1. BY: Shelbi, Megan, Bonnie, and Shivali
Digestive System
BY: Shelbi, Megan, Bonnie, and Shivali

2. Diversity among Animals
Main Types:
Suspension feeders ex: Baleen Whales
Substrate feeders ex: Caterpillars
Fluid feeders ex: Mosquitoes
Bulk feeders ex: Constrictors
Their digestive systems are modified according to their food source.

3. Blood Glucose Fluctuation
When food is digested the blood glucose level rises causing the pancreas to secrete insulin into bloodstream
Insulin facilitates absorption of glucose into body cells, thus as it is stored as glycogen the blood glucose level drops
Pancreas then secretes glucagon, which opposes the effect of insulin, glucagon then promotes breakdown of glycogen within the cells and the release of glucose into the blood increasing the blood glucose level.
This system allows individuals to pull from the glycogen stores if food becomes scarce.

4. Appetite Regulation
Leptin: produced by fat tissue, appetite suppressant
Ghrelin: secreted by stomach wall, triggers feelings of hunger
Insulin: secreted by pancreas upon rise in blood sugar, can suppress appetite
PYY: secreted by small intestine, appetite repressor
Proper balance of these can keep people at a stable weight

5. Essentials
Lacking in any of the eight essential amino acids results in malnutrition
Methionine, Valine, Threonine, Phenylalanine, Leucrine, Isoleucine, Tryptophan, Lysine
There are also essential vitamins, and fatty acids (those with double bonds)

6. Organs of Digestion

7. Swallowing Reflex

8. The Stomach
Contains gastric juice: mixture of hydrochloric acid (from Parietal glands), mucus (mucus cells), and pepsinogen (from chief cells)
Stores food and performs preliminary steps of digestion
Smooth muscle churns contents every 20 seconds, results in acid chyme

9. Small Intestine reaches up to 21ft when stretched out
- small in diameter when compared to the large intestine
The longest section of the alimentary canal (digestive tract)
Location where of most of the enzymatic hydrolysis of food macromolecules and most of the absorption of nutrients into the blood occur.

10. Composed of three sections
duodenum- enzymatic action
jejunum- finalizes the food digestion process, absorbs nutrients and water
ileum- absorbs nutrients and water

11. Duodenum: Enzymatic Action
Where acid chyme mixes with digestive fluids from other organs
Bicarbonate from the alkaline solution produced by the pancreas acts as a buffer, offsetting the acidity of the chyme
Pancreatic proteases (protein-digesting enzymes) are activated once they are located in the duodenum’s extracellular space.

12. Bile
Mixture of substances that is stored in the gallbladder which then releases the bile into the duodenum as needed
Produced by the liver
Bile salts
-act as detergents to aid in the digestion and absorption of fats

13. Enzymatic Digestion Brush border- epithelial lining
-Contains digestive enzymes
Enzymatic digestion is completed as the mixture of chyme and digestive fluids is transported along the small intestine.
The jejunum and ileum sections of the small intestine function mainly in the absorption of nutrients and water.

14. Types of Digestion Carbohydrate digestion-
-Polysaccharides and disaccharides to monosaccharides
Protein digestion-
-Proteins to amino acids
Nucleic acid digestion-
-DNA, RNA to nitrogenous bases, sugars, and phosphates
Fat digestion
-Fat globules to glycerol, fatty acids, and glycerides

15. Absorption of Nutrients
Large folds in the lining of the small intestine
Villi- fingerlike projections
-Increase surface area of the lining to increase nutrient absorption
Microvilli-
-Cover the villi, increasing the surface area even more
Capillaries penetrate the core of each villus
Nutrients are absorbed across the intestinal epithelium and unicellular epithelium to capillaries or lacteals
-Lacteal- small vessel of the lymphatic system
-Make up the second layer of epithelial cells that separate nutrients in the lumen from the blood stream.
The surface area of the villi and microvilli is about the same as the area of a tennis court.

16. Small Intestine Structure

17. Large Intestine
Colon
Connected to the small intestine in the form of a T
The cecum (one arm of the T) contains the appendix, a useless appendage.

18. Role of the Colon:
To recover water that has entered the alimentary canal as the solvent of the various digestive fluids.
Reclaims much of the 7 L of water secreted into the lumen each day that was not absorbed by the small intestine.
Feces- wastes of the digestive tract
-as they are moved slowly down the colon, they become more solid
Bacteria live in the colon, such as Escherichia coli (E coli).
-intestinal bacteria live on unabsorbed organic material
-bacteria produce gases and vitamins
Rectum- the terminal portion of the colon
Between the rectum and the anus are two sphincters, one voluntary and one involuntary.
Elimination of digestive waste is caused by contractions of the colon

19. Dental Adaptations Dentition reflects the diet of an animal
Nonmammalian vertebrates have less specialized dentition
-Poisonous snakes have fangs to inject their prey with venom
-Snakes swallow their prey whole
Further adaptations exist for:
-Carnivores
Cats (meat)
-Herbivores
Horses (vegetation)
-Omnivores
Humans (vegetation and meat)

20. Carnivores:
-pointed incisors and canines to kill prey and cut flesh
-jagged premolars and molars crush and shred food
Herbivores:
-teeth with broad, rigid surfaces that grind tough plant material
-incisors and canines are modified for biting off vegetation
Omnivores:
-32 permanent teeth
-beginning at the middle line of
the upper and lower jaw are:
2 incisors for biting
1 pointed canine for tearing
2 premolars for grinding
3 molars for crushing.

21. Stomach and Intestinal Adaptations
Length of vertebrate digestive system is correlated
with its diet
Herbivores and omnivores:
-longer alimentary canals relative to their body size
vegetation is harder to digest because of the cell walls
a longer tract allows more time for digestion and more surface area for nutrients to absorb
Carnivores:
-large, expandable stomachs

22. Symbiotic Adaptations:
animals don’t produce enzymes that hydrolyze cellulose
vertebrates house symbiotic bacteria and protists in fermentation chambers in their alimentary canals
the bacteria have enzymes that can digest cellulose
The cellulose in converted into simple sugars, as well as vitamins and amino acids
depending on the animal, the symbiotic microbes may vary in their location within the digestive tract
thus most nutrients made by bacteria in the large intestine are never absorbed
Some rodents recover these nutrients by eating some of their feces and passing the food through their system twice.

23. Ruminants:
An animal with an elaborate, multicompartmentalized stomach specialized for a herbivorous diet.
Stomach has four chambers
The diet a ruminant absorbs is much richer than the grass the animal originally ate.
-rumen- where the food goes when the cow first chews and swallows
-reticulum- the cow periodically regurgitates and rechews the “cud”
-omasum- the cow
reswallows the cud,
and water is absorbed
-abomasum- the cud
passes here for
digestion by the cow’s
own enzymes.