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