Download Human Digestive System

Human Digestive System
Two types of food components
Nutrients:
substances that can be digested (if necessary),
absorbed and used within the body
Roughage (fiber):
a) substances that cannot be digested or absorbed
b) primarily cellulose from
plant cell walls
Roughage Benefits
1) stimulates muscle contractions (peristalsis)
that move food through the digestive system
2) prevent constipation
3) reduce risk of colon cancer
4) reduce the amount of cholesterol in the blood
5) can help you lose weight
(suppress appetite without adding calories)
Sources of roughage
1) Fruits, vegetables, grains and other “natural” foods
that come from plants are good sources
2) “Processed” foods from plant sources often have little
or no roughage
Example:
table sugar, “instant rice”, cereals that are not “whole
grain”, snacks like chips, cheese doodles, candy bars
etc.
3) “low carbohydrate diets” may contain too little fiber
Three Uses for Nutrients
1) Energy Sources
2) Structural Material for growth and
tissue maintenance
3) Regulation of Body Functions
Six Important Nutrients
1)
2)
3)
4)
5)
6)
Water
Minerals
Vitamins
Proteins
Carbohydrates
Lipids (fats)
1. Water
1) most abundant substance in any organism
2) importance in human body:
a) solvent & transport medium
b) stimulates chemical reactions
c) regulation of body temperature
d) required for digestion (hydrolysis)
e) dilution of toxic waste products
f) helps immune system
Problems associated with
dehydration
1)
2)
3)
4)
5)
headaches
impairs immune system
increased thirst
lack of energy
hyperthermia (elevated body temp.)
How much fluid should you
drink each day
• 1. 9 liters of fluids
• 64 ounces (8 eight ounce glasses)
• Half gallon
Symptoms of Dehydration
• Thirst
• Dark Urine
• Dry mouth
2. Minerals
Simple inorganic substances like:
•
Calcium (Ca)
•
•
Phosphorous(P)
Iron (Fe)
•
•
•
Sodium (Na)
Potassium (K)
Iodine (I)
3. Vitamins
a) Small organic substances which regulate
body processes
b) Most are “coenzymes” (they assist
enzymes in controlling reactions)
Proteins
1. Used for:
a) structural material
b) enzymes (catalyze reactions)
c) hormones (chemical messengers)
d) antibodies (fight disease)
2. Complete proteins:
a) contain all of the 8 essential amino acids that
must be in your diet.
b) proteins from animals are generally
complete
Carbohydrates
1. Sugars and starches
2. Primary source of energy
3. Should provide about 2/3 of the calories in
your diet
Lipids (fats, oils, wax)
Used for:
a) energy storage
(contain about twice the calories per
gram of carbohydrates or protein)
b) structural material (cell membranes)
c) insulation
d) padding
e) production of steroid hormones
Saturated Fats vs. Unsaturated
1. come mainly from
animals
1. come mainly from
plants
2. easily converted to
cholesterol
2. less likely to raise
cholesterol
3. increase chances of:
heart attack, high
blood pressure and
stroke
3. fewer health risks
Problems with American Diet
1. Too many:
calories, fats, simple sugars, saturated
fats and sodium
2. Not enough:
variety, calcium, roughage, fruits &
vegetables
Problems Associated with
Obesity
1. Cardiovascular diseases
–
Heart disease, high blood pressure, stroke
2. Arthritis
3. Diabetes
4. Increased Cancer risk
Energy Needs
1. young males need about 2800 calories per day
2. young females need about 2200 calories per day
decrease with age
3. increase with physical activity
Eating Disorders
1. Anorexia Nervosa
a) excessive concern about gaining weight
b) victims starve themselves
2. Bulimia (binge & purge syndrome)
overeating followed by self induced
vomiting, fasting or use of laxatives
Digestive Terms
1. Ingestion
to take in food
2. Egestion
to remove undigested materials from the digestive
system (egestion is not excretion)
3. Digestion
the breakdown of food so that it can be absorbed
4. Peristalsis
muscle contractions that move food through
digestive organs
Peristalsis
peristalsis movie
Two Types of Digestion
1. Mechanical
a) physical breakdown into smaller pieces
b) chewing, grinding and dissolving
increases the surface area for faster
chemical digestion
2. Chemical Digestion
a) “hydrolysis” of large molecules into
their building blocks by enzymes
b) Large molecule + H2O Small
Molecules
c) Water, minerals and vitamins do not
require chemical digestion
Large Organic
Molecule
(polymer)
Protein
(polypeptide)
Polysaccharide
(starch)
Lipids
(fats, oils, wax)
Building block
(monomer)
Name of
digestive
enyzme
Large Organic
Molecule
End product of
digestion
Name of
digestive
enzyme
Protein
Amino acids
Protease and
pepsin
Starch/ carbs
simple
sugars/glucose
Amylase and
ptyalin
Lipids
Glycerol and
(fats, oils, wax) fatty acids
lipases
Human Digestive Organs
Two types of digestive organs
1. Organs of the Alimentary Canal (GI Tract)
form the passageway that food travels through
include: mouth
pharynx
esophagus
stomach
small intestine
large intestine (colon)
anus
2. Accessory Organs
Secrete fluids into the alimentary canal
Include:
a) salivary glands
b) liver
c) gall bladder
d) pancreas
The Mouth
Chewing is a form of :
mechanical digestion
Saliva:
a) helps food dissolve so it can
be tasted
b) contains pytalin (salivary
amylase), which:
- converts starch into
sugar ( chem digestion)
Tongue:
a) aids in swallowing
b) contains 4 types of taste buds:
sweet, sour, bitter & salty
Pharynx
a) the area behind your mouth
b) during swallowing, food is kept out of
the trachea (windpipe) by the:
epiglottis
How can you assist someone who has food
caught in the pharynx?
Esophagus
a) Carries food from the
pharynx to the stomach
b) Involves wave like muscle
contractions called
peristalsis
c) A ring like muscle called
the lower esophageal
sphincter:
– keeps stomach acid out
of the esophagus
d) Heartburn: irritation of
the esophagus by stomach
acid
The Stomach
a) J shaped sac on the left
side of your body
b) Contains 3 layers of
muscle which grind food
and mix it with “gastric
juice”
c) Pyloric sphincter keeps
food out of small intestine
until it’s converted to a
liquid
Gastric Juice
Fluid secreted by stomach
which contains:
a) pepsin (gastric protease)
a protein digesting enzyme
b) hydrochloric acid (HCl)
-kills most bacteria
-helps food dissolve
-provides the low pH
-that pepsin needs
c) Peptic ulcer : an irritation of
stomach or small intestine
caused by gastric juice
The Small Intestine
1. 6.5 meters (20ft) long and 2.5 cm (1 in.) thick
2. Most important digestive organ
3. Only organ where all types of nutrients can be
digested
4. Over 90% of nutrient absorption occurs in SI
5. Secretes a basic fluid called intestinal juice which
neutralizes stomach acid
6. Produces hormones that signal accessory organs to
release their fluids
The Digestive System Page
Ideal pH’s for digestion:
a) in stomach it’s about 3
(provided by Hydrochloric Acid)
b) in small intestine it’s 8-9
(provided by intestinal & pancreatic juice)
Villi
a) bumps in small intestine that increase surface area
for absorption
b) contain digestive enzymes on their surface
c) most nutrients are absorbed into capillaries w/in villi
d) fats and non-polar vitamins are absorbed into small
lymph vessels called “lacteals”
Large Intestine
(Colon)
a) includes:
ascending,transverse &
descending colon, rectum
and anus
b) no digestive enzymes
c) absorbs water from wastes
d) eliminates wastes (feces)
which consist of roughage &
bacteria
e) E. coli bacteria live in colon,
aid digestion and produce
vitamins
f) appendix –vestigial sac near
ascending colon
Accessory organs
(Organs that Secrete Into SI)
1. Pancreas
-secretes all kinds of
digestive enzymes
-pancreatic juice is
basic (high pH)
Secretes insulin to regulate
blood sugar levels
2. Liver (largest internal organ)
a) secretes “bile” into SI
b) bile makes lipids dissolve in water, a process
called emulsification
c) emulsification allows fats to mix with lipases
and is a form of mechanical digestion
3. Gall Bladder
a) stores bile that was produced in the liver
b) gallstones: crystallized deposits of
cholesterol which can block the flow of
bile
Other Functions of Liver
1) Produce glycogen from glucose and store it
when blood sugar is high
2) Breakdown glycogen to release glucose when
blood sugar is low
3) Store vitamins and iron
4) Remove old red blood cells
5) Destroy harmful substances in bloodstream
6) Break down alcohol (about 1 oz. per hour)
Disorders of the Digestive system
Liver Disorders
1. Cirrhosis- liver damage common in alcoholics
2. Hepatitis – inflammation of liver
a) usually caused by viral infection (A,B&C)or
alcohol
b) A – no lasting damage (4-6 week infection)
results from fecal contamination
c) B & C – more serious, can be transmitted
sexually and by blood, saliva and tears,
You can be vaccinated for Hepatitis B
3. Liver Cancer
a) often deadly
b) much more likely if you have cirrhosis or hepatitis
B or C
Liver Diseases
Disorders of Large Intestine
Constipation (irregularity)
a) difficulty in removing feces
b) caused by feces being in colon too long and too
much water reabsorbed
Diarrhea
a) frequent elimination of watery feces
b) quick passage prevents adequate water absorption
c) can cause serious dehydration
Appendicitis
inflammation of appendix, usually because
of infection
Colon Cancer
a) #2 cause of cancer deaths
b) linked to low-fiber diet