Download Stomach

Stomach
Objectives
At the end of the lesson, the student will be able to…
1. Name the parts of the stomach, including the
layers, regions, and sphincters
2. Identify the functions of the different cells in the
stomach and what they secrete
3. Identify how the stomach digests food and
contributes to the overall digestive system
4. Name the functions of the sphincters of the
stomach
5. Define the greater and lesser omentum and what
role they play in aiding the stomach
6. Trace the path of food from the stomach to the
small intestine
Stomach
• C-shaped, on the left side
• Hidden by liver and
diaphragm
• Multiple regions
o Cardiac
o Fundus
o Body
o Pyloric antrum
o Pylorus
• 3 muscular layers to help mix
and breakdown food
• Longitudinal layer, circular
layer, oblique layer
Stomach
Stomach
• Expands and collapses based on food content
• When collapsed, the mucosa forms folds called,
rugae
What holds it in place??
• Lesser omentum-
o Connects liver to “inside” curve of stomach
• Greater omentum-
o Connects large curve of stomach to the
intestines
Both are…
• Extensions of visceral peritoneum
• Riddled with fat (insulate & protect internal
organs)
o many lymph nodes
Stomach
• Food enters the stomach from the esophagus
through the cardiac sphincter
• Chemical breakdown of proteins starts in the
stomach
• The mucosa is composed entirely of mucous cells
that produce a protective layer of bicarbonate-rich
alkaline mucus
• Smooth lining is dotted with gastric pits that go to
gastric glands
Secretions in the Stomach
•
Gastric glands- secrete gastric
juice
•
Chief cells- produce protein
digestion enzymes- pepsinogen
(before activated, pepsin when
activated)
•
Parietal cells- produce HCl and
intrinsic factor
•
Mucous neck cells- thin acidic
mucous
•
Enteroendocrine cells- produce
hormones such as gastrin
•
Why do we need all of these????
Stomach to Small
Intestines
• Most digestion occurs in pyloric region
of stomach
• Chyme- processed food
• Chyme enters the small intestine
through the pyloric sphincter
• Chyme enters the stomach
slowly…one squirt at a time until the
stomach is empty
Stomach Video 
• http://www.youtube.com/watch?v=URHBBE3RKEs
Stomach Illnesses
• Heartburn- backflow of chyme into the esophagus
• Acid Reflux- chronic heartburn
• Gastric ulcers- stomach lining is eroded by gastric
juices faster than it can regenerate
• Caused by bacteria
Helicobactor pylori- acid tolerant bacteria
• How???
Peptic Ulcers
• Bacteria destroys the
mucous lining
• NOT caused by stress &
spicy foods
• Symptoms:
o
o
o
o
Pain navel-chest
Blood in vomit or stool
Temp. relief w/ antacids
Pain comes & goes
Review Activity
• Think-pair-share 
• Get into pairs
• Trace the path that food takes from the mouth to
the small intestine
Objectives
1. Trace the path of food from the stomach to the small
intestine
2. Identify the parts of the small intestine- duodenum,
jejunum, and ileum
3. Identify the functions of the pancreatic duct and bile
ducts in the small intestine and how they contribute to
digestion
4. Discuss the function of the microvilli, villi, circular folds,
and lacteal in digestion
5. Identify the parts of the large intestine, including the
cecum, appendix, colon (ascending, transverse,
descending, sigmoid, anus), rectum, sphincters, and
anal canal
6. Identify the pancreas, liver, and gallbladder, and their
function in digestion
7. Understand defecation reflex
Small Intestine
• Longest part of the
alimentary canal
• Named the “small”
intestine because of its
small diameter- 2.5 cm
across
• Major organ for chemical
digestion
• Goes from the pyloric
sphincter to the large
intestine
Let’s Talk about pizza.
• What?
• Where?
• How?
• What happens next?
Small Intestine and
Accessory Organs
• Duodenum- first part of
the small intestine~5%
• Jejunum- 40%
• Ileum- 60% (both
absorb nutrients
• Chyme is mixed with
enzymes and
transformed by:
• Liver- makes bile
• Pancreas- glandsecretes “juice” from a
duct
• Gallbladder- stores bile
The Bile Path
• Bile is produced by the
liver
• Stored in the
gallbladder
• Contains salts that
emulsify fats
• Prevents fat droplets
from re-forming large
globules
• Causes fats to be more
accessible to lipase
Absorption of Nutrients
• Villi- fingerlike
projections (each has
microvilli on it)
• Microvilli- tiny
projections of mucosa
cells; make the brush
border
• Lacteal- lymphatic
vessel in each villus
• Increase surface area,
increase rate of
absorption
Large Intestine
• Main part is the colon
• Functions:
•
•
•
•
•
Drys out indigestible food: ex: cellulose
Elminates waste as feces
Produce alkaline mucus
Absorb nutrients produced by bacteria in colon
No villi
Large Intestine
Troubles with the Large
Intestine
• Diarrhea- lining of the colon becomes irritated by a
viral or bacterial infection, resulting in less
absorption of water
• Constipation- feces is moved along the colon too
slowly, too much water is absorbed and feces
becomes hard.
• Celiac’s disease- protein, gluten, triggers an
immune response that leads to swelling and lack of
nutrient absorption
• Crohn’s disease- inappropriate immune response
that leads to chronic inflammation
Rectum
• Stores feces until they can be eliminated
• Contractions of the colon and rectum create urge
to defecate
• Anus is controlled by 2 sphincters- one voluntary,
one involuntary
• Voluntary sphincter relaxes, feces is expelled
through the anus
Digestive Enzyme Video
• http://www.youtube.com/watch?v=vTQybDgweiE
Review 
• Trace the path of food from the mouth to the anus.
Use the 4 functions of the digestive system in your
answer, specifying where each happen.
•
•
•
•
Ingestion
Digestion
Absorption
Elimination