Chapter 13 Part 7 Flashcards
What are the proventriculus and the gizzard?
- found in birds
- Pieces to a 2-part stomach
Gizzard
Muscular part of stomach
Grinds and softens food, takes part of teeth, Birds have no teeth!!
More musucular in birds who eat seeds, birds often swallow rocks to help; Thick keratinized parts in muscle to help break down hardy foods
Glands within the gizzard secrete a protective, leathery lining called gastric cuticle or koilin, a mixture of carbohydrates and proteins
the muscular lower part of the avian two‐part stomach that grinds and softens food, often with the aid of stones held within the gizzard
Ingest pebbles and gravel to augment this grinding process
Proventriculus
- secrete digestive enzymes(HCL, pepsin), initial digestion stage
- moves food from crop to gizzard
Why is fermentation of plant material necessary?
Vertebrates cannot digest cellulose
2 adaptations for cellulose digestion:
gastric(forgut) fermentation
hindgut fermentation
Gastric (forgut) fermentation
mammals and reptiles evolved, modified stomach that becomes chamber for fermentation for plant material mixed with microbacteria, etc.
Example: Ruminantia (giraffes, deer, antelope)
· Specizlied four chamber stomach
· True stomach has gastric glands, where enzymes secreted
Name the steps of fermentation
In ruminants, food is clipped, rolled into a bolus, mixed with saliva, and swallowed
Contractions spread through rumen and reticulum in cycles that circulate and mix the digesta
Contents separate into fluid and particulate material
Floating, fibrous plant material and a pocket of gas form during fermentation
Poorly masticated plant material regurgitated and rechewed later to break down fibrous cell walls mechanically and expose further plant tissue to cellulases
Omasum transports reduced digesta from the reticulum to the abomasum
First, relaxation of walls produces negative pressure that draws fine particulate material from the reticulum into its own lumen; Next, contraction of the omasum forces these particulates into the abomasum, the stomach region rich in gastric glands; The abomasum is the first true part of the stomach
Cycle repeated multiple times often
Villi
- part of intestines
- project above the level of the mucosal wall; intestinal glands are sunken within the mucosal wall
- blood vessels, arteries, veins for absorption of nutrients from substances being broken down inside the gut itself
Describe villi in different parts of intestines
- Duodenum and jejum have lots of internal surfaces with villi that help with broken down substances
- Getting into large intestine, it becomes more simple; mostly absorbs water
What is the spiral valve and in which vertebrates is it found?
o Most fish have structure called spiral valve
o Sharks, chimeras
o Spiral valve: increases surfaces area inside intestine for things getting broken down, for digestion
o Sturgeon: spiral valve
Do teleosts have a spiral valve?
No! They have coiled intestines
Generally speaking, how does gut length vary in tetrapods?
length increases as body size increases generally
Organisms with relatively short, unspecialized intestines
o Amphibians, snakes, caimans, forest chameleons, and red-tailed hawks
How do you prolong digestion
various specializations occur, such as the spiral valve of the bowfin, ceca of some herbivores, or the double ceca of the grouse and rhea
o Herbivores have more elaborate structures (cecum, double cecae, etc.)
o Double cecae: for fermentation of plant material
pyloric ceca
- are finger-like pouches found in the digestive system of many fish species
- increases surface area for nutrient absorption, secrete digestive enzymes, and participate in fermentation (of plant materials)
