The digestive system Flashcards
Step 1: Mouth
-Salivary amylase breaks down starch into disaccharides (chemical digestion).
-Teeth chew food and push food against rugae (physical digestion).
-The tongue pushes the bolus to the back of the mouth where the bolus enters the esophagus.
Step 2: Esophagus
-Bolus Passes through the Esophageal Sphincter which only opens for food to stop stomach acid from coming up.
-Bolus moves through here partly by gravity but mostly by peristalsis: wavelike series of muscle contraction/relaxations
Step 3: Stomach
-Stomach acid breaks down protein in bolus using pepsin.
-Bolus combines with gastric fluids to make chyme.
-Pepsinogen (inactive) is converted into pepsin (active) bcuz of hydrochloric acid
Step 4: Small Intestine
-Divided into three sections: Duodenum, ileum, jejunum
-Main function is to digest macromolecules and use enzymes from the pancreas to do so.
-Enzymes here: maltase, lactase, sucrase and enterokinase
-Nutrients broken into monomers and absorbed through bloodstream.
Villi vs Capillaries
-Villi (lymphatic system): absorb fats, move electrolytes by diffusion, move water by osmosis.
-Capillaries: absorb all other nutrients (circulatory system)
Step 5: Pancreas
-Soft tubular gland behind stomach
-Connected to duodenum
-has exocrine and endocrine functions
Exocrine function
-Secreting digestive enzymes
-Secreting Na bicarbonate to neutralize stomach acid
-This results in pepsin neutralized but pancreatic enzymes activated.
Pancreas Enzymes provided to small intestine:
-Trypsin and Chymotrypsin: proteases digest: proteins
-Pancreatic amylase: carbohydrate digests: starch
-Lipase: digest: fats
Step 6: The liver
-Produces bile to help lipases emulsify lipids and break down fats
-Stores glucose in form of glycogen, monosaccharides not glucose are turned into glucose & later used as source of energy.
- Makes enzymes to detoxe blood
-Deaminates amino acids: removing N, producing ammonia + urea
Bile
-Made of: water, cholesterol, bile salts, bile pigments
-800-1000 ML of yellow bile every day in gallbladder and acts as emulsifier
Hepatitis
-Infection in the liver that results in cirrhosis which is scar on liver that can come from excess alcohol
Step 7: Gallbladder
-Bile stored here between meals and bile salts injected into small intestine when needed.
-Lots of bile needed with heavy fats, though crystalize and turn into fats with fatty and cholesterol-filled foods.
Step 8: Appendix
-Doesn’t have a purpose though add bacteria in digestion when needed.
Step 9: Large Intestine
-No digestion happens here though waste is eliminated through the rectum and anus
-Salt and water from chyme makes feces
-Bacteria breaks down undigested food and produces vitamins B12 and K.
Step 10: Large Intestine/Colon
-Takes water and electrolytes to produce feces
-nutrients and carbs are used to make vitamins K (again) and B and methane gas.
