Download 3.2 Organs and Systems

Digestive System


Mechanically &
chemically breaks
down food so the
body can use
nutrients
The major organs
are the stomach,
liver, pancreas,
and intestines
See Figure 3.14A on p. 97
Mouth  Pharynx  Esophagus
Mouth
 Teeth break down food into smaller pieces
 Enzymes (protein) in saliva begin chemical digestion
 Swallowed food passes through the pharynx to the
esophagus
Esophagus
 Is a muscular tube that contracts
& relaxes to push chunks of
food down to the stomach

Waves of muscle contraction
is called peristalsis
Stomach

Contains liquids called gastric
juices that chemically break
down the food more


Stomach muscles mix the
contents, which continues the
mechanical breakdown of food


are highly acidic
churning action of stomach & gastric
juices cause food to break down into
a liquid
Food is pushed into small intestine
Small Intestine



Divided into 3 sections:
1. duodenum  where the rest
of digestion takes place
2. jejunum
3. ileum  where absorption
of nutrients takes place
Pancreas, liver, and gall bladder release digestive enzymes
into the duodenum via small tubes called ducts
Walls of the small intestine are covered with little projections
called villi (& microvilli)

they increase the surface area so that more nutrients and water can be
absorbed into the bloodstream
See Figure 3.15 on p. 98
See Figure 3.16 on p. 98
Large Intestine


Includes the colon, rectum, & anus (oh geez)
Absorbs water, vitamins salts from digested
food


achieved by bacteria in the
gut like E.coli
Remaining (undigested)
food is eliminated as feces
Sooooo… let’s recap

The path of a meal from start
to finish:


mouth  pharynx 
esophagus  stomach 
small intestine  large
intestine
Weird facts:


it takes 24 to 33 hrs for a meal
to go from beginning to end
of this system
the small intestine is between
6 – 10 m in an adult
Quizzy, quizzy…
1.
2.
3.
4.
5.
Identify the structures A. – E.
Name 3 organs that help digest
food that enters the small intestine.
Name the 3 sections of the small
intestine.
Give 4 organs in the digestive
system that chemically break down
food and explain how each occurs.
Which part of the digestive
systems mechanically breaks down
food?
Urinary (Excretory) System



Composed of the
kidneys, ureter,
bladder, urethra, and
blood vessels
Eliminates liquid
wastes from the body
Interacts closely
with the circulatory
& digestive systems
Kidneys: Liquid Waste’s Last Stop

As blood passes through the kidneys, it is
filtered and wastes are removed



Remember nephrons? Those are the tiny
structures within the kidneys that do the
filtering
Urine forms from excess water and
unneeded salts in the blood (called urea)
Urine is stored in the bladder and then
excreted through the urethra
Nephrons
Urine trouble if you don’t know the
answers to these questions!
1.
2.
3.
Name the 4 major structures that compose
the urinary system.
How is the urinary system different from the
digestive system?
What tiny structure in the kidney is
responsible for filtering blood of its wastes?