Exam 2 Flashcards
Alimentary organs
mouth esophagus stomach small intestine large intestine anus
accessory organs
tongue teeth salivary glands liver pancreas gastric glands intestinal glands
factors promoting digestion
mechanical
secretory
chemical
microbial- bacteria and protozoa
mechanical
mastication, deglutition, regurgitation, gastric motility, intestinal motility, defecation
secretory
saliva, gastric secretions, mucus secretions, digestive glands
chemical
enzymes, HCl
microbial- bacteria and protozoa
especially true for ruminants; large intestine
wall of intestinal tract has four layers
- mucosa
- submucosa
- muscularis
- serosa
mucosa
inner lining
submucosa
connective tissue, blood vessels, lacteal (lymph), nerves
muscularis
mixing and movement; also contains nerves
serosa
smooth outside covering
mucosa layer of stomach is subdivided into four zones
- cuticular region (non-glandular)
- cardiac gland region (mucus)
- fundic region (mucus, HCl, and enzymes)
- pyloric region (mucus)
gastric glands are sometimes called ___
oxyntic glands
gastric glands are located in the ___
fundic gland region
Gastric glands
- mucous neck cells (secrete mucus)
- parietal cells (produce HCl)
- chief cells (produce gastric enzymes)
B12 is not found in ___, only in ____
plants; animal proteins
parietal cells produce…
HCl and Intrinsic factor.
intrinsic factor
glycoprotein necessary for Vit B12 absorption. It binds to B12. Absorption occurs in ileum (last section of SI)
B12 absorption may be decreased by…
- lack of intrinsic factor (aging, gastritis, or the partial removal of stomach; decreased HCl secretion- parietal cell problems) ; ileal resection or ileitis; deficiency of B12 in diet.
small intestine divided into three parts
duodenum
jejunum
ileum
two sets of muscles in SI
- circular: cause peristaltic movements
- longitudinal: aid peristaltic movements
main functions of small intestine
- move chyme along its course
- continued digestion of chyme by secretions and enzymes secreted by the accessory glands and the SI’s own intrinsic factor
- absorption of nutrients into blood and lymph vessels
chyme
semi-liquid, pulpy material produced by the action of gastric secretions in the stomach
villi and microvilli
surface anatomy of SI. Microvilli is also called the brush border and are on epithelial cells. These folds increase surface area. The main folds increase it by 3. Villi with epithelial cells increase it by 10. And microvilli increase it by 20. Combined surface area is 600X greater than just a round tube
___ of blood in liver enters through ____; and ___ enters through ___
80% through portal vein; 20% through hepatic artery
large intestine
- absorption of water and little minerals
- very few secretions (mucus only significant one)
- dehydrator in many species
- no digestive secretions
- cecum, colon, rectum
- cecum of horse and rabbit enlarged for microbial fermentation that permits utilization of forage
- sows on pasture also have enlarged cecum and significant microbial fermentation
three main pairs of salivary glands
- parotid: below ear
- submaxillary: base of the mandible
- sublingual: beneath tongue
salivary amylase
- man and pig
- produced by parotid glands
- starch digestion enzyme
- starch ——-> maltose and dextrin
- deactivated by HCl in stomach
pre-gastric lipase
- from base of tongue
- produced by ruminants
- aids milk fat digestion
- also deactivated by HCl
composition of gastric secretions
- mucus
- gastric proteases
- HCl
- gastric lipase (minor importance)
protease
breaks down protein
gastric proteases
pepsin (from chief cells of fundic region) and rennin (abomasum of nursing calf)
zymogen
precursor form. if chief cells secreted pepsin in active form, you would digest your own stomach.
pepsin
- pepsinogen —(HCl)—> pepsin
- diet protein —(Pepsin)—> long chain polypeptides
rennin
- prorennin —(HCl)—> rennin
- Casein —(Rennin and Ca)—> Ca-paracaseinate (coagulated)
HCl
- activated pepsinogen and prorennin
- denatures dietary proteins
- stomach antiseptic
- promotes some hydrolysis (minor importance)
- stops action of salivary amylase
two sets of glands in small intestine
- brunner’s glands and crypts of lieberkuhn
Brunner’s glands
- in mucosa/submucosa 1st few cm of duodenum
- secrete viscous alkaline mucus
- pH= 7-8
- neutralizes acid chyme
- also aids in fat emulsification
crypts of lieberkuhn
- enterokinase: activates trypsin
- amylase: breakdown of starch (minor role)
- mucus
small intestine intracellular enzymes
- located on surface or inside epithelial cells (on microvilli)
- several peptidases (split small peptides into AA)
- disaccharidases: sugar splitting enzymes (three primary are maltase, sucrase, and lactase)
maltase
glucose + glucose
sucrase
glucose + fructose
lactase
glucose + galactose
horses do not have ___
gallbladder
liver function with respect to digestion
secretes bile which is for fat emulsification and aids in absorption of lipids and fat soluble vitamins
emulsification
breaks down fats into smaller pieces or droplets for more surface area for lipases to work with
bile
- produced continually by liver
- formed from cholesterol (major route of cholesterol excretion from body)
- stored and concentrated in gall bladder
- empties into SI when digesta (especially fats) enters from the stomach
- about 94% of bile salts are reabsorbed and recycled back to gall bladder via enterohepatic pathway
functions of bile
- emulsifies fat
- neutralizes acid
- excretes substances (cholesterol, fat soluble vitamins, drugs, toxins, some minerals)
composition of bile
- bile salts
- bilirubin
- cholesterol
- fatty acids
- lecithin
bile salts
- cholic acid and chenodeoxycholic acid
- amphipathic - solubilize fats
- micelles
amphipathic
both polar and non polar regions; part hydrophilic and part hydrophobic
bilirubin
- product of Hb breakdown
- primary bile pigment- yellow color- modified by enzymes to give brown color in feces
types of tissue in pancreas
- acinar
- islets of Langerhans
acinar
- produce pancreatic secretions
- released into duodenum
islets of langerhans
- produce hormones
- released into blood
- beta cells: produce insulin
- alpha cells: produce glucagon
pancreas secretions
- clear fluid, mostly water
- contains digestive enzymes
- contains bicarbonate to neutralize stomach acid
digestive enzymes of pancreas
- proteolytic enzymes (trypsin, chymotrypsin, and carboxypeptidase)
- pancreatic amylase
- pancreatic lipase
- cholesterol esterase
- phospholipase
trypsin
- trypsinogen —(enterokinase)—> trypsin
- trypsin, once formed, is autocatalytic
- enterokinase from crypts of lieberkuhn
chymotrypsin
- chymotrypsinogen —(trypsin)—> chymotrypsin
carboxypeptidase
- procarboxypeptidase —(trypsin)–> carboxypeptidase
endopeptidases
- act on internal bonds, specific for certain AA
- trypsin and chymotrypsin
exopeptidase
- act on carboxyl group and releases free AA
- carboxypeptidase
pancreatic amylase
- hydrolyzes starch to maltose (G-G)
- major enzyme for starch digestion
- starch = major carbohydrate in grain
pancreatic lipase
- hydrolyzes fats to fatty acids and monoglycerides
- major enzyme in fat digestion
neural control of digestion
- salivary secretions: sight of food, smell, taste, etc. excite the salivary nuclei in the CNS
- HCl secretion: stomach distention
- pancreatic secretion: fat and protein products in SI
origin of gastrin
pyloric region of stomach or abomasum
releasing mechanism for gastrin
food in stomach, especially protein, caffeine, and spices
function of gastrin
stimulates flow of stomach acid and enzymes
origin of gastric inhibitory polypeptide (GIP)
gastric antrum; duodenum; jejunum
releasing mechanism for GIP
glucose in duodenum; fats, fatty acids, bile in duodenum
function of GIP
insulin release; inhibit gastric secretion and motility
origin of secretin
duodenum; jejunum
releasing mechanism for secretin
acid chyme; large polypeptides
function of secretin
secretion of pancreatic juice and reduce gastric motility
origin of cholecystokinin
duodenum; jejunum
releasing mechanism for cholecystokinin
fat, fatty acids, polypeptides in duodenum
function of cholecystokinin
bile flow, synthesis of pancreatic juice and enzymes
places of absorption
- mouth: no absn
- esophagus: no absn
- stomach: simple stomach (essentially no absn; water, alcohol, minerals); ruminant stomach (absn of VFA, NH3, gases and some AA; some absn from abomasum)
- SI: primary site of absn
- LI: primarily water; some minerals
routes of absorption
- (hepatic) portal blood
- lymphatic system
- systemic blood
hepatic portal blood
- drains intestinal area and goes to the liver
- “portal drained viscera”
lymphatic system
- flow much slower
- services stomach and SI
- empties into blood stream through thoracic duct (bypasses liver)
systemic blood
blood that serves the entire system
mechanisms of absorption
- passive transport (simple diffusion or diffusion through channels)
- facilitated transport (or facilitated diffusion)
- active transport
passive transport
- movement of molecules from an area of high concentration to an area of low concentration (“concentration gradient”; always down a gradient)
- requires no energy from cell
- molecules must be small enough to pass through the pores of membrane
- diffusion of water across membrane is osmosis
facilitated transport (facilitated diffusion)
- most molecules cannot cross membrane by simple diffusion
- some carried across by carrier proteins embedded in cell membrane (they change shape when molecules attach to them, the change in shape enables molecule to cross membrane)
- also occurs down a gradient
- molecules move in or out of cell
- requires no energy from the cell
active transport
- cells often must move molecules up a concentration gradient (low to high)
- involves carrier proteins
- requires ATP
- carrier proteins act as pumps that use energy to move ions and molecules
mechanism of absorption example
- transport of glucose into the villus epithelial cell is by active transport; requires energy ; glucose concentration in cell is greater than in SI
- transport across the basolateral surface of the cell (into the blood) is by facilitated diffusion; glucose concentration in blood is less than cell
carbohydrates
- CHO is major supplier of energy
- make up ~3/4 of weight of feed
- starch = major CHO in grain
- cellulose = major CHO in forages
- CHO <1% of body (glucose; glycogen; glycoproteins)
Three major classes of CHO
- monosaccharides (1 sugar molecule)
- oligosaccharides (2-10 monosaccharides; includes di, trisaccharides)
- polysaccharides (can have 100 to 1000+ monosaccharides)
metabolically important monosaccharides
- trioses
- pentoses
- hexoses
trioses
- 3 C
- mostly found in metabolic pathways
pentoses
- 5 C
- small amount in plants
- usually polymers
- xylose: usually associated with poorly digested material
- ribose: component of ATP, ADP, RNA, DNA
hexoses
- 6 C
- glucose (free in blood, required by nervous system and RBC, key sugar in CHO metabolism)
- fructose (in seminal fluid: normal energy source for sperm; found in honey and ripe fruits)
- galactose (seldom found free in nature, important in structure of brain and nervous tissue)
metabolically important oligosaccharides
- maltose (glucose + glucose)
- lactose (milk sugar; glucose + galactose)
- sucrose (table sugar; glucose + fructose)
metabolically important polysaccharides
- starch
- glycogen
- cellulose
- hemicellulose
starch
- amylose (straight, unbranched chain of glucose units; a-1,4-glucosidic bonds)
- amylopectin (branched chain every 24-30 units; a-1,6-glucosidic bonds)
glycogen
- similar to starch (branch points every 8-12 units)
- liver and muscle
cellulose
- major component of plant cell walls
- straight, unbranched chain of glucose units
- b-1,4-glucosidic bonds
- strengthened by cross-linked H-bonds
- mammals: no digestive enzymes
hemicellulose
- part of cell wall of plants
- xylose units (5 C) linked b-1,4
digestion of CHO (starch)
- amylase (hydrolyzes a-1,4-glucosidic bonds; forms maltose; cannot hydrolyze a-1,6-glucosidic bond; primary end products are maltose and limit dextrin)
- maltase, isomaltase, a-dextrinase
learn transporters from notes
…
sources and fates of blood glucose
- there are several needs that are met by blood glucose
- liver glycogen
- muscle glycogen
- tissue oxidation
- fat formation
feeding- what happens after you eat?
- dietary glucose enters blood
- some glucose used by liver to replenish liver glycogen supply
- other glucose goes to muscle and other extra hepatic tissues
- after in blood, 3 things can happen (energy production (1st), muscle glycogen, fat synthesis (last))
AA structures
…
composition of proteins
- contain C, H, O, N (15-19%), S and P
- mean N content of feed = 16%
- 100/16 = 6.25 (Kjeldahl CP)
- % N x 6.25 = % CP
- primary dry matter constituent of body organs
protein requirements as % of diet
- as a percent of diet, the amount of protein goes down as the animal matures
protein requirement per day
- the amount of protein per day will increase as the animal matures because they are gaining more muscle mass. they are eating more protein as they grow, but as a percent of their diet, it is less
weak calf syndrome
associated with the amount of portein consumed by the cow during the last 60 days of pregnancy (hay with less than 10% CP, the average amount if cows that will be weak is about 8.5%
general AA structure
- all proteins are made up of simple units called AA
- general structure of AA have an a-amino end and en a carboxyl endO=C-OH O=C-O-
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H2N- C–H H2N+-C–H
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R R
general AA structure physiological pH - proteins always use L-a AA
lysine has e-amino group
- extra NH2
- important for maillard reaction
- carpenter’s available lysine test
peptide bond
- AA linked together with peptide bonds
- couple carboxyl group with a-amino group
- dehydration synthesis
protein structure
- primary = peptide bonds (sequence)
- secondary = a-helix (stabilized by H-bond between (CO) and (NH))
- tertiary = folding of polypeptide chains (3D): stabilized by disulfide bonds and H-bonds
- quartenary = grouping of several tertiary units
functional categories of proteins
- structural proteins
- hormones
- enzymes
- immune system
- transport within body
structural proteins
- contractile: actin and myosin (muscle)
- fibrous proteins: collagen (bone, teeth, skin, tendons, cartilage), elastin (circulatory system), keratin protein (hair, nails, wool, feathers)
hormones
- growth hormone, insulin, glucagon, thyroid hormone, ACTH are proteins
- regulate metabolism
enzymes
almost all enzymes are proteins
immune system
- antibodies are proteins
- IgG, IgA, IgM
transport within body
- chylomicron, VLDL
- albumin (transports fat to blood)
- hemeproteins
other roles of proteins
buffers (look in notes)
protein digestion
- feed protein (plant and animal sources)
- proteins are hydrolyzed to AA
- protein —> AA + di-,tripeptides
- exception: young animals absorb intact proteins (colostrum and immunoglobulins)
- proteins do not go into the blood as di-,tripeptides, but they can be absorbed and then broken down before blood
- born with little to no immunity, so important to get colostrum
- sows don’t cycle until pigs are weaned
protein digestion in stomach
- gastric protease
- pepsin (from chief cells of fundic gland)
- pepsinogen –(HCl)-> pepsin
- diet protein –(pepsin)-> long chain polypeptide
- rennin (abomasum of nursing calf)
- prorennin –(HCl)-> rennin
- casein –(rennin & Ca)-> Ca-paracaseinate (coagulated)
protein digestion in small intestine
- proteolytic enzymes secreted from pancreas: trypsin, chymotrypsin, and chymotrypsin
- trypsinogen –(enterokinase)-> trypsin
- chymotrypsinogen –(trypsin)-> chymotrypsin
- procarboxypeptidase –(trypsin)-> carboxypeptidase
- brush border of villi epithelial cells (amino peptidases: N-terminal end of oligopeptides. Dipeptidases: N-terminal end of dipeptides. Tripeptidases: N-terminal end of tripeptides.
enzyme/activator for pepsinogen
HCl and also pepsin
active form of pepsinogen
pepsin
site of activity for pepsin
stomach
substrate for pepsin
most AA
enzyme/activator for trypsinogen
enterokinase and trypsin
active form of trypsinogen
trypsin
site of activity for trypsin
small intestine
substrate for trypsin
basic AA (lys, arg)
enzyme/activator for chymotrypsinogen
trypsin
active form of chymotrypsinogen
chymotrypsin
site of activity for chymotrypsin
small intestine
substrate for chymotrypsin
aromatic AA (phe, tyr, tryp,) & met, asn, his
enzyme/activator for procarboxypeptidase A & B
trypsin
Site of activity for Carboxypeptidase A & B
Small intestine
Substrate for Carboxypeptidase A
C-terminal neutral AA
Substrate for Carboxypeptidase B
C-terminal basic AA
Site of activity for amminopeptidases
microvilli brush border
substrate for aminopeptidase
N-terminal AA
AA antagonism
two structurally similar AA out of balance (too much of one could result in def of another)
fate of AA following following absoprtion
- tissue synthesis
- synthesis of enzymes and hormones
- deamination
tissue synthesis
- within 5-10 minutes after absoportion AA move from gut to cells where they are used for protein synthesis
- muscle, veins, brains, bone
synthesis of enzymes and hormones
- AA move to cells that secrete enzymes and proteins
- pancreas, GI tract, liver, reproductive organs
deamination
- if AA not needed for protein synthesis, then deaminated
- used for energy or converted to fat
- no storage pool of AA
AA and nutrition
- > 200 AA occur in nature
- only 20-22 commonly found in most proteins
- essential AA (also called indispensable)
- 10 AA either cannot be synthesized or synthesis is inadequate to meet metabolic needs
- must be supplied in the diet
essential (indispensable) AA
- refers to dietary essential; all are tissue essential
- phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, histidine, arginine, leucine, lysine
exceptions to 10 essential AA
- chick requires glycine and proline
- cat requires taurine
- ruminants have no dietary requirement (microorganisms make them; as far as we know, the ten AA must be provided to the animal’s tussues, enough N and enough energy so they can make them)
nonessential (dispensable) AA
- 12+ AA can be synthesized by body cells
- the 10 essential AA may be precursors for some of the others
- all 22+ are needed by body tissue
- alanine, aspartic acid, asparagine, cysteine, cystine, glutamic acid, glutamine, glycine, proline, hydroxyproline, serine, tyrosine
cannula
for testing things leaving the tract where its located (re-entrant or T-cannula)
sparing effect of CYS and TYR
- NRC lists MET + CYS requirement, MET can be used to form CYS, but CYS can only meet its own needs.
- same as PHE + TYR
protein requirements for nonruminants
- primary purpose is to suppl essential AA to the tissues for max performance at a minimum cost
- actually AA nutrition
- they require AA, not protein
- but NRC lists CP requirement
why a CP requirement then?
- we feed protein to get AA
- NRC based on corn-SBM diets
- meets the AA requirements of the most limiting AA (all other AA will be in excess)
limiting AA
- animal can perform no better than that allowed by the AA present in the lowest amount relative to the requirement
- barrel diagram
- 1st limiting AA is the indispensable AA present in the least amount relative to the requirement
- if you can synthesize it, it cant be limiting
usual order of rate-limiting AA in cereal grains
- lysine
- tryptophan (2nd in corn-SBM diet)
- threonine (2nd in other grain based diets)
- methionine
- isoleucine
- legumes: methionine is 1st limiting, but also relatively high in lysine
requirement for lysine is high
- why does lysine have the highest dietary AA requirement
- highest concentration in muscle
- glutamic acid is actually in greatest concentration but can be synthesized
AA requirements
- are the net needs for tissue accretion and maintenance or replacement of net losses
why use the word “net” for AA requirement
- body proteins constantly turning over
- utilization of AA for protein synthesis is several times daily intake
- most AA are efficiently re-utilized
- some irreversibly lost (lost from AA pool)
- daily intake requirements reflect only the net needs of AA
- daily requirement of AA helps replacing lost AA
- in animals, it goes to replacing lost AA and storing muscle mass
does work increase CP/AA requirement?
- work and exercise do not increase requirements
- turnover rate increases
- more recycling
- needs more energy, so just feed more, which inevitably increases the protein anyways
what is protein quality?
- refers to the balance of AA to meet the needs of the animal
- perfect AA balance would equal ~7-8% CP
- egg is closest to being perfect
- biological value: measure of protein quality
high quality
proteins whose AA balance more nearly approximate the needs of the animal
- generally proteins of animal origins
- exception is gelatin (no tryp)
low quality
- low or lacking in one or more indispensable AA
- plant proteins generally low quality
complementary proteins
- corn and SBM complement each other
- Zein: primary protein in corn, practically devoid of lysine and tryptophan
Biological value
- % of absorbed N that is retained or utilized by the animal
- widely used method of expressing protein quality
- values expressed as a %
- 100 = perfect AA balance
- (NI - FN - UN) / (NI - FN) *100 = apparent BV
Apparent BV
(NI-FN-UN) / (NI-FN) *100
Actual BV
NI - (FN - MFN) - (UN - EUN) / NI - (FN - MFN)
- MFN is metabolic fecal nitrogen, and is nitrogen in feces that did not come from diet
- EUN is endogenous urinary nitrogen and is nitrogen in urine that did not come from the diet
PEM
protein energy malnutrition
kwashiorkor
- edema, fatty liver
- protein def, but not necessarily energy def
- eating enough carbs, but feed low in protein
marasmus
- skin and bones appearance
- def in protein and energy
- underfed
- starved
excess AA
- most diets have excess AA
- usually not a problem, but possible
- toxicity: rarely see adverse effects; methionine is most toxic (2.5% of diet, or 5x requirement); other AA have to be 5-10% of diet; growth reduction normally)
- long term could be kidney problem
antagonism
growth depression caused by excess amounts of naturally occurring AA that can be corrected by addition of structurally similar AA
