Human Digestion
Nutrition
•
process by which organisms obtain and utilize their food
2 Parts:
•
1. ingestion- process of taking food into the
digestive system so that it may be
hydrolized or digested.
•
2. digestion- the breakdown of food (either
chemically or mechanically) in order to
utilize nutrients
Terms to know:
• Autotrophs- make their own food.
• Heterotrophs- get food from other
sources.
Nutrients
• Micronutrients- vitamins, minerals, & water
• Macronutrients- proteins, lipids,
carbohydrates, etc…
Mouth
• Chemical and
mechanical
digestion.
• Food is chewed
(masticated)
mechanically.
• A bolus (lump) is
formed with saliva
and the tongue.
Which type of digestion is the
following?
1. Chewing a saltine? 2. Saliva breaking the saltine down into molecules of
glucose? 3. Your tongue breaking pieces of a hamburger apart?
4. Pepsin (an enzyme) in your stomach breaking the
hamburger into amino acids?
GI (gastrointestinal) tract = alimentary canal
Pharynx
• The back of the
throat.
• Larynx- passage
for air, closes
when we
swallow.
• Is approximately
15cm long.
Digestive Glands
• Groups of
specialized
secretory cells.
• Found in the
lining of the
alimentary canal
or accessory
organs.
Peristalsis
• series of involuntary
wave-like muscle
contractions which
move food along the
digestive tract
Stomach
• Food is temporarily
stored here.
• Gastric juices are
secreted.
• Has layers of
muscle that line the
inside.
• Mechanically and
chemically breaks
down food.
Gastric Juices
• Secreted by the
stomach.
• Acidic (pH 1.5-2.5)
(HCl).
• Pepsin- an enzyme that
breaks down large
proteins into amino
acids.
• Food is further broken
down into a thin liquid
called chyme.
Accessory Organs
• Pancreas
• Gall Bladder
• Spleen
Gall bladder
• Pouch structure located near the liver
which concentrates and stores bile
• Bile duct – a long tube that carries BILE.
The top half of the common bile duct is
associated with the liver, while the bottom
half of the common bile duct is associated
with the pancreas, through which it passes
on its way to the intestine.
BILE
• Bile emulsifies lipids (physically breaks
apart FATS)
• Bile is a bitter, greenish-yellow alkaline
fluid, stored in the gallbladder between
meals and upon eating is discharged into
the duodenum where it aids the process of
digestion.
Pancreas
• An organ which secretes both digestive
enzymes (exocrine) and hormones (endocrine)
• ** Pancreatic juice digests all major nutrient
types.
• Nearly all digestion occurs in the small intestine
& all digestion is completed in the SI.
Small Intestine
• Most chemical
digestion takes place
here.
• Simple sugars and
proteins are absorbed
into the inner lining.
• Fatty acids and
glycerol go to lymphatic
system.
• Lined with villi, which
increase surface area for
absorption, one cell
thick.
Absorption in the SI
•
Much absorption is thought to occur directly through the wall
without the need for special adaptations
•
Almost 90% of our daily fluid intake is absorbed in the small
intestine.
•
Villi - increase the surface area of the small intestines, thus
providing better absorption of materials
VILLI
Large Intestine
• Solid materials pass
through the large
intestine.
• These are undigestible
solids (fibers).
• Water is absorbed.
• Vitamins K and B are
reabsorbed with the
water.
• Rectum- solid wastes
exit the body.
Digestive Homeostasis Disorders
• ULCERS – erosion of the surface of the
alimentary canal generally associated
with some kind of irritant
Digestive Homeostasis Disorders
• CONSTIPATION – a
condition in which the large
intestine is emptied with
difficulty.
• Too much water is
reabsorbed and the solid
waste hardens
• Solution: Drink more water
eat more fiber.
Digestive Homeostasis
Disorders
• DIARRHEA – a gastrointestinal disturbance
characterized by decreased water
absorption and increased peristaltic activity
of the large intestine.
• This results in increased, multiple, watery
feces.
• This condition may result in severe
dehydration, especially in infants
Digestive Homeostasis
Disorders
• APPENDICITIS – an inflammation of
the appendix due to infection
• Common treatment is removal of the
appendix via surgery
Digestive Homeostasis
Disorders
• GALLSTONES – an accumulation of
hardened cholesterol and/or calcium
deposits in the gallbladder
• Can either be “passed” (OUCH!!) or
surgically removed
Digestive Homeostasis
Disorders
•
•
•
ANOREXIA NERVOSA - a psychological
condition where an individual thinks they
appear overweight and refuses to eat.
Weighs 85% or less than what is
developmentally expected for age and
height
Young girls do not begin to menstruate at
the appropriate age.
Digestive Homeostasis
Disorders
• HEART BURN – ACID from the
stomach backs up into the esophagus.
Nutrition
• Carbohydrates- main source of
energy. Starch and sugars are
carbohydrates.
• Monosaccharides- the
simplest carbohydrates
(Glucose).
• Disaccharides- the
combination of two simple
sugars ( Maltose).
Nutrition continued……
• Polysaccharides- long chains
of monosaccharides (simple
sugars) bonded together.
Starches are polysaccharides,
they are also found in Cellulose.
• Lipids-fats and oils. The
building blocks of lipids are fatty
acids and glycerol.
Proteins
• Are made up of Carbon,
Hydrogen, Oxygen, and
NITROGEN.
• Proteins are made up of amino
acids.
• Two amino acids bonded
together are called a dipeptide.
• Many amino acids bonded
together form a chain called a
polypeptide.
Enzymes
• Enzymes control chemical reactions.
• Enzymes are large complex protein
molecules.
• Enzymes are organic catalysts. They
either speed up or slow down a
chemical reaction.
• A coenzyme is the non-protein part of
an enzyme (usually vitamins).
• Enzyme function is controlled by
temperature, pH, and conc. of enzymes
and substrate.
Nucleic Acids
• Are very large molecules made up of
carbon, oxygen, nitrogen, and
phosphorus.
• Nucleotides are the building blocks of
nucleic acids.
• Nucleotides are made up of a
phosphate group, a sugar molecule,
nitrogen base.
pH Scale
• The pH scale measures
whether a solution is acid,
basic, or neutral.
• 0-6.9 is acid
• 7.1-14 is basic
• 7 is neutral
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