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Define the term digestion and explain its significance.
The chemical and mechanical process of breaking down food and its absorption. Its essential to maintaining life.
Distinguish between mechanical digestion and chemical digestion.
Chemical digestion is where complex food molecules are broken down to the basic building blocks by enzymes. Mechanical digestion is chewing, churning and segmentation.
Distinguish between the alimentary canal and digestive accessory organs.
Alimentary canal (GI tract) is the muscular tube that winds through the body. Accessory organs are teeth, tongue, gallbladder, salivary glands, liver, spleen
List the organs that compose the alimentary canal and identify each on a diagram.
Alimentary canal consists of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. Figure 22.2
List the digestive accessory organs and identify each on a diagram.
Teeth, tongue, gallbladder, and a number of large digestive glands - the salivary glands, liver and pancreas. Figure 22.2
Name the four layers that compose the wall of the alimentary canal from innermost (lining lumen) to outermost.
Mucosa, Submucosa, muscularis externa and serosa.
Compare and contrast the four layers of the alimentary canal wall (named above) in terms of their structure, function, and any distinguishing features.
Mucosa is moist epithelial that secretes mucus, digestive enzymes and hormones. The submucosa is moderately dense connective tissue containing blood vessels and nerve fibers. The muscularis externa is responsible for segmentation and peristalsis. Is made of smooth muscle cells. Sphincters form that act as valves to prevent backflow and control food passage from one organ to the next. Serosa is the protective outermost layer.
Explain the significance of mesenteries or peritoneal extensions.
Mesenteries provides roots for blood vessels, lymphatic's, nerves to reach digestive visera.
Describe how food is moved through the length of the alimentary canal and name the layer responsible for these actions.
Peristalis-Moves down esophagus stimulated by swallowing rate, stomach churn, once in intestine, peristalis every 20 seconds/ muscular layers
Define the term digestive sphincter muscle, describe the structure of these muscles, name the function of these muscles, and denote the major five locations of digestive sphincter muscles.
Digestive Sphincter Muscle- functions- opens for food to travel through closes to prevent back flow. 5 major locations- Gastro esophageal, pyloric, ileoceal, external anal, internal anal
Describe the overall structure and function of the mouth.
Mouth- mechanical breakdown of food- tounge, teeth, frenulum, styloid process, hyoid, taste buds, tonsils at base
Discuss the three portions of the palate, in terms of location and give an overall function for the palate.
The palate forms the roof of the mouth, hard palate anteriorly and soft palate posteriorly. The hard palate forces food during chewing. The soft palate rises reflexively to close off nasophrynx when you swallow, projecting downward from soft palates free edge is the uvula which stops the food from entering.
Name the tissue that composes the tonsils and name the overall function of tonsils.
Tonsils- composed of lymphatic tissue- produce lymphocytes. The tonsils gather and remove many pathogens entering the pharynx in food or in inhaled air.
Name the two sets of teeth we possess as humans, discuss the general structure of a tooth, and describe the four types of teeth we possess according to their location and function.
The two sets of teeth we possess are called milk teeth also called baby teeth. The second set of teeth are called permanent teeth. The general structure of a tooth consist of : crown = exposed area of tooth; root = area below gum (gingiva); enamel =covering on crown; Ca+ salts; hardest substance in body; dentin = bulk of tooth. The four types of teeth we possess are: incisors = front teeth; . break food into bite-size pieces; cuspids = canine (eye) teeth; grasp and tear food; bicuspids = grinding food particles; molars = grinding food particles.
Name and locate the three sets of salivary glands in humans, name and describe the secretions from these glands, and name the two types of cells that compose these glands.
three sets of salivary glands: parotid = largest; lies over masseter, submandibular = floor of mouth; lateral, sublingual = floor of mouth, medial. The two types of cells that compose these glands are: mucous cells secretes mucus; serous cells secretes watery substance containing the enzyme salivary amylase.
Discuss the enzyme "salivary amylase", in terms of its digestive function, location, and secretory gland.
Enzyme = salivary amylase; breaks polysaccharides into disaccharides; starch ----> disaccharides. Located in the salivary gland, secreted by the serous cells.
Name the function of the epiglottis.
The epiglottis is a thin lid-like flap of cartilage tissue that is attached to the root of the tongue. It is situated in front behind the tongue and in front of the entrance to the larynx (voice box).
When resting, the epiglottis allows air to pass through the larynx and into the rest of the respiratory system. When swallowing, it covers the entrance to the larynx to prevent food and drink from entering the windpipe. If both the air passage and the food passage were open when someone swallowed, air could enter the stomach and food could enter the lungs. The epiglottis is the way that this is prevented from happening, basically acting like a lid every time we swallow.
Define the term peristalsis and explain its digestive function.
Peristalsis: accomplished by movements of longitudinal muscle layer; propelling action; As food passes, one section of tube relaxes, opening next section & food moves on.
Describe the macroscopic structure of the stomach and locate it on a diagram or torso model.
The macroscopic structure of the stomach is J-shaped (25-30cm), holds 1 liter, has rugae (folds under the muscle), some absorption of alcohol and drugs, mixing and churning food, and pyloric sphincter.
Name the term used to describe the mucosal folds of the stomach lining and explain their significance.
The mucosal folds of the stomach lining are called rugae. Their significance if when the stomach is empty it collapses inward and throws its mucosa into the rugae.
Name the four types of cells that compose gastric glands, name the secretion(s) that each cell produce(s) that together compose gastric juice, and give the function of each component of gastric juice.
cell-->secretion-->function: 1)mucus cell-->goblet cells-->acidic mucus, 2)chief cell-->pepsinogen-->protein digesting enzyme, 3) parietal cell-->HCl and intinsic factor-->provides surface area, and 4) G cell-->gastrin(hormone)-->regulates stomach secretion.
Name one substance that is absorbed through the gastric mucosa (Stomach Lining).
water, aspirin, or alcohol
Name the hormone that regulates the release of gastric juice, explain when it is released, and the results of its action.
Gastrin - Causes mixing of stomach contents & releases the pyloric spincter when the stomach is full and dumps contents of stomach into small intestine.
Using anatomical terminology, describe the location of the pancreas in the abdominal cavity.
located in the abdominal cavity in the retro peroteneal space
Explain how the pancreas aids in digestion by listing the components in pancreatic juice, and naming the action of each of those components.
Pancreatic juice contains enzymes that digest carbohydrates, fats, proteins, and nucleic acids. Pancreatic enzymes include pancreatic amylase, pancreatic lipase, trypsin, chymotrypsin, carboxypeptidase, and two nucleases. Protein-digesting enzymes are released in an inactive form and are activated upon reaching the small intestine.
Name the regulatory hormone responsible for the release of pancreatic juice into the duodenum, and explain when it is activated.
Protein-digesting enzymes are released in an inactive form and are activated upon reaching the small intestine. The nervous and endocrine systems regulate release of pancreatic juice. Secretin from the duodenum stimulates the release of pancreatic juice with a high bicarbonate ion concentration but few digestive enzymes. Cholecystokinin from the wall of the small intestine stimulates the release of pancreatic juice with abundant digestive enzymes.
Name the functional unit of the liver and describe its general structure.
The Hepatocyte - The liver is divided into right and left lobes, an is enclosed by a fibrous capsule. Each lobe is separated into hepatic lobules consisting of hepatic cells radiating from a central vein. Hepatic sinusoids separate groups of hepatic cells. Blood from the hepatic portal vein carries blood rich in nutrients to the liver.
Define the terms hepatocyte and liver sinusoids.
Hepatocyte - plates of liver cells organized like bricks in a garden. Liver Sinusoids - leaky capillaries between the hepatocytes.
Describe the many functions of the liver.
Liver Functions - The liver carries on many diverse functions for the body. The liver is responsible for many metabolic activities, such as the metabolism of carbohydrates, lipids, and proteins. The liver also stores glycogen, vitamins A, D, and B12, iron, and blood. The liver filters the blood, removing damaged red blood cells and foreign substances, and removes toxins. The liver's role in digestion is to secrete bile.
Name the two blood vessels that supply the liver lobules with blood and track the flow of blood into and out of the liver lobule.
Fed by hepatic portal vein - from small intestine
Fed by hepatic artery to bring nutrients to liver itself
Explain the significance and location of Kupffer's cell.
Kupffer cells carry on phagocytosis in the liver. Secretions from hepatic cells are collected in bile canals that converge to become hepatic ducts and finally form the common hepatic duct.
Define the term emulsification and explain its role in digestion.
breaks down fats so that they can be digested
Name the "common" route that bile travels from either the liver or gallbladder and name the site where bile is deposited.
Cystic duct to common bile duct to Sphincter of Oddi to duodenum
Name the regulatory hormone that is responsible for the release of bile into the duodenum and explain when it is activated.
CCK - it is activated when the small intestine is full of fat and cck is given off to signal the release of bile to mix with lipase so that it can be digested.
Name the three parts of the small intestine, and locate each on a diagram or torso model.
see drawing on page 773 figure 22.1 Duodenum -Jejunum - Ileum
Discuss the histology of the small intestinal wall.
Villi - increased surface area -
blood capillaries - absorb monosac and aa
lacteals absorbs fat
Name the digestive enzymes that are secreted by the mucosa of the small intestines and explain the action of each.
Peptidases, sucrase, lactase, maltase, lipase.
** Intestinal enzymes and pancreatic enzymes break food to smallest subunits - monosac, aa, glycerol, monoglyceride
Identify the simplest forms of food that are absorbed through the mucosa of the small intestine, name the transport process by which each is absorbed, and describe the fate of each absorbed nutrient.
**Amino acids and monosacharrides to liver by hepatic portal vein
**Fatty acids to subclavian veins to circulatory system
**Peristalsis sends food to colon thru ileocecal valve and sphincter
Define the term lacteal and explain its significance.
Special lymphatic capillaries of the small intestine that take up lipids.
Distinguish between the duodenum and the distal small intestine (i.e. jejunum and ileum) in terms of function.
-->Duodenum is retroperitoneal.--> 1. the villi 2. Absorbs digested food. 3. Intestinal enzymes work with pancreatic enzymes. 4. Absorbs electrolytes & water
--> Ileum --> Ileocecal valve to colon
*********************************************************************The pylorus is continuous with the duodenum through the pyloric sphincter, which controls stomach emptying. The duodenum regulates the rate of emptying of the stomach via hormonal pathways. As chyme enters the duodenum, receptors in its wall respond to chemical signals and to stretch, initiating the enterogastric reflex and the hormonal (enterogastrone) mechanisms that inhibit acid and pepsin secretion. These mechanisms inhibit gastric secretory activity and prevent further duodenal filling by reducing the force of pyloric contractions. Fatty chyme is digested more slowly than carbohydrate-rich foods, slowing emptying of the stomach to six hours or more. Secretin, cholecystokinin (CCK) and vasoactive intestinal peptide (VIP) are released from cells in the duodenal epithelium in response to acidic and fatty stimuli present there when the pylorus opens and releases gastric chyme into the duodenum for further digestion. These cause the liver and gall bladder to release bile, and the pancreas to release bicarbonate and digestive enzymes such as trypsin, lipase and amylase into the duodenum as they are needed. The submucosa of the duodenum contains mucus-secreting duodenal (Brunner's) glands which produce an alkaline (bicarbonate-rich) mucus that helps neutralize the acidic chyme moving in from the stomach. The bile duct, delivering bile from the liver, and the main pancreatic duct, carrying pancreatic juice from the pancreas, unite in the wall of the duodenum in a bulb-like point called the hepatopancreatic ampulla. The ampulla opens into the duodenum via the volcano-shaped major duodenal papilla. The entry of bile and pancreatic juice is controlled by a muscular valve called the hepatopancreatic sphincter, or sphincter of Oddi. Most absorption occurs in this part of the small intestine.
Name the four parts of the large intestine and locate each on a diagram or torso model.
page 773 figure 22.1
Name the four parts of the colon and locate each on a diagram or torso model.
page 813 figure 22.29 (a).
1. Ascending colon
2. Transverse colon
3. Descending colon
4. Sigmoid colon
Identify the major digestive function of the large intestine.
Secretion - only mucus
Absorption - water and electrolytes
Storage - feces
Home to bacteria ***********************************************************************
Some remaining food residues are digested by enteric bacteria (which also produce vitamin K and some B vitamins). Water and electrolytes (mostly NaCl) and vitamins produced by bacteria are absorbed in the large intestine.
Explain how the movements in the large intestine differ from those throughout the rest of the alimentary canal.
Movements (peristalsis)-force contents into rectum
Occur only 2-3 times a day- usually follow a meal
************************************************************** Waves of peristaltic contractions move food in the esophagus unidirectionally into the stomach. In the pylorus peristalsis is bidirectional, compressing and mixing chyme. The pyloric muscle squirts a small amount of chyme into the small intestine, propelling the rest backward into the stomach, breaking up solids. Peristalsis rate is constant at about three waves per minute. The peristaltic waves of the small intestine are segmenting movements. Unlike the stomach pacemakers, which have only one rhythm, the pacemakers in the duodenum fire more frequently (12-14 waves per minute) than those in the ileum (8 or 9 contractions per minute). The intensity of segmentation is altered by long and short reflexes. Peristalsis consists of the Migrating Motility Complex (MMC), which sweeps food in continuous waves of about 2 ft in length from the duodenum toward the ileum. In the large intestine, movement most seen are haustral contractions, slow segmenting movements lasting about one minute that occur every 30 minutes or so. These contractions, which occur mainly in the transverse and descending colon, reflect local controls of haustra. As a haustrum fills with food residue, the distension stimulates its muscle to contract, which propels the luminal contents into the next haustrum. These movements also mix the residue, which aids in water absorption. Mass movements (mass peristalsis) are long, slow-moving, but powerful contractile waves that move over large areas of the colon three or four times daily and force the contents toward the rectum.
Define the terms feces and defecation.
Feces- material discharged from the bowel; composed of food residue, secretions, and bacteria
Defecation- elimination of feces
Name the sphincter muscles that open to the outside and explain how their action is controlled.
external sphincter- other reflexes from spinal cord causes the external sphincter to relax, it can also be voluntarily inhibited.
List the four major organic macromolecules that we ingest, and explain how each is broken down by various enzymes within the alimentary canal. Be sure to include enzyme names, the location of enzyme action, the breakdown products that result from the enzymatic action, and explain any hormonal control of the breakdown. Finally, explain how and where these simplest food forms are absorbed into the bloodstream or lymphatic system.
four organic molecules: carbs, lipids, protein, nucleic acid.
a) carb digestion starts with the breakdown of starch and disaccharides to simple glucose with the help of the salivary amylase and pancreatic amylase. Digestion of carbs occurs in the mouth and small intestine.
b) Fat digestion occurs when pancreatic lipase breaks down fat into glycerol and fatty acids in the small intestine. Excess fat go to adipose tissue for storage.
c) protein digestion occurs when protein is broken down into amino acids with the help of pepsin in the stomach and pancreatic enzymes in the small intestine.
d) nucleic acid digestion happens in the small intestine with the help of the enzyme nuclease.
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