By: Jama Willbanks, MS, NREMT-P

The Digestive

System

The Alimentary Canal

A long muscular tube that begins at the mouth and includes the oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines.

The Alimentary Canal

The accessory organs include the salivary glands, tongue, teeth, liver, gallbladder, and pancreas.

The Mouth

Food is tasted, broken down by teeth, lubricated and partially digested by saliva.

The Teeth

Break down food by chewing and grinding (mastication).

The Tongue

The Tongue

Muscular organ. Contains special

receptors called taste buds.

Aids with chewing and swallowing food.

Hard Palate and Soft Palate

Hard palate: a bony structure that forms the roof of the mouth and separates the mouth from the nasal cavities.

Soft palate: behind hard palate, separates the mouth from the nasopharynx.

Salivary Glands

The parotid, sublingual, and submandibular glands produce a liquid called saliva.

Saliva lubricates the mouth during speech and chewing and moistens food so it can be swallowed easily.

Salivary Glands Saliva contains an enzyme called salivary

amylase. Salivary amylase begins the chemical

breakdown of carbohydrates or starches into sugars that can be taken into the body.

Salivary Glands at Work

Bolus

After the food is chewed and mixed with saliva, it is called a bolus.

The Pharynx (Throat)

The pharynx is a tube that carries both air and food.

It carries the air to the trachea and food to the esophagus.

The Esophagus

The esophagus is the muscular tube posterior to the trachea that receives the bolus from the pharynx and carries it to the stomach.

The esophagus relies on peristalsis, a rhythmic, wavelike, involuntary movement of its muscles to move the food in a forward direction.

The Stomach

The stomach receives food from the esophagus.

The mucous membrane lining of the stomach contains folds called rugae that disappear as the stomach fills with food and expands.

Stomach

Food usually remains in the stomach for about one to four hours.

During this time, food is converted into a semifluid material called chyme by gastric juices produced by glands in the stomach.

The Small Intestine

When the food, in the form of chyme, leaves the stomach it enters the small intestine.

Purpose of the Small Intestine

Products of digestion are absorbed into the bloodstream for use by the body cells.

The Small Intestine

The small intestine is a coiled section of the alimentary canal about twenty feet long and one inch in diameter.

Villi

Walls of small intestine are lined with villi that contain blood capillaries and lacteals.

The Small Intestine

It is divided into three sections: duodenum, jejunum, and ileum.

Duodenum

The first nine to ten inches of the small intestine. Bile from the gallbladder and liver and

pancreatic juice from the pancreas enter this section through ducts or tubes.

Jejunum & Ileum

The jejunum is about eight inches long. It forms the middle section of the small

intestine. The Ileum is the final 12 feet and connects

with the large intestine at the cecum. The ileocecal valve prevents backflow.

Large Intestine

Approximately 5 feet long.

Approximately 2 inch diameter.

Purpose of Large Intestine

Absorption of water and any remaining nutrients.

Storage of indigestible materials before they are eliminated.

Synthesis and absorption of some vitamins. Transportation of waste.

Purpose of Large Intestine

Transportation of waste.

Sections of the Intestine

Cecum Colon

AscendingTransverseDescendingSigmoid Colon

• Rectum: final six to eight inches.

Big Word of the Day

Esophagogastroduodenoscopy 

esophagus gastric

duodenum

scope

We’ll just call it EGD

EGD: A diagnostic test used to aid in identifying abnormalities of the esophagus, stomach, and small intestines.

Abnormalities such as: esophagitis, inflammatory bowel disease, ulcers, tumors, gastritis, and polyps.

Accessory Organs

LiverGallbladderPancreas

Liver

Largest gland in the body. Located under the diaphragm and in the upper

right quadrant of the abdomen. Secretes bile which is used to emulsify fats in

the digestive tract. Bile also makes fats water soluble (which is

necessary for absorption).

Liver

Stores sugar in the form of glycogen. Glycogen is converted to glucose and

released into the bloodstream when needed. Stores iron and certain vitamins. Produces heparin which prevents clotting in

the blood.

Liver

Produces blood proteins such as fibrinogen and prothrombin which aid in clotting of the blood.

Detoxifies substances such as alcohol and pesticides.

Destroys bacteria.

Gallbladder

Small, muscular sac located under the liver and attached to it by connective tissue.

Stores and concentrates bile which it receives from the liver.

Gallbladder contracts to push bile through the common bile duct and into the duodenum.

Pancreas

Located behind the stomach. Produces pancreatic juices which contain

enzymes to digest food. Produces insulin which regulates the metabolism

of glucose into energy.