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Ken - Chapter 23
The Digestive System
| Question | Answer |
|---|---|
| What are the phases of the digestive process? | 1. Ingestion 2. Propulsion 3. Mechanical digestion 4. Chemical digestion 5. Absorption 6. Defecation |
| What does INGESTION refer to? | Taking food into the track |
| What does PROPULSION refer to? | Moving food through the canal; voluntary and involuntary |
| What does MECHANICAL DIGESTION refer to - and what body parts are involved? | Chewing, Mixing, and churning Teeth, Stomach, and Small intestine |
| What does CHEMICAL DIGESTION refer to - and where does it occur? | Catabolic breakdown by enzymes From the mouth to the small intestine |
| What does ABSORPTION refer to - and what is the major organ involved? | End products going through cells (of lumen) to blood and lymph Small intestine is major |
| What does DEFECATION refer to? | Elimination of indigestible items (feces) through the anus |
| What is mesentery - and what is the function? | Mesentery is a double layer of peritoneum: -Routes blood vessels, lymphatics and nerves -Holds organs in place and stores fat |
| Organs that lie posterior to the peritoneum are referred to as? | Retroperitoneal |
| What parts of the digestive system are retroperitoneal? | Duodenum, Pancreas, and parts of the large intestine |
| Organs that are surrounded by the peritoneum are referred to as? | Intraperitoneal |
| What parts of the digestive system are intraperitoneal? | Stomach, liver, and parts of the large and small intestine |
| What arteries are associated with splanchnic circulation? | Hepatic (liver), Splenic (spleen), and left gastric (stomach); also the inferior and superior mesenteric |
| What are 2 functions of hepatic portal circulation? | 1. Drains nutrient-rich blood from digestive organ (from splanchnic circulation) 2. Delivers blood to the liver for processing or storage |
| Name the tissue layers of the digestive tract, from the inside out. | 1. Mucosa (mucous membrane) 2. Submucosa 3. Muscularis externa 4. Serosa (ie. mesentery) |
| Identify what the following description is referring to: -middle layer of mucosa -made of loose connective tissue -capillary bed absorbs nutrients -has lymphoid follicles and lymphocytes that defend against bacteria; part of the MALT | Lamina Propria |
| Identify what the following description is referring to: -outer layer of mucosa -made of smooth muscle that produces local movements of mucosa -has grooves and ridges that increase surface area -increases efficiency of digestion & nutrient | Muscularis mucosae |
| Name the functions of the tongue: | -Reposition and mix food during chewing -Formation of bolus -Initiation of swallowing, speech and taste |
| What tongue muscles shape the tongue and form speech? | Intrinsic muscles |
| What tongue muscles position the tongue and manipulate the food? | Extrinsic muscles |
| What is the lingual frenulum? | The median fold of the mucosa that attaches the tongue to the floor of the mouth |
| What are the 4 types of lingual papillae? | 1. Filiform 2. Fungiform 3. Circumvallate (vallate) 4. Foliate |
| Which lingual papillae are white in color, small, rough, and provide friction; are the most abundant papillae on the human tongue, do not play a gustatory (taste) role and serve in sense of texture? | Filiform Papillae |
| Which lingual papillae are red in color, widely distributed/scattered, concentrated at the tips and sides of the tongue and have about 3 taste buds each? | Fungiform Papillae |
| Which lingual papillae are large, surrounded by a deep circular trench, in a V shape at the rear of the tongue, and although there are only about 7-12/tongue they contain up to 1/2 of all taste buds - about 250 each! | Circumvallate (vallate) Papillae |
| Which lingual papillae are weakly developed, lose taste buds around 2-3 years of age, and are about 2/3 of the way back from the tip of the tongue and on the sides of the tongue? | Foliate Papillae |
| Which lingual papillae help with taste in adults (there are 3)? | Filiform, Fungiform, and Circumvallate (vallate) |
| Which salivary glands are scattered in the oral mucosa? | Intrinsic Salivary glands (Buccal - inside of the cheeks, labial - inside of the lips, and lingual - inside the tongue) |
| What are the functions of saliva secretion? | -inhibits bacterial growth/cleanses the mouth (while awake) -moistens the mouth -dissolves food chemicals (allows us to taste what we eat) -aids in bolus formation -contains enzymes that begin the breakdown of starch (amylase) |
| What 2 types of cells secrete saliva? | Serous and mucous cells |
| What is saliva composed of? | Water (97-99.5%) Electrolytes (Na+, K+, Cl-, Phosphate, bicarbonate) Amylase (starch breakdown) Lingual lipase (fat breakdown) Mucin (glycoprotein) Metabolic wastes Lysozyme IgA (antibody) Defensins a cyanide compound that protects against micro |
| What is the pH of Saliva? | 6.8-7.0; slightly acidic |
| When are primary and permanent teeth (dentitions) formed? | By 21 years of age |
| How many deciduous teeth are there and when do they erupt? | There are 20 deciduous teeth ("baby"/"milk") teeth, that erupt between ages 6-24 months |
| What happens as permanent teeth develop, and about what age does this occur? | "baby" teeth (or "milk" teeth) fall out and their roots are reabsorbed; about 6-12 years of age |
| How many permanent teeth are there and when do they erupt? | There are 32 permanent teeth (16 on top/16 on bottom), all erupt by the end of adolescence (about age 13) except the third molars ("wisdom teeth") which erupt about age 17-25 if at all - they may become impacted (remain in jaw) and painful |
| Name and describe the 3 parts of the tooth structure. | 1. Crown - exposed area above gums (gingiva), covered by enamel - the hardest substance in the body, made of Ca2+ salts and hydroxyapetite crystals - about the thickness of a dime 2. Root - Portion embedded in the jawbone 3. Neck - Connects crown to roo |
| What are the gastric gland cell types? | 1. Mucous neck cells 2. Parietal cells 3. Chief cells 4. Endocrine cells |
| What do mucous neck cells secrete and what is the function of the secretion? | Secrete: Mucus Function: protect mucosa from HCl & enzymes (not well understood) |
| What do parietal cells secrete and what is the function of the secretion? | Secrete: HCl (say "hi") Function: activate pepsin & lingual lipase, helps liquify food, reduces dietary iron to useable form, destroys ingested pathogens Secrete: Intrinsic Factor Function: enables small intestine to absorb B12 |
| What do chief cells secrete and what is the function of the secretion? | Secrete: Pepsinogen (drink Pepsi) Function: is converted to Pepsin (by HCl), which digests protein Secrete: Gastric lipase Function: digests fat in the stomach |
| What do endocrine cells secrete and what is the function of the secretion? | Secrete:Serotonin Function:stimulate gastric motility Secrete:Histamine Function:stimulate HCl secretion Secrete:Gastrin Function:stimulate gastric glands to secrete HCl and enzymes Secrete:Somatostatin Function:inhibit gastric secretion and motili |
| What produces most gastric juice? | Glands in the fondus of the stomach |
| Describe the 2 secretions of parietal cells | 1. HCl - pH of 1.5-3.5 (very acidic), denatures protein in food (protein digestion starts here), activates pepsin, kills many bacteria 2. Intrinsic Factor - glycoprotein required for B12 absorption in small intestine |
| What cells secrete chemical messengers into the lamina propria (where is the lamina propria)? What are the 2 types of chemical messengers? | Endocrine cells secrete chemical messengers into the lamina propria (the middle layer of the mucosa layer of the alimentary canal): 1. Paracrines -Serotonin -Histamine 2. Hormones -Somatostatin -Gastin |
| What are the 3 mucosal barriers (protections of the stomach)? | 1. Mucous coat 2. Tight junctions 3. Epithelial cells |
| Which mucosal barrier is a layer of bicarbonate/rich mucus, that is thick and highly alkaline? | Mucous coat |
| Which mucosal barrier is between epithelial cells and prevents gastric juices from digesting connective tissue of the lamina propria? | Tight junctions |
| What mucosal barrier is replaced quickly - every 3-6 days - as damaged cells are replaced by stem cell division? | Epithelial cells |
| What are the digestive processes of the stomach? | -Physical digestion -Denaturation of proteins -Enzymatic digestion of proteins by pepsin (same chemical digestion as rennin on breast milk infants) -Secrete intrinsic factor, required for B12 absorption -Delivers chyme to small intestine |
| What would happen if the stomach did not produce intrinsic factor? | Intrinsic factor binds to B12 and the complex formed is absorbed, without intrinsic factor B12 cannot be absorbed, without B12 hemoglobin cannot be synthesized, which leads to pernicious anemia. |
| Identify the disease: -plaque calcifies to form calculus (tartar) -tartar disrupts the seal between the gingivae and the teeth -anaerobic bacteria infect gums -reversible:tartar is removed & good dental health habits -Red, swollen, bleeding gums | Gingivitis |
| Where are mucous cells found? | Mucous cells predominate in the cardiac and pyloric glands (of the stomach). In gastric glands, they are called mucous neck cells and are concentrated in the narrow neck of the gland. |
| Where are parietal cells found? | Parietal cells are found mostly in the upper half of gland - mostly in gastric glands, but are also found in pyloric glands. |
| Where are chief cells found? | Chief cells dominate the lower half of the gastric glands, but are absent from cardiac and pyloric glands. |
| Where are endocrine cells found? | Endocrine cells are especially concentrated in the lower end of a gland; they occur in all regions of the stomach, but are most abundant in the gastric and and pyloric glands. |
| What are the 2 types of gastric secretion regulation? | Neural and Hormonal |
| What are the 3 phases of stimulatory and inhibitory events that occur in gastric secretion regulation? | 1. Cephalic (reflex) phase 2. Gastric phase 3. Intestinal phase |
| Which phase of gastric secretion regulation occurs a few minutes prior to food entry? | The Cephalic (reflex) phase |
| Which phase of the gastric secretion regulation occurs 3-4 hours after food enters the stomach? | The Gastric phase |
| Which phase of the gastric secretion regulation results from sensory and mental inputs converging on the hypothalamus, which signals the medulla oblongata & Vagus nerve fibers stimulate the enteric nervous system (stomach) & stimulates gastric secretion? | The Cephalic (reflex) phase |
| Gastric Contractile Activity: | -Peristaltic waves move toward the pylorus at the rate of 3 per mintue -Base electrical rhythm (BER) set by pacemaker cells (cells of Cajal) -Distension and gastrin increase force of contraction |
| What is the major organ of digestion and absorption? | The small intestine |
| What is the largest part of the GI tract - and how long is it? | The small intestine, 2-4 m long (about 6') (from pyloric sphincter to ileocecal valve) |
| What are the 3 subdivisions of the Small intestine (in order) - and what is their anatomical position? | 1. Duodenum - retroperitoneal, next to stomach 2. Jejunum - attached posteriorly by mesentery, middle section of small intestine 3. Ileum - attached posteriorly by mesentery, distal, next to large intestine |
| Hepatic ducts->common hepatic duct->cystic duct->bile duct->pancreatic duct->hepatopancreatic ampulla, ends @ the major duodenal papilla, controlled by the heptopancreatic sphincter which regulates the passage of bile & pancreatic juice into what? | The duodenum (of the small intestine) |
| What structural modification of the small intestine are permanent folds, about 1 cm deep, and force chyme to slowly spiral through the lumen? | Circular folds |
| What structural modification of the small intestine is about 0.5-1 mm high with finger-like extensions and covered with 2 types of epithelial cells: simple columnar absorptive cells (enterocytes) and mucus-secreting goblet cells; also has lacteal at core. | Villi projections |
| What do the prominent Duodenal (Brunner's) glands in the submucosa of the duodenum do? | Secrete an abundance of bicarbonate-rich (alkaline) mucus, which neutralizes stomach acid (chyme) and shields the mucosa from its erosive effects. |
| What would the result be of a compromised mucosal defense in the stomach, esophagus, or duodenum? | A peptic ulcer; caused by erosion from pepsin and HCl |
| What protects the distal part of the small intestine (the ileum) against bacteria? | Peyer's patches (lymphatic nodules) |
| Innumerable tiny cylinders (about 2mm long by 1 mm wide) that have a hexagonal structure and are the functional units on the interior of the liver are called? | Liver lobules (or hepatic lobules) |
| What is a liver lobule composed of and what is it's function? | A liver lobule consists of: -a longitudinal central vein -plates of hepatocytes (liver cells) Function: filter and process nutrient-rich blood |
| What are the functions of hepatocytes? | -Process blood-borne nutrients -Store fat-soluable vitamins (A,D,E,K) -Perform detoxification -Produce about 900 ml (almost 1 L) of bile/day |
| Bile is a yellow-green, alkaline solution containing: | -Bile salts -Bilirubin -Cholesterol -neutral fats -phospholipids -electrolytes |
| What are cholesterol derivatives that function in fat emulsification (breakdown) and absorption? | Bile salts |
| What is bilirubin? | A pigment formed by heme (the breakdown of RBC's) |
| What would be the result of an increase in cholesterol or a decrease of salts in bile - and what would treatment include? | Gallstones, causing right thoracic region pain. Treatment includes drugs or ultrasound to break up the stones; or removal of gallbladder, if necessary. |
| What are pancreatic juices composed of? | Pancreatic juice is a watery alkaline solution composed of: -Electrolytes -Enzymes (secreted in active form, but require ions or bile for optimal activity) -Proteases (secreted in inactive form; help prevent pancreas from digesting itself) |
| What are the enzymes secreted by the pancreas - and what are their functions? | amylase (digests starch), lipase (digests fats), ribonuclease (digests RNA) and deoxyribonuclease (digests DNA) |
| What is the primary electrolyte secreted by the pancreas - and what is it's function? | Bicarbonate - neutralizes HCl |
| What is the the pH of pancreatic juice - and what is it's function? | pH of 8 (alkaline), neutralizes chyme |
| What are the proteases secreted by the pancreas - and what are their functions? | Tripsinogen - becomes trypsin, which digests protein Chymotrypinogen - becomes chymotrypsin, which digests protein Procarboxypetidase - becomes carboxypeptidase, which hydrolyzes the terminal amino acid from the carboxyl (-COOH) end of small peptides |
| What activates Trypsinogen to trypsin? | The brush border enzyme enteropeptidase |
| What activates procarboxypeptidase and chymotrypsinogen? | Trypsin |
| Trypsin is an autocatalytic - it converts trypsinogen into more trypsin, what is this an example of? | A positive feedback loop |
| What is gallbladder contraction stimulated by? | Cholecystokinin (CCK) from intestinal cells exposed to proteins and fat in chyme (also, vagal stimulation - a minor stimulus) |
| What does Cholecystokinin (CCK) cause to relax? | The hepatopancreatic sphincter (causes discharge of bile into duodenum) |
| What does Cholecystokinin (CCK) stimulate to secrete enzyme-rich pancreatic juice? | The pancreatic acini |
| What does secretin stimulate to secrete an abundant sodium bicarbonate solution that flushes the enzymes from the pancreas into the duodenum? | The ducts of both the liver and pancreas |
| What triggers the release of secretin in the pancreas? | HCl arriving from the stomach |
| What are the unique features of the large intestine? | Teniae coli - 3 bands of longitudinal smooth muscle in the muscularis Haustra - Pocket-like sacs caused by the tone of the teniae coli Epiploic appendages - Fat-filled pouches of visceral peritoneum |
| What is bacteria that enters through the small intestine or anus and colonize in the colon referred to? | Bacterial Flora |
| What are the benefits of bacterial flora - what are the less desirable side effects? | Benefits: ferment indigestible carbohydrates and synthesize B complex vitamins and vitamin K (a fat soluble vitamin important for adequate blood clotting) Less desirable side effects: release of irritating acids and gases |
| What are enzymes that digest proteins called? | Proteases |
| What is the enzyme that digests protein in the stomach called? | Pepsin |
| What are the brush border enzymes that digest proteins? | Aminopeptidases Carboxypeptidases Dipeptidases |
| How are amino acids transported in the digestive system? | They leave the cell by facilitated diffusion, enter the the capillaries of the villus, and are carried away in the hepatic portal circulation (coupled to active transport of Na+) |
| Where are vitamin K and B vitamins from bacterial metabolism absorbed? | In the large intestine |
| Where does most electrolyte absorption occur? | Along the length of the small intestine |
| Where are iron and calcium absorbed? | In the duodenum |
| What are Sodium ions co-transported with, for absorption? | Na+ is coupled with active absorption of glucose and amino acids |
| What does ionic iron bind to - and where is it stored? | Iron, if absorbed, binds to ferritin and is stored in mucosal cells |
| How are potassium ions absorbed? | K+ absorbed by simple diffusion; the K+ concentration of the chyme rises as water is absorbed from it, creating a gradient favorable to K+ absorption (osmotic gradient) |
| How is calcium absorbed in the duodenum? | Parathyroid hormone is secreted in by a drop in blood ca2+ level, which stimulates the kidneys to synthesize vit D. Vit D affects the absorptive cells of the duodenum by: Increasing ca2+ channels, amt of calbindin in the cytoplasm, and ca2+ ATPase pumps |
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nolanc
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