The Human

Digestive

System

The Human Digestive System

The digestive system of humans consists of a

digestive tract and several accessory organs which

work together to help the body gain nutrients from

food.

The organs form a tract through the body which

function to mechanically and chemically digest the

food for absorption.

The accessory organs assist in the digestion of food

into its component nutrients which can then be

absorbed.

salivary

glands

esophagus

tongue

pharynx

lower esophageal

sphincter

stomach

pancreas

pancreatic duct

descending colon

rectum

anus

gall bladder

common bile duct

duodenum

pyloric sphincter

liver

small intestines

ascending colon

transverse colon

cecum

Organ Structure Function

Oral Cavity

• Contains the tongue, which is a large

muscle in the mouth that has taste

buds in structures called papillae

• Also the location of teeth and exit

point of salivary glands

• Tongue and teeth aid in mixing

and chewing to break down

and taste food

• This is mechanical digestion of

food

Esophagus

• Long muscular tube leading to the

stomach

• Lined with both circular and

longitudinal muscles

• Secretes mucin (a lubricant)

• Muscles around the tube push

the food bolus down towards

the stomach

• This movement is known as

peristalsis

Stomach

• Food bolus enters through the lower

esophageal sphincter

• Secretes mucous and acid

• Contains folds called rugae

• Chyme exits through the pyloric

sphincter into the small intestines

• Churning of the stomach helps

to mechanically digest food.

• Hydrochloric acid aids in

chemical breakdown of food.

• The enzyme pepsin chemically

breaks down protein.

Organ Structure Function

Duodenum

• First part of the small intestine after

chyme moves through the pyloric

sphincter

• Ducts release secretions here

• Muscles move chyme around to

mix it with digestive enzymes that

are released by the pancreas and

gall bladder to help with chemical

digestion

Small

Intestines

• Consists of the duodenum, the

jejunum, and the ileum

• Very long tube with many folds

called villi and microvilli

• Connects to the large intestines

through the ileocecal valve

• Absorption of nutrients through villi

and microvilli which provide

increased surface area

Colon

• Larger diameter and shorter length

than small intestine

• Contain bacteria that assist in

digestion

• Absorption of water and

breakdown products from

bacteria

Rectum

and Anus

• Last tube of the digestive tract

before exit of waste products

through the anal sphincter

• Storage of undigested waste

before controlled elimination

Organ Structure Function

Salivary

Glands

• Glands located above and

below the oral cavity which

release liquids into the mouth

through salivary ducts

• Produces saliva and the

enzyme amylase which breaks

down some carbohydrates

Liver• Large organ located above

the stomach

• Produces bile which breaks

down globs of fat

Gall

Bladder

• Small sack under the liver that

is connected to the liver and

the duodenum through the

common bile duct

• Storage of bile before it is

release into the duodenum

through the bile duct

Pancreas

• Located behind the stomach

and connected to the

duodenum through the

pancreatic duct

• Production of enzymes to break

down fats and proteins