Digestion: part 2

Last time...Chewing!

Swallowing!Tummy churning!

Exiting the stomach!Our friend the pancreas!

Liver The liver produces bile which gets stored in the

gall bladder. This bile gets sent to the small intestine through

the bile duct The hormone CCK is produces in the wall of

the duodenum and triggers bile release The bile salts in bile break down fat into fat

droplets (this is called emulsification) After fat has been emulsified, it can be digested

We will return to our friend the liver in a moment...

Meanwhile...in the small intestine..

Intestinal glands release enzymes to complete digestion

Peptidases break peptides into amino acids Maltase breaks maltose into glucose Nuclease breaks nucleic acids into nucleotides This all happens with water!!

Once all nutrients are broken down...

The amino acids, glucose, fatty acids and glycerol get absorbed into the blood stream.

The small intestine is specialized for this function because it is long and convoluted and has many villi (and microvilli on the villi) which all works to creat a HUGE surface area for absorption

Absorption is an active process that requires ATP

Glucose and amino acids enter the blood stream (Y), glycerol and fatty acids enter the lacteals(X)

Now back to the liver......

All vessels form the villi end up at the hepatic portal vein at the liver

Any excess glucose present is removed by the liver and stored as glycogen (this process releases water)

Between meals (fasting) glycogen is broken down to glucose

When glucose stores run short, the liver will convert amino acids into glucose (this is called gluconeogenesis

Only occurs in periods of starvation A by product of this process is urea

Liver functions

Destroys old RBCs, converts hemoglobin to bilirbin and biliverdin

Produces bile Stores glucose as glycogen Produces urea Makes blood proteins Detoxifies blood

Large intestine There are 3 parts to the whole colon It is 1.5 m in length The appendix is found at the junction of the

small intestine and large intestine Large intestine has a large role in water

reabsorption

Water reabsorption Depends on how much time the feces spends in

the colon Bulk from fiber (cellulose) stimulates receptors

to prompt bowel movements Too little water reabsorbed = diarrhea Too much water reabsorbed = constipation E. coli bacteria helps to break down any

undigestible material and produce vitamins and amino acids

Now we have reached the rectum, (for storing and compacting feces and

absorbing a bit of water),also known as....

THE END