Chemical Digestion and accessory organs

1. Digestive System II: Accessory
Organs, Digestion and Nutrition
ATS Unit 6

2. Learning Targets
• Identify accessory organs and their
functions in the digestive system.
• Discuss the functions of key enzymes and
macronutrients as they interact in the
process of digestion.

3. Review of Macronutrients
• We need:
– Carbohydrates
– Proteins
– Lipids
• However, they are not absorbable in the
form we find them in food.
– Digestion is the physical and chemical
process of creating absorbable nutrients.

4. In the Beginning…
• We intake food through our oral cavities
(mouths).
– Toungue and teeth mash the food to prepare
it for digestion.
– Salivary glands secrete fluid that begins the
digestive process.
• A key ingredient in saliva is amylase, a digestive
enzyme that begins the breakdown of sugars
(carbs).

5. Chemistry in the Stomach
• Gastric Juices are very acidic and contain
various chemicals:
– Gastrin promotes production of Hydrochloric
Acid
– Hydrochloric acid is made by the parietal, also
intrinsic factor (b12 absorption)
– Pepsin is made by Chief cells and begins protein
digestion.
– Rennin is found in higher levels in infants and
children, and helps digest milk protein.
– Mucous is produced by many mucous cells to
protect the stomach lining from the acid.

6. Chemistry in the Small Intestine
• There are many enzymes and other chemicals
active that help with the complicated process of
digestion and absorption.
– Secretin and Cholecystokinin stimulate the pancreas
liver and gallbladder to release there enzymes.
– Pancreas releases Protease, Amylase and Lipase to
break down larger molecules of proteins, carbs and
fats. It also releases bicarb to neutralize the
stomach acid.
– Liver produces bile which emulsifies fats.
– Intestines produce enzymes to breakdown sugars
into simple sugars for absorption.

7. The Breakdown of Macronutrients

8. The Pancreas
• Both an exocrine gland for the digestive
system and and endocrine gland that
produces hormones.
– Three portions (head, body and tail)
– Lives just under the stomach
– Most of the pancreas works to create the
digestive enzymes and bicarbonate (Acini and
Duct Cells).
– Islets of Langerhans serve the endocrine
purpose.

9. The Liver and Gallbladder
• The liver a large vascular organ located under the
right side of the diaphragm. It has a right and left
lobe.
– Creates bile which contains bilirubin.
– Creates and stores glycogen
– Detoxifies harmful substances
– Makes blood proteins for clotting.
– Processes waste from protein metabolism (urea)
– Store vitamins
– Breaks down hormones and worn out RBCs.
• The gallbladder sits under the liver, is connected to
the hepatic and common bile duct and is just a
storage area for bile.

10. After Absorption
• The simplified molecules from the
proteins, fats, carbohydrates, vitamins
and minerals are absorbed by selective,
facilitates, or passive absorption into the
capillaries into eh intestinal walls. They
then are circulated around the body and
used where they are needed.