Cross-section of a coronary artery showing plaque build-up, narrowing and clot, resulting in a myocardial infarction (heart attack).

Cross-section of a coronary artery showing plaque build-up, narrowing and clot, resulting in a myocardial infarction (heart attack).

Cross-section of a coronary artery showing plaque build-up, narrowing and clot, resulting in a myocardial infarction (heart attack).

Artist's depiction of a targeted radiation beam destroying a malignant tumor.

A stylized depiction of the destruction/alteration of the genetic code by a malignant tumor.

A stylized depiction of the destruction/alteration of the genetic code by a malignant tumor; also shown are some of the organs that are most affected by genetic disposition to cancer.

This illustration depicts a male figure and molecular DNA. The cascade of foreground molecules at the top represents the molecular structure of the four nucleotides present in the organic base pairs of DNA: thymine, cytosine, guanine and adenine. Molecules at the bottom represent the phosphate and deoxyribose groups of nucleotides which form the chain that bonds all the nucleotides together in the DNA double-helix.

This illustration depicts molecular DNA. The cascade of foreground molecules at the top represents the molecular structure of the four nucleotides present in the organic base pairs of DNA: thymine, cytosine, guanine and adenine. Molecules at the bottom represent the phosphate and deoxyribose groups of nucleotides which form the chain that bonds all the nucleotides together in the DNA double-helix. The background represents a human cell.

This illustration depicts molecular DNA. The cascade of foreground molecules at the top represents the molecular structure of the four nucleotides present in the organic base pairs of DNA: thymine, cytosine, guanine and adenine. Molecules at the bottom represent the phosphate and deoxyribose groups of nucleotides which form the chain that bonds all the nucleotides together in the DNA double-helix. The background represents a human cell.

An ' stylized depiction of a retrovirus, consisting of a geomic nucleic acid, RNA or DNA (here RNA, in violet), and surrounded by capsid proteins (orange-yellow), surrounded by a glycoprotein envelope. Examples of retroviruses are the flu virus, the AIDS virus, and the SARS virus (depicted here). Viruses can only reproduce by invading and taking over other cells, as they lack the cellular machinery for self-reproduction.

An illustration of the key component of the nervous system, the neuron. Neurons have a large number of extensions called dendrites; branches of the neuron cell body that can be long, or very short to act as chemical message receivers from other neurons. The main extension here is the axon, the purpose of which is to transmit electro-chemical signals from one neuron to another neuron. Long axons are covered by a myelin sheath, a fatty substance that covers the axon and insulates it. Shown here is the connection between one neuron (center) and a foreground neuron body. At the end of the axon ending, the bouton, a synapse with the dendrite of the foreground cell is taking place. Across this synapse, very small neurotransmitters (red) cross this gap into the next neuron, creating the nervous system message transferral system.

An illustration of the key component of the nervous system, the neuron; human brain in the background. Neurons have a large number of extensions called dendrites; branches of the neuron cell body that can be long, or very short to act as chemical message receivers from other neurons. The main extension here is the axon, the purpose of which is to transmit electro-chemical signals from one neuron to another neuron. Long axons are covered by a myelin sheath, a fatty substance that covers the axon and insulates it. Shown here is the connection between one neuron (center) and a foreground neuron body. At the end of the axon ending, the bouton, a synapse with the dendrite of the foreground cell is taking place. Across this synapse, very small neurotransmitters (red) cross this gap into the next neuron, creating the nervous system message transferral system.

Illustration depicting the human heart.

Illustration depicting a technique for treatment of vertebral compression fracture called balloon kyphoplasty. This minimally invasive treatment can relieve pain and improve quality of life in patients with these fractures.

This is an illustration of a vertebral compression fracture.

Illustration depicting the human heart.

An illustration of the key component of the nervous system, the neuron; human brain in the background. Neurons have a large number of extensions called dendrites; branches of the neuron cell body that can be long, or very short to act as chemical message receivers from other neurons. The main extension here is the axon, the purpose of which is to transmit electro-chemical signals from one neuron to another neuron. Long axons are covered by a myelin sheath, a fatty substance that covers the axon and insulates it. Shown here is the connection between one neuron (center) and a foreground neuron body. At the end of the axon ending, the bouton, a synapse with the dendrite of the foreground cell is taking place. Across this synapse, very small neurotransmitters (red) cross this gap into the next neuron, creating the nervous system message transferral system.

An illustration of the key component of the nervous system, the neuron; human brain in the background. Neurons have a large number of extensions called dendrites; branches of the neuron cell body that can be long, or very short to act as chemical message receivers from other neurons. The main extension here is the axon, the purpose of which is to transmit electro-chemical signals from one neuron to another neuron. Long axons are covered by a myelin sheath, a fatty substance that covers the axon and insulates it. Shown here is the connection between one neuron (center) and a foreground neuron body. At the end of the axon ending, the bouton, a synapse with the dendrite of the foreground cell is taking place. Across this synapse, very small neurotransmitters (red) cross this gap into the next neuron, creating the nervous system message transferral system.

Illustration showing pregnant patient with epidural in place for labor pain relief. Evidence of fever on patien'ts face.

Conceptual image of junk food passing through the arteries into the heart.