Transcript Esophagus

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
 Peristalsis continues in stomach and
Gastric Motility
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
Empty
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
Full
 Pylorus
 Concentration of circular muscle fibers
 Maintains constant tone of sphincter
 Chyme is forced by contractions into
Gastric Motility
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.
Empty
Full
 ______________ reflex- prevents stomach
from sending its’ contents into the
duodenum before the intestines are ready.
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 stomach
 pH of stomach is generally about 2-3
 Must 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 & 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.
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 gas
 If 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
 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 (NH3+) and VFA’s → bloodstream
 Ammonia released is utilized by other microbes to create their own
amino acids and proteins
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.
 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).
Small Intestines