What are the four steps of obtaining energy from food?
4. Waste Elimination
What is the difference between an incomplete and complete digestive system?
incomplete digestive system: food comes out same place it went in
complete digestive system: one full continuous tube
Why have human's teeth gotten smaller over time?
use of fire and tools to cut up meet and make it smaller
What is special about cichlids?
they have undergone adaptive radiation because of variations in pharyngeal jaws and ability to eat different things
In terms of teeth, humans and mammals are ________.
generalists (have incisors, canines, premolars, molars)
Describe the jaws of a carnivore.
bite force is driven by a fulcrum (allows for full force, like scissors)
Describe the jaws of an herbivore.
since herbivores don't need a substantial bite force, they're chewing is driven by a lever force that allows for grinding
What are the benefits of a complete digestive tract?
one-way flow allows for continuous digestion, specialization of various organs, efficiency
What are the two types of muscles in the Esophagus?
skeletal muscles at top, smooth muscles at bottom
How long does it take for food to get from mouth to stomach?
What happens in the mouth?
increase size of surface area of food particles; saliva begins to break down carbohydrates and lipids; salivary glands supply lubricating mucus
What is responsible for beginning to digest carbohydrates in the mouth?
What is responsible for beginning to digest lipids in the mouth?
What is digested in the stomach?
only proteins start to be digested
What is digestion?
breakdown of food into small enough pieces to allow for absorption
What is absorption?
the uptake of specific ions and molecules that act as nutrients
What is the pH in the lumen of the stomach?
can be as low as 1.5
What are the muscles called that seal off the stomach from esophagus and small intestine?
What does the stomach do?
mechanical breakdown of food and partial digestion of proteins
What are the two types of specialty cells in the stomach?
chief cells and parietal cells
What do parietal cells do?
have a membrane spanning proton-ATPase that pumps out protons, in combination with Cl ions that have diffused out, these cells make Hydrochloric (stomach) acid
What do chief cells do?
chief cells secrete zymogen granules containing pepsinogen, the inactive form of the pepsin
How does pepsinogen turn into pepsin?
acid conditions in stomach convert it into pepsin (it prefers a pH of 1.5-2)
What is the start of the small intestine called that connects to the stomach?
75% of people who have peptic ulcers actually have....
an infection of Helicobacter pylori
The small intestine cannot handle low pH conditions, so how does the lumen neutralize the pH?
the pancreas secretes tons of bicarbonate buffer
What is the lumen of the small intestine similar to? (think water regulation)
rectal gland of a shark
How does the lumen of the small intestine work?
it pumps sodium into blood so that water and glucose will be pulled out of lumen (via sodium re-entry)
Where is amylase secreted from?
What does amylase break down?
How does the small intestine increase surface area?
folds, villi, and microvilli
What are essential amino acids?
8 (out of 20) amino acids that are required to manufacture proteins, but that cannot be synthesized by humans (we can synthesize the other 12)
What are vitamins?
carbon-containing molecules that function as coenzymes
What are electrolytes?
form ions in solution, influence osmotic balance and are required for normal membrane function
What are essential elements?
cannot be synthesized by the body, but they serve a wide variety of functions
What do salivary glands produce?
water and glycoproteins called mucin (together they create mucus)
In birds, what allows for the storage and digestion of foods?