Digestion

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  • Digestion

    1. 1. Digestive System <ul><li>Digestion includes six basic processes: </li></ul><ul><li>1 ingestion 5. absorption </li></ul><ul><li>2. secretion 6. defecation </li></ul><ul><li>3. mixing and propulsion, </li></ul><ul><li>4. mechanical and chemical digestion, </li></ul><ul><li>Mechanical digestion consists of movements of the gastrointestinal tract that aid chemical digestion. </li></ul><ul><li>Chemical digestion is a series of catabolic (hydrolysis) reactions that break down larger carbohydrate, lipid, and protein food molecules into smaller molecules that are usable by the body cells. </li></ul>
    2. 2. Digestive System Figure 14.1 Slide 14.1 Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
    3. 3. Digestive System <ul><li>The breaking down of larger food molecules into smaller molecules is called digestion. </li></ul><ul><li>The passage of these smaller molecules into blood and lymph is termed absorption. </li></ul><ul><li>The organs that collectively perform digestion and absorption compose the digestive system and are usually divided into two main groups: those composing the gastrointestinal (GI) tract and accessory structures. </li></ul><ul><li>The accessory structures include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas. </li></ul>i
    4. 4. Structure of the Wall <ul><li>The GI tract is composed of four layers or tunics: </li></ul><ul><ul><li>1. Mucosa - The mucosa, forming the inner lining of the tract, is supplied </li></ul></ul><ul><ul><li> with a rich network of blood vessels, nerve fibers and </li></ul></ul><ul><ul><li> endocrine cells . </li></ul></ul><ul><ul><li>2. Submucosa Connective tissue that lies just below the mucosa. It contains </li></ul></ul><ul><li> blood vessels and nerves </li></ul><ul><ul><li>3. Muscularis Contains two layers of muscle tissue. Important for peristalsis, </li></ul></ul><ul><li> mixing of food with digestive juices, and the mechanical </li></ul><ul><li> breakdown of food </li></ul><ul><li>4. Serosa - Outermost covering, composed of visceral peritoneum. </li></ul><ul><ul><li>It is a continuous tube extending from the mouth to the anus. The loops </li></ul></ul><ul><ul><li>of the digestive tract are anchored to the posterior wall of the abdominal </li></ul></ul><ul><ul><li>cavity by a large double fold of peritoneal tissue called the mesentary. </li></ul></ul>
    5. 5. Digestive System Figure 14.1 Slide 14.1 Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
    6. 6. Digestive Organs <ul><li>Mouth/Oral Cavity </li></ul><ul><li>Pharynx </li></ul><ul><li>Esophagus </li></ul><ul><li>Stomach </li></ul><ul><li>Small intestine </li></ul><ul><ul><li>Duodenum </li></ul></ul><ul><ul><li>Jejunum </li></ul></ul><ul><ul><li>Ileum </li></ul></ul><ul><li>Large intestine </li></ul><ul><li>Rectum </li></ul><ul><li>Anus </li></ul>
    7. 7. The Oral Cavity <ul><li>Roof of the mouth </li></ul><ul><ul><li>Hard Palate- anterior roof of the mouth </li></ul></ul><ul><ul><li>Soft Palate- posterior roof of the mouth </li></ul></ul><ul><li>Sides of the mouth </li></ul><ul><ul><li>Cheeks- lateral walls of the oral cavity </li></ul></ul><ul><li>Floor of the mouth </li></ul><ul><ul><li>Tongue/ functions </li></ul></ul><ul><ul><ul><li>Swallowing </li></ul></ul></ul><ul><ul><ul><li>Chewing </li></ul></ul></ul><ul><ul><ul><li>Speech </li></ul></ul></ul><ul><ul><ul><li>Taste </li></ul></ul></ul><ul><ul><ul><ul><li>Bitter, sour, sweet and salt </li></ul></ul></ul></ul>i
    8. 8. Buccal Cavity lips gullet – throat Uvula Hard Palate Soft Palate Tongue Palatine Tonsils
    9. 9. The Oral Cavity <ul><li>Teeth </li></ul><ul><ul><li>Functions </li></ul></ul><ul><ul><ul><li>Divide the food into smaller pieces </li></ul></ul></ul><ul><ul><ul><ul><li>Mastication- chewing </li></ul></ul></ul></ul><ul><ul><ul><li>Two sets of teeth </li></ul></ul></ul><ul><ul><ul><ul><li>Deciduous teeth- baby or milk teeth </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Total = 20 </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Start to erupt 6 months of age and are complete by 2 years </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>They loosen and fall out between ages 6 and 12. </li></ul></ul></ul></ul></ul>
    10. 10. The Oral Cavity <ul><li>Teeth - continued </li></ul><ul><ul><li>Permanent teeth </li></ul></ul><ul><ul><ul><li>Total = 32 </li></ul></ul></ul><ul><ul><ul><li>All permanent teeth but the third molars have erupted by the end of adolescence </li></ul></ul></ul><ul><ul><ul><li>Third molars emerge between 17 and 25 </li></ul></ul></ul><ul><ul><ul><li>They often fail to erupt and are said to be impacted </li></ul></ul></ul>
    11. 11. The Oral Cavity <ul><li>Types of teeth </li></ul><ul><ul><li>Incisors- biting </li></ul></ul><ul><ul><li>Canine- tearing </li></ul></ul><ul><ul><li>Premolars (bicuspids)- grinding </li></ul></ul><ul><ul><li>Molars- grinding </li></ul></ul>
    12. 12. The Mouth: Teeth Figur 14.4A Slide 14.6A Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
    13. 13. Wisdom Teeth
    14. 14. Molars <ul><li>Crown- upper portion of the tooth that is visible. It is made up of calcium phosphate, the biologically manufactured substance </li></ul><ul><li>Neck- boundary between the root and crown </li></ul><ul><li>Root- portion of the tooth that is embedded in the jawbone </li></ul>
    15. 15. Tooth Terms <ul><li>Enamel- covers the crown, very hard </li></ul><ul><li>Dentin- bulk of the tooth, very similar to bone but does not have cells </li></ul><ul><li>Gingiva- gums </li></ul><ul><li>Pulp cavity- contains connective tissue, blood vessels and nerve fibers. Supplies nutrients to tooth tissues and provides tooth sensations </li></ul><ul><li>Root canal- where pulp cavity extends into the root. Provides route for blood vessels and nerves </li></ul>
    16. 16. Pharynx
    17. 17. Pharynx- 3 Divisions <ul><li>Nasopharynx- behind the nose and palate </li></ul><ul><li>Oropharynx- behind the mouth to the soft palate, above the hyoid bone </li></ul><ul><li>Laryngopharynx- hyoid bone to the esophagus </li></ul>
    18. 18. Pharynx <ul><li>Uvula- a small muscular flap of tissue that hand from the soft palate and prevent food from entering the nasal cavity during swallowing by closing off the posterior nares </li></ul><ul><li>Tonsils- part of the lymphatic system </li></ul><ul><ul><li>Palatine tonsils- at the posterior end of the oral cavity are masses of lymphoid tissue </li></ul></ul><ul><ul><li>Lingual tonsils- covers the base of the tongue </li></ul></ul>
    19. 19. Pharynx and Tonsils
    20. 20. Salivary Glands <ul><li>Saliva- secreted in response to sight, smell or thought of food, or the presence of food in the mouth </li></ul><ul><li>There are three pairs of salivary glands: </li></ul><ul><li>1. parotid Largest gland, lies anterior to each ear </li></ul><ul><li>2. submandibular empty their secretions into the floor of the mouth </li></ul><ul><li>3. sublingual glands Smallest gland, located on the floor of the mouth inferior to the tongue. Empty their secretions into the floor of the mouth </li></ul>i
    21. 21. Salivary Glands
    22. 22. Salivary Glands i
    23. 23. Saliva <ul><li>Saliva contents </li></ul><ul><ul><li>Water </li></ul></ul><ul><ul><li>Salivary amylase- alkaline secretion, digests starch </li></ul></ul><ul><ul><li>Amount per day- 1000 to 2000 mL </li></ul></ul><ul><li>Function of saliva </li></ul><ul><ul><li>Prepares food for swallowing- mucus </li></ul></ul><ul><ul><li>Prevents mouth from drying out </li></ul></ul><ul><ul><li>Starts the breakdown of starch </li></ul></ul>
    24. 24. Swallowing Deglutition Bolus Involuntary nervous response Epiglottis i the act of swallowing the ball of food Starts as a voluntary action but shortly becomes an involuntary action the covering of the opening to the windpipe animation 1
    25. 25. Esophagus <ul><li>Location: pharynx to the stomach </li></ul><ul><li>Length: 10 inches </li></ul><ul><li>Histology: stratified squamous epithelium </li></ul><ul><ul><li>Mucous glands- secrete mucous </li></ul></ul><ul><li>Muscles: Upper 1/3 = skeletal muscle </li></ul><ul><li> Lower 1/3 = smooth muscle </li></ul><ul><li> Middle 1/3 = mixture of both </li></ul><ul><li>Function: carries food from the mouth to the stomach </li></ul><ul><li>Peristalsis: involuntary muscular contractions that move food along the esophagus </li></ul>
    26. 26. Motility: Peristalsis Figure 14.3A Slide 14.4 Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
    27. 27. Stomach
    28. 28. Stomach <ul><li>Location: left side and high up in the abdomen. It is “J” shaped </li></ul><ul><li>Functions: </li></ul><ul><ul><li>Temporary storage of ingested food </li></ul></ul><ul><ul><li>Mechanical breakdown of ingested food </li></ul></ul><ul><ul><li>Breakdown of chemical bonds in food items by acids and enzymes </li></ul></ul><ul><ul><li>Production of intrinsic factor needed for vitamin B 12 absorption </li></ul></ul><ul><li>Can store 4 liters of material </li></ul><ul><li>Food remains in stomach for 2-6 hours </li></ul><ul><li>Four divisions of the stomach </li></ul><ul><ul><li>Cardia- connects the esophagus to the stomach </li></ul></ul><ul><ul><li>Fundus- bulge of the stomach superior to the cardia </li></ul></ul><ul><ul><li>Body- large area between the fundus and the curve of the “J” </li></ul></ul><ul><ul><li>Pylorus- connects the stomach to the small intestine </li></ul></ul>Man Eating
    29. 29. Stomach
    30. 30. Structure of the Stomach Wall Figure 14.7 Slide 14.9A Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
    31. 31. Stomach Sphincter Muscles <ul><li>Cardiac sphincter- from the esophagus </li></ul><ul><li>Pyloric sphincter- connects to the small intestine </li></ul>
    32. 32. Stomach Rugae <ul><li>Rugae </li></ul><ul><ul><li>Folds of the stomach, they smooth out and disappear as the stomach becomes distended from food </li></ul></ul>Rugae
    33. 33. Muscles of the Stomach <ul><li>Longitudinal muscles </li></ul><ul><li>Circular muscles </li></ul><ul><li>Inner oblique muscles </li></ul><ul><li>These muscles add strength and assist in the mixing and churning of food </li></ul>
    34. 34. Stomach Muscles
    35. 35. Physiology of the Digestive System <ul><li>Stomach </li></ul><ul><ul><li>Mechanical digestion - churning or turning the food and mixes it until it becomes chyme (semi-fluid mixture of food) </li></ul></ul><ul><ul><li>Histology- simple columnar epithelium with mucous cells </li></ul></ul>
    36. 36. Gastric Secretions Three types of gastric glands 1. Mucus cells 2. Chief cells Secretion - mucus- watery substance Function - Protects stomach lining Secretion - Pepsinogen (inactive form of pepsin); made active in the presence of HCl Function - begins digestion of proteins into polypeptides i McGraw-Hill i
    37. 37. Gastric Secretions - cont. 3. Parietal cells Secretion - HCl & intrinsic factor (pH .9-1.5) Function - Kills bacteria, absorption of vitamin B 12, softens meat & bones, activates pepsinogen, HCl, pepsin, proteins and shorter chain amino acids 4. Intrinsic factor Vitamin B 12 Function- essential for the normal development of red blood cells Malfunction of intrinsic factor = pernicious anemia
    38. 38. Hormones that control Gastric Secretions <ul><li>Hormone : Gastrin </li></ul><ul><li>Location of hormone : pyloric region of stomach </li></ul><ul><li>When released : when solid food enters the stomach </li></ul><ul><li>Where does it go? To the blood stream back to the stomach </li></ul><ul><li>What does it do? Stimulates the glands to produce gastric juice </li></ul>
    39. 39. Regulation of Gastric Secretions Three Phases 1. Cephalic phase- parasympathetic reflex (30-50%) 2. Gastric phase (40-50%) 3. Intestinal phase (5%) Anticipate food, medulla oblongata, taste, smell, sight And thought of food Food in the stomach, stimulates more gastrin which in turn stimulates more gastric juices Chyme entering the small intestine triggers this phase. This inhibits gastric juices and more gastrin is secreted Stomach Absorption- absorbs only water,certain salts and lipid soluble drugs and also alcohol.
    40. 40. Small Intestine <ul><li>Diameter: 4 cm (1.6 in) to 2.5 cm (1 in.) </li></ul><ul><li>Length: 20 feet </li></ul><ul><li>Functions: </li></ul><ul><ul><li>Complete the digestion of food </li></ul></ul><ul><ul><li>Absorb the end products of digestion into the blood and lymph </li></ul></ul><ul><ul><li>Secrete hormones that help control the production of pancreatic juice, bile and intestinal juice </li></ul></ul><ul><ul><li>Control the amount of fluid and electrolytes lost from the body </li></ul></ul>
    41. 41. Small Intestine
    42. 42. 3 Division of the Small Intestine <ul><li>Duodenum: (latin for 12) </li></ul><ul><ul><li>Length: 10 inches </li></ul></ul><ul><ul><li>Function: receives chyme from the stomach and digestive secretions from the pancreas and liver </li></ul></ul><ul><li>Jejunum: </li></ul><ul><ul><li>Length: 8 feet </li></ul></ul><ul><ul><li>Function: bulk of chemical digestion and nutrient absorption </li></ul></ul>
    43. 43. Duodenum Gallstones i Duodenum valve Bile i
    44. 44. Jejunum Jejunum
    45. 45. 3 Division of the Small Intestine <ul><li>Ileum </li></ul><ul><ul><li>Length: 12 feet </li></ul></ul><ul><ul><li>Function: longest section, ends at the ileocecal valve (a sphincter valve) which controls the flow of material from the ileum into the cecum, the first part of the large intestine. </li></ul></ul>
    46. 46. Ileum
    47. 47. Villi and the Small Intestine <ul><li>Three parts of the villi: </li></ul><ul><ul><li>Arteriole </li></ul></ul><ul><ul><li>Venule </li></ul></ul><ul><ul><li>Lymph vessel (lacteal)- absorbs fatty acids </li></ul></ul><ul><li>Villi area covered </li></ul><ul><ul><li>Larger than the size of a tennis court </li></ul></ul><ul><li>Function </li></ul><ul><ul><li>Increase surface area for absorption (600 times) </li></ul></ul>
    48. 48. Villi and the Small Intestine <ul><li>Goblet cells </li></ul><ul><ul><li>Mucous secreting cells </li></ul></ul><ul><li>Digestive enzymes in the microvilli </li></ul><ul><ul><li>Peptidase- proteins </li></ul></ul><ul><ul><li>Maltase, sucrase, lactase- disaccharides </li></ul></ul><ul><ul><li>Lipase- lipids </li></ul></ul>
    49. 49. The Wall of the Small Intestine Figure 14.9 Slide 14.10A Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
    50. 50. Villi Microvilli
    51. 51. Hormones secreted by Intestinal Cells <ul><li>1. Secretin </li></ul><ul><ul><li>Stimulates the pancreas to secrete a fluid high in bicarbonate ions that help neutralize chyme </li></ul></ul><ul><li>CCK (cholecystokinin) </li></ul><ul><ul><li>Stimulates the release of bile from the gallbladder and the secretion of digestive enzymes from the pancreas </li></ul></ul>
    52. 52. 3 solutions in the small intestine <ul><li>The following solution mix with chyme from the stomach in the small intestine: </li></ul><ul><ul><li>Bile from the liver </li></ul></ul><ul><ul><li>Pancreatic juice from the pancreas </li></ul></ul><ul><ul><li>Intestinal juice from glands in the wall of the intestines </li></ul></ul>
    53. 53. Digestion in the Small Intestine <ul><li>Bile </li></ul><ul><ul><li>Produced in the liver </li></ul></ul><ul><ul><li>Stored in the gallbladder </li></ul></ul><ul><ul><li>Contains: water, ions, cholesterol, sodium bicarbonate ions (NO ENZYMES) </li></ul></ul><ul><ul><ul><li>These act as emulsifying agents- which lower the surface tension of fats, forming small droplets </li></ul></ul></ul><ul><ul><li>Green color comes from broken down hemoglobin </li></ul></ul><ul><ul><li>Bilirubin- main end product produced by the decomposition of hemoglobin </li></ul></ul>
    54. 54. Digestion in the Small Intestine <ul><li>Bile- cont. </li></ul><ul><ul><li>Travels to the small intestine by the bile duct </li></ul></ul><ul><ul><li>Large amounts of bile are released from the gallbladder in the presence of fatty acids </li></ul></ul><ul><ul><li>The hormone that causes the gallbladder to contract and eject bile is CCK (cholecystokinin) </li></ul></ul><ul><ul><li>The stimulus for the release of CCK is fatty acids and amino acids in the duodenum </li></ul></ul>
    55. 55. Digestion in the Small Intestine <ul><li>Bile- cont. </li></ul><ul><ul><li>If the gallbladder is removed, there is no storage of bile so it is constantly secreted into the small intestine by the liver </li></ul></ul><ul><ul><li>Gallstones are hard deposits of cholesterol and or calcium </li></ul></ul>
    56. 56. Gallbladder <ul><li>The gallbladder is a sac located on the posterior surface of the liver. </li></ul><ul><li>The gallbladder stores and concentrates bile. </li></ul><ul><li>Cholecystokinin (CCK) stimulates the release of bile into the common bile duct. </li></ul>i i
    57. 57. Gallstones
    58. 58. Pancreas
    59. 59. Pancreas
    60. 60. Pancreas <ul><li>Location: left side behind the stomach </li></ul><ul><li>Two types of glands: </li></ul><ul><ul><li>Exocrine gland- secretes materials onto the surface or into a cavity </li></ul></ul><ul><ul><li>Digestive enzymes (do most of the work in the SI) </li></ul></ul><ul><ul><ul><li>Amylase- starch to maltose </li></ul></ul></ul><ul><ul><ul><li>Trypsin- proteins </li></ul></ul></ul><ul><ul><ul><li>Lipase- fat </li></ul></ul></ul><ul><ul><ul><li>Nucleases- nucleic acids </li></ul></ul></ul><ul><ul><li>Sodium bicarbonate ions </li></ul></ul><ul><ul><ul><li>Neutralizes the chyme </li></ul></ul></ul><ul><ul><ul><li>pH of the contents of the small intestine are slightly alkaline- 7.5-8 </li></ul></ul></ul>
    61. 61. Pancreas <ul><li>Endocrine gland- secretes materials into the blood </li></ul><ul><ul><li>Regulates blood sugar levels </li></ul></ul><ul><ul><ul><li>Insulin </li></ul></ul></ul><ul><ul><ul><li>Glucagon </li></ul></ul></ul><ul><ul><li>Hormone secreting cells of the pancreas </li></ul></ul><ul><ul><ul><li>Beta cells- insulin </li></ul></ul></ul><ul><ul><ul><li>Alpha cells- glucagon </li></ul></ul></ul><ul><ul><ul><li>Delta cells- somastatin- inhibits the release of both insulin and glucagon </li></ul></ul></ul>
    62. 62. Pancreas <ul><li>Pancreatic secretion control </li></ul><ul><ul><li>Sight </li></ul></ul><ul><ul><li>Sound </li></ul></ul><ul><ul><li>Food in the mouth </li></ul></ul><ul><ul><li>Hormones </li></ul></ul><ul><ul><ul><li>Secretin </li></ul></ul></ul><ul><ul><ul><li>Secreted from the intestinal mucosa </li></ul></ul></ul><ul><ul><ul><li>When the intestinal content is acidic, secretin aacts as a chemical messenger causing the pancreas to secrete enzymes in response. As a result, the alkalinity of the pancreatic juices neutralizes the acid content in the SI </li></ul></ul></ul>
    63. 63. Liver <ul><li>Location: right hypochondriac and epigastric abdominopelvic regions </li></ul><ul><li>Materials carried to the liver from the SI for storage </li></ul><ul><ul><li>Vitamins </li></ul></ul><ul><ul><li>Minerals </li></ul></ul><ul><ul><li>Nutrients </li></ul></ul><ul><li>Functions </li></ul><ul><ul><li>Secretes bile </li></ul></ul><ul><ul><li>Synthesizes bile salts </li></ul></ul><ul><ul><li>Sythesizes plasma proteins </li></ul></ul><ul><ul><li>Storage of glucose, iron, vitamins </li></ul></ul><ul><ul><li>Detoxification of toxic compounds </li></ul></ul><ul><ul><li>Carbohydrate, lipid and proteins metabolism </li></ul></ul><ul><ul><li>Filters damaged RBC’s, bacteria and other materials from the blood </li></ul></ul>
    64. 64. Liver i
    65. 65. Liver <ul><li>Liver secretions for digestion </li></ul><ul><ul><li>Bile- stored in the gallbladder </li></ul></ul><ul><ul><ul><li>Water, bicarbonate ions, bilirubin, cholesterol, lipids </li></ul></ul></ul><ul><ul><ul><li>Collectively known as bile salts </li></ul></ul></ul><ul><ul><li>Emulsification </li></ul></ul><ul><ul><ul><li>Creates tiny droplets of fat (which coats the lipid to increase surface area for the lipid enzyme to attack </li></ul></ul></ul>
    66. 66. Large Intestine <ul><li>AKA: Colon </li></ul><ul><li>Length: 5 feet </li></ul><ul><li>3 divisions: </li></ul><ul><ul><li>Cecum- vermiform appendix- vestigal organ </li></ul></ul><ul><ul><li>Colon </li></ul></ul><ul><ul><ul><li>Ascending colon </li></ul></ul></ul><ul><ul><ul><li>Transverse colon </li></ul></ul></ul><ul><ul><ul><li>Descending colon </li></ul></ul></ul><ul><ul><ul><ul><li>Sigmoid colon- S-shaped curve </li></ul></ul></ul></ul><ul><ul><li>Rectum- thick muscular layer </li></ul></ul><ul><ul><li>Anal canal </li></ul></ul><ul><ul><ul><li>Internal sphincter valve- smooth muscle </li></ul></ul></ul><ul><ul><ul><li>External sphincter valve- skeletal muscle (voluntary) </li></ul></ul></ul>
    67. 67. Large Intestine Figure 14.12 Slide 14.13A
    68. 68. Large Intestine <ul><li>Functions: </li></ul><ul><ul><li>Large quantities of water are reabsorbed </li></ul></ul><ul><ul><li>Storage of waste </li></ul></ul><ul><ul><li>NO digestion of food material </li></ul></ul><ul><li>Solid waste of the the large intestine: feces </li></ul><ul><li>Most of the material that enters the large intestine is undigested fiber </li></ul><ul><li>Millions of bacteria inhabit the large intestine and are carried out of the body with the feces </li></ul>
    69. 69. Large Intestine <ul><li>Bacteria feed on undigested material in the large intestine and release gas as a waste product </li></ul><ul><li>They also synthesize vitamin K and and certain B vitamins which are absorbed into the bloodstream </li></ul><ul><li>The reddish brown color of feces comes from bilirubin from a breakdown of hemoglobin </li></ul>

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