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Glossary

Showing 871-880 out of 1196 Terms

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  • Opioid

    (OH-pee-OYD)

    A substance used to treat moderate to severe pain. Opioids are like opiates, such as morphine and codeine, but are not made from opium. Opioids bind to opioid receptors in the central nervous system. Opioids used to be called narcotics. An opioid is a type of alkaloid.

  • Optic nerve

    (OP-tik nerv)

    The nerve that carries messages from the retina to the brain.

  • Optical

    Pertaining to the sense of sight or to the eyes.

  • Organ

    (OR-gun)

    A part of the body that performs a specific function. For example, the heart is an organ. organelle.

  • Organism

    (OR-guh-NIH-zum)

    A living thing, such as an animal, a plant, a bacterium, or a fungus.

  • Orgasm

    (OR-ga-zum)

    The final part of the sex act, which involves contraction of sexual organs and a sudden release of endorphins, leading to a feeling of pleasure. In males, orgasm usually occurs with release of semen.

  • Orthopedic surgeon

    (OR-thuh-PEE-dik SER-jun)

    A surgeon who has special training in diagnosing and treating injuries and diseases of the musculoskeletal system. This includes the bones, joints, tendons, ligaments, and muscles.

  • Osteomyelitis

    Inflammation of the bone caused by an infection, which may spread to the bone marrow and tissues near the bone. Osteomyelitis can cause severe pain in the infected bone. If it is not treated, it can kill bone tissue.

  • Osteoporosis

    (OS-tee-oh-puh-ROH-sis)

    A condition in which there is a decrease in the amount and thickness of bone tissue. This causes the bones to become weak and break more easily. Osteoporosis may be caused by older age, hormone changes, taking certain medicines, and not eating enough foods with calcium and vitamin D. It may also be caused by certain types of cancer and cancer treatment.

  • Osteosarcoma

    OS-tee-oh-sar-KOH-muh

    A cancer of the bone that usually affects the large bones of the arm or leg. It occurs most commonly in young people and affects more males than females. Also called osteogenic sarcoma.