Illustration of skin tissue: epidermis, dermis, hair, hair follicle, erector pili muscle, sebaceous gland, sweat gland, nerve fibers, blood vessels and subcutaneous tissue. The epidermis is raised to show the dermal papillae.

Illustration of the abdominal anatomy: stomach, liver, spleen, gallbladder, pancreas, kidneys, and small intestine. Also shown are the major blood vessels: aorta, vena cava, and portal vein.

Illustration of the epidermis, cutaway view, showing a normal melanocyte (large pink cell) containing melanosomes (brown granules). Melanosomes are organelles within the melanocyte that produce melanin, the light-absorbing pigment in skin, and melanin granules migrate to adjacent keratinocytes. Melanoma tumors arise from mutant melanocytes.

Medical illustration of glomerular filtration. Red blood cells are shown in a glomerular capillary, with the filtrate that is processed into urine by the kidney passing through the filtration membrane into the glomerular capsule.

Medical illustration of the anatomy of the normal hip, showing the sciatic nerve passing through the sciatic notch and under the piriformis muscle. Compression of the nerve at this site may cause sciatica.

Illustration of an oligodendrocyte repairing the myelin sheath of a central nervous system neuron damaged by multiple sclerosis (MS). MS forms lesions (demyelination) in the sheath, causing impulses along the nerve to be impaired or lost. Oligodendrocytes help repair damaged nerves, but MS can destroy oligodendrocytes via apoptosis (programmed cell death).

Illustration of an oligodendrocyte repairing the myelin sheath of a central nervous system neuron damaged by multiple sclerosis (MS). MS forms lesions (demyelination) in the sheath, causing impulses along the nerve to be impaired or lost. Oligodendrocytes help repair damaged nerves, but MS can destroy oligodendrocytes via apoptosis (programmed cell death).

Illustration of an oligodendrocyte repairing the myelin sheath of a central nervous system neuron damaged by multiple sclerosis (MS). MS forms lesions (demyelination) in the sheath, causing impulses along the nerve to be impaired or lost. Oligodendrocytes help repair damaged nerves, but MS can destroy oligodendrocytes via apoptosis (programmed cell death).

Still life photomontage of a sepia-toned heart (model), anterior view, on a blue textured background with Da Vinci heart sketches and EKG graphics.

Knee joint osteoarthritis, showing disease progression from superficial to deep. Articular cartilage shows wear, abrasion, and the near-obliteration of the menisci. Cracks in the articular surfaces cause the formation of subchondral (under the bone surface) cysts and joint calcification. Bones lose vascularization and harden with osteophytes (bone lipping).

Illustration of the surgical elevation of the urethra by a sling that passes beneath it and attaches to the inside of the abdominal body wall. This procedure is used to treat urinary stress incontinence due to loss of the normal angle of the urinary bladder to the urethra (bladder neck). The sling is made from the patient's own connective tissue (fascia).

Illustration of pancreatitis, showing the characteristic blood-filled blisters, or pseudocysts, seen in advanced cases.

Illustration of the brain with a cerebral stroke in the region fed by the middle cerebral artery.

Illustration of a woman showing the main muscles of the back, including the trapezius, deltoid, and latissimus dorsi.

Illustration showing the main muscles of the back, including the trapezius, deltoid, rhomboids (rhomboideus major and minor), and infraspinatus.

Illustration of the heart showing its major veins and arteries, including the aorta, pulmonary artery, and vena cava.

Illustration of the uterus within the pelvis, showing the ovaries, fallopian tubes, vagina, sacrum, and hip.

Illustration of the lung's air sacs, with a cutaway view of one alveolus. The blood capillaries are also shown. The lung's smallest bronchioles terminate in respiratory ducts that lead into the clusters of alveoli called air sacs (also known as alveolar sacs), shown here.

3D illustration of the kidneys from a lateral oblique view. Also shown are the inferior vena cava, abdominal aorta, adrenal glands, and ureters.

3D illustration of a transparent kidney. The renal artery, ureter, calyxes, and medullary pyramids (renal pyramids) are also shown.