{basal nucleus}{}{Nucleus at the base of the cerebrum involved in controlling motor functions.}

{base}{}{Molecule that is a proton acceptor; any substance that binds to hydrogen ions.}

{basement membrane}{}{Specialized extracellular material located at the base of epithelial cells and separating them from the underlying connective tissues.}

{bile}{}{Fluid secreted by liver and stored in gallbladder.}

{binding site}{}{Site on a hormone receptor where the hormone binds.}

{bipolar neuron}{}{One of the three categories of neurons consisting of a neuron with two processes—one dendrite and one axon—arising from opposite poles of the cell body.}

{blastocoel}{}{The space formed in the center of a mass of dividing cells in an embryo at the blastula stage.}

{blastopore}{}{The opening into the archenteron in a gastrula.}

{blastula}{}{Embryonic stage characterized by a hollow ball shape.}

{blood}{}{The primary transport medium of the body for oxygen and carbon dioxide, as well as nutrients, water, ions, and waste products of metabolism.}

{bolus}{}{A mass of food or liquid introduced into the digestive system; can also be a mass of liquid introduced into the circulatory system through a needle.}

{bone}{}{Connective tissue with a protein fiber and ground substance matrix.  Bone protects and supports other body structures.}

{brain}{}{The central processing organ of the nervous system.  The brain is typically divided into three portions: the cerebrum, the cerebellum, and the brain stem.}

{brain stem}{}{Portion of the brain that includes midbrain, pons, and medulla oblongata.}

{Broca's area}{}{Region of frontal lobe that coordinates complex muscular actions of mouth, tongue, and larynx, making speech possible.}

{bronchial tree}{}{Bronchi and their branches that carry air from trachea to alveoli of lungs.}

{bronchiole}{}{Small branch of a bronchus within lung.}

{bronchus [bronchi]}{}{Branch of trachea that leads to lung.}

{buffer}{}{Mixture of an acid and base that reduces any changes in pH that would otherwise occur in a solution when acid or base is added to the solution.}

{bulbourethral gland}{}{Glands that secrete viscous fluid into male urethra during sexual excitement; Cowper's glands.}

{bursa [bursae]}{}{Closed sac or pocket containing synovial fluid, usually found in areas where friction occurs.}