digestion Flashcards
What is motility
the speed at which food moves through the digestive system
what is digestion and what three parts does it include
the chemical breakdown of food molecules by enzymes
-digestion
-absorption
-metabolism
steps of digestion (5)
1) mechanical breakdown
2) chemical breakdown
3) absorption
4) metabolism
5) egestion
What does mechanical breakdown include
1) prehension - movement of food into the oral cavity
2) mastication - chewing
3) motility - movement of food gradually through the digestive tract
What does chemical breakdown include
1) secretion
2) digestion
What is egestion
defaecation (getting rid of waste)
What is the difference between egestion and excretion
egestion is getting rid of waste products that haven’t been absorbed in the body whereas in excretion the waste products have been absorbed
What does saliva do
secretes amylase to breakdown starch and creates optimum environment for eznymes further down. Helps lubricate food going down oesophagus
What steps is the stomach involved with
motility and secretion
What is the liver/gall bladder/ pancreas involved in
secretion
What is the small intestine involved in
motility/digestion/absorption
What is the large intestine involved in
motility/fermentation/absorption/egestion
fermentation produces gases – farts
What salivary gland produces serous saliva
parotid
What glands produce mucous and serous saliva
mandibular/buccal/sublingual
What is the saliva like in simple stomached animals
mainly mucous to lubricate food passage
ph neutral for amylase action
What is the saliva like for complex stomached animals
mainly serous saliva for optimum conditions for fermentation
ph alkaline to buffer forrestomach for fermentation (carbonate)
large volme of salivary secretion
no amylase
What happens to digestive fluids released
most reabsorbed, if not causes diarrhea
How does saliva differ between herbivores and carnivores
carnivores don’t produce amylase
What components does saliva contain (8)
mucin (add water = mucus)
amylase (omnivores and horses, not ruminants or carnivores))
bicarbonate (to neutralise and buffer)
phosphate (in ruminants)
lysozymes+ antibodies (reduce infection)
protein binding tannins (digestion of cellulose_
urea (ruminants)
composition depends on species
What is the primary secretion of saliva
saliva that is first produced before it is released into the oral cavity so is still inside the gland
How does saliva osmotic effect change in non ruminants
primary secretion is isotonic with blood
at low flow rates (not eating) there is time for the minerals to be reabsorbed as it moves out of the gland so saliva becomes hypotonic
at high flow rate (eating) not enough time for minerals to diffuse so saliva is still isotonc
What happens to saliva composition for ruminants when digesting
ruminants digesting continuously so saliva is always isotonic
ruminant saliva needs to be buffered to keep rumen ph levels optimum for microbes
at low rates (not eating) PO4 is higher
at high rates (eating) HCO3 is higher
How is saliva secretion regulated
all under nervous syestem control
sympathetic causes reduction of production
parasympathetic causes increase for digestion
basal salivary secretion for oral hygeine
2 reflex pathways :
-congenital (innate)
-conditioned (learned)
What is the congenital reflex pathway of saliva
initiated by taste/smell of food in mouth
due to afferent nerves going to salivary centre in the brain and efferent nerves going to the salivary gland
(in ruminants also triggered by distension of cardia, rumino-reticular and reticulo-osmasal orficeses, swallowing and regurgitation)