gas exchange (uptake of oxygen; disposal of carbon dioxide)
immune and lymphatic system
body defense (fighting infections and cancer)
disposal of metabolic wastes; regulation of osmotic balance in blood
coordination of body activities (e.g., digestion, metabolism)
coordination of body activities; detection of stimuli and formulation of responses to them
protection against mechanical injury, infection, drying out
body support, protection of internal organs
the internal environment of vertebrates, consisting of the fluid filling the spaces between cells
the steady-state physiological condition of the body
A primary mechanism of homeostasis, whereby a change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation.
A physiological control mechanism in which a change in some variable triggers mechanisms that amplify the change.
the totality of an organism's chemical reactions
Organisms with bodies that are warmed by heat generated by metabolism. This heat is usually used to maintain a relatively stable body temperature higher than that of the external environment.
Organisms that do not produce enough metabolic heat to have much effect on body temperature.
basal metabolic rate (BMR)
the minimum number of kilocalories a resting animal requires to fuel itself for a given time
standard metabolic rate (SMR)
The metabolic rate of a resting, fasting, and nonstressed ectotherm at a particular temperature.
a diet that is chronically deficient in calories
a diet that is chronically excessive in calories
essential fatty acid
the certain unsaturated fatty acids that animals can't make
essential amino acid
Amino acids that an animal cannot synthesize itself and must be obtained from food. Eight of these are essential in the human adult.
an organic molecule required in the diet in very small amounts; they serve mainly as coenzymes or parts of coenzymes
in nutrition, a chemical element other than hydrogen, oxygen, or nitrogen that an organism requires for proper body functioning
An aquatic animal, such as a sponge, clam, or baleen whale, that feeds by sifting small food particles from the water.
An organism that lives in or on its food source, eating its way through the food
a heterotroph, such as an earthworm, that eats its way through detritus, salvaging bits and pieces of decaying organic matter
an animal that lives by sucking nutrient-rich fluids from another living organisms
animals that eat relatively large pieces of food
A heterotrophic mode of nutrition in which other organisms or detritus are eaten whole or in pieces. step one of digestion
process of breaking down food into molecules small enough for the body to absorb; step two of digestion
the uptake of small nutrient molecules by an organism's own body; the third main stage of food processing, following digestion
the passing of undigested materials out of the digestive compartment; step four of digestion
The joining of food vacuoles and lysosomes to allow chemical digestion to occur within the cytoplasm of a cell.
The breakdown of food outside cells
complete digestive tract
A digestive tube that runs between a mouth and an anus; also called alimentary canal. An incomplete digestive tract has only one opening.
A digestive tract consisting of a tube running between a mouth and an anus
rhythmic waves of contractions of smooth muscle that push food along the digestive tract
A ringlike valve consisting of modified muscles in a muscular tube, such as a digestive tract; closes off the tube like a drawstring.
Exocrine glands associated with the oral cavity; the secretions of salivary glands contain substances to lubricate foods, adhere together chewed pieces into a bolus, and begin the process of chemical digestion
A gland with dual functions: The nonendocrine portion secretes digestive enzymes and an alkaline solution into the small intestine via a duct; the endocrine portion secretes the hormones insulin and glucagon into the blood.
the largest organ in the vertebrate body; it performs diverse functions such as producing bile, preparing nitrogenous wastes for disposal, and detoxifying poisonous chemicals in the blood
an organ that stores bile and releases it as needed into the small intestine
A salivary gland enzyme that hydrolyzes starch
a lubricated ball of chewed food
An area in the vertebrate throat where air and food passages cross; in flatworms, the muscular tube that protrudes from the ventral side of the worm and ends in the mouth.
a cartiliginous flap that blocks the top of the windpipe, the glottis, during swallowing, which prevents the entry of fluid or food into the respiratory system
a channel that conducts food, by peristalsis, from the pharynx to the stomach
an enlarged and muscular saclike organ of the alimentary canal
the collection of fluids secreted by the epithelium lining the stomach
An enzyme present in gastric juice that begins the hydrolysis of proteins
The inactive form of pepsin that is first secreted by specialized (chief) cells located in gastric pits of the stomach.
a mixture of recently swallowed food and gastric juice
In the vertebrate digestive tract, a muscular ring that regulates the passage of food out of the stomach and into the small intestine
the longest section of the alimentary canal; it's the principle site of the enzymatic hydrolysis of food macromolecules and the absorption of nutrients
The first section of the small intestine, where chyme from the stomach mixes with digestive juices from the pancreas, liver, and gallbladder as well as from gland cells of the intestinal wall.
A mixture of substances that is produced in the liver but stored in the gallbladder and that enables formation of fat droplets in water as an aid in the digestion and absorption of fats
an enzyme found in the duodenum; specific for peptide bonds adjacent to certain amino acids
an enzyme found attached to the intestinal lining; it plits into small peptides
an enzyme found within the small intestine that splits off one amino acid at a time beginning at the end of the polypeptide that has a free carboxyl group
An enzyme found within the small intestine that splits off one amino acid at a time, beginning at the opposite end of the polypeptide containing a free carboxyl group.
A team of enzymes that hydrolyze DNA and RNA into their component nucleotides
the process that keeps tiny fat droplets from coalescing
an enzyme that hydrolyzes fat molecules in the intestinal lumen
fine, finger-like projections of the epithelial cells in the lumen of the small intestine that increases its surface area
fingerlike projections of the inner surface of the small intestine
A tiny lymph vessel extending into the core of an intestinal villus and serving as the destination for absorbed chylomicrons
small intracellular globules composed of fats that are mixed with the cholesterol and coated with special proteins
hepatic portal vessel
A large circulatory channel that conveys nutrient-laden blood from the small intestine to the liver, which regulates the blood's nutrient content
a digestive hormone secreted by the stomach; stimulates the secretion of gastric juice
a category of hormones secreted by the wall of the duodenum
a hormone released from the walls of the duodenum in response to the presence of amino acids or fatty acids
the last section of the digestive system, where water is absorbed from food and the remaining material is eliminated from the body
the tubular portion of the vertebrate alimentary tract between the small intestine and the anus; functions mainly in water absorption and the formation of feces
a blind outpocket of a hollow organ such as an intestine
A small, fingerlike extension of the vertebrate cecum; contains a mass of white blood cells that contribute to immunity.
mouth, pharynx, esophagus, stomach, intestines, liver, pancreas, anus
heart, blood vessels, blood
lungs, trachea, other breathing tubes
immune and lymphatic system
bone marrow, lymph nodes, thymus, spleen, lymph vessels, white blood cells
kidneys, ureters, urinary bladder, urethra
pituitary, thyroid, pancreas, other hormone-secreting glands
ovaries, testes, and associated organs
brain, spinal cord, nerves, sensory organs
skin and its derivatives (e.g., hair, claws, skin glands)