1. Esophagus Muscular tube that extends from _________to the __________ and is located dorsal to the trachea. Function is to transport swallowed material to the stomach. No significant digestion takes place Enters stomach at an angle in __________ Controlled by cardiac sphincter As stomach fills, fold of stomach against esophagus closes lower end of esophagus Reduces risk for reflux In some species, closure is strong enough to prevent reflux or vomiting (horse, rabbit)

2. Megaesophagus Loss of muscle tone causing _________ of the esophagus Causes esophagus to relax Food accumulates in the esophagus instead of being transported to stomach. Animal ___________ undigested food. How do we treat? Feed liquid based diet Feed on an elevated surface Holding animal up and allowing gravity to pull food down to stomach. Can lead to aspiration pneumonia.

3. Monogastric (Simple) Stomach 1. _________- area immediately surrounding the opening from the esophagus into the stomach; sphincter and angle of esophageal entry helps to prevent reflux 2. _________- distensible blind pouch; expands as more food is swallowed; rich with glands 3. _________ – distensible middle section; rich with glands

4. Monogastric (Simple) Stomach 4._________ ________- distal portion that grinds up swallowed food and regulates the HCl produced in the body and fundus 5. _________- sphincter that regulates movement of digested stomach contents (chyme) from stomach to duodenum (first part of intestine). -Prevents backflow of duodenal contents into the stomach. _________ curvature- outer portion of C-shaped stomach _________ curvature- inner portion of C-shaped stomach

5. Gastric Glands FUNDUS & BODY: Both areas are rich with glands containing the following cells: __________ cells Produce hydrochloric acid (HCl) __________ cells Produce pepsinogen, an enzyme precursor to pepsin __________ cells Produce a protective mucus PYLORIC ANTRUM ____ cells Endocrine cells that secrete the hormone gastrin into the blood when food is present Gastrin stimulates the parietal cells to release HCl __________ cells

6. Gastric Motility Peristalsis continues in stomach and small intestines. Longitudinal muscles send peristaltic waves from the cardia to the antrum. Circular muscles encircle the antrum, allowing it to grind food. Fundus and Body relax with swallowing, allowing stomach to distend and fill with food. Body of stomach also contracts to help mix food within the stomach. Pyloric Antrum increases contractions in response to swallowing of food. Stimulates mixing, grinding, and propulsive contractions that move food toward pylorus Empty Full

7. Gastric Motility Pylorus Concentration of circular muscle fibers Maintains constant tone of sphincter Chyme is forced by contractions into antrum of stomach. Remains partially open so contents can move from stomach to duodenum. Anything that causes distension of the small intestines or increased acidity of duodenum will inhibit stomach contractions and delay gastric emptying. ______________ reflex- prevents stomach from sending its’ contents into the duodenum before the intestines are ready. Empty Full

8. Gastric Motility Stomach contains mucosal layer, submucosa, muscular layer (longitudinal and circular muscle fibers), and outer serosal layer Smooth muscle in stomach wall responds to actions of the Autonomic Nervous System. _________________ stimulation causes fundus to relax and increases contractions in antrum _________________ stimulation (fight or flight) can decrease motility → gastric atony

9. Gastric Secretions ______________ Hormone produced by G cells in the pyloric antrum. Helps to increase HCl production. Inhibits muscle activity of fundus. Causes relaxation and greater filling of the stomach. _____________ acid Produced by parietal cells in body and fundus. Produce hydrogen and chloride separately which combine in stomach. Accounts for stomach’s low pH When enough acid is produced, then gastrin release is inhibited. _____________- precursor to pepsin which breaks down proteins to chains of amino acids. Peptides (chains of amino acids) stimulate release of gastrin, which increases hydrochloric acid production and pepsinogen release. Pepsin is inactivated from pH change from stomach to intestine.

10. Gastric Secretions ____________ Hormone released by intestines Can inhibit peristalsis which slows gastric emptying. _______________ (CCK) Nutrients high in fat or protein stimulate release of this hormone. Decreases contraction of antrum, body and fundus. _____________ factor- protein that combines with vitamin B12 that aids in absorption of this vitamin.

11. Gastric Secretions ____________ Produced by gastric glands Complex of substances _______- produced by goblet cells Main constituent of mucus ____________- 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 Must be secreted continuously

12. Prostaglandins Small molecular structures released by the body that have a wide variety of effects. Involved in ______________. Some are beneficial to body. PGE & PGI Reduce hydrochloric 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.

13. Gastric Ulcers Deep erosions of the stomach’s epithelium Rugae- long folds in the stomach.

14. Ruminants and Complex Stomachs Only have one true stomach (abomasum), and 3 forestomachs (reticulum, rumen, and omasum). RUMINATION: ____________ food ____________ it _______ it some more ____________it again

15. Reticulum Smallest and most cranial compartment. _____________ arrangement to increase absorption. Separated from rumen by _______________fold; muscle wall is continuous with the rumen Rumen and Reticulum work together and produce Reticulorumen contractions. ___________ disease is associated with the reticulum.

16. Rumen Contains billions of ____________ _____________ takes place here Muscular sacs separated by pillars (long, muscular folds of rumen wall). Sacs can close off to allow more mixing to take place Reticuloruminal contractions allow: Regurgitation of partially-digested plant food (cud) to take place Eructation-Expulsion of built up carbon dioxide or methane gas If build up continues, may cause _________.

17. Rumen Continued Rumen motility is controlled by: _____ (ideal is 5.8-6.4) Presence of _________ _______ _______ (VFAs) Cellulose  Glucose  absorbed by microbes  VFA (absorbed)  Glucose (liver) Excess VFAs decrease rumen motility ______________ nervous system ___________ of foodstuffs ___________ receptors

18. Fermentative Digestion Dependent on billions of microbes (bacteria/protozoa) in rumen Rumen microbes contain enzymes: (monogastric animals produce necessary enzymes) Cellulase enzymes turn cellulose into simple carbohydrates/sugars (Simple stomach animals cannot digest cellulose) Glucose not immediately available to ruminant Absorbed by microbes and released as VFA ’ s VFA ’ s absorbed into blood and converted to glucose, fat, milk fat Proteases (from microbes) break down protein into aa ’ s/peptides Incorporated into microbes; eventually → bloodstream Converted to ammonia (NH 3 + ) and VFA ’ s → bloodstream Ammonia released is utilized by other microbes to create their own amino acids and proteins

19. Omasum When reticulorumen contractions occur, they move ingesta to omasum. Muscular with interior full of parallel, longitudinal muscular folds. Breaks down food particles and carry them to the abomasum. ________ VFA’s (that weren’t already absorbed in rumen) and water from ingesta Removes _______________ (to preserve the pH of the abomasum). Abomasum “_______ __________”; functions very similar to that of mongastric stomach. Only ______________ part of the stomach. Contains enzymes called __________ that break down microbes “flushed out” from the rumen to be used as protein source

20. Young Ruminant Digestive Tract Newborn’s stomach functions mainly as a monogastric digestive system. ______________ is the largest chamber in a newborn Rumen and reticulum are small and non-functional at birth (minimal _________). Development of rumen and reticulum is dependent on rate of diet change to grain. Milk in rumen can disrupt fermentation process so is carried directly to omasum. ____________ groove (_______________ groove)- allows liquids to be carried from esophagus directly to omasum, bypassing rumen and reticulum. As animal ages, groove disappears.

21. Small Intestines Where majority of nutrients are __________ into the bloodstream. Same anatomy for monogastrics and ruminants Divided into: ______________ Short, first segment that leaves stomach. ______________ Longest portion, makes up majority of small intestines. ______________ Short section that enters the colon (large intestine). Separated from colon by ileocecal sphincter- muscle that regulates movement of materials from small intestine into colon or the cecum (blind pouch of the large intestine).