Transcript Human Digestion

Aim: What are THE structures and functions
of THE human digestive system?
I. THE Human Digestive system – gets THE
nutrients from THE food you eat into your
cells.
A. Tube-within-a-tube body plan – alimentary
canal (digestive tract) that THE food stays in.
B. One Way digestive tract – THE food enters
through THE mouth (ingestion), gets digested
throughout the digestive tract, and undigested
food is egested out through THE anus.
C. Digestion Organs
1. Mouth – performs both mechanical and
chemical digestion.
a. THE teeth chew food (mechanical) THE
to increase THE surface area for chemical
digestion (incisors, canines, molars).
b. Saliva contains THE enzymes amylase
which begins THE chemical digestion of
starch into sugars.
2. Pharynx – where THE respiratory and
digestive system meet. Food passes through to
THE esophagus.
What is the meaning of the expression
“the food went down the wrong tube?”
3. Epiglottis – flap of tissue that closes off
the trachea during swallowing to prevent food
from entering it.
4. Esophagus – pushes food towards THE
stomach. No digestion occurs here. Peristalsis
starts here.
a. Peristalsis – waves of muscular contractions
that push food throughout the digestive tract.
It starts in the esophagus and continues all the
way through the large intestine.
5. Stomach – both mechanical and chemical
digestion occur here.
a. Three layers of muscles that churn (mix) the
food (mechanical digestion).
b. Gastric glands release the enzyme pepsin
and hydrochloric acid. Pepsin chemically
digests proteins into peptides.
Why does the stomach have a mucus
lining?
It protects the inner lining by neutralizing the
hydrochloric acid.
c. Chyme – the liquid substance that leaves
the stomach and enters the small intestine.
6. Liver (accessory organ) – produces the
substance bile which is stored in the gall bladder
(accessory organ).
a. Bile emulsifies
(mechanically breaks
down) fats. It is
released into the small
intestine via the bile
duct.
7. THE Pancreas (Accessory organ) – produces
pancreatic juice which is released into the small
intestine via the pancreatic duct.
a. Pancreatic juice contains enzymes that
break down fats (lipase), starch (amylase),
and proteins (trypsin).
Q. Why does most chemical digestion
occur in the small intestine?
A. Because it contains enzymes that break
down each nutrient.
Q. The small intestine is 23
feet long. Why is it called
THE small intestine?
8. THE Small Intestine – chemical digestion and
absorption occur here. Last place that digestion
occurs.
a. Intestinal juice contains enzymes that
break the nutrients into their smallest
subunits. Ex: carbohydrates into
monosaccharides, proteins into amino acids, and
lipids into fatty acids and glycerol.
b. Villi – finger-like projections that line the
wall of the small intestine. Increase the
surface area for both digestion and
absorption. Nutrients enter the bloodstream
through the villi.
9. THE Large Intestine – reabsorbs water into
the body and eliminates feces.
10. Rectum – feces (digestive wastes) is
temporarily stored here before being
eliminated through the anus.
List the organs of the digestive tract that food
passes through, starting with the mouth and
ending at the anus.