Digestive System
The digestive system is a set of long tubes that provide nutrients to our body each time we eat. It produces a series of enzymes and substances that break down food into tiny molecules easy to absorb by cells.
Digestion at work...
FIVE STAGES OF DIGESTION
INGESTION: Food intake through the mouth.
MECHANICAL DIGESTION: Physical movements of the organs that breaks food into smaller pieces. Chewing includes churning food with the teeth, and moving it with the tongue to swallow it. Peristalsis is a set of muscular contractions of the rings that make up the esophagus and intestines to move food thorught the digestive canal.
CHEMICAL DIGESTION: Substances carry out chemical reactions to break down food into simpler molecules.
ABSORPTION: Epithelial cells lining through all the system that transport substances by difussion to the blood stream. Most absorption occurs in the intestines where surface area is increased due to fingerlike structures called villi. Gut bacteria or gut microbiota that live in the large intestine help to produce vitamins.
EGESTION: Expulsion of wastes and undigested food by the anus.
CHEMICAL DIGESTION
MOUTH: Salivary glands produce saliva to soften food and to lubricate the digestive tract. Saliva contains salivary amylase to start breaking down starch into smaller molecules. The food turns into a soft mass called Bolus.
STOMACH: The walls of the stomach produce pepsin to break down proteins to peptides. Hydrochloric Acid speeds up the reaction. The bolus turns into a dense fluid called Chyme.
DUODENUM: Is the first portion of the small intestine. It receives juices from the accesory organs, the liver, gall bladder and pancreas, to complete chemical digestion.
1. The liver produces bile that is stored in the gall bladder. Bile dissolves fat to facilitate digestion.
2. The pancreas produces amylase to break down starch into glucose, peptidase to break down peptides into aminoacids, lipase to break fats into fatty acids and glycerol. Insulin is released to regulate the levels ofglucose in the blood after absorption.