Physiology Ch. 13 (Digestion)

Accessory Organs

1 Liver 2. Gallbladder 3. Pancreas

4 Major Buffers (lab)

1. Carbonic Acid/Bicarbonate (HCO3-) 2. Phosphate (PO4 3-) 3. Ammonia (NH3) 4. Hemoglobin (Hb)

Major Digestive Organs

1. Mouth 2 Stomach 3. Small Intestine

Eat normal

Acid is buffered by pancreas

Enzyme produced in the mouth

Amylase (carbohydrates)

Helicobacter Pylori

Bacterium found in the stomach that can survive the acid and cause stomach ulcers. Waste product very acidic. Give antibiotic to kill bacteria.

Digestion

Break down macromolecules into smaller molecules to be used as nutrients. Carbohydrates --> glucose Lipids --> Fatty acids/glycerol Protein --> amino acids

Carbonic Acid/Bicarbonate

Buffer, HCO3 HCO3- + H+ --> H2CO3 Saturated after addition of one H+.

Hemoglobin

Buffer, Hb Hb + H+ --> HbH Can bond with numerous H+.

Ammonia

Buffer, NH3 NH3 + H+ --> NH4- Saturated after addition of one H+

Phosphate

Buffer, PO4 3- PO4 3- + H+ <-> HPO4 2- + H+ <-> H2PO4 1- + H+ <-> H3PO4 Can absorb 3 H+

Gastroesophageal Reflux Disease (GERD)

Caused by eating fast, overeating, or reflux. HCl from the stomach (pH 1-2) can cause ulcers in the esophagus or small intestine (pH 7-8). Increase in esophageal cancers. Gastric reflux Acid reflux Esophageal reflux "Heart burn"

Bolus

Chewed food. Swallowed and passes through esophagus by peristaltic activity.

Nutrients

Completely digested food (chyme). Absorbed through the walls of the small intestine (through microvilli) and enter bloodstream, where it will travel through the blood to reach the cells.

Amylase

Digestive Enzyme Digests carbohydrates (starch). 2 Types: Salivary: Produced in the mouth (A) by the salivary glands. Pancreatic: Produced in the pancreas (C).

Lipase

Digestive Enzyme Digests fat. Produced in the pancreas (C), released into the small intestine.

Carboxypeptidase

Digestive Enzyme Digests protein. Produced in the pancreas (C), released into the small intestine.

Chymotrypsin

Digestive Enzyme Digests protein. Produced in the pancreas (C), released into the small intestine.

Trypsin

Digestive Enzyme Digests protein. Produced in the pancreas (C), released into the small intestine.

Peptidase

Digestive Enzyme Digests protein. Produced in the small intestines (D).

Pepsin

Digestive Enzyme, Digests protein (small amount). Produced in the stomach (B) by combination of HCl & pepsinogen.

Glucose Insulinotropic Peptide (GIP) (Glucose-Dependent Insulinotropic Peptide)

Digestive Hormone Release by: small intestine (due to presence of glucose in duodenum) Target: Pancreas (islets) Action: Cause pancreas to release insulin (insulin targets protein channels on cell membrane, allowing glucose to enter cell for metabolism)

Lactase

Digestive enzyme. Digests lactose (carb) Produced in the small intestines (D).

Maltase

Digestive enzyme. Digests maltose (carb) Produced in the small intestines (D).

Sucrase

Digestive enzyme. Digests sucrose (carb) Produced in the small intestines (D).

Secretin

Digestive hormone Released by: Small intestine (due to presence of acidic chyme-acid in duodenum) 1. Target: Pancreas Action: cause pancreas to release buffers into the small intestine to stabilize pH. 2. Target: Liver cells (hepatocytes) Action: Cause liver to begin making bile.

Cholecystokinin (CCK)

Digestive hormone (bile-bladder-movement) Released from: Small intestine (due to presence of fat & protein) 1. Target: Pancreas Action: Release of pancreatin into the small intestine. 2. Target: Gall bladder Action: Cause gall bladder to contract, releasing bile into small intestine. 3. Target: Hepatopancreatic sphincter Action: Cause sphincter to open, allowing pancreatin & bile to enter duodenum of small intestine (after passing through pancreatic duct).

Vasoactive Intestinal Peptide (VIP)

Digestive hormone. Release by: small intestine villi Target: Capillaries inside the villi. Action: Cause capillaries to dilate, allowing them to absorb more nutrients to be transported to all parts of the body.

Gastrin

Digestive hormone. Released by: Stomach (due to stretching of the stomach from the presence of food) "Stress" can also trigger autonomic nervous system to release hormone. 1. Target: parietal cells of stomach Action: Release HCl 2. Target: Chief cells of stomach Action: Release Pepsinogen HCI & pepsinogen combine to make stomach enzyme pepsin.

Type II Diabetics

Don't respond to GIP. GIP receptors not responsive (something blocks receptors) so insulin is not produced when needed.

Bile

Emulsifies the fat in the small intestine. (Does not digest fat) Makes it easier for lipase to digest fat (smaller globules increase surface area). Produced by the liver, stored in the gall bladder. Released by the liver, through the hepatopancreatic sphincter, into the duodenum.

Pancreatin

Enzymes produced by the pancreas (C). Release triggered by hormone, Cholecystokinin (CCK). Enter duodenum of the small intestines through the hepatopancreatic sphincter. Trypsin Chymotrypsin Carboxypeptidase Amylase Lipase

Duodenum

First part of the small intestine. Receives the acidic chyme from the stomach. Cells lining this: Respond to protein & fat - release hormone cholecystokinin (CCK). Respond to acid - release hormone secretin.

What does cholecystokinin target

Gallbladder - bile pancreas - enzymes hepatopancratic sphincter - open Bile-Bladder-Movement

Lactose Intolerance

Lacking adequate amounts of lactase to digest lactose.

Microvilli

Line the small intestine. Absorb nutrients. Contain capillaries that allow nutrients to enter into the bloodstream.

Esophageal Sphincter

Located at the junction of the esophagus to the stomach.

Pyloric Sphincter

Located at the junction of the stomach to the small intestine.

Pancreas

Located posterior to stomach. Endocrine & exocrine organ. Lobules produce digestive enzymes. Islets produce hormones, insulin.

Hepatopancreatic sphincter

Located where the tubes from the gallbladder (and liver) meet with the tubes from the pancreas to join the small intestine.

Peristalsis

Muscular action of the esophagus that allows a bolus of food to pass from the mouth to the stomach.

Large Intestine

NO DIGESTION OCCURS HERE.

vitamin B12

Necessary for erythrocytes to absorb iron. Produced by bacteria in the sm. intestine.

Iron

Necessary for hemoglobin formation.

Esophageal Ulcer

No protection against acid. Acid reflux/vomit can cause damage to lining.

Duodenal Ulcer

Occurs when acid from the stomach enters the small intestine and deteriorates the lining. Small intestine does not have a lot of mucus protection. If too much acid enters, the buffers from the pancreas may not be able to keep up with it.

Stomach Ulcer

Occurs when gastric acid deteriorates the stomach lining. Stomach lining is protected by mucus from HCl. Ulcers can occur if cells that produce mucus fail to produce enough. Relatively rare - stomach normally has enough acid and has a high mitotic rate. Aspirin (acetylsalicylic acid) makes ulcers worse, prolongs bleeding, and slows the healing process.

Stomach

Partially digest protein. Stretching causes the cells to release hormone gastrin. Gastrin targets other cells to release HCl & pepsinogen (forming pepsin). Passes the acidic chyme on to the small intestines. pH = 1-2 Produces enzyme, pepsin.

Acidic Chyme

Partially digested food that has been mixed with gastric juices of the stomach (HCl) Passed into the small intestine by peristaltic activity. Once food is completely digested it is called nutrients.

Enzyme produced in the Stomach

Pepsin (protein)

Enzymes produced in the Small Intestine

Peptidase (protein) Sucrase (Carb - sucrose) Maltase (Carb - maltose) Lactase (carb - lactose)

Parietal Cells of Stomach

Produce HCl, triggered by hormone gastrin. Produce (hormone) Intrinsic Factor, triggered by hormone gastrin. Targets: sm. intestine action: absorb vit. B12 (necessary for RBC to absorb iron for Hb production)

Pancreatic Lobules

Produce digestive enzymes that are secreted into the duodenum of the small intestine. Enzymes: Trypsin Chymotrypsin Carboxypeptidase Amylase Lipase

Chief Cells of Stomach

Produce pepsinogen, triggered by hormone gastrin.

Liver

Produces bile, stored in the gall bladder.

What does the presence of acid in the duodenum trigger?

Release of secretin by small intestine.

Hydrochloric acid (HCI)

Released by parietal cells of the stomach. Mixes with pepsinogen to form stomach enzyme, pepsin.

Pepsinogen

Released by the chief cells of the stomach. Mixes with HCI to form stomach enzyme, pepsin.

Buffers

Released from pancreas (triggered by hormone, secretin), enter the duodenum of small intestine in order to control the pH of the small intestine. Raise pH: Remove H+ by bonding to them and making them no longer acidic. Lower pH: Add H+ by releasing them.

Gall Bladder

Releases bile into the duodenum of the small intestine.

"Pep" or "Tryp"

Think protein!

Stress

Triggers autonomic nervous system to release gastrin. HCL in stomach with no food. Increase chances of ulcer.

Enzymes produced in Pancreas

Trypsin (protein) Chymotrypsin (protein) Carboxypeptidase (protein) Amylase (carbs) Lipase (fat)

Mouth

Where digestion begins. Teeth mechanically break down food. Digestive enzymes break down a very small amount of carbs. Passes the bolus on to the stomach. pH = 7 Produces enzyme, salivary amylase.

Small Intestine

Where the majority of digestion takes place. Digests the remaining carbohydrates, proteins and fat. pH 7-8 (best for digestive enzymes) pH = 7-8 Produce enzymes: Peptidase Sucrase Maltase Lactase

Intrinsic Factor

acts as Hormone Produced by parietal cells of stomach. Targets: small intestine Action: Cause small intestine to absorbe vitamin B12 into bloodstream. B12 necessary for erythrocytes to absorb iron. Iron necessary for hemoglobin formation.

Bile does what?

emulsifies fat

What does the presence of protein & fat in the duodenum trigger?

release of CCK from small intestine.

What does the presence of glucose in the duodenum trigger?

release of GIP from small intestine.

Capillaries

those found inside microvilli, lining the small intestines, allow nutrients to be absorbed into the bloodstream. Dilation triggered by hormone vasoactive intestinal peptide (VIP), released by small intestines. Larger diameter can absorb more nutrients than smaller diameter.

Eat fast

too much acid to buffer. Food not digested because enzymes denatured.