The Digestive System

Question 1

Types of digestion

Answer 1

• mechanical digestion uses abrasives and/or muscle action to break the food into smaller pieces
• mechanical digestion happens early to reduce the surface area of the food pieces before chemical digestion starts
• chemical digestion uses molecules called enzymes to break the chemical linkages holding food together

Question 2

Digestive tracts

Answer 2

• simple animals like jellyfish have an ‘incomplete’ bag-type system with only one opening
• more complex animals have a ‘complete’ tube with two openings, with one way flow of materials

Question 3

Ingestion

Answer 3

• eat, chew, and swallow your food
• your tongue and nasal cavity have taste buds to assess the quality of food
• your tongue pushes food between sets of teeth and to your throat for swallowing

Question 4

Types of teeth

Answer 4

• incisors = nip and cut
• canines = pierce and tear
• premolars/molars = crush and grind

Question 5

Diet and teeth

Answer 5

• you can tell an animal’s diet by its teeth
• pointy teeth and prominent canines = carnivore
• flattened incisors, no canines, flattened molars = herbivore
• compromise = omnivore

Question 6

Gizzards

Answer 6

• some animals lacking teeth have a crop to store food after ingestion and a muscular gizzard to later grind it up
• sometimes these animals swallow small stones or grit to help grind up the food

Question 7

Peristalsis

Answer 7

• the digestive tract is a tube, or bag, of smooth muscle

* this rhythmically contracts to push food by the process of peristalsis

Question 8

Digestive enzymes

Answer 8

• enzymes that chemically digest fat, carbohydrates and protein are released by several accessory organs and by the small intestine itself
• examples = amylase (digests starch), pepsin (digests protein)

Question 9

Accessory organs

Answer 9

• salivary glands = release saliva to lubricate your food
• liver = produces bile, which allows fats to mix better with water, in which the fit digesting enzymes are mixed
• gall bladder = stores bile until it is needed to emulsify fats
• pancreas = produces a number of digestive enzymes that are released into the small intestine, also produce a base to neutralize stomach acid

Question 10

Key organs

Answer 10

• epiglottis = prevents food from entering the larynx
• esophagus = pushes food from pharynx to stomach by peristalsis
• stomach = holds food, chemical and physical digestion, acid secretion kills most harmful microbes or parasites
• small intestine = chemical digestion, absorption of nutrients
• large intestine = water absorption, formation of solid feces
• rectum = temporary storage of feces