Download Digestive and Excretory Systems

Digestive System
You are What You Eat!
7.12B identify the main functions of each system
7.6B distinguish between physical and chemical changes
7.6C recognize how large molecules are broken down into smaller
molecules such as carbohydrates are broken down into sugars
Digestive System
• Your cells need a lot of energy for their daily
activities
• Cells use nutrients obtained from food, for
energy, growth and repair
• The digestive system breaks down the
nutrients in food into smaller molecules that
can be used for energy and as building
materials for these cells.
Key vocab words!
• Carbohydrates – large molecules made of
carbon, hydrogen and oxygen.
• Enzymes – a protein made in a cell that is a
catalyst (speeds it up) in various biological
functions.
• Proteins – Compound made of amino acids.
• Fats – A soft compound stored in the body for
energy. Made of lipids.
Key vocab words!
• Bile – A substance produced by the liver that
breaks up fat particles.
• Metabolism – All of the chemical reactions
that occur within an organism
• Peristalsis – pronounced: per-uh-stawl-sis
involuntary waves of muscle contraction that
keep food moving along in one direction
through the digestive system.
Food into your body:
1. Proteins (meats), Carbohydrates (sugars =
energy), Fats (Lipids), Vitamins, Minerals, and
Water
2. Maintain homeostasis
3. No food has every nutrient, so eat a variety
of foods
THE DIGESTIVE SYSTEM’S FUNCTION:
breaks food down into
small molecules that are absorbed into bloodstream
1. Mechanical digestion: PHYSICAL process: food is chewed, mixed
and churned
2. Chemical digestion: CHEMICAL process: food is turned into a
mushy substance using stomach acid, bile, saliva, & other
enzymes (proteins that speed up chemical reactions)
Food’s journey Through the Digestive System
Step 1: The Mouth
• The mouth is the beginning of the digestive
system , and, in fact, digestion starts here
before you even take the first bite of a meal.
• The smell of food triggers the salivary glands
in your mouth to secrete saliva, causing your
mouth to water. When you actually taste the
food, saliva increases.
Food’s journey Through the Digestive System
Step 2: The Pharynx and Esophagus
• Also called the throat, the pharynx is the
portion of the digestive tract that receives the
food from your mouth.
• Branching off the pharynx is the esophagus,
which carries food to the stomach, and the
trachea or windpipe, which carries air to the
lungs.
Food’s journey Through the Digestive System
Step 3: The Stomach and Small Intestine
• The stomach is a sac-like organ with strong
muscular walls. Muscle contractions in the
stomach churn and mix food.
• The stomach secretes acid and powerful
enzymes that continue the process of
breaking the food down and changing it to a
consistency of liquid or paste.
• Bile breaks fats into tiny drops
Food’s journey Through the Digestive System
Step 4: Small intestine to the end
• From the stomach, food moves to the small
intestine.
• In the small intestine, nutrients are absorbed
through the walls and into the bloodstream.
What's leftover (the waste) moves into the
large intestine
• From the large intestine, waste goes to the
colon, rectum, and anus
Chemical Digestion
• Digesting food – pancreatic juices break down
carbohydrates, fats and proteins into simpler
substances so that enzymes can chemically
react with them to break down further
• pH changes in the stomach
• Video: How does digestion work?
Organs of the digestive system
1. Accessory organs: food DOES NOT pass
through. Includes tongue, teeth, salivary glands,
liver, gallbladder, & pancreas
Organs of the digestive system
2. Digestive tract: food DOES pass through.
Includes mouth, esophagus, stomach, small & large
intestine, rectum & anus
Digestion Begins:
1. Mouth: tongue, teeth, & saliva change food
into soft mass (called bolus)
2. Esophagus:
muscular tube
moves food to
stomach using
peristalsis which
are muscle
contractions
Inside the esophagus!
3. Stomach: muscular sac that turns food into a thin,
watery liquid called chyme
a. Mechanical digestion by peristalsis
b. Chemical digestion by digestive juices/enzymes
4. Small Intestine:
long tube (small
diameter) that
functions in
chemical
digestion and
nutrient
absorption
(most digestion
occurs here)
Inside the tube
(intestine), the surface
area for absorption is
increased.
How does the
surface area
increase?
The inside of the
“tube” isn’t flat,
it is full of ridges!
These ridges are
called villi, which
are finger-like
projections. And
there are smaller
ones insides of
these!!
Capillary bed
Microvilli
Each villus (single for villi) is composed of cells
that have microvilli. Cells transport nutrients
from these villi to the bloodstream through
capillary beds to be distributed to the body cells
Explained in a different way:
• If the small intestine were a simple smooth tube without folds
and villi, the surface area would be the inside of the tube as
seen below.
• The gathering of the intestinal wall into folds lined with villi
increases the surface area tremendously – imagine that the
folds are a string and you are pulling on the end. It would
unravel to a length much greater than that of the smooth
tube. In fact, it’s surface area is comparable to a tennis court!
• Let’s do a demo!
Accessory Organs of Small
Intestine:
a. Liver: large red-brown
organ that makes bile
b. Gallbladder: stores bile
which is released into
the S.I. and helps break
down fat
c. Pancreas: makes
digestive enzymes &
insulin which regulates
blood sugar
5. Large intestine: absorbs
water from undigested
chyme
a. Chyme can be in L.I.
as long as three days
b. Appendix: a sac
attached to the L.I.
that provides immune
support in the body
6. Rectum & anus: control
release of solid waste
(feces) from body
How nutrients are absorbed:
• Enzymes break down foods into smaller
particles so that the body can then absorb
nutrients!
Enzymes:
• Lactase – breaks down milk sugar
• Sucrase – breaks down table sugar
• Lipase –breaks down fat
• Pepsin – breaks down protein
Our Energy Source
• Video: Biological Molecules
•
(14min)
Diagram
• You will
label the
diagram
and write
down
information
based on
the notes
you have
just taken.
Digestion Gizmo Lab: