Digestion Notes ans.pdf

DIGESTIVE SYSTEM  INTRODUCTION: We obtain energy and materials for growth and repair of our bodies from the food that we eat. Food contains ___________________________, or substances needed for the body’s growth and maintenance.  NUTRIENTS include: Carbohydrates; proteins, lipids,...

DIGESTIVE SYSTEM  INTRODUCTION: We obtain energy and materials for growth and repair of our bodies from the food that we eat. Food contains ___________________________, or substances needed for the body’s growth and maintenance.  NUTRIENTS include: Carbohydrates; proteins, lipids, minerals; vitamins; water and +/- fiber. Non-digestible = ________________________________ ENERGY - _________________________________ FOOD - _________________________________ Nutrients CELL BUILDING- - _______________________________ - _______________________________ - _______________________________ - ________________________________ “YOU ARE WHAT YOU EAT” is not an accurate statement. There is no problem when it comes to water, vitamins and minerals. These can go to the cells unchanged. The problem comes with the three organic compounds. These are generally large molecules (POLYMERS). Cells cannot break down carbohydrates and fats directly for energy. Cells cannot use proteins directly for growth. Each of the three organic compounds must be reduced to their simple forms (MONOMERS), so that they can be absorbed and distributed to cells by the circulatory system.  THIS IS THE ROLE OF THE DIGESTIVE SYSTEM Within the digestive system, these large molecules are digested into monomers by _______________________ reactions. Digestion takes place within a tube called the ______________________________________ (also called the G.I.T. = Gastrointestinal Tract), which allows ONE-WAY transport because of wavelike muscle contractions and the actions of sphincter muscles. -This one-way transport allows different regions of the digestive tract to be specialized for different functions, such as an “ASSEMBLY” line. There are seven functions: 1. INGESTION: (“eating”) = the taking of food into the digestive system by way of mouth. 2. MASTICATION: (“chewing”) = chewing movements to pulverize food and mix it with saliva in the mouth. 3. DEGLUTITION (“SWALLOWING”) = the swallowing of food to move it from the mouth to the stomach. 4. DIGESTION = the process by which food is changed into a form the body can use.  There are two forms: i. ___________________________ digestion = the physical tearing and grinding of food into smaller pieces, thus increasing the amount of surface area of food exposed to the action of digestive enzymes. ii. ____________________________ digestion = changing large polymer food particles into small monomers the body can use. This is done mainly by the action of hydrochloric acid, bile and a variety of digestive enzymes. 5. ABSORPTION = the passage of the monomers of food molecules through the wall of the small intestine into the blood or lymphatic vessels. 6. Peristalsis = Rhythmic, wavelike contractions that move food one-way through the digestive tract. 7. DEFECATION (“egestion”) = the discharge or elimination of indigestible, non-usable wastes, called feces, from the body (through the anus).  Anatomically and functionally the digestive system can be divided into a tubular __________________________________________ (Gastrointestinal tract [G.I.T.]), and ______________________________________________________.  DIGESTIVE TRACT: The digestive tract is a tube that is approximately 9m (30ft) long, running through the body from the mouth to the anus. The lumen (inside of the tube) of the digestive tract, like the hole in a doughnut, is continuous with the external (outside) environment, which means that its contents are technically outside of the body. This fact is relevant to an understanding of some of the tract’s properties. -Indigestible material, such as cellulose from plant walls (fiber), passes from one end to the other without crossing the wall of the digestive tract (without being absorbed). Therefore, they never enter the body. -The lower part of the digestive tract is inhabited by millions of bacteria, most of which are harmless and even beneficial in this location “outside” of the body; however, if the same bacteria enter the body, as may happen, for example in the case of a ruptured appendix, they may be extremely harmful and even lethal.  The organs of the digestive tract include: 1. MOUTH (“oral cavity”) 2. PHARYNX 3. EPIGLOTTIS 4. ESOPHAGUS 5. CARDIAC SPHINCTER 6. STOMACH 7. PYLORIC SPHINCTER 8. DUODENUM (SMALL INTESTINE) 9. Rest of SMALL INTESTINE 10. APPENDIX 11. LARGE INTESTINE (Colon) 12. RECTUM 13. ANUS  ACCESSORY DIGESTIVE ORGANS: = Aid in digestion. They include: 14. TONGUE 15. TEETH 16. SALIVARY GLANDS 17. LIVER 18. GALL BLADDER 19. PANCREAS LABEL THE PARTS OF THE DIGESTIVE SYSTEM ON THE FOLLOWING DIAGRAM: THE DIGESTIVE SYSTEM  THE MOUTH = the oral cavity of the mouth receives the food when humans eat. Most people enjoy eating largely because they like the texture and taste of foods. -Receptors called _____________________ are found primarily on the tongue. These are activated by the presence of food in the mouth. -Mechanical and chemical digestion both start in the mouth  Mechanical Digestion: Teeth -Approximately 32 adult teeth -Food is bitten, cut, and torn by the INCISORS, the sharp teeth at the front of the mouth, and the teeth next to them, the canines (“fangs”) -Strong muscles of the jaws and tongue move the food in position for chewing. -Food is then crushed and ground by the broad, flat surfaces of the PREMOLARS and MOLARS at the rear of the mouth. Chemical digestion: Salivary Glands -While in the mouth, food is moistened by ______________, a mixture of ________________ and a digestive enzyme called __________________________. -Saliva is produced by three pairs of salivary glands.  The mucus in saliva helps to LUBRICATE the food so that it moves smoothly through the digestive tract. Saliva may also kill some bacteria in the mouth.  The salivary amylase starts the breakdown of the polysaccharides STARCHES into many molecules of the disaccharide MALTOSE (two glucose molecules joined together) -However, because food remains in the mouth for such a short time, salivary amylase only acts on less than 5% of the starches. Also, maltose molecules cannot be absorbed by the digestive tract lining, and therefore further digestion must occur in the small intestine to convert maltose to glucose.  THE TONGUE = The tongue, which is composed of muscle with an outer layer of mucous membrane (where taste buds are), mixes the chewed food with saliva, it then forms this mixture into a mass called a ______________ in preparation for swallowing.  THE PHARYNX (“THROAT”) = Swallowing (deglutition) occurs in the pharynx, a region between the mouth and the esophagus, which is a common passage for food and air.  Mechanisms of SWALLOWING: A. Swallowing is a complex ___________________________________ initiated when pressure is put on the walls of the pharynx by a bolus of food that is forced into the rear of the mouth by the tongue. -During this stage, the mouth is closed and breathing is temporarily interrupted. B. The tongue then pushes the bolus to the back of the mouth and forces the ___________ ________________ to close off the nasal cavity. C. At the same time, a flap of tissue called the ___________________________ seals off the trachea (windpipe) at the glottis, and the food bolus moves through the relaxed ____________________________________________. -If a person attempts to breathe while swallowing, food and water may get into the trachea. = An automatic coughing reflex helps to prevent this. D. Immediately after the bolus has passed, the upper esophageal sphincter closes, the glottis opens, and breathing resumes.  THE ESOPHAGUS = A tube that connects the pharynx with the stomach. -Once in the esophagus, the bolus is moved toward the stomach by ___________________________, a rhythmic, one-way, wave-like motion that occurs along the entire length of the digestive tract. -The CARDIAC SPHICTER (lower esophageal sphincter) opens and remains relaxed throughout the period of swallowing, allowing the arriving bolus to enter the stomach. Function of cardiac sphincter = after the bolus has passed, the sphincter closes to prevent the stomach contents from regurgitating into the esophagus (“gastric reflux”) and burning the unprotected lining of the esophagus (=“HEARTBURN”)   Mechanism of PERISTALSIS: -Peristalsis results from the action of two layers of involuntary muscles (not under conscious control) that form the walls of most of the digestive tract. -One layer of muscle wraps around tract (CIRCULAR MUSCLE) which can contract and squeeze the tube to a narrow diameter, and the second layer runs along its length (LONGITUDINAL MUSCLE) which can contract to shorten the tube.  As food is swallowed, the circular muscles above the bolus contract, pushing the bolus downwards. At the same time, longitudinal muscle below the bolus contract, shortening the passageway ahead of the bolus.  These contractions continue in _______________________________, pushing the bolus in one direction through the tract until it enters the stomach. Note: Swallowing can occur while a person is upside down since it is NOT primarily gravity, but the peristaltic wave which moves the bolus to the stomach.  THE STOMACH = Food passes through the cardiac sphincter into the stomach, a J-shaped, sac-like organ that stores food while it is mixed with gastric juices. Having a stomach is the main reason we don’t have to eat constantly. -The stomach can stretch to a capacity of approximately 2L, usually storing enough food and liquid to satisfy our body’s needs for many hours. -Both mechanical and chemical digestion continues (from the mouth) in the stomach: Mechanical digestion: Muscles -In addition to the two layers of involuntary muscle (circular and longitudinal) as seen in the esophagus, the stomach has a third, diagonal layer of muscle. Through the action of these three muscle layers, the stomach can actually GRIND food while it is mechanically churned with the gastric juices. -Hunger pangs (“gurgles”/”growls”) are felt when an empty stomach churns, making a hollow echo sound.  Chemical digestion: Glands -Chemical digestion of ______________________ begins in the stomach  The inside surface of the stomach is highly folded, and contains about 35 million _____________________________ that are lined by cells that produce mucus and cells that produce gastric juices.  The glands in the upper part of the stomach (____________ and ______________) secrete: 1. _________________________________ = precursor of the enzyme _______________. -When pepsinogen is exposed to HCl, it is converted to pepsin, a hydrolytic enzyme (able to perform hydrolysis reactions) that act on proteins to produce shorter chained peptides. -Peptides are too large to be absorbed by the stomach lining, but later they are further broken down to amino acids in the small intestine. 2. _____________________________ = (HCl : pH 2) -Lowers the pH of the stomach to optimum pH for pepsin enzyme to function. -This acidic environment allows the pepsinogen to convert  to pepsin -Denatures other proteins so they can be more easily digested. -Dissolves minerals and kills most bacteria. 3. ____________________________ = a thick fluid that helps PROTECT the stomach lining from acid HCl and digestion by pepsin. -An “ulcer” occurs when there is a deficiency in protective mucous, and pepsin and hydrochloric acid, destroying the stomach lining faster than it can regenerate.  The glands in the lower part of the stomach (______________________) secrete: 1) PEPSINOGEN (the same function as above) 2) MUCUS (same function as above) 3) _________________ (only from the antrum) = a HORMONE (“chemical messenger”) produced in the lower part of the stomach in response to a HIGH PROTEIN MEAL. -Cells in our gastric glands do not secrete gastric juices constantly. Their activity is regulated by a combination of nerve signals (once you see, smell, or taste food, as signals from your brain to your stomach stimulate your gastric glands to secrete gastric juices) and the hormone gastrin. Once you have a high protein meal in your stomach, the cells of the lower stomach wall secrete gastrin into the bloodstream. Gastrin circulates in the bloodstream and is transported to the upper part of the stomach, where it causes the gastric glands to SECRETE MORE PEPSINOGEN (PEPSIN) AND HYDROCHLORIC ACID.   Movement of food into the small intestine: -Normally, the stomach empties in about 2 to 6 hours. -By this time the bolus food has become a semiliquid, Acidic paste called _____________, which leaves the stomach and enters the small intestine through the pyloric sphincter. = The pyloric sphincter repeatedly opens and closes, allowing chyme to enter the small intestine in small squirts. -Like the esophagus, material moves one-way through the stomach by PERISTALTIC WAVES. -Each wave begins near the entry of the esophagus as a ripple, but becomes more powerful as it reaches the antrum. This closes the pyloric sphincter, only letting very small amounts of chyme into the small intestine. The rest is forced back into the antrum, where it can be mixed and churned some more. Note: There is no ______________________ of food substances in the stomach. The only commonly ingested substances that can be absorbed across the stomach wall are alcohol and aspirin. This occurs as a result of the lipid solubility of these molecules (able to diffuse through the cell membrane).  THE SMALL INTESTINE -Food leaves the stomach and enters the small intestine as CHYME. -The small intestine is approximately 6 meters long and 2.5 cm wide. It is called the “small” intestine because of its relatively small diameter compared to that of the large intestine (1.5 m long and about 6 cm wide) -In the small intestine, the breakdown of food that started in the mouth and stomach is completed. The small intestine serves as the major site of ______________________________ and __________________________________ but NO MORE MECHANICAL DIGESTION occurs beyond this point. Chemical Digestion in the Small Intestine = most chemical digestion occurs in the _______________________, the first 25 cm of the small intestine. -This area is protected from the acidic chyme released by the stomach by a heavy layer of _______________________, secreted by GOBLET CELLS in the epithelium (wall) of the small intestine. (Goblet cells are the cells that actually make mucus in the entire length of the digestive tract) -The small intestine contains a mixture of ______________________________, some produced by the intestinal cells and some produced by the pancreas and liver.  PANCREAS: (accessory organ) = the pancreas, located below and behind the stomach, is a mixed gland containing both ___________________ portions (hormone secretion) and ___________________ portions (digestive enzyme secretion). -The endocrine cells secrete into the blood the hormones _________________ and ______________________________, which help keep blood glucose levels within normal limits. -The exocrine cells secrete ____________________________________ which contain digestive enzymes and ___________________________________ (NaHCO3). -The pancreatic juices are transported to the small intestine by a single _______________________________ that joins the common bile duct from the liver just before entering the duodenum. -The pH of the small intestine is __________________ (alkaline), because it contains NaHCO3. In the intestinal lumen the bicarbonate ions neutralize the acidity of the chyme leaving the stomach (protection). -Pancreatic juice contains enzymes for the digestion of all types of foods. The four major pancreatic enzymes are: 1) ________________________________________________________ 2) _________________________________________________________ 3) ________________________________ 4) ________________________________ 1) PANCREATIC AMYLASE = similar to salivary amylase: continues the chemical digestion of starch that began in the mouth. - digests (hydrolyzes) STARCH into MALTOSE (still too big to be absorbed). 2) TRYPSIN = similar to pepsin: continues the chemical digestion of proteins that began in the stomach. - secreted as TRYPSINOGEN (inactive), which is converted to TRYPSIN (active) in the duodenum. (converted by an enzyme called enterokinase) 3) NUCLEASE = digests (hydrolyzes) strands of NUCLEIC ACID into NUCLEOTIDE monomers. - Nucleotides are small enough to be absorbed at this point.  4) LIPASE = digests (hydrolyzes) small FAT DROPLETS (neutral fats) into GLYCEROL + 3 FATTY ACIDS after they have been EMULSIFIED by BILE SALTS from the liver. -Glycerol and fatty acids are small enough to be absorbed at this point. REGULATION OF BLOOD GLUCOSE LEVELS (hormone supplement) Recall that the PANCREAS is a mixed gland containing two types of tissue: 1) _________________________ = produce and secrete the pancreatic juices (digestive enzymes and sodium bicarbonate) that are transported by the pancreatic duct to the duodenum where they digest food particles. 2) _________________________ = produce and secrete the hormones ____________________ and __________________, directly into the blood. INSULIN and GLUCAGON are hormones that affect the blood glucose levels in opposite directions.  INSULIN: -Insulin is secreted when there is a high blood glucose level, which usually occurs after eating. -Insulin has three different actions: 1) Stimulates the liver, fat, and muscle cells to take up and metabolize glucose 2) Stimulates liver and muscle cells to store glucose as glycogen 3) Promotes buildup of fats and proteins, and inhibits their use as an energy source. -Therefore, insulin is a hormone that promotes storage of nutrients so that they are on hand during leaner times. It also helps to lower the blood glucose levels. Diabetes Mellitus: (Hyperglycemia = “high blood sugar”) = a condition that is characterized by a high blood glucose level and the appearance of glucose in the urine. -Since the cells are not able to metabolize and use the glucose, the body turns to the breakdown of protein and fats for energy. The metabolism of fat leads to the buildup of ketones in the blood and acidosis (acid blood) that can eventually cause coma and death. -Type 1 (insulin-dependent) – the pancreas is not producing insulin -Type 2 (insulin-independent) – the pancreas produces insulin, but the cells do not respond to it, and therefore do not take up insulin. Thought to be due to obesity and inactivity. GLUCAGON: -Glucagon is secreted in between meals, when there is a low blood glucose level. -Glucagon has the opposite effects to those of insulin. -Glucagon stimulates the breakdown of stored nutrients and causes the blood glucose levels to rise. LIVER: (“accessory organ”) =The liver, which is the largest internal organ in the body, lies mainly in the upper right section of the abdominal cavity, under the diaphragm. -The liver has two main LOBES, the right lobe and the small left lobe. -The liver contains approximately 100,000 LOBULES (small lobes), that contain the cells responsible for the many functions of the liver. The 6 major functions of the liver include: 1) The liver produces ________________, which is stored in the GALL BLADDER and sent by way of the COMMON BILE DUCT (which joins the pancreatic duct) to the duodenum. -Bile contains BILE SALTS, which are emulsifying agents that break down fat into smaller droplets. This greatly increases the surface area of the fat droplets, so that pancreatic LIPASE can digest them more effectively in the duodenum. -Bile has a yellowish green colour (i.e. a bruise colour) because it contains the bile pigments bilirubin and biliverdin, which are derived from the breakdown of hemoglobin, the red pigment found in red blood cells (i.e. a bruise). 2) The liver _____________________________________________________ from the red blood cells into the bile pigments bilirubin and biliverdin, which are released into the bile along with bile salts and excreted through the intestinal tract. 3) The liver _________________________ the blood by filtering out and removing poisonous substances.  It then breaks down (metabolizes) these toxic substances into less harmful products.  However, some of these toxic substances form metabolic products that damage liver cells and interfere with their functions. i.e. ethanol (beverage alcohol); drugs 4) The liver produces ________________________________ from amino acids, that make the blood HYPERTONIC in relation to the tissues surrounding the cells and blood vessels.  This prevents the loss of water by OSMOSIS from the blood (plasma) to the tissues. 5) The liver _______________________________________ as glycogen (INSULIN) after eating and also breaks down glycogen back to glucose (GLUCAGON) to maintain the glucose concentration of blood between meals. 6) If the supply of glycogen or glucose is depleted, (or if there is an excess of amino acids), the liver will convert AMINO ACIDS to glucose molecules. -The liver _______________________ (deamination) the amino acids by removing the amine groups (-NH2) and producing ammonia (NH3), which is poisonous to cells. -The liver then converts the ammonia to UREA, which enters the bloodstream and is excreted in the urine by kidneys. Absorption in the Small Intestine: = Once mechanical and chemical digestion are complete, most of the absorption of molecules occurs in the small intestine (duodenum + jejunum + ileum). The small intestine is specialized for absorption in two major ways: 1) __________________________________ = approx. 6 meters; allows for adequate time for absorption to occur. 2) ________________________________________ = the inside lining of the small intestine consists of millions of fingerlike projections called VILLI (sing. Villus), which are covered with a single layer of epithelial and mucus producing (goblet) cells. The epithelial cells of the villi are further covered with thousands of tiny projections called _______________________.  Together these folds increase the surface area of the lining of the small intestine by approximately 600 times. The result is an absorptive area the size of a tennis court!  Absorption takes place across the wall of each Villus, through the process of FACILITATED DIFFUSION and ACTIVE TRANSPORT. -Each villus contains tiny blood vessels (capillaries), which carry blood to the villus (arterioles) and then away from the villus and to the liver (venules). -Each villus also contains a small blind- ended lymph vessel called a _______________. (More later) -Absorption occurs quickly because the villus epithelium is only ____ cell thick. SUMMARY OF THE SIX MAJOR FUNCTIONS OF THE LIVER 1) 2) 3) 4) 5) 6)  Digestive Enzyme Secreting Glands of the Small Intestine: -The epithelium (wall) of the small intestine contains millions of digestive glands that produce enzymes that add to the _________________________________ and complete the CHEMICAL DIGESTION of protein and carbohydrates.  Enzymes produced by the small intestine include: 1) _________________________________ = digests (hydrolyzes) peptides which resulted from the first step in protein digestion (PEPSIN and TRYPSIN), into amino acid monomers. 2) ________________________________ = digests (hydrolyzes) maltose which resulted from the first step in starch (carbohydrate) digestion (SALIVARY AMYLASE and PANCREATIC AMYLASE), into glucose monomers. Note: Other disaccharides, like lactose and sucrose, have their own specific enzymes secreted by the small intestine. For example, lactose is digested by the lactase enzyme and sucrose is digested by the surcease enzyme. ABSORPTION OF NUTRIENTS:  Monosaccharides, Amino Acids, Nucleotides, Vitamins and Minerals: = these nutrients are rapidly absorbed from the small intestine by facilitated diffusion (if they are in high concentrations in the gut and low concentrations in the blood) and active transport (if they are in low concentrations in the gut and high concentrations in the blood into the capillaries of the villi. -These capillaries carry these nutrients to the venule, which combine to form the ________________________________________. -The hepatic portal vein then carries the absorbed molecules to the liver so they can be made available to the body cells for use and consumption.  Water: = rapidly absorbed by osmosis, if high water concentration in the gut and low water concentration in the blood.  Fats: = the products of fat digestion are GLYCEROL + 3 FATTY ACIDS. - Short-chained fatty acids diffuse into the blood vessels of the villi directly (as above). - Long-chained fatty acids and glycerol receive special treatment during absorption: They diffuse into the villi epithelial cells and within these cells are rejoined into _______________________________ molecules. They are then packaged with cholesterol and other fatty substances, coated with lipoproteins, forming small globules called _______________________________, which are secreted by exocytosis into the lymph vessel (lacteal). - Lymph vessels are part of a system of tubes that return fluids from the tissues to the blood. - Once in the lacteal, the chylomicrons are in the lymphatic system. Lymph fluid is “milked” from the lacteal by rhythmic contractions (peristalsis) of the villi. Eventually the lymph enters the blood (circulatory system) at the _________________ duct near the heart.  THE LARGE INTESTINE = the large intestine, a tube about 6 cm in diameter, form the last 1.5m of the digestive tract. The large intestine is structurally divided into 4 regions. 1. The first portion of the large intestine, the _________________, forms a blind ended pouch from which the appendix extends. >> The appendix is a small fingerlike projection that has no known function (some studies suggest it may be involved in the production of antibodies in the immune system) >> The appendix is subject to inflammation, a painful condition called APPENDICITIS. 2. The next portion is called the ________________, which consists of three relatively straight segments – the ASCENDING, TRANSVERSE and DESCENDING portions. Peristalsis, which began in the esophagus, occurs along the entire digestive tract, including the colon. 3. The ____________________ is the last 20 cm of the large intestine. It stores feces before defecation. 4. The opening of the rectum to the exterior is called the ______________. It controls the elimination of feces through the ANAL SPHINCTER.  The 2 major functions of the large intestine are _______________________ and ______________________.  Absorption in the Large Intestine: - The inner wall of the large intestine is adapted to absorption with folds, however, it does not have villi or microvilli as the small intestine does. - The absorption of water, minerals, and vitamins is completed in the large intestine. These nutrients then enter the blood. No digestion occurs in the large intestine. About 1.5 liters of water enter the digestive tract daily as a result of eating and drinking. An additional 8.5 liters enters as secretions from the various glands (mucus, saliva, bile, pancreatic secretions, etc.) -About ______ of this water is reabsorbed by the cells lining the large intestine. If too little water is absorbed, DIARRHEA results, and if too much water is absorbed, CONSTIPATION occurs.  A species of bacteria called Escherichia coli (E. coli) lives in the large intestine. -These organisms and others (many different species of bacteria inhabit the colon), are usually harmless and live on nutrients we are unable to digest. They use the undigested material to make vitamins and amino acids, some of which are absorbed into the bloodstream.  E. coli are our chief source of ________________________ (important in blood clotting). Defecation in the large intestine (“egestion”): -About 24 to 30 hours after food is ingested, the first waste products, called FECES, may be egested from the anus by peristalsis. As the rectum fills, it distends until it is sufficiently stimulated to give rise to nervous reflex called the ________________________________________ -The feces are made up of undigested food (mostly cellulose plant fibers), some inorganic material, bile pigments (which account for its colour), water, and large quantities (approx. 30%) of bacteria (which accounts for its smell). REGULATION OF THE DIGESTIVE SYSTEM  Methods of Control: The body has two ways of controlling digestion: 1. ________________________________ = reflexes controlled by nerve signals to the brain -For example, as soon as you put food into your mouth (or even think about or smell food!), a signal travels through a nerve to your brain. The brain’s immediate response is to send nerve signals to the salivary glands, stimulating them to produce saliva, the brain also sends signals that stimulate the muscles in the digestive tract wall to begin peristalsis. 2. _______________________________ (“chemical messengers”) = substances produced by one set of cells that affect a different set of cells. -Hormones are usually transported by the blood stream.   Secretion of digestive juices are under control of three hormones: 1) GASTRIN: = Recall that meals rich in protein cause the lower part of the stomach (antrum) to produce the hormone gastrin, that enters the bloodstream and travels to the upper part of the stomach (fundus and body), where there is a stimulation to produce more pepsinogen and HCl) 2) SECRETIN and 3) CCK (cholecystokinin): = the cells of the wall of the duodenum produce these two hormones. -Secretin is produced in response to acid present in chyme entering the duodenum. -Partially digested protein and fat stimulate the release of CCK. Both hormones do the same thing: They both enter the bloodstream and stimulate the pancreas to increase its output of pancreatic juices (digestive enzymes and NaHCO3) and stimulate the liver to increase its output of bile. The gall bladder then contracts to release the bile.  Name: ____________________ Date: __________ Blk: _____ The Adventures of a Cheese Burger with Lettuce and Tomato through the Digestive System  This sandwich contains _____________ (in the meat), ____________ (especially in the cheese), ___________________________ (in the bread and vegetables), nucleic acids, vitamins, minerals, trace elements. Most of the nutrients must first be _______________________ down before they can be absorbed.  The mouth grinds up the food with the action of its ______________, which tear, grind, and mash to a pulp (now called a ____________). The food is moistened and lubricated with ________________, and at the same time _______________ _______________ in the saliva breaks some of the ________________ in the food to maltose.  The food passes through the ________________ and into the _______________, and moves down this tube through ________________ (muscle contractions). It enters the stomach through the ____________ ___________.  Presence of protein in the food (as well as the stretching of the stomach) causes _________________ to be released into the blood, which causes the gastric glands at the top of the stomach to release _______________ ___________ (containing _________________ and _________________ which combine to form __________________).  In the stomach, the food is churned by the stomach, and the enzyme ______________________ breaks down some of the _____________________ into smaller _____________________. _________________ kills much of the bacteria in the food and provides the optimal pH for the enzyme to work.  The food, now called ____________, passes through the ____________________ ________________ into the _____________________ of the small intestine. Its presence causes the small intestine to release the hormones ___________________ and _____________________. __________________ causes the pancreas to release __________ __________, which is sent through ducts to the small intestine, where it __________ the acid chyme, and makes the pH of the small intestine slightly _______________. CCK acts on the _______________ __________________, causing it to release ________________ into the small intestine. Bile __________________ fats into small droplets that can be more easily attacked by ___________________. CCK also acts on the pancreas, causing it to release _______________ _________________, which contains the enzymes __________________ __________________ (digests starch to __________________), ________________(digests polypeptides to smaller polypeptides), _________________ (digests fats to glycerol and fatty acids), and ______________________ (digest DNA and RNA to nucleotides).  The small intestine itself produces _______________ (digest small polypeptides and dipeptides to amino acids), _____________________ (digests maltose to glucose), ________________ (digest sucrose to glucose and fructose) and ______________________ (digests lactose to glucose and galactose).  Thus, all parts of the food are digested to _____________________ (e.g. glucose, amino acids, glycerol, fatty acids) in the small intestine.  The digested food moves into the much longer _________________ and __________________ of the small intestine. Here it is absorbed across the walls of the _____________ lining the small intestine. Glucose, amino acids, and other water soluble compounds moving into the _______________ network in each villus. They move in the blood to the liver through the ________________ ________________ __________________. ______________ acids and ___________________ are absorbed across the villi, are recombined into __________ molecules in the epithelial cells of the villus. The fats then move into the ___________________ of each villus and enter the ______________________ system. The lymphatic system eventually rejoins the circulatory system where the two systems connect near the left shoulder.  Absorption is both ________________ and passive. The __________________ processes all the nutrients, storing some, interconverting others, and releases them into the bloodstream as necessary to maintain nutrient levels.  The non-digestible material that is left (consisting of water, cellulose fiber, bacteria, and traces of other materials such as heavy metals) passes from the small intestine, and into the _________________ ___________________.  In the large intestine, about 90% of the _________________ is absorbed from the non-digestible material, now called _____________________. Bacteria in the large intestine, including ________________, the most common bacteria in the digestive system, feed on non-digested material, and in the process produce the gases methane, hydrogen sulfide, and vitamin _______ (which is absorbed by the host). Finally, the feces pass out of the body via the _________________.  Name: ___________________ Digestive System Worksheet BC Biology 12 p. 266-279 Digestive System 1. Label the parts of the digestive system and describe its main function(s). 2. The function of the digestive system is to ___________________ food, separate it into chemical __________________ that cells can use, ______________________ those nutrients and ______________________ indigestible remains. Digestion begins at the ________________ and ends at the _______________. 3. Mechanical digestion begins with the ____________________ of food in the _____________ and continues with the churning and __________________ of food in the __________________. During ______________________ digestion, many different ____________________ break down macromolecules to small organic molecules to be __________________________. 4. Sensory receptors called ____________ _______ occur primarily on the tongue. The roof of the mouth separates the ________________ cavity from the mouth. The roof has 2 parts: a ____________ palate and a ___________ palate. The soft palate ends in a projection called the ____________________. Three pairs of ______________________ glands produce saliva to keep the mouth __________________. Saliva also contains an enzyme which begins the process of digestion by digesting __________________. 5. The ________________ is a region that receives _______ from the nasal cavities and __________ from the mouth. From the mouth, food (________________________) passes through the pharynx and esophagus to the stomach. During swallowing the soft palate moves ___________ to close off the nasopharynx, and the trachea moves up under the _______________________ to cover the glottis (the opening to the __________________). This forces the bolus to go down the esophagus by means of rhythmic contractions called  ______________________ towards the stomach. Peristalsis begins in the _______________________ and continues in all the organs of the _________________________ tract. Sphincters are muscles that encircle tubes in the body, acting as ________________. The entrance of food into the stomach is controlled by the _____________________ sphincter. 6. The stomach is a thick-walled, J-shaped organ which _____________ food and mixes it with gastric __________ produced by gastric glands. The gastric juices contain pepsinogen, __________, and _______________. The high acidity of the stomach is beneficial because it kills most of the _________________ and other _________________. The stomach acts both ____________________ and chemically on food. When food leaves the stomach, it is a thick, soupy liquid called ______________. Chyme enters the small intestine in squirts by way of the _________________ sphincter. 7. The first part of the small intestine is called the __________, into which ducts from the gallbladder and __________ enter. The middle part of the small intestine is called the __________________ and the remainder is the _____________. The wall of the small intestine contains fingerlike projections, called __________. Microvilli greatly increase the __________________ area of the villus for the absorption of ____________________. Each villus contains blood capillaries and a small lymphatic vessel called a __________. 8. The large intestine includes the cecum, the __________, the rectum, and the __________ canal. The large intestine absorbs _______________, salts and some __________________. The vermiform appendix, attached to the __________, may become inflamed, causing ____________________, and if it bursts, peritonitis. Obligate anaerobes in the colon break down nondigestible material and produce some ______________. 9. The major causes of _________________ are infection of the lower tract and nervous stimulation. Two components of the diet that can help prevent constipation are water and __________. Three Accessory Organs 1. What is the endocrine function of the pancreas? 2. What is the exocrine function of the pancreas? 3. The structural - functional unit of the liver is the __________. The __________ artery of the triad brings oxygenated blood to the liver. The ______________________________ brings nutrients to the liver from the intestines. The __________ duct takes bile away from the liver. The liver acts as the ______________ to the blood because it __________. The liver produces __________, which is stored in the gallbladder. Bile contains bile salts. 4. When a person has __________ , there is a yellowish tint to the whites of the eyes. Inflammation of the liver is called _________________. _________________ of the liver occurs when it becomes fatty, and liver tissue is then replaced by fibrous scar tissue. The __________ stores bile. Digestive Enzymes and Hormones 1. Digestion of starch begins in the mouth by the enzyme ____________________ and later in the small intestine by pancreatic amylase. Maltose that is formed is converted to __________ by maltase. 2. Protein digestion begins in the _______________ by the enzyme __________ , which converts proteins to peptides. The pancreatic enzyme _____________ also converts proteins to peptides. Peptides, in turn, are converted to amino acids by the enzyme ________________ from the intestine. 3. The enzyme __________, made by the pancreas, digests fat droplets after they have been emulsified by __________ into glycerol and three ____________________. These products are rejoined, packaged as lipoprotein droplets and enter the ______________ of the villi. The best conditions for the digestion of egg white indicates that pepsin, water and __________ must be present. 4. A meal rich in protein causes the stomach to release the hormone _________, which causes the stomach to produce gastric juice. Acid in chyme causes the intestinal cells to release __________. Protein and fat stimulate the intestine to release __________. Secretin and CCK cause the pancreas to release pancreatic juice and the __________ bladder to release bile.  Name: ___________________ Date: __________ Blk: _____ Digestion System Worksheet II 1. Digestion of all foods and the absorption of nutrients take place primarily in the __________ __________________. The ___________ receives food and begins the digestion of starch. Food passes between the mouth and the stomach by means of the __________________. The ___________________ allows for mechanical breakdown of food, storage of food, and initial digestion of protein. Water and some vitamins are primarily absorbed in the __________ intestine, and indigestible food remains are defecated at the _________. 2. Label each organ of the digestive system in the diagram below. At the arrows, use the following terms: amino acids, glucose, lipids, or water. 3. The soft palate ends in a cone-shaped projection called the __________________, which helps block the ________________________ during swallowing. The salivary glands produce ___________________ which mixes with food to form a mass called a __________ in preparation for swallowing. 4. Assume the following substances, listed below, were placed into a test tube. In each instance, give an explanation if digestion will or will not occur at a maximal rate. a. pepsin, NaHCO3, water, egg white, warm gently: b. salivary amylase, water, egg white, warm gently: c. pepsin, HCl, water, egg white, freeze: d. pepsin, HCl, water, egg white, warm gently: Matching A. For questions 1-6, match the following answers to each of the statements below. a. pharynx b. soft palate c. esophagus d. stomach e. small intestine f. large intestine _____ 1. helps block food from entering nasopharynx _____ 2. conducts food from pharynx to stomach _____ 3. site where air and food passages cross _____ 4. longest segment of digestive tract _____ 5. transverse colon _____ 6. connects esophagus with duodenum B. For questions 1-6, match the following organs to each of the functions listed below. a. large intestine b. small intestine c. stomach d. pancreas e. liver f. gallbladder _____ 1. secretes digestive enzymes and NaHCO3 _____ 2. releases bile to the duodenum _____ 3. absorption of water and salts _____ 4. absorption of nutrients _____ 5. absorbs alcohol, partially digests protein _____ 6. removes poisonous substances from blood C. For questions 1-5, match the following structural units to one of the organs structures below. a. villi b. gastric glands c. cecum d. uvula e. lobules _____ 1. liver _____ 2. stomach _____ 3. soft palate _____ 4. large intestine _____ 5. duodenum D. For questions 1-6, match the following enzymes to each of the reactions listed below. a. pancreatic amylase b. peptidases c. maltase d. pepsin e. trypsin f. lipase _____ 1. protein + H2O ——> peptides (in intestine) _____ 2. fat droplets + H2O ——> glycerol + 3 fatty acids _____ 3. peptides + H2O ——> amino acids _____ 4. starch + H2O -—> maltose _____ 5. protein + H2O ——> peptides (in stomach) _____ 6. maltose + H2O ——> glucose + glucose E. For questions 1-6, match the following hormones (chemicals) to each of the functions below. a. HCl b. mucus c. gastrin d. secretin e. CCK f. NaHCO3 _____ 1. increases secretory activity of gastric glands _____ 2. increases the pH of chyme in duodenum _____ 3. kills bacteria and activates pepsin _____ 4. released from duodenal cells in presence of fat _____ 5. stimulates pancreas to produce pancreatic juice _____ 6. protects stomach walls from acid F. For questions 1-6, match the following diseases (conditions) to each of the statements listed below. a. ulcer b. obesity c. jaundice d. hepatitis B e. cirrhosis f. mumps _____1. weight more than 20% of the ideal weight _____2. yellowish cast to skin indicating liver problems _____3. open sore in stomach or intestinal wall _____4. viral infection of the liver transmitted by blood _____5. viral infection of parotid gland _____6. fatty liver often caused by excess alcohol