove the cuff.