Carnivores, Omnivores and Herbivores

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Digestion In The Mouth

Food is both physically and chemically digested in the mouth

The food is physically digested using the teeth

Starch is chemically digested in the mouth using enzyme amylase which is made in the salivary glands

The pH in the mouth is around neutral (varies from 6.4-7.4), ideal for salivary amylase

Saliva also contains mucin that moistens and softens food making it easier to eat

TEETH

Enamel is the hardest substance in the body and covers the crown of the tooth. It protects the tooth and forms a hard, biting surface. It consists almost entirely of calcium phosphate

Dentine is found just under the enamel and forms the bulk of the tooth. Though tough, it is not as hard as enamel or as resistant to decay. It is penetrated by thread-like extensions of cells in the pulp cavity. They make the dentine sensitive to touch, temperature and acids. Since it contains protein, dentine can be used as food by decay-causing bacteria

Pulp Cavity is in the centre of the tooth and contains blood vessels which bring food & oxygen to the dentine &nerve endings sensitive to pain

Cement covers the root of the tooth and is similiar to bone.

Type of Tooth

Incisors

Canines

Premolars

Molars

Function

This tooth is for biting or cutting food and is sharp and chisel-like

This tooth is for tearing food e.g. meat. They are pointy in shape

This tooth is for crushing or grinding food. It has only 2 cusps and a double root

This tooth is for crushing or grinding food. It has 4 cups and a double or triple root

Skull and teeth of a rabbit

Skull and teeth of a dog

Herbivore

Well developed facial muscles needed for grinding and chewing tough plant material

Side-to-side motion of jaw to help molars chew and cut up food

Extensive long chewing before swallowing as it is hard to break down because of cell walls

Do not need canines as they don't need to tear food like meat

Wide diastema to store food to allow the saliva to attack and break down the food more effectively

Broad flat blade-like shaped incisors to cut the grass and then be ground up by molars

Carnivore

Up and down movement of jaw makes slicing and grinding more effective

Sharp jagged blade-shaped molars to help tear up and slice the meat

No need to chew much as teeth quickly crush food. Easy digestion

Short pointed incisors scrape meat off bone & grips

Long sharp curved canines kill prey by penetrating vital organs

Small gap between canines and premolars so large canines can slide into place, no need to store food

The Problem With Cellulose

Digestive system of herbivores have adaptations as they eat cellulose

Plants are difficult to digest as they have cell walls to cellulose

Animals that eat cellulose can't digest it and must have bacteria inside them to break it down into substances herbivores can use

Foregut digesters (cattle, sheep, deer & goats are ruminants)

Have a stomach divided into a series of large chambers including a rumen which contains the bacteria that digests plant material

The chambers means that the passage of food is slowed, therefore time for micro-organisms to act on the cellulose

Hindgut digesters (rabbits)

They have a caecum

Appendix is found at the end of the caecum

Caecum houses the bacteria

Digestable matter passes into the caecum where anaerobic bacteria ferment the material and more absorption takes place

Carnivores have a relatively small stomach because of the high nutrient density of their diet. They have a shorter digestive system as they can more easily obtain energy from the food/meat that they eat, as the protein is more easily digested in the stomach by enzymes before it gets to the large intestine.

They have a shorter large intestine because most of the digestion of meat / protein occurs in the stomach so most of the digested molecules have already been absorbed in the small intestines and only the remaining molecules and water need to be absorbed

They do not need a large caecum as they are able to produce all the enzymes that they need to digest their food, such as pepsin and lipase. Carnivores still have a caecum; however, it is very much diminished and does not contain bacteria needed for digestion.

Digestion In The Mouth

Foregut & Hindgut Digesters