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.