Overview
This lecture provides an overview of the main sections of the gastrointestinal (GI) tract, describing the structure and primary functions of each part.
Introduction to the GI Tract
- The GI tract is a continuous tube through which food passes, connecting the outside environment to the body.
- Food inside the GI tract is technically still considered part of the external environment until absorbed.
Main Sections and Functions of the GI Tract
Mouth (Oral Cavity)
- The mouth is where food enters and chewing (physical breakdown) occurs.
- Hydrolysis, or enzyme-assisted breakdown, also begins in the mouth.
- Food is formed into a bolus (sphere of digested food) for swallowing.
Esophagus
- The esophagus transports the bolus from the mouth to the stomach.
- Its primary function is propulsion; no digestion or absorption occurs here.
Stomach
- The stomach churns food (mechanical breakdown) and further breaks it down via hydrolysis (enzymatic action).
- Acts as temporary storage for food until it’s ready to move on.
- Converts the bolus into chyme, a semi-liquid substance.
Small Intestine
- Divided into three sections (to be detailed in further videos).
- Performs extensive hydrolysis and is the main site for absorption of nutrients into the body.
Large Intestine (Colon)
- Absorbs water, ions, and some vitamins (e.g., vitamin K), but not significant nutrients.
- Also known as the colon.
Rectum and Anus
- The rectum stores waste until it is ready to be expelled.
- Waste is eliminated from the body through the anus (expulsion).
Accessory Organs (Preview)
- The liver, gallbladder, and pancreas assist digestion and will be covered in future lectures.
Key Terms & Definitions
- Hydrolysis — Enzyme-assisted breakdown of food.
- Bolus — A small, rounded mass of chewed, digested food ready for swallowing.
- Chyme — Semi-liquid mixture of food and digestive juices produced in the stomach.
- Propulsion — The movement of food through the GI tract.
- Colon — Another term for the large intestine.
- Expulsion — The elimination of waste through the anus.
Action Items / Next Steps
- Review the functions of each GI tract section.
- Prepare to learn details about the small intestine’s three parts and accessory organs in upcoming lectures.