1. Mechanical vs. Chemical Digestion

2. Mechanical Digestion
Larger pieces of food get broken down into smaller pieces while being prepared for chemical digestion; this process starts in the mouth and continues into the stomach. 
Occurs in the following locations:
1. Mouth via Mastication by teeth, tongue and palates
2. Esophagus via Peristalsis - the wave like contractions move food through the system
3. Stomach via the muscular churning action of stomach
4. Small Intestine via the Emulsification (breakdown) of Fats

3. Why do we need Mechanical Digestion?
Mastication (chewing) begins the process of breaking down food into nutrients.
chewing creates smaller pieces are more readily digested through chemical digestion
Movement of substance through digestive tract
Peristalsis moves the food through the rest of the digestive tract
Absorption the nutrients that come from food in the SI NOTE: Mechanical digestion only deals with the physical breakdown of substances

4. Chemical Digestion
Involves the breaking down large, insoluble molecules into small, soluble ones.
Enzymes speed up the process and work efficiently at body temperature and at a suitable pH level
Chemical Digestion happens
Mouth
Stomach
Small Intestine

5. Chemical Digestion
Lubricants – Mucus found throughout our digestive system (saliva, stomach, SI) plays a major role in lubricating food as it passes through the digestive system.
Secretions – a substance produced by a gland or tissue and released into the organism for special use by the organism or for excretion
Examples: digestive juices, hormones, and perspiration

6. Chemical Digestive Enzymes
The Salivary Glands, Gastric Glands, Liver, Gallbladder and Pancreas all play different roles in chemical digestion:
Enzymes secreted from these sources, break down large food molecules by the process of hydrolysis
HYDROLYSIS
The process by which a water molecule is
added at the site where a bond is broken
This in turn breaks down the molecules into
smaller molecules (easier to digest)

7. Chemical Digestive Enzymes

8. Chemical Digestive Enzymes
1. Mouth: salivary glands produce the enzyme salivary amylase which breaks down starch (Glucose) into maltose.
2. Stomach: is lined with Gastric glands
Secrete mL of gastric juice each meal
Stomach has a pH of >2, which helps break down food and kill bacteria.
PARIETAL CELLS
Secrete Hydrochloric Acid (HCl)
GASTRIC LIPASE
From Chief Cells, speeds up digestion
CHIEF CELLS
Pepsinogen  Pepsin
(protein  peptides)
MUCUS SECRETING CELLS
Protective Mucus coating of stomach lining

9. *Note: Lactose intolerance results from a lack of the enzyme lactose.*
Chemical Digestion
3. Small Intestine: Final digestion of Proteins and Carbohydrates.
Fats begin to break down (be Emulsified)
Villi cells produce enzymes that complete digestion of peptides and sugars.
*Note: Lactose intolerance results from a lack of the enzyme lactose.*
Enzymes
Break Down
Results
Maltase
 Maltose
2 Glucose
Lactase
 Lactose
1 Glucose & 1 Galactose 
Sucrase
 Sucrose
1 Glucose & 1 Fructose 
Peptidase
 Tripeptide
Dipeptide & 1 Amino Acid
Nuclease
 Nucleic Acid
Nucleotides

10. Chemical Digestion
3. Small Intestine: Final digestion of Proteins and Carbohydrates.
INTESTINAL JUICES
Intestinal juice contains the following substances: water, mucin and enzymes.
The glands that secrete intestinal juice are called the “CRYPTS OF LIEBERKUHN”.
These glands are located at the base of the villi that line the SI.

11. Chemical Digestion
3. Small Intestine: Final digestion of Proteins and Carbohydrates.
PANCREATIC JUICES
Pancreatic juice contains water, mucin, sodium bicarbonate and enzymes.
Pancreatic juice is produced by and released from the pancreas and flows by way of a tube called the pancreatic duct into the duodenum.
The Sodium Bicarbonate that is present in pancreatic juice is important in that it acts as a buffer to change the pH of the chyme from 2 to a pH of 8.

12. Absorption
A very important part of the digestive process as it allows digested food to be transferred to the bloodstream and transported to cells in the body.
Most absorption occurs in the small intestine.
Villi and micro villi greatly increase the surface area.
Absorption through the intestinal walls occurs by ________________ and ____________________.
Fat, however, enter the _________________ (vessel) which is part of the lymphatic system and takes the fat to fat tissue where it is stored.