Digestive Tract <ul><li>Gastrointestinal   ( GI )   tract  or  alimentary canal </li></ul><ul><li>Is a muscular tube </li>...
6 Functions of the Digestive System   <ul><li>Ingestion :  </li></ul><ul><ul><li>occurs when materials enter digestive tra...
<ul><li>Secretion : </li></ul><ul><ul><li>is the release of water, acids, enzymes, buffers, and salts  </li></ul></ul><ul>...
Lining of the Digestive Tract <ul><li>Protects surrounding tissues against: </li></ul><ul><ul><li>corrosive effects of dig...
Histological Organization of the Digestive Tract <ul><li>Major layers of the digestive tract: </li></ul><ul><ul><li>mucosa...
The Mucosa <ul><li>Is the inner lining of digestive tract </li></ul><ul><li>Is a  mucous membrane  consisting of: </li></u...
Lining of Digestive Tract <ul><li>Folding increases surface area for absorption:  </li></ul><ul><ul><li>longitudinal folds...
<ul><li>Consists of a layer of areolar tissue that contains: </li></ul><ul><ul><li>blood vessels </li></ul></ul><ul><ul><l...
Muscularis Mucosae <ul><li>Narrow band of smooth muscle and elastic fibers in lamina propria </li></ul><ul><li>Smooth musc...
The  Submucosa <ul><li>Is a layer of dense irregular connective tissue </li></ul><ul><li>Surrounds muscularis mucosae </li...
Submucosal Plexus   <ul><li>Also called  plexus of Meissner </li></ul><ul><li>Innervates the mucosa and submucosa </li></ul>
Muscularis Externa Structure <ul><li>Is dominated by smooth muscle cells </li></ul><ul><li>Involved in: </li></ul><ul><ul>...
The  Serosa <ul><li>Serous membrane covering muscularis externa: </li></ul><ul><ul><li>except in oral cavity, pharynx, eso...
The Movement of Digestive Materials <ul><li>By muscular layers of digestive tract: </li></ul><ul><ul><li>consist of viscer...
Pacesetter Cells <ul><li>Located in muscularis mucosae and muscularis externa: </li></ul><ul><ul><li>surrounding lumen of ...
Peristalsis <ul><li>Consists of waves of muscular contractions </li></ul><ul><li>Moves a bolus along the length of the dig...
Peristaltic Motion <ul><li>Circular muscles contract behind bolus: </li></ul><ul><ul><li>while circular muscles ahead of b...
Segmentation <ul><li>Cycles of contraction: </li></ul><ul><ul><li>Churn and fragment bolus </li></ul></ul><ul><ul><li>mix ...
Control of Digestive Function <ul><li>Neural mechanisms </li></ul><ul><li>Hormonal mechanisms </li></ul><ul><li>Local mech...
Neural Mechanisms <ul><li>Control: </li></ul><ul><ul><li>movement of materials along digestive tract </li></ul></ul><ul><u...
Digestive Hormones Mechanisms <ul><li>At least 18 hormones that affect: </li></ul><ul><ul><li>most aspects of digestive fu...
Local Mechanisms <ul><li>Prostaglandins, histamine, and other chemicals </li></ul><ul><li>Released into interstitial fluid...
Chemical Events in Digestion Figure 24–26
Processing Nutrients <ul><li>The digestive system: </li></ul><ul><ul><li>breaks down physical structure of food </li></ul>...
Digestive Enzymes <ul><li>Are secreted by: </li></ul><ul><ul><li>salivary glands </li></ul></ul><ul><ul><li>tongue </li></...
<ul><li>Are divided into classes by targets: </li></ul><ul><ul><li>carbohydrases : </li></ul></ul><ul><ul><ul><li>break bo...
Figure 24.1  The Components of the Digestive System Figure 24.1
<ul><li>Ingestion </li></ul><ul><li>Mechanical processing </li></ul><ul><li>Digestion </li></ul><ul><li>Secretion </li></u...
Figure 24.3  The Structure of the Digestive Tract Figure 24.3
<ul><li>Visceral smooth muscle shows rhythmic cycles of activity </li></ul><ul><ul><li>Pacemaker cells </li></ul></ul><ul>...
Figure 24.4  Peristalsis Figure 24.4
<ul><li>Movement of materials along the digestive tract is controlled by: </li></ul><ul><ul><li>Neural mechanisms  </li></...
Figure 24.5  The Regulation of Digestive Activities Figure 24.5
Figure 24.21  The Gallbladder Figure 24.21a, b
<ul><li>Neural and hormonal mechanisms coordinate glands </li></ul><ul><li>GI activity stimulated by parasympathetic inner...
Figure 24.22  The Activities of Major Digestive Tract Hormones Figure 24.22
GI System--Structure <ul><li>Mouth </li></ul><ul><li>Esophagus </li></ul><ul><li>Stomach </li></ul><ul><li>Small Intestine...
GI System--Structure <ul><li>GI tract is about 30 feet long from mouth to anus </li></ul><ul><li>Layers from inner to oute...
GI System--Structure <ul><li>Innervation </li></ul><ul><ul><li>Sympathetic-inhibitory </li></ul></ul><ul><ul><li>Parasympa...
GI System--Structure <ul><li>GI tract receives 25-30% of cardiac output </li></ul><ul><li>Venous blood empties into portal...
GI System--Structure <ul><li>Two types of movement </li></ul><ul><ul><li>Mixing (Segmentation) </li></ul></ul><ul><ul><li>...
GI System--Structure <ul><li>Abdominal organs are covered by peritoneum </li></ul><ul><li>Two layers of peritoneum </li></...
GI System—Intrinsic/Enteric layer  <ul><li>GI tract has its own nervous system </li></ul><ul><li>Enteric or intrinsic </li...
GI System-Function <ul><li>Supply nutrients to body cells </li></ul><ul><ul><li>Ingestion (taking in) and propulsion (move...
GI System-Function/Ingestion <ul><li>Swallowing (deglutition)-mechanical component of ingestion </li></ul><ul><li>Mouth </...
GI System-Function/Ingestion <ul><li>Pharynx </li></ul><ul><li>Esophagus </li></ul><ul><ul><li>Upper third – striated musc...
GI System-Digestion/Absorption <ul><li>Digestion is mechanical and chemical </li></ul><ul><li>Mouth </li></ul><ul><ul><li>...
GI System-Digestion/Absorption-Stomach <ul><li>Parts of stomach </li></ul><ul><ul><li>Fundus </li></ul></ul><ul><ul><ul><l...
GI System-Digestion/Absorption-Stomach <ul><li>Pylorus </li></ul><ul><ul><li>Small portion of antrum </li></ul></ul><ul><u...
GI System-Digestion/Absorption-Small Intestine <ul><li>Two functions </li></ul><ul><ul><li>Digestion </li></ul></ul><ul><u...
GI System-Digestion/Absorption-Small Intestine <ul><li>Villi </li></ul><ul><ul><li>Functional units of small intestine </l...
GI System-Physiology of Digestion <ul><li>Salivary gland-breakdown of starch </li></ul><ul><li>Stomach-releases of pepsino...
GI System-Physiology of Digestion-Small Intestine <ul><li>Carbohydrates broken down into monosaccharides </li></ul><ul><ul...
GI System-Physiology of Digestion-Small Intestine <ul><li>Enzymes secreted from pancreas </li></ul><ul><li>Bile from liver...
GI System-Physiology of Elimination-Large Intestine <ul><li>5-6 feet long </li></ul><ul><li>Four parts </li></ul><ul><ul><...
GI System-Physiology of Elimination-Large Intestine <ul><li>Forms feces until defecation </li></ul><ul><li>Feces </li></ul...
GI System-Physiology of Elimination-Large Intestine <ul><li>Bacteria- </li></ul><ul><ul><li>Responsible for breakdown of p...
Physiology of Elimination-Liver  <ul><li>Largest internal organ in body </li></ul><ul><li>Right and left lobes </li></ul><...
Physiology of Elimination-Biliary Tract <ul><li>Consists of </li></ul><ul><ul><li>Gallbladder-concentrate, store bile </li...
Physiology of Elimination-Biliary Tract <ul><li>Bilirubin metabolism </li></ul><ul><li>Breakdown of Hemoglobin </li></ul><...
Physiology of Elimination-Pancreas <ul><li>Exocrine and endocrine functions </li></ul><ul><li>Exocrine-digestion-pancreati...
GI System and Aging <ul><li>Periodontal disease-loss of teeth </li></ul><ul><li>Taste buds, smell, salivary secretions dec...
GI System-Factors that Influence Function <ul><li>Stress/anxiety </li></ul><ul><li>Dietary intake </li></ul><ul><li>Ingest...
Chapter 21,  part A Digestion
About this Chapter <ul><li>Overview of the digestive system & how it is organized </li></ul><ul><li>How products are moved...
Processes of the Digestive System: Overview <ul><li>Ingestion </li></ul><ul><li>Digestion:  enzymatic </li></ul><ul><li>Mo...
Digestive Anatomy: Overview <ul><li>Oral cavity </li></ul><ul><li>Salivary glands </li></ul><ul><li>Esophagus </li></ul><u...
Digestive Anatomy: Overview Figure 21-2a: ANATOMY SUMMARY: The Digestive System
More Digestive Anatomy <ul><li>Small intestine </li></ul><ul><ul><li>Duodenum </li></ul></ul><ul><ul><li>Jejunum </li></ul...
Digestive Anatomy: Histological Overview <ul><li>Stomach wall </li></ul><ul><ul><li>Mucosa </li></ul></ul><ul><ul><li>Gast...
Digestive Anatomy: Histological Overview Figure 21-2c: ANATOMY SUMMARY: The Digestive System
Digestive Anatomy: Histological Overview Figure 21-2e: ANATOMY SUMMARY: The Digestive System
Motility: Smooth Muscle Contractions <ul><li>Tonic – support </li></ul><ul><li>Phasic – move products </li></ul><ul><ul><l...
Digestive Secretions:  (  7 L / Day From Tissues into Lumen) <ul><li>Salivary glands </li></ul><ul><li>Pancreas </li></ul...
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G I T Lecture; Intro

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G I T Lecture; Intro

  1. 2. Digestive Tract <ul><li>Gastrointestinal ( GI ) tract or alimentary canal </li></ul><ul><li>Is a muscular tube </li></ul><ul><li>Extends from oral cavity to anus </li></ul>Components of the Digestive System
  2. 3. 6 Functions of the Digestive System <ul><li>Ingestion : </li></ul><ul><ul><li>occurs when materials enter digestive tract via the mouth </li></ul></ul><ul><li>Mechanical processing : </li></ul><ul><ul><li>crushing and shearing </li></ul></ul><ul><ul><li>makes materials easier to propel along digestive tract </li></ul></ul><ul><li>Digestion : </li></ul><ul><ul><li>is the chemical breakdown of food </li></ul></ul><ul><ul><li>into small organic fragments </li></ul></ul><ul><ul><li>for absorption by digestive epithelium </li></ul></ul>
  3. 4. <ul><li>Secretion : </li></ul><ul><ul><li>is the release of water, acids, enzymes, buffers, and salts </li></ul></ul><ul><ul><li>by epithelium of digestive tract </li></ul></ul><ul><ul><li>by glandular organs </li></ul></ul><ul><li>Absorption : </li></ul><ul><ul><li>movement of organic substrates, electrolytes, vitamins, and water </li></ul></ul><ul><ul><li>across digestive epithelium </li></ul></ul><ul><ul><li>into interstitial fluid of digestive tract </li></ul></ul><ul><li>Excretion : </li></ul><ul><ul><li>removal of waste products from body fluids </li></ul></ul>
  4. 5. Lining of the Digestive Tract <ul><li>Protects surrounding tissues against: </li></ul><ul><ul><li>corrosive effects of digestive acids and enzymes </li></ul></ul><ul><ul><li>mechanical stresses, such as abrasion </li></ul></ul><ul><ul><li>bacteria </li></ul></ul><ul><ul><ul><li>Is ingested with food or resides in digestive tract </li></ul></ul></ul><ul><ul><ul><li>Attacked by macrophages, and immune system cells </li></ul></ul></ul><ul><ul><ul><li>In lamina propria (underlying layer of areolar tissue) </li></ul></ul></ul>
  5. 6. Histological Organization of the Digestive Tract <ul><li>Major layers of the digestive tract: </li></ul><ul><ul><li>mucosa </li></ul></ul><ul><ul><li>submucosa </li></ul></ul><ul><ul><li>muscularis externa </li></ul></ul><ul><ul><li>serosa </li></ul></ul>
  6. 7. The Mucosa <ul><li>Is the inner lining of digestive tract </li></ul><ul><li>Is a mucous membrane consisting of: </li></ul><ul><ul><li>epithelium, moistened by glandular secretions </li></ul></ul><ul><li>Lamina propria composed of areolar tissue </li></ul>
  7. 8. Lining of Digestive Tract <ul><li>Folding increases surface area for absorption: </li></ul><ul><ul><li>longitudinal folds, disappear as digestive tract fills </li></ul></ul><ul><ul><li>permanent transverse folds ( plicae ) </li></ul></ul>
  8. 9. <ul><li>Consists of a layer of areolar tissue that contains: </li></ul><ul><ul><li>blood vessels </li></ul></ul><ul><ul><li>sensory nerve endings </li></ul></ul><ul><ul><li>lymphatic vessels </li></ul></ul><ul><ul><li>smooth muscle cells </li></ul></ul><ul><ul><li>scattered areas of lymphoid tissue </li></ul></ul>The Lamina Propria
  9. 10. Muscularis Mucosae <ul><li>Narrow band of smooth muscle and elastic fibers in lamina propria </li></ul><ul><li>Smooth muscle cells arranged in 2 concentric layers: </li></ul>
  10. 11. The Submucosa <ul><li>Is a layer of dense irregular connective tissue </li></ul><ul><li>Surrounds muscularis mucosae </li></ul><ul><li>Has large blood vessels and lymphatic vessels </li></ul><ul><li>May contain exocrine glands: </li></ul><ul><ul><li>secrete buffers and enzymes into digestive tract </li></ul></ul>
  11. 12. Submucosal Plexus <ul><li>Also called plexus of Meissner </li></ul><ul><li>Innervates the mucosa and submucosa </li></ul>
  12. 13. Muscularis Externa Structure <ul><li>Is dominated by smooth muscle cells </li></ul><ul><li>Involved in: </li></ul><ul><ul><li>mechanical processing </li></ul></ul><ul><ul><li>movement of materials along digestive tract </li></ul></ul><ul><li>Movements coordinated by enteric nervous system (ENS) </li></ul>
  13. 14. The Serosa <ul><li>Serous membrane covering muscularis externa: </li></ul><ul><ul><li>except in oral cavity, pharynx, esophagus, and rectum </li></ul></ul>
  14. 15. The Movement of Digestive Materials <ul><li>By muscular layers of digestive tract: </li></ul><ul><ul><li>consist of visceral smooth muscle tissue </li></ul></ul>Smooth Muscle <ul><li>Along digestive tract: </li></ul><ul><ul><li>has rhythmic cycles of activity </li></ul></ul><ul><ul><li>controlled by pacesetter cells </li></ul></ul><ul><li>Cells undergo spontaneous depolarization: </li></ul><ul><ul><li>triggering wave of contraction through entire muscular sheet </li></ul></ul>
  15. 16. Pacesetter Cells <ul><li>Located in muscularis mucosae and muscularis externa: </li></ul><ul><ul><li>surrounding lumen of digestive tract </li></ul></ul>
  16. 17. Peristalsis <ul><li>Consists of waves of muscular contractions </li></ul><ul><li>Moves a bolus along the length of the digestive tract </li></ul>Figure 24–4 <ul><li>Bolus is a small, oval mass of digestive contents </li></ul>
  17. 18. Peristaltic Motion <ul><li>Circular muscles contract behind bolus: </li></ul><ul><ul><li>while circular muscles ahead of bolus relax </li></ul></ul><ul><li>Longitudinal muscles ahead of bolus contract: </li></ul><ul><ul><li>shortening adjacent segments </li></ul></ul><ul><li>Wave of contraction in circular muscles: </li></ul><ul><ul><li>forces bolus forward </li></ul></ul>
  18. 19. Segmentation <ul><li>Cycles of contraction: </li></ul><ul><ul><li>Churn and fragment bolus </li></ul></ul><ul><ul><li>mix contents with intestinal secretions </li></ul></ul><ul><li>Does not follow a set pattern: </li></ul><ul><ul><li>does not push materials in any 1 direction </li></ul></ul>
  19. 20. Control of Digestive Function <ul><li>Neural mechanisms </li></ul><ul><li>Hormonal mechanisms </li></ul><ul><li>Local mechanisms </li></ul>
  20. 21. Neural Mechanisms <ul><li>Control: </li></ul><ul><ul><li>movement of materials along digestive tract </li></ul></ul><ul><ul><li>secretory functions </li></ul></ul><ul><li>Motor neurons: </li></ul><ul><ul><li>control smooth muscle contraction and glandular secretion </li></ul></ul><ul><ul><li>located in myenteric plexus </li></ul></ul>
  21. 22. Digestive Hormones Mechanisms <ul><li>At least 18 hormones that affect: </li></ul><ul><ul><li>most aspects of digestive function </li></ul></ul><ul><ul><li>activities of other systems </li></ul></ul><ul><li>Are peptides </li></ul><ul><li>Are produced by enteroendocrine cells in digestive tract </li></ul><ul><li>Reach target organs after distribution in bloodstream </li></ul>
  22. 23. Local Mechanisms <ul><li>Prostaglandins, histamine, and other chemicals </li></ul><ul><li>Released into interstitial fluid </li></ul><ul><li>Affect adjacent cells within small segment of digestive tract </li></ul><ul><li>Coordinating response to changing conditions: </li></ul><ul><ul><li>e.g., variations in local pH, chemical, or physical stimuli </li></ul></ul><ul><li>Affect only a portion of tract </li></ul>
  23. 24. Chemical Events in Digestion Figure 24–26
  24. 25. Processing Nutrients <ul><li>The digestive system: </li></ul><ul><ul><li>breaks down physical structure of food </li></ul></ul><ul><ul><li>disassembles component molecules </li></ul></ul><ul><li>Molecules released into bloodstream are: </li></ul><ul><ul><li>absorbed by cells </li></ul></ul><ul><li>Broken down to provide energy for ATP synthesis: </li></ul><ul><ul><li>used to synthesize carbohydrates, proteins, and lipids </li></ul></ul>
  25. 26. Digestive Enzymes <ul><li>Are secreted by: </li></ul><ul><ul><li>salivary glands </li></ul></ul><ul><ul><li>tongue </li></ul></ul><ul><ul><li>stomach </li></ul></ul><ul><ul><li>pancreas </li></ul></ul><ul><li>Break molecular bonds in large organic molecules: </li></ul><ul><ul><li>carbohydrates, proteins, lipids, and nucleic acids </li></ul></ul><ul><ul><li>in a process called hydrolysis </li></ul></ul>
  26. 27. <ul><li>Are divided into classes by targets: </li></ul><ul><ul><li>carbohydrases : </li></ul></ul><ul><ul><ul><li>break bonds between simple sugars </li></ul></ul></ul><ul><ul><li>proteases : </li></ul></ul><ul><ul><ul><li>break bonds between amino acids </li></ul></ul></ul><ul><ul><li>lipases : </li></ul></ul><ul><ul><ul><li>separate fatty acids from glycerides </li></ul></ul></ul>
  27. 28. Figure 24.1 The Components of the Digestive System Figure 24.1
  28. 29. <ul><li>Ingestion </li></ul><ul><li>Mechanical processing </li></ul><ul><li>Digestion </li></ul><ul><li>Secretion </li></ul><ul><li>Absorption </li></ul><ul><li>Excretion </li></ul>Functions of the digestive system
  29. 30. Figure 24.3 The Structure of the Digestive Tract Figure 24.3
  30. 31. <ul><li>Visceral smooth muscle shows rhythmic cycles of activity </li></ul><ul><ul><li>Pacemaker cells </li></ul></ul><ul><li>Peristalsis </li></ul><ul><ul><li>Waves that move a bolus </li></ul></ul><ul><li>Segmentation </li></ul><ul><ul><li>Churn and fragment a bolus </li></ul></ul>Movement of digestive materials
  31. 32. Figure 24.4 Peristalsis Figure 24.4
  32. 33. <ul><li>Movement of materials along the digestive tract is controlled by: </li></ul><ul><ul><li>Neural mechanisms </li></ul></ul><ul><ul><ul><li>Parasympathetic and local reflexes </li></ul></ul></ul><ul><ul><li>Hormonal mechanisms </li></ul></ul><ul><ul><ul><li>Enhance or inhibit smooth muscle contraction </li></ul></ul></ul><ul><ul><li>Local mechanisms </li></ul></ul><ul><ul><ul><li>Coordinate response to changes in pH or chemical stimuli </li></ul></ul></ul>Control of the digestive system
  33. 34. Figure 24.5 The Regulation of Digestive Activities Figure 24.5
  34. 35. Figure 24.21 The Gallbladder Figure 24.21a, b
  35. 36. <ul><li>Neural and hormonal mechanisms coordinate glands </li></ul><ul><li>GI activity stimulated by parasympathetic innervation </li></ul><ul><ul><li>Inhibited by sympathetic innervation </li></ul></ul><ul><li>Enterogastric, gastroenteric and gastroileal reflexes coordinate stomach and intestines </li></ul>Coordination secretion and absorption
  36. 37. Figure 24.22 The Activities of Major Digestive Tract Hormones Figure 24.22
  37. 38. GI System--Structure <ul><li>Mouth </li></ul><ul><li>Esophagus </li></ul><ul><li>Stomach </li></ul><ul><li>Small Intestine </li></ul><ul><li>Large intestine </li></ul><ul><li>Rectum </li></ul><ul><li>Anus </li></ul>
  38. 39. GI System--Structure <ul><li>GI tract is about 30 feet long from mouth to anus </li></ul><ul><li>Layers from inner to outer </li></ul><ul><ul><li>Mucosa </li></ul></ul><ul><ul><li>Submucosa </li></ul></ul><ul><ul><li>Muscle- 2 layers </li></ul></ul><ul><ul><ul><li>Circular (inner) </li></ul></ul></ul><ul><ul><ul><li>Longitudinal (Outer) </li></ul></ul></ul><ul><ul><li>Serosa except esophagus (fibrous) </li></ul></ul>
  39. 40. GI System--Structure <ul><li>Innervation </li></ul><ul><ul><li>Sympathetic-inhibitory </li></ul></ul><ul><ul><li>Parasympathetic-excitatory </li></ul></ul><ul><ul><li>Example: </li></ul></ul><ul><ul><ul><li>Peristalsis is increased with parasympathetic stimulation </li></ul></ul></ul>
  40. 41. GI System--Structure <ul><li>GI tract receives 25-30% of cardiac output </li></ul><ul><li>Venous blood empties into portal vein which peruses liver </li></ul><ul><li>Upper portion of GI tract receives blood from splanchic artery </li></ul><ul><li>Small intestine receives blood from hepatic and mesentery arteries </li></ul><ul><li>Large intestine receives blood supply from superior and inferior mesenteric arteries </li></ul>
  41. 42. GI System--Structure <ul><li>Two types of movement </li></ul><ul><ul><li>Mixing (Segmentation) </li></ul></ul><ul><ul><li>Propulsion (Peristalsis) </li></ul></ul><ul><ul><li>Hormones and enzymes for digestion </li></ul></ul><ul><ul><li>Mucous provides protection, lubrication, water, electrolytes </li></ul></ul>
  42. 43. GI System--Structure <ul><li>Abdominal organs are covered by peritoneum </li></ul><ul><li>Two layers of peritoneum </li></ul><ul><ul><li>Parietal-lines abdominal cavity wall </li></ul></ul><ul><ul><li>Visceral-covers abdominal organs </li></ul></ul><ul><ul><li>Peritoneal cavity- space between parietal and visceral </li></ul></ul><ul><ul><li>Two folds of peritoneum </li></ul></ul><ul><ul><ul><li>Mesentery-attaches small intestine to posterior abdominal wall </li></ul></ul></ul><ul><ul><ul><li>Lesser omentum-hangs from stomach like apron, contains fat and lymph nodes </li></ul></ul></ul>
  43. 44. GI System—Intrinsic/Enteric layer <ul><li>GI tract has its own nervous system </li></ul><ul><li>Enteric or intrinsic </li></ul><ul><li>Two intrinsic layers </li></ul><ul><ul><li>Lies between mucosa and the circular muscle layer </li></ul></ul><ul><ul><li>Other layer lies between circular and longitudinal layer </li></ul></ul><ul><li>Innervation contributes to coordination of GI motor and secretory activities </li></ul><ul><li>Enteric nervous system is also known as the “gut brain” </li></ul><ul><li>Ability to control movement and secretion of GI tract </li></ul>
  44. 45. GI System-Function <ul><li>Supply nutrients to body cells </li></ul><ul><ul><li>Ingestion (taking in) and propulsion (movement) </li></ul></ul><ul><ul><li>Digestion-breakdown </li></ul></ul><ul><ul><li>Absorption—transfer of food products into circulation </li></ul></ul><ul><ul><li>Elimination-Excreting waste products </li></ul></ul>
  45. 46. GI System-Function/Ingestion <ul><li>Swallowing (deglutition)-mechanical component of ingestion </li></ul><ul><li>Mouth </li></ul><ul><ul><li>Lips </li></ul></ul><ul><ul><li>Oral cavity </li></ul></ul><ul><ul><ul><li>Three pairs of salivary glands </li></ul></ul></ul><ul><ul><ul><ul><li>Parotid </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Submaxillary </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Sublingual </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Glands produce saliva (water, protein, mucin, salts, amylase(pytalin)) </li></ul></ul></ul></ul>
  46. 47. GI System-Function/Ingestion <ul><li>Pharynx </li></ul><ul><li>Esophagus </li></ul><ul><ul><li>Upper third – striated muscle </li></ul></ul><ul><ul><li>Distal two thirds-smooth muscle </li></ul></ul><ul><ul><li>With swallowing, peristaltic wave moves bolus into esophagus </li></ul></ul><ul><ul><li>Lower esophageal sphincter (LES) remains contracted except when swallowing, vomiting, or belching </li></ul></ul><ul><ul><li>LES-important barrier that prevents acid reflux from stomach </li></ul></ul>
  47. 48. GI System-Digestion/Absorption <ul><li>Digestion is mechanical and chemical </li></ul><ul><li>Mouth </li></ul><ul><ul><li>Lubricates and softens mass </li></ul></ul><ul><li>Stomach </li></ul><ul><ul><li>Stores food </li></ul></ul><ul><ul><li>Mixes food with gastric secretions </li></ul></ul><ul><ul><li>Empties contents into small intestine </li></ul></ul>
  48. 49. GI System-Digestion/Absorption-Stomach <ul><li>Parts of stomach </li></ul><ul><ul><li>Fundus </li></ul></ul><ul><ul><ul><li>Chief cells (secrete pesinogen) </li></ul></ul></ul><ul><ul><ul><li>Parietal cells (secrete HCL, water, and intrinsic factor) </li></ul></ul></ul><ul><ul><ul><li>Acid Ph protects against ingested organisms </li></ul></ul></ul><ul><ul><ul><li>Intrinsic factor promotes cyclocobalamin (B 12) absorption in the small intestine </li></ul></ul></ul><ul><ul><li>Body </li></ul></ul><ul><ul><li>Antrum </li></ul></ul>
  49. 50. GI System-Digestion/Absorption-Stomach <ul><li>Pylorus </li></ul><ul><ul><li>Small portion of antrum </li></ul></ul><ul><ul><li>Lies proximal to pyloric sphincter </li></ul></ul><ul><ul><li>Pyloric sphincter guards entrance to and from entrance to stomach </li></ul></ul><ul><ul><li>Rugae-folds in stomach, contains glands </li></ul></ul>
  50. 51. GI System-Digestion/Absorption-Small Intestine <ul><li>Two functions </li></ul><ul><ul><li>Digestion </li></ul></ul><ul><ul><li>Absorption-uptake of nutrients from gut to bloodstream </li></ul></ul><ul><ul><li>Approximately 23 feet long </li></ul></ul><ul><ul><li>Extends from pylorus to ileo cecal valve (prevents reflux from small intestine to large intestine) </li></ul></ul><ul><ul><li>Large surface area for absorption </li></ul></ul>
  51. 52. GI System-Digestion/Absorption-Small Intestine <ul><li>Villi </li></ul><ul><ul><li>Functional units of small intestine </li></ul></ul><ul><ul><li>Contains goblet cells </li></ul></ul><ul><ul><ul><li>Secrete mucous </li></ul></ul></ul><ul><ul><li>Epithelial cells </li></ul></ul><ul><ul><ul><li>Produce digestive enzymes </li></ul></ul></ul><ul><ul><li>Mirovilli-assist villi to increase surface area </li></ul></ul><ul><ul><li>Crypts of Liberkuhn-contain base columnar cells </li></ul></ul><ul><ul><li>Brunner’s glands-secrete mucous in duodenum </li></ul></ul>
  52. 53. GI System-Physiology of Digestion <ul><li>Salivary gland-breakdown of starch </li></ul><ul><li>Stomach-releases of pepsinogen from chief cells </li></ul><ul><li>Acid in stomach converts of pepsinogen in to pepsin-initial breakdown of proteins </li></ul><ul><li>Stomach has minimal impact on breakdown of starches and fat </li></ul><ul><li>Food stays in stomach 3-4 hours </li></ul>
  53. 54. GI System-Physiology of Digestion-Small Intestine <ul><li>Carbohydrates broken down into monosaccharides </li></ul><ul><ul><li>Fats to glycerol </li></ul></ul><ul><ul><li>Proteins to amino acids </li></ul></ul><ul><ul><li>Chyme (food mixed with gastric secretions) </li></ul></ul>
  54. 55. GI System-Physiology of Digestion-Small Intestine <ul><li>Enzymes secreted from pancreas </li></ul><ul><li>Bile from liver </li></ul><ul><li>Intestinal secretions </li></ul><ul><li>Hormones secretin stimulates pancreas to produce bicarb (neutralizes acid in chyme) </li></ul><ul><li>Duodenum secretes mucous to protect small intestine from acid </li></ul><ul><li>Hormone cholecystokinin stimulates gall bladder contraction and relaxation of the sphincter of Oddi-bile released-digest fat </li></ul>
  55. 56. GI System-Physiology of Elimination-Large Intestine <ul><li>5-6 feet long </li></ul><ul><li>Four parts </li></ul><ul><ul><li>Cecum and Appendix </li></ul></ul><ul><ul><li>Colon </li></ul></ul><ul><ul><li>Rectum </li></ul></ul><ul><ul><li>Anus </li></ul></ul><ul><li>Most important function-absorption of water and electrolytes </li></ul>
  56. 57. GI System-Physiology of Elimination-Large Intestine <ul><li>Forms feces until defecation </li></ul><ul><li>Feces </li></ul><ul><ul><li>Water </li></ul></ul><ul><ul><li>Bacteria </li></ul></ul><ul><ul><li>Unabsorbed minerals </li></ul></ul><ul><ul><li>Undigested food </li></ul></ul><ul><ul><li>Bile pigment </li></ul></ul><ul><ul><li>Epithelial cells </li></ul></ul>
  57. 58. GI System-Physiology of Elimination-Large Intestine <ul><li>Bacteria- </li></ul><ul><ul><li>Responsible for breakdown of proteins not digested by small intestine </li></ul></ul><ul><ul><li>Synthesize Vitamin K and some B vitamins </li></ul></ul><ul><ul><li>Production of flatus </li></ul></ul><ul><ul><li>Slow movement-haustral churning </li></ul></ul><ul><ul><li>Defecation </li></ul></ul><ul><ul><ul><li>Voluntary and involuntary muscles </li></ul></ul></ul><ul><ul><ul><li>Valsalva maneuver </li></ul></ul></ul>
  58. 59. Physiology of Elimination-Liver <ul><li>Largest internal organ in body </li></ul><ul><li>Right and left lobes </li></ul><ul><li>Lobules-functional unit </li></ul><ul><ul><li>Rows of hepatic cells (hepatocytes) </li></ul></ul><ul><ul><li>Kupfer cells-phagocytic activity-removes toxins/bacteria from blood </li></ul></ul><ul><ul><li>Portal circulatory system brings blood to liver from stomach, intestine </li></ul></ul><ul><ul><li>Involved in metabolism, detoxification, destruction of RBC </li></ul></ul>
  59. 60. Physiology of Elimination-Biliary Tract <ul><li>Consists of </li></ul><ul><ul><li>Gallbladder-concentrate, store bile </li></ul></ul><ul><ul><li>Duct system </li></ul></ul><ul><ul><li>Bile-produced by hepatic cells </li></ul></ul><ul><ul><li>Moves down common bile duct, enters duodenum at ampulla of Vater </li></ul></ul><ul><ul><li>In intestine, bilirubin converts to stercobilirubin (color of stool) and urobilirubin (color of urine) </li></ul></ul><ul><ul><li>Sphincter of Oddi keeps ampulla closed </li></ul></ul>
  60. 61. Physiology of Elimination-Biliary Tract <ul><li>Bilirubin metabolism </li></ul><ul><li>Breakdown of Hemoglobin </li></ul><ul><li>Bound to albumin for transport to liver (uncongugated) </li></ul><ul><li>In liver, conjugated with glucuronic acid </li></ul><ul><li>Conjugated bilirubin is soluable </li></ul>
  61. 62. Physiology of Elimination-Pancreas <ul><li>Exocrine and endocrine functions </li></ul><ul><li>Exocrine-digestion-pancreatic enzymes </li></ul><ul><li>Endocrine </li></ul><ul><ul><li>Islets of Langerhans </li></ul></ul><ul><ul><li>Beta cells-insulin </li></ul></ul><ul><ul><li>Alpha cells-glucagon </li></ul></ul><ul><ul><li>Delta-somatostatin </li></ul></ul><ul><ul><li>F cells-pancreatic polypeptides </li></ul></ul>
  62. 63. GI System and Aging <ul><li>Periodontal disease-loss of teeth </li></ul><ul><li>Taste buds, smell, salivary secretions decrease </li></ul><ul><li>Delayed gastric emptying </li></ul><ul><li>Motility of GI tract diminishes </li></ul><ul><li>Decrease in HCL secretion </li></ul><ul><li>Reduction in secretion of acid and intrinsic factor </li></ul><ul><li>Liver size decreases </li></ul>
  63. 64. GI System-Factors that Influence Function <ul><li>Stress/anxiety </li></ul><ul><li>Dietary intake </li></ul><ul><li>Ingestion of ETOH/caffeine </li></ul><ul><li>Cigarette smoking </li></ul><ul><li>Fatigue </li></ul><ul><li>Organic diseases </li></ul><ul><li>Others? </li></ul>
  64. 65. Chapter 21, part A Digestion
  65. 66. About this Chapter <ul><li>Overview of the digestive system & how it is organized </li></ul><ul><li>How products are moved and the role of digestive secretions </li></ul><ul><li>How and where food is broken down and absorbed </li></ul><ul><li>How digestive wastes are concentrated and eliminated </li></ul><ul><li>How digestion is regulated in the gastrointestinal (GI) tract </li></ul>
  66. 67. Processes of the Digestive System: Overview <ul><li>Ingestion </li></ul><ul><li>Digestion: enzymatic </li></ul><ul><li>Motility </li></ul><ul><li>Secretion </li></ul><ul><li>Absorption </li></ul><ul><li>Elimination </li></ul><ul><li>(Self protection) </li></ul>Figure 21-1: Processes of the digestive system
  67. 68. Digestive Anatomy: Overview <ul><li>Oral cavity </li></ul><ul><li>Salivary glands </li></ul><ul><li>Esophagus </li></ul><ul><li>Stomach </li></ul><ul><ul><li>Fundus </li></ul></ul><ul><ul><li>Body </li></ul></ul><ul><ul><li>(rugae) </li></ul></ul><ul><ul><li>Antrum </li></ul></ul><ul><ul><li>pyloris </li></ul></ul>
  68. 69. Digestive Anatomy: Overview Figure 21-2a: ANATOMY SUMMARY: The Digestive System
  69. 70. More Digestive Anatomy <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>Pancreas </li></ul><ul><li>Liver </li></ul><ul><li>Large intestine </li></ul><ul><ul><li>Colon </li></ul></ul><ul><ul><li>Rectum </li></ul></ul><ul><li>Anus </li></ul>
  70. 71. Digestive Anatomy: Histological Overview <ul><li>Stomach wall </li></ul><ul><ul><li>Mucosa </li></ul></ul><ul><ul><li>Gastric glands </li></ul></ul><ul><ul><li>Muscularis mucosa </li></ul></ul><ul><ul><li>Submucosa </li></ul></ul><ul><ul><li>Muscularis Externa </li></ul></ul><ul><ul><li>Serosa </li></ul></ul><ul><li>Small intestine wall </li></ul><ul><ul><li>Vili & microvili </li></ul></ul><ul><ul><li>Pyer's patches </li></ul></ul>
  71. 72. Digestive Anatomy: Histological Overview Figure 21-2c: ANATOMY SUMMARY: The Digestive System
  72. 73. Digestive Anatomy: Histological Overview Figure 21-2e: ANATOMY SUMMARY: The Digestive System
  73. 74. Motility: Smooth Muscle Contractions <ul><li>Tonic – support </li></ul><ul><li>Phasic – move products </li></ul><ul><ul><li>Parastalsis – moves  </li></ul></ul><ul><ul><li>Segmentation – mixes </li></ul></ul>Figure 21-4: Contractions in the GI tract
  74. 75. Digestive Secretions: (  7 L / Day From Tissues into Lumen) <ul><li>Salivary glands </li></ul><ul><li>Pancreas </li></ul><ul><li>Water </li></ul><ul><li>Enzymes </li></ul><ul><li>Mucus </li></ul><ul><li>Ions: H + , K + , Na + </li></ul><ul><li>HCO 3 - , Cl - </li></ul><ul><li>Mass Balance (H 2 O) </li></ul>Figure 21-5: Daily mass balance in the digestive system

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