Transcript Introduction to the Digestive System Notes

Digestive
System
Notes
Basic Outline
1. 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 Storage
As 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)
Energy Storage Cont.
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.
Support/Structure
Plant support: Cellulose (a polysac) provides
support for plants
Why do many athletes
“carb-up” before a big
event?
Proteins
Complex 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