AP12 Unit 3

For Us

The Role of the Digestive System (3 Points)

1. Ingestion (Ingests Food)

2. Separates food into chemical nutrients that cells can use.

3. Eliminates Indigestible Remains.

What are the 2 Types of Digestion?

1. Mechanical Digestion

2. Chemical Digestion

What is Mechanical Digestion?

Mechanical Digestion is breaking food into smaller bits.

• Chewing, Churning, Emulsifying.

Chewing: Using our teeth to break up food.

Churning: Our stomach contracts to mix the stomach acid with the food whilst also breaking it up more.

Emulsifying: Breaking fat into smaller droplets without breaking any chemical bonds.

What is Chemical Digestion?

Chemical Digestion is the process where enzymes help break polymers into monomers that can be absorbed by the body.

• Chemical Bonds are broken.

Food Pathway (Where does food travel)?

Food travels through the oral cavity, pharynx, esophagus, stomach, small intestine, and the large intestine.

Parts of the Mouth (Oral Cavity) (3 Parts)

1. Teeth

2. Tongue

3. Palates

Teeth

Mechanically breaks food into smaller pieces to maximize surface area.

Tongue

Helps mix food with saliva to form a bolus.

Palates (2 Types)

Hard Palate

-Helps with breaking down food.

Soft Palate

-Separates the nasal cavity from the mouth.

Parts of the Throat (2 Parts)

1. Pharynx

2. Epiglottis

Pharynx

Directs air to the trachea and food/liquid to the esophagus. When the bolus presses against it, swallowing occurs, and it sends a signal to the brain to move the epiglottis.

Epiglottis

Covers the opening to the trachea so that food does not enter the lungs.

Esophagus

A long muscular tube that connects the Pharynx to the Stomach.

-It performs smooth muscle contractions called Peristalsis to move the bolus down the esophagus, past the esophageal sphincter, and into the stomach.

Esophageal (Cardiac) Sphincter

The sphincter that is at the entrance of the stomach. It seals the stomach so that its acid won’t splash up into the esophagus.

Sphincter

A circular ring-like muscle that normally stays constricted to close a natural body passage or opening, and relaxes to let substances pass through.

Rugae

Folds in the stomach walls that can expand as the stomach fills.

Stomach & Alcohol

A small percentage of alcohol is absorbed into the blood through the stomach.

3 Products of the Gastric Glands in our Stomach

1. Hydrochloric Acid

Denatures proteins and gives the stomach its acidic properties.

2. Pepsinogen & Pepsin

Pepsinogen is a proenzyme (inactive enzyme) that turns into pepsin in acidic conditions. Pepsin is an enzyme in the stomach that breaks down proteins.

3. Mucus

Protective substance that stops our stomach from getting digested.

Chyme

Thick, soupy liquid composed of the food our stomach just mechanically digested. When food leaves our stomach, it is chyme.

Pyloric Sphincter

The sphincter at the bottom of the stomach. It regulates food (chyme) leaving the stomach.

3 Parts of the Small Intestine

1. First is Duodenum

2. Second is Jejunum

3. Lastly is Ileum

Where does most of the Chemical Digestion and Nutrients Absorption occur?

Small Intestine

Where is Bile made and stored?

Bile is made in the Liver and stored in the Gall Bladder.

What are the two substances secreted into the duodenum?

Pancreatic Juice and bile are secreted into the Duodenum through the common bile duct.

What does Pancreatic Juice contain to neutralize chyme and make it slightly basic (pH ~ 8) ?

Bicarbonate Ions (HCO₃^-)

Villi

Tiny projections that act like a filter to catch & absorb nutrients. They are covered by even smaller microvilli.

What are inside each Villus (Single Term for Villi)? ( 2 Things)

• Capillaries

Transport water-soluble nutrients (sugar, amino acids, nucleic acids) into the bloodstream.

• Lacteals

Brings lipids to the lymphatic system to be processed and broken down more.

3 Primary Functions of Large Intestine

1. Absorbing water and electrolytes from the chyme passing through.

2. Produces and absorbs vitamins.

3. Stores the indigestible material until it is removed as feces (poop).

4 Parts of the Large Intestine

1. Cecum

2. Colon

3. Rectum

4. Anus

Cecum

Small pouch of the Large Intestine. It includes the appendix.

Colon

Where electrolytes and water are absorbed. Gut bacteria ferment indigestible material and produce vitamins (Such as Vitamin K and Vitamin B), which our colon also absorbs.

4 Parts of the Colon

1. Ascending

2. Transverse

3. Descending

4. Sigmoid

Rectum

Where feces are collected, compacted, and stored before elimination.

Anus

Made up of two Sphincters that hold in the feces.

• Internal Sphincter: we can’t control it.

• External sphincter: we can control it.

When both relax, we start a bowel movement (we poop).