Chapter 3 -- Digestion, Absorption, and Transport
gastrin, secretin, cholecystokinin, gastric inhibitory peptide (GIP)
Enterogastrones include __________, ___________, __________________________________, and __________ __________________ ___________.
water, bile salts, bile pigments, fat, cholesterol
Bile is composed of _________, _______ ________, ______ ________________, ______, and ____________________________.
mechanical digestion
Breaking down food by chewing, grinding, squeezing, and moving it through the GI tract by peristalsis and segmentation.
chemical digestion
Breaking down food through enzymatic reactions.
epiglottis
Cartilage at the back of the tongue that closes off the trachea during swallowing.
goblet cells
Cells throughout the GI tract that secrete mucus.
lumen
Channel or inside space of a vessel such as the intestine or artery.
hydrolysis
Chemical reaction that breaks the bond between two molecules with water; a hydroxyl group is added to one molecule and a hydrogen ion is added to the other molecule.
mastication
Chewing food.
sphincters
Circular rings of muscle that open and close in response to nerve input.
proteases
Classification of enzymes that catalyze the hydrolysis of proteins.
salivary glands
Cluster of glands located underneath and behind the tongue that release saliva in response to the sight, smell, and taste of food.
intestinal permeability
Condition in which the junctions between enterocytes allow large molecules to enter the bloodstream; also called leaky gut syndrome.
3, 10
Depending on the amount and type of food eaten, the contact time in the small intestine is between ___ and ____ hours.
enteric
Digestion, absorption, and elimination are also regulated by the ____________ nervous system.
pancreas
Digestive enzymes are secreted all along the GI tract, but most are produced in the ______________.
capillaries, lacteals
Each villus contains ____________________ and lymphatic vessels called ______________ that pick up digested nutrients during absorption.
big
Endocytosis occurs when molecules are too ______ to cross through a membrane using passive or active transport.
elimination
Excretion of undigested and unabsorbed food through the feces.
intestinal gas
Fermentation is the major source of _______________________ _______.
rectum
Final 8-inch portion of the large intestine.
peristalsis
Forward, rhythmic muscular contractions that move food through the GI tract.
vitamin K, thiamin, riboflavin, biotin, vitamin B12, biotin, vitamin K
GI flora produce some vitamins, including ____________ ____, ____________, __________________, _________, and ___________ ______; only _________ and __________ ____ can be absorbed in the colon, however.
crypts
Glands at the base of the villi; they contain stem cells that manufacture young cells to replace the cells of the villi when they die.
enterogastrones
Group of GI tract hormones, produced in the stomach and small intestine, that controls gastric motility and secretions.
gastric inhibitory peptide (GIP)
Hormone produced by the small intestine that slows the release of chyme from the stomach.
peptide YY
Hormone produced in the small intestine that reduces hunger.
ghrelin
Hormone produced in the stomach that stimulates hunger.
cholecystokinin (CCK)
Hormone released by the duodenum that stimulates the gallbladder to release bile.
gastrin
Hormone released from the stomach that stimulates the release of acid.
gastric, pancreatic, peristalsis, enzyme
Hormones secreted throughout the GI tract regulate digestion by controlling the release of __________ and __________________ secretions, _____________________, and ____________ activity.
impair, activating, 1
Hydrochloric acid is unique in that it can ___________ the activity of some proteins while ____________________ others; it is essential for digestion because of its ability to lower the pH of gastric juice close to ___.
lipase
In addition to pepsinogen, the chief cells also secrete gastric _________, which begins to digest fats, although this enzyme is not particularly active in adults.
enzyme, nutrient, pH, temperature
In order for enzymes to catalyze hydrolytic reactions, three conditions must be present: the compatible ___________ and ____________ must both be present; the ______ of the environment must fall in the appropriate range; the ________________________ of the environment must fall within the appropriate range.
water, sodium
In the large intestine, ________ is absorbed via passive diffusion and __________ is absorbed via active transport.
protein
In the presence of HCl, pepsinogen is converted to its active form, pepsin, which begins the digestion of __________.
pepsinogen
Inactive protease secreted by the chief cells in the stomach; it is converted to the active enzyme pepsin in the presence of HCl.
gastric pits
Indentations or small pits in the stomach lining where the gastric glands are located; gastric glands produce gastric juices.
stomach
J-shaped muscular organ that mixes and churns food with digestive juices and acid to form chyme.
pancreas
Large gland locates behind the stomach that release digestive enzymes and bicarbonate after a meal; also secretes the hormones insulin and glucagon, which control blood glucose.
hepatic portal vein
Large vein that connects the GI tract to the liver and transports newly absorbed water-soluble nutrients.
probiotics
Live microorganisms that, when consumed in adequate amounts, confer a health benefit on the host.
small intestine
Long coiled chamber that is the major site of food digestion and nutrient absorption.
large intestine
Lowest part of the GI tract, where water and electrolytes are absorbed and waste is eliminated.
eating, fiber
Mass movement often occurs shortly after _________ and is stronger when the diet contains more _________.
mass movement
Mass peristalsis; strong, slow peristaltic movements, occurring only three or four times a day within the colon, that force waste toward the rectum.
pH
Measure of the acidity or alkalinity of a solution.
longitudinal, circular, diagonal
Mechanical digestion in the stomach occurs as the _________________________, _______________, and _______________ muscles that surround the organ forcefully push, churn, and mix the contents of the stomach with the gastric juices.
GI flora
Microorganisms that live in the GI tract of humans and animals.
brush border
Microvilli are referred to collectively as the ________ __________, which trap nutrients and absorb them into the enterocyte interior.
active transport
Movement of substances across a cell membrane against their concentration gradient with the help of a carrier protein and energy expenditure.
passive diffusion
Movement of substances across a cell membrane along their concentration gradient.
facilitated diffusion
Movement of substances across a cell membrane with the help of a carrier protein along their concentration gradient.
segmentation
Muscular contractions of the small intestine that move food back and forth, breaking the mixture into smaller and smaller pieces and combining it with digestive juices.
upper esophageal sphincter
Muscular ring located at the top of the esophagus.
lower esophageal sphincter (LES)
Muscular ring located between the base of the esophagus and the stomach.
bicarbonate
Negatively charged alkali ion produced from bicarbonate salts; during digestion, the ions released from the pancreas neutralize HCl in the duodenum.
prebiotics
Nondigestible starch found in plant foods that promotes the growth and health of your GI flora.
passive diffusion, facilitated diffusion, active transport, endocytosis
Nutrients move across cell membranes in the small intestine via one of four mechanisms: ____________ _________________, _______________________ _________________, __________ ________________, or _____________________________.
cardiovascular, lymphatic
Once the nutrients have been absorbed through the lining of the small intestine, they are carried either through the ___________________________ or _________________ system to other parts of the body.
denatured
Once the protein is ____________________, proteases hydrolyze the bonds, breaking the proteins into shorter chains.
carbohydrates, fats, proteins, alcohol
One of the most important roles of enzymes is to accelerate hydrolysis reactions, in which water breaks the bonds of digestible ____________________________, _______, ____________, and _____________.
anus
Opening of the rectum, or end of the GI tract.
water, surface
Pancreatic lipase is ________-soluble and only works on the surface of the fat globule.
gallbladder
Pear-shaped organ that stores and concentrates bile produced by the liver and secretes it through the common bile duct into the small intestine.
cecum
Pouch at the beginning of the large intestine that receives waste from the small intestine.
absorption
Process of moving nutrients from the GI tract into the circulatory system.
enterohepatic circulation
Process of recycling bile from the large intestine back to the liver to be reused during fat digestion.
digestion
Process that breaks down food into individual molecules small enough to be absorbed through the intestinal wall.
propulsion
Process that moves food along the GI tract during digestion.
saliva
Secretion from the salivary glands that softens and lubricates food and begins the chemical breakdown of starch.
bile
Secretion produced by the liver, stored in the gallbladder, and released into the duodenum to emulsify dietary fat.
mucus
Secretion produced throughout the GI tract that moistens and lubricates food and protects membranes.
enteric nervous system
Section of the peripheral nervous system that directly controls the gastrointestinal system.
shifted
Segmentation differs from peristalsis in that food is ___________ (rather than squeezed) back and forth along the intestinal walls.
chyme
Semiliquid, partially digested food mass that leaves the stomach and enters the small intestine.
villi
Small, fingerlike projections that line the lumen of the small intestine.
bolus
Soft mass of chewed food.
fiber, short-chain fatty acids
Some of the colon's bacteria break down undigested ________ and produce various ________-________ ________ ________.
chief cells
Specialized cells in the stomach and secrete pepsinogen, an inactive form of the protein-digesting enzyme pepsin.
parietal cells
Specialized cells in the stomach that secrete the gastric juices hydrochloric acid and intrinsic factor.
ileocecal valve
Sphincter that separates the small intestine from the large intestine.
hydrochloric acid (HCl)
Strong acid produced in the stomach that aids in digestion.
substrate
Substance or compound that is altered by an enzyme.
enzymes
Substances, mostly proteins, that increase the rate of chemical reactions; also called biological catalysts.
lymphatic vein
System of interconnected vessels that contains lymph fluid in which fat-soluble nutrients are carried; also includes bone marrow, lymph nodes, and other tissues and organs that produce and store defensive cells.
diameter
The "small" in "small intestine" refers to its ________________ (about 1 inch), not its extended length.
20, 24
The GI tract is a muscular tube that is approximately _____-_____ feet long in an adult.
liver
The _______ plays a key role in nutrition -- it is the first organ to receive water-soluble nutrients absorbed through the intestines via the hepatic portal vein.
brush border
The ________ __________ of the small intestine releases the last of the digestive enzymes.
blood
The ________ is the body's primary transport system, shuttling oxygen, nutrients, hormones, and waste products throughout the body.
salivary glands, liver, gallbladder, pancreas
The ____________ ________, _______, _______________________, and ____________ are considered accessory organs because food does not pass through them; they contribute digestive secretions such as saliva, bile, and enzymes that help with breakdown and transport of nutrients.
endocrine, nervous
The ______________ and ___________ systems work together to control and coordinate digestion, absorption, and elimination of waste products.
chemically, mechanically
The body digests food ____________________ by the actions of digestion secretions and _______________________ by the actions of the teeth and the powerful muscles of the GI tract.
urea, urine
The breakdown of proteins releases a nitrogenous waste called ________; the kidneys filter it from the blood, allowing it to be excreted in __________.
iron, bilirubin
The brown color of stool is due to unabsorbed ______ mixing with a yellowish-orange substance called ________________.
lipid
The cell membrane of enterocytes has a ________ layer that is impermeable to most nutrients.
ascending, transverse, descending, sigmoid
The colon is the largest portion of the large intestine, and it is further subdivided into the _______________, ___________________, _________________, and ____________ regions.
mouth, stomach
The esophagus has only one function -- to transport food and fluids from the _________ to the ______________.
voluntary, age, diet, prescription medicines, health, abdominal muscle tone
The final stage of defecation is under _______________ control and influenced by _____, ______, _____________________ _______________, _________, and ___________________ __________ _______.
mouth, pharynx, esophagus, stomach, small intestine, large intestine
The gastrointestinal tract's sic organs are the _________, _____________, _________________________, ___________, ________ __________________, and _________ ___________________.
atria, ventricles
The heart is divided into four chambers: two upper ________ and two lower ___________________.
ghrelin, peptide YY
The hormones _____________ and ___________ _____ communicate feelings of hunger or fullness to the brain.
12, 70
The intestinal matter passes through the colon within _____-_____ hours, depending on a person's age, health, diet, and fiber intake.
cecum, colon, rectum
The large intestine has three segments: the _________, ________, and ____________.
5, 2.5
The large intestine is about ___ feet long -- much shorter than the small intestine -- but its lumen is larger, about ______ inches in diameter.
3
The liver is the largest organ in the body, weighing in at about ___ pounds.
endocrine, exocrine
The pancreas is considered both __________________ and _________________.
esophagus, trachea
The pharynx is the gateway to the __________________, as well as to the ____________ (or windpipe, the tube that connects to the lungs).
salivary amylase
The primary enzyme in saliva is ____________ _____________, which begins to break down carbohydrates.
1 quart
The salivary glands produce about ___ _______ of saliva per day.
saliva
The secretion of ___________ and other digestive juices starts a cascade of events that prepares the body for digestion.
duodenum, jejunum, ileum
The small intestine consists of three segments -- the ______________________, _____________________, and _________ -- and extends from the pyloric sphincter to the ileocecal valve at the beginning of the large intestine.
parietal, chief
The specialized _______________ and ________ cells produce the gastric juices secreted by the stomach.
four, goblet cells, gastric pits, ducts
The stomach lining includes _______ layers; the innermost layer contains _________ _______ and __________ ______ or _________, which contain gastric glands that secrete a variety of critical digestive juices.
digestion, homeostasis
The synchronized effort by the GI tract hormones ensures the efficiency of _______________ and maintains ___________________________ in the body.
peristalsis, segmentation
The two primary types of contractions are called ______________________ and ______________________________.
stomach
The waves of contractions in the _____________ are slower than in other GI organs, as peristalsis mixes and churns its contents with gastric juices until the food is liquefied.
microvilli
Tiny projections on the villi in the small intestine.
emulsify
To break large fat globules into smaller droplets.
ferment
To metabolize sugar into carbon dioxide and other gases.
esophagus
Tube that connects the mouth to the stomach.
gastrointestinal (GI) tract
Tubular organ system including the mouth, pharynx, esophagus, stomach, and small and large intestines, by means of which food is digested, nutrients absorbed, and wastes expelled.
endocytosis
Type of active transport in which the cell membrane forms an indentation, engulfs the substance to be absorbed, and releases it into the interior of the cell.
92, 97
Under normal conditions, you digest and absorb _____-_____ percent of nutrients in food.
hepatic vein
Vein that carries the blood received from the hepatic portal vein away from the liver.
surface area
Villi increase the __________ _______ to maximize absorption and help mix the partially digested chyme with intestinal secretions.
stool
Waste produced in the large intestine; also called feces.
enterocytes, capillaries, hepatic portal vein
Water-soluble nutrients, including carbohydrates, amino acids, and water-soluble vitamins, are absorbed into the ________________________, cross into the _____________________, and travel via the _____________ _________ _______ to the liver.
greater
When the concentration of a nutrient is _______________ in the GI lumen that within the enterocyte, the nutrient flows passively across the cell membrane.
malabsorption
Without the proper nutrients, the villi deteriorate and flatten, resulting in _______________________________.
water, lipids, minerals, vitamin C
________, small _________, a few _______________, and ________________ ____ are examples of nutrients absorbed via passive diffusion.
glucose, amino acids
___________ and ________ _______ are examples of nutrients absorbed by active transport.
fructose
____________ is an example of a nutrient that is absorbed with the help of a carrier protein.
endocrine glands
_________________ _________, which are found in the stomach, small intestine, and pancreas, are specialized cells that secrete hormones into the bloodstream in response to a stimulus.
bicarbonate
__________________________ ions alter the pH of food at various points along the GI tract.
colon
Another name for the large intestine.
1, 5, 30
Approximately ___-___ milliliters (1 teaspoon) of chyme is released into the small intestine every ______ seconds.
pharynx
Area of the GI tract between the mouth and the esophagus, also called the throat.
secretin
A hormone secreted from the duodenum that stimulates the stomach to release pepsin, the liver to make bile, and the pancreas to release digestive juices.
1 liter
About ___ _______ of fluid material -- consisted of water, undigested or unabsorbed food particles, indigestible residue, and electrolytes -- passes into the colon each day.
99
About ______ percent water, saliva moistens and binds food to lubricate it for comfortable swallowing and traveling down the esophagus.
enterocytes
Absorptive epithelial cells that line the lumen of the small intestine.
liver
Accessory organ of digestion located in the upper abdomen and responsible for the synthesis of bile, the processing of nutrients, the metabolism of alcohol, and other functions.
pepsin
Active protease that begins the digestion of proteins in the stomach.
small intestine
Although most absorption occurs in the stomach and large intestine, the ________ ________________ absorbs most nutrients via the enterocytes lining its walls.
hydrogen, sulfide, fatty acids
Amino acids that reach the colon are converted to _______________, ____________, some ________ ________, and other chemical compounds.
