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Digestive System I: Organs and Structure  General functions  Organs of the Alimentary Canal Mouth and Teeth Swallowing Pharynx, Esophagus oPropulsion.

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Presentation on theme: "Digestive System I: Organs and Structure  General functions  Organs of the Alimentary Canal Mouth and Teeth Swallowing Pharynx, Esophagus oPropulsion."— Presentation transcript:

1 Digestive System I: Organs and Structure  General functions  Organs of the Alimentary Canal Mouth and Teeth Swallowing Pharynx, Esophagus oPropulsion Stomach Linings and Mesentaries Small Intestine Large Intestine

2 The Digestive System and Body Metabolism  Digestion Six essential activities 1.Ingestion 2.Propulsion 3.Mechanical digestion 4.Chemical digestion 5.Absorption 6.Defecation Figure 23.2 Food Ingestion Propulsion Esophagus Stomach Pharynx Mechanical digestion Chemical digestion Chewing (mouth) Churning (stomach) Segmentation (small intestine) Small intestine Large intestine Defecation Anus Feces Blood vessel Lymph vessel Absorption Swallowing (oropharynx) Peristalsis (esophagus, stomach, small intestine, large intestine) Mainly H 2 O

3 Organs of the Digestive System Organs of the Alimentary Canal  Mouth  Pharynx  Esophagus  Stomach  Small intestine  Large intestine  Anus Accessory Digestive Organs  Salivary glands  Teeth  Pancreas  Liver  Gall bladder

4 Digestive System I: Organs and Structure  General functions  Organs of the Alimentary Canal Mouth and Teeth Swallowing Pharynx, Esophagus oPropulsion Stomach Linings and Mesentaries Small Intestine Large Intestine

5 Mouth (Oral Cavity) Anatomy

6 Processes of the Mouth  Mechanical Processes Mastication (chewing) of food using temporal and masseter muscles and teeth Wetting masticated food with saliva Initiation of swallowing by the tongue  Chemical Processes Allowing for the sense of taste Digestion of some starch by salivary amylase in saliva

7 Teeth  The role is to masticate (chew) food  Humans have two sets of teeth Deciduous (baby or milk) teeth 20 teeth are fully formed by age two  Permanent teeth Replace deciduous teeth beginning between the ages of 6 to 12 A full set is 32 teeth, but some people do not have wisdom teeth  Classification of Teeth Incisors (clipping, nibbling) Canines (siezing) Premolars (grinding) Molars (grinding)

8 Regions of a Tooth  Crown – exposed part Outer enamel Dentin Pulp cavity  Neck Region in contact with the gum Connects crown to root  Root Periodontal membrane attached to the bone Root canal carrying blood vessels and nerves

9 Pharynx Anatomy and Function

10 Digestive System I: Organs and Structure  General functions  Organs of the Alimentary Canal Mouth and Teeth Swallowing Pharynx, Esophagus oPropulsion Stomach Linings and Mesentaries Small Intestine Large Intestine

11 Figure 23.13, step 1 Tongue Trachea Pharynx Epiglottis Glottis Bolus of food Upper esophageal sphincter is contracted. During the buccal phase, the tongue presses against the hard palate, forcing the food bolus into the oropharynx where the involuntary phase begins. 1 Deglutition

12 Figure 23.13, step 2 Epiglottis Esophagus Uvula Bolus The uvula and larynx rise to prevent food from entering respiratory passageways. The tongue blocks off the mouth. The upper esophageal sphincter relaxes, allowing food to enter the esophagus. 2 Deglutition

13 Figure 23.13, step 3 Bolus The constrictor muscles of the pharynx contract, forcing food into the esophagus inferiorly. The upper esophageal sphincter contracts (closes) after entry. 3 Deglutition

14 Digestive System I: Organs and Structure  General functions  Organs of the Alimentary Canal Mouth and Teeth Swallowing Pharynx, Esophagus oPropulsion Stomach Linings and Mesentaries Small Intestine Large Intestine

15 Esophagus  Runs from pharynx to stomach through the diaphragm  Conducts food by peristalsis (slow rhythmic squeezing)  Passageway for food only (respiratory system branches off after the pharynx)  Esophageal mucosa contains stratified squamous epithelium Changes to simple columnar at the stomach  Esophageal glands in submucosa secrete mucus to aid in bolus movement

16 Propulsion  Peristalsis – alternating waves of contraction  Segmentation – moving materials back and forth to aid in mixing Peristalsis Movie Online Peristalsis X-ray movie

17 Digestive System I: Organs and Structure  General functions  Organs of the Alimentary Canal Mouth and Teeth Swallowing Pharynx, Esophagus oPropulsion Stomach Linings and Mesentaries Small Intestine Large Intestine

18 Stomach Anatomy and Function Muscularis externa cardiac sphincter serosa rugae of mucosa lesser curvature greater curvature Functions of the Stomach  Acts as a storage tank for food  Site of initial food breakdown  Chemical breakdown of protein begins  Delivers chyme (processed food) to the small intestine cardiac region fundus region pylorus region body region

19 Propulsion in the Stomach  Food must first be well mixed  Rippling peristalsis occurs in the lower stomach  The pylorus meters out chyme into the small intestine (30 ml at a time)  The stomach empties in four to six hours Figure Stomach peristalsis interactive animation online

20 Specialized Mucosa of the Stomach  Simple columnar epithelium Mucous neck cells – produce a sticky alkaline mucus Gastric glands – secrete gastric juice Chief cells – produce protein-digesting enzymes (pepsinogens) Parietal cells – produce hydrochloric acid Endocrine cells – produce gastrin

21 Figure Stomach lumenChief cell Parietal cell Inter- stitial fluid Carbonic anhydrase Alkaline tide HCO 3 – Blood capillary CO 2 Cl – CO 2 + H 2 O H 2 CO 3 HCO 3 – - Cl – antiporter HCO 3 – H+H+ Cl – l K+K+ K+K+ H+H+ H + -K + ATPase HCI Chief Cells Utilize Blood CO 2 and Interstitial Cl to Produce HCl

22 Serous Membranes- Thin linings of organs and body wall Parietal serosae line internal body walls Visceral serosae cover internal organs  Mesenteries are double layers of peritoneum Routes for blood vessels, lymphatics, and nerves; holds organs in place and stores fat  Retroperitoneal organs lie posterior to the peritoneum (e.g. the liver); intraperitoneal (peritoneal) organs are surrounded by the peritoneum

23 Mesenteries of the Stomach Layers of peritoneum (serosa) attached to the stomach = mesentaries  Lesser omentum – attaches the liver to the lesser curvature  Greater omentum – attaches the greater curvature to the posterior body wall  Contains fat to insulate, cushion, and protect abdominal organs Lesser omentum Greater omentum

24 Digestive System I: Organs and Structure  General functions  Organs of the Alimentary Canal Mouth and Teeth Swallowing Pharynx, Esophagus oPropulsion Stomach Linings and Mesentaries Small Intestine Large Intestine

25 Small Intestine  The body’s major digestive organ  Site of nutrient absorption into the blood  Muscular tube extending form the pyloric sphincter to the ileocecal valve  Suspended from the posterior abdominal wall by the mesentery (omenta)  Regions of the Small Intestine Duodenum oAttached to the stomach oCurves around the head of the pancreas Jejunum oAttaches anteriorly to the duodenum Ileum oExtends from jejunum to large intestine

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27 Four Tunics of the Alimentary Canal

28 Absorption in the Small Intestine  Absorptive Structures Absorptive cells Blood capillaries Lacteals (specialized lymphatic capillaries)  Folds in the Small Intestine Called circular folds or plicae circulares Deep folds of the mucosa and submucosa Do not disappear when filled with food  Peyer’s patches in submucosa (collections of lymphatic tissue) Intestinal crypt epithelium Secretory cells that produce intestinal juice Cells that make antimicrobial chemicals Stem cells

29 Digestive System I: Organs and Structure  General functions  Organs of the Alimentary Canal Mouth and Teeth Swallowing Pharynx, Esophagus oPropulsion Stomach Linings and Mesentaries Small Intestine Large Intestine

30 Functions of the Large Intestine Structures  Cecum – saclike first part of the large intestine  Appendix Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis) Hangs from the cecum  Colon Ascending Transverse Descending S-shaped sigmoidal  Rectum  Anus – external body opening Functions  Absorption of water  Elimination of indigestible food from the body as feces  Does not participate in digestion of food  Goblet cells produce mucus to act as a lubricant

31 Figure 23.29a Left colic (splenic) flexure Transverse mesocolon Epiploic appendages Descending colon Teniae coli Sigmoid colon Cut edge of mesentery External anal sphincter Rectum Anal canal (a) Right colic (hepatic) flexure Transverse colon Superior mesenteric artery Haustrum Ascending colon IIeum IIeocecal valve Vermiform appendix Cecum

32 Modifications to the Muscularis Externa in the Large Intestine  Longitudinal smooth muscle is reduced to three bands (teniae coli); circular muscles still present  Muscle bands have some degree of tone  Walls are formed into pocketlike sacs called haustra

33 Digestive System I: Organs and Structure  General functions  Organs of the Alimentary Canal Mouth and Teeth Swallowing Pharynx, Esophagus oPropulsion Stomach Linings and Mesentaries Small Intestine Large Intestine


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