Animal Nutrition : Animal Nutrition
We need to eat! : We need to eat! Since we as animals cannot produce our own food, we must EAT it.
Classifying organisms by what they eat…
Herbivores: eat autotrophs
Carnivores: eat other animals
Omnivores: eat both autotrophs and animals
Classifying Animals by HOW They Get Their Food : Classifying Animals by HOW They Get Their Food Suspension feeders:
Sift small food particles from the water
Examples: clams, oysters, whales
Substrate feeders:
Live on (or in) their food source
Example: leaf miners, eat their way through leaves
Deposit feeders:
A type of substrate feeder
Eat partially decayed organic material in soil
Classifying Animals by HOW They Get Their Food : Classifying Animals by HOW They Get Their Food Fluid-feeders
Suck nutrient-rich fluids from a living host
Example: mosquitoes, hummingbirds
Bulk-feeders
Eat relatively large pieces of food
That’s us!
The 4 Stages of Food Processing : The 4 Stages of Food Processing Ingestion
The act of eating
Digestion
The process of breaking down food into molecules small enough for the body to absorb
This involves hydrolysis, which you should know well
This has to occur in a specialized compartment… why??
The 4 Stages of Food Processing : The 4 Stages of Food Processing 3. Absorption
The animal’s cells absorb the small molecules broken down during digestion
4. Elimination
Undigested material passes out of the digestive compartment
Gastrovascular Cavities : Gastrovascular Cavities Gastrovascular cavities are the digestive systems in simple animals
GCs have only one opening, and there is only one “part” of a GC
Digestion in Alimentary Canals : Digestion in Alimentary Canals Complex animals use alimentary canals, a digestive tube extending between two openings, a mouth and an anus
An “Entrance” and an “Exit”
Food travels in one direction only
Mouth = site of ingestion
Anus = site of elimination
Alimentary Canals : Alimentary Canals
The Mammalian Digestive System : The Mammalian Digestive System
The Mammalian Digestive System : The Mammalian Digestive System Consists of:
Oral cavity (mouth)
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
Food moves through the digestive system by peristalsis, rhythmic waves of contraction by the smooth muscles
Oral Cavity : Oral Cavity The mouth
Chewing cuts, smashes, and grinds food to facilitate swallowing
Saliva is secreted into the mouth by the salivary glands
Saliva contains salivary amylase
This enzyme breaks down starch and glycogen into smaller pieces
Pharynx : Pharynx The pharynx is the intersection that leads to both the esophagus (digestive system) and the trachea (respiratory system)
The epiglottis makes sure that food doesn’t enter the trachea
Esophagus : Esophagus The esophagus carries food from the pharynx into the stomach
Stomach : Stomach Our stomachs are stretchy – they expand to fit our food!
The inside of the stomach contains gastric juice, which has a pH of about 2
HCl – kills most bacteria swallowed with food
- breaks down cells in meat and plant material
Pepsin – breaks down proteins
Because the smooth muscle of the stomach and enzymes churn and break up your meal, the food becomes a nutrient broth known as acid chyme
Stomach : Stomach The pyloric sphincter closes off the stomach from the small intestine, the next stop on our tour
The pyloric sphincter lets in small amounts of acid chyme at a time
Small Intestine : Small Intestine Most digestion and absorption occurs in the small intestine
In humans, the small intestine is about 6 meters long
It’s called the “small intestine” because it has a small diameter
Small Intestine : Small Intestine First section of the small intestine is the duodenum responsible for digestion
Acid chyme enters from the stomach
Pancreatic enzymes (hydrolytic) enter
Bile (produced in the liver, stored in the gall bladder) enters
Bile contains bile salts which aid in digestion and absorption of fats
Small Intestine : Small Intestine Carbohydrates are broken down (digested) by amylases from the pancreas
Proteins are broken down (digested) by trypsin
DNA and RNA are broken down by nucleases
Fats are broken down by bile salts from the liver and lipase
Small Intestine : Small Intestine The digestion occurs in the duodenum
The absorption of nutrients occurs in the jejunum and ileum
In order to be useful to an organism, the nutrients that have been broken down must be absorbed
The jejunum and ileum (sections 2 and 3 of the small intestine) are responsible for absorbing what the duodenum digested
Small Intestine : Small Intestine The jejunum and ileum have a brush border
The jejunum and ileum have villi (that look like fingers) and microvilli
This gives them more surface area, which facilitates absorption of nutrients
More doors = faster access
The Small Intestine : The Small Intestine
Large Intestine (Colon) : Large Intestine (Colon) The major function of the colon is to reabsorb water that entered the digestive system as a solvent
The wastes of the digestive tracts are called feces, and they become more solid as they are moved along the colon
If it moves through too quickly, not enough water is reabsorbed diarrhea
If it moves through too slowly, too much water is reabsorbed constipation
The waste is stored in the rectum until it can be eliminated through the anus
The Mammalian Digestive System : The Mammalian Digestive System
Evolutionary Adaptations : Evolutionary Adaptations Evolutionary adaptations of the digestive system exist among animals, primarily based on their diet
Herbivores have less specialized teeth than do carnivores
Herbivores have longer alimentary canals than carnivores…why??
Evolutionary Adaptations : Evolutionary Adaptations
Food is our Fuel : Food is our Fuel Undernourished:
Someone whose diet is deficient in calories
Malnourished:
Someone whose diet is missing one or more essential nutrients
However, obesity is a more common dietary problem in America