HA&PII Exam 4 Lecture Objectives
HA&PII Exam 4 Lecture Objectives Biol 2230-001
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Clemson University Spring 2016 Unit 4 Lecture Objectives Digestive System 1. List the organs of the digestive system, differentiating the alimentary canal organs from the accessory organs. • Overall: Food is taken in, it’s broken down, it’s absorbed into circulation, and the rest is eliminated as waste • The digestive system is a continuous muscular one-directional tube called the alimentary canal - Mouth = entry point and the continuous tube à anus - Specifically includes the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and the anus - Along the tube of the alimentary canal, the diameter changes and it is not perfectly straight - Accessory organs along the path of the tube contribute to digestive processes - Any substance within the alimentary canal is considered to be outside the body à Why must absorb nutrients into the body across the lining of the tube through the epithelial tissue and mucosal barrier - Absorption doesn’t take place until the small intestine + some in the large intestine • Accessory organs: - Tongue - Salivary glands: o Parotid gland o Sublingual gland o Submandibular gland - Pancreas - Liver - Gallbladder 2. Describe the major actions of the digestive process. • Ingestion: - Mouth connects to the pharynx à esophagus à stomach à small intestine à large intestine à anus - Ingestion: Taking food into the digestive system - Mouth: One entry point for the digestive tract • Propulsion: - The process that moves food through the digestive system - Occurs in every portion of the digestive system - Deglutition: Swallowing o Starts the propulsion of food through the digestive tract o Swallowing is the beginning part that is voluntary - Peristalsis: o Involuntary portion of deglutition that starts after the food has been swallowed and reaches the esophagus o Esophagus has smooth muscle that includes involuntary propulsion to push food down towards the stomach à Muscle movements = peristalsis • Mechanical digestion: - Physical breakdown of taking big chunks of food to smaller chunks - Occurs in a number of places - Mastication: o Chewing in the mouth to increase the surface area of food - Mixing: o As food is being mechanically broken down, it is mixing with other secretions such as saliva (mouth), gastric juice (stomach), or enzymes - Segmentation: o Tube in the alimentary canal has wave-like contractions (peristalsis) + segmentation o Segmentation has wave-like contractions similar to a water balloon where one part of the water sloshes back to one side and then to the other that helps mix things together • Chemical digestion: - Enzymatic breakdown of food - Enzymes are specific to different types of macromolecules that are broken down to their components that can then be absorbed - Chemical digestion begins in the mouth, stomach, and finishes in the small intestine • Absorption: - Movement of digested products out of the lumen of the alimentary canal through the mucosal lining à Circulation in the blood or lymphatic vessels - Small intestine: Where absorption of the digested products occurs - Large intestine: Where absorption of water occurs • Defecation: - Elimination of feces (Waste) 3. Describe the mechanisms of control of the digestive process, differentiating short and long reflexes. • Various ways that activate and deactivate the digestive system • Sensory receptors (Sensors): - Mechanical sensors: o Respond to pressure - Chemical sensors: o Respond to certain chemicals - Stimuli that activate receptors: a) Stretch: o As food enters the stomach, the stomach becomes more distended à Stretches à Activates mechanical receptors to bring about a response to get the stomach and small intestine ready b) Osmolarity: o Refers to changes in fluid composition o Chemoreceptors detect osmolarity changes c) pH changes: o Changing pH conditions turns on and off things d) Presence of specific molecules: o Arrival of proteins vs. lipids vs. carbohydrates activate the stomach differently • Nerve plexuses - Sensory receptors are linked with nerve plexuses that are associated with reflexes - 2 types of reflexes: a) Short reflexes (Intrinsic reflexes): o Sensory receptor changes the activity of that organ so that it stays entirely within the organ itself b) Long reflexes (Extrinsic reflexes): o Sensory receptor sends a signal all the way to the central nervous system, which sends a signal back to cause a change in the activity of an organ - Responses of reflexes through nerve plexuses: o Activate or inhibit secretions o Change the activity of smooth muscle contraction à Smooth muscle contraction is stimulated to mix and move § Ex: The arrival of food in the stomach activates the large intestine to release the last meal • Hormones: - Hormonal secretions can control the activity of the digestive pathway as well - Sensory receptors can cause the activation of a gland to secrete a chemical messenger 4. Define mesentery, and discuss its relationship to the peritoneum. • Thin membranous material that holds the abdominal organs in place • Underside of organs is where the mesentery holds the organs to the abdominal wall • Area with high fat storage that increases with age • Mesentery is a double layer of the peritoneum: - Parietal peritoneum attached to the abdominal wall - Visceral peritoneum covers the organs 5. List the four tunics of the digestive tract, and describe their composition and action. a. Mucosa: • Superficial tunic • Composed of predominantly simple columnar tissue • Contains goblet cells à Secretes mucous • Epithelial tissue does not have a blood supply b. Submucosa: • Some glands here can secrete enzymes and hormones (Other than just mucous) • Contains nerve fibers + lymphatic and blood vessels • Made up of dense connective tissue with many elastin fibers due to having to change shape as food passes through the alimentary canal tube c. Muscularis externa: • Smooth muscle tissue • 2 layers: Both work to move food in one direction (Peristaltic waves) a) Circular: o Inner layer o Contraction of the circular layer will change the diameter of the tube o Constricts when activated b) Longitudinal: o Outer layer on top of the circular layer o Contracts and shortens the length of the tube d. Serosa: • Thin outer layer = Visceral peritoneum that lines the organs • *In the trachea and esophagus the outer layer is called the adventitia and not the serosa 6. Describe the enteric nervous system. • The enteric nervous system is an intrinsic nerve plexus • 2 intrinsic nerve plexuses: a) Submucosal nerve plexus: - Located in the submucosa of the alimentary tube - Activation of this nerve plexus à Activation of glandular secretion + could activate smooth muscle contraction b) Myenteric nerve plexus: - More important in relation to muscle contraction - Located between the circular and longitudinal layers of the muscularis externa - Activation à Changes in smooth muscle contraction • 2 components: a) Sympathetic nerve impulses: - Signal the digestive tract to shut off b) Parasympathetic nerve impulses: - Signal the digestive tract to turn on by activating secretions and increasing motility 7. Describe the anatomy and function of each organ (alimentary and accessory) of the digestive system. • Oral (Buccal) Cavity: - Only source of ingestion - Propulsion, mechanical, and chemical digestion (Only for starches) occurs in the mouth - Palate: o Roof of mouth o Have a hard/body palate § Helps to separate the oral and nasal cavities § Gives the tongue something to push up against à Important for mechanical digestion § Deglutition (Swallowing) involves action of the tongue o Have a soft palate § Extension that goes way back to separate the oral and nasal cavity § Allows us to continue to breathe when swallowing/chewing § Where the uvula closes off the nasopharynx when swallowing • Oral (Buccal Cavity): Tongue - Accessory organ - Involved with moving food around - Mixing function à Mix food with watery secretions to form a bolus structure that will pass through the rest of the digestive tract - Functions in voluntary portion of deglutition (Swallowing) - 2 types of papillae that are ridges that cover the tongue: a) Fungiform papillae: o Makes up most of the time o Provides texture so food doesn’t just slide across the tongue o Contains taste buds o Associated with chemoreceptors b) Circumvallate papillae: o Function in group o Contain some taste buds • Oral (Buccal) Cavity: Salivary Glands - Secretory glands that produce saliva - Composed mucous and/or serous cells: o Some have mucous cells (Mucous produced for moistening) o Some have all serous cells that produce enzymes o Some have mucous and serous cells - 3 salivary glands: a) Sublingual: o Located under the tongue o Composed only of mucous cells (Moistens food so it doesn’t stick) b) Submandibular: o Contains serous and mucous cells c) Parotid o Composed only of serous cells (Produces enzymes) - Saliva: o Fluid secreted in the mouth that mixes with food to create a moist semi solid bolus that will slide down the alimentary canal o Also cleans out the mouth in getting residual food or anything out that was left between teeth à Prevention of bacteria buildup o Helps dissolve food and put it in solution à Food has to be dissolved in solution to be biologically active + for taste o Can contain enzymes that allow for breakdown of starch (But not all salivary glands are created equally) - pH: 6.75-7.0 (Slightly acidic) o Salivary amylase is only functional at this pH - 1 liter – 1 ½ liters of saliva is produced a day - Under autonomic nervous system control - Can be prompted by chemoreceptors due to certain chemicals such as lemons - Can also respond to pressure receptors à Ex: Push sublingual salivary gland with tongue à express spit out - Psychological memory component: o Digestive activity can be prompted by memory o Mouth starts watering when think about a favorable food • Oral (Buccal) Cavity: Teeth - Involved with mastication - 32 permanent and total teeth in an adult - Front teeth: o 4 incisors o Sheering wedges à Cutting teeth used to bite food off - Cuspids: o 2 total (1 on each side) o Canines à Pierce and hold food - Pre-molars: o 4 total (2 on each side on top and bottom) o Sheering teeth à Humans are supposed to each meat - Molars: o 6 total (2 on each side) o 2 others à Age 18: When the last two erupt (Wisdom teeth) § Mouth keeps getting smaller due to evolution so there is not enough room left for wisdom teeth § Causes them to come in weird places or stay compacted in the jaw bone o Flat surface à Grinding teeth, meaning humans are supposed to have an omniferous diet - Humans are born without any teeth - Primary/facidious (Sp?) teeth (Baby teeth): o 20 total à Head is mall so not too many teeth can fit o Lose them at different time - Tooth structure: o Gingiva: Gum line o Crown: § Part of the tooth on the gum line § Exposed o Root: Part of the tooth below the gum line o Neck: Connects the crown and root o Enamel: § Covers outer layer of exposed crown § Very hard structure that allows our teeth to be resistant to wear o Dentine: § Deep into enamel o Pulp: § Deep to dentine § Contain blood vessels and nerves § If there is tooth decay, there are chemical problems with the pulp à Signals sent throughout body o Dentine and pulp run down through the root where there is no enamel but there is cementum that holds the tooth in the socket in the skull o Pulp exits down through the root via the root canal—Where nerves and blood vessels go out as well o Root canal: Dental procedure too where the tooth is dead from the root • Pharynx: - Food moves from the buccal cavity à oropharynx à laryngopharynx - Epiglottis covers up the trachea so food goes down the esophagus when swallowing occurs - The only thing that occurs in the pharynx is propulsion—Food is moved from the mouth to the esophagus • Esophagus: - Muscular tube - Collapses when swallowing is not occurring - When swallowing occurs, the bolus comes in and causes the muscular tube to distend à Why C-rings of cartilage are necessary on the trachea since the bolus will extend into the trachea and then it collpases again behind it - All that happens in the esophagus is propulsion - 2 physiological sphincters: o Not actual valves- Points where the esophagus bends o Help regulate the flow of food and move food in one direction a) Upper esophageal sphincter b) Gastroesophageal sphincter • Stomach: - Storage tank - Food doesn’t have to be processed and can be stored in the stomach for a while (Depends on how much is in the stomach) - Empty volume of stomach: 50 mL - Stomach can stretch to accommodate up to 4 L of content - Propulsion + churning via muscle contractions à Have mechanical breakdown - Secretion of enzymes à chemical breakdown - Digest starch in the mouth, but once the bolus reaches the stomach, the low acidic pH change causes the starch digestion to stop - Protein digestion occurs in the stomach - Anatomy of the stomach: a) Cardiac: o Where the esophagus first empties into the stomach o Close to the heart b) Fundus: o Top portion c) Body: o Central portion d) Pylorus: o Where the stomach reaches the small intestine e) Lesser and greater curvature f) Pyloric sphincter: True sphincter o Regulates the emptying of the stomach o Food isn’t moved through all at once à Small amounts are let out at time to be more efficient in the digestion and later the absorption processes - Bolus à stomach and leaves the stomach as a converted liquid form called chyme - Rugae: o Folds in the stomach that increase the surface area of the stomach o Able to collapse and fold in—Changing in shape - Stomach has another layer of muscle in addition to the circular and longitudinal layers: Oblique muscles that contract at a diagonal - Stomach contracts and pushes everything towards the pylorus and pyloric sphincter- Where the most pressure is - Gastric pits: Depressions in the wall of the stomach - Mucosa cells are located on the surface and the gastric pits are lined with goblet cells (Both produce mucous) - Gastric glands: o Produce gastric juice that includes HCl, pepsinogen à pepsin, and mucous that is all secreted to the lumen of the stomach to act on the bolus to convert it into chyme • Small Intestine: - Also engages in propulsion to move food along like everywhere else in the digestive system - Major organ of chemical digestion - Review: o Mechanical digestion occurs in the mouth along with the start of chemical digestion of starches à Stomach where have chemical digestion of proteins - Carbohydrate chemical digestion begins again + protein digestion continues + start and finish lipid digestion + start and finish nucleic acid digestion - Therefore, all digestion finishes in the small intestine à Next have the absorption of the necessary nutrients and the left over unabsorbed components will go to the large intestine - Small intestine is 8-13 feet in length à 20 feet when one dies due to muscle relaxation - Runs from the pyloric sphincter à ileocecal valve where it meets the large intestine • Liver: - Largest gland of the body - Hematopancreatic ampulla connects to the liver - Primary function of the liver: o Process red blood cells à Breakdown red blood cells by taking off the heme and stripping off the globulin - Also produces bile that acts as an emulsifier - Lobes: o Right o Left o Caudate o Quadrate - Divided into right and left sides (Uneven) by the falciform ligament that is a type of mesentery (An attachment made of connective tissue) that suspends from the diaphragm - Liver secretions à duodenum through the common hepatic duct (Initially—Turns into the bile duct when it meets the fork where bile is coming from the gallbladder) o Branches so that it can go to all of the lobes of the liver • Gallbladder: - Bile is constantly produced by the liver since processing old red blood cells is a non-stop function à Bilirubin accumulated all the time - Bile is only needed when a meal is being digested in the small intestine - Therefore, the hepatopancreatic ampulla (sphincter) is closed when digestion isn’t occurring so the bile is backed up into the gallbladder - Bile from the gallbladder through the cystic duct meets the common hepatic duct at a fork where the common hepatic duct becomes the bile duct - Gallbladder also concentrates bile by taking some water out o Too concentrated bile à formation of gallstones that block the ducts so the gallbladder has to be excised • Pancreas: - 2 parts: a) Islets of Langerhans b) Acinar cells - Acinar cells produce pancreatic juice that travels through the pancreatic duct that joins the bile duct and empties into the duodenum it through the hepatopancreatic ampulla - CCK (cholecystokinin) stimulates the hepatopancreatic ampulla to open • Large Intestine: - Ileocecal valve connects the ileum of the small intestine to the cecum of the large intestine - Appendix: o Vestige that comes off of the cecum o Ancestors probably used the appendix for cellulose o Issues when it becomes inflamed due to blockages à Problem with seeds such as blueberry or strawberry seeds if they get in the plug o If it ruptures, it’s bad because it’s a storage area for bacteria - Ascending colon - Transverse colon - Descending colon - Sigmoid colon: S-shape curve - Terminates in the rectum: o Extends as the anal canal + external opening of the anus - Anus: o 2 sphincters: a) Internal anal sphincter: Compose of involuntary smooth muscle b) External anal sphincter: On the outside and is composed of skeletal muscle - Large intestine has rectal valves that incorporate with how the large intestine makes folds and bends - The folds separate flatulence (gas) from feces so that the gas and solids pass through differently - Gas is able to slip around and bend more easily than solids - The gas is produced by bacteria c) Discuss the composition and function of saliva. • 97-99% water • Electrolytes (Charged ions) • Salivary amylase: - Only breaks down long chains of starch à shorter carbohydrate chains that will be broken down in the small intestine • Mucin: - Lubricant associated with mucous that helps make things slippery • Lysosome and IgA: - Have immune function - Can start to breakdown bacteria consumed with food • Metabolic wastes: - Presence of urea or uric acid due to protein breakdown elsewhere in the body à Saliva is a way to get rid of it - Can apply to other metabolic wastes produced elsewhere in the body as well d) Describe the mechanism of deglutition. • Swallowing • Food is compacted into a bolus • Buccal phase: - Swallowing is a voluntary act - Tip of tongue is lifted up and pushes against the hard palate - Tongue contracts to push the food back to the oropharynx - Bolus stimulates tactile receptors in the oropharynx so that it switches to the pharyngeal-esophageal phase • Pharyngeal-esophageal phase: - Involuntary portion of deglutition - Tactile receptors send signals to the medulla and pons to cause peristalsis (What begins the involuntary portion) - Parasympathetic impulses-motor impulses- cause the smooth muscle movement to push food down the pharynx to the esophagus 8. List the cells of the stomach, and identify the functions of each. • At the base of the gastric pits there are gastric glands that are secretory • Goblet cells: - Produce mucous that helps protect the stomach - Protein digestion occurs in the stomach and the muscle is composed of protein so it is important to protect the stomach from the digestive juices • Mucosal cells: - Also secrete mucous to help protect the lining of the stomach from being degraded by proteases • Mucous neck cells: - Mucous producing cells - Mucous has changed to be more acidic - Act as the transition between the gastric glands and the gastric pits • Parietal cells: - Deeper into the gastric gland below the mucous neck cells are the parietal cells - Secrete HCl (pH ~2) - Secrete intrinsic factor o Required for the absorption of vitamin B12 in the intestines o Vitamin B12 functions in making red blood cells • Chief cells: - Deeper into the gastric gland below the parietal cells - Produce pepsinogen protein (Inactive form) à activated by HCl to become pepsin - Pepsin: Enzyme that digests proteins - Produce some lipase: Enzyme that breaks down fats (Relatively insignificantly though) • Enteroendocrine cells: - AKA G cells à G for gastric - Located at the very bottom of the gastric glands - Produce gastrin: o Hormone that affects a number of different target tissues including the stomach, small intestine, and large intestine o Increases stomach motility and stomach secretion 9. Explain the processes of gastric secretion and motility. • Gastric secretion has both neural and hormonal control • Cephalic (Reflex) Phase: - Occurs before food arrives into the stomach à Makes it a condition reflex - Stomach produces juice to prepare for when food arrives even when someone is thinking about food • Gastric Phase: - Occurs when food actually arrives at the stomach - Neural: As more and more food enters the stomach (Stretches), a signal is sent to the brain à parasympathetic fibers of the autonomic nervous system à For the secretion of acetylcholine à Stimulates HCl to be secreted by the parietal cells - Endocrine: When consuming food, it’s likely that there will be protein present + with the changes in pH à G cells are stimulated to secrete gastrin to promote the production of the other cells in the gastric glands • Intestinal Phase: - Related to food leaving the stomach - 2 components: a) Excitatory portion: o When chyme first starts leaving the stomach and arriving into the duodenum of the small intestine, more activity in the stomach is promoted b) Inhibitory portion: o As chyme continues to leave the stomach, there is a switch to the inhibitory phase where it’s time to shut down the process of pushing food out o Slowing down pushing food out into the duodenum helps the small intestine have more time to process the food o Specifically: Continued stretch of the small intestine by the chyme shuts off parasympathetic neural impulses to activate the sympathetic neural impulses to shut down movement of chyme into the small intestine 10. Discuss the protective mucosal barrier that prevents the stomach from digesting itself. • We do not digest our own stomachs • Bicarbonate-rich mucous creates a buffer and prevents acids coming in contact with the stomach tissue • Epithelial cells of the mucosa have impermeable/tight junctions so that the acid does not seep through • Gastric gland cells producing HCl have HCl-impermeable plasma membranes so that HCl can only go from the gland à gastric pit à stomach (One way) • Undifferentiated stem cells located at the junction of gastric pits and gastric glands function to replace cells in the stomach since some damage is inevitable • The epithelial stomach lining is replaced on average every 3-6 days 11. Differentiate the various regions of the small intestine. • Duodenum: - First 10 inches of the small intestine - Chyme leaves the stomach and passes through the pyloric sphincter 3 mL at a time à duodenum where secretions for the liver and pancreas are produced to help digest the 3 mL of chyme - Location of the hepatopancreatic ampulla: o Where secretions from the liver, pancreas, (and gallbladder) go through to enter into the duodenum • Jejunum: - Middle à ~ 8 feet long - Makes up most of the small intestine - Continues digestion and begins absorption • Ileum: - About the last 12 inches - By the time the chyme reaches the ileum, all of the digestion and absorption is mostly finished - Ileum prepares the leftover cyme for the large intestine 12. Identify the structural modifications on the wall of the small intestine, and discuss how each enhances the digestive process. • The small intestine has a very high surface area • As 3 mL passes through the tube of the small intestine, most of the small intestine is able to come in contact with the fluid (Specifically, 200 m of surface area contact)—Why small amounts should be released from the stomach • Plicae circulares: - Folds of the mucosa and submucosa in the lumen of the small intestine that increase the surface area + slow down the movement of chyme - Results in increased absorptive ability so that they can get into the blood vessels or lacteals • Villi: - Individual folds have finger-like projections of just the mucosa that extends off the fold à villi - Villi increase the surface area of the small intestine - Epithelial cells that make up the villi have modifications to their plasma membranes à Microvilli • Microvilli: - End up with a resemblance of a brush à Lining of the small intestine is therefore called the brush border ( - Chyme passes through all this material slowly and gets “brushed” as it passes through - Background: o 1-2 L of intestinal juice is produced everyday that is stimulated by the presence of acidic chyme o Intestinal juice has a slightly alkaline pH (~7.4-7.8) that helps neutralize the very acidic chyme + shuts off pepsin (Only functions at low pH’s) - Brush border in the intestinal juice will produce enzymes that will help breakdown carbohydrates and proteins 13. State the roles of bile and pancreatic juice in digestion, and identify their point of entry into the alimentary canal. • Bile: - Produced by the liver - Stored in the gallbladder - Acts as an emulsifier: o Form of mechanical digestion o Turns big globules of fat into little globules à Increases the surface area on the fat so lipid digestion enzymes can have better access o Therefore, bile is needed for the chemical digestion of fats to occur - Composition: o Mostly water o Bile salts: Substances that actually emulsify and increase the surface area of fats o Bile pigments: § Liver produces bilirubin as a result of processing red blood cells à contained in bile § Bilirubin à urobilinogen (Brown colored pigment) that turns feces brown o Cholesterol o Neutral fats: Don’t have a digestive role in bile o Phospholipids o Electrolytes - Bile that is stored in the gallbladder leaves through the cystic duct and meets the common hepatic duct coming from the liver à bile duct à hepatopancreatic ampulla à duodenum • Pancreatic juices: - Composition: o Mostly water o Enzymes for all classes of macromolecules produced by the acinar cells o Bicarbonate: High pH above 8 that is for neutralization of acidic contents coming from the stomach and making sure enzyme won’t be denatured when they enter the duodenum - Enters duodenum via hepatopancreatic ampulla 14. Describe the regulation of pancreatic juice and bile into the small intestine. • Bile: - Hepatopancreatic sphincter is closed when food is not being digested - Backs up the ducts into the gallbladder - Bile Release: o Fatty chyme entering the duodenum stimulates the production of cholecystokinin (CCK) o CCK causes the parasympathetic impulses to promote gallbladder contractions o CCK also relaxes the hepatopancreatic sphincter so that the bile can leave the gallbladder and go out through the ampulla into the small intestine • Pancreatic juice: - Secretin: o Intestinal hormone that is stimulated by high levels of HCl due to the highly acidic chyme that first enters the duodenum o Acts on pancreatic duct cells to stimulate bicarbonate production to neutralize the pH so that anything else in additional secretions aren’t destroyed - CCK stimulates the acinar cells and NOT the ducts cells to secrete enzymes - CCK also stimulates hepatopancreatic sphincter to open when food is digested à Allows pancreatic juice to enter the duodenum after traveling through the pancreatic duct and out through the hepatopancreatic ampulla - High amount of fat in chyme à Lipase produced - High amount of protein in chyme à Proteases produced - Parasympathetic nerve stimulation of the pancreas is overall what activates the acinar cell productivity - Emptying of the small intestine: o Distal end of the small intestine is where it attaches to the large intestine à At the ileocecal valve that regulates the emptying of the small intestine o Gastroileal reflex: § Stomach (gastro) + ileal (Ileum- last part of small intestine) § Action of the stomach due to stimulation of being filled increases the force of segmentation in the small intestine § Segmentation is due to a long reflex that sends a signal to the medulla to stimulate muscular contraction of segmentation § So o Gastrin: § Produced in the stomach § Relaxes the ileocecal valve to empty into the large intestine o It is not ideal to empty too much at once into the cecum of the large intestine (first part) à As a result, when pressure builds on the cecum that shuts/closes the ileocecal valve o Overall, pressure is what regulates the filling and emptying of the small intestine 15. List the pancreatic enzymes, and identify what each digests. • Proteases: Break down proteins a) Trypsin: - Pancreas produces trypsinogen (inactive form of trypsin) that passes through the hepatopancreatic ampulla à duodenum à interacts with secretions from the small intestine à ultimately activated to trypsin by enterokinase b) Carboxypeptidase: - Pancreas produces procarboxypeptidase à duodenum à activated to carboxypeptidase by trypsin c) Chymotrypsin: - Pancreas produces chymotrypsinogen à duodenum à activated to chymotrypsin by trypsin • Other enzymes: a) Pancreatic amylase: - Breaks down smaller carbohydrates - *Salivary amylase breaks down starch b) Lipase: - Class of enzymes that breaks down fats c) Nucleases: - Break down nucleic acids 16. Identify the structural modifications of the large intestine, and discuss how each is associated the digestive process. • Function of the large intestine is to compose and eliminate feces • Feces composition: - Undigested food residue, sloughed off epithelial cells from the distal portion of the small intestine and large intestine, bacteria, and some water - Large intestine reabsorb water à When chyme comes into the small intestine, a lot of water is pulled out + the right amount is needed for flow • Haustra: - Large intestine is divided in segments called haustra - Sac-like puckerings - Bands of smooth muscles called teniae coli cause the puckerings to give the large intestine its segmented appearance - Smooth muscle bands cause constriction and have neighboring pouches • Epiploic appendages: - Fat-like globule accumulations - It is not clear what their function is à They may have been of use to our ancestors like the vermiform appendix • Intestinal bacteria: - Humans and bacteria have a symbiotic relationship à Bacteria receive a meal from the portion of food we can’t break down - Cellulose is predominantly broken down by the bacteria through fermentation - Fermentation products: o H2S (Dimethyl sulfide) is an odorous gas o B vitamins o Vitamin K for clotting protein synthesis in the liver • Motility: - Throughout the day, we go through haustral contractions o Haustrum contracts à Squeezes the contents next to one haustrum so that things are slowly moved through the large intestine (AKA segmenting movements) o Haustral contractions occur about every 30 minutes o Movements are prompted by stretch à As material enters the cecum, it accumulates and causes the contraction leading to accumulation of material in the next portion that contracts and so on - About 3-4 times a day, the smooth gentle flow of the haustral contractions is interrupted by mass movements o Mass movements: Large peristaltic movements that push all the way through the large intestine o Gastric fillings signals the mass movements à Therefore, when the stomach is beginning to be filled with food, it is then time for the large intestine to get rid of the last meal - Overall: Haustral contractions + mass movements push material into the rectum that stimulates a defecation reflex 17. Describe the defecation process. • Mass movements push fecal material into the rectum, which causes stretch • Stretch receptors will stimulate parasympathetic nerve impulses stimulate the sigmoid colon and rectum, and the anal sphincters are inhibited • As a result, the external and internal anal sphincters are relaxed • External anal sphincters are under voluntary control • Valsalva’s maneuver assists emptying à Epiglottis goes over the glottis so attempted forceful exhalation helps push things out Nutrition and Metabolism and Chemical Digestion 18. List the nutrients necessary for life, and identify where they are obtained. • Nutrient - Latin origin that means “nourishing” - Nutrient: Any substance used by the body to promote growth, provide maintenance, or to be involved in repair • Water - Major nutrient needed by the body - 60% of volume of food is water - In order to be biologically active, things have to be in solution • Carbohydrate - Used directly to produce ATP to power processes - Can be used as building blocks - More taken in than needed à Stored as fat - Most comes from plants consumed - Can get carbohydrate from animals due to glycogen storage • Lipids - Mostly neutral fats (Triglycerides and triglycerols) - Most of the fat we get in our diets anymore is animal fat—Specifically, saturated fats that have shown to cause an increase in cholesterol - Plant fats are unsaturated and are healthier • Proteins - Complete protein: Animal sources à Have all 9 essential amino acids - Incomplete protein: Plant sources à Miss 1 or more of the essential amino acids • Vitamins - Not broken down to produce energy - Not used as building blocks - Function as coenzymes in the body - Allow us to be able to use everything else, or else it wouldn’t be possible for our bodies to build our own carbohydrates, produce ATP for energy, etc. - AKA vitamins are important due to indirect actions involved in metabolic pathways - Water soluble vitamins: o Cannot pass through plasma membrane so they can not accumulate and stored in the body o Ingest too much of a water soluble vitamin à Excreted from the body via urination • Fat soluble vitamins: - Can pass through plasma membrane à Can be stored inside the body and accumulate and could cause toxicity possibly • Minerals - Not used as fuel - Required as cofactors in metabolic processes - Examples: o Calcium: For building bone and muscle contraction o Phosphorous: For phosphates in producing energy 19. List the enzymes involved in chemical digestion, their location of action, and/or production, and the macromolecules they act on. • Overview - Breakdown of starches occurs in the mouth - Breakdown of protein occurs in the stomach - Breakdown = catabolic process - Food is taken in and broken down so that the nutrients can be absorbed into the small intestine - Nutrients are converted to things in the body such as protein àAA to build muscles - Polymers are broken down to monomers that are absorbed in the small intestine - Monomers are readily available for energy use or for building blocks for something in our body • Hydrolysis - Breakdown of polymers using water - Ex: Disaccharide à Monosaccharide - 1 molecule of water is used for every bond that is broken in a polymer • Carbohydrates - Polysaccharides (Long chains of carbohydrates) à Monosaccharides in a continuous process - Polysaccharides: Stored in plants as starches and stored in animals as glycogen - Cellulose: o Can’t be digested by humans o Bacteria in the large intestine break cellulose down for themselves - Polysaccharides are split into oligosaccharides (Intermediate with about 8 subunits) à Split eventually down to disaccharides (Sucrose, lactose, maltose) that are still not absorbable à Monosaccharides (Glucose, fructose, galactose) that are absorbable in the small intestine - Monosaccharides are used for energy or building blocks • Carbohydrate Digestion - Salivary amylase: o Digests starch in the mouth o Breaks polysaccharides into oligosaccharides o Secreted by salivary glands o Salivary amylase function stops when it reaches the stomach since the acidity is highly toxic to the enzyme - Pancreatic amylase: o Chyme from the stomach is neutralized by pancreatic secretions (Bicarbonate) o Neutralization allows pancreatic amylase to be secreted by the pancreas into the duodenum of the small intestine o Converts starch into oligosaccharides in the duodenum - Dexitrinase: o Secreted at the brush border of the small intestine o Digests oligosaccharides - Glucoamylase: o Secreted at the brush border of the small intestine o Digests oligosaccharides - Maltase: o Secreted at the brush border of the small intestine o Digests maltose (disaccharide) - Sucrase: o Secreted at the brush border of the small intestine o Digests sucrose (disaccharide) - Lactase: o Secreted at the brush border of the small intestine o Digests lactose (disaccharide) - Cellulose cannot be digested in the human body à Bacteria in the cecum and appendix of the large intestine that ferments cellulose o After the jejunum, digested products will not be absorbed à Fermentation by bacteria instead in the large intestine o Fermentation products: Vitamin B for blood production and vitamin K for clotting proteins • Proteins - Protein has multiple sources that is broken down by enzymes that do not distinguish where the protein as come from o Why there are mechanisms in preventing the stomach lining from being digested from protein digesting enzymes (And acid) - Dietary proteins - Intrinsic proteins: Examples o Enzymes o Receptor proteins o Channel proteins in mucosal cells • Protein Digestion - Begins in the stomach - Chief cells: o Produce pepsin in the stomach o Pepsin only works under very acidic conditions o Pepsin is inactivated when it reaches the duodenum of the small intestine where neutralization of chyme occurs - Babies: o Produce rennin o Rennin breaks down milk proteins (casein) o Adults do not produce much rennin at all o Rennin is also important in cheese production o Synthetic version: Rennilase - Pancreas: o Produces trypsin o Produces chymotrypsin o Produces carboxypeptidase (Also produced at the brush border) - Brush border: o Produces carboxypeptidase o Produces aminopeptidase à Cleaves amino acids off the end of polymer to produce a single amino acid o Produces dipeptidase à Dipeptide is the substrate for this enzyme that will produce 2 free amino acids as the produces that can be absorbed - List of enzymes work to create a cascade of breaking down long chains of amino acids: o Product of pepsin is the substrate for trypsin o Product of trypsin is the substrate for chymotrypsin o Product of chymotrypsin is the substrate for carboxypeptidase o Etc. • Lipid Digestion - Pancreas produces lipase that breaks down lipids - Lipase only works in the small intestine à Therefore, lipid digestion starts and finishes in the small intestine - Lipase requires bile: Emulsifier that allows lipase to act on the lipids - Breakdown of lipid à Free fatty acid and a MAG (monoacylglyceride- fatty acid + glycerol attached) as the products that are absorbed • Nucleic Acid Digestion - Pancreas: o Produces pancreatic nuclease o Breaks long RNA/DNA molecules and breaks them down to smaller big molecules - Brush border: o Produces nucleosidase o Produces phosphatase o Both break down smaller pieces of the RNA/DNA molecules à free nucleotides (A, T, C, G, U) - Uses of free nucleotides: o DNA replication à Use a steroid hormone to activate a DNA segment to give a product of mRNA that is needed to produce a new protein (mRNA is produced from the free nucleotides from the diet) - Nucleic acid digestion starts and finishes in the small intestine 20. Describe the process of absorption in the small intestine. • Almost all of absorption takes place in the jejunum of the small intestine • Exceptions: Bile salts are absorbed in the ileum and water is absorbed in the large intestine • Absorbable substances are actively transported into villi capillaries à liver • Portal system: - Specialized capillary bed between 2 veins • Hepatic portal system: - Branching capillary network in the liver where the absorbed substances from the small intestine are delivered to the liver • Absorbable substances can also pass into the villi lacteals through simple diffusion that ultimately end up in circulation by the lymph through first being dumped by the jugular vein - Energy isn’t required for absorbing substances into lacteals because of the mini valve system - Most of what enters lacteals is lipid-based (Fatty acids, MAG, etc.) à Therefore, micelles aid in the lipid substance absorption 21. Define metabolism, then define the contributing roles of anabolism, catabolism, oxidation and reduction. • Greek: Metaballein, Ismos • Metabolism has to do with the use of nutrients and the trade off of buildup (anabolic) and tear down (catabolic) processes • Carbohydrates, proteins, and lipids can all be converted into each other through reactions in the liver • This allows the body to manipulate what we’re eating to match our bodies’ needs (Ex: Protein needed but carbohydrate is consumed à Convert carbohydrate into protein) • Components have to be ingested (Lipids, protein, and carbohydrates cannot be made inside the body) • Anabolism - Buildup process - Monomers à polymers - More is taken in than needed, substances get stored • Metabolism: Catabolism - Break down process - Polymers à monomers (Smaller units in general) - When energy is needed 22. Identify the enzymes and coenzymes used for redox reactions. • REDOX reactions have to do with adding or removing hydrogen and oxygen + switching these around • Oxidation: Addition of oxygen or the removal of hydrogen à Energy is lost as a result • Reduction: Addition of hydrogen to a molecule à Energy is added as a result • REDOX Enzymes: - Dehydrogenases: o Remove hydrogen or add oxygen à Catalyze oxidation - Oxidases: o Remove hydrogen or add oxygen à Involved with oxidation too - Coenzymes: o Hydrogen acceptors o Ex: NAD+ and FADH à NADH and FADH2 23. Differentiate substrate-level and oxidative phosphorylation. • ATP Synthesis: Substrate-Level Phosphorylation - Direct transfer of a phosphate to ADP à ATP - Related to muscle activity: o Storage product in muscle that stores phosphate is creatine phosphate that gives the phosphate group to ADP à ATP - Not much energy is obtained this way • ATP Synthesis: Oxidative Phosphorylation - Oxygen is required to be present - Chemiosmotic process: o Hydrogen gradient is created that is based off of coenzyme molecules carrying hydrogen 24. Summarize the important events in the oxidation of glucose, including the phases of glycolysis, Kreb’s cycle and electron transport. • Carbohydrate Metabolism - Carbohydrate is the first source of energy the body goes for—Most easily converted into energy - Glycolysis: o Substrate-level phosphorylation o All carbohydrates à glucose à enter cells in glycolytic pathway - Glucose (6 carbons) à Enters a cell by facilitated diffusion à glucose is phosphorylated to glucose-6-phosphate (Irreversible step) à Concentration of glucose outside the cell is greater than inside so a gradient is maintained and glucose continues to come into the cell to be converted to glucose-6-phosphate - End products of glycolysis: o 2 pyruvic acid (3 carbons) o 2 NADH o Net gain of 2 ATP § 2 ATP are required for glycolysis to occur § 4 ATP is produced in the end § 4-2 = 2 ATP (Enough is produced to begin glycolysis again o If oxygen is present, oxidative phosphorylation occurs • Oxidative Phosphorylation - Pyruvic acid (product of glycolysis) à acetyl CoA in mitochondria where reaction also produces CO2 and NADH o Overall reaction: Pyruvic acid + NAD+ à Acetyl CoA + NADH + CO2 - Acetyl CoA enters the Krebs cycle: o Generates 2 CO2 o 2 NADH o 1 ATP (1 for each pyruvate) o 1 FADH2 - Reduced Kreb’s cycle coenzymes (NADH and FADH2) enter the electron transport chain - Hydrogen carried on the coenzymes are used to phosphorylate ADP - Electron transport chain produces H2O and 34 ATP as a result 25. Name and describe the process that results when there is an excessive of glucose, describe how this process is reversed when glucose becomes rare, and how glucose is made from non-carbohydrate molecules. • High ATP levels inhibit glycolysis • Glucose is converted to glycogen as a result for storage until it’s needed for energy • Glucose à glycogen via glycogenesis • Glucose is needed when blood glucose levels drop • Glycogen is broken down to glucose as a result via glycogenolysis and put back into circulation • Gluconeogenesis - Insufficient glucose availability (Not enough taken in or enough glycogen storage) prompts the conversion of glycerol and amino acids to glucose - Occurs in the liver 26. Describe the process by which lipids are oxidized for energy, stored when in excess and freed when needed. • Body likes to obtain energy from glucose first • The same pathways that glucose uses can be used to extract energy from other sources • Absorbed lipids broken down by plasma enzymes into glycerol and fatty acids • Glycerol: - Glycerol à Glyceraldehyde phosphate à pyruvic acid in glycolysis - Pyruvic acid can then enter the Kreb’s cycle à Production of 34 ATP • Fatty acids are broken down to acetic acid in the mitochondria o Acetic acid is able to fuse with coenzyme A à acetyl CoA o Acetyl CoA can enter the Kreb’s cycle and 34 ATP will be produced • More energy is obtained from a molecule of fat than carbohydrate à 1 triglyceride has 3 fatty acids on 1 glycerol • Excess Lipids o High ATP and glucose levels trigger the conversion of glycerol and fatty acids into triglycerides for storage in adipose tissue o Lipolysis: Revers triglyceride creation à Break down for release of fatty acids and glycerol 27. Describe protein metabolism. • Energy from protein can come from protein if we have to • Amino acids deaminated (Remove amine group of ammonia) • Deaminated molecules are converted to pyruvic acid or to Kreb’s cycle intermediates to generate energy in electron transport chain • Excess Proteins - High ATP levels cause pyruvic acid formed through deamination to be converted into glucose - Glucose à Glycogen via glycogenesis that is controlled by hormonal secretions - Hormones also control protein synthesis on ribosomes Temperature Regulation 28. Explain the concept of nutrient pools, and describe pathways for the inter- conversions of materials in these pools. • Food taken into the body is first broken down to the macromolecules’ corresponding counterparts of fatty acids, glycerol, amino acids, etc. that will be absorbed in the small intestine • Pool of carbohydrates and fats: - Carbohydrates à Fats ß - Primary source of energy - Absorbed glucose can immediately be metabolized for energy + CO2 as a waste product - Too much à Glycogen synthesis and fatty acid synthesis when glycogen stores are filled - Energy produced is used for building blocks in making plasma membranes for example and other structural components - Lipids can be converted into steroids that will be secreted by cells - Overall: Carbohydrates and lipids can be used for cell products, energy or storage • Pool of free amino acids: - Amino acids can be used to make proteins in our own bodies and make cellular secretions like hormones - Proteins can be deaminated à Carbohydrate derivative produced to be used to make energy - NH3 (Amine group off of ammonia) à Urea à elimination predominantly by the kidneys - Urea: Component of saliva due to the breakdown of proteins and is a way for urea to also be able to leave the body in addition through the kidneys • Conversions between free amino acids à carbohydrates à fats occur mostly in the liver ß ß - Overall: Amino acids, carbohydrates, fats are able to convert into each other to fulfill the needs of the body • Nutrient pool: Contains many nutrients that are available for the body to use after a meal has been digested and absorbed 29. Differentiate the absorptive and postabsorptive states (types of metabolic states), and discuss the hormonal and neural regulation of these conditions. • Absorptive: - Nutrients are being absorbed during or right after a meal is consumed - Nutrients are absorbed through the wall of the small intestine into the circulatory system à High levels of nutrients in the body - High levels of nutrients means that the absorptive state is predominantly a state of anabolic processes - Anabolic processes: Nutrients à storage products, cell secretions, cell structures, etc. • Post-absorptive: - State between meals and when the GI tract is empty - Reserves will be broken down that were formed during the absorptive state à Post-absorptive state is predominantly a state of catabolic processes - State functions maintain blood levels of nutrients- Especially blood glucose since blood glucose levels are low in the post-absorptive state - Special sensors are able to detect the amount of glucose in the body that indicates the shift from the absorptive to the post-absorptive state • Hormonal Control: a) Absorptive state: Insulin - Insulin is produced in the pancreatic Islets of Langerhans - When glucose levels are high in the blood, the pancreas is stimulated to release insulin - The presence of insulin stimulates cells to take up glucose via cellular diffusion - Insulin effects: o Increased oxidation of glucose for energy o Production of glycogen o Promotion of protein synthesis à Excess sugars available are animated à amino acids (Insulin is able to also reduce blood sugar levels by increasing protein synthesis) b) Post-absorptive state: Glucagon - Low nutrient levels in the blood stimulates the release of glucagon from the pancreas - Glucagon stimulates catabolic breakdown - Glucagon effects: o Promotion of glycogenolysis o Promotion of gluconeogenesis: Production of glucose from non- carbohydrate source o Promotion of lipolysis: Breakdown of lipids o Overall increasing blood glucose levels • Neural Control: a) Sympathetic stimulation: - Low blood glucose levels stimulate the autonomic nervous system to send a sympathetic signal to areas of storage (Especially adipose tissue that stores lipid which produces much more energy than carbohydrates) - Occurs in the post-absorptive state between meals b) Epinephrine: - Sympathetic impulses signal the medulla of the adrenal gland to secrete epinephrine that functions as a hormone - Epinephrine promotes glycogenolysis and lipolysis for energy production 30. Describe the role of the liver in cholesterol regulation. • Major function of the liver: Recycle red blood cells and cleanse the blood • Secondary function of the liver: Produces bile salts • Third function of the liver: Produce VLDL- A cholesterol carrying molecule • Cholesterol: - Lipid in origin - Not water soluble so it cannot be easily transported in the blood - Must bind to lipoprotein: A protein carrier molecule - Will not be broken down for energy - Component of cell structure à Synthesis of membranes around vesicles - Used to create steroid hormones • Again: Liver produces 85% of the cholesterol made in the body that will attach it to a carrier protein to create a VLDL (A lipoprotein) • The more lipid that is put on the lipoprotein, the lower the density • Therefore, VLDL (Very low density lipoprotein) has a lot of cholesterol
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