Digestive and Excretory Systems

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Digestive and Excretory Systems
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Do Now
Section 38-1

• Good Food Sense
• Nutrients are molecules that provide the body
  with energy and materials for growth. Three kinds
  of nutrients you eat are called fats, proteins,
  and carbohydratesterms you may have already
  heard. Think about what they may mean.

1. Write a brief description of what you think
fats, proteins, and carbohydrates are. 2. Which
of these three nutrients do you think should make
up the largest part of your diet? Which should
make up the smallest part? Arrange the three
nutrients in order starting from the one that you
should eat the most to the one that you should
eat the least. 3. Why might it be unwise to eat
too much of the nutrient you listed last?
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Section Outline
Section 38-1

• 381 Food and Nutrition
• A. Food and Energy
• B. Nutrients
• 1. Water
• 2. Carbohydrates
• 3. Fats
• 4. Proteins
• 5. Vitamins
• 6. Minerals
• C. Nutrition and a Balanced Diet

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Food and Energy

• Cells convert the chemical energy stored in food
  into ATP
• When food is burned it releases heat energy,
  which is measured in calories
• A calorie is the amount of heat needed to raise
  the temperature of 1 gram of water 1 degree
  Celsius
• Dietary Calories refer to the energy stored in
  food.
• One Calorie 1000 calories
• Food also supplies the raw materials used to
  build and repair body tissues
• These raw materials are used to manufacture new
  biomolecules
• Food also contains at least 45 substances that
  your body cannot manufacture

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Concept Map
Section 38-1
Nutrients
include
include
are made of
include
include
are made using
such as
such as
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Carbohydrates

• Main source of energy for the body
• Can be simple
• Mono and disaccharides found in honey, fruits,
  sugar cane
• Can be complex
• Polysaccharides starches found in grains,
  potatoes, veggies
• Broken down by the digestive system to be
  absorbed into the blood and carried throughout
  the body
• If not used immediately, sugars are converted to
  glycogen, a complex carb and stored in the liver
  and muscles.
• Not all carbs can be broken down
• Fiber (cellulose) is used to keep your digestive
  system functioning properly by helping wastes to
  move through

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Fats

• Fats (lipids) formed from fatty acids and
  glycerol
• Needed to form cell membranes, myelin sheaths and
  some hormones
• Extra food is stored as fat to protect body
  organs and insulate the body
• Classified as saturated or unsaturated
• Saturated fats
• Solid at room temperature
• Main cause of high blood pressure, heart disease,
  obesity and diabetes
• Unsaturated fats
• Liquid at room temperature
• A healthier choice of fat

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Proteins

• Supply raw materials for growth and repair of
  skin and muscles
• Have regulatory and transport functions
• Ex. insulin, hemoglobin
• Polymers of amino acids
• The body can only synthesize 12 of the 20 amino
  acids
• The other 8 must be ingested
• Found in meat, fish, milk, eggs

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Figure 388 Food Guide Pyramid
Section 38-1
Fats, Oils, and Sweets (use sparingly) Soft
drinks, candy, ice cream, mayonnaise, and other
foods in this group have relatively few valuable
nutrients.
Bread, Cereal, Riceand Pasta Group (6-11
servings) The foods at the base of the pyramid
are rich in complex carbohydrates and also
provide proteins, fiber, vitamins, and some
minerals.
Fats
Sugars
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Section Outline
Section 38-2

• 382 The Process of Digestion
• A. The Mouth
• 1. Teeth
• 2. Saliva
• B. The Esophagus
• C. The Stomach
• 1. Chemical Digestion
• 2. Mechanical Digestion
• D. The Small Intestine
• Accessory Structures of Digestion
• E. Absorption in the Small Intestine
• F. The Large Intestine
• G. Digestive System Disorders

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Figure 3810 The Digestive System
Section 38-2



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The Mouth

• Performs mechanical and chemical digestion
• Mechanical food is changed in size
• Performed by the teeth
• Chemical food is changed in composition
• Performed by saliva
• Contains amylase (an enzyme that breaks down
  starch)
• Also helps to moisten food so it can move easier
• Contains lysozyme (an enzyme used to kill
  bacteria)
• The chewed up clump of food is now considered a
  bolus

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The Esophagus

• Lined with smooth (involuntary) muscle
• As the bolus passes through, contractions, known
  as peristalsis, squeeze the food through to the
  stomach
• The cardiac sphincter (a thick ring of muscle)
  closes the esophagus after food has entered the
  stomach to prevent the contents of the stomach
  from moving back up.
• Is associated with heartburn
• A backflow of stomach acid into your esophagus

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Stomach

• A large muscular sac
• Continues mechanical and chemical digestion
• Mechanical churning of bolus and stomach acids
  to form chyme
• Chemical stomach glands release a variety of
  secretions
• Hydrochloric acid activates pepsin
• Pepsin breaks down proteins
• Any other chemical digestion is stopped until the
  food reaches the small intestine
• Chyme then leaves the stomach through the pyloric
  valve and enters the small intestine

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Small Intestine (SI)

• Duodenum (1st part of the SI) where almost all of
  the digestive enzymes enter from accessory organs
• Shortest part of the SI
• Jejunum and Ileum
• Where absorption of nutrients occurs
• Villi increase surface area to allow for
  greater absorption
• Contain capillaries and lymph vessels
• Products of carbs and proteins are absorbed into
  the capillaries
• Undigested fats and fatty acids are absorbed by
  the lymph vessels
• Water, cellulose and other undigestible
  substances leave the SI and enter the large
  intestine

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Figure 3814 The Small Intestine
Section 38-2
Small Intestine
Villus
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Accessory Organs

• Pancreas
• Produces enzymes, that break down carbs,
  proteins, lipids and nucleic acids
• Also produces sodium bicarbonate to neutralize
  stomach acids so the enzymes will work
• Liver
• Produces bile, which dissolves and disperses
  droplets of fats, so that the enzymes can work on
  the smaller fat molecules
• Gall Bladder
• Stores the bile that is produced by the liver

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Figure 3813 The Liver and the Pancreas
Section 38-2
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The Digestive Enzymes
Section 38-2
Site Mouth Stomach Small intestine(from
pancreas) Small intestine
Enzyme
Role in Digestion
Salivary amylase Pepsin Amylase Trypsin Lipase
Maltase, sucrase, lactase Peptidase
Breaks down starches into disaccharides Breaks
down proteins into large peptides Continues the
breakdown of starch Continues the breakdown of
protein Breaks down fat Breaks down remaining
disaccharides into monosaccharides Breaks down
dipeptides into amino acids.
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The Large Intestine (LI)

• Also known as the colon
• Primary function is to absorb water from
  undigested materials
• Rich colonies of bacteria that are present in the
  LI produce compounds that the body is able to
  use, like vitamin K.
• The concentrated waste material that remains
  after the water has been removed passes through
  the rectum, where it is stored until it is
  eliminated from the body through the anus.

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Figure 3810 The Digestive System
Section 38-2
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Video 1
Video 1
Human Digestion

• Click the image to play the video segment.

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Interest Grabber
Section 38-3

• Your Bodys Filter
• Have you ever seen a water-purification system
  attached to a faucet?This system removes
  impurities from the water such as arsenic or
  other chemicals that can be harmful to people. As
  water passes through the filters contained in the
  system, the impurities are trapped on the surface
  of the filters. Eventually, the water that comes
  out of this purifier is free of the impurities.

1. Your body has its own system for filtering
blood. Why might the blood in your body need to
be filtered? 2. What organ(s) do you think
filters your blood? 3. How do you think the
filtered materials leave your body?
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Section Outline
Section 38-3

• 383 The Excretory System
• A. Functions of the Excretory System
• B. The Kidneys
• 1. Kidney Structure
• 2. Filtration
• 3. Reabsorption
• 4. Kidney Stones
• C. Control of Kidney Function
• D. Homeostasis by Machine

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Functions of the Excretory System

• Every cell in the body produces metabolic wastes
  as a result of maintaining homeostasis
• Wastes such as urea, excess salts and carbon
  dioxide must be removed from the body
• The skin, lungs and liver are three organs that
  assist in excretion
• The skin excretes excess salts, water and a small
  amount of urea
• The lungs excrete carbon dioxide
• The liver takes excess amino acids from the blood
  stream and converts them to useful compounds
• In the process of conversion, poisonous nitrogen
  compounds are created, which are turned into urea
• Urea is then removed from the bloodstream by the
  bodys principal organs of excretion the kidneys

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Kidneys

• The kidneys have many roles
• Remove waste products from the blood
• Maintain blood pH
• Regulate the water content of the blood and
  therefore blood volume
• As waste-laden blood enters the kidney from the
  renal artery, it removes urea, excess water and
  other wastes and passes them to the ureter
• The clean, filtered blood leaves the kidney
  through the renal vein and returns to circulation

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Kidney Structure

• Two distinct regions
• Renal cortex outer part
• Contains nephrons the functional units of the
  kidney
• Each one is a small, independent unit
• One part of a nephron, the loop of Henle, descend
  into the inner part of the kidney
• Renal medulla inner part

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Nephron

• Each nephron has its own blood supply
• An arteriole, a venule and a network of
  capillaries
• Each nephron releases fluid into a collecting
  duct, which leads to the ureters
• Blood purification involves two distinct
  processes filtration reabsorption
• Filtration takes place in the glomerulus, a
  small network of capillaries encased in Bowmans
  capsule
• Reabsorption most of the material (water, amino
  acids, glucose) removed from Bowmans capsule is
  taken back into the blood
• The material that remains is urine (urea, salts,
  water) and is concentrated in the loop of Henle,
  where water is conserved and the volume of urine
  is minimized.
• Urine is then stored in the bladder until it is
  released from the body through the urethra

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The Urinary System
Section 38-3
Artery
Vein
Kidney (Cross Section)
Kidney
Cortex
Medulla
Ureter
Urinary bladder
Urethra
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Figure 3817 Structure of the Kidneys
Section 38-3
Kidney
Nephron
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The Nephron
Section 38-3
Reabsorption As the filtrate flows through the
renal tubule, most of the water and nutrients are
reabsorbed into the blood. The concentrated
fluid that remains is called urine.
Filtration Most filtration occurs in the
glomerulus. Blood pressure forces water, salt,
glucose, amino acids, and urea into Bowmans
capsule. Proteins and blood cells are too large
to cross the membrane they remain in the blood.
The fluid that enters the renal tubules is called
the filtrate.
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Control of Kidney Function

• The activity of the kidneys is controlled by the
  blood itself.
• Water is absorbed into the blood from the
  digestive system.
• The concentration of water in the blood
  increases.
• Without your kidneys, the increase in water conc.
  would force water into cells and tissues, causing
  your body to swell
• As the amount of water in the blood increases,
  the rate of water reabsorption in the kidneys
  decreases.
• Less water is returned to the blood and the
  excess water is sent to the bladder.
• With an increase in salt, your kidneys return
  less salt to the blood, and send the excess salt
  to the bladder.

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Disease

• Kidney Stones
• Substances such as calcium, magnesium or salts in
  the urine crystallize and form stones
• These stones may block the ureter, causing great
  pain
• Often treated using ultrasound waves
• The stones gets pulverized into smaller
  fragments, which are then excreted in the urine.

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Homeostasis by Machine

• Dialysis
• Blood is removed from the body through a tube and
  pumped through special tubing that acts like
  nephrons
• Wastes diffuse out of the blood and into a
  fluid-filled chamber
• The purified blood is then returned to the body

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Figure 3819 Kidney Dialysis
Section 38-3
Blood in tubing flows through dialysis fluid
Blood pump
Vein
Artery
Used dialysis fluid
Shunt
Air detector
Fresh dialysis fluid
Dialysis machine
Compressed air
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Video 2
Video 2
Kidney Function
Click the image to play the video segment.