Chapter 17 – Part 4
Intestines
Watch an overview of the intestines and
abdominal cavity. This video is graphic as it
uses a cadaver.
https://www.youtube.com/watch?v=EJt4YDPL
pzE&feature=related
Coverings:
1. Greater Omentum
a "curtain-like" membrane that covers the
intestines, stores fat and lays like a drape
2. Mesentery
• suspends portions of the small
intestine from the posterior
abdominal wall
Small Intestine – 3 parts start at the
pyloric sphincter
The Duodenum
first part of the small intestine.
 Food, still mixed with gastric juice is
squirted into it from the stomach.
 The food is now a semi liquid, highly
acidic mush.
 It needs to be neutralized and
digestion needs to be continued…

• Small, soluble food molecules are
absorbed through the wall of the small
intestine
• To absorb food molecules efficiently the
small intestine has three main
adaptations…….
1. Large Surface Area
The small intestine is very long
-6m long
The inner surface on the intestine is folded
Each cell is covered with microvilli
increasing the surface area in contact
with digested food will increase absorption
(up to 60 times more absorption)
Wall of small intestine
‘finger-like folds
in the surface of
the small
intestine’
(Singular – villus)
Intestinal villi - increase surface area to
absorb nutrients, connect to vessels
2. Thin Wall
• Each villus has an
extremely thin wall
-only one cell thick
-rapid absorption
• electrolytes and water
• through diffusion,
osmosis, and active
transport
• absorbed into blood
3. Good Blood Supply
• Each villus is supplied with blood
vessels to receive the absorbed
foods
-glucose/amino
acids/vitamins/minerals are
absorbed into blood capillaries
-products of fat digestion
absorbed into lacteal
• Homework – do this animation.
Make sure you digest a
number of different types of foods. Note how they are digested
differently.
http://kitses.com/animation/swfs/digestion.swf
Secretions of Small Intestine
• peptidase – breaks down peptides into amino acids
• sucrase, maltase, lactase – break down disaccharides
into monosaccharides
• lipase – breaks down fats into fatty acids and glycerol
• enterokinase – converts trypsinogen to trypsin
• somatostatin – hormone that inhibits acid secretion by
stomach
• cholecystokinin (cck) – hormone that inhibits gastric
glands, stimulates pancreas to release enzymes in
pancreatic juice, stimulates gallbladder to release bile
• secretin – stimulates pancreas to release bicarbonate
ions in pancreatic juice
Enzyme Summary
Enzyme
Substrate
Product
Where it is
produced
Where it acts
Pancreas
Duodenum
Amylase
Amino Acids
Fat
Small intestine
Movements of the small intestine
• mixing movements
• peristalsis – pushing movements
• segmentation – ringlike contractions
• overdistended wall triggers peristaltic rush resulting
in diarrhea
Large Intestine
Cecum
Appendix
Colon (4 parts)
Cecum
Ascending
Transverse
Descending
Sigmoid
Rectum
Anus
Function of Large Intestine
Secretes mucus, reabsorbs water and electrolytes, contains
bacteria to aid in digestion (intestinal flora)
Mass Movements (defecation) - removes undigested food
The main job is
WATER
REABSORPTION...
Large Intestinal Wall
Simple columnar epithelium
Egestion
Any indigestible food (e.g. fiber)
passes into the large intestine (colon).
 Water is absorbed back into the body.


Where has this water come from?
The food becomes a solid waste
called feces.
 Feces are stored in the rectum and
removed through the anus. This
removal is called EGESTION.

Movements
• slower
and less frequent than those of small
intestine
• mixing movements
• peristalsis
• mass movements usually follow meals
Everybody Poops
Feces
• water
• electrolytes
• mucus
• bacteria
• bile pigments altered by bacteria provide color
• smell produced by bacterial compounds
How to Make Fake Poop...
LABEL THIS!
Practice makes perfect. Click to
access all the answers.
1. esophagus
2. liver
3. stomach
4. pyloric sphincter
5. duodenum
6. pancreas
7. jejunum
8. ileum
9. cecum
10. appendix
11. ascending colon
12. descending colon
13. sigmoid colong
14. anus
Microflora of the Gut
IBS - Irritable Bowel Syndrome –
normal structure of bowel
Crohn’s Disease - autoimmune
Appendicitis
Hernia
intestines
poke through
abdominal
muscles
Celiac disease foods
containing gluten (protein),
immune system responds by
damaging or destroying villi
Without healthy villi, a person
becomes malnourished, no
matter how much food one
eats.
Colon Cancer
Colonoscopy is a screening technique to detect cancer.
See Katie Couric's Colonoscopy