Download The Digestive System - Willoughby

The Digestive
System
How long is your digestive
system?
Digestive System
•30 Feet Long
•Why does the Digestive
System have to be so
long?
6 Functions of the Digestive System
1. Ingestion:
–
occurs when materials enter digestive tract via
the mouth
2. Mechanical processing:
–
–
crushing and shearing
makes materials easier to propel along digestive
tract
3. Digestion:
–
–
–
is the chemical breakdown of food
into small organic fragments
for absorption by the body
4. Secretion:
–
–
–
is the release of water, acids, and enzymes
by the digestive tract
by the digestive organs
5. Absorption:
–
movement of organic substrates, electrolytes, vitamins,
and water into the bloodstream.
6. Excretion:
–
removal of waste products from body fluids
Digestion
• Like a car: Engine changes
stored energy (gasoline)
into a form of energy that
makes the car move.
• Fats
• Carbohydrates
• Proteins
Digestion starts in the mouth
• Teeth cut & grind food into small pieces.
(Mechanical Breakdown)
• Why is this important?
• Lubrication:
– Salivary glands give off saliva
– Moisten & soften foods (Bolus)
• Limited digestion:
– of carbohydrates and lipids
Salivary Glands
• Produce 1.0–1.5 liters of saliva each day:
Saliva
• 99.4% water
• 0.6% includes:
– electrolytes (Na+, Cl—)
– Antibodies (?)
– enzymes
The Esophagus
• Involuntary muscles push food towards
stomach (Peristalsis)
• Moves a bolus along the length of the
digestive tract.
Peristalsis
Functions of the Stomach
1. Churns food
2. Mechanical breakdown of ingested
food by mixing with gastric juices
(HCL)
3. Food in stomach (CHYME)
The Stomach
Figure 24–12a
Segments of the Small Intestine
Figure 24–16
The Small Intestine
• CHYME (broken down food and gastric juices)
enter the Small Intestines
• Small Intestines play key role in digestion and
absorption of nutrients
• 90% of nutrient absorption occurs in the small
intestine
• Villi absorb the nutrients into the bloodstream
Intestinal Villi
• A series of
fingerlike
projections:
– In the small
intestine
• Absorbs fats,
carbohydrates and
proteins into the
bloodstream
The Digestive Organs
• Produce enzymes that breakdown
carbohydrates, fats and proteins
so they can be absorbed into the
bloodstream.
• Liver
• Pancreas
• Gallbladder
LIVER
• Largest organ inside the body
• Produces BILE that breaks down fats
Pancreas
• Produces chemicals that break
down carbohydrates & proteins
The Gallbladder
• Is a pear-shaped, muscular sac
• Stores the bile after it’s produced by the liver
• Increased fat in diet = more bile produced=
increased chance of Gallstones.
The Large Intestine
• Excretion:
Elimination of liquid
waste
• Kidneys: filter waste
from blood
• Urine passes to the
bladder
Figure 24–23
Large Intestine (Solid Waste)
• Undigested food passes into (LI)
• Colon lining absorbs all the liquid it
can. ( absorption)
• Waste leaves the body through the
ANUS.
Disorders Of The Digestive System
• Acid Reflux
Stomach Ulcer
Gallstones