Chapter 6 life processes 1 (introduction, nutrition and digestion)


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Chapter 6 life processes 1 (introduction, nutrition and digestion)

  1. 1.
  2. 2. LIFE PROCESSES Looking at living things
  3. 3. Living things  Although all living things look different from each other, they all have seven things in common.  These seven things are called life processes.  Something is only alive if it does all seven processes.
  5. 5. 1 All living things move
  6. 6.  Animals move their whole bodies to get from one place to another.  Plants turn towards the light and their roots grow down into the soil.
  7. 7. 2 All living things reproduce
  8. 8.  Animals have babies.  New plants grow from seeds.
  9. 9. 3 All living things are sensitive
  10. 10.  All living things respond to changes. Living things notice changes in their surroundings and react to them.  Eg. Plants grow towards the light.  Eg. People react to the temperature around them.
  11. 11. 4 All living things need nutrition
  12. 12.  Food is used to provide energy.  Green plants make their own food using sunlight.  Animals eat plants or other animals.
  13. 13. 5 All living things excrete
  14. 14.  Waste substances must be removed from the body.  Plants and animals both need to get rid of waste gas and water.
  15. 15. 6 All living things respire
  16. 16.  Plants and animals use the oxygen in the air to turn food into energy.
  17. 17. 7 All living things grow
  18. 18.  Babies grow into adults.  Seedlings grow into plants.
  19. 19. The seven life processes 1 Move 2 Reproduce 3 Sensitive 4 Nutrition 5 Excrete 6 Respire 7 Grow
  20. 20. Use the first letter from each process to help you remember them. Move Reproduce Sensitive Nutrition Excrete Respire Grow They spell MRS NERG
  21. 21. This is MRS NERG ! Can you remember what each of the letters in her name stand for ?
  22. 22. Move Reproduce Sensitive Nutrition Excrete Respire Grow
  23. 23. Well done !
  24. 24. Nutrients :- The components of food like carbohydrates, fats, proteins vitamins and minerals are called nutrients. Nutrients help living organisms :- i) To build their bodies. ii) To grow. iii) To repair the damaged parts of their bodies. iv) To provide energy to carry out life processes.
  25. 25. The mode of taking food by an organism and its utilization in the body is called nutrition. Modes of nutrition :- There are two main modes of nutrition in living organisms. They are autotrophic nutrition and heterotrophic nutrition. i) Autotrophic nutrition :- is nutrition in which organisms can prepare their own food. Organisms which can prepare their own food are called autotrophs. ii) Heterotrophic nutrition :- is nutrition in which organisms get their food directly or indirectly from plants. Organisms which get their food directly or indirectly from plants are called heterotrophs. nutrition
  26. 26. What is photosynthesis?  Plants make their own food. This process is called photosynthesis.
  27. 27. Where does photosynthesis occur?  Photosynthesis occurs in the leaves of a plant.
  28. 28. What is needed for photosynthesis to occur?  Light is needed for photosynthesis to occur. The plant’s leaves use the light to make a sugar called glucose.
  29. 29. Why do plants need glucose?  Glucose is the food for the plant. It gives the plant energy to grow.
  30. 30. How much glucose does a plant make?  Plants make enough glucose to be used during the night and on cloudy days when they don’t get sunlight. The extra glucose is stored in the plant’s leaves and other parts.
  31. 31. How does photosynthesis help us?  During the process of photosynthesis, oxygen is produced. We use this oxygen to breathe.
  32. 32. Photosynthesis - Food making process in plants :- Photosynthesis is the process by which plants prepare their own food by using sunlight, water, carbon dioxide and chlorophyll. Photosynthesis take place in the leaves. i) Sunlight is obtained from the sun. ii) Water is absorbed by the roots and transported to the leaves. iii) Carbon dioxide is taken from the air through small pores in the leaves called stomata. iv) Chlorophyll are the green pigments present in the leaves.
  33. 33. Chlorophyll uses the energy from sunlight to prepare food by using water and carbon dioxide. The food prepared is carbohydrate which is then converted into starch. During photosynthesis oxygen is released. Equation of photosynthesis :- Sunlight Carbon dioxide + Water Carbohydrate + Oxygen Chlorophyll
  34. 34. Synthesis of proteins :- The soil has some bacteria which convert nitrogen from the air into usable nitrogen in the soil. Farmers also add fertilisers containig nitrogen into the soil. Plants absorb this nitrogen from the soil along with water and other constituents to prepare proteins and fats.
  35. 35. Outline I. Photosynthesis A. Introduction B. Reactions II. Cellular Respiration A. Introduction B. Reactions
  36. 36. Photosynthesis  Method of converting sun energy into chemical energy usable by cells  Autotrophs: self feeders, organisms capable of making their own food – Photoautotrophs: use sun energy e.g. plants photosynthesis-makes organic compounds (glucose) from light – Chemoautotrophs: use chemical energy e.g. bacteria that use sulfide or methane chemosynthesis-makes organic compounds from chemical energy contained in sulfide or methane
  37. 37. Photosynthesis  Photosynthesis takes place in specialized structures inside plant cells called chloroplasts – Light absorbing pigment molecules e.g. chlorophyll
  38. 38. Overall Reaction  6CO2 + 12 H2O + light energy → C6H12O6 + 6O2+ 6H2O  Carbohydrate made is glucose  Water appears on both sides because 12 H2O molecules are required and 6 new H2O molecules are made  Water is split as a source of electrons from hydrogen atoms releasing O2 as a byproduct  Electrons increase potential energy when moved from water to sugar therefore energy is required
  39. 39. Light-dependent Reactions  Overview: light energy is absorbed by chlorophyll molecules-this light energy excites electrons and boosts them to higher energy levels. They are trapped by electron acceptor molecules that are poised at the start of a neighboring transport system. The electrons “fall” to a lower energy state, releasing energy that is harnessed to make ATP
  40. 40. Energy Shuttling  Recall ATP: cellular energy-nucleotide based molecule with 3 phosphate groups bonded to it, when removing the third phosphate group, lots of energy liberated= superb molecule for shuttling energy around within cells.  Other energy shuttles-coenzymes (nucleotide based molecules): move electrons and protons around within the cell NADP+, NADPH NAD+, NADP FAD, FADH2
  41. 41. Light-dependent Reactions  Photosystem: light capturing unit, contains chlorophyll, the light capturing pigment  Electron transport system: sequence of electron carrier molecules that shuttle electrons, energy released to make ATP  Electrons in chlorophyll must be replaced so that cycle may continue-these electrons come from water molecules, Oxygen is liberated from the light reactions  Light reactions yield ATP and NADPH used to fuel the reactions of the Calvin cycle (light independent or dark reactions)
  42. 42. Calvin Cycle (light independent or “dark” reactions)  ATP and NADPH generated in light reactions used to fuel the reactions which take CO2 and break it apart, then reassemble the carbons into glucose.  Called carbon fixation: taking carbon from an inorganic molecule (atmospheric CO2) and making an organic molecule out of it (glucose)  Simplified version of how carbon and energy enter the food chain
  43. 43. Harvesting Chemical Energy  So we see how energy enters food chains (via autotrophs) we can look at how organisms use that energy to fuel their bodies.  Plants and animals both use products of photosynthesis (glucose) for metabolic fuel  Heterotrophs: must take in energy from outside sources, cannot make their own e.g. animals  When we take in glucose (or other carbs), proteins, and fats-these foods don’t come to us the way our cells can use them
  44. 44. Cellular Respiration Overview  Transformation of chemical energy in food into chemical energy cells can use: ATP  These reactions proceed the same way in plants and animals. Process is called cellular respiration  Overall Reaction: – C6H12O6 + 6O2 → 6CO2 + 6H2O
  45. 45. Cellular Respiration Overview  Breakdown of glucose begins in the cytoplasm: the liquid matrix inside the cell  At this point life diverges into two forms and two pathways – Anaerobic cellular respiration (aka fermentation) – Aerobic cellular respiration
  46. 46. C.R. Reactions  Glycolysis – Series of reactions which break the 6-carbon glucose molecule down into two 3-carbon molecules called pyruvate – Process is an ancient one-all organisms from simple bacteria to humans perform it the same way – Yields 2 ATP molecules for every one glucose molecule broken down – Yields 2 NADH per glucose molecule
  47. 47. Anaerobic Cellular Respiration  Some organisms thrive in environments with little or no oxygen – Marshes, bogs, gut of animals, sewage treatment ponds  No oxygen used= ‘an’aerobic  Results in no more ATP, final steps in these pathways serve ONLY to regenerate NAD+ so it can return to pick up more electrons and hydrogens in glycolysis.  End products such as ethanol and CO2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)
  48. 48. Aerobic Cellular Respiration  Oxygen required=aerobic  2 more sets of reactions which occur in a specialized structure within the cell called the mitochondria – 1. Kreb’s Cycle – 2. Electron Transport Chain
  49. 49. Kreb’s Cycle  Completes the breakdown of glucose – Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen atoms end up in CO2 and H2O – Hydrogens and electrons are stripped and loaded onto NAD+ and FAD to produce NADH and FADH2  Production of only 2 more ATP but loads up the coenzymes with H+ and electrons which move to the 3rd stage
  50. 50. Electron Transport Chain  Electron carriers loaded with electrons and protons from the Kreb’s cycle move to this chain-like a series of steps (staircase).  As electrons drop down stairs, energy released to form a total of 32 ATP  Oxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water
  51. 51. Energy Tally  36 ATP for aerobic vs. 2 ATP for anaerobic – Glycolysis 2 ATP – Kreb’s 2 ATP – Electron Transport 32 ATP 36 ATP  Anaerobic organisms can’t be too energetic but are important for global recycling of carbon
  52. 52. Other modes of nutrition in plants :- Parasitic plants :- are plants which do not have chlorophyll and cannot prepare their own food. They get their food from other plants called host . Eg :- Cuscuta ( Amarbel)
  53. 53. Insectivorous plants :- are plants which feed on insects. Eg:- Pitcher plant. The leaf of the pitcher plant is modified into a pitcher. The end of the pitcher has a lid which can open and close. When an insect enters the pitcher, the lid closes. The insect is then digested by digestive juices inside the pitcher. Other example is Venus flytrap, Nepenthes, Serracenia and Cephalotus
  54. 54. Saprotrophs :- are plants which do not have chlorophyll and cannot prepare their on food. They get their food from dead and decaying organic matter. Eg :- mushroom, bread mould etc. They produce digestive juice on the dead and decaying organic matter and convert it into a solution and then absorb the nutrients from the solution.
  55. 55. Symbiotic relationship :- Some plants live together and share shelter and nutrients. Eg :- lichens. In lichens, an alga and a fungus live together. The fungus provides shelter, water and minerals to the alga. The alga provides food to the fungus which it prepares by photosynthesis.
  56. 56. How food is absorbed? Mechanisms for the movement of nutrients into a body system
  57. 57. Types of Nutritional Gain  Holozoic nutrition  method by which humans and other mammals feed  Saprotrophic nutrition  method by which fungi and many prokaryotes feed  Parasitic nutrition  method of feeding which has evolved in many different groups of organisms, including various kinds of worms and fungi and a few plants.
  58. 58. Cellular Structure
  59. 59. Glucose  indirect active transport  involving the co- transport of sodium ions.  Then facilitated diffusion and simple diffusion ,into the tissue fluid inside the villus and then into blood capillary.
  60. 60. Amino-acids In a fetus a newly born baby , some entire undigested proteins can be absorbed by pinocytosis.  This is how babies are able to absorb some of their mother’s antibodies from the milk. This can also happen to a small extent in adults. Absorbed into the villus cells by active transport and pass out of the opposite side by diffusion.
  61. 61. Fatty acids and glycerol  Easily absorbed across the cell surface membrane of the villus by simple diffusion.  Once inside the cells, they are taken to the smooth endoplasmic reticulum, then to the Golgi apparatus, where they are surrounded in a coat of protein.  These tiny structures ranging from 100 to 600nm in diameter ,are moved out of the villus by exocytosis.  Too big for blood so they absorb into the lymph inside the lacteals from a milky emulsion, which is what gives these structures their name.  (‘Lact’ means ‘to do with milk’).
  62. 62. Vitamins  Absorbed in the small intestine  The fat-soluble vitamins A, D, and E can simply cross the cell surface membranes by diffusion  The water –soluble vitamins, such as vitamin C and the many types of B vitamins are moved across the cells surface membranes by specific transport.  Vitamin B can only be adsorbed in combination with intrinsic factor.
  63. 63. Water and Inorganic Ions  Considerable amounts of sodium, chloride, calcium, and irons are also adsorbed in small intestine  Calcium is helped by the presence of vitamin D.  Iron is helped by citrate ions and ascorbic acid, both of which is found in citrus fruits.  Why fresh fruits and vegetables in the diet can help to prevent anemia.  On the other hand, drinking to much tea can hinder irons absorption, because tannins in the tea react with irons to produce compounds which cannot be adsorbed.
  64. 64. Digestion Overview
  65. 65. Organic Molecule Pathways
  66. 66. Liquid vs. Pill
  67. 67. Liquid vs. Pill
  68. 68. Liquid vs. Pill
  69. 69. Liquid vs. Pill
  70. 70. Liquid vs. Pill
  71. 71. Liquid vs. Pill
  72. 72. Liquid vs. Pill
  73. 73. Liquid vs. Pill
  74. 74. Liquid vs. Pill Vitamin Filtering Begins
  75. 75. Liquid vs. Pill Pill Vitamin Looses 0.8 Ounces In Filtering Process
  76. 76. Liquid vs. Pill Liquid Vitamin Looses 0.2 Ounces In Filtering Process
  77. 77. Liquid vs. Pill Pill PillLiquid Liquid
  78. 78. Nutrient Requirements • Humans require eight essential amino acids. • All are available in milk, eggs, or meat, but not in all vegetables. • Thus, vegetarians must eat a mix of foods.
  80. 80. Heterotrophic Nutrition: When an organism takes food from another organism, it is called heterotrophic nutrition. Different heterotrophic organisms follow different methods to take and utilize food. Based on this, heterotrophic nutrition can be divided into two types:
  81. 81. (a) Saprophytic Nutrition: In saprophytic nutrition, the digestion of food takes place before ingestion of food. This type of nutrition is usually seen in fungi and some other microorganisms. The organism secretes digestive enzymes on the food and then ingests the simple substances. Saprophytes feed on dead materials and thus help in decomposition dead remains of plants and animals.
  82. 82. (b) Holozoic Nutrition: In holozoic nutrition, the digestion of food follows after the ingestion of food. Thus, digestion takes place inside the body of the organism. Holozoic nutrition happens in five steps, viz. ingestion, digestion, absorption, assimilation and egestion.
  83. 83. • Describe the functions of main regions of the alimentary canal and the associated organs: mouth, salivary glands, oesophagus, stomach, duodenum, pancreas, gall bladder, liver, ileum, colon, rectum, anus, in relation to ingestion, digestion, absorption, assimilation and egestion of food, as appropriate. • Functions of a typical amylase, protease and lipase (listing the substrate and end-products)
  84. 84.  Holozoic nutrition: feeding on ready- made complex organic matter.
  85. 85.  The taking in of food (chemical energy) by the body & converting it into living matter
  86. 86. INGESTION DIGESTION ABSORPTION ASSIMILATION EGESTION Taking in food Breakdown of complex food substances into smaller soluble food substances Digested food is absorbed Into body cells Absorbed food is use to provide energy or form new protoplasm Removal of undigested food 5 processes in digestion
  87. 87.  Feeding/ Ingestion – intake of food into the mouth.
  88. 88.  Digestion – large food molecules are broken down into small, soluble and diffusible molecules.  2 types: Physical and chemical digestions
  89. 89. 1. Physical digestion refers to the mechanical break up of food into small particles which increases its surface area for chemical digestion. (E.g. Chewing, stomach churning). It also mix the digestive enzymes with the food particles
  90. 90. 1. Chemical digestions – breaking of biomolecules like proteins, starch and fats into small soluble molecules which can be absorbed by the cells. It involves digestive enzymes and chemical reactions like hyrolysis.
  91. 91. Why must food molecules be broken down into smaller, simpler forms before it can be absorbed by the cells for other uses? Cell membranes are partially permeable and only allow small molecules to pass through.
  92. 92.  Absorption – digested food materials are taken into the body cells.
  93. 93.  Assimilation – absorbed food materials are converted into new protoplasm or used to provide energy.
  94. 94.  Egestion – elimination of undigested food materials (faeces) Do not confuse Ingestion with Egestion!!!
  95. 95. Starch Proteins PROTEASE Lipids/ Fats AMYLASE LIPASE fatty acids & glycerol amino acids maltose
  96. 96. The Digestive System Consists of: 1) The gut or alimentary canal (9 m) from mouth to anus. 2) Glands (A cell, tissue, or organ that secretes a chemical substance). 3) Associated organs.
  97. 97. Mouth & Buccal Cavity
  98. 98. Buccal Cavity
  99. 99. 1. Food enters through the mouth. This process is called ingestion. 2. Teeth cuts food into small pieces. This increases surface area to volume ratio for enzyme to act more efficiently.
  100. 100. 1. Salivary glands produce saliva to moisten food. 2. Saliva also contains salivary amylase to break down starch to maltose. 3. pH of saliva is neutral (around pH 7).
  101. 101. Salivary Glands
  102. 102. Starch Maltose Salivary Amylase Salivary amylase is active at pH 7.
  103. 103. 1. Tongue rolls food into boli. 2. Food is swallowed and enters the pharynx.
  104. 104. • Made up of a tubular gut called the alimentary canal. • Food travels through our body along the alimentary canal which is a continuous tube beginning at the mouth and ending at the anus. • The parts of the gut includes: mouth, pharynx, oesophagus, stomach, small intestine, large intestine and anus. mouth stomach oesophagus small intestine pharynx large intestine anus Rectum
  105. 105.  Mouth & salivary glands  Pharynx, Oesophagus  Stomach  Small intestine- duodenum & ileum  Associated organs-liver, gall bladder, pancreas  Large intestine- colon, rectum  Anus
  106. 106. mouth stomach oesophagus duodenum pharynx colon/ large intestine anus liver gall bladder pancreas ileum rectum jejunum salivary gland
  107. 107. • Nutrition (Definition) • 5 Processes of Nutrition • Digestive Enzymes • Alimentary Canal • Alimentary Canal & Accessory Organs What we learn today.
  108. 108. liver gall bladder pancreas ileum rectum jejunum salivary gland colon/ large intestine anus duodenum oesophagus mouth pharynx stomach
  109. 109. GI (gastrointestinal) tract = alimentary canal
  110. 110.  Digestion is the breakdown of large, complex organic molecules into smaller components that can be used by the body.  Molecules need to be small enough to diffuse across plasma membranes.
  111. 111.  Ingestion – this is the consumption of or taking in of nutrients.  Digestion – the chemical breakdown of large organic molecules into smaller components by enzymes.  Absorption – the transport or delivery of digested nutrients to body tissues.  Assimilation – absorbed food materials are converted into new protoplasm or used to provide energy.  Egestion – the elimination of food waste materials from the body.
  112. 112.  Food enters the human digestive tract through the mouth or oral cavity.  Humans are considered chunk feeders because they consume chunks of food that are then mechanically broken down.
  113. 113.  The human digestive tract is often referred to as the alimentary canal.  The alimentary canal of a normal adult is approximately 6.5 to 9 meters long.
  114. 114.  Mouth ◦ mechanical digestion  teeth  breaking up food ◦ chemical digestion  saliva  amylase  enzyme digests starch  mucin  slippery protein (mucus)  protects soft lining of digestive system  lubricates food for easier swallowing  buffers  neutralizes acid to prevent tooth decay  anti-bacterial chemicals  kill bacteria that enter mouth with food
  115. 115.  Physical breakdown of food begins with the teeth grinding the food and increasing its surface area. An increase surface area allows for easier chemical digestion  Bacteria living in the mouth can feed off of nutrients sticking to the teeth and cause tooth decay.
  116. 116.  Saliva is released from the salivary glands and begins chemical digestion of starches. Saliva contains the enzyme salivary amylase which breaks down starches into simpler carbohydrates.
  117. 117.  As the food particles dissolve in the saliva they penetrate the cells of the taste buds located on the tongue and cheeks.  Humans can differentiate between sweet, sour, salty and bitter.
  118. 118.  Saliva also lubricates the food and helps to form a bolus, the ball of food that is swallowed.
  119. 119.  The bolus of food moves down the esophagus propelled by wave-like muscular contractions known as peristalsis.  Peristalsis moves food all the way through the gastrointestinal tract.
  120. 120. mouth break up food digest starch kill germs moisten food
  121. 121.  Chemical and mechanical digestion.  Food is chewed (masticated) mechanically.  A bolus (lump) is formed with saliva and the tongue.
  122. 122. Food is taken into the body through the mouth. This process is called ingestion. In the mouth the food is broken down into smaller pieces by the teeth. The mouth has salivary glands which secrete saliva. The saliva breaks down starch into sugars. The tongue helps to mix the food with saliva and swallow the food.
  123. 123. Babies do not have teeth. Humans grow two sets of teeth. The first set of teeth begins to grow during infancy. This set of teeth is called milk teeth. These fall off between the ages of six and eight. The second set of teeth, which replaces the milk teeth, is called the permanent teeth. This set lasts throughout our life, unless it falls off during old age. Teeth help in breaking down the food into smaller particles so that swallowing of food becomes easier. There are four types of teeth in human beings. They are incisors, canines, permolars and molars.
  124. 124.  The incisor teeth are used for cutting the food.  The canine teeth are used for tearing the food and for cracking hard substances.  The premolars are used for coarse grinding of food.  The molars are used for fine grinding of food.  Number of teeth Type of teeth Lower jaw Upper jaw Total Incisors 4 4 8 Canines 2 2 4 Premolars 10 10 20 molars
  125. 125. Dental Formula  Dental formula for milk teeth in humans is 2120/2120. It means that each half of upper jaw and lower jaw has 2 incisors, 1 canine and 2 premolars. Molars are absent in milk teeth. There are 20 teeth in the milk teeth set.  Dental formula for permanent teeth in human is 2123/2123. It means that each half of upper jaw and lower jaw has 2 incisors, 1 canine, 2 premolars, and 3 molars.  The dental formula in dogs (carnivore) is 3142/3143  The dental formula in rabbits (herbivore) is 2033/1023
  126. 126. Structure of Tooth The vertical section of tooth shows the following parts • The crown − the part lying above the gums • The neck − it connects the crown with the root • The root − it lies buried inside the gums and supports the tooth The white part of the tooth is called the enamel, it consists of calcium salts. Inner to the enamel is the dentine which is a solid tissue and contains strands of cytoplasm in it. The dentine encloses a cavity known as the pulp cavity. This cavity supplies the tooth with nerves and blood capillaries. At the root of the tooth is a bone like material called the cement which holds the tooth firmly to the socket.
  127. 127. Tooth decay A number of bacteria are present in our mouth, though not all of them are harmful. However, irregular and improper cleaning of teeth can lead to the growth of several harmful bacteria in our mouth. These bacteria break down the sugar present in leftover food particles and release acids in the mouth, which damage the teeth. This is known as tooth decay. This condition can lead to severe toothache. It can also result in untimely loss of teeth. Tooth decay can occur because of consuming chocolates, sweets, cold drinks, and other sugar products.
  128. 128. How can tooth decay be prevented? Tooth decay can be prevented by maintaining oral hygiene, which includes the proper cleaning of teeth. Teeth must be brushed twice a day after meals using dantun or dental floss.
  129. 129. The tongue has taste buds to detect different tastes of food. The different regions of the tongue detect different tastes.
  130. 130.  Epiglottis ◦ flap of cartilage ◦ closes trachea (windpipe) when swallowing ◦ food travels down esophagus  Peristalsis ◦ involuntary muscle contractions to move food along
  131. 131. 1. Chewing a saltine? - 2. Saliva breaking the saltine down into molecules of glucose? - 3. Your tongue breaking pieces of a hamburger apart? 4. Pepsin (an enzyme) in your stomach breaking the hamburger into amino acids?
  132. 132.  The back of the throat.  Larynx- passage for air, closes when we swallow.  Is approximately 15cm long.
  133. 133.  Groups of specialized secretory cells.  Found in the lining of the alimentary canal or accessory organs.
  134. 134.  series of involuntary wave-like muscle contractions which move food along the digestive tract Peristalsis
  135. 135.  The stomach acts as a temporary storage site for food. Food usually spends about 4 hours in the stomach. It has ridges which allow it to expand to store about 1.5 litres of food.  The stomach is also the site of initial protein digestion.
  136. 136.  Movement of food into and out of the stomach is controlled by circular muscles known as sphincters.  One at the top of the stomach allows food from the esophagus to enter and prevents food from going back up into the esophagus.  Another located at the bottom slowly releases partially digested food into the small intestine. The partially digested food is called chyme.
  137. 137.  Millions of cells lining the stomach secrete various fluids known collectively as gastric fluids.  Gastric fluid consists of mucus, hydrochloric acid, pepsinogens and other substances.  Mucus coats and protects the lining of the stomach. Hydrochloric acid kills any harmful substances that have been ingested and it also converts pepsinogen into pepsin.  Pepsin is a protein digesting enzyme that breaks large protein chains into smaller chains.
  138. 138.  The pH environment of the stomach normally ranges between 2.0 and 3.0 on the pH scale.  The high acidity allows pepsin to work and makes the HCL effective at killing pathogens
  139. 139.  An stomach ulcer is a lesion in the lining of the stomach. It occurs when the protective mucus lining breaks down and the cell membranes are exposed to the HCl and pepsin  Most stomach ulcers are linked to the bacterium shown on the right known as Heliobacter pylori.
  140. 140.  An endoscope (shown on the right) can be used to view things such as stomach ulcers or as shown below, a tumor growing in the large intestine.  The endoscope can also extract small pieces of tissue for a biopsy.
  141. 141.  Food is temporarily stored here.  Gastric juices are secreted.  Has layers of muscle that line the inside.  Mechanically and chemically breaks down food.
  142. 142.  Functions ◦ food storage  can stretch to fit ~2L food ◦ disinfect food  HCl = pH 2  kills bacteria ◦ chemical digestion  pepsin  enzyme breaks down proteins But the stomach is made out of protein! What stops the stomach from digesting itself? mucus secreted by stomach cells protects stomach lining
  143. 143. stomach kills germs break up food digest proteins store food sphincter sphincter mouth break up food digest starch kill germs moisten food
  144. 144.  Secreted by the stomach.  Acidic (pH 1.5-2.5) (HCl).  Pepsin- an enzyme that breaks down large proteins into amino acids.  Food is further broken down into a thin liquid called chyme.
  145. 145. Pancreas Gall Bladder Spleen
  146. 146.  Pouch structure located near the liver which concentrates and stores bile  Bile duct – a long tube that carries BILE. The top half of the common bile duct is associated with the liver, while the bottom half of the common bile duct is associated with the pancreas, through which it passes on its way to the intestine.
  147. 147.  Bile emulsifies lipids (physically breaks apart FATS)  Bile is a bitter, greenish-yellow alkaline fluid, stored in the gallbladder between meals and upon eating is discharged into the duodenum where it aids the process of digestion.
  148. 148.  An organ which secretes both digestive enzymes (exocrine) and hormones (endocrine)  ** Pancreatic juice digests all major nutrient types.  Nearly all digestion occurs in the small intestine & all digestion is completed in the SI.
  149. 149.  Digestive enzymes ◦ digest proteins  trypsin, chymotrypsin ◦ digest starch  amylase  Buffers ◦ neutralizes acid from stomach
  150. 150.  Function ◦ produces bile  bile stored in gallbladder until needed  breaks up fats  act like detergents to breakup fats bile contains colors from old red blood cells collected in liver = iron in RBC rusts & makes feces brown
  151. 151. pancreas produces enzymes to digest proteins & starch stomach kills germs break up food digest proteins store food mouth break up food digest starch kill germs moisten food liver produces bile - stored in gall bladder break up fats
  152. 152.  The intestines are named for their diameter, not length.  The small intestine is up to 7 m in length but only 2.5 cm in diameter.  The large intestine is only 1.5 m in length but 7.6 cm in diameter.
  153. 153.  In mammals the length of the small intestine is directly related to their diet.  Due to the fact that meats are easier to digest than plant materials, carnivores (lion) will have a shorter intestine than herbivores (rabbit). The length of the digestive tract of omnivores falls somewhere in the middle.
  154. 154.  The majority of chemical digestion occurs in the first of three sections of the small intestine known as the duodenum.  This section also contains an opening from the bile duct and pancreatic duct through which bile and pancreatic enzymes enter the small intestine.
  155. 155.  Food enters the small intestine as a semi-solid mixture known as chyme. The chyme is acidic due to the HCl in the stomach so it needs to be neutralized.  The presence of chyme in the small intestine triggers the conversion of prosecretin into secretin which is absorbed into the blood stream and carried to the pancreas
  156. 156.  Most chemical digestion takes place here.  Simple sugars and proteins are absorbed into the inner lining.  Fatty acids and glycerol go to lymphatic system.  Lined with villi, which increase surface area for absorption, one cell thick.
  157. 157.  Function ◦ chemical digestion  major organ of digestion & absorption ◦ absorption through lining  over 6 meters!  small intestine has huge surface area = 300m2 (~size of tennis court)  Structure ◦ 3 sections  duodenum = most digestion  jejunum = absorption of nutrients & water  ileum = absorption of nutrients & water
  158. 158.  1st section of small intestines ◦ acid food from stomach ◦ mixes with digestive juices from:  pancreas  liver  gall bladder
  159. 159. stomach kills germs break up food digest proteins store food mouth break up food digest starch kill germs moisten food pancreas produces enzymes to digest proteins & starch
  160. 160.  Much absorption is thought to occur directly through the wall without the need for special adaptations  Almost 90% of our daily fluid intake is absorbed in the small intestine.  Villi - increase the surface area of the small intestines, thus providing better absorption of materials
  161. 161.  Absorption through villi & microvilli ◦ finger-like projections ◦ increase surface area for absorption
  162. 162.  The pancreas is an accessory organ of the digestive system. It releases chemicals to aid in digestion.  Secretin will stimulate the pancreas to release a solution containing bicarbonate ion into the small intestine where it will neutralize the acidic chyme and raise the pH from 2.5 to 9.0. This inactivates the pepsin.
  163. 163.  The pancreas also releases digestive enzymes that break down the three macromolecules: carbohydrates, lipids and proteins.
  164. 164.  Trypsinogen, a protein- digesting enzyme is released into the small intestine where it is convertes into trypsin and it breaks down large protein chains into smaller chains.  The final step in protein digestion occurs with the release of erepsins from the pancreas and they break the smaller chains into individual amino acids.
  165. 165.  Amylase enzymes are released from the pancreas that break large carbohydrate chains into small chains called disaccharides.  Then the small intestine releases disaccharide enzymes which break those small chains into individual sugars.
  166. 166.  The pancreas also releases enzymes known as lipases that break down fats into fatty acids and glycerol.  The lipases include pancreatic lipase and phospholipase.  Before lipids can be broken down by lipases they must first be emulsified.
  167. 167.  The liver is a large accessory organ of the digestive system that is constantly producing a fluid known as bile.  Bile is stored in the gall bladder until it is needed in the small intestine.
  168. 168.  The presence of lipids in the small intestine trigger the release of the hormone cholecystokinin (CCK) which triggers the release of bile from the gall bladder.  Bile contains bile salts that emulsifies fats which means it breaks them into smaller droplets so they can be digested.
  169. 169.  Bile contains cholesterol which can acts as a binding agent and cause bile salts to crystallize into gallstones.  Gallstones can block the bile duct and inhibit fat digestion while causing a lot of pain.
  170. 170.  Jaundice is a yellow discoloration of the skin and tissues caused by a collection of bile pigments in the blood.  The pigments are a result of the liver breaking down hemoglobin from red blood cells and the products are stored in the gall bladder.
  171. 171.  The liver is also able to detoxify many substances in the body by making them soluble and they can then be dissolved in the bloodstream and eliminated in urine.  One example would be alcohol. Alcohol can damage liver cells which are replaced by connective tissues and fat. The result is cirrhosis of the liver (shown left).
  172. 172.  Chemical digestion of nutrients is completed by the time it reaches the large intestine.  Now that nutrients are small enough they need to be absorbed into the blood stream so they can diffuse inside cells.
  173. 173.  The large intestine or colon stores waste products long enough so that water can be reabsorbed from the wastes.  Along with the water, some inorganic salts, minerals and vitamins are absorbed.
  174. 174.  The large intestine is home to several different types of bacteria.  These bacteria use waste materials to synthesize vitamins B and K. This is an example of a symbiotic relationship.
  175. 175.  Cellulose is a long chain carbohydrate found in the cell wall of plant cells.  Humans cannot digest cellulose however it provides bulk which promotes the movement of the waste products out of the colon.
  176. 176.  Cellulose is more commonly known as fiber. Fiber helps to remove wastes and therefore toxins from the body.  If you have a diet low in fiber you will have fewer bowel movements which means toxins remain in your body for longer periods of time.
  177. 177.  Most nutrients are absorbed in the small intestine.  The small intestine is lined with millions of small finger-like projections known as villi. The villi increase the surface are of the small intestine which increases it’s ability to absorbed digested nutrients.
  178. 178.  Each villus contains a capillary network along with a lacteal.  End products of protein and carbohydrate digestion enter the capillary network.  End products of fat digestion are absorbed into the lacteal. The lacteal is a vessel of the lymphatic system.
  179. 179.  Function ◦ re-absorb water  use ~9 liters of water every day in digestive juices  > 90% of water reabsorbed  not enough water absorbed  diarrhea  too much water absorbed  constipation
  180. 180.  Solid materials pass through the large intestine.  These are undigestible solids (fibers).  Water is absorbed.  Vitamins K and B are reabsorbed with the water.  Rectum- solid wastes exit the body.
  181. 181.  Living in the large intestine is a community of helpful bacteria ◦ Escherichia coli (E. coli)  produce vitamins  vitamin K; B vitamins  generate gases  by-product of bacterial metabolism  methane, hydrogen sulfide
  182. 182. Vestigial organ
  183. 183.  Last section of colon (large intestines) ◦ eliminate feces  undigested materials  extracellular waste  mainly cellulose from plants  roughage or fiber  masses of bacteria
  184. 184.  ULCERS – erosion of the surface of the alimentary canal generally associated with some kind of irritant
  185. 185.  CONSTIPATION – a condition in which the large intestine is emptied with difficulty.  Too much water is reabsorbed  and the solid waste hardens
  186. 186.  DIARRHEA – a gastrointestinal disturbance characterized by decreased water absorption and increased peristaltic activity of the large intestine.  This results in increased, multiple, watery feces.  This condition may result in severe dehydration, especially in infants
  187. 187.  APPENDICITIS – an inflammation of the appendix due to infection  Common treatment is removal of the appendix via surgery
  188. 188.  GALLSTONES – an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder  Can either be “passed” (OUCH!!) or surgically removed
  189. 189.  ANOREXIA NERVOSA - a psychological condition where an individual thinks they appear overweight and refuses to eat.  Weighs 85% or less than what is developmentally expected for age and height  Young girls do not begin to menstruate at the appropriate age.
  190. 190.  HEART BURN – ACID from the stomach backs up into the esophagus.