The Digestive System Presents:
Jan 16, 2016
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)