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Mouth
Functions
- 1. begin mechanical digestion
- 2. In higher vertebrates, it begins digestion of carbohydrates (some amphibian and rest of vertebrates
- a. does not complete it; just begins it
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Salivary Glands
- 1. Little
- or no oral glands
- 2. aquatic
- amphibian do not have oral glands; all of terrestrial do
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Teeth
1. all vertebrates except birds have teeth, which are edentate (without teeth)
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Teeth of Vertebrates
Types in vertebrates (fish, amphibians, reptiles)
Types in humans
Types in Birds
- a. homodont and pleurodont (fish, amphibians and reptiles)
- b. Humans are heterodont and most are diphyodont
- c. Birds don’t have teeth
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Explain Homodont and Pleurodont
- a. Homodont
- i. Means one shape (all of the teeth in a particular vertebrates mouth only have one shape [can be sharp, flat, etc. but they all have to be the same
- b. Pleurodont
- i. Many sets of teeth
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Explain heterodont and diphyodont
- a. Humans are heterodont and most are diphyodont
- i. Hetero: variety of shapes in same mouth
- Di= two sets: temporary and permanent
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Pharynx
short, muscular tube that is used both for digestion and respiration
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Pharynx function
- 1. Function in all vertebrates is transport of the bolus and transport of air
- a. No digestion takes place in the pharynx
- 2. Some exceptions:
- a. Some amphibians have digestive glands, which secrete digestive juices, don’t digest
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Stomach
Shape
- 1. In vertebrate:
- a. Can be J-shaped or straight
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Stomach Funciton in all
- a. To begin digestion of proteins
- i. Not to complete it, just to begin it
- b. Churning
- i. Convert bolus to chyme
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Stomach Lining
- 1. Lining of stomach, the mucosa, is thrown into irregular folds
- a. When stomach is empty, the stomach is all folded up
- i. Irregular folds, called rugae
- 1. Purpose is to decrease size of stomach so that it does not have to be too large
- a. When food in it, folds open up and it distends
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Stomach end
- 1. At end of stomach is the pyloric sphincter
- a. End of stomach where the small intestine starts
- b. Sphincter is circular, smooth muscle
- i. Controls the passage of food
- 1. Close when we want to slow down food
- 2. Open when we want food to pass
- c. This one is movement of chyme from stomach to small intestines
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Small Intestine
Parts
- 1. Two parts in all but mammals:
- a. Duodenum
- b. Ileum
- 2. Mammals have three parts (in order)
- a. Duodenum
- b. Jejunum
- c. Ilium
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Small Intestine
Modifications
- plicae
- villi
- (in man, microvilli)
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Plicae
- i. Circular arrangements of mucosa, or pleated arrangement of mucosa in wall of small intestine
- ii. Unlike rugae, which is irregular, the mucosa is pleated
- iii. It can stretch out when food is in it
- iv. Increase SA of the lumen
- 1. Distension; increase SA when food in it
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Villi
- i. Simple columnar epithelium (in humans) is thrown into clown collar; undulating layer
- ii. Fingerlike projections
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Microvilli
- i. At the luminal border, there is an increased surface area on the villi
- ii. Each cell of mucosa, at least in man, has the microvilli
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Large Intestine
Functions
- 1. Some absorption of material (limited)
- a. Most is water
- i. Very important amount of water absorbed by our colon
- b. Vitamins
- c. Drugs
- d. NO NUTRIENTS ARE ABSORBED BY LARGE INTESTINE
- THAT TAKES PLACE IN SMALL INTESTINE
- 1. Formation of waste product: feces
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Large Intestine (colon)
Structure
- 1. Structure depends on vertebrate
- a. Usually one large intestine
- b. When we get down (in mammals)
- i. Cecum (blind pouch)
- 1. Coming off it is a very small gland called the appendix
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What does the large intestine consists of?
blind pouch (cecum) with appendix coming off of it
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Prole of apendix and cecum
- 1. Appendix plays no role iin man, but in early vertebrate form it does
- ii. In some vertebrates, ceca have a digestive role, but in man, they don’t
- iii. Usually associated with large intestines
- 1. Some animals have a lot, but man only has one
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Size of LI
short but large in diameter
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End of the large intestine
- 1. cloaca/ anus
- a. Means sewer
- i. Cloaca used for opening of digestive, excretory, and reproduction
- 1. Liquid waste, solid waste, and gametes
- b. Anus:
- i. Just for solid waste= digestive
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