The Digestive System Presents:

Digestion begins with your imagination! As soon as you see, smell, or even imagine

food, our salivary glands begin to prepare by producing saliva.

Physical or mechanical digestion begins in the mouth.

In the mouth, two types of digestion occur:

Physical or mechanical digestion Teeth shred, tear, and grind food Food is formed into a bolus (Greek for “ball”) by

the tongue

Chemical digestion Saliva contains the enzyme salivary amylase

The first step in the digestion of food There are 32 teeth in a normal adult (from

front to back)EACH OF TOP, BOTTOM, LEFT, RIGHT

incisorscanine

(cuspid)pre-molars(bicuspids)

molars

Flat, blade-like

Long, sharp Wide, flat Wider, flat

2 1 2 3

Biting/cuttingShredding/

tearingGrinding Crushing

2 incisors x 4 = 81 canine x 4 = 42 pre-molars x 4 = 83 molars x 4 = 12 (includes 4

wisdom teeth)

= 32

Parts of a tooth Crown – the visible part of

the tooth Root – the anchor of the

tooth that extends into the jaw bone

Enamel – the tough, white, shiny outer surface

Dentin – hard but porous tissue; harder than bone

Pulp – soft centre of tooth; nourishes dentin

Cementum – layer of tough, yellowish, bone-like tissue covering root of tooth; helps to hold tooth in socket

Nerves and blood vessels – transmit signals to and from the brain (hot, cold, pain, etc)

Begins chemical digestion with the enzyme salivary amylase Amylase starts to break down

carbohydrates, starches, and sugars Saliva also lubricates food so it does

not scratch the mucous membranes of the alimentary canal

It also dissolves food particles and activates your taste buds

Saliva is produced by 3 salivary glands: Parotid gland

This is the largest salivary gland and is located in front of and below the ears

Submandibular gland Located at the floor of the

mouth near the rear of the cheeks

Sublingual gland Located at the floor of the

mouth underneath the tongue

After the food has been torn, shredded, ground, and moistened by the teeth and saliva, it is formed into a ball-like mass called a bolus

To swallow, the tongue is elevated against the top of the palate and propels the food down the throat

During swallowing, a flap of cartilage called the epiglottis folds back to cover the entrance to the larynx to prevent food and drink from entering the windpipe, and food continues it’s trip to the anus.

This is a long, thin tube tube with muscular walls

Muscles contract rhythmically in a movement called peristalsis which move the bolus and fluids along the digestive tract

This contraction is involuntary and independent of gravity

Also called the esophageal sphincter

When it’s contracted, it closes the opening to the stomach

When it’s relaxed, food is allowed to enter

Gets its name from being close to the heart

It’s also helpful in preventing reflux or heartburn

Caused by a physiological process by a sudden jerk in the diaphragm that causes you to breathe in

The hiccup sounds are made by the vocal cords (glottis)

Eating too fast Air to stomach

Movement of stomach acid into the esophagus

Metabolic disorder (renal failure)