Human Digestive System Table

Interactive Timeline of Digestion. Trace the journey of food from Ingestion to Egestion.

Mouth (Oral Cavity)

Teeth chew food (Mastication) breaking it into smaller pieces. Tongue mixes food with saliva to form a round ball called 'Bolus'.
pH: 6.8 (Slightly Acidic)Bolus Formation
Key Enzymes / Factors
Salivary Amylase (Ptyalin)Lysozyme
LocationHead

Salivary Glands

Parotid, Submandibular, and Sublingual glands secrete saliva which moistens food and initiates starch digestion.
pH: 6.8Lubrication
Key Enzymes / Factors
Salivary Amylase
LocationMouth (3 pairs)

Esophagus

A muscular tube that pushes the bolus down to the stomach via rhythmic wave-like contractions called Peristalsis. No digestion occurs here.
pH: 7.0 (Neutral)Swallowing (Deglutition)
LocationThroat to Stomach

Stomach

Muscular walls churn food. Gastric glands secrete HCl (kills bacteria) and Pepsinogen. Food becomes a semi-solid paste called 'Chyme'.
pH: 1.5 - 3.5 (Highly Acidic)Chyme Formation
Key Enzymes / Factors
Pepsin (Proteins → Peptides)Renin (in infants)Gastric Lipase
LocationUpper Abdomen (Left)

Liver

Largest gland. Produces Bile which emulsifies fats (breaks large fat globules into tiny droplets). Also detoxifies blood and stores Glycogen.
pH: Alkaline BileEmulsification
Key Enzymes / Factors
No Enzymes (produces Bile Salts)
LocationRight Upper Abdomen

Gallbladder

Stores and concentrates Bile produced by the Liver. Releases it into the Duodenum when fatty food enters.
pH: 7.6 - 8.6Storage & Concentration
LocationUnder Liver

Pancreas

Leaf-like heterocrine gland. Secretes Pancreatic Juice containing enzymes for carbohydrates, proteins, and fats into the Duodenum.
pH: Alkaline JuiceSecretion
Key Enzymes / Factors
TrypsinChymotrypsinPancreatic AmylaseLipase
LocationBehind Stomach

Small Intestine

Longest part (6m). Duodenum receives bile/pancreatic juice. Jejunum/Ileum have Villi for absorbing nutrients into blood. Food becomes 'Chyle'.
pH: 7.4 - 7.8 (Alkaline)Absorption (Villi)
Key Enzymes / Factors
ErepsinMaltaseSucraseLactaseLipase
LocationAbdomen (Central)

Large Intestine

Absorbs water, minerals, and drugs from undigested food. Bacteria produce Vitamin K. Undigested waste becomes solid feces.
pH: 6.0 - 7.0Reabsorption
Key Enzymes / Factors
None (Bacterial action)
LocationAbdomen (Peripheral)

Rectum & Anus

Rectum stores feces temporarily. Anus expels waste from the body controlled by sphincters.
Excretion
LocationPelvis

Key Stages of Digestion

Digestion is a complex process categorized into 5 main steps: Ingestion, Digestion, Absorption, Assimilation, and Egestion.

1. Ingestion

Taking food in through the mouth.

2. Digestion

Breakdown of complex food.

3. Absorption

Nutrients enter bloodstream.

4. Egestion

Removal of waste.

Enzymes & Glands Guide

Stomach

Gastric Juices

  • PepsinBreaks down Proteins → Peptides
  • HClActivates Pepsin, kills germs
Accessory Organs

Liver & Pancreas

  • Bile (Liver)Emulsifies Fats (Physical breakdown)
  • Trypsin (Pancreas)Proteins → Amino Acids

Frequently Asked Questions

What is the first step of digestion?

Digestion starts in the Mouth (Ingestion). Teeth break down food mechanically, and Salivary Amylase helps break down starch chemically.

What is the role of Hydrochloric Acid (HCl)?

HCl in the Stomach creates an acidic environment (pH 1.5-3.5) necessary for the enzyme Pepsin to digest proteins. It also kills bacteria in food.

Where does most absorption happen?

Most nutrients are absorbed in the Small Intestine. Its inner walls have finger-like projections called Villi that increase surface area for maximum absorption.

What is Peristalsis?

Peristalsis is the wave-like muscle contraction that pushes food down the Alimentary Canal, from the Esophagus to the Anus.

Does the Liver digest food?

The Liver does not touch food directly. It produces Bile, which is stored in the Gallbladder and released into the Small Intestine to emulsify fats.

What is the function of the Pancreas?

The Pancreas secretes digestive enzymes (Trypsin, Lipase, Amylase) into the Small Intestine to break down proteins, fats, and carbohydrates.

What happens in the Large Intestine?

The Large Intestine absorbs water and salts from the undigested food material, turning liquid waste into solid stool (feces).

What works on proteins in the stomach?

The enzyme Pepsin breaks down proteins into peptides in the stomach. In infants, Renin helps digest milk proteins.

What is the length of the Small Intestine?

The Small Intestine is about 6-7 meters (20-23 feet) long in adults. It is called "small" because of its narrow diameter compared to the large intestine.

What is Villi?

Villi are tiny, finger-like projections lining the Small Intestine. They are rich in blood vessels and absorb nutrients into the bloodstream.