Digestive System

21. Discuss the liver

- An accessory organ - Produces bile - The duodenum is the entry site for things from the liver, pancreas, and gall bladder to enter - Bile enters the small intestine at the level of the duodenum

24. Discuss the pancreas

- An accessory organ - Endocrine pancreas 1. Pancreatic islet cells secrete insulin and glucagon , controls blood glucose lvls -Exocrine pancreas 1. Acinar cells (clusters of secretory cells) secrete pancreatic juice: Zymogen granules of secretory cells contain important digestive enzymes 2. Gas a small duct and tough endoplasmic reticulum - tells you that there is lots of proteins being produced from this cell

34. Provide an overview for fat digestion

- Plz look at and understand slide 59

28. Discuss the anatomy of the large intestines and its functions

- Regions: 1. Cecum (blind ended pouch with attached vermiform appendix) 2. Colon 3. Rectum 4. Anal canal Functions: -Vitamins, water, and electrolytes are reclaimed and reabsorbed here - major sites -Major function is the production/compaction of feces and their propulsion toward the anus -Colon is not essential for life

43. Provide a summary of ATP yields

- SLIDE 72 UNDERSTAND RLLY IMPORTANT

15. Discuss gastric glands in stomach

- There are different types of gastric glands in the stomach - There are HCl producing parietal cells - There is also pepsin-secreting chief cells NOTE: -Parietal cells release HCl to activate pepsinogen really  -Chief cells release Pepsinogen, the enzyme that is involved in the breakdown of proteins

31. What are the properties and features of chemical digestion

-All chemical digestion has the following features: 1. Catabolic (makes things smaller, breaks them down) 2. Enzymatic 3. Hydrolysis -Specific digestive enzymes for the chemical digestion of carbohydrates 1. Salivary amylase, pancreatic amylase, and brush border enzymes (carbohydrate digesting enzymes: dextrinase, glucoamylase, lactase, maltase, and sucrase) - look @ and understand slide 53 plz

29. Discuss bacterial flora of the large intestine

-Bacteria enter from the small intestine or anus that do the following: 1. Colonize the colon 2. Ferment indigestible carbohydrates 3. Release irritating acids and gases 4. Synthesize B complex vitamins and vitamin K -Beneficial bacteria for the most part in the large intestine - type?

36. Provide an overview of metabolism

-Carbohydrate metabolism: 1. glycolysis 2. TCA cycle 3. electron transport chain -Lipid metabolism -Protein metabolism -Cellular respiration: catabolism of breakdown of food fuels and capture of energy to form ATP

26. Discuss the regulation of gastric secretion

-Cholecystokinin (CCK) is released from intestinal cells exposed to proteins and fat in the chyme and causes: 1. The hepatopancreatic sphincter to relax 2. Induces the secretion of pancreatic juices from the acinar cells -Secretin is a hormone like substance released from intestinal cells exposed to HCl and fat in the chyme and causes: 1. Bile secretion from hepatocytes to be enhanced 2. Secretion of bicarbonate-rich pancreatic juice by duct cells

27. Discuss digestion in the small intestine and the requirements for it

-Chyme from stomach contains: 1. Partially digested carbohydrates and proteins 2. Undigested fats -Slow delivery of hypertonic (or concentrated) chyme (do you drink water when you eat? Drink It after so the chyme is more concentrated and helps with digestion) -Delivery of bile, enzymes, and bicarbonate from the liver and pancreas -Mixing to occur

7. Discuss intrinsic and extrinsic controls

-Enteric nerve plexuses (important in how these muscle contract) initiate short reflexes in response to stimuli in the GI tract -Long reflexes in response to stimuli inside or outside the GI tract involve CNS centers and autonomic nerves -Hormones from cells in the stomach and small intestine stimulate target cells in the same or different organs - Also look at slide 12 plz

30. Provide an overview of chemical digestion

-Enzymes secreted from the mouth through to the small intestine -These act as catalysts to increase the process of Hydrolysis - what is this? Breaking bonds by adding water -Enzymes react optimally at a specific pH -Stimuli for enzyme secretion is by: the presence of food in tract; the autonomic nervous system (ANS); GI Tract hormones

32. Discuss chemical digestion of proteins

-Enzymes: pepsin in the stomach -Pancreatic proteases: 1. Trypsin, chymotrypsin, and carboxypeptidase -Brush border enzymes that further break down peptides, they are: 1. Aminopeptidases, carboxypeptidases, and dipeptidases -Absorption of amino acids is coupled to active transport of Na+ - Plz look @ and understand slide 56

13. Discuss the esophagus

-Esophageal mucosa contains stratified squamous epithelium: 1. Changes to simple columnar at the stomach - Esophageal glands in submucosa secrete mucus to aid in bolus movement (it also has the same 4 layers tho) -Muscularis: skeletal superiorly; smooth inferiorly - see previous slide - In the esophagus the circular muscles and longitudinal muscles contract - In the esophagus the gastroesophageal sphincter is closed when those muscles are contracting so acid from stomach doesn't rise NOTE: - You coontrol swalloing at the top of your esophogus but as it goes down it becomes smooth muscle and is involuntary - smooth muscle as it hits the stomach - In the esophagus the muscularous layer has two layers associaeted with it the longtitudal layer and circular muscle ****

46. Discuss lipid metabolism

-Fat catabolism yields 9 kcal per gram (vs 4 kcal per gram of carbohydrate or protein) -Most products of fat digestion are transported as chylomicrons and are hydrolyzed by endothelial enzymes into fatty acids and glycerol -Only triglycerides are routinely oxidized for energy -The two building blocks are oxidized separately: 1. Glycerol pathway 2. Fatty acid pathway NOTE: Why do u actually need fat? It is better to use fats as it produces more 9 kcal than carbs and proteins, more energy yaya u get it

5. Discuss the structure of the GI tract: the layers and the mesentery*

-Four basic layers (tunics) throughout the tract but different layers have modifications: 1. Mucosa (most inner) 2. Submucosa 3. Muscularis externa 4. Serosa (most outter) - Mesentery: it holds the GI tract and attaches it to organs so that it cant contract on itself and coil it, it keeps it in places

16. Discuss gastric gland secretions

-Glands in the fundus and body produce most of the gastric juice -Parietal cell secretions (in stomach): 1. HCl 1a. pH 1.5-3.5 denatures protein in food, activates pepsin, and kills many bacteria 2. Intrinsic factor 2a. Glycoprotein required for absorption of vitamin B12 in small intestine -Chief cell secretions 1. Inactive enzyme pepsinogen 2. Activated to pepsin by HCl and by pepsin itself (a positive feedback mechanism) -Enteroendocrine cells 1. Secrete chemical messengers into the lamina propria 1a. Paracrines: Serotonin and histamine 1b. Hormones: Somatostatin and gastrin

45. Discuss glucaneogenesis

-Glucose formation from noncarbohydrate (glycerol and amino acid) molecules -Mainly in the liver -Protects against damaging effects of hypoglycemia

44. Discuss glycogenesis/glycogenolysis

-Glycogenesis: 1. Glycogen formation when glucose supplies exceed need for ATP synthesis 2. Mostly in liver and skeletal muscle -Glycogenolysis 1. Glycogen beakdown in response to low blood glucose NOTE: Glucose is stored as glycogen in the liver - glycogen is the storage form of glucose, mostly stored in the liver

23. What are the functions of the liver?

-Hepatocyte functions 1. Process bloodborne nutrients 2. Store fat-soluble vitamins 3. Perform detoxification 4. Produce ~900 ml bile per day

11. Discuss the composition of saliva*

-Important secretion in the mouth acts to lubricate, maintains the bolus and other functions -Secreted by serous and mucous cells -97-99.5% water, slightly acidic solution (pH 6.6-6.8) containing: 1. Electrolytes—Na+, K+ 2. Contains enzymes: Salivary amylase (carbohydrates digesting) and lingual lipase (fat digesting) 3. Mucin - glycoprotein associated with mucus 4. Metabolic wastes 5. Lysozyme, IgA -> these are immune responses to bacteria in your mouth NOTE: Salivary glands secrete saliva - Serous secretion (more watery) and muscus secretion (more mucus like) - KNOW THIS: The pH of saliva, it Is slightly acidic for a reason

3. What is the function of motility?

-Important to move food from the mouth to the anus (i.e. forward movement of food along the length of the GI Tract) -Mechanically mixes food for maximal exposure to the various secretions and enzymes found in the GI Tract -Allows for maximal contact with the surface epithelial cells within the Tract for absorption NOTE: - There is smooth muscle in the digestive tract, involuntary

35. Discuss vitamin absorption

-In small intestine: 1. Fat-soluble vitamins (A, D, E, and K) are carried by micelles and then diffuse into absorptive cells 2. Water-soluble vitamins (vitamin C and B vitamins) are absorbed by diffusion or by passive or active transporters. 3. Vitamin B12 binds with intrinsic factor, and is absorbed by endocytosis NOTE: KNOW WHICH ONES ARE FAT SOLUBLE VITAMINS *

12. Discuss digestive processes: the mouth

-Ingestion - is a behavioural response -Mechanical digestion: 1. Mastication (chewing) is partly voluntary, partly reflexive - why? How? -Chemical digestion (salivary amylase and lingual lipase) -Propulsion: 1. Deglutition (swallowing) - last act of conscious control of digestion NOTE: You should know what mastication and deglutition mean

22. Discuss the microscopic anatomy of the liver

-Liver lobules 1. Hexagonal structural and functional units 1a. Filter and process nutrient-rich blood 1b. Composed of plates of hepatocytes (liver cells) -Portal triad at each corner of lobule 1.Bile duct receives bile from bile canaliculi -Liver sinusoids are leaky capillaries between hepatic plates -Kupffer cells (hepatic macrophages) in liver sinusoids NOTE: -Make sure you know the hepatocyte is part of the liver

19. Discuss the small intestine - specializations

-Major organ of digestion and absorption -2-4 m long; from pyloric sphincter to ileocecal valve -Subdivisions (anatomical divisions): 1. Duodenum (retroperitoneal) 2. Jejunum (attached posteriorly by mesentery) 3. Ileum (attached posteriorly by mesentery)

51. Discuss bio: functions and composition

-Major secretions by the liver and the gall bladder -Yellow-green, alkaline solution containing: 1. Bile salts: cholesterol derivatives that function to emulsify fats and aid in their absorption 2. Bilirubin: pigment formed from heme 3. Cholesterol, neutral fats, phospholipids, and electrolytes 4. Bile is alkaline that help to neutralize the acid from the stomach, can't have that acidity running through the body

41. Discuss the Krebs cycle

-Occurs in mitochondrial matrix: 1. Transitional phase: Each pyruvic acid that was formed by glycolysis is converted to acetyl CoA and 2 NADH's are also formed NOTE: -Unlike glycolosis that starts with glucose, this starts with pyruvic acid , need to know this doe - Review slide 70

10. Discuss mouth and salivary glands

-Oral (buccal) cavity: 1. Bounded by lips, cheeks, palate, and tongue 2. Lined with stratified squamous epithelium -Extrinsic salivary glands (3 PAIRS: parotid, submandibular, and sublingual) NOTE: - The most important part here is enzymes. When you have food in your mouth, you are activating salivary glands that excrete enzymes that help in digestion of food

38. Discuss carbohydrate metabolism

-Oxidation of glucose: C6H12O6 + 6O2 -> 6H2O + 6CO2 + 36 ATP + heat -Glucose is catabolized in three pathways: 1. Glycolysis 2. Krebs cycle 3. Electron transport chain and oxidative phosphorylation NOTE: -1 MOLECULE OF PRODUCES 36 MOLECULES OF ATP

33. Discuss lipid digestion and absorption

-Pre-treatment—emulsification by bile salts -Enzymes—pancreatic lipase -Absorption of glycerol and short chain fatty acids (the end products of all fats and lipids you ingest - TGs): 1. Absorbed into the capillary blood in villi 2. Transported via the hepatic portal vein -Absorption of monoglycerides and fatty acids: 1. Cluster with bile salts and lecithin to form micelles 2. Released by micelles to diffuse into epithelial cells 3. Combine with proteins to form chylomicrons (we find these inside intestinal cells) 4. Enter lacteals (are actually part of the lymphatic system) and are transported to systemic circulation

50. Discuss protein synthesis and essential amino acids

-Requires a complete set of amino acids: Essential amino acids must be provided in the diet -What are essential amino acids? HILLMPTV

6. Discuss mechanoreceptors and chemoreceptors

-Respond to stretch, changes in osmolarity and pH, and presence of substrate and end products of digestion -Initiate reflexes that: 1. Activate or inhibit digestive glands 2. Stimulate smooth muscle to mix and move lumen contents NOTE: - These receptors initiate reflexes in digestion. All this involves smooth muscle

42. What is the electron transport chain and oxidative phosphorylation?

-The part of metabolism that directly uses oxygen -Chain of proteins bound to metal atoms (cofactors) on inner mitochondrial membrane -Substrates NADH + H+ and FADH2 deliver hydrogen atoms -Hydrogen atoms are split into H+ and electrons -Electrons are shuttled along the inner mitochondrial membrane, losing energy at each step -Released energy is used to pump H+ into the intermembrane space

9. What is the enteric nervous system

-The second nervous system? -Neurotransmitters? -Intrinsic nerve supply of the GI tract: 1. Submucosal nerve plexus: Regulates glands and smooth muscle in the mucosa 2. Myenteric nerve plexus: Controls GI tract motility -Linked to the CNS via afferent visceral fibers -Long ANS fibers synapse with enteric plexuses: 1. Sympathetic impulses inhibit secretion and motility - when its activated the movement of the GI tract stops usually so that you are able to be in the fight mode (fight or flight) 2. Parasympathetic impulses stimulate -> rest and digest -It kind of is the 2nd nervous system, it is in the submucosal layer etc * importnt*

48. Discuss lipogenesis

-Triglyceride synthesis occurs when cellular ATP and glucose levels are high -Glucose is easily converted into fat because acetyl CoA is: 1. An intermediate in glucose catabolism 2. A starting point for fatty acid synthesis -This is opposed by the breakdown of triglycerides via Lipolysis

20. Discuss important structural features of the small intestine

-Villi 1. Motile fingerlike extensions (~1 mm high) of the mucosa which contain brushborder enzymes. Only found in small intestine -Villus epithelium 1. Simple columnar absorptive cells (enterocytes) Goblet cells NOTE: -There are microvilli ontop of villi, also only found in small intestine - SLIDE 33 plz

25. Discuss pancreatic juice

-Watery alkaline solution (pH 8) neutralizes chyme -Electrolytes (primarily HCO3-) -Enzymes: 1. Amylase lipases, nucleases are secreted in active form 2. Proteases secreted in inactive form -Protease activation occurs in duodenum 1. Trypsinogen is activated to trypsin by brush border enzyme enteropeptidase/kinase 2. Procarboxypeptidase and chymotrypsinogen are activated by trypsin NOTE: - Every single type of macromolecule you inject is somewhat broken down by pancreatic juice proteins, carbohydrates, and fats - Slide 42

49. Discuss protein metabolism

-When dietary protein is in excess, amino acids are: 1. Oxidized for energy 2. Converted into fat for storage -In oxidation, they are first deaminated (removal of the amine group); then converted into: 1. Pyruvic acid 2. A keto acid intermediate of the Krebs cycle

1. What are the two simple parts of the digestive system?

1. Alimentary canal (gastrointestinal or GI tract) -Used for mechanical and chemical digestion of food -Site of absorption of nutrients in food -Mouth, pharynx, esophagus, stomach, small intestine, and large intestine 2. Accessory digestive organs -Teeth, tongue, gallbladder -Digestive gland Salivary glands, Liver/gall bladder and pancreas NOTE: -The "food" doesn't actually enter the body, it stays in the tube, it only enters the body when you absorb it in the intestines

18. Discuss the 3 phases of digestion in the stomach

1. Cephalic phase prepares stomach for food 2. Gastric phase enhances secretion started in cephalic phase, homogenizes and acidifies chyme and initiates digestion of protein by pepsin 3. Intestinal phase controls rate of chyme entry to duodenum

39. Discuss carbohydrate metabolism stages - slide 66

1. During glycolysis each glucose molecule is broken down into two molecules of pyruvic acid in the cytosol 2. The pyruvic acid then enters the mitochondrial matrix, where the Krebs cycle decomposes it to CO2. During glycolysis and the Krebs cycle, small amounts of ATP are formed by substrate-level phosphorylation. 3. Energy-rich electrons picked up by coenzymes are transferred to the electron transport chain, built into the cristae membrane. The electron transport chain carries out oxidative phosphorylation, which accounts for most of the ATP generated by cellular respiration. NOTE: THIS IS AN IMPORTANT DIAGRAM - inslide the cell (cytoplasm) glucose can be converted into pyruvic acid, which can take part in krebs cycle (occurs in the mitchochondria) - end product of glycolosis is pyruvic acid

5. What are the two GI tract regulators?

1. Mechanoreceptors and chemoreceptors 2. Intrinsic and extrinsic controls

4. What are the major propulsive movements?

1. Peristalsis: Adjacent segments of alimentary tract organs alternately contract and relax, which moves food along the tract distally. - occurs a lot in esophogus as well as other parts in GI tract 2. Segmentation: Nonadjacent segments of alimentary tract organs alternately contract and relax, moving the food forward then backward. Food mixing and slow food propulsion occurs.

40. Discuss glycolysis

10-step pathway with unique features: 1. Anaerobic 2. Occurs in the cytosol 3. Glucose -> 2 pyruvic acid molecules -Three major phases: 1. Sugar activation 2. Sugar cleavage 3. Sugar oxidation and ATP formation -Final products of glycolysis : 1. 2 pyruvic acid 1a. Converted to lactic acid if O2 not readily available (like when you exercise) 1b. Enter aerobic pathways if O2 is readily available 2. 2 NADH + H+ (reduced NAD+) 3. Net gain of 2 ATP

14. Discuss the anatomy and histology of the stomach

Anatomy Layers specific to the stomacch are: - Oblique Layer - Rugae of mucosa - Pyloric sphincter (valve) at pylorus Histology -Cell types in gastric glands: 1. Mucous neck cells (secrete thin, acidic mucus) 2. Parietal cells - what does this do? 3. Chief cells - what does this do? 4. Enteroendocrine cells 5. Important pH change

47. Discuss lipids and Krebs cycle

LOOK AT AND UNDERSTAND SLIDE 76 NOTE: Highlight: take lipids, force them into different ascpets of the kreb cycle and form acetocolase - one biochemical step: beta oxidation needs to be in the kreb cycle for lipid metabolism ** NEED TO KNOW THIS DOE*** when you see beta oxidation you know your talking about the metabolism of fats

37. What are the stages of metabolism?

Processing of nutrients: 1. Digestion, absorption and transport to tissues 2. Cellular processing (in cytoplasm): -Catabolism (glycolysis) into intermediates -Synthesis of lipids, proteins, and glycogen 3. Oxidative (mitochondrial) breakdown of intermediates into CO2, water, and ATP or Stafes of metabolism: Stage 1: digestion in the GI tract lumen to the absorbable forms. Transport via blood to tissue cells Stage 2: Anabolism (incorporation into molecules) and catabolism of nutrients to form intermediates within tissue cells Stage 3: Oxidative breakdown of products of stage 2 in mitochondria of tissue cells. CO2 is liberated, and H atoms removed are ultimately delivered to molecular oxygen, forming water. Some energy released is used to form ATP. SLIDE 64 VERY IMPORTANT

1. What are the six essential activities that take place in digestion? Where does each one occur?

Six essential activities that takes place in digestion: 1. Ingestion, putting it in your mouth 2. Propulsion, from the oral cavity to the anal canal: physical movement - Swallowing (oropharynx) - Peristalses (esophagus, stomach, small intestine, large intestine) 3. Mechanical digestion - Chewing (mouth) - Churning (stomach) - Segmentation (small intestine) 4. Chemical digestion - In stomach and in the intestines 5. Absorption - In the intestines - some gets abosrbed directly into blood and some into lymphatic system then blood 6. Defecation - Anus

17. Discuss the stomach major functions

Stomach is there for these major factors: -Physical or mechanical digestion -Denaturation of proteins (chemical) -Enzymatic digestion of proteins by pepsin -Secretes intrinsic factor required for absorption of vitamin B12 (Lack of intrinsic factor -> pernicious anemia) -Delivers chyme to the small intestine