Download Digestion

Digestion
Digestive System
• Mouth – teeth, tongue, salivary glands
• Esophagus- muscular tube that contracts in
waves to move food into the stomach.
• Stomach – a muscular J-shaped organ
packed full of gastric glands
• Small Intestine – divided into three regions
1) duodenum 2) jejunum 3) ileum
• Large Intestine- consisting of the caecum,
colon, rectum, and anal canal.
Two Types of Digestion
• Mechanical Digestion – the initial stage of
physically breaking down food into smaller
more manageable pieces.
• Chemical Digestion – is the separation of
food into its molecular components by
chemical means.
Mechanical Digestion
• Begins in the mouth
with the teeth and
tongue manipulating
the food into
manageable sized
pieces
• Food is moved down
the esophagus in a
wave like movement
called Peristalsis.
• http://www.innerbody.com/anim/mouth.ht
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Mechanical Digestion
• For the rest of the
system Involuntary
muscle movements
grind food into smaller
pieces.
Chemical Digestion
• Chemical Digestion occurs simultaneously
with mechanical digestion.
• When food enters the mouth, saliva is
secreted by salivary glands to chemically
breakdown food and moisten the food for
an easy passage down the esophagus.
• Salivary amylase – is the enzyme to
breakdown starch and other complex
sugars into a more manageable sugar,
maltose (a double sugar).
Chemical cont.
• Food then travels
down the esophagus.
• Once in the stomach,
harsh hydrochloric
acid Pepsin – an
enzyme to breakdown
proteins into smaller
peptides, works to
chemically
breakdown food.
Small Intestine
• The area of enzymatic
breakdown of lipids
by Lipase and
carbohydrates by
carbohydrase.
• ALSO- major site of
absorption of
nutrients into the
blood stream
Small Intestine
Large Intestine
• Final stage of Digestion
• Point where water and electrolytes
(Sodium and Chloride) are re-absorbed
back into the body.
• Waste products at this point are mixed with
bacteria and mucus to form feces.
• http://www.whfoods.com/genpage.php?tna
me=faq&dbid=16#digestion
• http://www.cando.com/uci/ssi2002/digestivesystem.html
Chemical Digestion & Enzymes
Essential Nutrients
• There are basic raw materials organisms need to
make their own structures, perform functions,
and obtain energy for survival
• There are six (6) Essential Nutrients:
– Carbohydrates
– Proteins
– Vitamins
- Fats (Lipids)
- minerals
- water
• Our body functions best when we get the correct
portions satisfying a balanced diet.
Carbohydrates
• Consists of atoms of carbon, hydrogen and
oxygen (CHO). Carb’s are broken down to
simple sugars during digestion (glucose,
fructose, galactose).
– Main function is to provide a source of energy
– Excess carbohydrates are converted to fat or
glycogen and stored.
– Sources would be: sugar, rice, bread, pasta
etc…
Fats (Lipids)
• Are made up of fatty acids and glycerol
– Main functions include: providing a source of
energy, insulating the body from the cold, and
protecting the organs from injury.
– Used as the main component in building cell
membranes and some hormones.
– They are broken down to fatty acids and
glycerol by the digestive system
– Sources include: butter, meat, cheese, nuts,
eggs
Protein
• They are made up of individual amino
acids joined by peptide bonds forming
chains of peptides. (there are 8 essential
amino acids)
– Main functions include: cell growth and
repair, enzymes in your body are all proteins,
minor energy source.
– Sources include: meat, milk, poultry, fish,
eggs, etc…
Vitamins
• Our bodies require small amounts of these
in our diets. They act as coenzymes
(chemicals needed to make enzymes
function)
• Ex. Vitamin A, B, C, D, E, and K
• SEE TABLE 11.1 on Page 358
Minerals
• These are inorganic compounds that your
body needs in small amounts.
– Main functions include: helping to build bones
and cartilage, enabling certain chemical
reactions, and helping to maintain acid-base
balance within the body
Water
• The ‘life’ solvent.
• Most chemical reactions in the body
require water.
• Main source is food and water.
• Regardless of an organisms food source,
nutrients acquired by an organism must be
in a form that can readily pass through the
organisms cell membrane.
Chemical Digestion
• The chemical breakdown of food occurs ar
the molecular level where a water
molecules break the bonds of complex
compounds through the process of
hydrolysis.
• Hydrolysis does occur naturally but at too
slow of a rate. This is where enzymes
assist by speeding up the process.
Enzyme action
• Many enzymes end in ‘ase’, and act on a
single substrate (the item being broken
down), and are named using the subtrates
name. Lactase  lactose
Three Broad Classes
• Carbohydrases- breakdown carbohydrates
• Lipases – breakdown lipids
• Proteinases (Proteases) – breakdown
proteins
Function
• Enzymes are extremely specific for the job they
were designed to do.
– ‘Lock and key fit ‘ analogy
• Some work in acidic environments (pepsin),
while some like a neutral or alkaline
environment.
• High temperatures usually change the shape of
the ‘lock’ and prevent them from working.
• Some need coenzymes to function properly
(vitamins or minerals)
Overview
• Begin in the mouth where amylase breaks
starch down to a dissacharide.
• Gastric acid and activated pepsin in the
stomach begin to break down proteins.
Amylase continues until the low pH
destroys it.
• The chyme passes into the small intestine
where enzymes from the duodenum,
pancreas, and liver continue digestion.
Duodenum - busy place
• Secretions from the liver and pancreas are used for
digestion in the duodenum.
• The pancreas secretes digestive enzymes and stomach
acid-neutralizing bicarbonate. It neutralizes the chyme
(stopping the action of pepsin), and continues peptide
breakdown.
• The liver produces bile, which is stored in the gall
bladder. Bile salts emulsify (surround) fat droplets so
they can be absorbed by the intestine.
• Most absorption occurs in the ileum and jejeunum.
Liver and Gall Bladder
• The liver produces bile and helps to
detoxify of blood
• synthesis of blood proteins
• destruction of old erythrocytes
• storage of glucose as glycogen
• De-amination amino groups and ammonia.
(this produces urea, less toxic)
Glycogen-Glucose
• Low glucose levels in the blood cause
glucagon to stimulate breakdown of
glycogen into glucose.
• Insulin helps store glucose and glycogen in
the liver
• When no glucose or glycogen is available,
amino acids are converted into glucose in
the liver.
The Large Intestine what to do
with left overs!
• The large intestine produces an alkaline mucus
that neutralizes acids produced by bacterial
metabolism.
• Water, salts, and vitamins are absorbed, the
remaining contents in the lumen form feces
(mostly cellulose, bacteria, bilirubin).
• Bacteria in the large intestine, such as E. coli,
produce vitamins (including vitamin K) that
are absorbed.
Digestive Disorders
Overview
• Problems with the digestive system can range
from minor inconveniences (heartburn) to a
major impediment to a normal lifestyle (bleeding
ulcers)
• We will discuss the following 6 digestive
disorders.
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1. Ulcers
2. Gallstones
3. Ileitis
4. Colitis
5. Anorexia Nervosa
6. Bulimia Nervosa
Ulcers
• Are slow healing sores in the linings of
the stomach and intestines.
• Causes:
– Acids – Cause breakdown of mucus layer of stomach and
intestines.
– Heliobacter pylori – Acid resistant bacteria that causes
mucus production to stop.
– Lifestyle – Stress, smoking, alcohol/beverage consumption
• Cures/Treatments range from medications to reduce
acid production to an overall change in lifestyle.
Ulcers
Gallstones
• Hard masses that form in the gall bladder.
Cholesterol in the bile “precipitates” out as a solid
forming crystals.
• Causes:
– Obesity
– Alcohol
– Heredity
• Treatments:
– Ultrasound (busts up the gall stone so it can pass)
– Diet Changes (lower fat content diet – reduce
cholesterol)
– Surgery (Removal of gall bladder).
Gallstones
Ileitis
• Inflammation of the Ileum causing severe pain.
The inflammation causes the intestine to empty
often causing diarrhea.
• Causes:
– Relatively unknown
– Does run in families
• Treatments/Cures:
– There is no cure. Treatment includes drugs to reduce
swelling or surgical removal of affected area
Crohn’s & Colitis
• Inflammation and ulceration of the lining of the Colon,
Colitis affects the innermost lining of the colon, where
Crohn’s affects the entire thickness of the colon. Both
conditions can cause bleeding, diarrhea and abdominal
pain.
• Causes:
– Relatively unknown
– Does run in families
• Treatments/Cures:
– Again, no cure so treatment includes drugs to reduce
swelling and surgical removal of affected area
Anorexia Nervosa
• Eating disorder where a
person has a fear of gaining
weight so they go on very
restrictive diets.
• The person often loses
excessive amounts of weight
and has a lack of nutrients to
the cells of body.
Many complications
Bulimia Nervosa
• Eating disorder where a person has
episodes of binge eating followed by
“purging” through vomiting or taking
laxatives.
• This is very dangerous because it affects
several organs. Damage to heart, kidneys,
esophagus and teeth are common.