1
GI, Hepatobiliary, and Pancreatic System
Adam Bein
12/20/2013 6:00 AM
Nerves of the Oral Cavity
Organ/Part
Tongue
Papillae on upper surface
of the tongue
Nerve #
cranial nerve
7th & 9th cranial nerves
12th
Nerve name
Hypoglossal Nerve
7th and 9th cranial nerves.
Facial nerve
Glossopharyngeal nerve
Medulla
Pons
Purpose
Mediates (parasympathetically) the rate of secretion of saliva when anything is in the mouth.
Mediates (parasympathetically) the rate of secretion of saliva when anything is in the mouth.
Along w/the Pons, regulate the reflex of the constrictor muscles of the pharynx contracting when food is entering the esophagus.
Along w/the Medulla, regulate the reflex of the constrictor muscles of the pharynx contracting when food is entering the
esophagus.
Tongue notes
The tongue keeps food between the teeth.
The first step in swallowing is the elevation of the tongue.
Salivary Glands
There are 3:
Salivary Gland
Parotid
Submandibular
Sublingual
Purpose
Carry saliva to the oral cavity.
Carry saliva to the oral cavity.
Carry saliva to the oral cavity.
Salivary Gland Digestive Enzymes
Digestive Enzymes
Amylase
Lingual Lipase. RRR
Ptyaline. RRR
Purpose
The only digestive enzyme in saliva that functions in the mouth is amylase. However, food usually doesn’t remain the mouth long enough for amylase to have any significant effect.
Amylase digests starch to maltose.
This is activated by acidic pH. It begins it’s action in the stomach.
? From where does this come?
? Where is this found?
Comes from the salivary glands. ??? Converts starch to dextrin.
Sphincters of the GI System in order:
Name of the sphincter
Lower Esophageal Sphincter (“L.E.S.”) aka:
Cardiac Sphincter aka:
Gastroesophageal Sphincter aka:
Esophageal Sphincter
Pyloric Sphincter
Sphincter of Oddi
Location & Purpose
Found at the bottom end of the esophagus.
Relaxes to let food enter the stomach. Contracts to prevent the backflow of stomach contents into the
esophagus.
Located at the bottom of the stomach and the top of the small intestine. More accurately, located between
the Pyloic area of the stomach and the Duodenum area of the small intestine.
Located in the wall of the Duodenum. Contents dump into the Duodenum thru it from the Pancrease,
Gallbladder, and Liver.
Problems
If it doesn’t close properly gastric juices splash up and into the
esophagus.
2
Stomach Notes
It is located in the upper L quadrant.
It lies between the esophagus and the duodenum.
It mainly serves as a reservoir for food-not for digestion.
Parts of the Stomach
The fundus is the top curve (the roof if you will).
The pyloris is the bottom area (the floor). Below the pyloris is the duodenum area of the small intestine.
The sphincter between the stomach’s pyloris area and the small intestine’s duodenum area is the Pyloric Sphincter.
Gastrin
Gastrin is a hormone.
Gastrin is secreted by the Gastric Mucosa.
The presence of food in the stomach stimulates the secretion of the hormone Gastrin by the Gastric Mucosa.
Gastrin increases the secretion of Gastric Juice.
Gastric Juice
The stomach’s digestive enzymes are found in the gastic juice.
Gastric juice is secreted parasympathetically.
Digestive Enzymes of the Stomach
Digestive Enzyme
Pepsinogen
Pepsin RRR
Hydrochloric Acid
Gastric Lipase
Intrinsic Factor
Purpose
An inactive enzyme that activates to Pepsin by hydrochloric acid.
Is this in the stomach??? Pepsin comes from Pepsinogen when Pepsinogen is activated by Hydrochloric Acid.
Pepsin begins the digestion of proteins into polypeptides.
Needs a pH of 1-2 to function.
Activates Pepsinogen into Pepsin.
Creates the pH of 1-2 that:
1) Is necessary for Pepsin to function.
2) Kills most organisms which enter the stomach.
3) Breaks down (“denatures”) proteins.
Helps digest triglycerides.
Aids in the absorption of Vitamin B12.
Chyme
What you eat that ends up in the stomach gets turned into “Chyme”.
Small Intestine
The small intestine is 20 feet long (6-7 meters).
The diameter is 1 inch.
The small intestine begins at the stomach and ends at the colon at an area called the “Cecum”.
The first 10 inches of the Small Intestine is called the “Duodenum”.
3
The Duodenum has the Hepatopancreatic Ampulla /Ampulla of Vater. Two tubes eventually feed into the Hepatopancreatic Ampulla:
1) One tube that comes from the Pancreas.
2) One tube that comes from the Liver and the Gallbladder. This tube is called the “Common Bile Duct” and splits in two: One tube coming down from the
liver, one tube coming down from the Gallbladder.
The next 8 feet of the Small Intestine is called the Jejunum.
The next 11 feet of the Small Intestine is called the Ileum.
In the small intestine digestion occurs.
End products of digestion are absorbed:
Into the blood. ??? Where?
Into the lymph. ??? Why & what?
The Beginning of Digestion in the Small Intestine
1) The chyme enters the small intestine.
2) Bile enters the duodenum of the small intestine. The bile came from the _________ ? Gallbladder?
3) Enzymes from the pancreas enter the duodenum of the small intestine.
4) The intestinal mucosa produces:
1) To complete the digestion of disaccharides to monosaccharides:
1) The enzyme sucrose.
2) The enzyme maltase.
3) The enzyme lactase.
2) Peptidases. These complete the digestion of proteins to amino acids.
3) Nucleosidases and Phosphatases. These complete nucleotide digestion. ???
5) The duodenal mucosa secretes the hormone “Cholecystokinin”. Cholecystokinin stimulates contraction of the gallbladders smooth muscle, forcing bile into the duodenum.
Absorption of Nutrients in the Small Intestine
Lots of surface area is needed. Extensive folds include are called circular folds (“Plicae Circulares”). They include:
1) Fold of the mucosa (“Villi”).
2) Microscopic folds of the cell membranes on the intestinal epithelial cells (“Microvilli”). In this area there is:
1) A capillary network. Water soluble nutrients (monosaccharides, amino acids, minerals, & water soluble vitamins) are absorbed into the blood here.
2) A lymph network (“Lacteal”). Fat soluble vitamins, fatty acids, and glycerol (???) are absorbed into the Lymph here.
The Large Intestine
It starts at the ileus of the small intestine.
It is 5 feet long.
It’s diameter is 2.5 inches.
The first part is called the “Cecum”.
Between the end of the small intestine (the “Ileum”) and the Cecum is a valve. The valve is called the “Ileocecal Valve”). The purpose of the Ileosecal valve is to prevent a backflow of contents from the large intestine up and
back into the small intestine.
The Liver
The liver fills the R side and center of the upper abdomen.
Contains: The Hepatic Portal System. This is a filtering system.
1) Hepatic Artery: This is how the liver receives it’s oxygenated blood.
2) The Portal vein:
1) This is where the dissolved nutrients are brought first before being sent out to the body.
2) Blood comes from the spleen. ???
4
The Liver:
Makes bile.
Regulates blood levels of nutrients.
Removes toxic substances.
Metabolises carbs.
Metabolises amino acids
Metabolises lipids
Synthesizes plasma proteins.
Phagocytosis
Forms bilirubin
Stores
Detoxification
Activates Vit. D.
Cells called hepatocytes make bile. The bile then flows thru a series of ducts & tubes until it leaves the liver by way of the common hepatic duct. The common hepatic duct then
joins the cystic duct of the Gall Bladder and they form the “Common Bile Duct”. It is thru the Common Bile Duct that bile flows to go into the duodenum.
1) Stores extra glucose as glycogen.
2) Changes glycogen back to glucose.
3) Changes fructose & galactose to glucose.
1) The liver can make 12/20 “Non-Essential Amino Acids” (via a process call ‘transamination’). The remaining 8 (of 20 total) must be consumed in the diet.
2) Excess amino acids are ‘deaminated’, the amino group is removed, and what’s left is a carb chain. The carb chain is converted into a simple carb (used for energy or converted
to fat for energy storage).
3) The amino groups are converted to urea (a nitrogenous waste product that is removed from the blood by the kidneys then excreted in urine).
1) Forms “Lipoproteins”. Lipoproteins transport lipids in the blood to other tissues. ??? Why do u need proteins to transport lipids?
2) Makes cholesterol.
3) Excretes excess cholesterol into bile to be eliminated in the feces.
4) Splits fatty acid molecules into 2 carbon acetyl groups. This process is called “Beta Oxidation”. The carbon acetyl groups can be used by the liver to produce energy or can be
combined to form ketones and those ketones get transported to other cells for energy production. ??? Is this a link to ETOH??
1) Makes albumin. Albumin helps maintain blood volume by pulling tissue fluid into capillaries.
2) Makes clotting factors:
1) Prothrombin. ???
2) Fibrinogen. Circulates in the blood until needed for chemical clotting.
3) Makes globulins. ???
1) Become part of lipoproteins
2) Act as carriers for other molecules in the blood.
There are macrophages in the liver which stay only in the liver. They phagocytize worn down erythrocytes, leukocytes, and some bacteria (the bacs were in the colon).
1) Worn down erythrocytes have their hemoglobin removed. The hemoglobin then has it’s ‘heme’ removed. The heme is made into bilirubin by the hepatocytes. The worn
down erythrocytes also come from blood collected from the spleen and the red bone marrow.
The liver stores:
1) Iron
2) Copper
3) the fat soluble vitamins: A, D, E, K.
4) the water soluble vitamin: B12.
1) The liver makes enzymes which change harmful substances into less harmful substances.
2) The liver converts ammonia (from the metabolism of protein) into urea.
Along w/the skin and the kidneys, the liver performs a role in providing the body with vitamin D.
The Gallbladder
Is located under the Liver.
It stores bile.
It concentrates bile.
It gets the bile from the liver. It gets the bile via the Hepatic Duct and then the Cystic Duct.
5
The Pancreas
Is 6 inches long.
Has glands called “Acini”.
Acini glands produce digestive secretions.
The small ducts connect to the large ducts, those connect to the pancreatic duct, the pancreatic duct joins the common bile duct at their emptying spot where the meet the duodenum. They go thru the “Sphincter of Oddi” and then empty into the duodenum thru the
“Hepatopancreatic Ampulla” (“Ampulla of Vater”).
Pancreatic enzymes are involved in the digestion of all 4 of the organic molecule categories.
1) Pancreatic Amylase digests starch to maltose.
2) Pancreatic Lipase converts emulsified fats to fatty acids and monoglycerides.
(more physiology on page 688).