1. DIGESTION
SBI 3C: NOVEMBER 2010

2. DIAGRAM OF DIGESTIVE SYSTEM:
Mouth
Esophagus
Liver
Stomach
Pancreas
Gallbladder
Small Intestine
Large Intestine
Rectum
Appendix
Anus

3. STAGES OF DIGESTION: INGESTION DIGESTION ABSORPTION EGESTION
Taking in nutrients
DIGESTION
Breakdown of macromolecules into smaller components by physical and chemical means
ABSORPTION
Absorbing digested molecules
EGESTION
Removal of waste food materials from the body

4. STEP 1: INGESTION Teeth chew the food Saliva moistens
Enzyme in saliva (amylase) breaks down carbs
Muscular tongue pushes food back to pharynx

5. STEP 1: INGESTION
Epiglottis – flap covers trachea so food doesn’t get in
Food stretches walls of esophagus and moves downward through waves of contractions called peristalsis
Video

6. STEP 2: DIGESTION Stomach:
Food moves in and out through sphincters (circular muscles)
Stomach contracts and relaxes to churn the food
Stomach produces gastric juices to breakdown food.
Hydrochloric acid:
Breaks down food
Destroys foreign organisms (bacteria) in food
Pepsin:
Enzyme
Breaks down proteins into polypeptides

7. STEP 2: DIGESTION Mucus: Protects stomach lining from acid
Some absorption of water, medicine and alcohol here

8. STEP 2: DIGESTION Small Intestine:
Up to 7m in length, 2.5cm in diameter
The small intestine is divided into 3 parts: the duodenum, the jejunum, and the ileum
Primary site of nutrient absorption to the blood

9. STEP 2: DIGESTION
Secretes peptidase which completes digestion of proteins
Only the small intestine can absorb lipids (fats), carbohydrates, and amino acids (from proteins)
Contains capillaries in the villi that absorbs the nutrients form the small intestine.

10. ACCESSORY ORGANS
The liver, pancreas and gallbladder are all accessory organs that are connected to the small intestine and help with the digestion of other nutrients.

11. ACCESSORY ORGAN: PANCREAS
Secretes digestive enzymes trypsin, lipase, and amylase into the duodenum to break down carbohydrates, proteins and fats
Neutralizes acidic stomach contents (called chyme) before they enter the small intestine

12. ACCESSORY ORGAN: LIVER
Weighs between g, 2-5% of adult human body weight
Cleans and detoxifies blood
Stores carbohydrates, fats, vitamins and minerals
Makes bile and sends it to the gallbladder.

13. ACCESSORY ORGAN: GALLBLADDER
Stores and concentrates bile from the liver and delivers it to the duodenum to break down fats
Not an essential organ.
Gallbladder is sometimes removed because of gallstones

14. STEP 3: ABSORPTION
Most absorption of nutrients takes place in small intestine
Small intestine is lined with villi:
Finger-like projections that increase surface area for absorption

15. STEP 3: ABSORPTION
The capillaries within the villi absorb the nutrients from the intestine and deliver it to other tissues through the blood.

16. STEP 4: ELIMINATION Large intestine is 1.5 meters in length
The large intestine reabsorbs fluids
Harmless bacteria live here producing vitamin K and B
Any undigested food that remains is called feces
Fecal matter is stored here before elimination through the anus