chapter 17 – part 4
DESCRIPTION
Chapter 17 – Part 4. Watch an overview of the intestines and abdominal cavity. This video is graphic as it uses a cadaver. https :// www.youtube.com/watch?v=EJt4YDPLpzE&feature=related. Intestines. a "curtain-like" membrane that covers the intestines, stores fat and lays like a drape. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 17 – Part 4Intestines
Watch an overview of the intestines and abdominal cavity. This video is graphic as it uses a cadaver. https://www.youtube.com/watch?v=EJt4YDPLpzE&feature=related
Coverings: 1. Greater Omentum
a "curtain-like" membrane that covers the intestines, stores fat and lays like a drape
Stores fat for
quick use by liver
2. Mesentery• suspends portions of the small intestine from the posterior abdominal wall
Small Intestine – 3 parts start at the pyloric sphincter
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…
The Duodenum
• 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 longThe inner surface on the intestine is foldedEach 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 SummaryEnzyme Substrate Product Where it is
producedWhere it acts
Amylase
Pancreas Duodenum
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 AppendixColon (4 parts) Cecum Ascending Transverse Descending Sigmoid
Rectum Anus
Function of Large IntestineSecretes 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!
1. esophagus2. liver3. stomach4. pyloric sphincter5. duodenum6. pancreas7. jejunum8. ileum9. cecum10. appendix11. ascending colon12. descending colon13. sigmoid colong14. anus
Practice makes perfect. Click to access all the answers.
Microflora of the Gut
IBS - Irritable Bowel Syndrome – normal structure of bowel
Crohn’s Disease - autoimmune
Appendicitis
Herniaintestines 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