Helicobacter pylori and the erosion of the mucous lining on the cellular surface of the gastric mucosa, at the edge of an ulcer (foreground). Often found in the human stomach, in some people H. pylori causes mucous stomach lining erosion and contributes to peptic ulcers. A sectioned stomach with a large peptic ulcer is shown in the background.

Illustration of the most common sites of endometriosis, midline section of the female pelvic anatomy. Sites shown include (clockwise, starting from the rectum): rectum, or sigmoid colon; outside of the sigmoid colon; ovary; fallopian tube; posterior surface of the uterus; and pelvic peritoneum.

Illustration of a normal heart, anterior view. The top two ECG traces show normal rhythms. The next two traces below, which pass through the center of the heart, show an arrhythmia. The bottom trace shows atrial fibrillation. A representation of the electrical conduction system inside the heart is shown in orange.

Illustration of a typical hair follicle on the edge of a section of skin. The follicle is clogged and becoming infected and inflamed. Also shown in section is the subcutaneous oil gland (sebaceous gland).

Illustration of an eyeball in section, viewed from the outside of the eye, showing in the focal area the characteristic presentation of how diabetes affects the retina.

Asthmatic terminal bronchi. Blood oxygen exchange takes place in the alveoli, the balloon-like sacs on the ends of the bronchi. The tiny muscles that encircle these bronchi constrict in asthma patients and restrict the volume of inhaled oxygen. The air passageway is also constricted by mucous collecting in the bronchial lining, shown in the cut section.

Illustration of the aorta, left side section view, showing a balloon catheter inflated inside for intra-aortic balloon pumping (IABP). IABP therapy helps the heart decrease its workload and increase coronary blood flow by inflating during diastole (rest phase) and deflating during systole (work phase).

Illustration of a toenail with a fungal infection (onychomycosis). Three common fungi that cause this condition are shown: Trichophyton mentagrophytes, top; Candida albicans, bottom; Microsporum audouinii, left.

Conceptual illustration of genetic testing for breast and ovarian cancer: DNA (foreground); breast tissue on a female figure with an orange glow representing breast cancer (background); and a normal ovary (lower right corner).

Conceptual illustration of genetic testing for colon cancer: DNA (foreground); the colon with the front of the descending colon and sigmoid colon removed (background).

Illustration of scleroderma. Shown are a pursed mouth, characteristic of scleroderma (background); two types of collagen (bottom), type I (striped) and type III (web), both affected by scleroderma; and cellular changes involved in the disease process (above). The pursed mouth occurs when collagen breaks down and the skin starts to lose its elasticity.

Illustration of the typical vein pattern in the arm, showing their position relative to important nerves to avoid when performing venapuncture.

Rheumatoid arthritis (RA) pathology. Pannus (shown as orange lesions), is an inflammatory granulation tissue resulting from the progressive thickening and inflammation of the synovium, the membranous lining of the joint capsule (shown with front removed in this flexed knee view). Pannus is associated with the breakdown of the articular surfaces.

Illustration of normal female pelvic anatomy, three-quarter view seen from below, with an orange and yellow glow implying inflammation. Pelvic inflammatory disease is often abbreviated as PID.

Uterus, sagittal section, showing three primary types of fibroids, classified by their location in the uterine wall. Subserosal fibroids develop in the outer wall and continue to grow outward; intramural fibroids, the most common type, develop within the wall and expand; and submucosal fibroids, the least common, develop just under the uterine cavity lining.

Hiatal hernia and gastroesophageal reflux disease (GERD). A hiatal hernia occurs when a diaphragm weakening allows a portion of the stomach to herniate upward into the chest. Some people with a hiatal hernia suffer from GERD, a condition in which gastric juices splash back into the esophagus, causing extreme heartburn pain.

Illustration of the normal anatomy of the female digestive system.

Illustration of the normal anatomy of a pregnant female showing the upward displacement of the digestive system by the developing fetus.

Illustration of the normal anatomy of the digestive system from the distal esophagus to the anus.

Conceptual illustration of diabetes drugs used to treat problems in the liver, pancreas, and digestive system. A normal pancreas is shown above a drawing of the digestive system. A pill bottle releases representative drugs to treat diabetes-related problems in the liver and digestive system as well as insulin production in the pancreas.