The Digestive System Overview

Study Notes

The digestive system is a group of organs that work together to break down food and liquids into nutrients the body needs.
Digestion is the process of breaking down food.
Absorption is the process of nutrients entering the bloodstream, which occurs in the small intestine.

Mouth:
- The digestive process begins in the mouth with chewing (mechanical digestion).
- Bolus is the chewed food in the mouth.
- Digestive enzymes in saliva begin to break down food molecules (chemical digestion).
- Enzyme - a substance that speeds up chemical digestion.
- Ptyalin is an enzyme in saliva that converts starch into sugar.
Esophagus:
- A long, narrow tube that carries food from the mouth to the stomach.
- Peristalsis is the involuntary muscle contractions that move food through the digestive tract.
Stomach:
- An elastic sac that churns, digests, and stores food.
- Chyme is the soupy mixture of broken-down food and gastric juices formed in the stomach.
Small Intestine:
- The major site of digestion and absorption of nutrients.
- Villi are small finger-like projections in the small intestine walls that help absorb digested nutrients.
Large Intestine:
- Absorbs water, minerals, and remaining nutrients from food.
- Forms waste into stool/feces.
Rectum:
- The final section of the large intestine (approx. 12 cm long).
- Feces pass into the rectum and are eliminated from the body through the anus.
Anus:
- The body opening at the end of the digestive tract (approx. 4 cm long).
- Contains vertical ridges called anal columns.

Salivary Glands: Produce saliva, which moistens the mouth and contains digestive substances.
- Parotid glands: The largest, located in the cheeks.
- Submaxillary glands: Located under the jaw, produce most of the saliva at night.
- Sublingual glands: The smallest, found under the tongue.
Pancreas: Secretes pancreatic juice into the small intestine.
Liver:
- The largest gland in the body.
- Secretes bile (helps break down fats into fatty acids).
Gallbladder:
- Located beneath the liver.
- Stores bile.

Diarrhea: Frequent watery bowel movements.
Intestinal worms/parasites: Can cause stomach aches and steal nutrients from the intestine.
Indigestion/dyspepsia: Upset stomach.
Constipation: Difficult bowel movements due to hard stool.
Appendicitis: Inflammation of the appendix.
Ulcer: A sore in the lining of the stomach, small intestine, or esophagus.
Gallstones: Hardened deposits of bile that can form in the gallbladder.