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food being taken in, taken apart, and taken up


animals that eat mainly plants or algae, such as cattle, parrotfish, and termites


animals that eat mostly other animals, such as sharks, hawks, and spiders


animals that regularly consume animals as well as plants or algae, such as humans, cockroaches, and crows

essential nutrients

materials that an animal's cells require but cannot synthesize; include minerals and preassembled organic molecules--amino acids, fatty acids, vitamins, minerals


number of essential amino acids


proteins in animal products are _________ amino acids, meaning they provide all essentials in proper proportions


proteins in plants are ___________ amino acids, meaning they are missing one or more essentials

essential fatty acids

_______________ are unsaturated and often found in seeds, grains, and vegetables


organic molecules with diverse functions that are required in small amounts; can be water soluble or fat soluble


number of essential vitamins for humans

water soluble

B complex and vitamin C are what classification of vitamins?

fat soluble

Vitamins A, K, and D are what classification of vitamins?


inorganic nutrients, such as zinc and potassium, which are needed in small amounts from 1 mg to 2500 mg per day


the result of a diet that consistently supplies less chemical energy than the body requires


the long term absence from the diet of one or more essential nutrients


the study of human health and disease that has been helpful in giving insight to human nutrition


the act of eating

suspension feeders

animals that sift small food particles from water (whales)

substrate feeders

animals that live in or on their food source (maggots)

fluid feeders

animals that suck nutrient rich fluid from a living host (mosquitoes)

bulk feeders

animals that eat relatively large pieces of food (snakes, humans)


when food is broken down into molecules small enough for the body to absorb

enzymatic hydrolysis

the splitting process that catalyzes digestion

mechanical digestion

the process that breaks food into smaller pieces, increasing surface area to make it available for chemical processes


this occurs when an animal's cells take up small molecules, such as amino acids and sugars


this occurs when undigested material passes out of the digestive system

intracellular digestion

the hydrolysis of food inside vacuoles that begins after a cell engulfs food

extracellular digestion

the breakdown of food in compartments that are continuous with the outside of the animal's body

gastrovacular cavity

this functions in digestion as well as in the distribution of nutrients throughout the body; found in animals with a simple body plan

alimentary canal

a digestive tube with two openings, a mouth and an anus, both of which are further compartmentalized


alternating waves of contraction and relaxation in the smooth muscles lining the alimentary canal that move food along; enables digestion while lying down


ringlike valves formed by muscular layers at junctions between specialized compartments that regulate the passage of material

oral cavity

the mouth; where ingestion and the initial steps of digestion occur; presence of food stimulates a nervous reflex that causes salivary glands to deliver saliva

salivary glands

stimulated by presence of food to deliver saliva through ducts to the oral cavity; initiate chemical digestion and protect oral cavity


an enzyme in saliva that hydrolyzes starch and glycogen into smaller polysaccharides and the disaccharide maltose


a ball of partly digested food selected by the tongue that moves from the back of the mouth to the pharynx for further digestion


the throat region that opens to two passageways: 1) esophagus, 2) trachea


this connects the pharynx to the stomach; contains striated muscle at the top and smooth muscle further down to help peristalsis


the organ that is located just below the diaphragm in the upper abdominal cavity; primarily stores food and continues digestion, though it does absorb a few nutrients into the bloodstream; can stretch to accommodate 2L of food and liquid; secretes gastric juices

gastric juice

a digestive fluid that is churned with food


a mixture of gastric juices and partly digested food; its HCl denatures proteins


a gastric juice that contains pepsin


a protein-digesting enzyme that breaks proteins into polypeptides

parietal cells

the cells that release gastric juices by secreting H+ and Cl- ions at high concentrations

chief cells

the cells that release pepsin in its inactive form in the stomach lumen


the inactive form of pepsin which is converted by HCl into active pepsin by clipping off a portion of it to expose the active site


a viscous and slippery material containing glycoproteins, cells, salts, and water that lines the stomach that protects against self-digestion;

small intestine

the primary station of enzymatic hydrolysis of macromolecules; 6 meters long


the first 25 centimeters of the small intestine that serves as a major crossroad in digestion; chyme from stomach mixes with digestive juices of pancreas, liver, and gallbladder; controls digestive secretions into alimentary canal


an organ that aids chemical digestion by producing an alkaline solution rich in bicarbonate and the enzymes trypsin and chymotripsyn


a mixture of substances that act as detergents that aid in the absorption of lipids; stored and concentrated in gallbladder, but made in liver


this organ breaks down toxins, balances nutrients, breaks down dysfunctional red blood cells, and makes bile


an organ that stores bile


water-soluble globules that are made by the recombination of fats into triglycerides within the epithelial cells of the small intestine, and then coated with phospholipids, cholesterol, and proteins; too large to pass through membranes of capillaries to be absorbed,


a vessel at the core of each villus that is a part of the vertebrate lymphatic system, which is a network of vessels filled with clear fluid called lymph; chylomicrons are sent here after their formation

hepatic portal vein

the convergence of veins that carry blood away from the villi and to the liver, heart, and other organs; allows the liver to regulate distribution of nutrients

large intestine

the organ at the end of the alimentary canal; includes the colon, cecum, and rectum; joins the small intestine with a T-junction sphincter


an organ in the large intestine that leads to the rectum and anus; recovers water that entered the alimentary canal through osmosis


a pouch connected to the large intestine that is important for fermenting ingested material such as cellulose


a fingerlike projection of the cecum that has a minor and dispensable role in immunity


wastes of the digestive system that become increasingly solid as they are moved along the colon by peristalsis; it takes 12-24 hours for material to travel the length of the colon


the terminal portion of the large intestine in which feces are stored until they can be eliminated; consists of two sphincters: one voluntary and one involuntary


these animals generally have pointed incisors and canines that can be used to kill prey and rip or cut away pieces of flesh; jagged molars crush and shred food


these animals usually have teeth with broad, ridged surfaces that grind tough plant material; incisors and canines are modified for biting off pieces of vegetation


these animals have unspecialized teeth--there are combinations of traits found in both carnivorous and herbivorous dentition


the consumption of more calories than the body needs for normal metabolism; can cause obesity, the excessive accumulation of fat that contributes to type 2 diabetes, some types of cancer, and cardiovascular disease

oral cavity, esophagus, pharynx

polysaccharides, sucrose, and lactose are digested here by salivary amylase (in order of system)


proteins are digested here into polypeptides by pepsin

lumen of small intestine

digested here: polysaccharides, maltose, polypeptides, amino acids, DNA, RNA, nucleotides, fat globules, fat droplets, glyercol, fatty acids, monoglycerides

epithelium of small intestine

digested here: monosaccharides, small peptides, amino acids, nucleosides, nitrogenous bases, sugars, phosphates


primary enzyme for the digestion of carbohydrates


enzyme for digestion of proteins in stomach

carboxypeptidease, chymotrypsin, trypsin

enzymes (in alphabetical order) for digestion of proteins in lumen of small intestine

nuclease, phosphatease

enzymes generally used in the digestion of nucleic acids

bile salt, lipase

enzymes generally used in the digestion of fats

interior surface

this part of the stomach is highly folded and dotted with pits leading to the tubular gastric glands

gastric gland

this part of the stomach includes different components of gastric juices, including mucus cells, chief cells, and parietal cells

mucus cells

these cells secrete a lubricating material that coats the stomach


the first chamber of ruminant digestive systems; boluses enter this area when food is ingested


the second chamber of ruminant digestive systems; mutualistic prokaryotes and protists go to work here, then secrete fatty acids; periodical regurgitation occurs in order to further break down fiber


the third chamber of ruminant digestive systems; water is removed from the cud


the fourth chamber of ruminant digestive systems; the cud, which contains microorganisms, passes through for digestion by enzymes


an appetite-regulating hormone that suppresses appetite and acts as a counter to ghrelin


an appetite-regulating hormone that triggers the sensation of hunger


an appetite-regulating hormone that is secreted after a rise in blood sugar

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