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Digestive System
Wk 10 Ch 23
| Question | Answer |
|---|---|
| What enzyme is produced by cells in the duodenum wall, is secreted from duodenum's glands, the crypts of Lieberkühn, when ingested food enters duodenum from the stomach and turns trypsinogen (a zymogen) to trypsin, activating pancreatic digestive enzymes? | Enteropeptidase (aka enterokinase) |
| What digestive organ has microvilli that constitute the brush border that has enzymes for the absorption phase of digestion? | small intestine |
| What are gastric folds? | rugae |
| Deep folds of the mucosa and submucosa that extend completely or partially around the circumference of the small intestine? | circular folds |
| Structure that suspends the small intestine from the posterior body wall | mesentery |
| Conduit for both air and food | pharynx |
| Three structures continuous with and representing modifications of the peritoneum | greater omentum, lesser omentum and mesentery |
| Sacculations of the large intestine | haustra |
| Valve at the junction of the small and large intestines | ileocecal valve |
| Primary region of food and water absorption | small intestine |
| Absorbs water and forms feces | large intestine |
| Wormlike sac that outpockets from the cecum | appendix |
| Structure attached to the lesser curvature of the stomach | lesser omentum |
| Valve controlling food movement from the stomach into the duodenum | pyloric valve |
| Location of the hepatopancreatic sphincter through which pancreatic secretions and bile pass | small intestine |
| Serous lining of the abdominal cavity wall | parietal peritoneum |
| Principal site for the synthesis of vitamin K by microorganisms | large intestine |
| visible portion of the tooth in situ | clinical crown |
| produce(s) mucus; found in the submucosa of the small intestine | duodenal glands |
| produce(s) a product containing amylase that begins starch breakdown in the mouth | salivary glands |
| produce(s) a whole spectrum of enzymes and an alkaline fluid that is secreted into the duodenum | pancreas |
| produce(s) bile that it secretes into the duodenum via the bile duct | liver |
| produce(s) HCI and pepsinogen | gastric glands |
| found in the mucosa of the small intestine; produce(s) intestinal juice | intestinal crypts |
| Which of the salivary glands produces a secretion that is mainly serous? | parotid |
| The pancreas has two major populations of secretory cells-those in the islets and the acinar cells. Which population serves the digestive process? The ________ cells. | acinar |
| What are the 2 digestive tract regulatory mechanism rules that act to control luminal conditions so that digestion and absorption can occur there as effectively as possible. | Digestive activity is provoked by a range of mechanical and chemical stimuli; Controls of digestive activity are both extrinsic and intrinsic. |
| What are the two kinds of reflex activity that occur? | short and long |
| Which reflexes are mediated entirely by the local (enteric) plexuses (the so-called gut brain) in response to GI tract stimuli. | Short |
| Which reflexes are initiated by stimuli arising inside or outside the GI tract and involve CNS centers and extrinsic autonomic nerves | Long |
| What is a double layer of peritoneum—a sheet of two serous membranes fused back to back—that extends to the digestive organs from the body wall? | mesentary |
| What are some parts of the small intestine and other organs that adhere to the dorsal abdominal wall lose their mesentery and come to lie posterior to the peritoneum referred to as? | retroperitoneal organs |
| What are digestive organs (like the stomach) that keep their mesentery and remain in the peritoneal cavity called? | intraperitoneal or peritoneal organs |
| What is the most common cause of Peritonitis? | ruptured or burst appendix |
| What includes those arteries that branch off the abdominal aorta to serve the digestive organs and the hepatic portal circulation? | the splanchnic circulation |
| What are the walls of the alimentary canal have the same four basic layers, or tunics called? | mucosa, submucosa, muscularis externa, and serosa |
| What is the moist epithelial innermost layer that lines the alimentary canal lumen from mouth to anus? | mucosa |
| Which layer's major functions are (1) secretion of mucus, digestive enzymes, and hormones, (2) absorption of the end products of digestion into the blood, and (3) protection against infectious disease | mucosa |
| What 3 layers does the typical digestive mucosa consists of? | (1) a lining epithelium, (2) a lamina propria, and (3) a muscularis mucosae. |
| Which epithelium is a simple columnar epithelium rich in mucus-secreting goblet cells? | digestive mucosa |
| What underlies the epithelium, is loose areolar connective tissue and whose capillaries nourish the epithelium and absorb digested nutrients? | lamina propria |
| Particularly large collections of lymphoid follicles occur within? | the pharynx (as the tonsils) and in the appendix. |
| What is external to the lamina propria, a scant layer of smooth muscle cells that produces local movements of the mucosa. | the muscularis mucosae |
| twitching of this layer dislodges food particles that have adhered to the mucosa. In the small intestine, it throws the mucosa into a series of small folds that immensely increase its surface area. | the muscularis mucosae |
| What layer is just external to the mucosa, is a moderately dense connective tissue containing blood and lymphatic vessels, lymphoid follicles, and nerve fibers. | submucosa |
| What layer is just deep to the submucosa, is responsible for segmentation and peristalsis. It typically has an inner circular layer and an outer longitudinal layer of smooth muscle cells | the muscularis externa, also simply called the muscularis. |
| In several places along the tract, the circular layer of what thickens, forming sphincters that act as valves to prevent backflow and control food passage from one organ to the next. | the muscularis externa |
| What is the protective outermost layer of the intraperitoneal organs, is the visceral peritoneum. It is formed of areolar connective tissue covered with mesothelium, a single layer of squamous epithelial cells. | The serosa |
| Where is the serosa replaced by an adventitia? | In the esophagus, which is located in the thoracic instead of the abdominopelvic cavity, |
| Which semiautonomous neurons constitute the bulk of the two major intrinsic nerve plexuses (ganglia interconnected by unmyelinated fiber tracts) found in the walls of the alimentary canal: the submucosal and myenteric nerve plexuses | enteric neurons |
| What occupies the submucosa, includes sensory as well as motor neurons, and chiefly regulates the activity of glands and smooth muscle in the mucosa? | submucosal nerve plexus |
| What lies between the circular and longitudinal muscle layers of the muscularis externa. | large myenteric nerve plexus |
| Enteric neurons of this plexus provide the major nerve supply to the GI tract wall and control GI tract motility. | large myenteric nerve plexus |
| the enteric nervous system contains how many neurons? | over 100 million neurons |
| The mouth, a mucosa-lined cavity, is also called what? | the oral cavity, or buccal cavity |
| the oral cavity is continuous with? | the oropharynx |
| The walls of the mouth are lined with what type of epithelium? | stratified squamous epithelium |
| How does the oral mucosa responds to injury? | by producing antimicrobial peptides called defensins |
| Since Saliva is largely water—97 to 99.5%, it is considered to be what? | hypo-osmotic |
| Saliva solutes include electrolytes (Na+, K+, Cl–, PO4–, and HCO3–); the digestive enzyme salivary amylase; the proteins mucin (mu′sin), lysozyme, and IgA; and metabolic wastes (urea and uric acid). | True |
| Secretions of the intrinsic salivary glands contain a fat-digesting enzyme that is optimally active at an acid pH, known as what? | lingual lipase |
| What is the average output of saliva? | 1000–1500 ml per day. |
| Salivation is controlled primarily by? | the parasympathetic division of the autonomic nervous system. |
| When we ingest food, chemoreceptors and mechanoreceptors in the mouth send signals to where? | the salivatory nuclei in the brain stem (pons and medulla). |
| As a result of salivation, what activity increases and sends impulses via motor fibers in the facial (VII) and glossopharyngeal (IX) nerves triggering a dramatically increased output of watery (serous), enzyme-rich saliva? | parasympathetic nervous system |
| What are The chemoreceptors activated most strongly by? | acidic substances such as vinegar and citrus juice |
| What is this? 2I, 1C, 2M (upper jaw) ______________________ x 2 (20 teeth) 2I, 1C, 2M (lower jaw) | dental formula for primary dentition |
| What is this? 2I, 1C, 2PM, 3M (upper jaw) ______________________ x 2 (32 teeth) 2I, 1C, 2PM, 3M (lower jaw) | dental formula for permanent dentition |
| What is the exposed part of the tooth above the gingiva | The enamel-covered crown |
| The outer surface of the tooth's root is covered by what material that is a calcified connective tissue, which attaches the tooth to the thin periodontal ligament? | cementum |
| The periodontal ligament anchors the tooth in the bony alveolus of the jaw, forming a fibrous joint called what? | a gomphosis |
| What material underlies the enamel cap and forms the bulk of a tooth? | dentin |
| What is at the proximal end of each root canal that allows blood vessels, nerves, and other structures to enter the pulp cavity? | an apical foramen |
| What are 2 common passageways for food, air and fluids? | oropharynx and laryngopharynx |
| The pharyngeal wall mucosa contains what type of epithelium? | a friction-resistant stratified squamous epithelium well supplied with mucus-producing glands. |
| Where does food go after it moves through the laryngopharynx, as the epiglottis closes off the larynx to food entry. | into the esophagus |
| What phase of deglutition occurs in the mouth and is voluntary. | The buccal phase |
| What phase of deglutition is involuntary and is controlled by the swallowing center located in the brain stem (medulla and lower pons). | pharyngeal-esophageal phase |
| Motor impulses from the swallowing center are transmitted via various cranial nerves, most importantly which nerves, to the muscles of the pharynx and esophagus. | the vagus nerves |
| The stomach mucosa is comprised of what type of epithelium composed entirely of goblet cells, which produce a protective 2-layer coat of alkaline mucus in which the surface layer consists of viscous mucus that traps a layer of bicarbonate-rich fluid | a simple columnar epithelium |
| What is the stomach's smooth lining dotted with, which lead into the gastric glands that produce the stomach secretion called gastric juice. | millions of deep gastric pits |
| What part of the stomach does most chemical digestion occurs? | the fundus and body |
| What are the 4 glands in the stomach fundus and body? | mucous neck cells-produce thin, mucus Parietal cells-secrete HCl and intrinsic factor Chief cells-produce pepsinogen Enteroendocrine cells-release histamine and serotonin, act locally as paracrines. somatostatin, gastrin |
| What 4 factors create the barrier to protect the stomach from digesting itself? | A thick coating of bicarbonate-rich mucus is built up on the stomach wall; tight junctions that prevent gastric juice from leaking into underlying tissue layers; Damaged epithelial mucosal cells are shed and quickly replaced. |
| What are gastric ulcers? | erosions of the stomach wall. |
| What type of digestion is initiated in the stomach and is the only significant type of enzymatic digestion that occurs there. | Protein digestion |
| Dietary proteins are denatured by what that is produced by stomach glands in preparation for enzymatic digestion. | HCl |
| What is the most important protein-digesting enzyme produced by the gastric mucosa? | pepsin |
| What is secreted in the stomachs of infants, an enzyme that acts on milk protein | rennin |
| What is required for intestinal absorption of vitamin B12, needed to produce mature erythrocytes; in its absence, pernicious anemia results. | Intrinsic factor |
| Gastric secretion is controlled by both what 2 types of mechanisms. | neural and hormonal |
| Nervous control is provided by what 2 types of reflexes? | long (vagus nerve–mediated) and short (local enteric) nerve reflexes |
| What are the the three phases of gastric secretion called? | the cephalic, gastric, and intestinal phases |
| Inputs from activated olfactory receptors and taste buds are relayed to where, which in turn stimulates the vagal nuclei of the medulla oblongata, causing motor impulses to be transmitted via the vagus nerves to parasympathetic enteric ganglia. | the hypothalamus, |
| The enhanced secretory activity that results when we see or think of food is what kind of reflex and occurs only when we like or want the food? | conditioned reflex |
| local neural and hormonal mechanisms initiate which phase, which lasts three to four hours and provides about two-thirds of the gastric juice released. The most important stimuli are distension, peptides, and low acidity. | the gastric phase |
| What activates stretch receptors and initiates both local (myenteric) reflexes and the long vagovagal reflexes. | Stomach distension |
| both local (myenteric) reflexes and the long vagovagal reflexes lead to acetylcholine (ACh) release, which in turn stimulates the output of what? | more gastric juice |
| Though neural influences initiated by stomach distension are important, what hormone probably plays a greater role in stimulating stomach gland secretion during the gastric phase. | gastrin |
| Chemical stimuli provided by partially digested proteins, caffeine, and rising pH directly activate gastrin-secreting enteroendocrine cells called what in the stomach antrum. | G cells |
| Although gastrin also stimulates the release of enzymes, its main target is what, which it prods to spew out even more HCl | HCl-secreting parietal cells |
| When protein foods are in the stomach, the pH of the gastric contents generally rises because proteins act as buffers to do what? | tie up H+. |
| The more protein in the meal, the greater the amount of _________and ______ released. | gastrin and HCl |
| As proteins are digested, the gastric contents gradually become more acidic, which again inhibits what? | the gastrin-secreting cells. |
| Emotional upsets, fear, anxiety, or anything that triggers the fight-or-flight response inhibits ___________because (during such times) the sympathetic division overrides parasympathetic controls of digestion. | gastric secretion |
| HCl secretion is stimulated by three chemicals, all of which work through what kind of systems? | second-messenger systems |
| ACh released by parasympathetic nerve fibers and gastrin secreted by G cells bring about their effects by increasing levels of what? | intracellular Ca2+ |
| What is released by the so-called enterochromaffin-like (ECL) cells in response to gastrin (and to a lesser extent by ACh) acts through cyclic AMP (cAMP) | Histamine, |
| What is the phenomenon called the alkaline tide due to? | blood draining from the stomach being more alkaline than the blood serving it. |
| What are the 2 components of the intestinal phase of gastric secretion? | one excitatory and the other inhibitory |
| What is set into motion as partially digested food fills the initial part (duodenum) of the small intestine. | The excitatory aspect |
| the inhibitory component is triggered in the form of what reflex? | the enterogastric reflex |
| What trio of reflexes (1) inhibit the vagal nuclei in the medulla, (2) inhibit local reflexes, and (3) activate sympathetic fibers that cause the pyloric sphincter to tighten and prevent further food entry into the small intestine. | The enterogastric reflex |
| What comprise the intestinal hormones, collectively called enterogastrones? | secretin; cholecystokinin (CCK); and vasoactive intestinal peptide (VIP). |
| The pressure of the stomach remains constant until how much food has been ingested? | 1.5 L |
| The relatively unchanging pressure in a filling stomach is due to what? | (1) the reflex-mediated receptive relaxation of the stomach muscle and (2) the plasticity of visceral smooth muscle. |
| What happens to smooth muscle in the stomach fundus and body both in anticipation of and in response to food movement through the esophagus and into the stomach. | Receptive relaxation |
| What is coordinated by the swallowing center of the brain stem and mediated by the vagus nerves acting on serotonin and NO-releasing enteric neurons. | receptive relaxation |
| What is the intrinsic ability of visceral smooth muscle to exhibit the stress-relaxation response, that is, to be stretched without greatly increasing its tension and contracting expulsively. | Plasticity |
| What is emesis? | vomiting |
| The small intestine relies on the secretions from what 2 organs to digest? | pancreas and liver |
| What part of the digestive system does most absorption occur? | small intestine |
| What are the 3 subdivisions of the small intestine? | duodenum; jejunum and ileum |
| Of the duodenum, jejunum and ileum, which are retroperitoneal and which are intraperitoneal? | duodenum-retraperitoneal jejunum, ileum - intraperitoneal |
| What two ducts unite in the wall of the duodenum in a bulblike point called the hepatopancreatic ampulla? | The bile duct, delivering bile from the liver, and the main pancreatic duct, carrying pancreatic juice from the pancreas |
| The entry of bile and pancreatic juice is controlled by a muscular valve called the what? | hepatopancreatic sphincter, or sphincter of Oddi. |
| What extends from the duodenum to the ileum. | jejunum about 2.5 m (8 ft) long, |
| What hangs in sausagelike coils in the central and lower part of the abdominal cavity, suspended from the posterior abdominal wall by the fan-shaped mesentery | The jejunum and ileum |
| Where is the arterial supply for the small intestine primarily from? | the superior mesenteric artery . |
| The small intestinal wall has three structural modifications—plicae circulares, villi, and microvilli—that do what? | amplify its absorptive surface enormously (by a factor of more than 600 times). |
| What is a lacteal and what is its function? | A lymphatic capillary that receives some of the fatty materials absorbed from the intestine. |
| Between the villi of the small intestine, the mucosa is studded with pits that lead into tubular intestinal glands called what? | intestinal crypts, or crypts of Lieberkühn |
| Where are specialized secretory cells called Paneth cells, which fortify the small intestine’s defenses by releasing antimicrobial agents such as defensins and lysozyme, an antibacterial enzyme. | Deep in the crypts of the small intestine |
| What increase in abundance toward the end of the small intestine, reflecting the fact that this region of the small intestine contains huge numbers of bacteria that must be prevented from entering the bloodstream. | Peyer’s patches |
| Elaborate mucus-secreting ___________ glands are found in the submucosa of the duodenum only. | duodenal (Brunner’s) |
| What type of glands (see Figure 23.21b) produce an alkaline mucus that helps neutralize the acidic chyme moving in from the stomach. | duodenal glands |
| Which 2 organs are accessory organs associated with the small intestine. | The liver and gallbladder |
| What is the liver's digestive function? | to produce bile for export to the duodenum |
| What is the largest organ in the body weighing 3 lbs? | liver |
| The liver is composed of sesame seed–sized structural and functional units called what? | liver lobules |
| Each lobule is a roughly hexagonal (six-sided) structure consisting of plates of liver cells, aka | hepatocytes |
| Between the hepatocyte plates are enlarged, leaky capillaries, known as what? | liver sinusoids. |
| The liver's hepatic macrophages, which remove debris such as bacteria and worn-out blood cells from the blood as it flows past are called what? | Kupffer cells |
| What part of the liver has large amounts of both rough and smooth ER, Golgi apparatuses, peroxisomes, and mitochondria. | The liver's hepatocytes |
| The chief bile pigment is ______a waste product of the heme of hemoglobin formed during the breakdown of worn-out erythrocytes | bilirubin |
| What is done with the globin and iron parts of hemoglobin? | They are saved and recycled |
| What is absorbed from the blood by the liver cells, excreted into bile, and metabolized in the small intestine by resident bacteria. | bilirubin |
| What gives feces a brown color | stercobilin |
| The liver produces how much bile daily? | 500 to 1000 ml |
| What is released by intestinal cells exposed to fatty chyme, also stimulates liver cells to secrete bile. | Secretin |
| What is the major stimulus for gallbladder contraction? | cholecystokinin (CCK), an intestinal hormone released to the blood when acidic, fatty chyme enters the duodenum |
| Besides causing the gallbladder to contract, CCK stimulates ______and ___________ so that bile and pancreatic juice can enter the duodenum. | secretion of pancreatic juice, and relaxes the hepatopancreatic sphincter |
| Too much cholesterol or too few bile salts leads to what homeostatic imbalance? | cholesterol crystallization, forming gallstones, or biliary calculi |
| What can be caused by bile duct blockage preventing both bile salts and bile pigments from entering the intestine. | yellow bile pigments accumulate in blood and eventually are deposited in the skin, causing it to become yellow, or jaundiced. |
| The pancreas produces enzymes that break down all categories of foodstuffs, which is then delivered to the duodenum. This exocrine product is called what? | pancreatic juice |
| Within the pancreas are clusters of secretory cells surrounding ducts called what? | acini |
| Acini cells are full of rough endoplasmic reticulum and exhibit deeply staining _________ granules containing the digestive enzymes they manufacture. | zymogen |
| Scattered amid the acini are mini-endocrine glands that release insulin and glucagon, hormones that play an important role in carbohydrate metabolism, as well as several other hormones called what? | pancreatic islets (islets of Langerhans) |
| Pancreatic juice consists mainly of water, and contains enzymes and electrolytes (primarily bicarbonate ions) | True |
| Which cells produce the enzyme-rich component of pancreatic juice. | The acinar cells |
| Which cells release the bicarbonate ions that make it alkaline (about pH 8). | The epithelial cells lining the smallest pancreatic ducts |
| Like pepsin of the stomach, pancreatic proteases (protein-digesting enzymes) are produced and released in inactive forms, which are activated in the duodenum, where they do their work. | True |
| Secretion of pancreatic juice is regulated both by __________and by the __________ | hormones; parasympathetic nervous system |
| What kind of stimulation causes release of pancreatic juice primarily during the cephalic and gastric phases of gastric secretion. | Vagal stimulation |
| What initiates the gastroileal reflex , a long reflex that enhances the force of segmentation in the ileum | Enhanced activity of the stomach |
| Injury to the intestinal wall by severe stretching, some bacterial infections, or mechanical trauma may lead to a total cessation of small intestine motility, a phenomenon called what? | intestino-intestinal reflex |
| Which digestive organ exhibits three features not seen elsewhere—teniae coli, haustra, and epiploic appendages | The large intestine |
| Which intestine has the following subdivisions: cecum, appendix, colon, rectum, and anal canal | The large intestine |
| In the large intestine, what contains masses of lymphoid tissue, and as part of MALT, it plays an important role in body immunity. | The appendix |
| What results from a blockage (often by feces) that traps infectious bacteria in its lumen. | appendicitis |
| Bacteria from the cecum and bacteria that enter the GI tract via the anus, constitute what? | the bacterial flora of the large intestine, over 700 species of them. |
| The movements most seen in the colon are ________slow segmenting movements lasting about one minute that occur every 30 minutes or so. | haustral contractions |
| What type of contractions, which occur mainly in the transverse and descending colon, reflect local controls of smooth muscle within the walls of the individual haustra. | Haustral contractions |
| What condition occurs when diet lacks bulk, the colon narrows and its contractions become more powerful, increasing the pressure on its walls, promoting formation of small herniations of mucosa thru colon walls, most commonly occurs in the sigmoid colon? | diverticula |
| In about what percent of cases, diverticulosis progresses to diverticulitis, in which the diverticula become inflamed and may rupture, leaking feces into the peritoneal cavity, which can be life threatening. | 20% |
| The enzymatic breakdown of any type of food molecule is called what because it involves addition of a water molecule to each molecular bond to be broken. | hydrolysis |
| The monosaccharides glucose and galactose, liberated by the breakdown of starch and disaccharides, are shuttled by _______ into the epithelial cells by common protein carriers. | secondary active transport (cotransport with Na+) |
| How does fructose moves by? | entirely by facilitated diffusion. |
| What are collections of fatty elements clustered together with bile salts in such a way that the polar (hydrophilic) ends of the molecules face the water and the nonpolar portions form the core. | Micelles |
| the free fatty acids and monoglycerides are resynthesized into triglycerides which are then combined with phospholipids and cholesterol, and coated with a “skin” of proteins to form water-soluble lipoprotein droplets called what? | chylomicrons. |
| While in the bloodstream, the triglycerides of the chylomicrons are hydrolyzed to free fatty acids and glycerol by an enzyme associated with the capillary endothelium called what? | lipoprotein lipase |
| The small intestine absorbs dietary vitamins,and the large intestine absorbs some of which vitamins made by its enteric bacterial “guests | the K and B vitamins |
| What is the phenomenon called where ionic iron, essential for hemoglobin production, is actively transported into the mucosal cells, where it binds to the protein ferritin. | the mucosal iron barrier. |
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