digestion Flashcards
4 groups of nutrients
carbohydrates,
proteins,
lipids,
vitamins and minerals
how many vitamins and minerals are there
13 vitamins and 15 minerals
3 animal feeding strategies
filter feeders,
detritivore,
fluid feeders
3 different digestive specialisations
carnivore,
herbivore,
omnivore
4 stages of a generalised digestive system and what happens in each
- motility - mixes and propels digestive contents forwards
- secretion - of digestive enzymes, under neuroendocrine control
- digestion - sequential hydrolysis of complex molecules
- absorption - uptake of simple absorbable units, water, vitamins and electrolytes via specialised epithelia transporters
what animals have the simplest digestive structure where the mouth and anus are the same
Ctenophora, Cnidaria and Platyhelminthes
what animal has a digestive system which is a simple line
hagfish
what unique structure is found in a gar’s digestive tract
pyloric cici
what unique structure is found in a shark’s digestive tract
spiralised intestine
what unique structure is found in a chicken (and other bird’s) digestive tract and what is it for
‘crop’ to store digestive material
what do fish have that show the beginning evolution of the pancreas
pancreatic ducts
what differences lie among vertebrate digestive systems
all have same organs, but different arrangement
look different anatomically
birds have an additional glandular portion of the stomach, what is this called and what is it for
proventriculus which secretes hydrochloric acid
what is a bird’s gizzard for
grinding of food
what 2 intrinsic nerve plexuses make up the enteric nervous system
myenteric plexus and submucous plexus make up the enteric nervous system
what extrinsic nerves are responsible for digestive system regulation
autonomic (parasympathetic) nervous system including vagus nerve
what is the role of the mouth and what enzymes are released
grind food and mix with saliva
saliva lubricates bowla (food mass) allowing it to pass smoothly down oesophagus
saliva has amylase to begin digestion
how is swallowing achieved
waves of peristatic muscular contraction
what is the role of the stomach
stores ingested material,
kill microorganisms
what is used in initial digestion occuring in the stomach
chyme
3 types of gastric exocrine secretory cell and what do these release
parietal cells - hydrochloric acid and intrinsic factor
chief cells - pepsinogen
mucus cells - mucus is protective layer against HCl
how is pepsinogen converted to pepsin
hydrochloric acid
how are gastric pits formed and what do they contain
deeply infolded mucosa containing gastric gland cells at base
3 types of gastric endocrine / paracrine secretory cells and what do they do
histamine - promote HCl secretion,
gastrin - promote HCl secretion,
somatostatin - decrease HCl secretion
2 pancreatic proteolytic enzymes
trypsinogen (trypsin),
chymotrypsinogen (chymotrypsin),
procarboxypeptidase (carboxypeptidase)
what is the name for the combine pancreas and liver in invertebrates and fish
hepatopancreas
why are pancreatic proteolytic enzymes sencreted as their inactive forms
to prevent self-digestion of cells secreting them
what other enzymes does the pancreas release
amylase, chitinase and lipase
what type of control are enzymes released in the pancreas under
negative feedback / hormonal
what makes up the biliary system
liver, gallbladder and ducts
what does bile contain
bile salts, cholesterol and lecithin
what is the role of bile salts
aid fat digestion and absorption
fats are hydrophobic so are broken down into smaller droplets by bile salts
what adaptations does the mucosal lining of the small intestine have
maximised surface area and specialised transport mechanisms
what is the role of the brush border in the small intestine
final carbohydrate and protein digestion
how does vitamin absorption occur
via micelles or via specialised transporters
what is an indirect benefit of Na+ / K+ active transport
water uptake by diffusion
what steps are involved in lipid absorption
- micelles freely diffuse into cell and become triglycerides
- coated in lipoprotein and become chylomicrons
- pass into lymphatic system, not blood
what happens to most absorbed nutrients from the small intestine
immediate processing in liver
what are the roles of the liver
metabolic processing
detoxification
what is the role of the large intestine
storage of excreted material
microbiota
what minerals are absorbed in the large intestine
active Na+ absorption and passive uptake of Cl- and water
what is rumination
regurgitation followed by further grinding
what occurs in the rumen
microbial digestion,
fermentation of carbohydrates,
protein hydrolysis
what is the name for the true stomach in ruminants
abomasum - site of acid secretion
