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

http://www.udel.edu/Biology/Wags/wagart/anaglyphpage/villi.gif

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