Flashcards in chapter 34 (digestive system) Deck (62)
Digestive system functions
Breaks food down into small molecules that can cross plasma membranes
Absorbs nutrient molecules
Eliminates indigestible remains
Includes all the organs, tissues, and cells involved in ingesting food and breaking it down into smaller components
Contributes to homeostasis by providing body with nutrients needed to sustain life of cells
incomplete digestive tract
has a single opening used as an entrance for food and exit for wastes
complete digestive tract
has two openings
Continuous filter feeders
Always have water moving into the mantle cavity via the incurrent siphon
Particles are deposited on gills.
Size of incurrent siphon permits entry of only small particles.
Do not need food storage area
Moves rapidly through water using jet propulsion
Uses tentacles to seize prey
Beaklike jaws pull pieces into the mouth with the radula
Food storage area needed
Stomach, with cecum, retains food until digestion is finished
differs with mode of nutrition
type, number, arrangement, set of teeth.
Eat only plants
Incisors for clipping
Premolars and molars for grinding
Land snails and some insects are herbivores.
Koalas, which are mammals, eat only eucalyptus leaves.
Grazers, like horses, feed on grasses.
Ruminants, like cattle, goats, and sheep, have a four-chambered stomach which allows them to regurgitate solid material for complete digestion.
Eat only other animals
Pointed incisors and enlarged canines
Shear off pieces small enough to swallow
Spiders and sea stars are carnivores.
Dogs, lions, and dolphins are carnivores.
The lion’s pointed canine teeth are used for
killing, sharp incisors for scraping bones,
and pointed molars for slicing flesh.
Variety of specializations to accommodate both vegetation and meat
Clams and tube worms are invertebrate omnivores.
Humans, pigs, raccoons, and most bears are omnivores.
Dentition of the above is specialized to accommodate vegetable and meat diet.
Better ability to adapt to different food sources
Human Digestive System
Human digestive tract is complete.
Part of a tube-within-a-tube body plan
Begins with a mouth and ends in an anus
Digestion is entirely extracellular.
Is mechanical as well as chemical
Digestive enzymes are secreted by
The wall of the digestive tract
Nearby accessory glands
Where digestion begins
Composed of striated muscle and an outer layer of mucous membrane
Mixes chewed food with saliva
Forms mixture into a bolus
Digestive and respiratory passages come together in the pharynx, then separate.
Soft palate closes off nasopharynx during swallowing
Covers the glottis (opening into the trachea)
Keeps food from air passages (most of the time)
Moves food to stomach by peristalsis
Peristalsis – Rhythmical contraction to move contents in tubular organs
Stomach wall has deep folds (rugae)
Folds disappear as the stomach fills to an approximate volume of one liter.
Epithelial lining of the stomach has millions of gastric pits, which lead to gastric glands.
about 2.0, which can kill bacteria in food
is a hydrolytic enzyme that acts on protein to produce peptides.
secrete hydrochloric acid (HCl) and pepsin
what protects the stomach wall from enzymatic action.
A layer of mucus
in the stomach When gastric acid leaks upward
the mucosal lining can be irritated.
Gastrointestinal reflux disease can cause heartburn
happens when Food mixes with gastric juices
are ridges on the surface, which contain even smaller ridges called microvilli.
Contain digestive enzymes called brush-border enzymes
Greatly increase the surface area for absorption
what is in the wall of the small intestine
lacteal (lymphatic capillary)
blood capillaries in the villus
large intestine has what pertaining to bacteria?
has a large population of bacteria that break down indigestible material and produce vitamins.
Lies deep in the abdominal cavity