Bma Illustrated Medical Dictionary

spine; 12 vertebrae in the thoracic spine;

5 vertebrae in the lumbar spine; 5 fused

vertebrae in the sacrum; and 4 fused ver-

tebrae in the coccyx. The top 24 vertebrae

are separated by discs of cartilage (see

disc, intervertebral). Each vertebra has a

hole in the centre throughwhich the

spinal cord runs, and processes to

which muscles are attached.

vertebrobasilar insufficiencyInter-

mittent episodes of dizziness, double

vision, weakness, and difficulty in speak-

ing caused by reduced blood flow to

parts of the brain. It is usually due to ath-

erosclerosisof the basilar and vertebral

arteries and other arteries in the base of

the brain. Vertebrobasilar insufficiency

sometimes precedes a stroke.

vertigoAn illusion that one or one’s

surroundings are spinning. Vertigo is

due to a disturbance of the semicircular

canalsin the inner ear or the nerve

tracts leading from them. Sudden-onset

vertigo is treated with rest and antihis-

tamine drugs, which, in some cases, are

also given to prevent recurrent attacks.

VERTEBRA vesicleA small blister, usually filled with

clear fluid, that forms at a site of skin

damage. The term is also used to refer to

any small sac-like structure in the body.

vestibuleA chamber. The vestibule in

the inner ear is a hollow chamber that

connects the 3 semicircular canals.

vestibulitisInflammation of the nasal

vestibule (the part of the nasal cavity

just inside the nostril), usually as a

result of bacterial infection.

vestibulocochlear nerveThe 8th cran-

ial nerve. It consists of 2 branches: the

vestibular nerve (concerned with balance)

and the cochlear nerve (concerned with

hearing). Each vestibulocochlear nerve

(1 on each side) carries sensory im-

pulses from the inner earto the brain,

which it enters between the pons and

medulla oblongata (in the brainstem).

A tumour of the cells that surround

the vestibulocochlear nerve (see acous-

tic neuroma) may cause loss of balance,

tinnitus, and deafness. Deafness may

also result from damage to the nerve,

which may be due to an infection, such

as meningitisor encephalitis, or to a

reaction to a drug such as streptomycin.

viabilityThe capability of independent

survival and development.

villusA minute finger-like projection from

a membranous surface. Millions of villi

are present on the mucous lining of the

small intestine. Each intestinal villus con-

tains a small lymphvessel and a network

VERTEBROBASILAR INSUFFICIENCY VILLUS

V

Capillary network

Villus

Vein

VILLI OF SMALL INTESTINE

Lymph vessel

Artery

VILLUS

Mucus-

producing cell

Cervical
vertebrae

Thoracic
vertebrae

Lumbar
vertebrae

Sacrum

Coccyx

LUMBAR VERTEBRA

THORACIC VERTEBRA

CERVICAL VERTEBRA

SPINE