Download Digestive and Excretory Systems

WHAT HAPPENS WHEN YOU EAT?
We eat food to obtain the six basic nutrients our body
needs to function
Carbohydrates – Composed of carbon, hydrogen and
oxygen in a ratio of 1:2:1. Their monomers are
monosaccharides.
Proteins – Consist of long chains of amino acids.
These are a very important structural component of
your body!
Lipids – Composed of fatty acids and contain lots of
Carbon-Hydrogen bonds which store lots of energy.
WHAT HAPPENS WHEN YOU EAT CONT.
There are 3 more nutrients your body needs
Vitamins – Complex organic molecules which
help your enzymes function (coenzymes) (Vit
A, Vit B)
Minerals – Inorganic substances required for
normal body function. (iron, sodium)
Water – Makes up over ½ your body weight.
Most reactions necessary for life happen in
the water of your body.
THE DIGESTIVE SYSTEM
Before your body can use the nutrients in the
food you eat, the food must be broken down
into its simpler components – the
monomers.
Digestion – The process of breaking food
down into molecules the body can use.
THE DIGESTIVE SYSTEM CONT.
Digestive Tract/Gastrointestinal Tract – A
continuous tube through the body which
breaks down food.
Continuous – Means it is a
SINGLE tube through your body
– just shaped into various
parts.
The food you eat never leaves
this tube unless it has been
broken down into a small
molecule or as feces.
DIGESTIVE SYSTEM CONT.
There are 2 types of organs in the digestive system.
 Those organs which make up the continuous tube (those which actually make up the
gastrointestinal tract)
 Those which food doesn’t move through but produce substances which help digestion
(accessory organs)
 Take some time to label the organs of the digestive system - we will discuss each of these
later!
A TRIP THROUGH THE GI TRACT!
Mechanical Digestion – Physically breaking large
chunks of food into smaller ones.
This helps your enzymes attach to the food and
break it down.
Chemical Digestion – involves a change in the
chemical nature of the food. (polymers into
The action of the tongue, teeth
monomers)
and saliva will form the food into
The Mouth:
a ball called a bolus
Teeth – Your teeth begin the
mechanical
Nowprocess
the foodof
is ready
to be
digestion.
swallowed and continue its
journey
yourglands.
body.
The food is mixed with saliva
fromthrough
salivary
Your saliva contains an enzyme which begins the
Chemical Digestion of carbohydrates.
TRIP THROUGH THE GI TRACT CONT.
Swallowing forces the food into the pharynx (the
throat).
The pharynx is shared by both the digestive and
respiratory systems.
Epiglottis – A small flap of tissue which covers the
opening to the trachea and prevents food from
entering the lungs.
From the pharynx, the food moves into the
esophagus.
Food moves through the esophagus via peristalsis: a
series of rhythmic contractions of both the circular
and longitudinal muscles of the esophagus.
TRIP THROUGH THE GI TRACT CONT.
After the esophagus, the food arrives in the
stomach where both mechanical and
chemical digestion occur.
The strong muscles of the stomach churn any
food inside – breaking into smaller pieces.
Gastric Fluid inside the stomach carries out
chemical digestion.
Gastric Fluid activates an enzyme called
pepsin which breaks down proteins.
THROUGH THE GI TRACT CONT.
Once food is done in the stomach, it moves into the
small intestine.
The small intestine has 3 parts and is nearly 21 feet
long!
Duodenum – First part of the sm. Intestine
Jejunum – Middle portion of the sm. Intestine.
Ileum – Final portion of the sm. Intestine.
Inside the sm. Intestine, chemical digestion finishes and
absorption occurs.
Chemical Digestion –
Bile (which is made in the liver and stored in the gall
bladder) breaks down fats.
The pancreas secretes many enzymes which finish
the break down of other nutrients.
TRIP THROUGH THE GI TRACT CONT.
Absorption of nutrients – Transferring the nutrients
into the blood stream.
The inside of the small intestine contains villi –
fingerlike projections which increase the surface
area available for absorption.
TRIP THROUGH THE GI TRACT CONT.
Any remaining material moves into the large intestine
(colon).
There are 4 main parts to the colon:
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Bacteria feed on the undigested material and
produce vitamins for us
Any water not absorbed in the sm. Intestine is also
absorbed
Any remaining material moves out of the anus as
feces.
ENZYMES: A CLOSER LOOK
There are some very important digestive
enzymes to know!
Salivary Amylase: Made in the salivary glands
and breaks down carbohydrates
Pepsin – Made in the pancreas and breaks
down proteins
Bile – Made in the liver, stored in the gall
bladder and breaks down fats.
THE URINARY SYSTEM
Breaking food down into useful nutrients causes wastes to
build up in the blood stream.
Excretion – The process of removing metabolic wastes
from the body.
There are 2 main waste products your body must remove
Carbon Dioxide – made when your cells convert sugars
into ATP (energy)
Nitrogen Wastes – Caused by the break down of
proteins
The lungs remove most of the Carbon Dioxide from your
system
The kidneys remove the nitrogen wastes from your
system.
Medulla: The inner 2/3 of the
kidney.
THE KIDNEYS
Collecting Ducts – Take the
urine produced in the nephrons
and deliver it to the ureter
Cortex: The outermost 1/3 of
the kidney.
Nephron: Forms the urine. This
is the functional unit of the
kidney!
FORMATION OF URINE
In each kidney, the nephron filters wastes from the
blood.
Water is also removed from the blood to keep the
concentration of wastes low (high concentrations
can kill you)
Once urine is formed it flows through collecting ducts
into ureters.
The ureters transfer urine into the urinary bladder
where it is held.
Urethra transfers the urine from the bladder to the
outside environment.
WATER CONSERVATION
While some water is necessary to produce
urine, the body is able to adjust the amount
of water used to make urine.
In times when you have excess water in your
system (or by drinking caffeine) your kidneys
allow more water to be used to make urine.
In times when you are dehydrated, your
kidneys allow less water to make urine
This will lead to production of a dark yellow
urine because the wastes are more
concentrated!