Exam 3: G.I. and Metabolism Flashcards
What is the G.I. System from mouth to anus?
Alimentary canal
What are the functions of the G.I. system?
Food ingestion, propulsion, digestion, absorption, and defecation
What is the elimination of wastes called?
Defecation
What lines the lumen from mouth to anus and is the deepest layer?
Mucosa
What does mucosa secrete?
Mucus, enzymes, hormones
What does the mucosa do?
Secretes substances, absorbs nutrients, protects from pathogens
What tissues line the stomach to rectum?
Simple columnar epithelium
What tissues line the oral cavity and esophagus?
Non-keratinized stratified squamous epithelium
What type of tissue lines the lamina propria?
Areolar connective tissue
What is the smooth muscle that helps increase surface area and causes minute movement for intestinal functions?
Muscularis mucosa
What is the submucosa made of?
Areolar connective tissue with vessels and nerves
What is the muscularis externa comprised of?
2 layers of smooth muscles (circular and longitudinal)
What does the muscularis externa do?
Push food along the tract
What is the outermost/most superficial layer of the G.I?
Serosa
What type of tissue is the serosa made of?
Simple squamous epithelium
What type of membrane is the serosa?
Mesothelium
What is the particular kind of serosa that lines the viscera called?
Visceral peritoneum
What is the mesothelium that lines the abdominal wall called?
Parietal peritoneum
What layer of serosa produces fluid?
Parietal peritoneum
What stimulates the G.I. tract?
Vagus nerve (parasympathetic nervous system)
Does the stomach stretch or contract in the presence of food?
Stretch
What is the series of intrinsic neurons located in the G.I tract?
Enteric nervous system
What controls glands and the muscularis mucosa?
Submucosal nerve plexus
Where is the submucosal nerve plexus?
The submucosa
What controls movement of the intestines?
Myenteric nerve plexus
Where is the myenteric nerve plexus?
Between the circular and longitudinal muscles of the muscularis externa
What are the two components of the enteric nervous system?
Submucosal nerve plexus
Myenteric nerve plexus
What is motility?
Movement
What is motility of the intestines called?
Peristalsis
What is taking food in?
Ingestion
What is the process of chewing?
Mastication
What muscles are involved in mastication?
Temporalis, masseter, pterygoids
Where does digestion begin?
The mouth
What in saliva begins digestion?
Amylase/ptyalin
What does amylase/ptyalin break down?
Starch
What is starch broken down into?
Smaller carbohydrates, and eventually, glucose molecules
What is amylose?
A plant starch
How many muscles are in the tongue?
9
What anchors the tongue to the floor of the mouth (to prevent “swallowing of the tongue” or its posterior movement?
Lingual frenulum
What are projections containing most of the taste buds?
Papillae
What are the smallest papillae on the dorsum of the tongue to give it friction?
Filiform
Which projection on the tongue does not have taste buds?
Filiform
What are the larger “mushroom shaped” projections scatted over the dorsal surface of the tonuge?
Fungiform
Which are the largest papillae?
Circumvallate
How many circumvallate do we have, and where are they?
10-12 near the back of the tongue
What projections are along the sides of the tongue?
Foliate
Do the tastebuds increase or decrease in function as you age?
Decrease
What do lipases do in saliva?
Begin digesting various lipids
What does mucus do in saliva?
Lubricate food
What does lysozyme do in saliva?
Kills microbes
What are the IgA in saliva?
Antibodies (that are also found in breast milk)
What is the purpose of defensins in saliva?
Antimicrobial
What salivary gland is just in front of the earlobe?
Parotid gland
What salivary gland is on the body of the manible?
Submandibular gland
What salivary gland is on the floor of the mouth?
Sublingual gland
What nervous system stimulates the G.I. system and with what neurostransmitter?
Parasympathetic with Acetylcholine
What does atropine do and when would it be used?
Inhibits the G.I. system, would be used as a preoperative
What is it called when swallowing is voluntary first, the involuntary takes over?
Deglutition
What is it called when waves of smooth muscle contractions propel food along the G.I. tract?
Peristalsis
What is it called when you purge toxins like too much ethanol?
Vomiting
What region of the stomach is the first part connected to the esophagus?
Cardiac
What region of the stomach is on the top, rounded area to the left of the cardia?
Fundus
What region of the stomach is the largest and the main part?
The body
What part of the stomach connects to the small intestine?
Pyloric
What does the stomach activate?
Pepsin and lipases
What does the stomach break down?
Connective tissue and cellulose
What is cellulose?
Plant cell wall, or fiber
What does the stomach convert?
Fe+++ into the absorbable form Fe++
What does the stomach do to microbes?
It kills some ingested microbes
What are the folds in the stomach to increase surface area?
Rugae
What is the contents of the stomach called?
Chyme
What is the pH of the stomach? Is it basic or acidic?
pH: 2-3
Very acidic
What cells are the mucus cells in the stomach?
Goblet
What cells in the stomach produce hydrochloric acid (HCl)?
Parietal or oxyntic cells
What is hydrochloric acid (HCl) also known as?
Stomach acid
What receptors do histamine bind to in the stomach?
Type 2 histamine receptor
What happens when histamine binds to type 2 histamine receptors?
Proton pumps move cytoplasm to the cell membrane
What do proton pumps do in the stomach?
Actively pump H+ ions into the lumen
What does the proton pump exchange H+ ions for?
K+
What type of transport is seen in proton pumps?
Counter transport (secondary active)
What does H+ and Cl- make?
HCl (stomach acid)
Where is HCl made?
In the gastric lumen
What type of transport is the chloride shift?
Counter transport (secondary active)
What enzyme is used in the chloride shift?
Carbonic anhydrase
In the stomach, what does carbonic anhydrase do in the chloride shift?
The reaction produces H+ (instead of removing it)
Where does bicarb go in exchange for the chloride ion in the chloride shift?
Bicarb: pumped from the parietal cell to plasma
Where does chloride go in exchange for the bicarb ion in the chloride shift?
Chloride: enters the gastric lumen to combine with H+
What is secreted by parietal cells allowing the intestines to absorb vitamin B12?
Intrinsic factor
What happens if there’s too much stomach acid?
Gastroesophageal reflux (heart burn, etc.)
What heartburn remedy blocks histamine at the H2 receptors of parietal cells?
Histamine receptor type 2 (H2) inhibitors
What do Histamine receptor type 2 (H2) inhibitors do?
Reduce HCl production
What heartburn remedy blocks the H+ pump?
Proton pump inhibitors
What do proton pump inhibitors do?
Reduce production of HCl
Which are more effective in treating heartburn: H2 inhibitors or Proton pump inhibitors?
Proton pump inhibitors
What cells in the stomach produce pepsinogen?
Chief or zymogen cells
What does pepsinogen become in low pH?
Pepsin
What does pepsin do?
Digests proteins into smaller, yet still NON-absorbable, peptides
What cells in the stomach secrete various hormones to regulate digestion?
Enteroendocrine cells
What are the main 3 substances enteroendocrine cells secrete?
Gastrin
Histamine
Somatostatin
What is produced by the small intestines and stomach and stimulates the production of HCl?
Gastrin
Where in the stomach is gastrin produced?
Pyloric glands
What is produced by the stomach to move proton pumps from cytoplasm to the cell membrane where they can go to work?
Histamine
What is produced in the stomach to inhibit gastrin release?
Somatostatin
What is the first, or proximal, section of the small intestine (attaches to the stomach)?
Duodenum
What is the middle section of the small intestine?
Jejunum
What is the last, or distal, end of the small intestine that attaches to the colon?
Ileum
What does the small intestine do?
Absorbs nutrients, secretes fluids
What disease is where your intestines start to release all their fluids?
Cholera
What hormone secreted by the small intestine causes the pancreas to release bicarb and protease into the duodenum?
Secretin
When is secretin released?
In response to low pH entering duodenum
What hormone secreted by the small intestine that causes the stomach to make HCl?
Gastrin
When is gastrin released?
In response to rising pH in the stomach
If antacids neutralize the stomach, thus raising the pH, what might the stomach do?
Make more acid to lower the pH
Why are proton pump inhibitors better?
It doesn’t cause a feedback loop where taking antacids encourages the need for more antacids
What hormone secreted by the small intestine causing the gallbladder to release bile into the duuodenum?
Cholecystokinin
What is cholecystokinin used for/when?
Aiding in lipid digestion when they enter the duodenum
Why are the folds of the intestines important?
They increase the surface area for increased absorption of nutrients
What folds in the stomach are visible to the naked eye?
Plicae circulares and Villi
How much do plicae circulares increase SA by?
3x
How much do villi increase SA by?
10x
What folds in the stomach are microscopic?
Microvilli
How much do microvilli increase SA by?
20x
What is the total increase in SA thanks to the 3 types of folds?
3 x 10 x 20 = 600x
What do carbohydrates break down into?
Monosaccharides
How fast are carbs broken into monosaccharides?
10-20 minutes
What are triglycerides broken down into?
2 fatty acids & 1 monoglyceride
What are proteins broken down into?
Monopeptides (single amino acids)
What are monoglycerides made of?
Glycerol + 1 fatty acid
What is the body’s major detox center?
Liver
What is extramedullary hemopoiesis?
Making blood cells outside of the bone marrow
When does extramedullary hemopoiesis happen?
In cases of bone marrow suppression/disease
Can the liver make blood cells?
Yes
What is gluconeogenesis?
Making glucose from non-carbs, such as proteins
What is glycogenesis?
Combining glucose to make glycogen
Where does gluconeogenesis occur?
Liver
Where does glycogenesis occur?
Liver
What is glycogen?
Animal starch polymer made of glucose molecules
How is glycogen different than amylose?
Glycogen is branched
How does the liver regulate blood glucose?
The liver can release glucose from glycogen under the influence of a hormone
What hormone stimulates the liver to release glucose from glycogen?
Glucagon
Where does glucagon come from in the body? (what cells, and where are they)
Alpha cells of pancreatic islets
Where is glycogen stored?
Liver and muscle
Does the liver increase or decrease plasma glucose levels?
Increase, but releasing glucose from glycogen
What is glycogenolysis?
Breaking down glycogen into glucose, thus releasing glucose to the blood and increasing plasma glucose levels
What is it called when the liver breaks fatty acids into acetyl groups that can be used for metabolism?
Beta oxidation
What is the Cori cycle?
Lactic acid generated in muscles is converted into usable pyruvic acid
Where is HDL and LDL cholesterol produced?
The liver
What % cholesterol is dietary vs hereditary?
15% diet
85% genetics
Where are phospholipids made?
Liver
What is mechanical digestion?
Chewing
What is chemical digestion?
Enzymatic
What layer actually propels the food down the digestive tract?
Muscularis externa
What are the major acid producing cells?
Parietal or oxyntic cells
How many plasma proteins does the liver make?
Over 2000 (pretty much all of them except for antibodies)
What must the liver remove from amino acids before they are broken down further?
Amino group (NH2)
What is the process of removing the amino group called?
Deamination
What is the amino group (NH2) converted to by the liver?
Urea
Where is urea eliminated?
The kidneys
Where is iron stored to be used?
The liver
How does the liver destroy toxins?
By using enzymes
Will repeated exposure to toxins reduce the liver’s functioning?
Yes
What are detoxified by the liver on the “first pass”?
Water soluble compounds taken per os (by mouth)
What is bile made from?
Cholesterol
What does bile do?
Allows for digestion of fats by emulsifying (breaking them down) into tiny droplets
What are the tiny broken down bits of fats called?
Micelles
Where is bile made? Where is it stored?
Made: liver
Stored: gallbladder
What does bile contain from hemoglobin breakdown?
Bilirubin
What is produced by the small intestines due to the presence of fat, and causes the gallbladder to contract forcing bile into the duodenum?
Cholecystokinin (CCK)
What two systems does the pancreas participate in?
Exocrine and endocrine
What does the pancreas do in the exocrine system?
Produces digestive enzymes and bicarbonate ions
What does the pancreas do in the endocrine system?
Produces hormones
Where do the enzymes and ions that the pancreas makes get secreted?
Into the duodenum
What are the cells that make the enzymes and bicarbonate ions in the pancreas?
Acinar cells (acini or acinus)
Where are acinar cells located?
Outside the islets of Langerhans
What pancreatic enzyme digests starch?
Amylase
What 2 pancreatic enzymes digests oligosaccharides into individual glucose molecules?
Dextrinase
Glucoamylase
How many monosaccharides is an oligosaccharide?
3-8 monosaccharides long
What pancreatic enzymes digest maltose, sucrose, and lactose?
Maltase, sucrase, lactase
What do alpha cells in the pancreas produce?
Glucagon
What do beta cells in the pancreas produce?
Insulin
What do delta cells in the pancreas produce?
Somatostatin
What does trypsinogen become?
Trypsin
What does trypsin (made in the pancreas) do?
Digests proteins into smaller, yet still NON-absorbable peptides
What does chymotrypsin (made in the pancreas) do?
Digests proteins into smaller, yet still NON-absorbable peptides
What do peptidases (made in the pancreas) do?
Digests smaller peptides into ABSORBABLE molecules
What are examples of molecules small enough to be absorbed?
Single amino acids or monopeptides
What does carboxypeptidase do?
Breaks off amino acids from the carboxyl end of a polypeptide
What does aminopeptidase do?
Breaks off amino acids from the amino end of a polypeptide
What does dipeptidase do?
Breaks dipeptides into their amino acid components
What do lipases do?
Break triglycerides into 2 free fatty acids and 1 monoglyceride (glycerol attached to 1 fatty acid)
What does ribonuclease do?
Digests RNA
What does deoxyribonuclease do?
Digests DNA
What does the bicarbonate ion do?
Buffers H+ ions
What hormone released by the small intestines encourages bicarbonate ions to be released from the pancreas?
Secretin
Where do the hormones that are released from the pancreas go?
Directly into the blood (not using ducts)
Does glucagon production cause the liver to release glucose, if so, where does it go?
Releases glucose to increase plasma glucose
Does insulin production increase plasma glucose?
NO, it decreases plasma glucose
What does the hormone somatostatin do?
Inhibits growth hormones
What does “emulsify” mean?
Separates/breaks down
What are examples of micelles?
Triglycerides and fat soluble vitamins
What do micelles allow?
Lipids to be absorbed by the epithelium of intestines
Where do micelles go?
Stay in the intestines and then are excreted with feces
Where are triglycerides reassembled?
Smooth ER of the intestinal epithelial cells
Where do compounds go from the smooth ER?
Golgi apparatus, where it is surrounded by phospholipids and proteins
What are chylomicrons?
Small spheres found around the golgi apparatus that allow lipids to enter the intestinal lacteals
What are lacteals?
Tiny lymphatic vessels
What process do lipids use to enter lacteals?
Exocytosis
Where do lipids go from the lacteals?
The thoracic duct
Where does the thoracic duct dump?
Left subclavian vein
Do fats and other lipids pass through the liver for detox before entering the blood?
NO! They go straight to the lymphatics then the blood
What happens if a toddler ingests fat soluble toxins?
The toxins won’t be detoxed in the liver, and will go straight to vital organs
What % of per os water soluble drugs are destroyed after going through the veins and liver?
85-90%
What is the first step of the pathway for per os water soluble compounds?
Intestinal veins
Where do compounds go from the intestinal veins?
Superior mesenteric vein
Where do compounds go from the superior mesenteric vein
Hepatoportal vein
Where do compounds go from the hepatoportal vein?
Liver’s lobules
Where do compounds go from the liver’s lobules?
Liver’s sinusoids
Where do compounds go from the liver’s sinusoids?
Central vein
Where do compounds go from the central vein?
Hepatic veins
Where do compounds go from the hepatic veins?
Inferior vena cava
Where in the liver are water soluble toxins detoxified?
Sinusoids
What is the large intestine called?
Colon
What are the main functions of the colon?
Absorb water, produce bicarbonate, houses gut bacteria
What can cause bicarb loss resulting in acidosis?
Diarrhea
What do gut bacteria help breakdown?
Certain fiber components
What vitamins do gut bacteria help synthesize?
Vitamins B and K
What does gut bacteria help metabolize?
Bile components
What produces flatus or gass?
Gut bacteria
What do gut bacteria profoundly influence?
Physiology, metabolism, nutrition, immune system
What is dysbiosis?
Disruption of gut microbiota
What often causes dysbiosis?
Antibiotics
What is dysbiosis often implicated in?
Inflammatory diseases (like IBS), infections, obesity, autoimmune diseases, and response to cancer treatment
What % of feces are: dead bacteria
30%
What % of feces are: fiber?
30%
What % of feces are: fat from digested epithelial cells and dead bacteria?
10-20%
What % of feces are: inorganic material?
10-20%
What pathology is < appetite?
Anorexia
What pathology is binge eating then self-induced vomiting?
Bulimia
What NS stimulates vomiting, and with what hormone?
Parasympathetic NS, via serotonin
What is projectile vomiting?
Vomiting without retching due to CNS stimulation
What pathology is difficult or infrequent defecation?
Constipation
What can neurogenic damage to the colon cause?
Constipation
