The External Environment Within

Gastrointestinal Tract Overview

• The gastrointestinal tract is not entirely part of our body, as food we eat passes through our gastrointestinal tract, which is considered an external environment.

Mouth (Oral Cavity)

• The first place food goes to is the mouth (oral cavity).
• Main functions in the mouth: • Chewing (morcecation of food) • Hydrolysis (enzymatic digestion or breakdown of food)
• Goal: to create a bolus (a sphere of digested food) that can be swallowed.

Esophagus

• After swallowing, food passes through the esophagus.
• The esophagus just propels the bolus down to the next structure, without modifying it.

Stomach

• The stomach receives the bolus and performs: • Churning (physical breakdown of food) • Hydrolysis (enzymatic breakdown of food) • Storage of food if it's not time to pass it on
• Goal: to create chyme (a fluid substance) that can be passed on to the intestines.

Intestines

• The intestines receive the chyme and are divided into: • Duodenum • Small intestine (with three parts, to be discussed in a subsequent video) • Large intestine (also known as the colon)
• Main functions in the intestines: • Hydrolysis • Absorption of nutrients in the small intestine • Absorption of water, ions, and vitamin K in the large intestine

Rectum and Anus

• The rectum stores the processed food until it's time to expel it.
• The anus is the final exit point for the food through expulsion.

Accessory Organs

• Other organs involved in digestion include: • Liver • Gallbladder • Pancreas (to be discussed in subsequent videos)

Explore the concept that the food we eat passes through our gastrointestinal tract, blurring the lines between our internal self and the external environment. How weird is that?