Illustration of teenage girl at normal weight. Compare 047806P000033-01 (normal) and 047806P000034-01 (overweight).

Illustration of overweight teenage girl. Compare 047806P000033-01 (normal) and 047806P000034-01 (overweight).

Illustration of teenage girl at normal weight. Compare 047806P000035-01 (normal) and 047806P000036-01 (overweight).

Illustration of overweight teenage girl. Compare 047806P000035-01 (normal) and 047806P000036-01 (overweight).

Illustration of teenage girl at normal weight. Compare 047806P000037-01 (normal) and 047806P000038-01 (overweight).

Illustration of overweight teenage girl. Compare 047806P000037-01 (normal) and 047806P000038-01 (overweight).

Illustration of overweight man. Compare 047806P000039-01 (overweight), 047806P000040-01 (normal), and 047806P000041-01 (both, side by side). Also note, the male figures in 047806P000039-01 and 047806P000040-01 are adult versions of the teenagers in 047806P000028-01 and 047806P000027-01, respectively.

Illustration of a man at normal weight. Compare 047806P000039-01 (overweight), 047806P000040-01 (normal), and 047806P000041-01 (both, side by side). Also note, the male figures in 047806P000039-01 and 047806P000040-01 are adult versions of the teenagers in 047806P000028-01 and 047806P000027-01, respectively.

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).

Normal blood sugar regulation. High blood sugar (glucose) causes pancreatic beta cells to secrete insulin into the bloodstream. When insulin attaches to cell membrane receptors, the cells absorb glucose, lowering blood sugar. Low blood sugar causes pancreatic alpha cells to secrete glucagon, which induces the liver to release glucose, raising blood sugar.

Normal blood sugar regulation. High blood sugar (glucose) causes pancreatic beta cells to secrete insulin into the bloodstream. When insulin attaches to cell membrane receptors, the cells absorb glucose, lowering blood sugar. Low blood sugar causes pancreatic alpha cells to secrete glucagon, which induces the liver to release glucose, raising blood sugar.

Normal blood sugar (glucose) regulation. Carbohydrates are broken down into glucose, which is absorbed into the blood. Pancreatic beta cells secrete insulin, which attaches to cell membrane receptors, stimulating cells to absorb blood glucose. Pancreatic alpha cells secrete glucagon, which induces the liver to release glucose, increasing blood glucose.

Normal blood sugar (glucose) regulation. Carbohydrates are broken down into glucose, which is absorbed into the blood. Pancreatic beta cells secrete insulin, which attaches to cell membrane receptors, stimulating cells to absorb blood glucose. Pancreatic alpha cells secrete glucagon, which induces the liver to release glucose, increasing blood glucose.

Normal blood sugar (glucose) regulation. Carbohydrates are broken down into glucose, which is absorbed into the blood. Pancreatic beta cells secrete insulin, which attaches to cell membrane receptors, stimulating cells to absorb blood glucose. Pancreatic alpha cells secrete glucagon, which induces the liver to release glucose, increasing blood glucose.

Illustration of a hand holding a non-sterile needle. Sharing intravenous needles is a common way to spread hepatitis, HIV, and other infectious diseases.

Illustration of a hand holding a non-sterile needle. Sharing intravenous needles is a common way to spread hepatitis, HIV, and other infectious diseases.

Molecular model of galantamine, an Alzheimer's disease medication, with carbon (light blue), hydrogen (white), oxygen (yellow), and nitrogen (purple) atoms.

Molecular model of galantamine, an Alzheimer's disease medication, with carbon (green), hydrogen (white), oxygen (red) atoms, and nitrogen (blue) atoms.

Molecular model of cyclosporine, an immunosuppressive drug often used to prevent the rejection of organ transplants. Atoms shown are carbon (white), oxygen (red), and nitrogen (violet). Hydrogen atoms are not shown.

Simulated bull's-eye rash (erythema migrans) on the back. Erythema migrans, a symptom of Lyme disease, radiates from the location of an infected tick bite.