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(bŭl′ŭs) [L. bulla, bubble] Like a blister or vesicle.


A person who uses physical or psychological means or force to get his or her way, esp. by intimidating or hurting others who may be smaller or weaker.


blood urea nitrogen.


(bŭn′dĕl) 1. A group of fibers. SYN: fasciculus. 2. A multicomponent clinical intervention.

Arnold b. SEE: under Arnold, Friedrich.

atrioventricular b. ABBR: A-V bundle. Bundle of His.

cingulate b. Cingulum.

cingulum b. Cingulum.

efferent cochlear b. Olivocochlear b.

ground b. A bundle of nerve fibers immediately surrounding the gray matter of the spinal cord. It is divided into three regions, the anterior, lateral, and posterior bundles, which lie in the corresponding funiculi.

b. of His SEE: under His, Wilhelm Jr.

medial forebrain b. A diffuse limbic tract of lightly myelinated and unmyelinated axons interconnecting the forebrain, hypothalamus, and brainstem. Along with the dorsal longitudinal fasciculus, the medial forebrain bundle is the main pathway by which monoaminergic axons from cells in the hindbrain and midbrain reach the striatum, the limbic system, and the cerebral cortices of the forebrain.

nigrostriate b. A dopaminergic axon tract from the substantia nigra to the striatum in the basal ganglia. Activation of the nigrostriate bundle inhibits the striatum, which normally lowers the activity of motor programs. In Parkinson disease, neurons in the substantia nigra are damaged, and their effect on the striatum is reduced; the result is unchecked activity of the striatum and an excessive damping of motor programs, i.e., hypokinetic behavior. SYN: nigrostriatal fibers.

olivocochlear b. An axon tract that originates in the superior olivary nuclei of the hindbrain. The tract exits the brainstem and runs in the vestibulocochlear nerve (CN VIII), eventually synapsing on hair cells in the cochlea in the inner ear. The olivocochlear bundle is one pathway by which the auditory system can modify its perception of sound. SYN: efferent cochlear bundle.

thoracodorsal b. The nerve, artery, and vein that adjoin the latissimus dorsi muscle about 1.5 in (4 cm) below the axillary vein. The bundle defines the lateral border of the axilla in axillary lymph node dissection for breast cancer.

ventilator b. A cluster of four evidenced-based safety measures that decrease the risk to patients of mechanical ventilation while in the intensive care unit. The elements of the bundle may include elevating the head of the patient's bed, administering medications to prevent deep venous thrombosis, administering medications to reduce the incidence of GI bleeding, and giving the ventilated patient periodic intermissions ...

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