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  1. 1. DIGESTION AND ABSORPTION •1 •HSE Zoology blog
  2. 2. MAJOR COMPONENTS OF FOOD • Carbohydrates • Proteins • Fats • Vitamins • Minerals • Water •2 •HSE Zoology blog
  3. 3. DIGESTION • The process of conversion of complex food substances to simple absorbable form is called digestion. •3 •HSE Zoology blog
  4. 4. HUMAN DIGESTIVE SYSTEM Alimentary canal Associated glands •4 •HSE Zoology blog
  5. 5. DIGESTIVE SYSTEM OF MAN •5 •HSE Zoology blog
  6. 6. ORAL CAVITY (BUCCAL CAVITY) • Teeth • Tongue • Palate(roof) •6 •HSE Zoology blog
  7. 7. Dentition Refers the number, kinds and arrangement of teeth Thecodont Heterodont Diphyodont TEETH •7 •HSE Zoology blog
  8. 8. THECODONT • Teeth are placed in jaw sockets •8 •HSE Zoology blog
  9. 9. HETERODONT • Teeth are different types or dissimilar Incisors Canine Premolars Molars •9 •HSE Zoology blog
  10. 10. DIPHYODONT • Teeth appear twice in the whole life • Milk teeth • Permanent teeth •10 •HSE Zoology blog
  11. 11. The kind and number of teeth are explained in the form of formula is called dental formula. • Adult 32 permanent teeth • Incisors 2/2 • Canine 1/1 • Premolars 2/2 • Molars 3/3 • Child 20 milk teeth • Incisors 2/2 • Canine 1/1 • Premolars 0/0 • Molars 2/2 DENTAL FORMULA •11 •HSE Zoology blog
  12. 12. WISDOM TEETH • Third molar appears after the age of 20 years and hence is called wisdom teeth. •12 •HSE Zoology blog
  13. 13. Odontoblast Found in the dental pulp secrete dentine Crown Neck Root STRUCTURE OF TOOTH •13 •HSE Zoology blog
  14. 14. TONGUE • Freely movable muscular organ attached to the floor of the buccal cavity by frenulum. •14 •HSE Zoology blog
  15. 15. TONGUE • The upper surface of the tongue has small projections called papillae, some of which bear taste buds. •15 •HSE Zoology blog
  16. 16. PHARYNX • Common passage for digestive and respiratory system. • Opening of oesophagus • Opening of larynx - Glottis •16 •HSE Zoology blog
  17. 17. GLOTTIS • Glottis is guarded by a flap of tissue called epiglottis. • When food materials pass through the pharynx the epiglottis closes the glottis. •17 •HSE Zoology blog
  18. 18. OESOPHAGUS • Narrow muscular tube • 30 cm long • Leads to stomach • Pass through the diaphragm (a muscular partition that separates thorax from abdomen). •18 •HSE Zoology blog
  19. 19. OESOPHAGEAL SPHINCTER (GASTRO OESOPHAGIAL SPHINCTER) • Posterior region of the oesophagus there is a ring of muscle called oesophagial sphincter. • It controls the opening of the oesophagus into the stomach. •19 •HSE Zoology blog
  20. 20. PERISTALSIS • The movement of food materials in the esophagus is effected by the wave like contraction and relaxation of longitudinal and circular muscles of the esophagus is known as peristalsis. •20 •HSE Zoology blog
  21. 21. STOMACH • Large muscular ‘J’ shaped sac. • Lying just below the diaphragm in the abdominal cavity. • Three major parts – Cardiac – Fundic – Pyloric •21 •HSE Zoology blog
  22. 22. PYLORIC SPHINCTER • The opening of the stomach into the duodenum is guarded by pyloric sphincter. • Controls the flow of food to the intestine. •22 •HSE Zoology blog
  23. 23. SMALL INTESTINE • Long, highly coiled, narrow tube • Seven metres long • 2.5 cm diametre • Divided in to duodenum, jejunum & ileum. •23 •HSE Zoology blog
  24. 24. DUODENUM • First part of SI • ‘U’ shaped • Area of digestion • Receives common opening of the bile and pancreatic duct. •24 •HSE Zoology blog
  25. 25. JEJUNUM • Coiled and longer •25 •HSE Zoology blog
  26. 26. ILEUM • Highly coiled • Opens into the large intestine • Area of absorption •26 •HSE Zoology blog
  27. 27. LARGE INTESTINE • 1.5 metres long • Differentiated into Caecum , Colon & Rectum •27 •HSE Zoology blog
  28. 28. CAECUM • Small blind sac (at the junction of SI &LI) • Plays no role in Nutrient absorption. • It hosts some symbiotic microorganisms. • Caecum bears a finger like out growth of unknown function known as Vermiform Appendix. •28 •HSE Zoology blog
  29. 29. COLON ( Pelvic colon) •29 •HSE Zoology blog
  30. 30. RECTUM • Temporary storage of faeces • Rectum opens out by Anus. •30 •HSE Zoology blog
  31. 31. HISTOLOGY OF HUMAN GUT ( Outer most ) forms a fibrous coat (Inner most)-made of secretary & absorptive cells Loose connective tissue layer with blood & lymph vessels Smooth muscle •31 •HSE Zoology blog
  32. 32. RUGAE • Mucosal layer forms irregular fold in the stomach called rugae. •32 •HSE Zoology blog
  33. 33. VILLI • (Sing:- Villus) • Mucosal layer forms small finger like folding in the small intestine called Villi • A villus is about 0.5 to 1 mm long Villus •33 •HSE Zoology blog
  34. 34. VILLI •34 •HSE Zoology blog
  35. 35. VILLI •35 •HSE Zoology blog
  36. 36. VILLI •36 •HSE Zoology blog
  37. 37. •37 •HSE Zoology blog
  38. 38. MICROVILLI • Each villus has numerous electron microscopic evaginations called microvilli. • Both villi & micro villi increases the surface area for digestion and absorption of food •38 •HSE Zoology blog
  39. 39. DIGESTIVE GLANDS • Salivary glands • Pancreas • Liver • Gastric glands • Intestinal glands •39 •HSE Zoology blog
  40. 40. DIGESTIVE ENZYMES • Hydrolyses Group of enzymes released from the cells digestive system play a major role in the extra cellular digestion in human • Carbohydrase ( amylase ) carbohydrate digesting E.g.: ptyalin, maltose etc • Proteases (protein digesting) Eg: amino peptidase, dipeptidase . Lipase (lipid digesting) •40 •HSE Zoology blog
  41. 41. SALIVARY GLANDS • Secrete saliva • Found in buccal cavity • Three pairs of salivary glands 1.Parotid glands (largest) 2.Sub lingual glands 3.Sub maxillary (Sub mandibular) •41 •HSE Zoology blog
  42. 42. SALIVA • Derived from blood plasma • Secrete 1.5 liters of saliva per day • Slightly alkaline • Contain water & electrolyte (Na+, K+, Cl-, HCO3 -) • Mucin, ptyalin, lyzozyme & inorganic salts • Ptyalin digest starch in to maltose •42 •HSE Zoology blog
  43. 43. LIVER • Largest gland in the human body • Weighs about 1.5 kg in adult man • Bi lobed • Secrete bile •43 •HSE Zoology blog
  44. 44. • Each lobe is separated into numerous tiny hepatic lobules, which are the functional units. • A lobule is formed of numerous hepatic cells – bile is secreted by hepatic cells • Each lobule is covered by a thin connective tissue sheath called Glisson’s capsule Glisson’s capsule LIVER •44 •HSE Zoology blog
  45. 45. HEPATIC LOBULES •45 •HSE Zoology blog
  46. 46. GALL BLADDER • Bile is stored and Concentrated in a thin muscular sac called gall bladder. • Capacity- 40 – 60 ml • Absent in whale, horses, rats etc. •46 •HSE Zoology blog
  47. 47. BILE • Golden yellow or greenish fluid • Alkaline nature • Bile pigments (product of dead RBC) (biliverdin & bilirubin) • Bile salts, • cholesterol, • phospholipids • Bile salts play a very important role in the emulsification of fat •47 •HSE Zoology blog
  48. 48. GALL BLADDER • The duct of gall bladder (cystic duct) along with hepatic duct from the liver forms a common bile duct. •48 •HSE Zoology blog
  49. 49. GALL BLADDER • The bile duct and pancreatic duct opens together into the duodenum as common hepato - pancreatic duct, which is guarded by a sphincter called sphincter of Oddi. Hepato - Pancreatic duct •49 •HSE Zoology blog
  50. 50. PANCREAS • Located between stomach & duodenum • Second largest glands • Heterocrine gland (both exocrine &endocrine) • Pancreatic duct opens into the duodenum along with bile duct • Secrete pancreatic juice. •50 •HSE Zoology blog
  51. 51. PANCREATIC JUICE • Alkaline nature • Trypsinogen , Chymotrypsinogen Proarboxypeptidase, Amylopsin (p. amylase) • Steapsin (pancreatic lipase) • Nuclease (Nucleic acid digesting enzyme) •51 •HSE Zoology blog
  52. 52. GASTRIC GLANDS • Found on the wall of stomach • Formed of three kinds of cells 1. Mucous cells 2. Chief cells or Zymogen cells 3. Oxyntic cells or Parital cells •52 •HSE Zoology blog
  53. 53. mucus secreting GASTRIC GLANDS •53 •HSE Zoology blog
  54. 54. GASTRIC GLANDS •54 •HSE Zoology blog
  55. 55. GASTRIC SECRETIONS Name of Cell Function Mucous cells (Goblet cells) Secrete mucous Oxyntic cells or Parital cells Secretion of HCl and intrensic factor (factor essential for the absorption of vitamin B12) Chief cells or Zymogen cells Secretion of enzymes such as pepsin , rennin, lipase etc. •55 •HSE Zoology blog
  56. 56. • Inactivate the secretion of salivary amylase. • Kills micro organism • Lowers the pH of the stomach (1.5 to 2.5) • Activate proenzyme pepsinogen to active pepsin. HCl •56 •HSE Zoology blog
  57. 57. INTESTINAL GLANDS • Simple tubular glands found throughout SI • Two types Crypts of Lieberkuhn Glands of Brunner •57 •HSE Zoology blog
  58. 58. CRYPTS OF LIEBERKUHN • Goblet cells – Mucous secreting • Paneth cells – Enzyme secreting Many surface area of gastro intestinal tract are lined by evaginations of the epithelium in to sub mucosa similar to pits. These pits of the intestine are called Crypts of Lieberkuhn Paneth cells Goblet cells villus crypt •58 •HSE Zoology blog
  59. 59. GLANDS OF BRUNNER ( DUODENAL GLANDS) • Confined to the sub mucosa of the duodenum and secrete mucus only •59 •HSE Zoology blog
  60. 60. INTESTINAL JUICE (SUCCUS ENTERICUS) • Collective secretions of intestinal glands • Alkaline nature • Contain enzymes , mucous & inorganic salts. • Proteases Aminopeptidase, Dipeptidase • Amylase Maltase, Isomaltase Lactase, Surcease • Lipase • Enterokinase •60 •HSE Zoology blog
  61. 61. DIGESTION • The teeth and tongue with the help of saliva masticate and mix up the food into bolus. • The bolus is conveyed to pharynx and then to oesophagus by swallowing or deglutition. •61 •HSE Zoology blog
  62. 62. DIGESTION • The stomach stores the food 4-5 hrs. The food mixes thoroughly with acidic gastric juice to form paste.- Chyme chyme •62 •HSE Zoology blog
  63. 63. • Starch Maltose Buccal cavity Starch Maltose Salivary amylase CARBOHYDRATE DIGESTION Stomach No carbohydrate digestion Small Intestine Starch Maltose Maltose 2 Glucose Lactose Glucose + Galactose Sucrose Glucose + Fructose P. amylase Maltase Lactase Sucrase •63 •HSE Zoology blog
  64. 64. Buccal cavity No protein digestion Stomach Pepsinogen Pepsin HCl Protein Pepsin Peptones + Proteoses Peptones = larger peptides Proteoses = smaller peptides Small intestine Trypsinogen Enterokinase Trypsin Chymotrypsinogen Chymotrypsin Procarboxy peptidase Carboxy peptidase Proteins Peptones Proteoses Dipeptides Dipeptides Amino acids Dipeptidase Trypsin / Chymotrypsin Carboxy peptidase PROTEIN DIGESTION •64 •HSE Zoology blog
  65. 65. Buccal cavity No protein digestion Stomach Gastric lipase hydrolyses only a small amount of fat Small intestine Fat Fat droplets Bile Emulsification Fat Pancreatic lipase Fatty acids & Glycerol Diglyceride Monoglycerides FAT DIGESTION •65 •HSE Zoology blog
  66. 66. Small Intestine Nucleic acids Nucleotides Nucleosides Sugar + Bases NUCLEIC ACID DIGESTION •66 •HSE Zoology blog
  67. 67. END PRODUCTS OF DIGESTION Carbohydrates Glucose Fructose Galactose Proteins Amino acids Fats Fatty acids glycerol •67 •HSE Zoology blog
  68. 68. • Complete digestion of food take place in the duodenum. The fully digested food is semi fluid in nature and is known as Chyle DIGESTION •68 •HSE Zoology blog
  69. 69. ABSORPTION OF DIGESTED PRODUCTS • Absorption is the process by which the end products of digestion pass through the intestinal mucosa ( transported through the intestinal mucosa) into the blood or lymph • The end products of digestion are absorbed in the jejunum and ileum regions of small intestine. •69 •HSE Zoology blog
  70. 70. Absorption is carried out by – Passive transport – Facilitated transport – Active transport ABSORPTION •70 •HSE Zoology blog
  71. 71. PASSIVE TRANSPORT • Small amounts of monosaccharide like glucose, amino acids, and some of electrolytes like chloride ions are generally absorbed by simple diffusion. •71 •HSE Zoology blog
  72. 72. •72 •HSE Zoology blog
  73. 73. FACILITATED TRANSPORT • Fructose and some amino acids are absorbed with the help of carrier ions like sodium. This mechanism is called facilitated transport. •73 •HSE Zoology blog
  74. 74. ACTIVE TRANSPORT • Requires energy • Various nutrients like amino acids, monosaccharide like glucose, electrolytes like Na+ are reabsorbed into the blood by active transport. •74 •HSE Zoology blog
  75. 75. •75 •HSE Zoology blog
  76. 76. ABSORPTION OF FAT • Fatty acids and glycerol insoluble in water so they cannot be absorbed directly from the lumen of the intestine. • With the help of bile salts & phospholipids the fatty acids and glycerol are converted into small spherical water soluble droplets called micelles. •76 •HSE Zoology blog
  77. 77. ABSORPTION OF FAT Micelles are reformed into very small protein coated fat globules called chylomicrons. Which are transported in to the lymph vessels (lactales)in the villi. •77 •HSE Zoology blog
  78. 78. ABSORPTION OF FAT •78 •HSE Zoology blog
  79. 79. LARGE INTESTINE Functions Absorption of water, minerals and certain drugs. Secretion of mucus which helps in adhering waste. • No significant digestive activity occurs in the large intestine. •79 •HSE Zoology blog
  80. 80. LARGE INTESTINE • The undigested and unabsorbed substances (faeces) enters into the caecum of the large intestine through the ileo caecal valve, which prevents the back flow of faecal matter. •80 •HSE Zoology blog
  81. 81. EGESTION • The egestion of faeces to the outside through the anal opening (defaecation) is a voluntary process and is carried out by a mass peristaltic movement. •81 •HSE Zoology blog
  82. 82. THE SUMMARY OF ABSORPTION IN DIFFERENT PARTS OF DIGESTIVE SYSTEM Oral cavity Stomach Small Intestine Large Intestine Certain drugs coming in contact with the mucosa of the mouth and lower side of the tongue are absorbed into the blood capillaries lining them. Water, simple sugars, alcohol Glucose Fructose Fatty acids Glycerol Amino acids Water , some minerals, drugs •82 •HSE Zoology blog
  83. 83. DISORDERS OF DIGESTIVE SYSTEM • Infections of the digestive system are caused by bacteria, virus, parasites like tape worm, thread worm, round worm, hook worm, pinworm etc. Bacteria Tape worm Virus Pinworm Thread worm •83 •HSE Zoology blog
  84. 84. VOMITING • It is the ejection of stomach content through the mouth. •84 •HSE Zoology blog
  85. 85. DIARRHOEA • The abnormal frequency of bowel movement and increased liquidity of faecal discharge is known as diarrhoea. • It reduces the absorption of food. •85 •HSE Zoology blog
  86. 86. JAUNDICE • The liver is affected, skin, eyes turn yellow due to the deposition of bile pigments. •86 •HSE Zoology blog
  87. 87. CONSTIPATION • The faeces are retained with in the rectum as the bowel movement occur irregularly. •87 •HSE Zoology blog
  88. 88. INDIGESTION • The food is not properly digested leading to the feeling of fullness. • The cause of indigestion are inadequate enzyme secretion, anxiety, food poisoning, overeating and spicy food. •88 •HSE Zoology blog