4 Digestive System


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4 Digestive System

  2. 3. DIGESTIVE SYSTEM <ul><li>Two main parts: </li></ul><ul><ul><li>Gastrointestinal (GI) tract - mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus. </li></ul></ul><ul><ul><li>Accessory digestive organs - teeth, tongue, gallbladder, salivary glands, liver, and pancreas. </li></ul></ul>
  3. 4. Digest. <ul><li>Abdomino-pelvic cavity is lined by 2 serous membranes = Peritoneal membrane(secretes a watery fluid) </li></ul><ul><ul><li>1. Parietal peritoneum - attached to body wall. </li></ul></ul><ul><ul><li>2. Visceral peritoneum - fused to surface of abdominal organs. </li></ul></ul>
  4. 5. GI – 4 Tunics <ul><li>A. Tunica Mucosa: innermost, 3 parts </li></ul><ul><ul><li>1. Epithelial Layer; Nonkeratinized stratified squamous (oral cavity to stomach) for protection; Simple Columnar (stomach to anus) </li></ul></ul><ul><ul><ul><li>a. Absorption </li></ul></ul></ul><ul><ul><ul><li>b. Secretion </li></ul></ul></ul><ul><ul><ul><ul><li>i. digestive enzymes </li></ul></ul></ul></ul><ul><ul><ul><ul><li>ii. mucus from goblet cells </li></ul></ul></ul></ul><ul><ul><li>2. Lamina propria - c.t. with lymphatic nodules (groups of WBC's) </li></ul></ul><ul><ul><li>3. Muscularis mucosae - thin layer of smooth muscle </li></ul></ul>
  5. 6. GI – 4 Tunics <ul><li>B. Tunica Submucosa - c.t. </li></ul><ul><ul><li>1. Highly vascular </li></ul></ul><ul><ul><li>2. May contain mucous glands </li></ul></ul><ul><ul><li>3. Nerve plexus </li></ul></ul>
  6. 7. GI – 4 Tunics <ul><li>C. Tunica Muscularis most common type is 2 layers of smooth muscle </li></ul><ul><ul><li>1. Inner - circular </li></ul></ul><ul><ul><li>2. Outer - longitudinal </li></ul></ul><ul><ul><li>Contract by  Peristalsis (waves of smooth muscle contraction, and are controlled by a nerve plexus) </li></ul></ul>
  7. 8. GI – 4 Tunics <ul><li>D. Tunica Serosa or Tunica Adventitia:  </li></ul><ul><ul><li>serosa = simple squamous epi + c.t.; </li></ul></ul><ul><ul><li>adventitia = just c.t. </li></ul></ul>
  8. 9. Mouth = Oral or Buccal cavity <ul><li>Functions </li></ul><ul><ul><li>1. Receives food </li></ul></ul><ul><ul><li>2. Initiates digestion </li></ul></ul><ul><ul><ul><li>a. Mastication </li></ul></ul></ul><ul><ul><ul><li>b. Saliva - has amylase (an enzyme) which breaks down carbohydrates (long chains of sugars into short chains) </li></ul></ul></ul><ul><ul><li>3. Initiates swallowing  </li></ul></ul>
  9. 10. Mouth -Histology <ul><li>1. Tunica Mucosa; inner epithelial lining = nonkeratinized stratified squamous </li></ul><ul><li>2. Tunica Submucosa: c.t. </li></ul><ul><li>3. Tunica Muscularis: facial muscles </li></ul><ul><li>4. Skin: outer, keratinized stratified squamous </li></ul>
  10. 11. Mouth -Tongue - has Papillae <ul><li>1. Filiform - most numerous, conical; for tactile sensation (touch, temp., texture, heat, cold, etc.) </li></ul><ul><li>2. Fungiform - larger, rounded, taste buds on top </li></ul><ul><li>3. Circumvallate - very large, 7-12, taste buds on sides </li></ul>
  11. 12. Palate <ul><li>1. Hard palate - bone (roof of oral cavity)  </li></ul><ul><li>2. Soft palate = muscular arches </li></ul><ul><ul><li>a. Uvula </li></ul></ul><ul><ul><li>b. Palatoglossal arch (ant.) </li></ul></ul><ul><ul><li>c. Palatopharyngeal arch (post.)   </li></ul></ul><ul><li>Between the two arches = palatine tonsils   </li></ul>
  12. 13. Mouth - Teeth <ul><li>Teeth </li></ul><ul><ul><li>Mastication </li></ul></ul>
  13. 14. Mouth –Salivary Glands <ul><li>Salivary glands: 3 pairs </li></ul><ul><ul><li>1. Parotid - largest, on masseter, secretes serous fluid, fluid enters mouth via parotid duct </li></ul></ul><ul><ul><li>2. Submandibular - secretes serous & mucous </li></ul></ul><ul><ul><li>3. Sublingual - secretes primarily mucus, in floor of mouth </li></ul></ul>
  14. 15. Pharynx - <ul><li>Common to resp. & digest. systems. Connects oral cavity to esophagus & nasal cavity to larynx. </li></ul><ul><li>Parts </li></ul><ul><ul><li>1. Nasopharynx - not part of Dig. Sys. </li></ul></ul><ul><ul><li>2. Oropharynx - air & food </li></ul></ul><ul><ul><li>3. Laryngopharynx - air and food </li></ul></ul>
  15. 16. Pharynx –Histo. <ul><li>1. Tunica Mucosa: contains nonkeratinized stratified squamous </li></ul><ul><li>2. Tunica Submucosa: c.t. </li></ul><ul><li>3. Tunica Muscularis; composed of 3 bands of skeletal muscle = constrictors </li></ul><ul><li>4. Tunica Adventitia: c.t. </li></ul>
  16. 17. Esophagus <ul><li>A. Connects pharynx to stomach </li></ul><ul><li>B. Passes through diaphragm at esophageal hiatus </li></ul><ul><li>C. Ends at stomach; its muscularis layer forms the Gastroesophageal (cardiac) sphincter. </li></ul>
  17. 18. Esophagus – histo. <ul><li>1. Mucosa - non-keratinized stratified squamous </li></ul><ul><li>2. Submucosa - contains mucous glands </li></ul><ul><li>3. Muscularis - 3 sections </li></ul><ul><ul><li>a. Upper 1/3 = skeletal </li></ul></ul><ul><ul><li>b. Middle 1/3 = sk. & smooth </li></ul></ul><ul><ul><li>c. Lower 1/3 = smooth </li></ul></ul><ul><li>4. Adventitia - c.t. </li></ul><ul><li>Function: voluntary & involuntary movement of food to stomach   </li></ul>
  18. 19. Stomach - General <ul><li>4 regions: cardiac, fundus, body, & pylorus. Ends at pyloric sphincter </li></ul><ul><li>Begins break-down of food </li></ul>
  19. 20. Stomach - histo <ul><li>1. Mucosa - has Gastric Pits which open up into the Gastric Glands.                 The Gastric Glands are composed primarily of; </li></ul><ul><ul><li>a. Simple columnar epi. </li></ul></ul><ul><ul><ul><li>i. Mucous neck cells - for protection </li></ul></ul></ul><ul><ul><ul><li>ii. Parietal cells - hydrochloric acid (HCl) </li></ul></ul></ul><ul><ul><ul><li>iii. Chief cells - pepsinogen (an inactive enzyme that is activated                          to Pepsin by hydrochloric acid, for protein digestion) </li></ul></ul></ul><ul><li>2. Submucosa - c.t. </li></ul><ul><li>3. Muscularis - 3 layers of smooth muscle; longitudinal, oblique, & circular </li></ul><ul><li>4. Serosa   </li></ul>
  20. 21. Small Intestine – Major Digest Organ <ul><li>Major digestive organ 8-18 ft long   </li></ul><ul><li>1. Duodenum: most chemical digestion occurs here because; </li></ul><ul><ul><li>Duodenal cells make enzymes to break down foodstuffs </li></ul></ul><ul><ul><li>It receives bile from gall bladder </li></ul></ul><ul><ul><li>It receives enzymes from the pancreas for the break down of foodstuffs </li></ul></ul><ul><li>2. Jejunum - most absorption occurs here </li></ul><ul><li>3. Ileum - very little absorption   </li></ul><ul><li>Digestion is completed in Small Intestine. The small intestine ends at the Ileocecal valve </li></ul>
  21. 22. Sm. Intestine - Histo <ul><li>1. Mucosa has finger-like folds = Villi </li></ul><ul><ul><li>a. Epithelium - Simple Columnar with microvilli (secretion & absorption) and Goblet cells (mucus). </li></ul></ul><ul><ul><li>b. Lamina propria - contains lacteals Between villi = intestinal glands </li></ul></ul><ul><li>2. Submucosa is in folds </li></ul><ul><li>3. Muscularis - 2 layers of smooth muscle; outer - long., inner - circ. </li></ul><ul><li>4. Serosa </li></ul>
  22. 23. Large Intestine – Larger Diameter <ul><li>Regions: Cecum, Apendix, Colon, Rectum, Anal Canal </li></ul><ul><li>Function Re-absorption of digestive fluids </li></ul>