•Digestion is the mechanical and chemical breakdown of food from mouthfuls
to molecules small enough to:
(1) Be transportable, and
(2) Fit into cells.
•Mechanical Digestion: breaks big chunks of food up into little chunks - mouth and stomach.
•Chemical Digestion: breaks little chunks of food up into molecules - stomach and small
•Alternaterms for the Digestive System; Alimentary Canal, GI (gastrointestinal) tract, Food Tube
•The digestive system includes organs through which food passes (mouth, esophagus,
stomach, small intestine, large intestine, anal canal) AND accessory organs – organs
that food doesn’t pass through - (salivary glands, liver, gall bladder, and pancreas.)
•From beginning to end, the digestive system
is between 20 and 30 feet long.
•The wall (lining) of the digestive system is
continuous and unbroken from
beginning to end and contains 4 layers:
•These four layers are:
(1) The mucosa (mucous membrane). Formed of
surface epithelium, goblet cells, connective tissue
(lamina propria), and a small amount of smooth
muscle. Sometimes folded into villi and microvilli.
Might also secrete digestive enzymes. Functions:
(2) The submucosa. Areolar (loose) connective
tissue, blood vessels, glands lymphatic vessels, and
nerves. It's principle role is the delivery
of blood to carry away nutrients.
(3) Muscularis. Responsible for the movement of
food through the tube. Consists of (usually) two layers
of smooth muscle. Two layers of muscle fibers
through the length of the canal –circular fibers and
(4) Serosa. The "outermost" layer. Epithelial
tissue on the outside, connective tissue underneath.
Secretes serous fluid to reduce friction when the
organs of the abdominal cavity "rub" against each
•These four layers are found along the
entire length of the digestive
•The cavity in the interior of these tissue
layers is the lumen.
•The alimentary canal wall contains two
important intrinsic nerve plexuses –
the submucosal nerve plexus and
the mycentric nerve plexus. These
networks of nerve fibers are part of the autonomic nervous system and help regulate
digestive system activity (smooth muscle contraction and glandular secretion)
•The micrograph to the left shows a cross section through the
esophagus. L – lumen M – mucosa S – submucosa
TM – (tunica) muscularis. The serosa isn’t labeled, but it is the
thin layer surrounding the muscularis.
•The two types of movements of the alimentary canal wall are:
(1) mixing movements - mixes food with digestive fluid (ex.
(2) propelling movements - peristalsis (wavelike contraction) to
move food through the tube.
•The mouth is the organ of mastication (chewing).
•Food is mixed with saliva to form a bolus.
•The interior of the mouth is called the oral cavity.
•The space between the teeth and the cheeks is called
•The lining of the mouth is stratified squamous
•Beneath the lining are muscles (for chewing and facial
expression), fat, and the outer layers of skin.
•The lingual frenulum secures the tongue to the floor of the mouth.
•Thin stratified squamous epithelium, no fat, impressive
muscularity, highly-concentrated neurons, highly
vascular - blood vessels are very close to the skin's
surface - this is why lips bleed so easily and frequently.
The lip-skin border is where the mucous membranes of
the alimentary canal start!
•Lips are necessary to maintain an air-tight seal while suckling
•Lips are necessary for making some of the "letter sounds" during speech.
•Which letters of the alphabet are difficult for ventriloquists? Write them here: __ __ __ __ __ __
•Thick, mostly muscular.
•The tongue has several bony attachments
– two of these are to the hyoid bone and the
styloid processes of the skull.
•Muscle fibers in the tongue run in a number
of directions, resulting in the tongue's flexibility.
•The lingual tonsils lie atop the posterior portions of the
•It is urban legend that the tongue is “the strongest
muscle in the human body”.
•The palate is the roof of the oral cavity. Hard anterior, soft
Hard palate - palatine processes of the maxillary bone.
Soft palate - a muscular arch that ends in the uvula.
•In the back of the mouth, on either side of the soft palate
are the palatine tonsils. Composed of lymphatic tissue.
•A third pair of tonsils, the pharyngeal tonsils (AKA
the "adenoids") lie above and beyond the border of the
The Teeth 4
•Teeth are harder than bone. Teeth are made of enamel, not bone.
•Two sets are formed during development, the deciduous (primary) teeth and the
•Deciduous (baby, primary, milk) teeth number 20.
•The deciduous teeth erupt through the gingiva (gums) beginning at about 6 months and
continuing until 2-4 years old.
•The permanent teeth number 32 and have deeper roots. All of the permanent teeth but
the third molars (wisdom teeth) have erupted by the end of adolescence.
The Deciduous Teeth
•The first to erupt is usually a lower front
incisor at 6 months.
•Number 20 when all have erupted.
•The deciduous teeth are shed in the same
order that they appear.
•The roots are dissolved by odontoblasts,
and then the teeth are pushed out of
their socket by pressure from the
The Permanent Teeth
•Usually begin to appear at about 6 yrs. old.
•Last molars (3rd molars, wisdom teeth)
appear at 17-25 years old.
•3rd molars that do not erupt are called
•Incisors - chisel-shaped, used to bite off
pieces of food.
•Canines - pointed ("fangs"), used for ripping
•Premolars - AKA bicuspids and Molars are
used for grinding.
•Each tooth has a crown (above the gum) and a root (below the gum).
•The crown and the root meet at the neck (gumline).
•The tooth is covered by white, shiny enamel. Enamel is principally calcium.
•Unlike bone: enamel, once lost, is not replaced.
•Beneath the enamel is the dentin. - Still harder than bone.
•Dentin surrounds the pulp cavity which contains blood vessels, nerves, and softer
connective tissues. The pulp
cavity becomes the root canal in
each of the roots.
•The roots are anchored to the mandible
and maxillary bones by cementum
and a tough periodontal ligament.
•The periodontal ligament contains
bundles of thick collagenous fibers
that pass between the cementum
and the bone, firmly attaching
tooth to jaw.
•Producers of the fluid that goes by the name "saliva".
•Functions of saliva:
•Moistens food, making it easier to swallow.
•"Dissolves" food and helps separate "tastants" from the food mass so that they may be detected by the taste buds.
•Begins the chemical digestion of carbohydrates by utilizing the enzyme amylase.
•Contains bicarbonate ions (HCO3-) that help neutralize bacterial acids (carbonic acid) that cause tooth decay.
•Maintains mouth pH between 6.5 and 7.5 (optimum for salivary amylase)
•Saliva is produced in the 3 main pairs of salivary glands and in the minute salivary glands that are scattered throughout the
walls of the mouth and on the tongue.
•Within each salivary glands are two types of fluid-producing cells:
(1) Serous cells - produce a watery fluid that contains amylase - an enzyme that splits polysaccharides into
(2) Mucous cells - secrete a thick fluid called mucus.
•The salivary glands are innervated by nerves that are branches of both the sympathetic and parasympathetic divisions of
the autonomic nervous system.
(1) Sympathetic impulses stimulate the glands to release small amounts of a very viscous form of mucous. The
mouth lining becomes drier and "gooier" or “phlegmier”.
(2) Parasympathetic impulses promote the release of a large amount of very watery saliva. Parasympathetic
impulses are activated reflexly when a person sees, smells, tastes, or even thinks about favorite foods.
•Largest of the salivary glands.
•Lie underneath the skin of the cheek and over the masseter.
•Secretes a clear, watery form of saliva which is rich in amylase.
•This gland is also lymphoid. If you are suffering an infection,
they can swell and make you look like a "chipmunk".
Submandibular Glands (AKA Submaxillary Glands)
•Located on the floor of the mouth on the inside surface of the
•Most of the cells are serous, few mucosal cells.
•The saliva is more viscous than that of the parotid glands.
•The ducts open under the tongue and are called
Wharton's ducts. It is through these ducts that you are able to "gleek".
•Smallest of the 3 pairs of salivary glands.
•Located under the tongue.
•Cells are principally mucosal. Secretions are
thick and stringy.
•The pharynx (note spelling) connects the mouth to the esophagus.
•It has a muscular wall that aids in swallowing.
•No digestive action....food is not present long enough for action to occur.
•The pharyngeal muscles are skeletal muscles, arranged in two layers: the inner
circular muscles and the outer longitudinal muscles.
•When swallowing occurs, breathing is interrupted. Swallowing raises the pharynx,
pushing the epiglottis up against the ceiling of the trachea, sealing it and so
preventing food from "going down the wrong tube". When it does, we cough
and use the force of air to remove the food or drink from the trachea and
return it to the pharynx for re-swallowing.
•Students are taught that the pharynx is divided into three regions:
1. The Nasopharynx – located above the soft palate. It
communicates with the nasal cavity and provides a
passageway for nose breathing. The eustachian
(auditory) tubes open into the nasopharynx.
2. The Oropharynx is behind the mouth. This is where
“postnasal drip occurs”.
3. The Laryngopharynx is located below the oropharynx. This
portion is for the passage of food only; it is not a
respiratory pathway. It connects to the esophagus.
•The esophagus is 9 to perhaps 14 inches long.
•The walls of the esophagus can and do collapse. If they did not, we would constantly "detect" and
"share" the contents of our stomachs with others.
•The esophagus descends behind the trachea.
•It passes through the mediastinum down to an opening in the diaphragm the esophageal hiatus, below
which it joins the stomach.
•Mucous glands are found in the mucosa and submucosa of the esophagus.
•At the base of the esophagus is the lower esophageal sphincter. (AKA the "cardiac sphincter") This
sphincter is usually closed, and only opens to allow food's entry.
•The action of contractile smooth muscle waves that pass through the esophagus (and the rest of the
alimentary canal) are given the verb "peristalsis”.
•The stomach is not shaped like a basketball. It is shaped like the letter "J".
•It underhangs the diaphragm on the body's left side.
•Capacity for the Average Joe - 1 liter.
•Its inner surface is lined with rugae (roo'-jee) that disappear
when the stomach holds 4 Whoppers, 2 Fries, and an XL
•The stomach receives food
through the gastroesophageal sphincter,
mixes it with gastric juice, kills bacteria in
food, achieves a small amount of
absorption, mixes all of the components of
your meal (making them into a pasty
substance called chyme) and passes them
on to the duodenum in the small intestine.
•When viewed from the exterior, the stomach
can be divided into four regions:
1. The cardiac (or cardia) region - at the
top of the stomach just past the
2. The fundus - The balloon-like portion
that overlies the cardiac region.
This is usually filled with air.
3. The body region - The part of the
stomach that holds chyme.
4. The pyloric region - tapers down to
the pyloric sphincter.
•At the end of the stomach, the pyloric sphincter prevents food that passes into the small
intestine from backing up into the stomach. This is, truly, the “Point of No Return.”
•The stomach has a superthick mucosa.
•The inner surface of the stomach is dotted
with gastric pits that are openings to
the deeper gastric glands.
•Gastric glands contain 3 types of secretory
(1) Goblet cells - for mucus secretion
(2) Chief cells - secrete the protein-digesting
enzymes of the stomach.
(3) Parietal cells - secrete hydrochloric acid.
The Digestive Enzymes of the Stomach
•Pepsin is the most important of the stomach's digestive enzymes. Begins protein
digestion. Pepsin will not, however, digest mucin.
•Pepsin is secreted as the inactive precursor enzyme pepsinogen. When
pepsinogen contacts hydrochloric acid, it is denatured into pepsin.
•Gastric lipase - found in minute quantities. Acts on fats like butterfat.
•Intrinsic factor - not an enzyme, but it is a gastric juice component that enables vitamin
B12 absorption by the small intestine.
Control Of Gastric Juice Production and Release
•The hormone gastrin stimulates the gastric glands to secrete gastric juice.
•Gastrin is produced under parasympathetic control when food enters the stomach
or when one's thoughts turn to food.
•Parasympathetic impulses to the stomach are carried by the Vagus nerve.
Absorption By The Stomach
•The stomach wall is poorly adapted for food absorption; it has too much mucus.
•The materials that WILL pass through the stomach wall include water, glucose,
certain salts, alcohol, and lipid-based drugs of several types.
Contraction Of The Wall Of The Stomach
•Because the stomach has 3 muscle layers, peristalsis is non-directional and results
in the mixing of food rather than the forward movement of food.
•Chyme (food mixed with gastric juice) enters the small intestine one little squirt at
a time so that it may be neutralized by duodenal secretions of bicarbonate.
•Solid fat stays in the stomach the longest (3-6 hours), followed by proteins, carbs,
and liquids, which remain in the stomach for only a short period of time.
•The stomach may empty a 2nd way - vomiting.
•The vomiting center is located in the medulla oblongata.
•Imminent vomiting is signaled by taking deep breaths and excessive
salivation accompanied by pallor and feelings of nausea.
•Both the diaphragm and abdominal muscles contract during the act to
increase the force of repulsion.
•The vomiting center is stimulated by overstretching of
receptors in the stomach wall, drugs which elicit
vomiting (emetics), bacterial toxins in contaminate food,
and sometimes rapid changes in the change of the
body's direction (commonly caused by TheScrambler).
•Food next enters:
•Chyme is squirted in small quantities into the duodenum (1st foot or so) of the small
intestine. Chyme must be liquefied to pass through the pyloric sphincter.
•As food enters the duodenum, it is mixed with fluids from the pancreas, liver, and
•The pancreatic duct connects with the duodenum at the same place where the
common bile duct from the liver and gall bladder enters the duodenum. A
ring of smooth muscle - the sphincter of Oddi - surrounds this opening.
of Oddi is here!
•The small intestine fills most of the abdominal cavity. It is 0-14 feet long in a living person.
•It is in the small intestine that chemical digestion is completed, most food materials are
absorbed, and indigestible residues are passed on to the large intestine.
•The small intestine has three "regions": one you already know about - the duodenum. The
other two are the jejunum (2nd part of the S.I.) and the ileum (3rd. part).
•The ileum and jejunum are suspended by a double-layered but thin membrane called the
•The mesentary contains blood vessels, nerves, lymphatic
vessels, and lymph nodes.
•A membrane called the greater omentum
covers the stomach and small intestine
like an apron. It is here that fat is
deposited and one develops a "pot belly".
•The inner wall of the small intestine is covered with uncountable tiny projections
called (intestinal) villi (vee'-lee). They project inward toward the intestinal
•Each villus has a lining of simple columnar Columnar
epithelium interspersed with goblet
cells (for mucus production). Within the center of Goblet
each villus are blood capillaries, a single lymph Cell
capillary (called a lacteal), and nerve fibers.
•In addition to goblet cells, the small intestine contains mucus-secreting glands called
Brunner's glands that are buried in the submucosa.
•Intestinal glands at the base of each villus secrete large amounts of a watery fluid. This fluid
has a neutral pH and lacks enzymes.
•Intestinal enzyme secretion occurs from epithelial cells on the surfaces of the microvilli.
These enzymes include:
Peptidases - split polypeptides into the 20 different amino acids.
Sucrase, maltase, and lactase - split disaccharides into monosaccharides.
Intestinal lipase - splits fats into fatty acids and glycerol.
Nuclease - splits DNA and RNA into nucleotides.
•Many adults secrete insufficient lactase, which is necessary to digest milk sugar.
•If lactose remains undigested, it creates a hypertonic internal environment and draws water
into the small intestine lumen. Concurrently, intestinal bacteria break the lactose
down and produce organic acids and gases. The result is bloating, intestinal
cramps, and diarrhea.
•To avoid the symptoms of lactose intolerance, the victim can avoid dairy products or take
lactase in pill form before eating or drinking dairy.
•The end products of organic molecule digestion are small enough to fit through the
mucosa of the small intestine and the walls of the blood capillaries and
lacteals. These end-products include monosaccharides, amino acids, fatty
acids, and nucleotides – all major monomers of complex life polymers.
•The small intestine has an internal absorptive surface area the size of a tennis
•Absorption occurs by either active or passive mechanisms. Absorption involves not only
nutrient monomers (listed above), but also water and electrolytes.
•Water is absorbed passively, by osmosis. More water is absorbed in the small
intestine than in the large intestine (2 liters per day for the S.I., 1 liter per day
for the L.I.)
•Electrolyte absorption is active (ie. it utilizes ACTIVE TRANSPORT).
•Monosaccharide transport occurs by either facilitated diffusion or active transport
into the epithelial cells lining the intestine. From there, the monosaccharides
move passively into the blood capillaries by simple diffusion.
•Amino acids are absorbed by active transport through the intestinal lining. Once
across the lining, the monomers move passively into the bloodstream.
•The end products of fat digestion are typically fatty acids, glycerol, phospholipids,
and cholesterol molecules. These molecules readily diffuse into the epithelial
walls of the small intestine BECAUSE THEY ARE FAT SOLUBLE. Here, they are
resynthesized into fat droplets (called chlyomicrons) that diffuse into the lacteals.
Lymph in the lacteals carries these droplets to the bloodstream.
•The major mixing movement in the small intestine is termed segmentation. The
chyme is cut into segments by sphincter-like contractions in the walls, and the
food in each segment is "swished" back and forth so
that digestion and absorption may occur.
•Peristalsis in the small intestine is weaker and slower Where the small
than in the esophagus or stomach. large intestine
•A sphincter muscle called the ileocecal valve separates unite.
chyme in the small intestine from the large intestine.
The appearance of
the large intestine to
•The large intestine as a diameter (not a length) greater than the small intestine. And thus,
•Its length can reach 1 1/2 meters (5 feet).
•It begins on the lower right side of the abdominal cavity
- here, the ileum and the cecum unite. Then, the
L.I. rises, transverses the abdominal cavity over
the small intestine, and plunges rapidly on the
body's left side.
•The cecum is a dilated, pouch-like structure that
hangs beneath the ileocecal junction. Hanging
underneath it is the appendix.
•The appendix contains lymphatic tissue. If it becomes
inflamed or infected, it might require removal. If it enlarges and
breaks open, the peritoneum becomes infected (peritonitis), a
potentially fatal condition.
•The four sections of the L.I. are the ascending colon, the
transverse colon, the descending colon, and the S-
shaped sigmoid colon.
•At the end of the sigmoid colon is the rectum, which lies against
the sacrum, to which it is attached.
•The last 1 1/2-2 inches of the L.I. is the anal canal. Two sphincter
muscles, the internal and external anal sphincters, regulate the canal.
•The wall of the large intestine includes the 4 tissue
layers that typify the GI tract.
•There are no villi in the large intestine.
•The wall is arranged in a series of pouches called haustra.
Here, fat is deposited in the serosa of the wall
(this fat is not present in the small intestine serosa).
•Hemmorrhoids - enlarged branches of the rectal vein.
Functions of the Large Intestine
•Very limited or no chemical digestive function.
•There is an overabundance of mucous-producing goblet cells line the mucosa. Mucus helps
hold the fecal mass together and helps maintain a neutral pH (to combat bacterial
•Water and electrolytes are reabsorbed in the first half of the L.I. 90% of the water
that enters the L.I. is reabsorbed.
Intestinal flora - the bacteria that occupy the L.I. - chiefly E. coli.
•These bacteria synthesize vitamin K, B12, thiamine, and riboflavin. These vitamins
are absorbed by the intestinal mucosa.
Vitamin K – helps modify proteins after they are synthesized on ribosomes.
Vitamin B12 – aids the nervous system and helps in blood formation.
Thiamine – necessary for neural function and carbohydrate metabolism.
Riboflavin – plays a key role in energy metabolism.
•Bacterial actions in the large intestine may give rise to flammable (methane) and
odious (phenol, hydrogen sulfide, indole, skatole, and ammonia) intestinal
•Food materials that humans are incapable of digesting end up in the fecal mass:
•Cellulose - because we lack the enzyme necessary to digest it!
•Seed coats and covers
•Bone, cartilage, and tendon
•The color of the fecal mass relates to the bile pigments from dead red blood cells. The bile
pigments (shades of red, brown, and green) enter the food tube in the duodenum and
are altered by intestinal bacteria. The color of the fecal mass does NOT relate to the
items upon the dinner plate.
•The fecal mass is about 75% water.
•The defecation reflex occurs when a person holds and deep breath and forcefully contracts
the abdominal wall muscles. Intestinal contraction ensues, followed by the relaxation
of the external anal sphincter.
•Synthesizing digestive enzymes is the digestive system function of the pancreas.
•Enzyme synthesis is an exocrine function (to contrast it with the endocrine function of the
The Structure of the
•The "head" of the pancreas is tucked
in the duodenal loop and the
tail bumps up against the This is the
•The cells that synthesize the
digestive pancreatic fluids are
called acinar cells.
•Acinar cells secrete their enzymes
into small tubes, which unite
to form larger tubes and ,
ultimately, form the
•The pancreatic duct unites with the
common bile duct to form a short tube
called the hepatopancreatic ampulla.
•It is here that digestive enzymes from the
pancreas, mixed with bile from the liver,
enters the small intestine to aid in food
•Pancreatic juice contains several digestive enzymes that digest all 4 organic molecule
groups (carbohydrates, lipids, proteins, & nucleic acids.)
•Here are the most important Pancreatic Enzymes:
Pancreatic amylase Splits starch or glycogen into disaccharides.
Pancreatic lipase Splits triglycerides into fatty acids and glycerol.
and Carboxypeptidase Reduce proteins to amino acids.
Pancreatic nucleases Split nucleic acids (DNA, RNA, ATP) into nucleotides.
•Pancreatic juice also contains bicarbonate to neutralize the harsh acids arriving
in the duodenum from the stomach.
•The hormone secretin is released into the bloodstream from the intestinal mucosa
upon the arrival of chyme in the duodenum. Secretin stimulates the pancreas,
which secretes pancreatic juice.
•The liver is sometimes called "The Elvis of Organs"
•The liver is on the body's right side, underneath the diaphragm, protected
by the lower ribs. It is reddish brown in color, highly vascular.
•The liver has more functions than any other
organ in the human body!
•The liver is the chief chemical converter
in the human body.
•It also serves as a site of destruction, a
storage facility, and a protein
•It is a good organ to eat because it is where
iron is recycled.
Liver Menu Items Matching – Match With Arrows
Liver 'n Onions Liver Loaf Liver Pate' Braunshweiger Raw Liver
Functions of the Liver
•It helps maintain levels of blood sugar by storing excess carbohydrates as glycogen.
•Lipids are metabolized in the liver and lipids are converted to phospholipids, lipoproteins,
•Carbohydrates and proteins are converted to fat in the liver.
•Amino acid deamination occurs in the liver. This means that amino acids are
stripped of their NH3 group so that they are structurally similar to
carbohydrates. In this form, they may be used for energy. The leftover
NH3 molecule is converted to urea and becomes a component of urine.
•Blood proteins (clotting factors) are produced in the liver
•The liver stores glycogen, iron, vitamins A, D, and B12.
•Liver cells help destroy damaged red blood cells.
•Liver cells phagocytize foreign antigens.
•The liver removes toxic substances (such as alcohol) from the blood.
•The liver stores 200-400 mL of blood.
•The liver secretes bile for fat emulsification during digestion.
•The liver is surrounded by a fibrous capsule.
•The human liver has 2 major lobes and two minor lobes (your
cat will have 5!)
•Major lobes: Left lobe and Right lobe
•Minor lobes: Quadrate lobe (near the gall bladder) and
Caudate lobe (near the vena cava)
•The falciform ligament separates the two lobes.
•Each lobe is divided into many hepatic lobules.
•Within the lobule there are many hepatic cells that radiate
outward from a central hepatic vein. Cells are
separated by hepatic sinuses.
•Also within the lobules are bile canals, which receive
secretions from the liver cells. The bile canals unite
to form bile ducts.
•Blood is carried to the liver through the hepatic
portal vein (from the stomach and small
intestine) and the hepatic artery (which carries
oxygenated blood from the aorta).
The Composition of Bile
•Bile is the yellowish, green fluid produced by hepatic (liver) cells.
•Bile is the only secretion of the liver. It is a greenish-yellow fluid that exits the liver through
the hepatic duct and goes to either the small intestine (for use) or to the gall bladder
(for storage). In either instance, its fate is to end up in the small intestine.
•The Composition of Bile: water, bile salts (most common bile solid), bile pigments,
•The bile salts perform the digestive function of emulsification - reducing larger
droplets of fat into tiny droplets that digestive enzymes (lipases) can act upon.
•The bile pigments (bilirubin and biliverdin) are the breakdown products of hemoglobin.
Bilirubin is reddish, biliverdin is green. You see traces of these colors in a bruise, as
RBCs are broken down by phagocytes in the same way as they are in
the spleen and liver.
•The yellowish skin of jaundice results from the deposition of bile
pigments. I’m a baby with
•The liver secretes NO DIGESTIVE ENZYMES. in an incubator
under a UV
•The gall bladder is a pear-shaped sac located
in a depression on the inferior surface
of the liver.
•The liver sends bile to the gall bladder
through the cystic duct, which unites
with the hepatic duct to send bile to the
duodenum through the common bile
•It is lined with columnar epithelial cells.
•Its wall is lined with smooth muscle.
•The gall bladder stores and concentrates bile
between meals. When a meal arrives
at the small intestine from the stomach,
the gall bladder is filled with bile!
•The gall bladder releases bile when stimulated by
cholecystokinin from the small intestine.
•Gallstones may form in the duct system or within the gall bladder if bile is too concentrated!
The gall bladder
and liver of a cat.