Glossary

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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.

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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.

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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.

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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.