More Digestion Notes from Old Notes Flashcards
Ingestion
take food into digestive tract
Mastication
physical breakdown of large clumps into small clumps to increase surface area for digestive enzymes
Digestion
Chemical breakdown of large molecules into small molecules that can be absorbed
Absorption
Movement of molecules into tissues of body across membrane
Egestion
Elimination of materials from GI tract
Defecation
Vomiting
Purpose of Saliva
To create a solution for digestive enzymes to work since they are water soluble
Chyme
Term for material moving through GI tract
Made up of water + food + enzyme + etc.
Amylase
In saliva that digest amylose (a starch)
Where does digestion begin?
Begins in the mouth, but the bulk of digestion occurs downstream
What is peristalsis?
Rhythmic contractions
Used in the movement of food from the esophagus to the stomach
Overall look at the GI tract
Oral cavity Mastication and some carbohydrate digestion Pharynx Transport Esophagus Transport Stomach Storage and protein digestion Small intestine Digestion and absorption Large intestine Salt and water absorption
Name the accessory organs and their function
Salivary Glands - saliva
Pancreas - pancreatic juice containing digestive enzymes
Liver - bile which aids in lipid digestion (it doesn’t digest lipid, only aids in digestion of)
• ^^ These are not part of digestive tract, they add material to GI tract
Teeth
Tongue
T/F: The hypopharyngeal sphincter normally closes off the esophagus when we are not swallowing
T
What is the function of the gastroesophageal sphincter?
A gastroesophageal sphincter near the stomach area of the esophagus at diaphragm keeps material that has entered the stomach from going back up to the esophagus
What is heartburn?
Movement of acid chyme upstream to esophagus and the gastroesophageal sphincter has failed doing its job
Regions & Purpose of the Stomach
There are muscles in the stomach that churn the chyme and allow it to move downstream and enter the small intestines
Portion where esophagus comes in is called the cardiac region
The portion that bulges out is called the Fundus
The central part is called the body
The very end where it meets the intestines is called the pyloris
○ There is a pyloric sphincter there which closes off and keeps material in the stomach
○ We use small intestine to digest and absorb but we don’t want to overwhelm it
○ Therefore, we want to allow food to enter in small portions at a rate that the small intestine can process it
Goblet Cells
Secrete alkaline mucous which will form a barrier on top of the epithelial cells of stomach to help prevent acid contact with cells
There is also constant replacement of stomach lining cells every 4 day or so
Purpose of G cells
Secrete Gastrin
Parietal Cells
Secrete HCl
Lowers pH in chyme
□ More protein you eat in food, the more acid you secrete
□ Low pH needed to maintain shape of pepsin to keep it active
H+ denatures proteins in food
□ This allows easier cleaving of peptide bonds by pepsin
H+ also kill many (but not all) bacteria in food
Helicobacter pylori
Can secrete cytotoxin that will erode epithelial lining of the stomach, leaving the cell exposed to acid causing gastric ulcer
Chief Cells
Secrete Pepsinogen
What is Pepsinogen?
Pepsinogen is an inactive digestive enzyme that is converted into pepsin (active enzyme) in the presence of high acid (H+) produced by parietal cell
What is Pepsin?
Pepsin is a protease that breaks down proteins into protein fragments at specific peptide sites
Where does most protein digestion occur?
Protein digestion begins in stomach, but pepsin does not break down all amino acids
Most protein digestion occurs in small intestines
What is Zymogen?
An inactive form of a protease secreted in the small intestine
Regions of the small intestine
Duodenum - upper region
Jejunum - middle region
Illeum - lower region
Duodenum
Where the bile and pancreatic duct empties into
Acid chyme enters here
What is the role of the small intestine?
Digestion
Absorption
Movement in the small intestines
Peristalsis - moves chyme downstream
Segmentation - mixing the chyme