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DIGESTIVE AND EXCRETORY SYSTEMS
Regents Biology
OBJECTIVES
Upon completion of this unit students will be able to:
1. Contrast autotrophs and heterotrophs.
2. Describe the functions of the six basic types of nutrients found in the human diet.
3. Differentiate mechanical and chemical digestion of food.
4. Compare digestive processes in different organisms.
5. Describe the functions of the different parts of the human digestive system.
6. List and describe the major functions of the digestive enzymes.
7. Define excretion and describe how it maintains homeostasis.
8. Name the major metabolic wastes.
9. Describe the process of urine formation.
10. Explain the excretory functions of the liver, lungs, skin, and kidneys.
KEY WORDS
1.
2.
3.
4.
5.
autotroph
bile
excretion
kidney
liver
6.
7.
8.
9.
10.
lung
nephron
peristalsis
sebaceous gland
skin
DIGESTIVE SYSTEM
I. NUTRITION
 Nutrition is the process by which organisms OBTAIN food and
BREAK IT DOWN for use
 Nutrients are used for metabolism. There are 6 nutrients, four are
organic (which means that they contain CARBON) and two are
inorganic, which means that they do not contain CARBON)
ORGANIC NUTRIENTS




CARBOHYDRATES
LIPIDS
PROTEINS
VITAMINS
INORGANIC NUTRIENTS
 WATER
 MINERALS
 FIBER is not a nutrient, but is very important for the digestive
system. Fibers are bulky, indigestible materials (like cellulose) that
stimulate the MUSCLES OF DIGESTION
II. ENERGY
• We need energy to carry out LIFE PROCESSES
• The energy in food is the energy given off by
BURNING the sample; a CALORIMETER is used to
measure this
• A unit of energy is called a CALORIE
• We vary in our daily calorie requirements
o Young vs. old
o Male vs. female
o Active vs. inactive
• If you ingest more calories than you burn, then you
will GAIN weight
• If you ingest fewer calories than you burn, then
you will LOSE weight
III. TYPES OF NUTRITION

Autotrophs:MAKE THEIR OWN FOOD
o Phototrophs use photosynthesis
o Chemotrophs use chemicals (non-photosynthetic)
 Heterotrophs: MUST OBTAIN FOOD THAT IS “READY
MADE”
IV. TYPES OF DIGESTION

Nutrient molecules in food are too large to pass through
the cell membrane, so they must be broken down. There are 2
types of digestion.
o CHEMICAL: FOOD IS CHEMICALLY ALTERED;
USES ENZYMES
o MECHANICAL: FOOD IS PHYSICALLY ALTERED
(CUT, CRUSHED, ETC.); INCREASES SURFACE
AREA OF FOOD
V. DIGESTION IN REPRESENTATIVE HETEROTROPHIC
ORGANISMS
A. Protozoans
 Ameoba and paramecium use INTRACELLULAR digestion
(digestion within the cell)
 The amoeba uses pseudopods for PHAGOCYTOSIS
 The paramecium uses its CILIA in getting food into its oral groove
and into the gullet, then out the anal pore.
B. Hydra
 The hydra actually has stinging cells along its exterior, and captures
food with its TENTACLES
 Food goes into the mouth into the GASTROVASCULAR CAVITY
 Uses both intracellular and EXTRACELLULAR digestion
 There is only ONE body opening to the digestive cavity (“two way
traffic”); material not digested goes out the same opening it entered.
C. Earthworm
• The earthworm has “one way” digestion;
there are two body openings, the MOUTH and
the ANUS
• The CROP is used for storage of food, and
the GIZZARD is used for grinding up food
• Let’s label this!
D. Grasshopper
•The grasshopper has a digestive
tube, somewhat similar to the
earthworm, but has chewing
mouth parts which help to
MECHANICALLY digest food in
preparation for chemical
digestion.
VI. HUMAN DIGESTIVE SYSTEM
• Humans have a digestive tract, or
ALIMENTARY CANAL, similar to (but not
exactly like) the earthworm and grasshopper.
• Digestive ENZYMES are secreted along the
lining of the alimentary canal; some accessory
glands that secrete enzymes are:
1.Salivary glands - SALIVA
2.Liver - BILE
3.Pancreas – PANCREATIC JUICE
• Mucus is secreted for LUBRICATION
•The path of digestion for humans is:
Let’s start at the beginning shall we?
A.
Mouth and Pharynx
o The mouth provides MECHANICAL and CHEMICAL digestion; the
teeth and tongue movements are mechanical and the salivary
amylase is chemical
o The EPIGLOTTIS is the flap that prevents food from going into the
larynx and down the pharynx
http://www.easttroy.k12.wi.us/hs/dept/science/bottum/Adv%20Biology/digestive/danatomy/images/Pharynx.gif
http://www.esg.montana.edu/esg/kla/ta/pharynx.jpg
B.
Esophagus
o The esophagus carries food from the pharynx to the STOMACH
o The process of PERISTALSIS is the contraction and relaxation of
the muscular wall of the alimentary canal. Peristalsis is what moves
food through and out of your body.
o Do you know what’s going on when you “throw up” (vomit)?
Basically, it is REVERSE PERISTALSIS, as your sphincter muscle
opens up, releasing food back up into your esophagus, and the
stomach contents are “thrown up”
o There is a “ring” muscle that is
found at the opening of the stomach
called the SPHINCTER. It controls
the passage of food into the stomach.
There is also a sphincter muscle found
along the rectum; you can guess what this
is for.
http://www.medicalook.com/systems_images/Esophagus.jpg
A.
Stomach
o The stomach can EXPAND and hold 2 Liters of food
o Both MECHANICAL (churning) and CHEMICAL (gastric juice)
digestion takes place here
o Gastric juice contains HYDROCHLORIC ACID (HCl) and PEPSIN
(which breaks down proteins)
o The flow of gastric juice increases with stimulation, and liquids
pass through in 20 minutes!
o Solids must be reduced to a soupy mixture called CHYME
o The stomach usually empties 2-6 hours after a meal
o When the mucus lining in the stomach breaks down, an ULCER
forms
http://www.pharmainsight.ca/anatomical-images/stomach1.jpg
http://courses.washington.edu/chordate/453photos/gut_photos/rabbit_stomach.jpg
A.
Small intestine
o The small intestine is 6.5 meters long (21.33 feet) and 2.5 cm wide
and serves mainly to ABSORB nutrients in food
o The first section of the small intestine is called the DUODENUM.
Two accessory organs that help the duodenum to do it job are the
LIVER and the PANCREAS
1. LIVER – The liver manufactures BILE and the gall bladder stores it
between meals. Bile breaks up FAT globules
2. PANCREAS – releases pancreatic juice, which contains several
enzymes. Lipase acts on LIPIDS, amylase acts on
CARBOHYDRATES , and proteases act on PROTEINS
o (Review) The end products of:
1) protein digestion are AMINO ACIDS
2) fat (lipid) digestion are FATTY ACIDS AND GLYCEROL
3) carbohydrate digestion are MONOSACCHARIDES
o The second section of the small intestine is the JEJUNUM and the
third is the ILEUM
o Millions of small finger-like projection in the small intestine, called
VILLI absorb the end products of digestion increase the surface area
of the small intestine
o Once the end products of digestion enter the bloodstream, they can
be transported to all cells of the body. These molecules can be used
for growth or energy (cellular respiration).
oUndigested matter is pushed in to large intestine, or COLON, by the
process of PERISTALSIS
A.
Large intestine
o Also called the COLON
o Undigested and unabsorbed materials go from the small intestine
to the large intestine
o The large intestine is 1.5 m long and 6 cm wide
which is SMALLER than the small intestine
o The main function of the large intestine is to
ABSORB WATER from food into the body
(WATER!!!!!)
DIARRHEA
CONSTIPATION
TOO LITTLE WATER
ABSORBED, SO IT
COMES OUT!!
TOO MUCH WATER
ABSORBED, SO
YOU’RE ALL
BOUND UP!
o The large intestine also absorbs VITAMINS
and eliminates indigestible material (feces)
to the RECTUM
http://images.google.com/imgres?imgurl=http://www.medicalook.com/diseases_images/constipation.gi
http://images.google.com/imgres?imgurl=http://www1.istockphoto.com/file_thumbview_approve/424743/2/istockphoto_424743_constipation.jpg&imgrefurl
F. Rectum
o The rectum STORES FECAL MATTER
G. Anus
o The anus eliminates FECAL MATTER
THE EXCRETORY SYSTEM
• Excretion is THE PROCESS WHERE
METABOLIC WASTES ARE REMOVED
• There are different types of wastes produced
from the body:
A. Respiratory wastes include CARBON
DIOXIDE AND WATER
B. Nitrogenous wastes include AMMONIA,
UREA, URIC ACID
C. General metabolic wastes include MINERAL
SALTS
A. Protozoans
 Since they are unicellular, they get rid of waste by DIFFUSION
 As CO2 moves out of the organism, so does nitrogenous waste.
The main nitrogenous waste of Protozoans is AMMONIA
 By what process would a cell get rid of waste that is already in
higher concentration in the surrounding environment? ACTIVE
TRANSPORT
B. Hydra
 Then hydra is multicellular, but only two cell layers thick
 It gets rid of waste by DIFFUSION
 The main respiratory waste is CARBON DIOXIDE
 The main nitrogenous waste is AMMONIA
C. Earthworm
 The earthworm gets rid of CO2 by diffusion into the blood and then it
is transported to the moist SKIN where it diffuses out of the body.
The main nitrogenous waste is UREA. It is excreted by special
structures called NEPHRIDIUM. These structures are located
ALONG THE SEGMENTS (LINES) and each segment has 2 of them
A. Grasshopper
 The respiratory gas, carbon dioxide is removed by tracheal tubes.
 The main nitrogenous waste, URIC ACID, is removed from body
fluids by special structures called MALPIGHIAN TUBULES, which
extend into the body sinuses.
 These wastes are then dumped into the INTESTINE and then
excreted from the body along with digested wastes.

1
A. Humans
 The excretory organs of the human include the:
1. SKIN – excretes UREA AND SALT
2. LUNGS – excretes CARBON DIOXIDE AND WATER
3. LIVER – excretes BILE, UREA, TOXICS FROM
BLOOD
• Urea, a nitrogenous waste, is made by the LIVER. It is released into
the bloodstream and THE KIDNEYS remove it from the blood.
• The process by which amino acids are broken down is called
DEAMINATION; these amino groups are combined with carbon
dioxide to form UREA
• Urea is LESS toxic than ammonia (NH3)
• The kidneys have two main functions: FILTRATION AND
REABSORPTION
• Filtration of blood occurs as it enters the kidneys by way of the
RENAL arteries. The fluid which enters the Bowman’s capsule is
called NEPHRIC FILTRATE because it is the filtered blood that comes
from the nephrons (the functional unit of a kidney)
• The liquid which leaves the kidneys and enters the URETERS is
called URINE
• Urine contains WATER, UREA, SALTS, GLUCOSE
• The two ureters empty the urine into the URINARY BLADDER until
the ring muscle, called a SPHINCTER (Cal Egan), relaxes and
releases the urine into the URETHRA which carries the urine out of
the body.
 Let’s make a flow chart of excretion, ay?