The Comparative Anatomy of Eating

Summary

	Carnivore	Herbivore	Omnivore	Human
Facial Muscles	Reduced to allow wide mouth gape	Well-developed	Reduced	Well-developed
Jaw Type	Angle not expanded	Expanded angle	Angle not expanded	Expanded angle
Jaw Joint Location	On same plane as molar teeth	Above the plane of the molars	On same plane as molar teeth	Above the plane of the molars
Jaw Motion	Shearing; minimal side-to-side motion	No shear; good side-to-side, front-to-back	Shearing; minimal side-to-side	No shear; good side-to-side, front-to-back
Major Jaw Muscles	Temporalis	Masseter and pterygoids	Temporalis	Masseter and pterygoids
Mouth Opening vs. Head Size	Large	Small	Large	Small
	Carnivore	Herbivore	Omnivore	Human
Teeth: Incisors	Short and pointed	Broad, flattened and spade shaped	Short and pointed	Broad, flattened and spade shaped
Teeth: Canines	Long, sharp and curved	Dull and short or long (for defense), or none	Long, sharp and curved	Short and blunted
Teeth: Molars	Sharp, jagged and blade shaped	Flattened with cusps vs complex surface	Sharp blades and/or flattened	Flattened with nodular cusps
Chewing	None; swallows food whole	Extensive chewing necessary	Swallows food whole and/or simple crushing	Extensive chewing necessary
Saliva	No digestive enzymes	Carbohydrate digesting enzymes	No digestive enzymes	Carbohydrate digesting enzymes
Stomach Type	Simple	Simple or multiple chambers	Simple	Simple
	Carnivore	Herbivore	Omnivore	Human
Stomach Acidity	Less than or equal to pH 1 with food in stomach	pH 4 to 5 with food in stomach	Less than or equal to pH 1 with food in stomach	pH 4 to 5 with food in stomach
Stomach Capacity	60% to 70% of total volume of digestive tract	Less than 30% of total volume of digestive tract	60% to 70% of total volume of digestive tract	21% to 27% of total volume of digestive tract
Length of Small Intestine	3 to 6 times body length	10 to more than 12 times body length	4 to 6 times body length	10 to 11 times body length
Colon	Simple, short and smooth	Long, complex; may be sacculated	Simple, short and smooth	Long, sacculated
Liver	Can detoxify vitamin A	Cannot detoxify vitamin A	Can detoxify vitamin A	Cannot detoxify vitamin A
Kidney	Extremely concentrated urine	Moderately concentrated urine	Extremely concentrated urine	Moderately concentrated urine
Nails	Sharp claws	Flattened nails or blunt hooves	Sharp claws	Flattened nails