Digestive System Notes

Basic Outline1. Movement: propels food through the

digestive system

2. Secretion: release of digestive juices in response to a specific stimulus

3. Digestion: breakdown of food into molecular components small enough to cross the plasma membrane

4. Absorption: passage of the molecules into the body's interior and their passage throughout the body

5. Elimination: removal of undigested food and wastes

Hungry?

The average male will eat about 50 tons of food (during his lifetime!) in order to sustain a weight of 150 lbs.

Mouth• Receptacle for food

• Begins mechanical digestion through chewing

• Swallow food

Esophagus

A simple conduit between the mouth and stomach

Did you know ?

It takes about 8 seconds for food to travel down the esophagus. The average time for your stomach to digest a high fat meal is 6 hours, as compared 2 hours for a carbohydrate meal. The average time for the digestion process in the small intestine is about 3 to 5 hours. This is followed by another 4 hours to 3 days(!) in the large intestine.

Stomach• Short-term storage

reservoir

• Substantial chemical and enzymatic digestion is initiated, particularly of proteins.

• Liquefaction of food

• Slowly released into the small intestine

Chemistry Flash

Organics Compounds: Carbohydrates

Proteins

Lipids

Carbohydrates (Carbs)

A group of organic compounds that includes sugars, starch and cellulose.

Functions of carbs: • Energy storage• Support/structure

Energy StorageAs plants photosynthesize, the energy from the sun is

stored in sugars and starch (both are carbohydrates).

a. Energy Storage - Sugars come in two forms:- monosaccharides (a single sugar unit)

ex. Glucose

- disaccharides (double sugar unit)ex. sucrose (glucose + fructose)ex. lactose (glucose + galactose)

Support/StructurePlant support: Cellulose (a polysac) provides

support for plants

b. Starch is a polysaccharide (a chain of monosacs).- Animals store carbohydrates in the form of glycogen (a polysac). - Glycogen is made in the liver muscles.

Energy Storage Cont.

Why do many athletes “carb-up” before a big

event?

ProteinsComplex organic compounds made up from smaller molecules called amino acids.

All the many, many types of proteins are made from only 20 different amino acids

Different combinations of a.a.’s produce different kinds of proteins.

Functions of proteins:

• movement (ex. actin and myosin in muscle fibers)

• structure (ex. collagen found almost everywhere in animals)

• regulation (ex. enzymes)• transport (ex. hemoglobin in blood)• nutrition• defense (ex. antibodies)

Lipids

Organic compounds that contain fats,

oils, waxes, phospholipids and

steroids. Fatty acid chains make lipids.

Functions of lipids:• Long-term energy storage (fats and oils)

• Protection and insulation (in animals)

• Water proofing (waxes)

• Body function and control (hormones and cholesterol)

• Structural (phospholipids - a major component of the cell plasma membranes)

Why do elephant seals have so much

fat?

Chemistry Flash Review• Be able to give an example of each of the

4 organic compounds (we learned one back in the DNA unit)

• Be able to give the function of each

• Be able to give the subunit (aka what is make up of)– Carbs – monosaccharide– Proteins – amino acids– Lipids – fatty acid chains– Nucleic Acids - nucleotides

Did you know ?

Your stomach produces a new lining every 3 days in order to avoid digesting itself in its own production of acid.

Liver, Pancreas and Gallbladder

• Liver: The center of metabolic activity in the body - provides bile salts to the small intestine, which are critical for digestion and absorption of fats.

• Pancreas: provides a potent mixture of digestive enzymes to the small intestine which are critical for digestion of fats, carbohydrates and protein.

• Gallbladder: stores and concentrates bile, and then releases it into the duodenum to help absorb and digest fats.

Small Intestine

This is where the final stages of chemical enzymatic digestion occur and where almost all nutrients are absorbed.

Large Intestine

• In all animals water is absorbed, bacterial fermentation takes place and feces are formed.

• Herbivores like the horse, the large intestine is huge and of critical importance for utilization of cellulose.

How long are your intestines?

At least 25 feet in an adult. Be glad you're not a full-grown horse -- their coiled-up intestines are 89 feet long!

Rectum/Anus• Rectum

It is the rectum's job to receive stool from the colon, to let the person know that there is stool to be evacuated, and to hold the stool until evacuation happens.

• Anus: The anus is the last part of the digestive tract.

The next slide has a map of the digestive system. Your notes need to include a map and you’ll need to be able to label parts. You can choose to copy figure included in these notes or figure 38-10 on page 979 in your textbook