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Modern Biology

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nutrient
a substance or compound that provides nourishment (or food) or raw materials needed for life processes
vitamin
an organic compound that participates in biochemical reactions and that builds various molecules in the body
mineral
a natural, usually inorganic solid that has a characteristic chemical composition, an orderly internal structure, and a characteristic set of physical properties
dehydration
condition resulting from excessive water loss
digestion
the breaking down of food into chemical substances that can be used for energy
gastrointestinal tract
the digestive tract from the mouth to the anus, including the stomach and intestines
saliva
the watery fluid that is secreted by the salivary glands of the mouth, that softens and moistens food, and that begins digestion
pharynx
in flatworms, the muscular tube that leads from the mouth to the gastrovascular cavity; in animals with a digestive tract, the passage from the mouth to the larynx and esophagus
epiglottis
a structure that hangs at the entrance of the larynx and prevents food from entering the larynx and the trachea while swallowing
peristalsis
the series of rhythmic muscular contractions that move food through the digestive tract
gastric fluid
a liquid secreted by gastric glands in the stomach
ulcer
a lesion of the surface of the skin or a mucous membrane; sometimes occurs in the digestive system
cardiac sphincter
a circular muscle located between the esophagus and the stomach
chyme
the mixture formed in the stomach from digested food particles and gastric fluid
pyloric sphincter
the circular muscle that controls the flow of chyme from the stomach to the small intestine
gallbladder
a sac-shaped organ that stores bile produced by the liver
villus
one of the many tiny projections from the cells in the lining of the small intestine; increases the surface area of the lining for absorption
colon
a section of the large intestine
excretion
the process of eliminating metabolic wastes
renal cortex
the outermost portion of the kidney, makes up about a third of the kidney's tissue mass
renal medulla
the inner two-thirds of the kidney
renal pelvis
a funnel-shaped structure in the center of the kidney
urea
the principal nitrogenous product of the metabolism of proteins that forms in the liver from amino acids and from compounds of ammonia and that is found in urine and other body fluids
ammonia
a colorless gas that has an alkaline reaction in water; forms in nature as an end product of animal metabolism (formula, NH3)
urine
the liquid excreted by the kidneys, stored in the bladder, and passed through the urethra to the outside of the body
nephron
the functional unit of the kidney
Bowman's capsule
a tight ball of capillaries that retains cells and large molecules in the blood and passes wastes dissolved in water
glomerulus
a cluster of capillaries that is enclosed in a Bowman's capsule in a nephron of the kidney, where blood is filtered
renal tubule
the long, tubular portion of a nephron that produces and that takes urine to the renal pelvis of a kidney
filtration
the process of separating dissolved substances, such as impurities in the blood by passing them through a porous material; occurs between the glomerulus and the Bowman's capsule in the nephrons of a kidney
reabsorption
the process in the kidneys by which materials return to the blood from the nephrons
secretion
the process by which the glands of the body release their substances; a substance produced by a gland
loop of Henle
in the kidney, the long, U-shaped part of a nephron that reabsorbs water and salts from the urine collected by the glomerulus
ureter
one of the two narrow tubes that carry urine from the kidneys to the urinary bladder
urinary bladder
a hollow, muscular organ that stores urine
urethra
the tube that carries urine from the urinary bladder to the outside of the body