Lec_activity16-and-17_digestive_system

NUR11O1 Integrated Human Anatomy and Physiology Department of Biology Institute of Arts and Sciences Far Eastern University

LECTURE ACTIVITY NO. 16 DIGESTIVE SYSTEM Name: Yda Maxine Palma

Section: 38

Date Submitted: 12/15/2020

I. INTRODUCTION The digestive system is responsible for the breakdown of large organic molecules into smaller molecules that can be absorbed and used by the body. Elimination of wastes is also effectively performed by a functional digestive system.

II. ACCOMPLISH THE ACTIVITY TABLE 1. GUIDE QUESTIONS 16.01A. List the major functions of the digestive system.

16.02A. Describe the general histology of the digestive tract. 16.03A. Describe the structure of a tooth.

16.03B. Describe the major salivary glands. Compare their structures and functions. 16.04A. Outline the anatomical and physiological characteristics of the stomach.

16.04B. Describe the stomach secretions, their functions, and their regulation.

ANSWERS The functions of the digestive system are to take in food, break down the food, absorb the digested molecules, provide nutrients to the body, and eliminate wastes. The digestive tract is composed of four tunics: the mucosa, the submucosa, the muscularis, and a serosa or an adventitia. There are 32 permanent teeth, including incisors, canines, premolars, and molars. Each tooth consists of a crown, a neck, and a root. Saliva helps protect the mouth from oral bacteria, starts starch digestion, and provides lubrication. The stomach connects to the esophagus at the gastroesophageal opening and to the duodenum at the pyloric opening. The wall of the stomach consists of three muscle layers: longitudinal, circular, and oblique. Gastric glands contain mucous neck cells, parietal cells, endocrine cells, and chief cells. Parasympathetic stimulation, gastrin, and histamine increase stomach secretions. During the cephalic phase, the stomach secretions are initiated by the sight, smell, taste, or thought of food. During the gastric phase, partially digested proteins and distention of the stomach promote secretion.

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Biofacultymember2020

NUR11O1 Integrated Human Anatomy and Physiology Department of Biology Institute of Arts and Sciences Far Eastern University

16.04C. Describe gastric movements and stomach emptying and how they are regulated.

16.05A. List the characteristics of the small intestine that account for its large surface area.

16.05B. Describe the secretions and movements that occur in the small intestine.

16.06A. Describe the anatomy, histology, and ducts of the liver and pancreas.

During the intestinal phase, acidic chyme in the duodenum stimulates neuronal reflexes and the secretion of hormones that inhibit gastric secretions by negative-feedback loops. Secretin and cholecystokinin inhibit gastric secretion. Mixing waves mix the stomach contents with the stomach secretions to form chyme. Peristaltic waves move the chyme into the duodenum. Increased motility increases emptying. Distention of the stomach increases gastric motility. Neural and hormonal feedback loops from the duodenum inhibit gastric motility. Cholecystokinin is a major inhibitor of gastric motility. The small intestine is divided into the duodenum, jejunum, and ileum. Circular folds, villi, and microvilli greatly increase the surface area of the intestinal lining. Goblet cells and duodenal glands produce mucus. Mucus protects against digestive enzymes and stomach acids. Chemical or tactile irritation, vagal stimulation, and secretin stimulate intestinal secretion. Peristaltic contractions occur over the length of the intestine and propel chyme through the intestine. Segmental contractions occur over short distances and mix the intestinal contents. The liver consists of four lobes. It receives blood from the hepatic artery and the hepatic portal vein. Branches of the hepatic artery and hepatic portal vein empty into hepatic sinusoids, which empty into a central vein in the center of each lobe. The central veins empty into hepatic veins, which exit the liver. The liver is divided into lobules with portal triads at the corners. Portal triads contain branches of the hepatic portal vein, hepatic artery, and hepatic duct.

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Biofacultymember2020

NUR11O1 Integrated Human Anatomy and Physiology Department of Biology Institute of Arts and Sciences Far Eastern University

16.06B. Describe the major functions of the liver and pancreas, and explain how they are regulated.

16.07A. List the parts of the large intestine, and describe its anatomy and histology.

16.07B. Describe the major functions of the large intestine, and explain how movement is regulated.

Hepatic cords, formed by hepatocytes, form the substance of each lobule. A bile canaliculus, between the cells of each cord, joins the hepatic duct system. Bile leaves the liver through the hepatic duct system. The right and left hepatic ducts join to form the common hepatic duct. The gallbladder stores bile. The cystic duct joins the common hepatic duct to form the common bile duct. The common bile duct joins the pancreatic duct and empties into the duodenum. The pancreas is both an endocrine and an exocrine gland. Its endocrine function is to control blood nutrient levels. Its exocrine function is to produce bicarbonate ions and digestive enzymes. The liver produces bile, which contains bile salts that emulsify fats, and excretory products. The liver stores and processes nutrients, produces new molecules, and detoxifies molecules. The pancreas produces HCO3 and digestive enzymes. Acidic chyme stimulates the release of a watery bicarbonate solution that neutralizes acidic chyme. Fatty acids and amino acids in the duodenum stimulate the release of pancreatic enzymes. The cecum forms a blind sac at the junction of the small and large intestines. The appendix is a blind sac off the cecum. The colon consists of ascending, transverse, descending, and sigmoid portions. The large intestine contains mucus-producing crypts. The rectum is a straight tube that ends at the anal canal. The anal canal is surrounded by an internal anal sphincter (smooth muscle) and an external anal sphincter (skeletal muscle). The functions of the large intestine are feces production and water absorption. Mass movements occur three or four times a day.

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Biofacultymember2020

NUR11O1 Integrated Human Anatomy and Physiology Department of Biology Institute of Arts and Sciences Far Eastern University

16.08A. Describe the digestion, absorption, and transport of carbohydrates, proteins, vitamins, and minerals.

16.08B. Describe the digestion, absorption, and transport of fats and lipids.

16.08C. Discuss water movement into and out of the digestive tract.

16.09A. Describe the effects of aging on the digestive system.

Defecation is the elimination of feces. Reflex activity moves feces through the internal anal sphincter. Voluntary activity regulates movement through the external anal sphincter. Digestion is the chemical breakdown of organic molecules into their component parts. After the molecules are digested, some diffuse through the intestinal wall; others must be transported across the intestinal wall. Polysaccharides are split into disaccharides by salivary and pancreatic amylases. Disaccharides are broken down to monosaccharides by disaccharidases on the surface of the intestinal epithelium. The major monosaccharide, glucose, is absorbed by cotransport with Na+ into intestinal epithelial cells. The transport is driven by gradient generated by the sodium-potassium pump. Glucose is carried by the hepatic portal vein to the liver and enters most cells in the body by facilitated diffusion. Insulin increases the rate of glucose transport into most cells. Bile salts emulsify lipids. Lipase breaks down lipids. The breakdown products aggregate with bile salts to form micelles. Micelles come in contact with the intestinal epithelium, and their contents diffuse into the cells, where they are packaged and released into the lacteals. Lipids are stored in adipose tissue and in the liver, both of which release the lipids into the blood when energy sources are needed elsewhere in the body. Water can move across the intestinal wall in either direction, depending on osmotic conditions. Approximately 99% of the water entering the intestine is absorbed. Most minerals are actively transported across the wall of the small intestine. With advancing age, the layers of the digestive tract thin, and the blood supply decreases. Mucus secretion and motility also decrease in the digestive tract. The defenses of the

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NUR11O1 Integrated Human Anatomy and Physiology Department of Biology Institute of Arts and Sciences Far Eastern University

17.01A. Define nutrition, essential nutrient, and kilocalorie.

17.01B. For carbohydrates, lipids, and proteins, describe their dietary sources, their uses in the body, and the daily recommended amounts of each in the diet.

digestive tract decline, leaving it more sensitive to infection and the effects of toxic agents. Tooth enamel becomes thinner, and the gingiva recede, exposing dentin, which may become painful and affect eating habits. Nutrients, the chemicals used by the body, consist of carbohydrates, lipids, proteins, vitamins, minerals, and water. Essential nutrients either cannot be produced by the body or cannot be produced in adequate amounts. A kilocalorie is the energy required to raise the temperature of 1000 g of water 1°C. A kilocalorie (Calorie) is the unit of measurement used to express the energy content of food. Carbohydrates include monosaccharides, disaccharides, and polysaccharides. Most of the carbohydrates we ingest are from plants. Carbohydrates are used as an energy source and for making DNA, RNA, and ATP. The Acceptable Macronutrient Distribution Range (AMDR) for carbohydrates is 45–65% of total kilocalories. Lipids include triglycerides, steroids, phospholipids, and fat-soluble vitamins. Triglycerides are a major source of energy. Eicosanoids are involved in inflammation, tissue repair, and smooth muscle contraction. Cholesterol and phospholipids are part of the cell membrane. Some steroid hormones regulate the reproductive system. The AMDR for lipids is 20–35%. Proteins are chains of amino acids. Animal proteins tend to be complete proteins, whereas plant proteins tend to be incomplete. Proteins are involved in structural strength, muscle contraction, regulation, buffering, clotting, transport, ion channels, receptors, and the immune system. The AMDR for protein is 10–35% of total kilocalories.

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Biofacultymember2020

NUR11O1 Integrated Human Anatomy and Physiology Department of Biology Institute of Arts and Sciences Far Eastern University

17.01C. List the common vitamins and minerals, and give a function for each.

17.02A. Define metabolism, anabolism, and catabolism.

Most vitamins are not produced by the body and must be obtained in the diet. Some vitamins can be formed from provitamins. Vitamins are important in energy production, nucleic acid synthesis, growth, and blood clotting. Vitamins are classified as either fatsoluble or water-soluble. Recommended dietary allowances (RDAs) are a guide for estimating the nutritional needs of groups of people on the basis of their age, their gender, and other factors. Daily Values are dietary references that can be used to plan a healthful diet. Daily Values for vitamins and minerals are based on Reference Daily Intakes (RDIs), which are generally the highest 1968 RDA value of an age category. Daily Values are based on Daily Reference Values. The Daily Reference Values for energy-producing nutrients (carbohydrates, total fat, saturated fat, and proteins) and dietary fiber are recommended percentages of the total kilocalories ingested daily for each nutrient. The Daily Reference Values for total fats, saturated fats, cholesterol, and sodium are the uppermost limits considered desirable because of their link to diseases. The % Daily Value is the percentage of the recommended Daily Value of a nutrient found in one serving of a particular food. Metabolism consists of catabolism and anabolism. Catabolism, the breakdown of molecules, gives off energy. Anabolism, the synthesis of molecules, requires energy. The energy in carbohydrates, lipids, and proteins is used to produce ATP. The energy from ATP can be used for active transport, muscle contraction, and the synthesis of molecules.

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Biofacultymember2020

NUR11O1 Integrated Human Anatomy and Physiology Department of Biology Institute of Arts and Sciences Far Eastern University

17.02B. List three ways in which enzyme activity is controlled.

17.02C. Describe glycolysis and name its products.

17.02D. Describe the citric acid cycle and its products.

17.02E. Describe the electron-transport chain and how ATP is produced in the process.

17.02F. Explain how the breakdown of glucose yields 2 ATP molecules in anaerobic respiration and 38 ATP molecules in aerobic respiration.

1. Enzyme synthesis. Enzymes are proteins, and their synthesis depends on DNA. Thus, the types and amounts of enzymes present in cells are under genetic control. 2. Receptor-mediated enzyme activity. The combination of a chemical signal, such as a neurotransmitter or hormone, with a membrane-bound or intracellular receptor can activate or inhibit enzyme activity 3. Product control of enzyme activity. The end product of a biochemical pathway can inhibit the enzyme responsible for the first reaction in the pathway. This negativefeedback regulation prevents accumulation of the intermediate products and the end product of the pathway. Glycolysis is a cytoplasmic pathway which breaks down glucose into two three-carbon compounds and generates energy. Glycolysis is used by all cells in the body for energy generation. The final product of glycolysis is pyruvate in aerobic settings and lactate in anaerobic conditions. The citric acid cycle is a series of reactions that produces two carbon dioxide molecules, one GTP/ATP, and reduced forms of NADH and FADH2. The proton gradient produced by proton pumping during the electron transport chain is used to synthesize ATP. Protons flow down their concentration gradient into the matrix through the membrane protein ATP synthase, causing it to spin (like a water wheel) and catalyze conversion of ADP to ATP. Without oxygen, organisms can split glucose into just two molecules of pyruvate. This releases only enough energy to make two ATP molecules. With oxygen, organisms can break down glucose all the way

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Biofacultymember2020

NUR11O1 Integrated Human Anatomy and Physiology Department of Biology Institute of Arts and Sciences Far Eastern University

17.02G. Describe the basic steps involved in using lipids and amino acids as energy sources.

17.02H. Differentiate between the absorptive and postabsorptive metabolic states.

17.02I. Define metabolic rate. 17.03A. Describe heat production and regulation in the body.

to carbon dioxide. This releases enough energy to produce up to 38 ATP molecules. 1. Lipids are broken down in adipose tissue, and fatty acids are released into the blood. 2. Fatty acids are taken up by cells and broken down into acetyl-CoA, which can enter the citric acid cycle. Acetyl-CoA can also be converted into ketones by the liver. Ketones released from the liver into the blood are used as energy sources by other cells. The absorptive state of metabolism lasts for about four hours, during and after each meal. Throughout this state, digested food is converted into sugar or glucose. During the postabsorptive state, the digestive tract is empty and energy comes from the breakdown of the body's reserves. The metabolic rate is the total energy expenditure per unit of time. Body temperature is a balance between heat gain and heat loss. Heat is produced through metabolism. Heat is exchanged through radiation, conduction, convection, and evaporation. The greater the temperature difference, the greater the rate of heat exchange. Body temperature is maintained around a set point by neural circuits in the hypothalamus. Dilation of blood vessels in the skin and sweating increase heat loss from the body. Constriction of blood vessels in the skin and shivering promote heat gain by the body.

III. CONCLUSION: Make general statement (Maximum of three sentences on what you have learned on this activity. It is extremely important for us to know the ins and outs of how our digestive system works alongside nutrition. This is so we can maintain a healthily body functions and maintain homeostasis.

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