Play 0:00 A-DE-IJ-OP-Z A-D Return to top Acetaminophen Analgesic used to treat minor aches and pains. Adenoid Gland located in the roof of the mouth, behind the soft palate where the nose connects to the throat. Adenoidectomy Surgical removal of the adenoids. Adenovirus Common viruses that cause a range of illnesses. They can cause cold-like symptoms such as sore throat, bronchitis, diarrhea, or pinkeye. Alimentary tract (digestive tract) Organ system which takes in food, digests it to extract and absorb energy and nutrients, and excretes the waste. Allergen Substance that causes an allergic reaction. Allergic pinkeye Eye inflammation caused by allergies. Alveolar sac Clusters of alveoli located in the lungs at the end of the bronchioles. Alveoli Located in the lungs, alveoli are air sacs bunched together in clusters at the end of the bronchioles. Amoxicillin Antibiotic often used to treat bacterial infections. Anaphylaxis Acute allergic reaction to an antigen to which the body has become hypersensitive. Antibiotics Medications widely used to treat bacterial infections. Antibodies Y-shaped proteins produced by the immune system to stop intruders from harming the body. Antigenic drift Gradual genetic change in a virus. Antigenic shift Abrupt, major genetic change in a virus. Antihistamine Medicine used to treat common allergy symptoms such as sneezing, watery eyes, hives, and a runny nose. Antiviral medication Medication used specifically for treating viral infections rather that bacterial infections. Anus Opening at the end of the alimentary canal through which solid waste leaves the body. Aqueous layer Located in the eye, the aqueous layer is the middle layer of the tear film which nourishes the cornea and conjunctiva. Aspirin Medication used to treat pain, fever, or inflammation. Asthma Allergic condition that causes the airways to become inflamed, narrow, and swollen. Autism Serious developmental disorder that impairs the ability to communicate and interact. Bacteria Microscopic living organisms, usually one-celled, that can be found everywhere. Basal layer The deepest layer of the five layers of the epidermis. Bile ducts Series of thin tubes that go from the liver to the small intestine. Bladder Membranous sac in which urine is collected for excretion. Bladder infection Most common UTI, or urinary tract infection, usually caused by bacteria. Body mass index (BMI) Measure of body fat based on height and weight. Bordetella pertussis Type of bacteria that causes whooping cough. Bronchi Any of the major air passages of the lungs which diverge from the windpipe. Bronchial tree Branching system of bronchi and bronchioles, conducting air from the windpipe into the lungs. Bronchioles Any of the minute branches into which the bronchi divide. Bronchiolitis Inflammation of the bronchioles. Bronchitis Inflammation of the mucous membrane in the bronchial tubes. Calamine lotion A medication used to treat mild itchiness. Campylobacter Bacteria that can get into your system if you eat undercooked poultry or food that has touched raw or undercooked poultry. It is a common cause of intestinal infection. Candida Yeastlike parasitic fungus that can cause infection. Capillary Smallest blood vessels in the body. Cellular metabolism Set of chemical reactions that occur in living organisms in order to maintain life. Cellulitis Common and potentially serious bacterial skin infection. Cerebellum Part of the brain at the back of the skull. Its function is to coordinate and regulate muscular activity. Cerebral palsy Condition marked by impaired muscle coordination, typically caused by damage to the brain before or at birth. Chemical pinkeye Inflammation of the eye caused by getting liquids, fumes, or chemicals in the eye. Chickenpox (varicella) A highly contagious viral infection causing an itchy, blister-like rash on the skin. Cilia Short microscopic hairlike vibrating structures found in large numbers on the surface of certain cells. Circadian rhythm Physical, mental, and behavioral changes that follow a daily cycle. They respond primarily to light and darkness. Circulatory system The system that circulates blood and lymph through the body, consisting of the heart, blood vessels, blood, lymph, and the lymphatic vessels and glands. Coblation Method for removing tonsils and adenoids using radiofrequency. Cochlea Spiral cavity of the inner ear containing the organ of Corti, which produces nerve impulses in response to sound vibrations. Cochlear nerve (auditory nerve) Nerve that carries auditory sensory information from the cochlea of the inner ear directly to the brain. Colloidal oatmeal Medication used as a moisturizer to treat or prevent dry, rough, scaly, itchy skin and minor skin irritations. Conjunctiva Mucous membrane that covers the front of the eye and lines the inside of the eyelids. Conjunctivitis (pinkeye) Inflammation of the conjunctiva. Constipation Condition in which there is difficulty in emptying the bowels, usually associated with hardened feces. Contagion The communication of disease from one person to another by close contact. Continuous positive airway pressure (CPAP) Treatment method for patients who have sleep apnea. Cornea Transparent layer forming the front of the eye. Corticosteroids Steroid hormones produced in the adrenal cortex or made synthetically. Croup Inflammation of the larynx and trachea in children, causing breathing difficulties. Curette Surgical instrument used to remove material by a scraping action. Cyclospora Parasite that can cause symptoms of gastroenteritis, as well as infections of the liver, bile ducts, gallbladder, and pancreas. Dermis Layer of skin between the epidermis and subcutaneous tissues. Diabetes Disease in which the body's ability to produce or respond to the hormone insulin is impaired, resulting in abnormal metabolism of carbohydrates and elevated levels of glucose in the blood and urine. Diaphragm Part of respiration, it's the dome-shaped sheet of muscle that separates the chest from the abdomen. Diarrhea Loose, watery stools (bowel movements). Digestion The process of breaking down food by mechanical and enzymatic action in the alimentary canal into substances that can be used by the body. Digestive juices Secretions of the stomach glands important for breaking down starches, proteins, and fats. Digestive system System by which ingested food is acted upon by physical and chemical means to provide the body with absorbable nutrients and to excrete waste products. E-I Return to top Ear canal Passage made of bone and skin leading to the eardrum. Electrocautery Process often used in surgery to remove unwanted or harmful tissue. It can also be used to burn and seal blood vessels. Encephalitis Inflammation of the brain. ENT Field of medicine involving diagnosis and treatment of the ears, nose, and throat. Enterovirus Virus which typically occurs in the gastrointestinal tract. Epidermis Surface of the skin, overlying the dermis. Epinephrine Medication used to treat life-threatening allergic reactions caused by insect bites or stings, foods, medications, latex, and other causes. Equilibrium State of physical balance. Erysipelas A bacterial infection of the skin's outer layers. Escherichia coli (E. coli) Bacteria which is a common cause of gastroenteritis. Esophagus Part of the alimentary canal that connects the throat to the stomach. Ethmoid sinus Part of the paranasal sinus system located between the nose and eyes. Eustachian tube Narrow passage leading from the pharynx to the cavity of the middle ear, permitting the equalization of pressure on each side of the eardrum. Febrile seizure Seizure associated with a high body temperature but without any serious underlying health issue. Fifth disease (erythema infectiosum) Viral illness characterized by a red rash on the face. Flange Means by which PE tubes are secured in the ear. Foot-and-mouth-disease Viral disease of cattle and sheep. Not to be mistaken for hand-foot-and-mouth disease, a common childhood virus. Frontal sinus A hollow space in the bones situated behind the brow ridges. Fungus Parasitic spore-producing organisms that include molds, mildews, and yeasts. Gallbladder Small organ beneath the liver, in which bile is stored after secretion by the liver and before release into the intestine. Gangrene Localized death and decomposition of body tissue, resulting from either obstructed circulation or bacterial infection. Gastroenteritis Inflammation of the stomach and intestines which causes vomiting and diarrhea. Glucose Simple sugar which comes from the foods we eat; an important energy source. Group A Streptococcus Bacterium that can cause many different infections, ranging from minor illnesses to very serious and deadly diseases. Gut flora (microbiome) Complex community of microorganisms that live in the digestive tract. Hand-foot-and-mouth disease A common illness of infants and children under 10 years old characterized by fever, sores in the mouth, and a rash with blisters. Head lice Tiny insects that feed on blood from the human scalp. Helicobacter pylori (H. pylori) Spiral-shaped bacteria that likely spread through unclean food, water, or eating utensils, and contact with an infected person's saliva and other body fluids. Human herpesvirus 6 (HHV-6) Common, contagious virus and most common cause of the infection known as roseola. Hyaline cartilage Translucent bluish-white type of cartilage present in the joints, the respiratory tract, and the immature skeleton. Ibuprofen Drug used to treat fever and mild to severe pain. Immune system The body's defense against infectious organisms and other invaders. The immune system includes the innate immune system, present at birth, and the adaptive, or acquired immune system, developed by the body over time to fight specific pathogens. Immunization The action of making a person immune to infection, typically by inoculation. Impetigo Contagious bacterial skin infection forming pustules and yellow crusty sores. Incubation time Time between exposure to a virus and development of symptoms. Incus Small anvil-shaped bone in the middle ear, transmitting vibrations between the malleus and stapes. Influenza (flu) Highly contagious viral infection of the respiratory passages which causes fever and severe aching; often occurs in epidemics. Inner ear Semicircular canals and cochlea embedded in the temporal bone which form the organs of balance and hearing. Insulin Hormone produced in the pancreas which regulates the amount of glucose in the blood. Intercostal muscles Muscles situated between the ribs. Intercostal retractions Movement that occurs when the muscles between the ribs pull inward. Intestinal tract Organ system which takes in food, digests it to extract and absorb energy and nutrients, and excretes the waste. Iris Thin, circular structure in the eye, responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina. Irritant Toxic, bacterial, physical, or chemical substance which causes irritation. J-O Return to top Keratin A tough, fibrous protein produced by keratinocytes in the skin. Keratinocytes Cells which comprise most of the epidermis. Kidney Each of a pair of organs in the abdominal cavity which excrete urine. Kidney infection Type of urinary tract infection (UTI) that commonly begins in the bladder and moves upstream to one or both of the kidneys. Kidney stone Small "pebbles" of salt and mineral in the urine, causing great pain. Large intestine (colon) Collective term for the cecum, colon, and rectum. Larynx The hollow muscular organ forming an air passage to the lungs and holding the vocal cords. Also known as the voice box. Ligament A short band of tough, flexible fibrous connective tissue which connects two bones or cartilages or holds together a joint. Lipid layer One of three layers of the tear film in the eye, the lipid layer prevents evaporation of aqueous tears and drying. Listeria Bacterial infection which can come from deli meats, undercooked pork and poultry, produce, and seafood. Liver Part of the digestive system, the liver is a large organ which filters unwanted substances out of the blood. Louse Parasitic insect which lives on the skin. Lower respiratory tract Part of the respiratory system which includes the portion of the larynx below the vocal folds, trachea, bronchi, and bronchioles. Lungs Primary organs of the respiratory system, located within the ribcage, where breathing occurs. Lymph nodes Part of the lymphatic system, these are small bean-shaped structures located in many parts of the body which filter lymphatic fluid. Lymph vessels Part of the lymphatic system, these are thin-walled vessels, or tubes, that carry lymph. Lymphatic system An important part of the immune system, the function of which is to trap and destroy invading viruses and bacteria. Macules Flat, discolored areas of a rash on the skin; a symptom of the measles. Malleus One of the three ossicles found in the middle ear. Mast cells Type of white blood cell that releases histimine during an allergic response. Maxillae sinus Largest of the paranasal sinuses, located near the nose. Measles (rubeola) Highly contagious viral illness which can be prevented by the MMR vaccination. Melanin Pigment produced by melanocytes. Melanocytes Cells found in the basal layer of the skin which produce pigment. Melatonin Hormone which regulates the natural sleep-wake cycle. Meninges Membrane covering the brain and spinal cord. Meningitis Inflammation of the membrane covering the brain and spinal cord. Methicillin-resistant Staphylococcus aureus (MRSA) Bacteria which can cause impetigo, treatable only with special antibiotics. Middle ear Part of the ear where the ossicles are located. Mite Tiny spider-like creature that causes scabies. Mucous membrane Tissue which secretes mucus, and lines many body cavities and tubular organs including the gut and respiratory passages. Mucus Slimy substance secreted by mucous membranes and glands for lubrication and protection. Nasal cavity The inside of the nose. Nasal epithelium Tissue that lines the nasal cavity. Nasal septum Dividing wall that runs down the middle of the nose, separating the two nasal cavities, each of which ends in a nostril. Nausea Feeling of sickness with an inclination to vomit. Night terrors (sleep terrors) Traumatic sleep incidents causing intense fear. Someone experiencing a night terror is difficult to awaken, and will have no memory of it. Nightmare A frightening or unpleasant dream. Nits Eggs of head lice. Norovirus Virus which can cause gastroenteritis. Nostrils Two external openings of the nasal cavity that admit air to the lungs and smells to the olfactory nerves. Nymph One of the three stages of the development of a louse. Obesity Having far too much body fat; in children, having a BMI at or above the 95th percentile for children and teens of the same age and sex. Obstructive sleep apnea Condition causing a person to stop breathing during sleep due to blockage in the upper airway. Ocular surface Surface of the eye consisting of the conjunctiva and the cornea, bordered by the upper and lower eyelids. Olfactory nerve Nerve which transmits impulses about odors to the central nervous system, where they are perceived by the sense of smell. Ossicles Three small bones in the middle ear that transmit incoming sound waves to the inner ear. Osteomyelitis Inflammation of the bone or bone marrow, usually due to infection. Otitis externa (swimmer's ear) Infection of the outer ear and ear canal. Otitis media Infection of the middle ear. Outer ear Outer visible portion of the ear that collects and directs sound waves toward the tympanic membrane. P-Z Return to top Pancreas Part of the digestive system; a large gland that secretes digestive enzymes and the hormones insulin and glucagon. Papules Symptom of the measles; solid, red, raised areas on the skin. Parainfluenza virus (human parainfluenza virus, HPIV) Virus which most commonly causes croup. Paranasal sinuses Air-filled chambers which surround the nasal cavity. Parasite Organism that lives in or on another and takes its nourishment from that other organism. Parvovirus B19 Virus which causes fifth disease. Pathogen Bacterium, virus, or other microorganism that can cause disease. Penicillin Antibiotic produced naturally by certain blue molds, and now usually prepared synthetically. Pertussis (whooping cough) Contagious bacterial disease chiefly affecting children, characterized by convulsive coughs followed by a whoop. Pharynx Membrane-lined cavity behind the nose and mouth, connecting them to the esophagus. Pinna (auricle) The outer, visible part of the ear. Pneumonia Lung inflammation caused by bacterial or viral infection, in which the air sacs fill with pus and may become solid. Pressure equalization (PE) tubes (ear tubes, tympanostomy tubes, myringotomy tubes, ventilation tubes) Tiny cylinders surgically placed through the eardrum to allow air into the middle ear. Rapid eye movement (REM) Erratic motions of a person's eyes occurring in REM sleep. Rectum The final section of the large intestine, terminating at the anus. Recurrent middle ear infections Four or more ear infections within 12 months. Reflux The flow of a fluid through a vessel or valve in the body in a direction opposite to normal. Respiratory syncytial virus (RSV) A type of virus that causes disease of the respiratory tract; a major cause of bronchiolitis and pneumonia in young children. Respiratory system (respiratory tract) The passage formed by the mouth, nose, throat, and lungs, through which air passes during breathing. Reye's syndrome A life-threatening metabolic disorder in young children. Rheumatic fever An inflammatory disease that can develop as a complication of inadequately treated strep throat or scarlet fever. Rhinovirus Infections which cause the common cold. They may also cause sore throats, ear infections, and infections of the sinuses. Roseola A common viral infection that mostly affects children between the ages of six months and three years. Rotavirus An infection that causes diarrhea. Saliva A watery liquid secreted into the mouth by glands, it provides lubrication for chewing and swallowing, and aids digestion. Salmonella Food poisoning caused by infection with the Salmonella bacterium. Scabies An itchy skin condition caused by a tiny burrowing mite. Scarlet fever (scarlatina) An infection that can develop in people with strep throat, characterized by a bright red rash on the body, usually accompanied by a high fever and sore throat. Sclera The white outer layer of the eyeball. Sebum Oily substance secreted by the sebaceous glands that helps keep the skin and hair moisturized. Semicircular canals Along with the vestibule, these are organs in the ear that help maintain balance. Sensitization Immune system process in which exposure to an antigen results in the development of hypersensitivity. Sepsis The body's overwhelming and life-threatening response to infection that can lead to tissue damage, organ failure, and death. Shigella Bacteria frequently found in water polluted with human feces. Shigellosis (bacillary dysentery) Dysentery caused by the bacteria Shigella. Shingles Viral infection that causes a painful rash, caused by the same virus as chickenpox. Sickle cell disease Severe hereditary form of anemia in which red blood cells are distorted into a crescent shape. It is most common among those of African descent. Sleep apnea Potentially serious sleep disorder in which breathing repeatedly stops and starts. Sleepwalking Walking around and sometimes performing other actions while asleep. Small intestine The part of the intestine that runs between the stomach and the large intestine. Spasmodic croup Croup caused by allergy or reflux from the stomach. Sphenoid sinus Either of two large sinuses in the sphenoid bone, which is behind the nose between the eyes. The sphenoid sinuses are lined with cells that make mucus to keep the nose from drying out. Sphincter Valve which guards or closes an opening or tube. Stapes Small stirrup-shaped bone in the middle ear, which transmits vibrations from the incus to the inner ear. Staphylococcus Bacteria that cause pus formation, especially in the skin and mucous membranes. Steroids Medication used to decrease swelling and inflammation. Stratum corneum Outermost layer of the epidermis. Strep throat Infection of the throat and tonsils caused by group A Streptococcus bacteria. Streptococcus Bacteria which causes strep throat. Stridor Coarse musical sound which may accompany breathing when a child has viral croup. Subcutaneous layer Innermost layer of the skin, made up of fat. T&A surgery Surgery to remove the tonsils and adenoids. Tear film Thin layer formed by the tears that spreads across the eye's surface every time a person blinks. Thrush Infection of the mouth caused by the yeast-like fungus Candida. Tonsillectomy Surgical removal of the tonsils. Tonsillitis Inflammation of the tonsils. Tonsils Two small masses of lymphoid tissue in the throat, one on each side of the root of the tongue. Toxoplasma gondii (T. gondii) Parasite that can only reproduce in cats and is passed in their feces. It can cause gastroenteritis when ingested. Trachea Large membranous tube reinforced by rings of cartilage, extending from the larynx to the bronchial tubes and conveying air to and from the lungs. Also known as the windpipe. Tympanic membrane (eardrum) Membrane located between the outer and middle ear which vibrates in response to sound waves. Ulcer Open sore on an external or internal surface of the body. Ultraviolet (UV) radiation Invisible rays that are part of the energy that comes from the sun. Upper respiratory infection Illness caused by an infection which involves the upper respiratory tract. Upper respiratory tract Part of the respiratory tract which includes the nose and nasal passages, sinuses, the pharynx, and the portion of the larynx above the vocal cords. Ureter Duct through which urine passes from the kidney to the bladder. Urethra Tube by which urine is conveyed out of the body from the bladder. Urinary tract infection (UTI) Infection in any part of the urinary system -- kidneys, ureters, bladder, and urethra. Urine Watery, typically yellowish waste fluid stored in the bladder and discharged through the urethra. Uvula Fleshy extension at the back of the soft palate which hangs above the throat. Vaccination Inoculation for producing immunity against a disease. Varicella-zoster virus Herpes virus that causes chickenpox and shingles. Vestibular nerve Nerve which controls the sense of hearing; also pertinent to the sense of balance. Vestibule Part of the inner ear which, along with the cochlea and the semicircular canals, helps maintain balance. Viral pinkeye Inflammation of the conjunctiva in the eye caused by a virus. Virus Infective agent able to multiply only within the living cells of a host. Vomiting Ejecting matter from the stomach through the mouth. White blood cells Part of the body's immune system, they help the body fight infection and other diseases.