Human Digestive System Overview

Overview of the Human Digestive System

The human digestive system is a complex process by which the body breaks down and absorbs nutrients from food.

Mouth

• Also known as the oral cavity
• Food enters the mouth where it is chewed by teeth and mixed with saliva that contains enzymes to break down carbohydrates
• The tongue helps to mix food with saliva and form a bolus
• The bolus is swallowed, and it passes through the pharynx into the esophagus

Esophagus

• A muscular tube that uses peristalsis to propel food into the stomach
• Food is pushed through the esophagus by involuntary muscle contractions
• The lower esophageal sphincter (LES) relaxes to allow food to enter the stomach

Stomach

• A sac-like organ that secretes digestive enzymes and acid to break down proteins and fats
• The stomach lining secretes mucus to protect itself from the acidic environment
• The stomach churns and mixes food with digestive enzymes for about an hour before releasing it into the small intestine
• The stomach mixes food with hydrochloric acid, pepsin, and gastric amylase to break down proteins and carbohydrates

Small Intestine

• A long, thin tube where most of our nutrient absorption takes place
• The walls of the small intestine are lined with finger-like projections called villi, which increase the surface area for absorption
• Nutrients are absorbed into the bloodstream through the walls of the small intestine
• The small intestine is divided into three parts: duodenum, jejunum, and ileum

Large Intestine (Colon)

• A shorter, wider tube that absorbs water and electrolytes, and stores and eliminates waste
• The large intestine is also home to a diverse community of microbes known as the gut microbiome
• The large intestine is divided into four parts: ascending, transverse, descending, and sigmoid colon
• The large intestine absorbs water and electrolytes, and the remaining waste is eliminated through the anus

Mouth

• Food enters the mouth, where teeth chew it and mix it with saliva containing enzymes that break down carbohydrates.
• The tongue helps mix food with saliva, forming a bolus.
• The bolus is swallowed, passing through the pharynx into the esophagus.

Esophagus

• A muscular tube that uses peristalsis to propel food into the stomach.
• Involuntary muscle contractions push food through the esophagus.
• The lower esophageal sphincter (LES) relaxes to allow food to enter the stomach.

Stomach

• A sac-like organ that secretes digestive enzymes and acid to break down proteins and fats.
• The stomach lining secretes mucus to protect itself from the acidic environment.
• The stomach churns and mixes food with digestive enzymes for about an hour before releasing it into the small intestine.
• The stomach mixes food with hydrochloric acid, pepsin, and gastric amylase to break down proteins and carbohydrates.

Small Intestine

• A long, thin tube where most of our nutrient absorption takes place.
• The walls of the small intestine are lined with finger-like projections called villi, increasing the surface area for absorption.
• Nutrients are absorbed into the bloodstream through the walls of the small intestine.
• The small intestine is divided into three parts: duodenum, jejunum, and ileum.

Large Intestine (Colon)

• A shorter, wider tube that absorbs water and electrolytes, and stores and eliminates waste.
• The large intestine is home to a diverse community of microbes known as the gut microbiome.
• The large intestine is divided into four parts: ascending, transverse, descending, and sigmoid colon.
• The large intestine absorbs water and electrolytes, and the remaining waste is eliminated through the anus.

Learn about the process of digestion, from the mouth to the esophagus, and how the body breaks down and absorbs nutrients from food.