Illustration of a human eye, showing a quarter dissection (left) and a detail of the retinal membrane (right). Shown are the cornea, iris, lens, retina, blood vessels (supplying zinc and other nutrients), macula, optic nerve, and eye muscle (quarter dissection view); and the nerve ending, rod, and cone (detail view).

Illustration of a penis with a resectoscope instrument inserted, cutaway cross section. Shown are the corpus cavernosum, prostate gland, testis, scrotum, anus, rectum, ureteral orifice, urinary bladder, and pubic bone.

Grayscale illustration of root canal therapy. To save a tooth, diseased pulp is removed and any abscess is drained (top right). Once the infection is gone, root canals are lined with cement, filled, and sealed (middle right). Tooth restoration is often completed with a crown supported by a post (bottom right). A normal tooth is also shown (left).

Grayscale illustration of a heart assist system, which provides a patient in heart failure with full circulatory assistance, allowing the heart to rest. The system is often used to assist patients in heart failure while they are waiting for a heart transplant.

Grayscale illustration of three cross section views of the human eye, showing normal anatomy (left), glaucoma (top right), and cataracts (bottom right). Glaucoma is caused by a buildup of fluid that increases pressure in the eyeball, damaging the optic nerve. A cataract is caused by changes in proteins that cause the lens to become opaque.

Illustration of the normal anatomy of a human eye, cross section. Shown are the cornea, iris, lens, retina, blood vessels (supplying zinc and other nutrients), macula, optic nerve, and eye muscle.

Illustration of a normal brain superimposed on a line drawing of a male head, side view. Shown are the skull, cerebrum, cerebellum, and brain stem.

Grayscale illustration of healing burns on the back of a human hand and wrist, showing the layers of the dressing.

Grayscale illustration portraying where herpes type one virus can remain dormant within the brain. Arrows to the eye and mouth indicate some regions where the virus can become active.

Grayscale illustration of laser treatment being used for tongue cancer (carcinoma of the tongue).

Illustration of a normal human female reproductive system (front and cutaway views), showing the vagina, cervix, uterus, fallopian tubes, fimbria, and ovaries.

Illustration of a human postmenopausal uterus (front and cutaway views). Shown are the vagina, cervix, uterus, fallopian tubes, fimbria, and ovaries.

Illustration of a normal human female breast, cutaway cross section. Shown are the ribs, fat, ligament, milk (mammary) glands, nipple, and milk ducts.

Illustration of a postmenopausal human female breast, cutaway cross section. Shown are the ribs, fat, ligament, milk (mammary) glands, nipple, and milk ducts.

Illustration of a normal human female pelvis, cutaway cross section. Shown are the rectum, cervix, spine, fallopian tubes, uterus, bladder, pubic bone, urethra, and vagina.

Illustration of a postmenopausal human female pelvis, cutaway cross section. Shown are the rectum, cervix, spine, fallopian tubes, uterus, bladder, pubic bone, urethra, and vagina.

Illustration showing how lotion is absorbed into dry skin, beginning with the application of lotion at the left and proceeding to full absorption of the lotion at the right.

Illustration of Teflon arterial vessel grafts (gray) in a human lung.

Illustration of diabetic arterial disease, showing gangrene and ulcerations of the toes. Although it is unusual in other atherosclerotic peripheral vascular diseases, this condition is a serious threat in diabetes. A hand is shown taking the dorsal pedis pulse.

Illustration of diabetic arterial disease and foot drop. Foot drop is associated with vascular disorders (especially in diabetics), and symptoms may result from ankle joint deterioration, foot drop, or sensory impairment. The patient often walks gingerly with a cane. because of a loss of position sense.