Illustration of a normal pancreatic islet of Langerhans. Cells from the glandular tissue of the pancreas are shown, with an islet (center) made up of the smaller endocrine cells that are responsible for insulin production.

Illustration of the pancreas and an islet of Langerhans. The front view of the pancreas is shown with an inset detail of cells from the glandular tissue of the pancreas, with an islet (center) made up of the smaller endocrine cells that are responsible for insulin production.

Illustration of the pancreas and an islet of Langerhans. The front view of the pancreas is shown with an inset detail of cells from the glandular tissue of the pancreas, with an islet (center) made up of the smaller endocrine cells that are responsible for insulin production.

Illustration of penis innervation, showing the autonomic nerves of the penis related to erectile function.

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 normal human prostate gland anatomy, sagittal section. Shown are the prostate gland with the seminal vesicle, vas deferens, and a portion of the membranous urethra.

Illustration of the anatomy of the human prostate gland. Shown is a sagittal section anatomical view of the prostate glad with seminal vessicles, vas deferens, and a portion of the membranous urethra.

Illustration of the normal human anatomy of the male reproductive system, oblique view. Shown are the penis, testicles, epididymis, urethra, bulbourethral glands, prostate gland, vas deferens, seminal vesicle (one of a pair is visible), and scrotum. The urinary bladder above the prostate is shown for reference.

Illustration of a normal esophagus and stomach in a child, shown in their normal anatomical position.

Illustration of a normal esophagus and stomach in a child, shown in their normal anatomical position.

Illustration of the normal human anatomy of a testicle. Shown are the testicle with septa, epididymis with ductules, and ductus deferens.

Illustration of the normal human anatomy of a testicle. Shown are the testicle with septa, epididymis with ductules, and ductus deferens.

Illustration of the male urinary bladder, showing a cutaway view of the urinary bladder, a portion of the urethra with the right ureter, the position of the prostate gland (shown transparently), and the urethral sphincters.

Illustration of intense headache pain and possible sources: vascular, temporomandibular joint (TMJ) syndrome, and the brain itself. CT scans in the background convey clinical diagnosis, often involved in treatment of patients suffering from migraine-type symptoms.

Illustration of sports-related eye injuries and their clinical diagnosis. Shown are: a normal eyeball, parasagittal section (foreground); a baseball heading toward the eye; an examiner using a litmus-type paper and fingers to sample fluid content, aligned with a CT scan of an orbit fracture; and a retinal photograph of an injured retina (orange background).

Osteoporosis: the three most common femoral fracture sites. Background shows more general diagnostic references to the disease: overall clinical assessment for osteoporosis yields a "T-score" rating; posterior spinal view superimposed over an actual bone density scan used for assessment.

Illustration of a thyroid gland, swollen and inflamed. The view shows the position in the brain of the pituitary gland, which secretes thyroid stimulating hormone (TSH). TSH levels are monitored in patients with thyroid disease.

Osteoarthritis treated by injection into the knee joint of hyaluronate, a component of synovial fluid that provides lubrication and shock absorption. By restoring the fluid's viscoelastic properties, the injection reduces pain due to wear and abrasion of the articular cartilage surfaces. The synovial membrane (blue) encases the joint, here shown flexed.

Limbic system of a normal brain, midline section, highlighting the hippocampus, the brain's center for memory processing. The anatomy and neurophysiology of the hippocampus and its related structures (blue, purple, and gold), including the fornix, dentate gyrus, and mammillary bodies, are the focus of research on memory disorders such as Alzheimer's disease.

Generic cochlear implant artificial hearing device in a child. An external device picks up sounds and transmits processed digital auditory signals to a subcutaneously implanted receiver. This in turn relays the signals by wire via the middle ear to the implant in the cochlear coil of the inner ear, where electrode-stimulated nerves send signals to the brain.