Digestive system Flashcards
herbivores
eat mainly autotrophs
Carnivores
eat other animals
Omnivores
Regularly consume animals as well as plants or algal matter
Detritivores
regularly consume dead organic matter
Extracellular digestion
the breakdown of food particles outside of cells
Intracellular digestion
food particles are engulfed by endocytosis and digested within food vacuoles (sponges and single-celled species)
Four classes of essential nutrients
Essential amino acids
Essential fatty acids
vitamins
minerals
how many amino acids do animals require
20
can synthesize about half from molecules in their diet
essential amino acids
must be obtained from food in preassembled form (humans need 9)
Insufficient essential amino acids causes
malnutrition called protein deficiency
Essential fatty acids
certain unsaturated fatty acids that must be obtained from diet
deficiencies are rare
Vitamins
organic molecules required in the diet in small amounts
How many vitamins have been identified that are essential to humans
13
Two categories of vitamins
fat soluble and water soluble
Too much water-soluble vitamins
removed in the urine (unless very high quantities)
Where are fat soluble vitamins stored
In the liver and fatty tissues
can be toxic in large quantities
Minerals
simple inorganic nutrients, usually requited in small amounts
Potassium
Mineral
necessary for pH balance, water balance, and nerve function
Fluorine
Mineral
necessary for tooth and bone health
Digestion
the process of breaking food down into molecules small enough to absorb
Enzymatic hydrolysis
chemical digestion
splits bonds in molecules with the addition of water
Absorption
uptake of nutrients by body cells
Elimination
the passage of undigested material out of the digestive compartment
Path of digestion
begins in the mouth, continues through the stomach and small intestine
Where does absorption occur
mainly in the small intestine
where does elimination occur
the rectum, waste leaves through anus
The first stage of digestion is
mechanical
salivary glands
deliver saliva to lubricate food.
salivary amylase
initiates breakdown of glucose polymers
Tongue’s role in digestion
shapes food into a bolus and provides help with swallowing
pharynx
The region we call our throat
a junction that opens to both the esophagus and the trachea
Peristalsis
rhythmic contractions of muscles in the wall of the canal that help move food
sphincters
valves that regulate the movement of material between compartments
The stomach
stores food and secretes gastric juice, which converts a meal to acid chyme
gastric juice
converts a meal to acid chyme
Mucus
protects the stomach lining from gastric juice
How often are cells renewed in the stomach lining
Every 3 days
Bacterium Helicobacter pylori
causes gastric ulcers (lesions in the lining)
What is gastric juice made of
hydrochloric acid and the enzyme pepsin
Enzyme pepsin
digests proteins
Parietal cells
secrete hydrogen and chloride ions separately
Chief cells
secrete inactive pepsinogen, which is activated to pepsin when mixed with hydrochloric acid in the stomic
Pepsinogen
activated to pepsin when mixed with hydrochloric acid in the stomach
Pancreas
produces proteases trypsin and chymotrypsin, protein-digesting enzymes that are activated after entering the duodenum
How does the small intestine help digestion
bile aids in the digestion and absorption of fat
the major organ of digestion and absorption
where is bile made
the liver
where is bile stored
the gallbladder
what is the longest section of the alimentary canal
the small intestine
What is the small intestine composed of
duodenum, jejunum, and the ilium
what is the colon of the large intestine connected to
the small intestine
Cecum
In the large intestine
aids in the fermentation of plant material and connects where the small and large intestines meet
appendix
extension of the human cecum, plays a minor role in immunity
