Digestion is the breakdown of chemicals
This allows a large molecules to become nutrients that can be absorbed more readily.
Absorption is done through cells and into the blood stream
Ingestion – introduces food to the digestive process
Mechanical breakdown:
- Force from teeth and tongue to breakdown food into smaller particles
- Swallowing
- Peristalsis – smooth muscle movement
Chemical breakdown:
- The reactive force to breakdown molecules into simple structures
- Enzymes
- Saliva
- Acids
- Bile
- Water
Peptides become Amino Acids – Breakdown begins in the stomach but is further broken down in the small intestines.
Enzymes from the pancreas can cut protein into smaller peptides
Lipids (fats ) become Fatty acids and Glycerol.
Pancreatic lipase with the help of bile, together they cause the breakdown of triglycerides into the free fatty acids.
Carbohydrates become sugars such as glucose.
Pancreatic amylase breaks carbohydrates into complex sugars. Then the enzymes in the small intestines break the complex sugars into simple sugars.
4 main hormones involved in regulation of the digestive system
1.) Gastrin – found in stomach and stimulates gastric glands to secrete “pepsinogen” and “hydrochloric acid“.
2.) Secretin - found in the duodenum and signals release of “sodium bicarbonate” in pancreas which causes the release of “bile” from the liver
3.) Cholecystokinin (CCK) found in duodenum and stimulates release of digestive enzymes in pancreas and causes release of “bile” from gallbladder.
4.) Gastric inhibitory peptide (GIP) found in duodenum and causes decrease activity of stomach. Also stimulates the release of insulin from pancreas
Absorption
- Addition of nutrients to cells and blood stream
- Diffusion
- Osmosis
- Active Transport
Egestion:
- The removal of waste and undigested material
- Done through Defecation
Categories of Human digestion
1.) Cephalic phase
– Saliva from mouth begins breakdown
- Taste and smells stimulate release gastric secretion
- Starches are broken down here
2.) Gastric phase
- Stimulated by expansion of stomach with food particles
- pH may change
- Gastric juices are released
3.) Intestinal phase
– Movement of food particles through intestines
- Will end in Defecation
- Some absorption occurs
- Active transport and enzymes are essential
Organs involved:
- Stomach