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)

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.

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

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

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

Gastric MotilityPeristalsis 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

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

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

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.

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.

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 stomachpH of stomach is generally about 2-3Must be secreted continuously

Prostaglandins

Small molecular structures released by the body that have a wide variety of effects. Involved in ______________. Some are beneficial to body.

PGE & PGIReduce hydrochloric acid production by inhibiting

gastrin release from G cells.Directly inhibit Parietal cellsStimulate bicarbonate ion productionEnhance blood flow to stomachHelp stomach to repair quickly.

Gastric Ulcers

Deep erosions of the stomach’s epithelium

Rugae- long folds in the stomach.

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

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.

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 gasIf build up continues, may cause

_________.

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

Fermentative Digestion

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

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.

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).