The Digestive System A Closer Look

Betcha didn’t know that… Your intestines are 7.5 metres long! A horse’s intestines are 27 metres long! Digestion from mouth to anus takes ~72 hrs! In your lifetime, your digestive system may handle about 50

tons o’ food! The average person eats about 1.4 kg of food per day! 1.5 litres of saliva are produced each day! An adult’s stomach can hold about 1.5 litres! Each day 11.5 litres of digested food, liquids and digestive

juices flow through the digestive system…but only 100mLs are lost in feces!

QOTD – Label Me!

Answers

1. Tongue

2. Esophagus

3. Stomach

4. Duodenum

5. Pancreas

6. Ileum

7. Large Intestine

8. Rectum

Purpose:

To enable the absorption of the nutrients needed for growth, maintenance and repair

Types of Digestion

As food travels down the alimentary canal it must be broken down into monomers so that our cells can use them.

They need to be small enough to pass through the villi and into the bloodstream.

Mechanical Digestion

Chewing, Mixing, Emulsifying

Done with the teeth Peristalsis: Muscular

contractions move the bolus (food ball) along the digestive tract.

Chemical Digestion

Performed by enzymes Uses the process of hydrolysis to break down

polymers into monomers.

Question:

HOW DO WE KEEP FROM DIGESTING OURSELVES??

Answer:

Line the entire system with mucus!!

Lined from the cardiac sphincter to the anus.

Where is there no mucus?

Esophagus…Acid reflux (heartburn)

Components of Digestion

Ingestion = the taking in of nutrients = enters by mouth

Digestion = the breakdown of complex organic molecules into

smaller components by physical & chemical means

Mechanical – done by teeth, and stomach

Chemical – done by the mouth, stomach, liver, gallbladder, pancreas, small & large intestine.

Break It Down Now!Enzymes

Carbohydrases break down ________ Peptidases break down… ________ Lipases break down… ________

Absorption

The taking up of digested molecules into cells Done by stomach, small intestine (villi), large

intestine

small intestine (villi)

Absorption

The Small Intestine is designed to have a large surface area.

The inner membrane is folded like a fan The entire surface is covered with villi (villus) Each villus is covered with microvilli Absorption involves diffusion and active

transport

Anatomy of a VillusMicrovilli

Capillary

Lacteal

Water

Minerals TO BLOOD

Water soluble vitamins (B, C)

Glucose

Amino AcidsGlycerol TO LYMPH

Fatty Acids

Fat soluble vitamins (A, D, E, K)

Proteins

Starches

Lipids

BEFORE DIGESTION…

TOO BIG!!

AFTER DIGESTION…

SMALL ENOUGH!!

Elimination The removal of waste from the body Done by large intestine, rectum and anus

Control Mechanisms

Regulation through feedback

Done by hormones (chemical messengers)

Thermostat Example:

-Too hot, shuts down

-Too cold, starts furnace

Digestion of Fats

When fats enter the duodenum, the hormone CCK (Cholecystokinia) is released which causes the gall bladder to release bile.

Fats are emulsified

Acidic Chyme

When acidic chyme enters the small intestine, the hormone secretin is released which causes the pancreas to release bicarbonate ions.

The acid is then neutralized!

Blood Glucose Levels

When glucose enters the blood stream, the pancreas releases Insulin.

Insulin stimulates the storage of glucose (as Glycogen, in the liver)

Blood Glucose Levels CONT

When blood glucose levels drop too low, the pancreas releases Glucagon.

Glucagon stimulates the release of glucose (from Liver) into the bloodstream

Blood Sugar Levels

Check out Page 270!

Digestive System Problems

1. Ulcer A sore wall of the

stomach (peptic) or duodenum (duodenal)

HCl creates a hole in the mucous lining…acid irritates muscles

Caused by bacteria that reduce amount of mucous.

Treated with antibiotics

Digestive System Problems

2. Cirrhosis of the Liver. Scar tissue in liver. Caused by excessive

alcohol consumption and/or hepatitis virus.

Results in jaundice (yellow skin), nausea, pain, fluid in abdomen

Treatment…stop drinking!, vitamins, transplant.

Read Page 273!

Digestive System Problems

3. Inflammatory Bowel Disease Crohn’s Disease and

Ulcerative colitis Inflammation of the lining of

small or large intestine. Treatment: Drugs,

supplements or… Resection and Colostomy A stoma is created, and a

pouch collects the waste.

Digestive System Problems

4. Constipation Too much water is

removed from feces Usually because waste

is moving too slowly…”bunged up!”

Treatment: Eat fibre! (cellulose), laxatives, suppositories.

Time to get Active!! Using all the members of the class,

create a representation of the journey of a peanut butter and banana sandwich through the digestive system from start to finish!

WE’RE DONE!!!