Oat cell cancer: A
type of lung cancer in which the cells look like oats. Also
called small cell lung cancer.
OB: Short for obstetrics (or an obstetrician).
Obesity: Overweight. Please see MedicineNet site on OBESITY for
OB/GYN: A commonly used abbreviation. GYN is short for
gynecology (or a gynecologist).
Obsessive-compulsive: A form of personality (or personality
disorder) marked by obsessions and compulsions.
Obstetrician: A physician who delivers babies and is in the
practice of obstetrics.
Obstetrics: The art and science of managing pregnancy, labor and
the pueperium (the time after delivery).
Obtunded: Mentally dulled. Head trauma may obtund a person.
Occipital bone: The bone forming the rear (and rear bottom) of
Occiput: The back of the head.
Occular: Having to do with the eye.
Occult: Hidden. Occult blood is hidden from the eye but is
nontheless present and can be detected by chemical tests.
OCP: Oral contraceptive pill. Also known as "the pill".
Ocular: Having to do with the eye.
Oesophagus: Alternate spelling for esophagus.
Ointment: An ointment has an oil base whereas a cream is
water-soluble. (The word ointment comes from the Latin ungere
meaning anoint with oil).
Olfaction: The sense of smell. Olfactory apparatus: The whole
system needed to have a sense of smell.
Oligo-: Means just a few or scanty.
Oligodendroglioma: A type of brain tumor.
Oligohydramnios: Scant amniotic fluid: less than usual.
Oligomenorrhea: Scant menstruation. Less menstrual blood flow
Oligospermia: Fewer sperm than usual. Azospermia, by contrast,
means absolutely no sperm at all.
Oliguria: Less urination than normal.
Oligonucleotide: A short DNA molecule composed of relatively few
Omentum: A sheet of fat covered by peritoneum. The greater
omentum is attached to the bottom edge of the stomach and hangs
down in front of the intestines. The other edge is attached to
the transverse colon. The lesser omentum is attached to the top
edge of the stomach and extends to the undersurface of the
Colon - add the following to the end of the existing text: The
colon can be divided into ascending (right), transverse,
descending (left), and sigmoid segments. The ascending colon
includes the cecum which joins with the small bowel and also has
the appendix attached to it. Stool then proceeds up the
ascending colon toward the liver, then across to the left side
of the body via the transverse colon. Near the spleen, the colon
turns downward and becomes the descending colon which becomes
the sigmoid colon toward the pelvis.
Ommaya reservoir: A device implanted under the scalp and used to
deliver anticancer drugs to the fluid surrounding the brain and
Omphalocele: A birth defect with intestine protruding outside
the abdomen at the umbilicus. Due to a failure at 10 weeks'
embryonic development for the intestine, for a time normally
outside the abdomen, to return.
Oncogene: A gene that plays a normal role in cell growth and,
when altered, may contribute to the growth of a tumor. The word
oncogene (literally, cancer gene) is catchy but oversimplifies
the complex process of cancer.
Oncologist: A doctor who specializes in treating cancer.
Onycho-: Having to do with the nails.
Onychodystrophy: Malformation of the nails. Oo-: Prefix meaning
egg. Pronounced o'-o.
Onychoosteodysplasia: The nail-patella syndrome, an hereditary
condition with abnormally formed (dysplastic) or absent nails
and absent or underdeveloped (hypoplastic) kneecaps (patellae).
Other features include iliac horns, abnormality of the elbows
interfering with full range of motion (pronation and supination)
and kidney disease resembling glomerulonephritis which.is often
mild but can be progressive and lead to renal failure.
Onychoosteodysplasia is inherited as dominant gene. This means
that the disease can be transmitted by one affected parent. The
nail-patella gene locus found linked genetically to the ABO
blood group in1965 is now known to be in chromosome region 9q34.
Also called Turner-Kieser syndrome, and Fong disease.
Oocyte: A female germ cell in the works; a developing egg cell.
Oogonium: Ancestral cell that gives rise to oocytes.
Oophorectomy: The removal of one or both ovaries. Oophoritis:
Inflammation of the ovary.
Open reading frame: (genetics) An open reading frame in DNA has
no termination codon, no signal to stop reading the nucleotide
sequence, and so may be translated into protein.
Ophthalmoscope: A lighted instrument used to examine the inside
of the eye, including the retina and the optic nerve.
Ophthalmia: Inflammation of the eye.
Ophthalmic: Pertaining to the eye. An ophthalmic ointment is
designed for the eye.
Ophthalmologist: An eye doctor. A physician practicing
ophthalmology. An ophthalmologist is an M.D.
Ophthalmology: The art and science of eye medicine.
Ophthalmopathy: Eye disease.
Optic: Having to do with vision.
Optic neuroma: A benign tumor of the optic nerve.
Optic nerve: The nerve that carries Messages from the retina to
Optometrist: Professional trained to provide primary eye and
vision care and improve vision with glasses, contact lenses,
etc. An optometrist is an O.D. (Doctor of Optometry), not an
Oral: Having to do with the mouth.
Oral cancer: Cancer within the mouth. Please see MedicineNet
site on RAL CANCER for more information.
Oral surgeon: A dentist with special training in surgery of the
mouth and jaw.
Orbit: In medicine, the bony cavity in which the eyeball sits.
Orbital ridge: The bony ridge beneath the eyebrow.
Orchitis: Inflammation of the testis (male sex organ). There are
many causes of inflammation of the testis including infections
(such as mumps), diseases (such as polyarteritis nodosa), or
injury. Also called orchiditis.
Orchiectomy: The surgical removal of the testicles.
Orifice: An opening. The mouth for example is an orifice.
Oromandibular dystonia: Oro- refers to the mouth and mandibular
refers to the lower jaw. Oromandibular dystonia affects the
muscles of the jaw, lips, and tongue. The jaw may be pulled
either open or shut, and speech and swallowing can be difficult.
Oropharynx: The area of the throat at the back of the mouth.
Ortho-: Prefix meaning straight or erect.
Orthodontic treatment (dental braces): Please see MedicineNet
site on ORTHODONTIC TREATMENT for information on this subject.
Orthopedics: Literally, the practice of child straightening,
orthopedics is the branch of surgery broadly concerned with the
skeletal system (bones).
Orthopedist: An orthopedic surgeon.
Orthopod: Slang for orthopedist.
Orthopnea: The plight of a person who can only breath easily
when sitting straight or standing erect.
Orthostatic hypotension: A temporary low blood pressure
(hypotension) due usually to suddenly standing up (orthostatic).
Symptoms such as dizziness, feeling about to black out, and
tunnel vision can be due to insufficient blood flow to the
brain. The symptoms are typically worse when standing and
improve with lying down. Orthostatic hypotension may be
experienced by healthy people who rise quickly from a chair,
especially after a meal, and have a few seconds of
Osseous: Having to do with the bone.
Osteo-: Prefix meaning bone.
Osteoarthritis: Type of arthritis caused by inflammation,
breakdown and eventual loss of the cartilage of the joints. For
more information on this common type of arthritis, please see
the MedicineNet site on OSTEOARTHRITIS.
Osteochondroma: An abnormal solitary benign growth of bone and
cartilage typically at the end of a long bone. Osteochondromas
are usually discovered in persons 15 to 25 years of age. They
are typically detected when injured or they become large enough
to be noted.
Osteodystrophy (renal osteodystrophy): A combination of bone
disorders usually caused by chronic kidney failure (renal
disease). Please see the MedicineNet site on OSTEODYTROPHY for
Osteogenesis: The production of bone.
Osteogenesis imperfecta: Brittle bone disease.
Osteomalacia: Softening of the bone.
Osteomyelitis: Inflammation of the bone due to infection, for
example by the bacteria salmonella.
Osteonecrosis (aseptic necrosis or avascular necrosis):
Condition resulting from poor blood supply to an area of bone
causing bone death. For more information on this condition,
please see the MedicineNet site on OSTEONECROSIS.
Osteopath: An osteopathic physician who is a Doctor of
Osteopathy: A system of therapy founded in the 19th century
based on the concept that the body can formulate its own
remedies against diseases when the body is in a normal
structural relationship, has a normal environment and enjoys
Osteopetrosis: Stony bones; thickening of the bones, also called
Osteoporosis: Thinning of the bones with reduction in bone mass
due to depletion of calcium and bone protein, predisposing to
fractures. For more information, please see the MedicineNet site
Osteosarcoma: A cancer of the bone that is most common in
children. Also called osteogenic sarcoma.
Osteotomy: Taking out part or all of a bone.
Ostomy: An operation to create an opening from an area inside
the body to the outside. See glossary entry for colostomy.
Otitis: Inflammation of the ear.
Otitis externa: Inflammation of the external ear canal that
leads inward to the ear drum (tympanic membrane).
Otitis interna: Inflammation of the inner ear.
Otitis media: Inflammation of the middle ear, often due to an
infection. Very common in children.
Oto-: Prefix meaning ear.
Otolaryngologist: A doctor who specializes in treating diseases
of the ear, nose, and throat.
Otoscope: Instrument for looking in the ear. Today, otoscopic or
ophthalmoscopic heads can usually be attached to the base (which
supplies the electrical power) to look at the ears or eyes.
Ounce: A measure of weight equal to 1/16th of a pound or,
metrically, 28.35 grams. The abbreviation for ounce is oz. (An
ounce of prevention is reputedly worth a pound of cure.)
Outpatient: A patient who is not an inpatient (not
hospitalized). Outpatient care is called ambulatory care.
Ova: Two or more "ovums". (Ova is the plural of ovum).
Ovarian cancer: Cancer of the ovary. Most often due to ovarian
carcinoma. For more information on this important women's health
problem, please see the MedicineNet site on OVARIAN CANCER.
Ovaries: The pair of female reproductive organs that produce
eggs (ova) and hormones. They are located in the lower abdomen,
one on each side of the uterus.
Ovary: An ovary or "egg sac" is one of a pair of reproductive
glands in women. The ovaries produce the ovum or female egg
which is transferred through the fallopian tube for fertiliztion
by the sperm. The ovary also produces both the hormones estrogen
Overgrowth: Just what it sounds like: excessive growth.
Overgrowth syndromes: Conditions with multiple abnormalities
including excessive growth. Early overgrowth syndromes that
affecting children include the fragile X and Beckwith-Wiedemannn
syndromes. Overactivity of the pituitary gland with
overproductiuon of growth hormone causes overgrowth before
adolescence and a distinctive pattern of overgrowth called
Overweight: Obesity. Please see MedicineNet site on OBESITY for
Ovulation: The release of the ripe egg from the ovary.
Ovum: An ovum is an egg that exists in the ovary of the female.
This egg is called the female "gamete" or sex cell. It combines
with the male gamete, called a sperm, to form a zygote. This
formation process is called "fertilization." (see sperm,
Oxyuris: A group of intestinal worms that includes pinworm.
oz.: Abbreviation for ounce.