1. “We must have pie. Stress cannot exist in the presence of a pie.” David Mamet

2. Chapter 11

3.  Takes complex food and breaks them down into simple nutrient molecules through process of digestion.  After digestion takes place, nutrient molecules are absorbed into the bloodstream for use by the body’s cells.  Consists of a tube that runs from the mouth to the anus and accessory digestive organs that aid in the process of digestion and absorption. ◦ Known as digestive tract, Gastrointestinal (GI) tract, the alimentary canal, gastroenteric tract, or gut.

4.  The lumen is the opening in the middle of the intestinal tract or any hollow organ.  Anything in the lumen is considered outside the body. ◦ What must occur for things to enter the body?

5.  The requirements for digestion and absorption of foodstuffs vary considerably depending on the diet of the animal.  Each type of animal has different mechanisms to handle digestion and absorption. ◦ Herbivores  Plant eating animals ◦ Carnivores  Meat eating animals ◦ Omnivores  Animals that eat both plants and meat.

6.  Monogastric ◦ Animals that have simple, single stomachs.  Complex Stomachs ◦ Animals that have fermentation and mixing compartments in addition to the stomach.( Ex: ruminants)

7. 1. Prehension (grasping) of food with the lips or teeth 2. Mastication - mechanical grinding and breaking down of food (chewing) 3. Chemical digestion of food 4. Absorption of nutrients and water 5. Elimination of wastes  If any function fails, malnutrition may result. ◦ Usually failure is followed by clinical signs.  Examples of clinical signs?

8.  Gastro- refers to the stomach.  Entero- refers to the intestine.

9.  Made of multiple layers.  The mucosa-the lining layer and consists of the lining epithelium and some loose connective tissue  The submucosa-beneath the mucosa and contains glands and dense connective tissue.  The thick muscle layer is external to the submucosa. ◦ What type of muscle is this?  The serosa- is the outermost layer that consists of a thin, tough layer of connective tissue.

11.  Mesentery - Sheets of connective tissue ◦ Suspends digestive tube from dorsal body wall ◦ Contains blood vessels, lymph vessels, and nerves that supply GI tract

12.  2 types of epithelium are found in the GI tract: ◦ Stratified Squamous  Thick and tough.  Lines mouth, pharynx, esophagus, and anus. ◦ Simple Columnar  Change form stratified squamous occurs where esophagus enters stomach.  Allows for better absorption of nutrients.

13. SIMPLE COLUMNAR EPITHELIUM W/GOBLET CELLS AND MICROVILLI STRATIFIED SQUAMOUS EPITHELIUM

14.  2 types ◦ Skeletal Muscle  Under voluntary control  Mouth, pharynx, cranial esophagus, external anal sphincter.  Allows process of chewing, mixing saliva with food, and swallowing to be conscious acts.  Controls defecation. ◦ Smooth Muscle  Present in remainder portion of digestive tract.  Arranged in circular and longitudinal layers.  Circular Layer- narrows segment of tube.  Longitudinal Layer- shortens segment of tube.

16.  Food is moved and mixed by two types of muscle contractions. ◦ Peristaltic contractions  Move contents along digestive tract.  Circular muscle contractions that move food along in waves.  Propels food ahead of contractions.

17. http://www.youtube.com/w atch?v=h0E9ITyRlh0

18. ◦ Segmental contractions  Cause back and forth mixing movements of the digestive tract contents.  Consist of periodic, circular muscle contractions that occur in different adjacent sites.  Aid in digestion and absorption by mixing the digestive tract contents and slowing their movement through the tract.

19.  Also called the buccal cavity.  Where food is initially taken in and where digestion actually begins.  Structures include: ◦ Lips  Prehensile organ  Labia- term for referring to the lips. ◦ Tongue ◦ Teeth ◦ Salivary glands  Produce saliva, which performs digestive and lubrication functions.  Also involved in evaporative cooling. ◦ Hard palate ◦ Soft palate ◦ Oropharynx

20.  Most animals have 3 matching pairs of glands. ◦ Parotid salivary glands  Located just ventral to ear canals ◦ Mandibular salivary glands  Located ventral to parotid glands at the caudal angle of the mandible ◦ Sublingual salivary glands  Located medial to the shafts of the mandible just under the base of the tongue.  All have ducts that carry saliva to oral cavity.  Salivary glands are controlled by autonomic nervous system ◦ What happens during “fight or flight”?

21. Parotid salivary glands Mandibular salivary glands Sublingual salivary glands Buccal salivary glands

22.  Responsible for breaking down food into smaller pieces by process of mastication.  Increases surface area of the food that is exposed to digestive processes.  Maxilla contains upper arcade  Mandible contains lower arcade.

24.  Lingual (tongue)- inner surface of lower arcade  Palatal (hard palate)- inner surface of upper arcade  Labial (lips)- outer surface of upper/lower arcades (rostral)  Buccal (cheek) - outer surface of teeth (caudal)  Occlusal – surface that grinds with other teeth

25.  Carnivore teeth - pointed on occlusal surface; slightly curved toward back of mouth ◦ Good for holding prey, tearing, cutting, shredding  Herbivore teeth - flat occlusal surfaces ◦ Good for grinding plant and grain material

28.  Incisors ◦ Grasping teeth ◦ Most rostral teeth of upper and lower arcade  Canines ◦ Tearing teeth ◦ Located at corners of incisors ◦ Longer than other teeth ◦ Pointed at tip  Premolars ◦ Cutting teeth ◦ Rostral cheek teeth ◦ Sharp points and surfaces in carnivores  Molars ◦ Grinding teeth ◦ Caudal cheek teeth ◦ Larger, flatter occlusal surfaces ◦ Used for grinding

30.  Typical number of each type of tooth found in upper/lower arcades  Tooth type designated by the following letters: ◦ I=incisor ◦ C=canine ◦ P= premolar ◦ M=molar  Upper case: adult teeth  Lower case: deciduous teeth  Ruminants have no upper incisors or canine teeth. Instead have a dental pad- a flat, connective tissue structure of the maxilla opposite the lower incisors and canine teeth.

31.  Species Dental FormulaTotal Canine - puppy i3/3 c1/1 p3/3 28  Canine - adultI3/3 C1/1 P4/4 M2/3 42  Feline - kitteni3/3 c1/1 p3/2 26  Feline - adultI3/3 C1/1 P3/2 M1/1 30  Equine - adultI3/3 C1/1 P3-4/3 M3/3 40 or 42  Porcine - adultI3/3 C1/1 P4/4 M3/3 44  Bovine - adultI0/3 C0/1 P3/3 M3/3 32

34.  The fourth premolar is also referred to as the carnassial tooth. ◦ If this tooth abscesses may cause drainage through the skin under the eye. ◦ Because of root system and length of roots, removal is hard work.

36.  Living structures.  Have nerve, blood vessel and lymph supply.  Are susceptible to damage and pain.  Consist of: ◦ Apex ◦ Pulp ◦ Dentin ◦ Cementum ◦ Enamel ◦ Gingiva

37.  Apex ◦ the pointed part at the tip of the root ◦ Where blood and nerve supply enter the tooth  Pulp ◦ The center of the tooth  Dentin ◦ Surrounds the tooth pulp. ◦ More dense than bone but less dense than enamel.  Cementum ◦ Hard connective tissue that helps to fasten tooth in bony socket.  Enamel ◦ Hardest, toughest tissue in body. ◦ Outer cover of crown of tooth  Gingiva ◦ Epithelial tissue that forms the gums around the teeth

38.  The scaling away of tartar from the teeth.  Horses get teeth “floated”-this reduces points on buccal edge of teeth.

39.  Prehension of food  Initiate mastication ◦ Also referred to as mechanical digestion  Initiate chemical digestion ◦ Saliva has enzymes that aid in breakdown of food.  Prepare food for swallow ing.

40.  Proteins that promote the chemical reactions that split complex food molecules up into simpler compounds.  Secreted in the digestive system to break down different components of food.  Two common Digestive enzymes: ◦ Amylase  Found in saliva of omnivores but absent in carnivores  Breaks down amylose- a sugar component of starch. ◦ Lipase  Digests lipids  Found in saliva of young animals while nursing or on high milk diet.

41.  Cattle use sodium bicarbonate and phosphate buffers in saliva to neutralize acids that form in rumen.  Cattle can produce 25 to 50 gallons of saliva a day.

42.  Tube that extends from pharynx to the stomach.  Function is to take swallowed material to the stomach.  No digestion takes place here, it serves only for transport.  Enters the cardia of the stomach.  The cardiac sphincter surrounds the cardia.  Esophagus enters stomach at an angle. ◦ As the stomach fills with food, the folds in the stomach can close off against esophagus decreasing chance of reflux.

43.  Divided into five different areas. ◦ 1. Cardia ◦ 2. Fundus ◦ 3. Body ◦ 4. Pyloric antrum ◦ 5. Pylorus

44.  Cardia ◦ Where esophagus enters stomach. ◦ Helps reduce reflux  Fundus & Body ◦ Forms a pouch that can distend as more food is swallowed ◦ Rich with glands  Pyloric Antrum ◦ Distal part of the stomach that grinds food. ◦ Regulates hydrochloric acid  Pylorus ◦ Sphincter that regulates movement ofdigested stomach contents (Chyme) from stomach to duodenum (first part of intestine). ◦ Prevents backflow of duodenal contents into the stomach.

45.  Contain 3 key cells: ◦ Parietal cells (oxyntic cells)  Produce hydrochloric acid (HCl) ◦ Chief cells  Produce pepsinogen, precursor to pepsin ◦ Mucous cells  Produce mucus that is protective in nature.

46.  G- cells ◦ Endocrine cells ◦ Secretes gastrin hormone ◦ Presence of food stimulates G-cells to dump gastrin into the blood.

47.  C-shaped  Inside called lesser curvature of the stomach.  Outside called greater curvature of the stomach.  Rugae- long folds in the stomach.  Gastritis- inflammation of the stomach.  Gastric ulcers- erosions of epithelium of stomach.

49.  Each part of the stomach has different muscle functions.  Fundus and body relax with swallowing, allowing stomach to distend and fill with food.  Body of stomach contracts to help mix food within the stomach.  Pyloric Antrum increases contractions with the swallowing of food. ◦ Grinds food and propels food toward pylorus.

51.  Contains: ◦ Inner mucosal layer ◦ Submucosa ◦ Muscular layer  Circular  Longitudinal ◦ Outer serosal layer

52.  Pylorus ◦ Circular muscle fibers ◦ Maintains constant tone ◦ Chyme is forced through by contractions into antrum of stomach. ◦ Remains partially open so liquid contents can move from stomach to duodenum.

53.  Enterogastric reflex- prevents stomach from emptying until intestines are able to handle incoming contents.

54.  Vagus Nerve. Stimulates parasympathetic activity  Gastric atony- decreased muscle tone in the stomach.

55.  Gastrin ◦ Produced by which cells? ◦ Produced where? ◦ Helps to increase hydrochloric acid production. ◦ Inhibits muscle activity of fundus. ◦ Causes relaxation and greater filling of the stomach.

56.  Hydrochloric acid ◦ Produced by parietal cells. ◦ Produce hydrogen and chloride separately which combine in stomach. ◦ Accounts for stomach’s low pH ◦ When enough acid is produced, gastrin release is inhibited.

57.  Secretin ◦ Hormone released by intestines ◦ Can inhibit peristalsis which slows gastric emptying.  Cholecystokinin ◦ Nutrients high in fat or protein stimulate release of this hormone. ◦ Decreases contraction of antrum, body and fundus.

58.  Intrinsic factor- protein that combines with vitamin B12 and aids in absorption of this vitamin.  Pepsinogen- precursor to pepsin which breaks down proteins to chains of amino acids. ◦ Peptides (chains of amino acids) stimulates release of gastrin which increases hydrochloric acid production and pepsinogen release. ◦ Pepsin is inactivated by pH change from stomach to intestine.  Which area has a higher pH?  Which area has a lower pH?

59.  Mucus ◦ Produced by gastric glands ◦ Complex of many substances  Mucins- produced by goblet cells  Main constituent of mucus  Bicarbonate Ion- makes mucous coat more alkaline in nature  This helps to neutralize hydrochloric acid. ◦ Help to coat the stomach  pH of stomach is generally about 2-3

60.  3 receptors on “blood side” that regulate acid production ◦ Receptors are for:  Acetylcholine- neurotransmitter  Gastrin- increases hydrochloric acid production  Histamine- chemical associated with inflammatory response  Inhibiting these receptors decreases hydrocholoric acid production. ◦ This is how antacids work.

61.  Small molecular structures released by the body that have a wide variety of effects. ◦ Involved in inflammation. ◦ Some are beneficial to body.  PGE & PGI  Reduce hydrocholric acid production by inhibiting gastrin release from G cells.  Directly inhibit Parietal cells  Stimulate bicarbonate ion production  Enhance blood flow to stomach  Help stomach to repair quickly.