Illustration of the two steps of an endoscopy to remove a gallstone. In the first step, a catheter is introduced into the cystic duct. In the second step (enlarged inset), a gallstone ensnared by a wire cage is pulled out through the duct.

Illustration of gingivitis, showing an inflamed gingiva (gum) on the right side of the tooth. For comparative purposes, a normal gingiva is shown on the left side of the tooth.

Illustration of a health care provider using a stethoscope to listen to the heart sounds (auscultation) of a child. The child's heart is shown highlighted within the rib cage.

Illustration of the human heart with atherosclerosis, anterior view. Shown are the ventricles and atria of the heart as well as its major arteries and veins. An enlargement shows a cutaway view of a coronary artery with atherosclerotic plaque buildup (yellow).

Illustration of the human heart with atherosclerosis, anterior view. The illustration shows the ventricles and atria of the heart as well as its major arteries and veins. An enlargement shows a cutaway view of a coronary artery with atherosclerotic plaque buildup (yellow).

Illustration of the human heart with atherosclerosis, anterior view. The illustration shows the ventricles and atria of the heart as well as its major arteries and veins. An enlargement shows a cutaway view of a coronary artery with atherosclerotic plaque buildup (yellow).

Illustration of a human heart and cardiac arrhythmia. An electrocardiogram (ECG) strip is shown with arrhythmic waveform tracings. An outline of a human body and repeats of the arrhythmic tracings are shown in the background.

Illustration of the auscultation zones (in color) for the diagnosis of heart murmurs in a child. The child's heart is highlighted within the rib cage against a background showing the child's head and torso and the examiner's hand and stethoscope.

Illustration of the diagnosis and treatment of hypertension. In the background, a female health care provider is shown confirming hypertension in an elderly female patient. In the foreground are prescription medication tablets shown as a treatment, an artery, and the dial of the sphygmomanometer used to measure blood pressure.

Illustration of lead poisoning in a child, schematically depicting lead (Pb) molecules entering red blood cells in the bone marrow of child. The child's esophagus and stomach are shown in the figure of the child; the primary source of lead contamination in children is by ingestion.

Illustration of marijuana prescribed for therapeutic use, depicted in a whimiscal manner. The foreground shows a prescription vial containing marijuana cigarettes and pills of THC (tetrahydrocannabinol, the psychoactive and physiologically active molecule derived from cannabis resin). The background shows a pattern of cannabis leaves.

Illustration of osteoarthritis of the human knee. Shown is extensive osteoarthritis of the knee joint, including degraded articular cartilage (center, pink and cream) and numerous osteophytes (abnormal bony growths) formed at the periphery of the joint (small bumps at the ends of the bones shown, center).

Illustration of a health care provider conducting a Doppler scan of arteries in the foot to diagnose peripheral artery disease (PAD). The scan is performed while a blood pressure cuff is inflated on the ankle; the pressure gauge shows low blood pressure in the lower limb. The patient's foot is pale and shows vascular lesions.

Illustration of normal human male sexual circuitry, showing the neural connections from the cerebral cortex, hypothalamus, and brain stem, through the spinal cord generators, to the autonomic nerves of the penis. The autonomic innervation of the penis is responsible for erectile function.

Illustration of a pharyngitis strep throat test. Pharyngitis caused by Streptococcus sp. bacteria is being diagnosed with a rapid test kit using a throat swab culture from a child patient. The rapid readout is able to diagnose strep throat. Streptococcus bacteria are shown in the background.

Illustration of pharyngitis: a throat swab being taken for a culture test to make a diagnosis of strep throat. Streptococcus bacteria are shown in the background.

Illustration of an enlarged prostate, showing a benign, moderately enlarged prostate (pink). This anterior view to the right shows its 3D position within a sagittal section of the male pelvis. The bladder is above, penis tissues are below, and the rectum is behind and to the left of the prostate.

Illustration of an enlarged prostate, showing a benign, moderately enlarged prostate (pink). This anterior view to the right shows its 3D position within a sagittal section of the male pelvis. The bladder is above, penis tissues are below, and the rectum is behind and to the left of the prostate.

Illustration of prostatitis, an infected and moderately enlarged prostate (red). This anterior view to the right shows its 3D position within a sagittal section of the male pelvis. The bladder is above, penis tissues are below, and the rectum is behind and to the left of the prostate.

Illustration of prostatitis, an infected and moderately enlarged prostate (red). This anterior view to the right shows its 3D position within a sagittal section of the male pelvis. The bladder is above, penis tissues are below, and the rectum is behind and to the left of the prostate.