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Karteikarten

Digestive System

Jonathan Cash HAP 1 5 Englisch 47 Karten

Digestive System

Karten in diesem Stapel (47)

  1. 1Organs of the Digestive System Two main groups
    - Alimentary canal (also called the GI tract) continuous coiled hollow muscular tube
    - Accessory digestive organs
  2. 2Organs of the Alimentary Canal- Mouth
    - Pharynx
    - Esophagus
    - Stomach
    - Small intestine
    - Large intestine
    - Rectum
    - Anus
  3. 3Accessory Digestive Organs- Salivary glands
    - Tongue
    - Teeth
    - Pancreas
    - Liver
    - Gall bladder
  4. 4—
  5. 5Structure of Alimentary Canal- Mucosa - in contact with food substances  Innermost layer
     Moist membrane - mucus
    - Submucosa - blood supply and nerves
    -Muscularis externa
    - Smooth muscle - circular and longitudinal  Serosa – anchors organs
  6. 6—
  7. 7Ingestion- Getting food into the mouth.
    - This is an active, voluntary process
  8. 8Propulsion- Moving foods from one region of the digestive system to another
    - This includes:
     Swallowing
     Peristalsis
     Segmentation
  9. 9Propulsion- Peristalsis – alternating waves of contraction - oesophagus
    - Segmentation – moving materials back and forth to aid in mixing - small intestine
  10. 10Mechanical digestion - food breakdown- Mastication / Chewing = Grinding and mixing of food in the mouth by the teeth and tongue
    - Churning of food in the stomach
    - Segmentation (mixing) in the small intestine
    - Prepares food for enzyme breakdown
  11. 11Chemical Digestion – food breakdown- Enzymes break down food molecules into their building blocks (smallest units)
    - Each major food group uses different enzymes
     Carbohydrates are broken to simple sugars
     Proteins are broken to amino acids
     Fats are broken to fatty acids and glycerol
  12. 12Absorption- End products of digestion are absorbed into the blood or lymph
    - Active and passive transport
    - Mostly in small intestine
  13. 13Defecation- Elimination of indigestible substances as faces
    - Large intestine
  14. 14Mouth• Foodisingested
    • Propulsionisinitiatedby swallowing
    • Mechanicaldigestionbegins.
    • Chemicalbreakdownofstarch
    begins.
    • The pharynx and esophagus serve as conduits to pass food from the mouth to the stomach
  15. 15Saliva- Mixture of mucus and serous fluids
    - Helps to form a food bolus
    - Contains salivary amylase to begin starch digestion
    - Dissolves food chemicals so they can be tasted by taste buds
    
  16. 16Esophagus• Runs from the pharynx through the diaphragm to the stomach
    • 25cm long
    • Wall consists of the 4
    basic layers.
    • Peristalsis – aided by gravity
  17. 17Stomach Anatomy- Food enters at the cardioesophageal sphincter
    - 4 regions of the stomach
    - Rugae – internal folds of the mucosa
    - Food empties into the small intestine at the pyloric sphincter
    - Volume 50 mls to 4 litres
  18. 18—
  19. 19Stomach• Muscularis externa
    • Has a third layer = oblique
    • Allows the stomach to Propulsion in the Stomach churn, mix, and pummel food physically
    • Breaks down food into smaller fragments
    • CHYME
  20. 20Propulsion in the Stomach-  Food must first be well mixed
    - Rippling peristalsis occurs in the lower stomach
    - The pylorus lets out chyme into the small intestine (3 mls at a time)
    - The stomach empties in four to six hours
  21. 21Stomach mucosa• Mucosa is composed of:
    – Goblet cells that produce a coat of alkaline mucus
    –The mucous surface layer traps a bicarbonate-rich fluid beneath it
    – To protect from self
    – digesting
    – Gastric pits
  22. 22Gastric pits lead to gastric glands• Gastric glands have a variety of secretory cells:
    - Mucous neck cells – secrete mucous
    - Parietal cells – secrete HCl and intrinsic factor - Chief cells – produce pepsinogen
    • Pepsinogen is activated to pepsin by:
    - HCl in the stomach
    - Pepsin itself via a positive feedback
    mechanism
  23. 23Stomach Functions- Acts as a storage tank for food
    - Site of food breakdown (churning)
    - Secretion of gastric juice
    - Chemical breakdown of protein begins
    - No absorption
    - Delivers chyme (processed food) to the small intestine
    - Secretes intrinsic factor required for absorption of vitamin B12
  24. 24Digestion and Absorption in the Stomach Protein digestion enzymes
     Pepsin – an active protein digesting enzyme
     The only absorption that occurs in the stomach is of alcohol and aspirin
  25. 25Small Intestine
    Subdivisions of the small intestine
     Duodenum - 25 cms
     Jejunum – 2.5 ms
     Ileum – 3.6 ms
     The bile duct and main pancreatic duct empty secretions into the small intestine at the duodenum
  26. 26Anatomy of Small Intestine Folds called circular folds or plicae circulare
     Designed for absorption and large folds designed to slow down passage of chyme
     Villi - fingerlike structures formed by the mucosa
     Give the small intestine more surface area - absorption
  27. 27Villi of the Small Intestine Between villi are pits containing glands that secrete intestinial juices.
     Villi, in turn, have microvilli which secrete enzymes (brush border enzymes)
  28. 28Microvilli Of The Small Intestine Microvilli = Small projections of the plasma membrane of the absorptive cells
     Brush border enzymes
  29. 29Pancreas – pancreatic juice Produces a wide spectrum of digestive enzymes that break down all categories of food
     Enzymes are secreted into the duodenum
     Alkaline fluid (bicarbonate) introduced with
    enzymes neutralizes stomach contents
     Endocrine products of pancreas - control blood glucose levels
     Insulin - blood glucose high (after meal).
     Glucagon - blood glucose low (between meals)
  30. 30Liver Largest gland in the body
     Metabolic and regulatory roles
     Digestive role to produce bile
  31. 31Bile Produced by cells in the liver
     Gallbladderstoresand concentrates bile from the liver
     Bile is introduced into the duodenum in the presence of fatty food - emulsifies fat to aid enzymatic breakdown
  32. 32Propulsion in the Small Intestine Peristalsis is the major means of moving food
     3-6 hour journey through small intestine  Segmentation movements
     Mix chyme with digestive juices
     Aid in propelling food
  33. 33Chemical Digestion in the Small Intestine Most chemical digestion occurs in the small intestine
     Source of enzymes that are mixed with chyme to give intestinal juice
    Pancreas = pancreatic juice
    Intestinal cells - brush border enzymes
     Bile enters from the gall bladder
  34. 34Chemical digestion - CarbohydratesChemical digestion - Carbohydrates
  35. 35Chemical digestion - ProteinChemical digestion - Protein
  36. 36Chemical digestion - FatsChemical digestion - Fats
  37. 37Chemical digestionUnemulsified Fats (lipids)
    • Bile enters small intestine from the gall bladder
    • Bile emulsifies the fat this allows enzymes to start fat breakdown
    • Pancreatic lipase from the pancreas enters the small intestine
    • Pancreatic lipase aids in breaking down the fat.
  38. 38Absorption of digested food components. A• Carbohydrates-finalbreakdownproducts
    • Monosaccharides - glucose, galactose, fructose enter
    the capillaries of the villi
    • via co-transport with Na+, and facilitated diffusion
  39. 39Absorption of digested food components. B• Protein-finalbreakdownproducts
    • Amino acids enter the capillary of the villi
    • Both monosaccharides and amino acids are transported to the liver by the hepatic portal vein
  40. 40Absorption of digested food components• Fat - final breakdown products
    • Fatty acids and glycerol are absorbed into the lacteal of the villi as a chylomicron
    • Enters the lymphatic system
    • Lymph is drained back into blood at the thoracic duct
    • Fatty acids then enter the liver for distribution to other body areas.
  41. 41Brushborder enzymes Found in the microvilli
     Final breakdown to produce single units ready for absorption
  42. 42Structures Involved in Absorption of Nutrients Absorptive cells
     Blood capillaries
     Lacteals (specialized lymphatic capillaries)
  43. 43Large Intestine Larger in diameter, but shorter than the small intestine
     Frames the internal abdomen
     Subdivisions:
     Cecum
     Appendix
     Colon
     Rectum
     Anal canal
  44. 44ColonDistinct regions:
     Ascending
     Transverse
     Descending
     Sigmoid
    Goblet cell – mucus
    Longitudinal muscle – teniae coli
    Haustra
  45. 45Food Breakdown and Absorption in the Large Intestine No digestive enzymes are produced
     Resident bacteria digest remaining nutrients
     Produce some vitamin K and B
     Release gases approx 500ml/day
     Water and vitamins K and B are absorbed  Remaining materials are eliminated = feces
     Undigested food, mucus, bacteria, water
  46. 46Propulsion in the Large Intestine Residue moves along slowly in 12 -24 hours
     Haustral contractions
     Mass movements
    Slow, powerful movements
     Occur three to four times per day
     Presence of feces in the rectum causes a defecation reflex
  47. 47Defecation reflex• Rectum is generally empty
    • Mass movements force feces into rectum and
    stretch the wall - signals the defecation reflex
    • Internal sphincter relax (involuntary)
    • External sphincter remains closed (voluntary)
    • If convenient defecation can occur - voluntary relaxation of external sphincter
    • If not convenient, defecation can be delayed temporarily

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Beschreibung
5 HAP 1 Karteikarten am Digestive System, erstellt von Jonathan Cash am 21/10/2015.
Erstellt von
Jonathan Cash · Okt 2015
Aktualisiert
4 Feb 2018
Aufrufe
1
Tags
hap1
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