Copy of `Dorland's Medical Dictionary`

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Dorland's Medical Dictionary
Category: Health and Medicine > Medical Dictionary
Date & country: He/al/th a, US
Words: 39246


BK virus
a virus of the genus Polyomavirus that is a common cause of infection in childhood and remains dormant in the person who has been infected. It is believed to cause hemorrhagic cystitis and nephritis in immunocompromised persons.

black cataract
black or dark-colored opacity occurring in senile nuclear sclerotic cataract.

Black Creek Canal virus
a virus of the genus Hantavirus that causes hantavirus pulmonary syndrome, found in warm regions of the Americas; the vectors are rodents, especially cotton rats of genus Sigmodon.

black death
bubonic plague; see plague.

black fever
visceral leishmaniasis.

black induration
the hardening and pigmentation of the lung tissue seen in coal workers' pneumoconiosis.

black lung
coal workers' pneumoconiosis.

black substance
substantia nigra.

black tongue
black hairy tongue hairy tongue in which the hypertrophied filiform papillae are brown or black.

black widow spider antivenin
antivenin (Latrodectus mactans).

Blackfan-Diamond anemia
(blak´fan di´mәnd) Blackfan-Diamond syndrome congenital hypoplastic anemia.

blackhead
(blak´hed) a plug of keratin and sebum within the dilated orifice of a hair follicle. The dark color is caused not by dirt but by the discoloring effect of air on the sebum in the clogged pore. Infection may cause it to develop into a pustule or boil. See also acne vulgaris. Called also open comedo.

blackout
(blak´out) temporary loss of vision and momentary unconsciousness due to diminished circulation to the brain and retina. Blackout refers specifically to a condition which sometimes occurs in aviators resulting from increased acceleration, which causes a decrease in blood supply to the brain cells. The term can als...

blackwater fever
a severe complication of malaria characterized by intravascular hemolysis, hemoglobinuria, renal failure, and passage of dark brown or red urine, seen in association with intermittent quinine therapy, with Plasmodium falciparum infection in the nonimmune, or with interrupted exposure in the partially immune.

bladder
(blad´әr) a membranous sac, such as one serving as a receptacle for secretion. Called also cyst and vesica. urinary bladder.

bladder calculus
vesical calculus.

bladder cancer
malignancy of the urinary bladder; this is the most common site of malignancy of the urinary system. It affects men more often than women, and it is seen more often in persons over age 50. Suspected contributing factors include exposure to industrial substances such as aniline dyes, and to the toxins in cigarette smoke. T...

bladder cells
swollen cells in the epidermis of the tips of the fingers and toes of the embryo. Called also Zander cells.

bladder compliance
ability of the urinary bladder to stretch in response to pressure without being disrupted, expressed in milliliters per centimeter of water calculated as change in volume divided by change in pressure. The normal bladder has a compliance of no more than 2 cm increase in water pressure per 100 mL of fluid.

bladder neck
a constricted portion of the urinary bladder where its inferolateral surfaces meet at the opening of the urethra.

bladder reflex
the reflex contracting and emptying of the urinary bladder in response to filling, the first step in the micturition reflex; it can be voluntarily inhibited by impulses from the brain in patients with normal neurological function.

Blainville ears
asymmetry of the two ears.

Blair-Brown operation
repair of a cleft lip by the use of a lateral flap one-half the length of the lip.

Blalock-Hanlon operation
a palliative operation for transposition of the great vessels, consisting of the creation of an interatrial septal defect.

Blalock-Taussig operation
(bla´lok taw´sig) Blalock-Taussig shunt anastomosis of the subclavian artery to the pulmonary artery to shunt some of the systemic circulation into the pulmonary circulation; performed as palliative treatment of congenital pulmonary stenosis.

blanch
(blanch) to become pale.

bland diet
one that is free from any irritating or stimulating foods.

blanking period
a period of time during and after a pacemaker stimulus when the unstimulated chamber is insensitive to avoid sensing the electronic event in the stimulated chamber.

Blaskovics operation
an operation for ptosis of the upper eyelid, consisting of excision of the levator muscle and the tarsus through a conjunctival approach.

blast
(blast) an immature stage in cellular development before appearance of the definitive characteristics of the cell; used also as a word termination, as in ameloblast and trophoblast. blast cell. the wave of air pressure produced by the detonation of high-explosive bombs or shells or by other e...

blast cell
in one theory of development, the least differentiated, totipotential blood cell without commitment as to its particular series, from which all blood cells are derived, preceding a stem cell. Called also blast, hematoblast, hemoblast, and hemocytoblast.

blast cell leukemia
acute undifferentiated leukemia.

blast crisis
a sudden, severe change in the course of chronic granulocytic leukemia, characterized by an increased number of blasts (myeloblasts or lymphoblasts).

blastema
(blas-te´mә) in species with asexual reproduction, a group of cells that give rise to a new individual. in other species, including humans, a group of cells showing little or no differentiation that gives rise to an organ or part in either normal development or regeneration.

blastocoele
(blas´to-sēl) the fluid-filled central segmentation cavity of the mass of the blastula.

blastocyst
(blas´to-sist) the mammalian conceptus in the postmorula stage, consisting of an embryoblast (inner cell mass) and a thin trophoblast layer enclosing a blastocyst cavity.

blastocyte
(blas´to-sīt) an undifferentiated embryonic cell.

blastoderm
(blas´to-dәrm) collectively, the mass of cells produced by cleavage of a zygote, forming the hollow sphere of the blastula, or the cellular cap above a floor of segmented yolk in the discoblastula of telolecithal eggs.

blastodermic layer
germ layer.

blastogenesis
(blas″to-jen´ә-sis) development of an individual from a blastema (that is, by asexual reproduction). transmission of inherited characters by the germ plasm. morphological transformation of small lymphocytes into large lymphocytes (lymphoblasts) that accompanies lymphocyte activation.

blastogenic factor
lymphocyte-transforming factor.

blastoma
(blas-to´mә) pl. blastomas, blasto´mata A neoplasm composed of embryonic cells derived from the blastema of an organ or tissue. adj., blasto´matous., adj.

blastomere
(blas´to-mēr) one of the cells produced by cleavage of a fertilized oocyte (zygote). Called also cleavage cell.

Blastomyces
(blas″to-mi´sēz) a genus of pathogenic fungi growing as mycelial forms at room temperature and as yeastlike forms at body temperature; applied to the yeasts pathogenic for humans and other animals. B. dermati´tidis is the species that causes North American blastomycosis.

blastomycete
(blas″to-mi´sēt) any organism of the genus Blastomyces. any yeastlike organism.

blastomycosis
(blas″to-mi-ko´sis) infection with any yeastlike organism. an infection usually acquired through the pulmonary route, caused by Blastomyces dermatitidis. There may be suppurating tumors in the skin (cutaneous b.) or lesions in the lungs, bones, subcutaneous tissues, liver, spleen, and kidneys (systemic b.)...

blastopore
(blas´to-por) the opening of the archenteron to the exterior of the embryo at the gastrula stage.

blastospore
(blas´to-spor) a spore formed by budding, as in yeast.

blastula
(blas´tu-lә) pl. blas´tulae the usually spherical structure produced by cleavage of a zygote, consisting of a single layer of cells (blastoderm) surrounding a fluid-filled cavity (blastocoele); it follows the morula stage.

blastulation
(blas″tu-la´shәn) conversion of the morula to the blastula by development of a blastocoele.

bleb
(bleb) bulla (def. 1).

bleeder
(blēd´әr) any blood vessel cut during surgery that requires clamping, cautery, or ligature. slang term, now considered offensive, referring to a person who bleeds freely, especially one suffering from a condition in which the blood fails to clot properly, such as hemophilia.

bleeding
(blēd´ing) escape of blood from an injured vessel; see also hemorrhage. phlebotomy.

bleeding disorder
coagulopathy.

bleeding time
the time required for a standard-sized wound to stop bleeding; see bleeding time test.

bleeding time test
a test of bleeding time, used to screen for congenital or acquired platelet disorders; these measure the ability of platelets to stop bleeding and thus give an estimate of how many platelets there are and how well they are functioning. Normally bleeding should stop in 2 to 9 minutes. Qualitative platelet disorders, thrombocytop...

blennadenitis
(blen″ad-ә-ni´tis) myxadenitis.

blennoid
(blen´oid) mucoid.

blennorrhea
(blen″o-re´ә) any free discharge of mucus, especially a gonorrheal discharge from the urethra or vagina.

blennothorax
(blen″o-thor´aks) a pleural effusion containing mucus.

blennuria
(blen-u´re-ә) mucus in the urine.

Blenoxane
(blen-ok´sān) trademark for a preparation of bleomycin sulfate, an antineoplastic antibiotic.

bleomycin
(ble″o-mi´sin) an antitumor antibiotic obtained from cultures of Streptomyces verticellus. It binds to DNA and causes single-strand breaks and double-strand scissions, impairing DNA synthesis and inhibiting RNA and protein synthesis. Administered by injection as the sulfate salt to treat lymphomas, soft tissue sar...

blepharadenitis
(blef″ә-rad″ә-ni´tis) inflammation of the meibomian glands; called also blepharoadenitis.

blepharal
(blef´ә-ral) palpebral.

blepharectomy
(blef″ә-rek´tә-me) partial or complete excision of an eyelid.

blepharism
(blef´ә-riz″әm) spasm of the eyelid; continuous blinking.

blepharitis
(blef″ә-ri´tis) inflammation of the glands and lash follicles along the margin of the eyelids; symptoms include itching, burning, photophobia, mucous discharge, crusted eyelids, and loss of eyelashes. Warm saline compresses may be used to soften secretions, and the eyelids are cleansed thoroughly. Exudate an...

blepharoadenitis
(blef″ә-ro-ad″ә-ni´tis) blepharadenitis.

blepharoatheroma
(blef″ә-ro-ath″әr-o´mә) an encysted tumor or sebaceous cyst of an eyelid.

blepharochalasis
(blef″ә-ro-kal´ә-sis) hypertrophy and loss of elasticity of the skin of the upper eyelid.

blepharoconjunctivitis
(blef″ә-ro-kәn-junk″tĭ-vi´tis) inflammation of the eyelids and conjunctiva.

blepharoncus
(blef″ә-rong´kәs) a tumor on the eyelid.

blepharophimosis
(blef″ә-ro-fĭ-mo´sis) abnormal narrowness of the palpebral fissures.

blepharoplasty
(blef´ә-ro-plas″te) plastic surgery of an eyelid; called also tarsoplasty.

blepharoplegia
(blef″ә-ro-ple´jә) paralysis of an eyelid.

blepharoptosis
(blef″ә-rop-to´sis) (blef″ә-ro-to´sis) ptosis (def. 2).

blepharorrhaphy
(blef″ә-ror´ә-fe) suture of an eyelid. tarsorrhaphy.

blepharospasm
(blef´ә-ro-spaz″әm) spasm of the orbicular muscle of the eyelid.

blepharostat
(blef´ә-ro-stat″) an instrument for holding the eyelids and keeping them apart during surgical operations on the eye. Blepharostat.

blepharostenosis
(blef″ә-ro-stә-no´sis) blepharophimosis.

blepharosynechia
(blef″ә-ro-sĭ-nek´e-ә) growing together or adhesion of the eyelids.

blepharotomy
(blef″ә-rot´ә-me) surgical incision of an eyelid; called also tarsotomy.

Blessig cysts
cystic spaces formed at the periphery of the retina.

blind
(blīnd) not having the sense of sight. pertaining to an experiment in which one or more of the groups receiving, administering, and evaluating treatment are unaware of which treatment any particular recipient is getting. See single blind, double blind, and triple blind.

blind fistula
an abnormal passage open at one end only, opening on the skin (external blind fistula) or on an internal surface (internal blind fistula).

blind loop syndrome
stasis syndrome.

blind spot
optic disk. mental scotoma.

blindness
(blīnd´nis) lack or loss of ability to see; see also vision and legal blindness. The five leading causes of blindness in the United States are age-related macular degeneration, cataract, glaucoma, diabetic retinopathy, and atrophy of the optic nerve.

blink reflex
corneal reflex.

blister
(blis´tәr) a vesicle, especially a bulla. blood blister a vesicle having bloody contents, as may be caused by a pinch or bruise. fever blister herpes febrilis. water blister one with clear watery contents.

Blocadren
(blok´ә-dren) trademark for a preparation of timolol maleate, a beta-adrenergic blocking agent used as an antihypertensive agent and in treatment of myocardial infarction and migraine.

Bloch-Sulzberger syndrome
(blok´ sulz´bәr-gәr) incontinentia pigmenti.

block
(blok) obstruction. to cause an obstruction. regional anesthesia. heart block.

block anesthesia
regional anesthesia.

blockade
(blok-ād´) in pharmacology, the blocking of the effect of a neurotransmitter or hormone by a drug. in histochemistry, a chemical reaction that modifies certain chemical groups and blocks a specific staining method. regional anesthesia.

blocked pleurisy
encysted pleurisy.

blocker
(blok´әr) something that blocks or obstructs a passage or activity; see also antagonist and blocking agent. α-blocker alpha-adrenergic blocking agent. β-blocker , beta-blocker beta-adrenergic blocking agent. p...

blocking
(blok´ing) interruption of an afferent nerve pathway (see block). inhibition of an intracellular biosynthetic process; metabolic block. thought blocking or thought deprivation; sudden cessation of the train of thought or speech, such as may occur in a period of extreme emotion or when a repre...

blocking agent
an agent that inhibits a biological action, such as movement of an ion across the cell membrane, passage of a neural impulse, or interaction with a specific receptor.