Download Where does Food go? The Digestive System

Where does Food go?
The Digestive System
Where does Food Go?
• The cells of the human body cannot use food
directly for energy
• Food must be transformed in the digestive
system before it can be put to use
• The role of the digestive system is to break
down ingested food into molecules that are
small enough to be absorbed by the body’s
cells
• It eliminates undigested food in the form of
solid waste
Transformation and Selection
• The food and air (oxygen) that enter your
body are known as INTAKE.
• The INTAKE is not utilized by the body in the
form in which it enters: it undergoes
transformation or change and then a selection
process.
• Your DIGESTIVE SYSTEM breaks down and
sorts that intake.
• It transforms the food by mechanical and
chemical transformations.
Mechanical Transformation
• Changes the appearance and movement of food from
one place to another
• The composition (what its made of) of the resulting food
remains unchanged
• Examples
– Ingestion in the mouth: INCREASES the surface area of the
food in order to aid in chemical digestion
– peristalsis  series of involuntary wave-like muscle
contractions which move food along the digestive tract
– Churning : produced by muscle contractions, which mix
food with digestive secretions
Peristalsis
Chemical Transformations
• Breaks down complex molecules into simpler
molecules
• Occurs with the help of secretions from the
digestive glands
• Is carried out by the digestive ENZYMES
The Digestive System
• Can be broken into 2 parts:
– Digestive tract
– Digestive glands
• The digestive tract is composed of:
– The mouth
– The pharynx
– The esophagus
– The stomach
– The small intestine
– The large intestine (which ends with the rectum
and anus)
Diagram of the Digestive System
1. teeth
2. epiglottis
3. liver
4. Gall bladder
5. Common bile
duct
6. Large
intestine
7. appendix
8. Salivary
glands
9. tongue
10. esophagus
11. stomach
12. duodenum
13. pancreas
14. Small
intestine
15. Rectum/
anus
• Digestion is a complicated process that
involves
1. Ingestion - process of taking food into the
digestive system so that it may be digested.
2. propulsion – movement of food along the
digestive tract
3. digestion- the breakdown of food (either
chemically or mechanically) in order to utilize
nutrients
4. Absorption of nutrients
5. Elimination of fecal matter
Oral Cavity/Mouth
• Includes both mechanical and chemical
transformations
• The tongue and teeth work together, breaking food
apart and pushing it around.
• The resulting mixture is called the bolus
• Saliva pours into the mouth from salivary glands to
begin digesting food, softening and lubricating it on
its way.
• The tongue pushes against the roof of the mouth as
you swallow, helping push food down the food tube
(esophagus).
Teeth
• Incisors – CUT
food
• Canines – TEAR &
SHRED food
• Premolars &
Molars – CRUSH &
GRIND food
Esophagus
• is about 10 inches long in an
adult.
• It lies behind your windpipe
(trachea) and is flattened
when empty.
• As you swallow, you stop breathing for a moment.
• A trapdoor called the epiglottis automatically closes the
opening to your airway and lungs, and the soft palate at the
back of the roof of your mouth swings up to shut off the
passage to your nose.
• If you swallow too fast, the epiglottis may not have time to
close, causing you to cough to clear out any food that might
enter the trachea.
• The muscles in the esophagus ripple to push the food into
the stomach using a movement called peristaltism.
Stomach
• Contains gastric juices made of
hydrochloric acid and the enzyme
pepsin are released to break down
protein in your food.
• These acids are strong enough to
eat through the wall of the stomach.
• Normally, these acids are not manufactured until food is in
the stomach and a protective mucus coats the stomach.
• Like a balloon, the stomach expands with food. The
muscles which surround it begin to churn the food back
and forth.
• Carbohydrates move out first and then
proteins. Fats are the last to leave the
stomach. Some food may remain in the
stomach for two to five hours.
• The food is now called chyme; it is a thick
liquid. The chyme squeezes into the
Duodenum (1st part of the small intestine).
Small Intestine
• Duodenum, the first 10 inches of the small intestine
where the digestive process will be completed by other
juices.
• The following organs are found around the intestine and
release digestive substances to aid digestion:
– The pancreas -- pancreatic juice
– The liver – bile
• Pancreatic juices and bile flow into the duodenum
through the bile duct and mix with the intestinal juice to
complete digestion
• Small Intestine now has the completely
digested food and it has been changed to
nutrients which can now be absorbed through
tiny fingers (villi) that line the walls of the
small intestine.
• Tiny blood vessels are inside the villi. They
take in the vitamins, minerals, and other
nutrients and carry them to all parts of the
body through the blood systems.
• The journey through the small intestine may
take four to eight hours.
• What remains undigested passes into the
large intestine.
Large Intestine
• Large Intestine where food
spends 10 to 12 hours
losing large quantities of
water and nutrients.
• At the end, the solution is
fed on by a colony of
bacteria which decay the
remains (feces).
• The feces are brown because they contain dead
blood cells.
• What is left of your meal passes to the rectum,
ready to leave the body through the opening called
the anus.
• The entire journey lasts about 15 to 48 hours.
The Liver
• An organ in the upper abdomen that aids in digestion
and removes waste products and worn-out cells from the
blood.
• Bile is made by the liver and stored in the gall bladder.
Bile works like a detergent to emulsify (soften) fats so
they can be dissolved in water and absorbed into the
body.
– Also neutralizes acids in partly digested food.
• The liver is the largest solid organ in the body.
• The liver has many functions. Some are:
1. to produce substances that helps to break down
fats
2. convert glucose to glycogen
3. produce urea (the main substance of urine),
4. make certain amino acids (the building blocks of
proteins)
5. filter harmful substances from the blood (such as
alcohol & drugs)
6. storage of vitamins and minerals
7. maintain a proper level or glucose in the blood
8. producing cholesterol.
The Pancreas
• The pancreas is a glandular organ that secretes
(releases) digestive enzymes and hormones. In
humans, the pancreas is a yellowish organ.
• the pancreas produces pancreatic juice to digest
carbohydrates, proteins, and fats.
• The pancreas lies beneath the stomach and is
connected to the small intestine at the duodenum.
• The pancreas produces the body's most
important enzymes. The enzymes are
designed to digest foods and break down
starches.
• also produces the hormone insulin and
secretes it into the bloodstream in order to
regulate the body's glucose or sugar level.
• The pancreas also helps neutralize chyme and
helps break down proteins, fats and starch.
• If the pancreas is not working properly to
neutralize chyme and break down proteins,
fats and starch, starvation may occur.
The Gall Bladder
•
•
•
•
The gallbladder is a small pear-shaped organ.
The gallbladder is connected to the liver by a duct.
The function of the gallbladder is to store bile.
A muscular valve in the common bile duct opens,
and the bile flows from the gallbladder into the
duodenum (part of the small intestine).
Chemical Transformations
Digestive glands
• A gland is an organ or group of cells that
produces secretions
• Secretions are chemical substances (such as
hormones) or liquids (such as sweat or
maternal milk) that have different functions in
the body
• Digestive glands secrete substances that aid in
the digestion of food
Digestive Glands and Secretions
Digestive
Glands
Location
Targets
Salivary glands Saliva
Mouth
Starch (complex carbs)
Gastric glands
Gastric juice
Stomach
proteins
Intestinal
Glands
Intestinal juice Small
intestine
Pancreas
Pancreatic
juice
Bile
Liver
Secretions
Small
intestine
Small
Intestine
Proteins, carbs,fats
Proteins, carbs,fats
fats
Chemical Transformations
• In a chemical transformation, the bonds of
complex molecules are broken, which gives
new more simple substances
Type of Nutrient
Complex Molecules (example)
Simple Molecules
(example)
Carbohydrate
Startch
Fats
Proteins
glucose
triglyceride
Enzymes
Glycerol and fatty acids
Amino acids