Phases of gastric secretion Flashcards
What are the 3 phases of gastric secretion?
Cephalic, Gastric, intestinal
What is the composition of bile and how much is produced a day?
Yellow/green - alkaline
- bile salts
- pigments
- cholesterol
- neutral fats
- phospholipids
- electrolytes
What are cholic acid and chenodeoxycholic acid?
2 principle bile salts
What is bilirubin and how does intestinal bacteria affect it?
main bile pigment (waste product of hemoglobin)
- converts bilirubin into stercobilin (feces brown color)
What is the liver’s role in digestion?
produces bile (a cholesterol derivative)
What is the function of the gallbladder?
a storage organ for bile
- contracts to release bile
What is bile and why is it needed?
is a fat emulsifier
- breaking fat down into easier absorbable portions
What is the meaning of amphipathic?
hydrophilic and hydrophobic
What happens when the hepatopancreatic sphincter is closed?
digestion is not occurring
- bile back up through cystic duct and is stored in gallbladder
How does the muscular walls affect the gallbladder?
releases bile into the duodenum
- bile expelled into cystic duct the bile duct
What is the major stimulus of gallbladder contractions?
CCK
What is CCK secreted by and what does it respond to?
small intestine, lipids and peptides
What are the 2 main hormones that regulate bile in the small intestine?
secretin and CCK
What is the role of CCK?
stimulates gallbladder contractions
- stimulates secretion of pancreatic juice
- relaxes hepatopancreatic sphincter
How are bile salt conserved?
recycling (90-95%) through the enterohepatic circulation
What is the function of the ileum when it comes to bile transportation?
ileum (bile transporter reabsorbs 95% of bile salts) to blood to liver (via hepatic portal vein) to new bile
What are gallstones and why are they painful?
They are sharp and in gallbladder/ ducts. When we release bile (the liver contracts) the gallbladder touch the sharp sides
What is obstructive jaundice? And what are other causes of jaundice?
It’s caused by excess bilirubin
- the gallstones block the duct causing bilirubin and bile build up
- Alcoholism, fatty liver disease, hepatitis
What are the treatments of gallstones and what is its effect?
removing the gallbladder
- causes common bile duct to expand to hold more bile
What is acini and what do they mediate?
secretory acinar cells clustered around ducts
- mediate exocrine function of pancreas
What are the 4 basic types of enzymes needed to digest food?
- DNA/ RNA
- protein
- lipids
- carbohydrates
What is the composition of pancreatic juice and what is the function of its alkalinity?
1200-1500 ml/day
- water + electrolytes (bicarb; pH8) + enzymes
- i) neutralize acidic chyme ii) create optimal pH for intestinal and pancreatic enzymes
What is a precursor form and what enzyme is released in that form?
an inactive form (activated once in the duodenum)
- proteolytic enzymes
What form is amylase, lipase and nucleases in?
active form but require ions or bile for optimal activity
What class are membrane-bound enteropeptidase in?
brush border enzymes
What are the 3 types of cells in a gastric gland?
Parietal (secretes HCl and intrinsic factor) + chief cells (secrete pepsinogen) + enteroendocrine cells (secrete hormones and paracrines)
What is the function of secretin and what’s it triggered by?
stimulates pancreatic duct cells to secrete bicarb-rich juice
- acidic chyme
What is the function of CCK of the pancreas and what’s it triggered by?
stimulates pancreatic acinar cells to secrete enzyme-rich juice
- proteins and lipids
How does the parasympathetic nervous system affect secretion?
vagal stimulation of secretory activity
- primarily during cephalic and gastric secretion
What are the 2 regulations of pancreatic secretion?
secretin and CCK
Where are most enzymes manufactured in the intestine?
brush border enzymes
What are most intestinal juices made of?
water + mucus
What are the requirements for optimal intestinal digestive activity?
i) optimal liver & pancreatic function and ii) regulated chyme delivery to stomach
- neutralize stomach HCl and contents of stomach are hypertonic
What is segmentation and what is it initiated by?
contractions of smooth tissue in small intestine for digestion
- intrinsic pacemaker cells in circular muscle
What is the pace of segmentation in the duodenum and ileum and why is one faster?
duodenum (12-14/ min), ileum (8-9/ min)
- duodenum at top faster to push food down
What determines the intensity of segmentation?
long and short reflexes and hormones
What is the function of motilin?
initiates peristalsis starting in proximal duodenum
What do ileal motility (increases) and ileocecal sphincter (relaxes) respond to?
i) gastroileal reflex (initiated by stomach; long reflex) ii) gastrin
What are the important hormones and paracrines?
CCK
- gastrin
- histamine
- intestinal gastrin
- motilin
- secretin
- somatostatin
What is a catabolic reaction and what is the most important process called?
chemical digestion
- hydrolysis (water + breakdown)
What are the monosaccharides?
glucose, fructose, galactose
What monosaccharide makes sucrose, lactose and maltose?
S - glucose + fructose
L - glucose + galactose
M - glucose + glucose
What are the 3 digestive enzymes of carbohydrates?
salivary amylase, pancreatic amylase, and intestinal brush border enzymes
