Human Digestion

“Who has the Guts?”

Digestion

There are 2 types of digestion:

Mechanical Digestion – breaks food into smaller pieces to increase surface area exposure to digestive enzymes

Chemical Digestion – breaks organic compounds into their building blocks

Mechanical/ Chemical Digestion

Chewing Salivary glands release saliva which

moistens the chewed food, now called a Bolus.

The tongue pushes the bolus to the back of the throat, called the Pharynx.

A flap of skin called the Epiglottis flips down and covers the entrance to the Trachea during swallowing

Swallowing Choking

Peristalsis/Alimentary Canal

The bolus passes through the esophagus by peristalsis

Peristalsis Food continues to pass through the

Alimentary Canal (any part that food passes through)

Mouth-Pharynx-Esophagus-Stomach-Small Intestine-Large Intestine-Anus

Accessory organs play a role in digestion, but food never enters them

Salivary glands-Pancreas-Gall Bladder-Liver

Anatomy of Digestion

Chemical Digestion

Enzymes break down the organic compounds (polymers) into their building blocks (monomers) so they can be absorbed into the blood stream and transported to all cells

Carbohydrates – Simple sugars Protein – Amino acids Lipids – Glycerol and 3 Fatty acids Nucleic acids - Nucleotides

Look in your textbook Chapter 38-2

Compare the digestion of Carbohydrates and Protein.

Follow the digestion of Carbs from the time they enter your mouth until the end products are absorbed into your blood.

Do the same for Protein.

Do you know your guts?

Try the quiz.

Digestion of Carbohydrates

Mouth – Mechanical digestion breaks the carbs into smaller pieces to increase the surface area exposure to enzymes.

Saliva lubricates the bolus. It contains the enzyme Amylase which begins the Chemical digestion of Carbs.

Polysaccharides are broken into shorter chains.

Swallowing pushes the bolus into the esophagus

Carbs in the Stomach

Peristalsis moves the bolus to the stomach. Cardiac sphincter opens and bolus enters

the stomach Bolus now mixes with the gastric juices of

the stomach. This acidic mixture is now called Chyme Mechanical digestion (churning) continues No chemical digestion of Carbs here

because of the acidity of the chyme Protein is digested here

Carbs in the Duodenum

Pyloric sphincter opens and chyme moves into the duodenum.

Pancreas secretes: Alkaline secretion that neutralizes the

acidic chyme Pancreatic amylase and disaccharase

continue the breakdown of carbs into simple sugars

Absorption of Simple Sugars

Small intestine is about 6 meters long!

The lumen of the small intestine is lined with Villi.

Absorption of Carbs

Each villi has microvilli on it’s surface

The infolds increase surface area contact so the simple sugars can pass into the blood by diffusion.

Small Intestine

Absorption is complete here. Peristalsis moves the digested food

mass to the Large Intestine (Colon)

Large Intestine Main function is to absorb water from the

unusable waste that remains. Too much water absorption –

constipation! Not enough water absorption – diarrhea! Bacteria in colon produce Vitamin K Feces passes from descending colon to

rectum and then is excreted through the anus (anal sphincter)

Accessory organs and their Functions

Salivary glands – Amylase Pancreas – Amylase

- Protease - Lipase

Liver – produces bile which is stored in the Gall Bladder and secreted into the duodenum through the Common Bile Duct

- Bile emulsifies fats

Digestion

Human Digestion

Have another look

Digestion Animation

Digestive Problems

Heart burn – acidic gastric juice enters the esophagus

Gastric ulcer – mucus lining of the stomach deteriorates and the gastric juice of the stomach begins to digest the stomach wall

Pig Dissection

Protein Digestion

1. Complete the handout questions on Digestion from your textbook.

2. Summarize in your notes the digestion of Protein. Include what happens in the mouth, stomach and small intestine. Identify the enzymes that play a role in protein digestion.

3. At your table, on flip chart paper, compare the digestion of carbs and protein.