GI Tract Basics
This enzyme in saliva begins the chemical digestion of starch in the mouth.
What is salivary amylase
These stomach cells produce HCl, which drops the stomach pH to about 1.5–2.
Parietal cells
The three sections of the small intestine in order.
Duodenum, jejunum, ileum
The liver produces this substance that breaks up fat droplets so enzymes can digest them more easily.
Bile
This hormone from G cells in the stomach tells parietal cells to make more HCl.
Gastrin
The muscular tube that uses peristalsis to move a bolus to the stomach, measuring about 25 cm with no digestion occurring.
What is the esophagus?
These cells secrete pepsinogen, which gets activated into pepsin by HCl to digest proteins.
Chief cells
These tiny finger-like projections on the small intestine wall dramatically increase surface area for absorption.
Villi (and microvilli)
This small organ stores and concentrates bile between meals, releasing it when triggered by CCK.
gallbladder
Secretin is released when acidic chyme enters the duodenum. What does it tell the pancreas to do?
Secrete bicarbonate
Food, water, and air all pass through this shared passageway in the throat. The epiglottis covers the airway when you swallow.
What is The pharynx?
These stomach folds allow the stomach to expand — it can hold up to about 4 liters when full.
Rugae
The final section of the small intestine; the only place that absorbs vitamin B12 and recycles bile salts.
The ileum
This organ, the largest internal organ in the body, produces bile and detoxifies drugs and alcohol.
The Liver
This autoimmune disease is triggered by gluten and destroys the villi in the small intestine, causing severe malabsorption
Celiac disease
The approximate total length of the entire GI tract.
About 9 meters
Parietal cells also produce this molecule (not HCl) that is essential for absorbing vitamin B12.
Intrinsic factor
is the small intestine the primary absorption site?
True
When you eat a fatty meal, this hormone signals the gallbladder to contract and release bile
CCK
A deficiency of this brush-border enzyme causes undigested milk sugar to be fermented by gut bacteria, leading to bloating and diarrhea
Lactase (lactose intolerance)
This phase of swallowing is the ONLY one you can consciously control — your tongue pushes food to the back of the mouth.
The voluntary phase
The semi-liquid mixture of food and gastric juices that leaves the stomach through the pyloric sphincter.
Chyme
What does Bicarbonate in the Duodenum do?
Neutralize acids
This bicarbonate-rich fluid from the pancreas neutralizes the acidic chyme entering the duodenum.
Pancreatic juice
Dysfunction of the lower esophageal sphincter allows stomach acid to flow back up, causing this common condition
GERD