The digestive system is 30 feet long to allow for thorough breakdown and absorption of nutrients. It has 6 main functions: ingestion, mechanical and chemical digestion, secretion of enzymes, absorption of nutrients, and excretion of waste. Digestion begins in the mouth and involves breakdown by teeth, saliva, and the esophagus. The stomach further breaks down food into a liquid. The small intestine plays a key role in nutrient absorption through fingerlike villi. The liver, pancreas, and gallbladder produce enzymes and bile to break down carbohydrates, proteins, and fats. The large intestine absorbs water before waste is excreted. Common digestive disorders include acid reflux, ulcers, and gallstones.

1. The Digestive
System

2. How long is your digestive
system?

3. Digestive System
•30 Feet Long
•Why does the Digestive
System have to be so
long?

4. 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

5. 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

6. Digestion
• Like a car: Engine changes
stored energy (gasoline)
into a form of energy that
makes the car move.
• Fats
• Carbohydrates
• Proteins

7. 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

8. Salivary Glands
• Produce 1.0–1.5 liters of saliva each day:
Saliva
• 99.4% water
• 0.6% includes:
– electrolytes (Na+
, Cl—
)
– Antibodies (?)
– enzymes

9. The Esophagus
• Involuntary muscles push food towards
stomach (Peristalsis)
• Moves a bolus along the length of the
digestive tract.

10. Peristalsis

11. Functions of the Stomach
1. Churns food
2. Mechanical breakdown of ingested
food by mixing with gastric juices
(HCL)
3. Food in stomach (CHYME)

12. The Stomach
Figure 24–12a

13. Segments of the Small Intestine
Figure 24–16

14. 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

15. Intestinal Villi
• A series of
fingerlike
projections:
– In the small
intestine
• Absorbs fats,
carbohydrates and
proteins into the
bloodstream

16. The Digestive Organs
• Produce enzymes that breakdown
carbohydrates, fats and proteins
so they can be absorbed into the
bloodstream.
• Liver
• Pancreas
• Gallbladder

17. LIVER
• Largest organ inside the body
• Produces BILE that breaks down fats

18. Pancreas
• Produces chemicals that break
down carbohydrates & proteins

19. 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.

20. The Large Intestine
Figure 24–23
• Excretion:
Elimination of liquid
waste
• Kidneys: filter waste
from blood
• Urine passes to the
bladder

21. 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.

22. Disorders Of The Digestive System
• Acid Reflux

23. Stomach Ulcer

24. Gallstones