Dictionary

Body systems

Anatomy and the conditions of each body system, from the heart and lungs to the skin.

ideationThe forming of thoughts or ideas, especially repeated thoughts about a particular act.

idiopathicHaving no known cause.

IgAImmunoglobulin A: a kind of antibody found mostly in the body's linings and in saliva, tears and breast milk.

IgDImmunoglobulin D: an antibody found mostly on the surface of B cells, where it helps start an immune response.

IgEImmunoglobulin E: the type of antibody involved in allergic reactions and in fighting parasites.

ileumThe last and longest part of the small intestine, which joins the large intestine.

ileusA slowing or stopping of the normal movement of the intestines, with nothing physically blocking them.

iliacHaving to do with the ilium, the large, wing-shaped upper part of the hip bone.

iliumThe large, wing-shaped upper part of each hip bone.

imbalanceA lack of balance: too much or too little of something the body needs to keep at a steady level.

immobilityBeing unable to move about freely, such as being kept in bed or a chair.

immuneProtected against a disease, or having to do with the body's defense system against germs and other foreign things.

immune responseThe way the body recognizes and defends itself against germs and other substances it sees as foreign.

immune systemThe body's defense system of cells, tissues and organs that fights germs and other foreign substances.

immunityThe body's ability to resist or fight off a particular infection or disease.

immunocompromisedHaving an immune system that is weaker than normal at fighting infection.

immunodeficiencyA state in which the immune system is weaker than normal and cannot fight infection well.

immunoglobulinAn antibody: a protein made by B cells that recognizes and helps destroy a specific germ or foreign substance.

immunologyThe branch of science and medicine that studies the immune system.

immunotherapyTreatment that uses or changes the body's immune system to fight disease.

impactedFirmly packed or wedged in place so it cannot move or pass normally.

impetigoA contagious bacterial skin infection, most common in young children.

implantationThe attachment of a fertilized egg to the lining of the uterus, the start of a pregnancy.

impulseAn electrical signal that travels along a nerve or through the heart muscle; also, a sudden urge to act.

in vitro fertilizationA fertility treatment in which eggs are joined with sperm in a lab and an embryo is then placed in the uterus.

inactivateTo make something, such as an enzyme, drug, hormone or germ, stop working.

incontinenceLoss of control over the bladder or bowel, so urine or stool leaks out without the person meaning it to.

increased intracranial pressurePressure inside the skull that has risen above the normal range.

indurationAn area of tissue that has become firm or hard, felt by touch.

infancyThe first year of life, from birth to about 12 months of age.

infantA baby from birth to 1 year of age.

infarctionDeath of an area of tissue (an infarct) because its blood supply has been cut off.

inferiorLower, or below; nearer the feet.

inferior vena cavaThe large vein that carries blood from the lower body back to the right atrium of the heart.

infertilityNot being able to become pregnant after a year of regular sex without birth control, or after six months for women over 35.

inflammationThe body's protective response to injury or infection, with redness, heat, swelling, pain and sometimes loss of function.

inflammatory bowel diseaseA group of long-term diseases, mainly Crohn disease and ulcerative colitis, in which the lining of the digestive tract becomes inflamed.

inflammatory responseThe body's protective reaction to injury or infection, which brings blood, fluid and white cells to the area.

influenzaAn infection of the nose, throat and lungs caused by influenza viruses; the flu.

ingestionTaking something into the body through the mouth, such as food, drink, a drug or a poison.

inguinalRelating to the groin, the fold where the thigh meets the lower abdomen.

inhalationBreathing in; also, a way of giving a drug as a mist or powder that is breathed into the lungs.

inner earThe deepest part of the ear, inside the skull bone, which holds the organs of hearing and balance.

inotropicChanging the force with which the heart muscle contracts; an inotropic drug is one that does this.

insomniaTrouble falling asleep, staying asleep or getting restful sleep.

insufficiencyA state in which an organ or part does not work well enough to meet the body's needs.

insulinA hormone made by the pancreas that lets the body's cells take in glucose, also made as a medicine.

insulin resistanceA state in which the body's cells respond poorly to insulin, so more insulin is needed to move glucose into them.

intakeWhat a person takes into the body, especially fluids or food, counted over a set time.

integumentaryRelating to the skin and the parts that grow from it, such as hair, nails and skin glands.