Digestive System- Part 2 Flashcards
4 Regions of the Stomach
1) Cardia
2) Fundus
3) Body
4) Pylorus
Cardia (2)
1) Where Esophagus opens into Stomach
2) Lower Esophageal Sphincter surrounds opening (physiological constrictor that can’t be seen anatomically)
Fundus
Superior part of stomach that lies to the left of the Cardia.
Body of Stomach (3)
1) Largest part
2) creates a Greater Curvature & Lesser Curvature of Stomach
3) Narrows to form Pylorus
Pylorus (aka & 4 parts)
1) aka Gatekeeper
2) Pyloric Antrum- wider portion of funnel toward Body
3) Pyloric Canal- narrow part leads to Pyloric Orifice into the Small Intestine
4) Pyloric Sphincter- thick ring of smooth muscle that surrounds Pyloric Orifice and regulates movement of stomach contents into small intestine
Hypertrophic Plyoric Stenosis
Common stomach defect where phyloric sphincter is greatly thickened thus interfering with normal stomach emptying
What is unique about the Muscularis layer of the stomach? (2)
1) It contains 3 layers
2) Inner oblique layer helps generate the strong stomach contractions that physically break down food
Rugae
Folds of Submucosa & Mucosa (deep to Muscularis) that arrange when stomach is empty and allows them to stretch when Volume increases
Gastric Pits (2)
1) Tube-like cavities in the Mucous (Innermost) lining of the stomach
2) Serve as openings for gastric glands to secrete acid & other substances
5 Types of Epithelial Cells of the Stomach
1) Surface Mucous cells
2) Mucous Neck cells
3) Parietal cells
4) Chief cells
5) Endocrine cells
Surface Mucous cells (location, function, production, connection type, replacement rate (5))
1) Only stomach epithelial cell not found in gastric glands –> on surface of gastric pits
2) Protect stomach wall from acid & digestive enzyme damage
3) Produce Alkaline Mucus (which protects the stomach lining and prevents the stomach from digesting itself)
4) Connected by tight junctions (additional barrier)
5) Rapidly replaced when damaged
Mucous Neck cells
Parietal cells
Chief cells
1) MN- located near openings of gastric glands & Produce mucus
2) P- Produce hydrochloric acid & intrinsic factor
3) C- Produce pepsinogen (enzyme) & gastric lipase (enzyme that digests lipids in stomach)
Endocrine cells (epithelial cell of stomach) (2)
1) Produce regulatory hormones & paracrine factors
2) Several types of endocrine cells (histamine producing, gastrin secreting, & somatostatin secreting)
What is the primary function of the stomach?
To store & mix chyme (some digestion & absorption occur but not its major functions)
6 Stomach Secretions
1) Hydrochloric acid (HCI)
2) Intrinsic Factor
3) Mucus
4) Pepsinogen
5) Gastric Lipase
Hydrochloric Acid (produced by & function)
1) Produced by Parietal cells
2) Decreases stomach pH (keeps pH level at about 2) by killing bacteria that’s ingested
3) Activates Pepsinogen to Pepsin conversion by keeping pH low (can only occur at low pH)
Pepsin/Pepsinogen (produced by & function (4))
1) Pepsinogen (inactive form of Pepsin) produced by Chief cells
2) Packaged in Zymogen granules and released by exocytosis when pepsinogen secretion is stimulated
3) Activated by HCl to form Pepsin
4) Digests proteins into smaller peptide chains
Intrinsic Factor (produced by & function (3)))
1) Glycoprotein produced by Parietal cells
2) Binds to Vitamin B12 & aids in its absorption in the small intestine
3) B12 important to DNA synthesis & continual RBC production –> lack of B12 absorption can lead to Pernicious Anemia (RBC disorder)
What is the importance of Intrinsic Factor to B12? (2)
What results occur from lack of B12? (2)
1) B12 important to DNA synthesis & continual RBC production
2) lack of B12 absorption can lead to Pernicious Anemia (RBC disorder)
3) lack of B12 absorption can lead to neurological symptoms such a peripheral neuropathy
Gastric Lipase (produced by & function & 1 fact)
1) Produced by Chief cells
2) Digests minor amounts of lipids
3) More active during infancy
Proton Pump (3)
1) H+ - K+ exchange pump
2) Key player in formation of Hydrochloric Acid by parietal cells in gastric glands of stomach
3) Actively transports H+ across the mucosal surface of the parietal cells into the lumen of the stomach
PRODUCTION OF HCL VIA PROTON PUMP STEPS???
PG. 930
What are the chemical messengers (hormones) that regulate stomach secretions? (3)
1) Gastrin
2) Secretin
3) Cholecystokinin
What are the 3 phases of the regulation of stomach secretions (aka creation of gastric juice)?
1) Cephalic- “Get Started”
2) Gastric- “ Go for it”
3) Intestinal- “Slow down”
Describe the Cephalic (reflex) Phase of gastric juice production (3)
1) Initiated by sensory receptors in the head which leads to increased gastric juice production
2) Parasympathetic response via Vagus (X) nerve
3) Emotional distress can trigger sympathetic stimulation which can slow this phase
Describe the Gastric Phase of gastric juice production (3)
1) Stretch receptors in stomach wall stimulated when food enters stomach (triggering further production)
2) Phase can also be triggered by Gastrin (hormone) produced by G cells (aka enteroendocrine cells) in the pyloric atrium
3) When stomach content pH falls below 2, Gastrin & overall stomach secretion production blocked.
Describe Intestinal Phase of gastric juice production (2)
1) Stretch receptors in the duodenum stimulated when chyme enters small intestine.
2) Gastric secretions inhibited when chyme pH falls below 2 via Secretin, Cholecystokinin, & GIP (Gastric Inhibitory Peptide) (hormones) & Enterogastric Reflex (nervous system reflex)
How does Secretin affect gastric secretions during gastric juice production? (2)
1) Hormone released during the Intestinal Phase in response to ACIDIC SOLUTIONS in the Duodenum.
2) INHIBITS gastric secretions of both Parietal & Chief Cells
How does Cholecystokinin (CCK) affect gastric secretions during gastric juice production? (2)
1) Hormone released during Intestinal Phase in response to FATTY ACIDS & LIPIDS in the Duodenum & Proximal Jejunum.
2) INHIBITS gastric secretions & stomach emptying
How does the Enterogastric Reflex affect gastric secretions during gastric juice production? (3)
1) LOCAL reflex & nervous system reflex integrated within Medulla Oblongota
2) Activated by duodenal wall extension, presence of irritating substance in duodenum, reduced pH, & hypertonic or hypotonic solutions
3) INHIBITS gastric secretions & gastric motility
How long does it take the stomach to empty after eating?
How long does it take carbohydrates, proteins, & lipids to pass through the stomach?
- 2-6 hours after eating
- Carbs- 2 hours
- Proteins- 4 hours
- Lipids- 6 hours
What are the 3 sections of the small intestine?
1) Duodenum
2) Jejunum
3) Ileum
What does the small intestine connect to?
Where does it receive secretions from? (2)
- Connects at the stomach with the duodenum & with the large intestine at the ileum via Ileocecal Sphincter (ileocecal valve)
- Liver & Pancreas release secretions into the Duodenum
Absorption & Digestion Facts about the Small Intestine (4)
1) Where greatest amount of digestion & absorption of nutrients & water occurs
2) Major absorption sites= Duodenum & Jejunum
3) Absorption of water via OSMOSIS
4) Over 90% of water is absorbed before the large intestine
3 Structural Modifications that Increase surface area of Small Intestine
1) Circular folds- formed by mucosa & submucosa layers
2) Villi- finger like projections of the mucosa
3) Brush border- combined microvilli that cover entire surface
4 Cell Types in the Mucosa of the Small Intestine
1) Absorptive Cells- in microvilli & Produce digestive enzymes & absorb digested food
2) Goblet cells- produce protective mucus
3) Granular cells (PANETH cells)- protect intestinal epithelium from bacteria via lysozyme secretion
4) Endocrine cells- produce regulatory hormones
2 Glands of the Small Intestine (location, akas, & which cells they house)
1) Intestinal Glands aka CRYPTS OF LIEBERKUHN- located in the Mucosa layer at the base of villi. –> house Absorptive & Goblet cells
2) Duodenal Glands aka BRUNNER Glands- located in the Submucosa layer and open into the base of the Intestinal Glands –> house Granular & Endocrine cells
2 Enzymes of Small Intestinal Wall
1) AKA Brush Border enzymes because they are bound to the membranes of absorptive cell microvilli
2) Disaccharidase- breaks down disaccharides to monosaccharides
3) Peptidases- hydrolyze Peptide bonds between small amino acid chains
Anatomy of Liver (4)
1) Largest internal organ (3lbs)
2) Right and Left lobe seen from anterior view (front) & separated by Falciform Ligament
3) Quadrate lobe & Caudate lobe seen from posterior view
4) Houses Gallbladder (small bile storing sac) & Porta Hepatis
3 Parts of Porta Hepatis
1) Hepatic Portal Vein- where blood flows into liver
2) Hepatic Artery- how blood leaves liver
3) Hepatic Ducts- 2 ducts, one from each right and left lobe where bile flows out
Histology of Liver (4)
1) Made up of HEPATIC CORDS- strings of cells coming out of central vein of each lobule.
2) Cords consist of HEPATOCYTES- functional epithelial cells around veins that take up nutrients from portal blood
3) Hepatic Sinusoids- blood channels in spaces between Hepatic Cords that contain Hepatic Phagocytic cells AKA KUPFFER cells
4) Kupffer cells destroy worn out blood cells, bacteria & foreign debris in the blood passing through the Sinusoids-.
Liver Functions (6)
1) Production of Bile
2) Production of Heparin (anticoagulant), plasma proteins, & blood clotting proteins
3) Detoxification of blood
4) Breakdown of hemoglobin
5) Removal of bacteria & other foreign matte from blood
6) Storage of vitamins, minerals, & Glycogen
What does Bile consist of? (5)
Bile production site & pathway
1) Water
2) Ions
3) Bilirubin (Bile pigment)
4) Cholesterol
5) Bile Salts
Produced by liver then sent to Gallbladder which releases it into the Duodenum (small intestine)
How does Bile play a role in digestion? (3)
1) NO DIGESTIVE ENZYMES
2) Neutralizes stomach acid –> alkaline pH of bile mixes with acidic chyme entering the Duodenum which neutralizes pH
3) Emulsifies lipids- via bile salts which is necessary for digestion by lipase
ENDOCRINE Cells of Pancreas & their 3 hormones produced
EXOCRINE Gland of Pancreas & product
- Pancreatic Islets aka Islets of Langerhans Cells produce 3 Hormones
1) Glucagon
2) Insulin
3) Somatostatin
-Acinar glands which house acinar cells that produce digestive enzyme aka enzymatic component of pancreatic juice)
Pancreatic Juice
(location & contents (7 TOTAL –> Will Sodium Pan-fry Pancakes or Try Chopping Proteins)
- Released into Duodenum (Small Intestine) from Pancreas
1) Water (majority)
2) Sodium Bicarbonate (maintains pH of 7.1-8.2)
3) Pancreatic amylase (Maltose & Isomaltose digestion)
4) Pancreatic lipase (lipid digestion into fatty acids & monoglycs)
5) Trypsinogen (Activated/converted into Trypsin by Enterokinase)
6) Chymotrypsinogen (Activated/converted into Chymotrypsin by Trypsin)
7) Procarboxypeptidase (Activated/converted into Carboxypeptidase by Tripsin)
4 Parts of the Large Intestine
1) Cecum
2) Colon
3) Rectum
4) Anal Canal
How long does it take for material to pass through the Large intestine vs. small intestine?
18-24 hours for the Large intestine & site where chyme is converted to feces
3-5 hours in the Small intestine where chyme passes thorugh
Cecum (2)
1) Connects small and large intestine at ileocecal junction
2) Vermiform Appendix- worm looking structure attached to head
Organic Molecule (aka, 4 classes, & content)
1) aka Macromolecules
2) 4 Classes –> Carbohydrates, Lipids, Proteins (aka Polypeptides), & Nucleic Acids
3) Contains Carbon (and usually Hydrogen) & may also contain Nitrogen, Oxygen, Phosphorus, & Sulfur
Carbohydrates
1) Contain Carbon, Hydrogen, & Oxygen (often in 1:2:1 ratio)
2) Monosaccharides= small sugars (Glucose & Fructose)
3) Disaccharides= Pairs of monos –> Sucrose
4) Polysaccharides= complex carbs, long chains of monos –> EX: Starch, Cellulose, & Glycogen
Lipids
1) Contain large amounts of C and H but very little O
