Digestive System- Physiology Flashcards
_____means simply ‘eating or drinking,’ while _____ refers to the process of eliminating
_____ (material which is left over after all usable substances have been extracted).
Ingestion; defecation; feces
_____ is the breakdown of ingested foods into simple organic molecules.
Digestion
_____ refers to the mixing of food and digestive juices into a soft pulp.
Mechanical digestion
________ means ‘chewing.’ It is one means by which _____ occurs.
Mastication; mechanical
digestion
Smooth muscles in the gastrointestinal tract are responsible for the _____ of food from
mouth to anus via processes called _____ (swallowing) and _____.
propulsion; deglutition;
peristalsis
_________ consists of a series of progressive, alternating contractions of smooth muscle rings
which encircle the intestine. The result is propulsion of a portion of the partially digested
food, called a(n) _____, through the intestine.
Peristalsis; bolus
Mechanical digestion is continued throughout the gastrointestinal tract via a process
called _____, in which the bolus is rhythmically divided into ever-smaller portions by
bidirectional, peristalsis-like contractions of smooth muscle.
segmentation
_____ of enzymes and corrosive liquids, as well as mucus to lubricate and protect the
system itself is the function of specialized cells within the gastrointestinal tract and
accessory organs.
Secretion
_____ of nutrients is possible because cells of the gastrointestinal tract actively
transcytose them into the blood or lymph.
Absorption
The epithelial cells of the GI tract are joined by _____ so that nutrient molecules cannot
enter the body by passing between cells, but must instead pass through them.
tight junctions
During _____, complex molecules are separated and hydrolyzed by enzymes, emulsifiers
and corrosive chemicals.
chemical digestion
Digestive activity is subject to _____ and _____ controls. These, in turn, are triggered by
_____ or _____ stimuli.
nervous; hormonal; chemical;
mechanical
Neural networks found in the entrails, as a group, are the _____ or _____.
enteric plexus; enteric nervous
system (ENS)
Neural control is primarily _____, via the _____, with only minor modulation from the CNS.
local; enteric plexus
Neural regulation of the digestive system is complex, and involves over 30 _____, each
mediating a slightly different response from the cells which receive them as signals.
neurotransmitters
Many of the hormones that control digestion are produced by _____. This allows each
region of the digestive system to interact with _____, even those some distance away.
cells of the digestive system; all
of the others
Beginning with the esophagus, the GI tract has four major walls or layers, called _____.
From the lumen outward, the first three are the _____, _____, and the _____.
tunics; mucosa; submucosa;
muscularis
The outermost tunic of the GI tract is called the _____ when it is adjacent to the peritoneal
cavity, or the ____ in regions where it is physically continuous with surrounding tissue.
visceral serosa; adventitia
The mucosa of the intestinal tract consists of three layers: from the lumen outward, they
are the _____, _____ and _____.
mucous epithelium; lamina
propria; muscularis mucosae
In many regions of the GI tract, the mucous epithelium invaginates, penetrating the _____
to form _____.
lamina propria; glands
Blood vessels and lymphatic vessels in the _____ of the GI tract’s
mucosa provide nutrients and oxygen, and remove wastes, from the mucous epithelium.
lamina propria
The mucosa-associated lymphoid tissue (MALT) is found in the _____ . Since it is in the gut, MALT in this region is often called “_____”
instead of MALT.
lamina propria; Gut-Associated Lymphoid Tissue (GALT)
The purpose of the MALT in the GI tract is to protect it from _____.
bacteria which contaminate
food or drink
Smooth muscles in the _____ create
transient wrinkles which decrease adherence of substances to the intestinal surface and
increase local mixing.
muscularis mucosae
Most blood vessels, lymphatic vessels, and nerve fibers of the GI tract are found in the
_____ .
submucosa
The inner layer of the muscularis consists of smooth muscle fibers which _____ the
lumen, while in the outer layer the fibers are arranged _____.
encircle; longitudinally
In the stomach and intestines, peristalsis and segmentation are accomplished by
alternating contractions of the inner and outer layers of the _____ .
muscularis
_____ cells in the muscularis control the rate of peristalsis and segmentation.
Pacemaker
In certain regions of the GI tract, the muscles of the muscularis act as _____, and are
capable of closing to prevent movement of food or liquid through the tract.
sphincters
Neurons of the enteric plexus in the submucosa are called the _____ plexus; those in the
muscularis lie _____ and are called the _____ plexus.
submucosal; between the
muscle layers; myenteric
The mouth is kept moist between meals primarily by the _____, which are scattered
throughout the oral mucosa.
intrinsic salivary glands OR
buccal glands
When we ingest food (or even think about it!) signals from the _____ branch of the
autonomic nervous system cause the _____ salivary glands to produce saliva.
parasympathetic; extrinsic
Damage to _____ can prevent signals from the CNS from reaching the salivary glands
and increasing salivation.
cranial nerves VII or IX
_____ and _____ respond to taste and pressure, and lead to an increase in salivation that
is mediated by the autonomic nervous system.
Chemoreceptors;
pressoreceptors
The _____ branch of the autonomic nervous system inhibits production of serous (watery)
saliva, but not of mucin-rich saliva, so that stress leaves the mouth feeling dry and sticky.
sympathetic
Saliva contains amylase to begin _____, chemicals including lysozyme and immunoglobin
A to _____, and mucin to _____.
starch digestion; inhibit
bacterial growth; lubricate the
mouth
The two major processes which moisten and soften food in the oral cavity are _____ and
_____.
mastication; salivation
_____ means ‘swallowing.’
Deglutition
The voluntary portion of deglutition is the _____ phase, which occurs in the mouth. In this
phase, the _____ is used to push the food into the _____.
buccal; tongue; oropharynx
The second phase of deglutition, the _____ phase, is involuntary.
pharyngeal
During the pharyngeal phase of deglutition, the _____ prevents food from returning to the
mouth.
tongue
During the pharyngeal phase of deglutition, the _____ and _____ prevent food from
entering the nasopharynx.
soft palate; uvula
During the pharyngeal phase of deglutition, the _____ prevents food from entering the
larynx.
epiglottis
Cranial nerves V, IX, X and XI are all involved in the _____. Damage to any of them can
make it difficult to swallow.
pharyngeal phase of deglutition
Three rings of muscles in the pharynx called the _____ contract one after the other to
propel food into the esophagus.
pharyngeal constrictor muscles
As food reaches the bottom of the pharynx, the _____ relaxes.
upper esophageal sphincter
During the third phase of deglutition, the _____ phase, food is propelled toward the
stomach by _____ .
esophageal; peristalsis
Both the pharyngeal and esophageal stages of deglutition are triggered by _____ and
lead to both local and CNS signals.
contact with solids or liquids
OR tactile receptors
Since the task of the esophagus is simply to transport food, its surface is optimized for
resisting friction as food passes by; it consists of _____.
stratified squamous epithelium
The surface of the esophagus includes _____ glands, which lubricate the surface.
mucous or esophageal
Mixing semi-solid food with liquid to form completely liquid ‘_____’ is one of the major
functions of the _____.
chyme; stomach
Liquid is secreted into the stomach by _____; their entrances, the _____, appear as pores
on the stomach’s interior surface.
gastric glands; gastric pits
Unlike the esophagus, whose surface is specialized to resist friction, the surface of the
stomach is specialized for _____, and consists of _____.
secretion; simple columnar
epithelium
Gastric secretions and food are mixed in the stomach by muscular contractions called
_____. These contractions occur primarily in the _____, the widest part of the pyloric region.
mixing waves; antrum
Unlike the muscularis in other regions of the GI tract, that of the stomach has _____.
three layers
The stomach adjusts to the ingestion of food or drink by _____ and _____ to
accommodate to the new demand for volume.
stretching; relaxing
While most digestion occurs in the _____, digestion of _____ begins in the stomach.
small intestine; protein
_____ cells in the gastric glands secrete a(n) _____ (an inactive proenzyme) called
pepsinogen.
Chief; zymogen
Pepsinogen, when it is placed in a(n) _____ environment, is activated to form the enzyme
_____. This enzyme hydrolyzes _____.
acidic; pepsin; proteins
_____ cells in the gastric glands secrete hydrochloric acid, which _____ the pH in the
stomach’s lumen.
Parietal or Oxyntic; lowers
Hydrochloric acid _____ proteins and nucleic acids in the stomach and converts _____ to
its active form, _____.
denatures; pepsinogen; pepsin
Most bacteria are unable to survive in the stomach because of the _____.
low pH OR acidity
The parietal cells use _____ acid as the source for positive hydrogen ions. This produces
the negative _____ ion, which they don’t need or use.
carbonic; bicarbonate
To get rid of bicarbonate ions, parietal cells secrete it into the blood, exchanging it for the
readily available _____.
chloride ions
The stomach’s secretions must be electrically neutral, and so the secretion of positive
hydrogen ions into the lumen is accompanied by the secretion of negative _____.
chloride ions
In water, hydrochloric acid is present as two ions: _____ and _____.
hydrogen ions; chloride ions
The two major cell types in the stomach produce _____, which is necessary so that the
stomach does not _____.
mucus; digest itself
The mucus that coats the stomach is thick, heavy, and (just as importantly) _____. This is
because the mucus producing cells mix their product with _____.
neutral to alkaline; bicarbonate
Very few substances are absorbed in the stomach - most cannot penetrate the _____
layer. Those that can include water, alcohol, and a few drugs.
mucus
Vitamin B12 would be destroyed by the stomach’s acid if not for _____, a protective
glycoprotein secreted by _____. (B12 is critical for DNA replication: the first symptom of
deficiency is _____ due to poor cell division.)
intrinsic factor; parietal cells;
pernicious anemia
_____ is needed not only to protect vitamin B12 from destruction in the stomach, but also
to allow it to be absorbed in the intestine. Thus, production of this glycoprotein by the
stomach is absolutely critical to survival.
Intrinsic factor
Three chemicals together signal the parietal cells to secrete HCl: _____, _____ and _____.
gastrin; histamine; acetylcholine
Gastrin is released by enteroendocrine cells in the stomach mucosa in response to _____
or to signals from the _____.
an increase in stomach
content; CNS
Gastrin has several effects, one of which is to promote _____ in the cells of the stomach:
thus, in the long term, a large appetite leads to a large _____. (Do not confuse this with a
large store of fat in the abdomen, which may also occur!)
cell division; stomach
_____ is released by ‘ECL cells’ and mast cells in the stomach’s lamina propria in
response to _____.
Histamine; gastrin
Histamine binds to H2 receptors on _____ cells, and is the most potent acid-producing
signal molecule. (Blocking these receptors with drugs such as Tagamet virtually abolishes
acid production.)
parietal OR oxyntic
Regulation of the stomach’s secretions and motility occurs in three phases: the _____
phase, _____ phase, and _____ phase.
cephalic; gastric; intestinal OR
gastrointestinal
The _____ phase of gastric regulation occurs before food (or drink) enters the stomach,
and depends on taste, smell, and anticipation.
cephalic
During the _____ phase of gastric regulation, signals from the medulla oblongata are
conveyed by the _____ nerve to the enteric ganglia.
cephalic; vagus
During the gastric phase of gastric regulation, the major signals are _____ and the
presence of _____ in the stomach. In addition, over-secretion is prevented by _____
feedback. If pH falls too far, acid production stops.
distention; peptides OR amino
acids; negative
Two chemicals commonly consumed by students (and teachers, to be fair) also trigger the
gastric phase or gastric reflex: _____ and _____.
caffeine; alcohol
In the _____ phase, sensations in the stomach are sent to the CNS via the vagus nerve:
return signals, via the same nerve, increase _____ and _____.
gastric; gastric secretion;
motility
In the _____ phase, sensations in the stomach activate _____ cells: these release gastrin
and other hormones into the blood, which eventually trigger an increase in _____.
gastric; enteroendocrine;
gastric secretion and motility
Mixing waves occur in the stomach three times per minute: less frequently, stronger
_____ waves overwhelm the partially closed _____ sphincter and send a small amount of
_____ into the duodenum.
peristaltic; pyloric; liquid
In the gastrointestinal or intestinal phase of gastric regulation, the _____ inhibits the
activities of the stomach in order to give itself time to cope with _____, _____ or _____.
duodenum; decreases in pH;
high levels of fat; over-filling
_____ is secreted by the duodenum in response to acid. It travels through the blood to the
_____ and _____ cells of the stomach, which it inhibits.
Secretin; parietal OR oxyntic;
chief
_____ and _____ are secreted by the duodenum in response to the presence of fat:
among other activities, these hormones inhibit the activity of the _____.
Gastric inhibitory peptide;
cholecystokinin; stomach
The duodenum signals the medulla oblongata when conditions are such that a further
influx from the stomach would overwhelm it, and the medulla then signals the stomach to
decrease gastric activity: this is the _____.
enterogastric reflex
A major change in the epithelia occurs between the stomach and duodenum. While the
stomach is designed to protect itself and avoid self-digestion, the duodenum is specialized
for _____ and _____, and its epithelia includes many _____.
digestion; absorption; villi
The _____ cells of the duodenum are covered with _____, which increase their surface
area and allow them to absorb more nutrients than would otherwise be possible.
absorptive; microvilli
A(n) _____ and a(n) _____ are located in the core of each villus in the small intestine.
capillary bed; lacteal
Microvilli have enzymes on their surfaces which _____.
digest carbohydrates and
proteins
In addition to many absorptive cells, villi also contain _____ cells which secrete mucus,
and _____ cells which secrete hormones. The number of these cells _____ as one moves
from the jejunum to the ileum to the large intestine.
goblet; enteroendocrine;
increases
In addition to other cell types, villi also contain immune cells called _____.
intraepithelial lymphocytes
In between the villi of the small intestine the mucosa forms _____ which secrete a watery
mucus called intestinal juice.
intestinal crypts OR crypts of
Lieberkuhn
The villus epithelium is replaced every _____.
3 to 6 days
As one moves from the duodenum toward the ileum, patches of lymphoid tissue called
_____ become more abundant.
Peyer’s patches
A highly alkaline mucus which helps to neutralize the acidic chyme exiting the stomach is
produced by _____ in the _____.
duodenal glands OR Brunner’s
glands; duodenum
Two accessory digestive organs, the _____ and _____, deliver their products directly to
the duodenum.
liver; pancreas
Two openings are found in the duodenum through which digestive juices enter: the
opening of the _____ and the large, nipple-like opening formed by the union of several
ducts, the _____.
accessory (pancreatic) duct;
hepatopancreatic ampulla
Entry of bile and pancreatic juice through the hepatopancreatic ampulla is controlled by
the _____. The bulge formed by this, and the hepatopancreatic ampulla, is called the
_____.
hepatopancreatic sphincter OR
sphincter of Oddi; major
duodenal papilla
The major histological differences seen as one progresses through the small intestine is
that the _____ decrease in number and density while the _____ increase.
villi; Peyer’s patches
Most of the small intestine is covered by the visceral peritoneum; the duodenum, however,
is _____ and so its outer layer is _____.
retroperitoneal; adventitia
_____ or _____ leads to the production of extra intestinal juice by the intestinal crypts.
Distension; exposure to
hypertonic or acidic chyme
The liver is an organ from which _____ flow, and to which many _____ flow.
digestive juices; absorbed
nutrients
To suspend tiny droplets of one substance in another (for example, tiny droplets of oil in
water) is to _____ it.
emulsify
_____ is the digestive juice that is produced by the liver, and which functions to emulsify
_____.
Bile; fats OR lipids
The liver is composed of microscopic structural units called _____.
liver lobules
Each liver lobule has roughly _____ sides consisting of adjacent plates, or layers, of liver
cells called _____.
six; hepatocytes
At each corner in a liver lobule is a(n) _____, so named because it contains three
structures: a(n) _____, a(n) _____ and a(n) _____.
portal triad; hepatic artery;
portal vein; bile duct
Between each layer of hepatocytes in a liver lobule lies a space called a(n) _____, which
is a large, leaky capillary.
sinusoid
Within the liver sinusoids, blood from the _____ and _____ mix before they reach the
central vein.
hepatic artery; portal vein
Blood in the _____ of the liver lobules eventually enters the hepatic veins, then leaves the
liver to flow to the inferior vena cava.
central veins
_____ are included in the sinusoid walls; their job is to eat debris,
bacteria and worn out blood cells.
Hepatic macrophages OR
Kupffer cells
Nutrients and waste products are altered or removed from the blood in _____ in the liver.
hepatocytes
Blood-borne chemicals are modified for disposal by _____ in the liver; the modified
chemicals are then either _____ or _____.
hepatocytes; released into the
blood for disposal by the
kidneys; secreted in bile
_____ in the liver are the cells in which _____ is stored, for use as an energy source
during brief fasts.
Hepatocytes; glycogen
In the absence of insulin, _____ will use lipids to produce _____, an alternate fuel source
usable by many tissues in the body, including the brain.
hepatocytes; ketone bodies
During periods of extreme hypernutrition (over-eating), _____ in the liver will store lipids.
This is also common in alcoholism, since lipid metabolism is inhibited during the
metabolism of alcohol.
hepatocytes
Once bile is produced by _____, it leaves the liver lobules via the _____.
hepatocytes; bile canaliculi
In part because of its role in detoxifying dangerous chemicals and being the first organ
which blood leaving the intestines encounters, the _____ is subject to disease. Two of the
most common are _____ and _____.
liver; hepatitis; cirrhosis
_____ is any disease characterized by inflammation of the liver, and is often caused by
viral infections.
Hepatitis
_____ is a disease in which normal liver tissue is replaced by connective tissue.
Cirrhosis
Detoxified substances and waste products which are removed from the blood by the liver
are disposed of in the _____.
bile
Bile is a mixture of waste products and ‘_____,’ which are required for fat digestion. They
are _____ in the ileum so that they can be recycled.
bile salts; reabsorbed
_____ are made from cholesterol and use more cholesterol than any other single bodily
function.
Bile salts
Fat is emulsified in order to increase the_____ of the droplets.
surface area
The major function of the gallbladder is to _____ and _____ bile until it is needed.
store; concentrate
Bile backs up into the gallbladder through the _____ due to the fact that the _____ is
closed unless digestion is in progress.
cystic duct; hepatopancreatic
sphincter
Gallbladder contraction and opening of the hepatopancreatic sphincter is controlled by
_____, a hormone with several functions.
cholecystokinin (CCK)
Cholecystokinin (CCK) is released to the blood by the duodenum in response to the entry
of _____.
fat-containing chyme
All of the macromolecules depend on _____ for the production of enzymes which lead to
their digestion.
the pancreas
Microscopic examination of the pancreas reveals the presence of many _____, which are
clusters of secretory cells and their associated ducts.
acini
One of the major functions of the pancreas is to secrete bicarbonate, which is used to
_____ entering the _____.
neutralize acidic chyme;
duodenum
Many enzymes produced by the pancreas are released as _____.
zymogens OR proenzymes
Trypsin is one of the enzymes released by the pancreas. Trypsin _____ many of the other
enzymes. (It is released as a zymogen called trypsinogen.)
activates
Trypsinogen is converted to trypsin by an enzyme found on the _____. Such enzymes are
called _____ enzymes because of the appearance of the microvilli when light microscopy
is used.
microvilli; brush border
Several pancreatic enzymes, including amylase and lipase, depend for their activity on
substances found in the _____.
chyme
Two major hormonal controls of pancreatic activity are _____ and _____.
cholecystokinin (CCK); secretin
Secretin is released by duodenal cells in response to _____.
acid OR low pH
Secretin prompts the pancreas to release _____-rich pancreatic juice.
bicarbonate
Cholecystokinin is released by duodenal cells in response to _____ and _____.
proteins; fats
Cholecystokinin prompts the pancreas to release _____-rich pancreatic juice.
enzyme
The CNS can also activate pancreatic secretions via the _____ nerve: this occurs
primarily during the _____ and _____ phases of gastric regulation.
vagus; cephalic; gastric
Premature activation of pepsinogen, trypsinogen, or any of the digestive enzymes would
result in _____.
digestion of the cells that
produce them
Digestive enzymes are produced primarily by the _____, not by the intestines.
pancreas
Within the small intestine, _____ waves are rare while _____ waves are common. As a
result, food is slow to pass through the small intestine.
peristaltic; mixing
The ileocecal sphincter is normally _____. Two factors can change that: the _____ reflex
and the hormone _____.
closed; gastroileal; gastrin
The gastroileal reflex is a reflex mediated by the CNS which is caused by activity in the
stomach and leads to _____.
increased activity in the ileum
Gastrin released by the stomach signals the _____ to relax briefly, thus allowing a bolus
of chyme to enter the large intestine.
ileocecal sphincter
One of the major functions of the ileocecal sphincter is to prevent _____.
backflow from the large
intestine to the small
One of the main functions of the large intestine is to absorb _____.
water
In order to reduce friction as the rapidly dehydrating feces pass through the large
intestine, the surface of the colon contains many deep microscopic indentations called
_____, which contain a large number of mucus producing _____.
crypts OR crypts of Lieberkuhn
OR intestinal glands; goblet
cells
The surface epithelium of the anal canal is _____ .
stratified squamous epithelium
Bacteria which survive the digestion process multiply in the _____ and _____. Bacteria
account for over one quarter of the dry weight of the feces.
ileum and large intestine
Most bacteria in a healthy person’s intestines are _____; they prevent the growth of _____
and produce several vitamins, including vitamin _____, which is necessary for normal
blood clotting.
beneficial; pathogenic bacteria;
K
The large intestine has two major patterns of movement: _____, which are a form of
segmentation, and _____, which are powerful waves which send feces toward the rectum
at a rapid pace.
haustral contractions; mass
movements
One stimulus for mass movements of the colon is known as the _____ reflex, and is
triggered by gastric filling.
gastrocolic
_____ in the diet increases fecal bulk and prevents damage to the walls of the colon
caused by small, hard feces formed by over-absorption of water.
Indigestible carbohydrates
fiber
Overly rapid transit of feces through the large intestine does not allow time for water
resorption; the result is _____.
diarrhea
Most intestinal gas (_____) is produced as a result of _____ of undigested
macromolecules by _____ in the large intestine. (The amount produced depends on their
identity and nature.)
flatus; fermentation; bacteria
Digestion of macromolecules involves their _____ into smaller molecules.
hydrolysis
Carbohydrate digestion begins in the _____ with the enzyme _____.
mouth; amylase
Carbohydrate digestion slows in the _____, then is accelerated again in the _____, where
carbohydrates are exposed to _____.
stomach; duodenum;
pancreatic amylase
Once carbohydrates have been broken down into disaccharides, the final hydrolysis to
yield monomers is catalyzed by enzymes found _____.
on the microvilli OR on the
brush border
Absorption of monosaccharides occurs in _____, but primarily in the _____ and _____.
the entire small intestine;
duodenum; jejunum
Once absorbed, monosaccharides are transported in the _____ to the _____.
blood; liver
Digestible carbohydrates in the human diet consist of _____, some _____ and two
polysaccharides: _____ and _____.
monosaccharides;
disaccharides; glycogen; starch
We lack enzymes to digest some carbohydrates (for example, cellulose) and so if eaten,
these reach the _____ undigested. They are referred to as _____.
large intestine; fiber
The first enzyme to hydrolyze proteins into smaller parts is _____, in the _____. This
enzyme is inactivated when it reaches the _____.
pepsin; stomach; duodenum
Partially digested proteins are exposed to several free-floating proteases in the _____;
these are produced by the _____.
duodenum; pancreas
Polypeptides are hydrolyzed to single amino acids by _____, or in the case of some
dipeptides or tripeptides, by _____ of the intestinal epithelial cells.
brush border enzymes;
intracellular enzymes
Amino acids are absorbed by the _____ in the cells of the _____, then transported in the
_____ to the _____.
microvilli; small intestine; blood;
liver
Dietary fat is usually in the form of _____.
triglycerides
For the most part, digestion of fat begins in the _____, with their _____ by bile. (A very
small amount of fat digestion occurs prior to this point.)
duodenum; emulsification
Fat-digesting enzymes called _____ are released by the _____.
lipases; pancreas
Lipases in the small intestine hydrolyze triglycerides to form _____ and _____. These
combine with a component of bile salts to form microscopic _____ in a process similar to
emulsification of the original fats.
monoglycerides; fatty acids;
micelles
Micelles containing monoglycerides, fatty acids, and cholesterol (another lipid) are
absorbed by the epithelial cells of the _____.
small intestine
In the epithelial cells of the small intestine, monoglycerides and fatty acids are used to remake
the triglycerides. These, and cholesterol, are coated with _____ to form structures
called _____.
protein; chylomicrons
Chylomicrons are exported into the _____ of the lamina propria where they enter _____,
which deliver them to the blood vessels of the neck in the lymph.
interstitial fluid; lacteals
Digestion of nucleic acids begins in the _____, where they encounter _____ secreted by
the _____.
duodenum; nucleases;
pancreas
Each nucleotide released from nucleic acids is broken down to a(n) \_\_\_\_\_, a(n) \_\_\_\_\_ and a(n) \_\_\_\_\_ by \_\_\_\_\_.
sugar; base; phosphate ion;
brush border enzymes
Many vitamins, minerals, and drugs are not _____.
chemically digested
Vitamins, minerals, and drugs which are soluble in water enter through the intestinal
epithelial cells and travel to the _____.
liver
Vitamins and drugs which are soluble in fat enter through the intestinal epithelial cells
along with the fat and travel to the _____ via the _____.
blood vessels of the neck;
lymphatic system
Nine liters (over two gallons) of water enter the intestines each day from the blood and by ingestion. Active transport of nutrients, ions, minerals, etc., into intestinal cells lowers the \_\_\_\_\_, and so water enters the cells as well.
relative tonicity of the chyme
