Esophagus

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

• _________- area immediately surrounding the
  opening from the esophagus into the stomach
  sphincter and angle of esophageal entry helps to
  prevent reflux
• _________- distensible blind pouch expands as
  more food is swallowed rich with glands
• _________ 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 stomachs 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 stomachs 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 VFAs
• VFAs absorbed into blood and converted to
  glucose, fat, milk fat
• Proteases (from microbes) break down protein into
  aas/peptides
• Incorporated into microbes eventually ?
  bloodstream
• Converted to ammonia (NH3) and VFAs ?
  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.
• ________ VFAs (that werent 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

• Newborns 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).