exam 2 Flashcards
anatomy/physiology
digestive system
long tube beginning w/ mouth, ending w/ anus
what happens in digestive system
- large complex molecules break down to simpler molecules (digestion)
- simpler molecules cross cellular lining (absorption)
absorption
simpler molecules cross cellular lining
digestion
large, complex molecules break down into simpler molecules
functions of GI tract
digestion & absorption
GI tract
gastrointestinal tract
four major digestive systems
ruminant, monogastric, modified monogastric, avian
ruminant
4 compartment stomach
EX. sheep, cattle
monogastric
1 simple stomach, extensive intestines
EX. swine, humans
modified monogastric
1 stomach w/ extensive intestinal system & enlarged cecum
EX. horses, rabbits
avian
begins w/ mouth, includes several unique structures before ending at cloaca
EX. poultry, various birds
mouth (prehension tool)
- grasps and chews food
- breaks down food particles
salivary glands
- mouth
- secrete juices containing enzymes to begin digestion (limited w/ horses)
bolus
- mouth
- chewed up food covered in saliva formed
- soft cohesive mass of food, saliva, enzyme
structures of mouth
- lips, beak, teeth, tongue
- varies in species
ruminant mouth
- dental pad
- no top teeth
- cattle use tongue (graze)
- sheep use lips (graze)
- limitedly chews –> regurgitate and re-masticate (chew) food
why can sheep access higher quality feed in the same pasture [as cows…]?
they can eat until the root which has more nutrient since it is fresher, young plant material
but it can cause added parasite risks
avian mouth
- uses peck to grab food
4 functions of saliva
- lubricate and binds bolus to prevent esophagus damage
- aids in taste reception by solubilizing
- contains digestive enzyme for starch (not horses, small amt in carnivore/cattle)
- acts as a buffer to normalize pH (important ruminants!!!!)
esophagus
- muscular tube connects mouth to stomach
- smooth muscle contracts rhythmically causing contents to move (peristalsis)
- muscle contraction controlled by CNS
peristaltic movement
- sequential contraction of ring-like muscles
- happens at 0 gravity to varying degrees (even if animal upside down)
reverse peristalsis
vomiting/cud (not horses!!)
esophagus monogastric
tube to transport bolus (swallowing) to GI tract to stomach
esophagus ruminant
tube to transport bolus (swallowing) to GI tract to reticulum/rumen
esophagus avian
tube to transport bolus (swallowing) to GI tract to crop
esophageal sphincter
end of esophagus, one way ring of muscle that relax to allow food to enter stomach
rumination
cud chewing. reverses action
stomach
- muscular contractions break down food
- gastric glands inside stomach wall
- very acidic pH, inactivates salivary amylase
- stomach protect itself from acid w/ mucus
gastric glands in stomach
- secretes digestive juices (HCl & powerful/pro-enzymes)
gastric enzymes
pepsin and rennin (young) begin to break down proteins
enzymes
end in “-ase” and act on other form…
EX. cellulase = cellulose, lipase = lipid
small intestine sections
- duodenum
- jejunum
- ileum
small intestine & functions
- long coiled tube connecting stomach to large intestine (3x body length)
- surface covered w/ intestinal villi
- majority of digestion by enzymatic action
- absorption of AA, monosaccharides, lipid components
approximately 90+% of digestion and all absorption occurs in SI which requires LOTS of surface area. how is this achieved?
- muscular folds also serves to mix feed
- villi (villus = 1) increases surface area & absorption
- microvilli (brush border membrane) contains enzymes and improves absorption bc surface area
villi
tiny, fingerlike protrusions along the walls of small intestines
- takes in units of carbo, pro, lipids, vits, and some water/mins through enterocytes
duodenum
- Brunner’s gland secretes alkaline mucuous (protects DDN from acidic chyme, provides alkaline env to activate enz, and lubricates intestinal walls)
- receives secretions from pancreas & liver via ducts
- bile emulsifies fat
- protein digestion continues
- Fe absorption
jejunum
- long villi & more microvilli
- enzymatic digestion continues
- main site in SI of absorption for CHO + proteins
ileum
- short in most livestock
- absorbs B12 + bile salts
- absorption of fat/fat soluble vitamins
- absorption of remaining nutrients
- microbial population growth starts
SI intestinal walls
made up of smooth muscle that contract & relax, moves food or chyme forward then slightly backward
pancreatic duct
bile & pancreatic juices dumped through duct into duodenum
pancreas (acc organ)
- secrete enzymes to act on protein, CHO, fat
- secretes & dumps alkali containing juice to help BUFFER (counteract) HCl acid from stomach and digest
why is alkali containing juice to help buffer HCl acid from stomach and digest important?
to prevent villi of small intestines from being damaged and prevent ulcerations
liver (acc organ)
- secretes bile (stored in gallbladder)
- metabolic regulator/nutrient metabolism
- waste product removal
- nutrient storage (iron, vits, glycogen)
- drug inactivation
how does the bile secreted in the liver aid in fat digestion and absorption?
bile breaks it up, lipase attacks, breaks down fat into… makes it more accessible to absorb
large intestine
- final digestive structure, most nutrients absorbed by the time chyme/digested food reach it
- no villi
- minerals absorbed
- microbial digestion occurs in cecal fermenters
sections of large intestine
- cecum
- colon
- rectum
primary role of large intestine
convert chyme into feces for excretion
colon (LI)
the colon absorbs water from the chyme, changing it from liquid to solid
pregastric (cecal fermentation)
fermentation that occurs in the rumen of ruminant animals. occurs before food passes into small intestine [ruminants]
postgastric (cecal fermentation)
fermentation of feed occurs in cecum behind SI [cecal fermenters: horse]
rumen (paunch) - ruminant digestive system
- largest compartment
- located on left side of abdomen
- primarily anaerobic
- lined w/ papillae (inc surface area)
- several strong muscular pillars (not solid, made up of old roughage) that divides rumen and contracts to mix and partition feed
what do the strong muscular pillars do in the rumen that are made up of old roughage?
they divide the rumen and contract to mix and partition the feed
functions of rumen
- storage
- soaking
- microorganism home
microbe functions
- fermentation of carbohydrates
- synthesis of vit B12
- microbial protein
reticulum (hardware stomach) - ruminant
- located next to heart
- honeycomb appearance
- no enzyme secreted
why is the reticulum called the hardware stomach?
bc it collects foreign material such as nails, wire, plastic, etc
omasum (buchers bible) - ruminant
- many piles (folds) that prevent feed from leaving rumen if too large
- removes fluid
- traps food particles until size is reduced
- no enzymes from walls
why is removing fluid in omasum important?
bc feed that is passing is very liquidly which can cause enzymes to be dilute that are in the abomasum
abomasum (true stomach) - ruminant
- same function as glandular stomach of monogastrics
- digestion by gastric secretions from walls (such as HCl acid + enzymes.. pepsin/rennin)
- secretes enzymes from walls
- mucin (mucus) protects lining from being digested
rumination (cud chewing)
- decreases particle size for better microbe/enzyme action
- increases saliva production to buffer rumen
- amt of ruminant depends on fiber content of diet
- controls intake/gain or productivity
- feed should be <1mm before leaving rumen
what is the relationship between microbial organisms & animal?
symbiotic - both sides benefit
what do microbes get in reticulorumen environment from animal that make it an ideal place for microorganism?
- constant temperature
- moist environment
- anaerobic environment
- feed provides substrate (food)
- end products removed
what do ruminants get in reticulorumen environment from microbes?
- ability to digest fibrous feeds
- can change poor quality to higher quality protein
- some vitamin production
what are the microbe types?
bacteria, protozoa, fungi
bacteria
biggest component, smallest size
protozoa
larger but fewer in number
fungi
the type and number of rumen microorganisms depend on what?
- feed composition (forage vs concentrate)
- level of intake (correlation w/ population)
fibrous feeds are more efficiently digested by what?
fibrous feeds are more efficiently digested by rumen microbes than in LI (cecum)
true or false: cellulase & hemicellulose are microbial enzymes
TRUE
dietary upset
too much grain too quickly
what does dietary upset cause?
it causes rapid change in microbial population which greatly affects fiber digestion
why is milk bypassing the rumen beneficial?
the ruminant animal gets the ability to improve protein quality
rumen in young ruminants
sterile at birth
young ruminant abomasum
much larger that allows them to rely on milk for more nutrients
young ruminant inoculation
through environment and saliva
reticulo-rumen - young ruminants
grows w/ fibrous feed introduction & as the animal grows
esophageal/reticular groove - young rum
during nursing/bucket feed, milk bypass rumen & goes directly to abomasum via esophageal groove
what does reflex action(ex. calf nursing) prevent when it closes the esophageal groove to form a tube-like structure?
reflex action prevents milk/milk replacers from entering rumen bc if calf drinks milk too fast, it may overflow into rumen
what are the disadvantages of microbial fermentation?
- all levels of protein quality end up as microbial protein
- high quality protein downgrade to intermediate
how is milk (high quality protein) protected from microbial fermentation?
it is protected by the esophageal groove bc it doesn’t go to the rumen
readily degradable carbs (sugar & starch) are covered to what and why?
converted to volatile fatty acids (VFA) to be absorbed and used as energy source
why are VFAs good and bad?
good bc it can be absorbed through rumen wall. bad bc microbes need some energy
microbial fermentation uses some consumed energy
8-10% end up as methane that need to be belched
ruminants use poor quality feed to produce milk/meat
makes feed conversion rates appear poor
