Download The Digestive System

Digestive
Function
 Break down food into molecules to obtain energy that
the body needs: (ATP)
4 steps involved:
Ingestion- take food in
2. Digestion- break down food
3. Absorption- keep molecules body needs
4. Elimination- get rid of waste
1.
Digestion can occur in 2 ways
 Mechanical- physical break down of the food- occurs in
the mouth using your teeth and also in the stomach due
to churning.
 Purpose -- increase the surface area so more sites are
available for the enzymes to act upon.
 Chemical- enzymes break the bonds
in the food. This occurs in the mouth,
stomach and small intestine.
Food Pathways We will follow the path of food
beginning in the mouth until it reaches the point of elimination.
 Mouth
 Liver
 Pharynx
 Gallbladder
 Epiglottis
 Esophagus
 Stomach
 Small intestine
 Pancreas
http://www.youtube.com/
watch?v=Z7xKYNz9AS0
 Large Intestine
Rectum
Mouth
 Site of mechanical digestion. Teeth break
food into smaller pieces to increase surface area for the
enzymes to work.
 Have different teeth for different food types.
 Salivary glands release saliva to mix with food.
Contains SALIVARY AMYLASE- enzyme which breaks
down carbohydrates.
 Saliva also acts as lubricant to help food go down the
esophagus.
 Act of chewing and tongue form food into BOLUS
before it is swallowed.
Swallowing
 When food is swallowed a small flap of tissue called
the EPIGLOTTIS covers the trachea (air pipe which
leads to lungs) so food goes down the correct tube.
 Esophagus-Muscle(smooth) covered tube that
connects mouth to the stomach
 Food is moved down the esophagus by waves of muscle
contraction called PERISTALSIS
The Mouth and Pharynx
Peristalsis http://health.howstuffworks.com/adam-200088.htm
Stomach
 Muscular pouch
 Mechanical digestion- churning
 Chemical digestion-pepsin digests proteins
 Other gastric juices and HCl (pH of 2) digest the
food (break the bonds between the molecules) and
turns food into a soupy liquid called CHYME
 Sphincter- acts as valves to let food into stomach
 Stomach is covered in thick mucous to prevent HCL
damage.
 Takes 2-4 hrs for food to leave the stomach
Esophagus and Stomach
The Small Intestine
 6 meters long
 Pyloric valve-valve between stomach and
small intestines
 Made of 3 sections: Duodenum ,Jejunum,
and Ileum
 Main site of absorption
 Pancreas-adds sodium bicarbonate
(NAHCO3) to balance PH
 Additional enzymes added here from small
intestine, pancreas, liver and gall bladder
Small intestine
Structure of small intestine
 The Small Intestine isn’t
a smooth tube- it has
little finger like
projections called villi
and micro villi that help
increase the surface area
of the small intestine
that allow for increased
absorption.
The Accessory Organs
Pancreas
 Secrets enzymes for
 Liver produces BILE
digestion (Pancreatic
 Bile helps digest fat by
Juice)
surrounding the fat
 Secretes Sodium
droplets so they break
Bicarbonate to balance
into smaller particles.
PH in intestines
(Emulsification)
 (Produces insulin-and
 Gall Bladder stores
glucagon to lowers and
bile and delivers it
raise blood glucose
when needed
levels)
Liver and Gall Bladder
Digestive Enzymes
Active Site
Enzyme
Effect on food
Mouth
Salivary
Amylase
Breaks down starches
Stomach
Pepsin
Breaks down proteins
Small intestine Trypsin
(from pancreas)
Amylase
Lipase
Small intestine
Sucrase
Maltase
Lactase
Lipase
Peptidase
Continues the breakdown
of proteins
Continues the breakdown
of starch
Breaks down fats
Breaks down remaining
disaccharides into
monosaccharides
Breaks down fats
Breaks down dipeptides
into amino acids
Large Intestine
 Main function- Absorb water
 Produce vitamin K with the help
of E. Coli bacteria that live in the
large intestine
 1.5 meters long
 Takes 18-24 hrs for waste to reach here
 Rectum-Storage of waste until it is eliminated
 Total time for digestion and elimination -24-33 hrs.
Nutrition
 Energy in food is measured in Dietary Calories (Big C)
 1 Calorie = 1000 calories
 Average American teenager needs to take in 2200-2800
Calories per day
 6 basic nutrients:
 carbohydrates,
 fats,
 proteins,
 vitamins,
 minerals ,
 and water
Carbohydrates
 Bread, pasta, fruits
 Main source of energy for our body
 Break down complex sugars into simple sugars
(glucose)
 Use glucose for ATP production
 Store excess in liver as glycogen. Some gets converted
to fats for storage.
 1g carb = 4 Calories
Fats
 Dairy, meats, nuts
 Provides energy and building blocks for your CELL
MEMBRANE (phospholipids) and hormones
 Fats are broken down into fatty acids and glycerol
 1g fat= 9 Calories
Protein
 Meat, beans, eggs
 Raw material for growth, repairs skin
and muscle
 Also used in transport and regulatory functions such
as hemoglobin and insulin.
 Broken down into the individual amino acids (20
essential) to make enzymes, antibodies, hormones
 Also need Nitrogen to make DNA and RNA for mitosis
and protein production
 1g protein = 4 Calories
Vitamins
 Vitamins are organic molecules that help to regulate
body processes Vitamins used to maintain growth and metabolism.
 Needed in small amounts
 Two kinds- fat soluble- D, E, K, A
 Can be stored in body
 and water soluble.- B1, B2, B6, B12, C, Niacin, Folic
Acid, Biotin, Choline, Pantothenic Acid
 Can not be stored in body.
Minerals
 Inorganic nutrients that the body needs.
 Minerals used for building material or in cellular
reactions.
 Need small amounts
 Inorganic substances like
 Fe, Ca, Na, Cl, Mg, P, K, S, I
Water
 Facilitates reactions and maintains
homeostasis
 Makes up the bulk of blood, lymph
and body fluids
 Average person needs to take in at least 1 liter /day
 Loose water through urine, sweating and exhalation
2000 Calories