1. Nutrient Absorption and Delivery

2. How does digestion occur?
Starts in the mouth with mechanical chewing
Saliva contains an enzyme called amylase to break down carbohydrates.

3. How does digestion occur?
Once chewing has occurred and the food is digested into a smooth small ball, the food is swallowed.
It passes through the esophagus to the stomach.
The esophagus uses wave-like muscular contractions called peristalsis to move the food along the passageway.

4. How does digestion occur?
In the stomach, HCl in the stomach juices and an enzyme called pepsin breaks the peptide bonds in proteins.
The muscles in the stomach also contract stirring the food around in the juices causing them to break down more.

5. How does digestion occur?
The food now passes from the stomach to the small intestine.
In the small intestine, secretions from the pancreas complete carbohydrate digestion.
Secretions from the liver, called bile, breaks up fats into small globules that are then digested by lipases, a pancreatic enzyme.

6. How does digestion occur?
Most absorption of nutrients occurs in the small intestine.
The lining of the small intestine is specialized for this job.
Villi, finger-like projections that line the small intestine, increases the surface area so more absorption can occur.

7. THINK OF THE RELAY WE DID!!!
Once the nutrients are absorbed in the small intestine, what happens to them?
HINT: These are VEINS and ARTERIES!
THINK OF THE RELAY WE DID!!!

8. How does digestion occur?
In the large intestine, the leftover materials become waste. Water is absorbed leaving behind solid waste that is passed out of the anus.

9. How does digestion occur?

10. How does digestion occur?
The large intestine is full of little helpers!
These helpers digest any remaining unused materials, stimulate cell growth, keep out harmful microbes, and produce vitamins such as biotin and vitamin K.
Who are these little helpers???
BACTERIA!!!

11. Overview: Human Digestive System
What is the function?
Take in food, break it down into molecules small enough for absorption
What are the primary components?
Mouth
Esophagus
Stomach
Small intestine
Large intestine
Anus
What are the secondary components?
Salivary glands, Liver, Gallbladder, Pancreas

12. Add the following on your flowchart--
What is digested in each segment of the digestive tract?
What enzymes are present in each stage of the digestive tract?
Specialized structures to aid in digestion
Secondary organs that play a role in digestion

13. Digestion in Animals
Simple animals, such as hydra and flatworms, have a gastrovascular cavity, a digestive cavity with only one opening.
Cells cannot be specialized within a gastrovascular cavity because every cell is exposed to all stages of digestion.

14. Digestion in Animals
All other animals have a digestive tract (gut) with two openings, a mouth and an anus.
The anus is the opening through which undigested food leaves the body.
Food moves in one direction, from mouth to anus.
Allows for specialization
For example, one section of gut may be for food storage, one for breaking down food mechanically, one for chemical digestion.
Eventually food is broken down into molecules small enough to pass through the lining of the gut into the bloodstream.