GI Flashcards
Primary purpose of digestive tract
Primary purpose – Transfer nutrients from ingested food into body’s internal environment – Ingested food is essential as an energy source and as the building blocks of tissues
schematic pathway through GI
Oral cavity -> esophagus->
stomach -> small intestine ->
large intestine -> rectum
What is the statement concerning the amount of liquid entering and leaving Gi
The volume of fluid entering the GI tract must equal
the volume leaving
4 major functions of GI
1. Motility- muscular contractions that mix food and move it forward 2. Secretion- of digestive juices 3. Digestion- Biochemical breakdown of complex food stuffs 4. Absorption –of small absorbable units and water 5. Excretion-elimination of feces
2 types of motility in GI
Peristaltic contractions ( propulsion) Segmentation contractions : mixing
What is the general composition of digestive secretions
– Water, electrolytes, and specific organic constituents (enzymes) – Secretions are released into digestive tract lumen on appropriate neural or hormonal stimulation – Normally reabsorbed in one form or another back into blood after their participation in digestion
What is digestion
the biochemical breakdown of
structurally complex foodstuffs into smaller,
absorbable units
– Accomplished by enzymatic hydrolysis
What is enzymatic hydrolysis
adding water at the bond site
allows enzymes in the digestive secretions to break
down the bonds that hold the smaller molecular
subunits within the nutrients.
Absorbable units of macronutrients
- Carbohydrates → monosaccharides
- Proteins → amino acids
- Fats → glycerol and fatty acids
Parts of stomach
– (cardia)->Fundus ->body -> pyloric antrum
what are the parts of the rest of GI after the stomach (also valves)
Pyloric valve • Small intestine – Duodenum à jejunum à ileum • Accessory organs: pancreas and liver • Large intestine: colon and rectum • Anus
4 general tissue layers in GI
- Mucosa
- Submucosa, connective tissue and glands
- Muscularis externa
- Serosa
Describe mucosa layer in GI
Innermost layer, epithelium, connective
tissue, muscle
Describe muscularis externa in GI
inner layer of
circular outer of longitudinal, nerves
organized into a plexus-regulate
movement, mechanical breakdown
What is serosa in GI
Outer layer, connective tissue, fold
connect to form mesentry
Three layers in mucosa
Mucous elithelium
Lamina propria
Muscularis mucosae
2 types of muscular layer in muscularis externa
Circular and on top longitudinal
Serosa role
To prevent friction between other organs
Anchoring everything in place to prevent twisting
3 major pairs of salivary glands
Parotid gland
Submandibular gland
Sublingual gland
Composition of saliva
• 99.5% H2O
• 0.5% electrolytes and protein
(amylase, mucus, lysozyme)
Salivary gland composition
Serous cells are specialized to secrete an enzyme solution
Mucous cells
and then duct is lined with duct epithelium
Functions of saliva
• Salivary amylase begins digestion of carbohydrates (1 hour then deactivated) • lingual lipase (activated in stomach) • Facilitates swallowing by moistening food • Mucus provides lubrication • Antibacterial action – Lysozyme destroys bacteria – Saliva rinses away material that could serve as food source for bacteria • Rich in bicarbonate buffers (amylase works best at slightly basic pH)
In what layer lymphoid nodules are found in GI
In lamina propria (mucosa)
What cells line the esophagus and what layers
Lined with stratified squamous epithelium (has same four layers as entire digestive tract) 1.Mucosa 2.Submucosa, connective tissue and glands 3.Muscularis externa 4.Serosa
Esophagus extends between ___
pharynx and
stomach
How food is pushed through esophagus
Peristaltic waves push food through esophagus
What sphincters esophagus has at each end
Pharyngoesophageal sphincter
– Keeps entrance closed to prevent
large volumes of air from entering
esophagus and stomach
– Gastroesophageal (cardiac)
sphincter
– Prevents reflux of gastric contents
Outter serosa in esophagus has another name and it is ___
Adventitia
Stomach is
J-shaped sac-like chamber lying between
esophagus and small intestine
3 main functions of stomach
- Store ingested food until it can be emptied into
small intestine - Secretes hydrochloric acid (HCl) and enzymes
that begin protein digestion(pepsin) - Mixing movements convert pulverized food to
chyme
2 curvatures of the stomach and where do they attach to
Lesser curvature to organs behind the stomach
Greater curvature to the large intestine
Folds in stomach are called
Rugae
What glands are found in the mucosa of the stomach and what they secrete
Secretory cells: mucous, chief (enzymes), parietal (HCl and intrinsic factor) and endocrine (ghrelin hormone that regulates appetite) • Gastric pits and • Glands secrete most of the gastric juice-mucous fluid containing digestive enzymes and HCl
What does inner epithelial layer contains and what does it secrete and serves as
• Serves as protective surface • Modified for secretion and absorption • Contains – Exocrine gland cells – secrete digestive juices – Endocrine gland cells (secretes into blood or tissue) – secrete blood-borne gastrointestinal hormones – Epithelial cells – specialized for absorbing digestive nutrients
What is lamina propria, what does it have
Lamina propria-thin layer of connective tissue • Houses gut-associated lymphoid tissue (GALT) – Important in defense against disease-causing intestinal bacteria (at the base of each crypt there are cells secreting bactericidal enzymes)
what type of muscles is in muscularis mucosa
Smooth muscle
Rugae is marked by ___
depressions
called gastric pits
We have villi only in
Small intestine
Submucosa role and what is it
Thick layer of connective tissue • Provides digestive tract with distensibility and elasticity • Contains larger blood and lymph vessels • Contains nerve network known as submucosal plexus (imp for exocrine function and contraction of muscles)
Difference between circular and longitudinal muscles
Circular layer • Inner layer • Contraction decreases diameter of lumen – Longitudinal layer • Outer layer • Contraction shortens the tube
What is mesenterius
Double sheets of serous membranes composed
of parietal and visceral peritoneum
- Stabilize the positions of some organs
- Prevent intestines from getting tangled during
digestion
- Provide a pathway for blood vessels, nerves,
and lymphatic vessels servicing the digestive
tract
Digestive motility and secretion are regulated by
– Autonomous smooth muscle function
– Gastrointestinal hormones
4 aspects in gastric motility and characteristics of each
– Filling
• Involves muscular relaxation
– Enhances stomach’s ability to accommodate the extra
volume of food with little rise in stomach pressure
– Triggered by act of eating
– Storage
• Takes place in body of stomach
– Mixing
• Takes place in antrum of stomach
– Emptying
• Largely controlled by factors in duodenum
Mixing
actions in the stomach
include both
propulsion
and retropulsion
____ is main factor that influences
strength of contraction
Amount of chyme in stomach
In what state the food should be before moving to small intestine
Liquid
How duodenum and stomach regulate the emptying of chyme to SI on the example of fat
Fat is digested and absorbed more slowly than other
nutrients
• Fat digestion and absorption takes place only within lumen of
small intestine
• When fat is already in duodenum, further gastric emptying of
additional fatty stomach contents is prevented until the
existing fat is completely processed
• For ex a high fat meal may take 6 hours to empty whereas a
lean meat and potatoes meal may take only 3 hours
How duodenum and stomach regulate the emptying of chyme to SI on the example of acid
The stomach secretes HCl and highly acidic chyme is
neutralized in the duodenum by sodium bicarbonate
(secreted by the pancreas)
• Unneutralized acid in duodenum inhibits further emptying of
acidic gastric contents until neutralization can be
accomplished
How duodenum and stomach regulate the emptying of chyme to SI on the example of hypertonicity
build up of amino acids and glucose
molecules slows gastric emptying. When osmolarity
of duodenal contents starts to rise closure to stomach.
How duodenum and stomach regulate the emptying of chyme to SI on the example of distension
Too much chyme in duodenum inhibits emptying of even
more gastric contents
Factors Controlling Gastric Emptying
One of the Factors (fat, hypertonicity, acid, distension) trigger either
1. A Neural response
• Collectively called enterogastric reflex acts to slow the peristaltic
activity – smooth muscle contractions-autonomic system
OR
2. Hormonal response
• Release of GIP (gastric inhibitory peptide), endocrine hormone that
acts on gastric muscle to decrease peristalsis and thus slow
passage of food into the duodenum
• Additional factors that that influence gastric motility
– Emotions
• Sadness and fear – tend to decrease motility
• Anger and aggression – tend to increase motility
– Intense pain – tends to inhibit motility
Two distinct areas of gastric
mucosa that secrete gastric
juice
– Oxyntic mucosa
• Lines body and fundus
– Pyloric gland area (PGA)
• Lines the antrum
Gastric juice : content
(strongly acidic
secretion from glands,
enzymes ex pepsin, intrinsic
factor, mucus, water)
Three phases of gastric secretion:
Cephalic phase
Gastric phase
Intestinal phase
What is cephalic phase
Sensation or thought
about food are relayed to the brainstem (medulla). In response
parasympathetic signals to the gastric mucosa are
initiated. Stimulates secretion of gastric juice.
What is gastric phase of juice secretions
The distension of the stomach caused by the presence of food
triggers local and parasympathetic reflexes that increase secretion
of gastric juice. Gastrin (secreted by endocrine G cells) is a
digestive hormone secreted by mucosa in presence of food causes
increased secretion of gastric juice.
What is Intestinal phase
Triggers endocrine response
Once food enters the SI, stomach activity is inhibited by decreased gastric
juice secretion initiated by GIP (gastric inhibitory peptide), CCK and secretin
–opposes gastric juice secretion. Opposes action of gastrin. Stimulates
ejection of bile from the pancreas required for neutralization of HCl in the
duodenum
Two type of secretory tissues in the stomach
Oxyntic mucosa ( the upper layer) Pyloric gland area ( near the pyloric sphincter)
In what layer gastric pits are found
Mucosa
What cells oxyntic layer has
Contains contains gastric glands which have endocrine, chief, parietal, ECL (enterochomaffin-like) cells
What connects gastric gland with the surface of the stomach and what is found there
Gastric pit, with mucosa cells
Mucous cells: role and type of gland
Exocrine
secrete mucus,
protects epithelial cells in the stomach against pepsin and acid
Chief cells: role and type of gland
exocrine
release pepsinogen and chymosin
pepsinogen when
activated begins protein digestion
Parietal cells: role and type of gland
Exocrine
HCl, activates pepsinogen, denatures proteins, breaks down connective tissue, kills microorganisms, intrinsic factor imp for vitamin B12 absorption
ECL: role and type of cell
Exocrine neuroendocrine
Release histamine that stimulates parietal cells
Pyloric gland area has what type of cells
contain mucous
cells and G cells, D cells
Role of g cells and what type of cells
Endocrine
G-cells secrete gastrin which stimulates
exocrine cells- to secrete greater gastric
juice which has high HCl and pesinogen.
Mechanism to ensure that when there is
food in the stomach there will be enough
juice and enzymes there to digest it.
promotes digestion
D cells : role and type of cell
Endocrine
D cells produce the only inhibitiry secretions-somatostatin • Acts to inhibits parietal cells (HCl), G cells (gastrin which increases digestive juice secretion) and ECl cells.
difference between endocrine and exocrine glands
Endocrine: ductless glands
that secrete hormones
• Exocrine-secrete through
ducts into a cavity
Role of HCl
Activates pepsinogen to active enzyme pepsin and provides acid medium for optimal pepsin activity – Aids in breakdown of connective tissue and muscle fibers – Denatures protein – Along with salivary lysozyme, kills most of the microorganisms ingested with food
How HCl gets produced in gastric parietal cells
H-K pump on the apical surface of parietal cells pumps K in and H+ out. NOTE: H+ is coming from carbonic acid, a combination of CO2 and H2O in parietal cells. It is unstable , so it breaks down to HCO3- and H+. HCO3- goes out of the cells to the capillary through chloride shift and this Cl- from blood can get inside parietal cells
Chloride ions are pumped into the lumen of the stomach, where it reacts with H+
The gastric mucosal barrier made up of the following components enables the stomach to contain acid without injuring itself:
1) The luminal membranes of the gastric mucosal cells are impermeable to H+ so that HCl cannot penetrate into the cells
2) The cells are joined by tight junctions that prevent HCl from penetrating between them
3) A mucus coating over the gastric mucosa offers further protection
What happens when the gastric mucosal barrier is damaged
Gastric ulcers
What is the cause of 60% of ulcers
Helicobacter pylori
How H.pylori survives the acid in the stomach
H pylori has a unique, acid gated membrane channel, which effectively controls the amount of alkali produced by the bacterium to combat gastric acid, allowing it to survive and grow in gastric acid.
Where usually you can find H.pylori in the stomach
In Fundus where there is less acid
It uses flagella to burrow itself below mucus cells
How H.pylori causes ulcers
Damage mucus barrier and
tight junction
• Allows HCl to damage
intestinal tissue
H.pylori is treated with
Antibiotics
What is the other cause of ulcers apart form H.pylori
emotion/stress can increase
gastric juice secretion
What is the way to treat ulcers if not concentrating on bacteria
By PPI (Proton pump inhibitors) to prevent HCl formation
Examples of PPI
omeprazole, Lansoprazole
Action of PPI
It can act at different levels: inhibit H/K ATPase, so no Hydrogen pumped into the stomach
What is GERD and what is the treatment
When lower esophageal sphincter fails to stay closed and stomach acid damages the lining of the esophagus
Treated with PPIs
Ulcers can be from ____
the
overuse of NSAIDs (a drug class that reduce pain, decrease fever, prevent blood clots and, in higher doses, decrease inflammation) or H.
Pylori or stress/emotions
Pancreas is
Mixture of exocrine and endocrine tissue
• Elongated gland located behind and below the
stomach
Endocrine function of pancreas
performed by Islets of Langerhans • Found throughout pancreas • Secrete insulin (Beta cells-causes uptake of glucose) and glucagon (released when low glucose)
Exocrine function of pancreas
Secretes pancreatic juice consisting of • Pancreatic enzymes (Trypsinogen, lipases, nucleases) actively secreted by acinar cells • Aqueous alkaline solution actively secreted by duct cells that line pancreatic ductsimportant for neutralizing stomach contents in duodenum
What cells secrete pancreatic enzymes
Acinar
exocrine secretion of pancreas are regulated by
Secretin-(from intestinal mucosa)
– CCK-Cholecystokinin (from intestinal mucosa)
– Both act to stimulate release of pancreatic juice
What are proteolytic enzymes in pancreas
Trypsinogen - converted to active form trypsin (converting
enzymes sits poised on mucosal epithelium)
• Chymotrypsinogen – converted to active form chymotrysin
Action of pancreatic amylase
Converts polysaccharides into the disaccharide amylase
What is particular about pancreatic lipase
Only enzyme secreted throughout entire digestive system that
can digest fat
What cells secrete NaHCO3 in pancreas
Duct cells
What is proteose
a water-soluble compound produced during
digestion by hydrolytic breakdown of proteins
Protein is broken down to peptides and proteoses by proteases in gastric and pancreatic juices.
What is going to break down peptides and proteoses to amino acids
peptides:intestinal peptidases
Proteoses: proteases in pancreatic juices
Is pepsinogen active?
No, pepsin is active
How liver is important to digestion
secretion of bile
salts which are important for fat digestion
What is the largest gland in the body
Liver
Anatomy of liver
Consists of two lobes which are highly vascularized
Liver functions
detoxification
- bile secretion
- stores iron, vit D, A B12
- site of hematopoiesis during fetal development
Right and left lobe of the liver is separated by
Round ligament
All the nutrients from the intestine are going to the liver by
Hepatic portal vein
Functional unit of liver is
Liver acinus
Liver acinus has the form of ___, and each end has ___
Hexagon
Hepatic triad: hepatic portal vein, hepatic artery and bile ductule
Functions of liver
Synthesis and secretion of bile
Storage of glycogen and lipid reserves
Maintenance of normal blood levels of glucose, AAs and FAs
Synthesis and interconversion of nutrient types
Synthesis and release of cholesterol bound to transport proteins
Inactivation of toxins, lipid-soluble drugs
Storage of iron reserves
Storage of fat-soluble vitamins
Absorption and breakdown of circulating hormones (insulin, epinephrine) and immunoglobins
How liver and gall bladder is connected to intestine
ducts from the liver that carry the bile to be ejected into the
duodenum
• The hepatic ducts fuse with the gallbladder cystic duct, to
form the common bile duct that enters into the duodenum
Where bile is stored between meals
Stored and concentrated in gallbladder
What are lecithins, where they are produced and what is their function
Derivatives of cholesterol
– Convert large fat globules into a liquid emulsion
– After participation in fat digestion and absorption,
most are reabsorbed into the blood
Blood flow through liver
From intestine - hepatic portal vein
From the heart: hepatic artery
From liver to inferior vena cava-hepatic vein
What nutrients are stored in the liver
Glucagon
Fat-soluble vitamins A, D, E, and K
How liver monitors and adjust circulating nutrients
High blood glucose triggers synthesis of glycogen
• Low blood glucose triggers breakdown of glycogen and
release of glucose
What is the function of Phagocytic Kupffer cells in the liver
remove old or damaged
RBCs, debris, and pathogens from blood
What is the function of plasma proteins secreted by liver
Determine osmotic pressure of plasma
– Function as nutrient transporters
– Key elements of clotting and complement cascades
What is NAFLD
The most frequent form of fatty liver disease
– namely the non-alcoholic fatty liver disease
(NAFLD)
– form of chronic liver disease, resembling the
histological changes of alcoholic liver disease
– found in subjects who do not abuse alcohol
– Is tightly-linked with type II DM
– prevalence of NAFLD is growing worldwide due
to the increasing prevalence of obesity, diabetes
and the metabolic syndrome.
What is NASH and how it is identified
Non Alcoholic Steatohepatitis (NASH)
Identified by abnormal lipid accumulation and presence of inflammatory cells
NAFLD progression
Healthy liver->NAFLD->NASH
This steps are reversible
From NASH to cirrhosis is irreversible
What is steatosis
comprises abnormal accumulation of triglycerides in
hepatocytes in response to metabolic, toxic, and viral conditions
What is the normal thing about liver and aging
Macrovesicular steatosis
A progression of macrovesicular steatosis is
Microvesicular
What is cirrhosis
chronic or scarred liver as a result of chronic inflammation due to hepatits, chemicals that destroy hepatocytes, parasites that infect the liver, or alcoholism
What is hepatitis
inflammation of the liver caused
by viruses, drugs, and chemicals
Hepatitis A: cause, symptoms and effect
spread by fecal contamination of objects (food, clothing, toys, eating utensils: fecal-oral route) - Loss of appetite, malaise, diarrhea, nausea, fever, chills - Does not cause lasting liver damage
Hepatitis B: cause, symptoms and effect
spread primarily through
sexual contact and contaminated syringes
and transfusion equipment; also via saliva
and tears (bodily fluids)
- Can produce cirrhosis and possible liver
cancer
- Can be carriers
Hepatitis C is similar to
Hepatitis B
Common bile duct and pancreatic duct are both controlled by
Hepatopancreatic sphincter
Where gallbladder is found
the posterior surface of the
liver’s right lobe
Functions of the gallbladder
Stores bile
– Releases bile into duodenum, but only under
stimulation of hormone cholecystokinin (CCK
How much bile there can be in gallbladder and what is happening with it over time
Full gallbladder contains 40–70 mL bile – Bile composition gradually changes in gallbladder: • Water is absorbed • Bile salts and solutes become concentrated
Where most digestion and absorption of food happens and what is done to make it more efficient
Small intestine
Surface area increased by circular folds, villi, and
microvilli
The end of small intestine is
ileocecal valve
Functions of small intestine
Segmentations mix chyme with digestive juices
and bring food to mucosa for absorption; peristalsis
2. Completes the digestion of carbohydrates,
proteins, and lipids; begins and completes
digestion of nucleic acids
3. Absorbs ~90% of nutrients (including water) that
pass through the digestive system
What is folds of mucosa
and submucosa
Circular folds (plicae circulares):
What is villi and microvilli
Villi: fingerlike projections of mucosa; increase SA
- Microvilli: projections of the apical membrane of the absorptive cells (villi)
Structure of villi
- Each is covered by epithelium with a core of
lamina propria with an arteriole, a venule, a
capillary network, and a lacteal embedded)
3 parts of small intestine
Duodenum-the uppermost (shortest)portion and is the part to which the pyloric end of the stomach attaches – Jejunum- commences at point where the tube turns downwards – Ileum –(longest) last segment with no clear demarcation
2 types of digestive motility and their function
Propulsive (peristaltic) movements
– Push contents forward through the digestive tract
• Mixing movements (segmentation)
– Serve two functions
» Mixing food with digestive juices promotes digestion
of foods
» Facilitates absorption by exposing all parts of
intestinal contents to absorbing surfaces of digestive
tract
Segmentation movements
ringlike contractions
Segmentation is initiated by
pacemaker cells in small intestine
which produce basic electrical rhythm (BER)
Circular smooth muscle responsiveness is initiated by
distension of intestine, gastrin, and
extrinsic nerve activity
What is migrating motility complex
a cyclic, recurring motility pattern that occurs in the stomach and small bowel during fasting; it is interrupted by feeding.
Sweeps intestines clean between meals
Who is doing the work of digestion in small intestine
Juice secreted by small intestine does not contain
any digestive enzymes
• Digestion
– Pancreatic enzymes continue carbohydrate and
protein
– Brush-border enzymes complete digestion of
carbohydrates and protein
– Fat is digested entirely within small intestine
lumen by pancreatic lipase
Most of absorption happens in
duodenum and jejunum
Lining of small intestine is changed every __
3 days
How TGs undergo hydrolysis and absorption
Triglycerides are subsequently broken into monoglycerides and longand short-chain fatty acids • Short-chain fatty acids can often be absorbed • Bile salts surround longchain fatty acids and monoglycerides forming tiny spheres called micelles • Then undergo hydrolysis by pancreatic lipase • Absorbed by brush border
Where chylomicrons are assembled
Golgi in small intestine cells and then through lacteal into lymph
Amylase function
breaks down starch, glycogen into disaccharides
How proteins are absorbed
After digestion
Di and tripeptides cotransport paired with H+ via Na(in)-H(lumen)+( pump
Amino acids contransport with Na
Small peptides are carried intact across the cell by transcytosis-“ blood
Parts of large intestine
– Colon
– Cecum
– Appendix
– Rectum
Parts of colon
ascending colon, transverse colon,
descending colon, sigmoid colon
Function of large intestine
Reabsorption of water – Reabsorption of bile salts – Absorption of vitamins (vitamin K, pantothenic acid B5, biotin) produced by bacteria -Preparation of feces for excretion
Difference between anatomy of large and small intestine
Has a larger diameter and thinner wall than small intestine
– The wall of the colon:
• Forms a series of pouches (haustra)
What is haustra
Haustra permit expansion and elongation of colon
Muscle tone in taeniae coli creates the haustra
What is taeniae coli
Three longitudinal bands of smooth muscle (taeniae coli):
• Run along outer surfaces of colon
• Deep to the serosa
• Similar to outer layer of muscularis externa
Borders of ascending and transverse colon
Ascending Colon
– Begins at superior border of cecum
–
bends at right colic flexure (hepatic flexure)
• Transverse Colon
– Crosses abdomen from right to left; turns at left colic
flexure (splenic flexure)
– Is separated from anterior abdominal wall by greater
omentum
Sigmoid colon starts ___
At sigmoid flexure
When we start to have an urge to defecate
Movement of fecal material into rectum
2 sphincters in anal
Internal anal sphincter:
• Has smooth muscle cells, not under voluntary control
– External anal sphincter:
• Encircles distal portion of anal canal
• A ring of skeletal muscle fibers, under voluntary control
Histology of the large intestine
Lack villi or other structures that increase SA
– Abundance of mucous cells; mostly absorptive
and goblet cells
when haustral churning occurs
Haustra remain relaxed and become distended
while they fill
- Distension reaches a certain point, walls contract
and squeeze contents into next haustrum
- Peristalsis occurs at a slower rate
What is appendix
Vestigial organ: shrunken remainder of cecum
– Is dominated by lymphoid nodules (a lymphoid
organ
What is appendicitis, cure, causes
Inflammation of the appendix • High mortality • Requires immediate surgical removal • Possible causes: - Obstruction - Low transit time - Low dietary fiber intake - (none are mutually exclusive)
Gastrin: stimulus, origin, target and effects
Vagus nerve stimulation or arrival of food in the stomach (produced in stomach)
Arrival of chyme containing large quantities of undigested proteins ( produced in duodenum)
Target: stomach
Effects; stimulate production of acids and enzymes, increases motility
Secretin: stimulus, origin, target and effects
Arrival of chyme in the duodenum
Produced in duodenum
Target: pancreas, stomach, liver
Effects: stimulates production of alkali buffers
inhibits gastric secretion and motility
Increases rate if bile secretion
CCK: stimulus, origin, target and effects
Arrival of chyme containing lipids and partially digested proteins
Secreted in duodenum
Pancreas-stimulates production of pancreatic enzymes
Gallbladder: Stimulated contraction of gallbladder
Duodenum: causes relaxation of sphincter at base of bile duct
stomach-inhibits gastric secretion and motility
CNS-may reduce hunger
Gastric inhibitory peptide: stimulus, origin, target and effects
Arrival of chyme containing large quantities of fats and glucose
ORIGIN: duodenum and stomach
Target: pancreas -stimulates release of insulin
In stomach -inhibits gastric secretion and motility
What is the second leading cause if cancer mortality in Canada
Colon cancer
potential causes of colon cancer
Incidence increased among persons with family history
• Also increases with persons with Crohn’s
disease, ulcerative colitis and those with
adenomatous polyposis (genetic: autosomal
dominant)
• Diet also plays a role
- Dietary fat intake (increases bile acid synthesis,
may be converted into carcinogens by bacterial
flora in colon)
- Refined sugar intake (enhances above)
- Fiber intake (increases stool bulk thereby diluting
and removing potential carcinogens)
- Adequacy of protective micronutrients such as
vitamins A,C, and E in diet (refined diets often
contain reduced amounts of A,C, and E which
may act as oxygen free radical scavengers
-Polips grow
