Exam #4 GI Flashcards
saliva composed of…
water w/mucus, sodium chloride, bicarb, K+, and salivary amylase (carb digestion) and is controlled by ANS
also contains IgA - prevents orally ingested microorganisms
What fibers stimulate the salivary glands? what meds inhibit?
cholinergic parasympathetic fibers stimulate salivation
anticholinergic meds inhibit salivation
stimulation of what decreases salivary secretion
sympathetic beta-adrenergic stimulation decreases salivary secretion - none, little, or little with rich protein content
normal pH of saliva
pH of 7.4 which neutralizes bacterial acids aiding to prevent infections
prevents air entry into the esophagus during respiration
upper esophageal sphincter
also called the cardiac sphincter - prevents acidic content regurgitation from the stomach
lower esophageal sphincter
what increases the tone of the lower esophageal sphincter? two things
cholinergic vagal stimulation and the digestive hormone gastrin
*Gastrin helps the pancreas produce enzymes for digestion and helps the liver produce bile. It also stimulates the intestines to help move food through the digestive tract.
what decreases the tone/relaxes the lower esophageal sphincter
non-adrenergic, non-cholinergic vagal impulse and the hormones progesterone, secretin, and glucagon
sphincters & chyme…
lower esophageal (chyme enters from esophagus into the stomach), pyloric (chyme exits stomach into duodenum of small intestines
the stomach can absorb very few substances, but can absorb?
alcohol, aspirin, NSAIDS
gastric hydrochloric acid does what? secreted by? converts what to what? stimulated by (what medication comes into play)? inhibited by?
- secreted by parietal cells of the stomach
- dissolves food fibers
- acts as bactericidal agent
- converts pepsinogen to pepsin (breakdown of proteins)
- stimulated by: acetylcholine via vagus nerve, caffeine, calcium, gastrin (stimulates secretion of gastric acid by parietal cells), histamine
- inhibited by: prostaglandins (mucus), gastric inhibitory peptide, somatostatin, secretin
two things that protect the mucosal barrier? mucus works to do what?
prostaglandins and nitric oxide: protect the mucosal barrier by stimulation of mucous and bicarbonate to inhibit acids
mucus protects against aspirin, NSAIDS, H.pylori, ethanol, regurgitated bile, and ischemia to prevent inflammation and ulceration
Gastric glands: primary secretory units contain what type(s) of cell(s)
parietal cells chief cells G cells Enterochromaffin-like cells D cells
parietal cells secrete?
secrete HCl acid and intrinsic factor, gastroferrin
chief cells secrete?
The primary function of gastric chief cells is the synthesis and release of the proenzyme pepsinogen, which subsequently, in an acid environment, is converted to the acid protease pepsin. Pepsin breaks down proteins in the stomach
g cells secrete?
gastrin (hormone) - *Gastrin helps the pancreas produce enzymes for digestion and helps the liver produce bile. It also stimulates the intestines to help move food through the digestive tract.
enterochromaffin-like cells produce
produce and secrete histamine
D cells
somatostatin
Somatostatin produces predominantly neuroendocrine inhibitory effects across multiple systems. It is known to inhibit GI, endocrine, exocrine, pancreatic, and pituitary secretions, as well as modify neurotransmission and memory formation in the CNS
phases of gastric secretion
celiac phase
gastric phase
intestinal phase
celiac phase of gastric secretion
where does it begin? what is secreted? mediated by? what is a strong stimulus to gastric secretion?
mouth
- begins with smelling, seeing, tasting, chewing, swallowing
- mediated by the vagus nerve
- acid, pepsinogen, gastrin secreted
- insulin secreted by pancreas to hyperglycemia and is strong stimulus to gastric secretion
gastric phase of gastric secretion
mediated by? blocked by?
2 major stimuli?
stomach
-begins with arrival of food to stomach
-2 major stimuli to secretory effect – distension of stomach and presence of digested protein
-vagus nerve stimulated by distension – contributes
to secretion stimulus
-mediated by acetylcholine and can blocked by
atropine
*distension causes PSNS activation of the vagus nerve which continues the signal to secrete HCl and pepsin
_____ levels higher in gastric secretions than in plasma
what is this important to note with?
potassium
important in vomiting, suctioning, etc.
______ allows for relaxation of lower esophageal sphincter during swallowing
vagus nerve
what two things enhance relaxation of the stomach. Remember that one of them normally increases tone of LES
gastrin and cholecystokinin
what three things increase peristalsis contractions of the stomach
gastrin, motilin, and low blood glucose enhance peristalsis
what three things inhibit peristalsis
sympathetic activity, secretin, and cholecystokinin inhibit peristalsis
the vagus nerve stimulates (parasympathetic) _____ and ______
stimulates gastric secretion and motility
gastric emptying is increased by? decreased by?
increased gastric emptying occurs d/t large volume consumption
delayed by solids, fats, and non-isotonic solutions
*slowed down by fats d/t cholecystokinin – inhibits intake, gastric motility, decreases gastric emptying so that fats do not exceed rate of bile and enzyme secretion
Intestinal phase - begins with? does what? what inhibits gastric secretions?
- begins with movement of chyme from stomach to duodenum
- decelerates gastric secretion – when chyme enters alkaline environment of duodenum – inhibitory vagal reflexes decrease gastric motility
- secretin and cholecystokinin stimulate pancreatic secretions and inhibit gastric secretions
• Peritoneum – serous membrane surrounding
the organs of the abd and pelvic cavity
• Visceral – lies over the organs
• Parietal – lines the wall of the abd cavity
• Inflammation of the peritoneum, peritonitis,
occurs with perforation of the intestine or after
surgery
• Peritoneal cavity: Space between the two layers of the
peritoneum
Know these
remember it’s visceral peritoneum and parietal peritoneum
________ within the small intestine slow the passage of
food providing more time for digestion and absorption (more numerous in the jejunum and upper ileum)
Mucosal folds (plica) - part of the muscular layer of the small intestines
Myenteric plexus and mucosal plexus of the small intestines
site of intrinsic motor innervation mediation
• Parasympathetic – secretion, motility, pain sensation, and intestinal reflexes mediation
• Sympathetic – inhibits motility and produces vasoconstriction
Villi in the SI - what occurs here?
– cover the mucosal folds and are the functional units of the intestine
• Absorption occurs through the villi
Villus composed of two things?
absorptive columnar cells (enterocytes) and mucus
secreting goblet cells of the mucosal epithelium
Surface of each columnar epithelial cell contains ______
_____ with microvilli increase surface area for absorption
contains microvilli
remember there’s a villi and microvilli that cover it
villi and microvilli increase surface area for absorption
All nutrients are absorbed in the _______ as well as 85% of the water and fluid intake
small intestines
Carbohydrates digested into? What breaks it down? Sugars absorbed where?
- digested into monosaccharides and disaccharides
- salivary and pancreatic amylase break down starches
- sugars are primary absorbed in the duodenum and in the upper jejunum (so first two parts of SI)
Proteins digested into? Where are they broken down by hydrolysis? Carboxypeptidase?
- digested into amino acids and peptides
- pancreatic enzymes accomplish major protein hydrolysis in small intestines (trypsin and chymotrypsin hydrolyze the bonds or large molecules - endopeptidase)
- carboxypeptidase: breaks away the end amino acids (exopeptidase)
Fats digested into?
fatty acids and monoglycerides
fat digestion step 1
- emulsification: emulsifying agents cover the small fat particles and prevent them from reforming into fat droplets - fats are then ready for lipolysis - LIPASE (from pancreas) breaks down triglycerides; PHOSPHOLIPASE cleaves fatty acids from phospholipids; CHOLESTEROL ESTERASE breaks down cholesterol esters
fat digestion step 2 - 4 see notes, not bolded
…
Most minerals are absorbed by _______ or ______
Most ________ vitamins are passively absorbed or by sodium-dependent active transport
most minerals are absorbed by passive diffusion or active transport (requires energy) or are actively transported with a carrier protein
most water-soluble vitamins are passively absorbed or by sodium-dependent active transport
Large intestines do what?
Massages fecal mass; absorbs water and electrolytes
mucus secreting goblet cells are in the LI, but no villi
Intestinal motility: Contractions of the circular muscles, called ________, mixes the chyme and promotes digestion
segmentation
_______ inhibits gastric motility when the ileum is distended
Ileogastric reflex
The _________ reflex inhibits intestinal motility when one intestinal segment is over distended
intestinointestinal
_________ increases intestinal motility when gastric motility increases
• Initiates propulsion in the entire colon, usually during or immediately after
eating, when chyme enters from the ileum
• Causes fecal mass to pass rapidly into the sigmoid colon and rectum,
stimulating defecation
• Stimulates the reflex: Gastrin and cholecystokinin
• Inhibits the reflex: Epinephrine
• Increased intra abdominal pressure facilitates defecation
Gastroileal reflex
Liver produces __________ necessary for fat digestion and
absorption
• Receives nutrients absorbed by the small intestine; which are metabolized and
synthesized into forms that can be used by the body’s cells
• Then releases them into the bloodstream or stores them for later use
bile, with salts
Exocrine pancreas produces what?
enzymes needed for complete digestion of
carbohydrates, proteins, and fats
• Also produces an ALKALINE FLUID that neutralizes chyme and produces duodenal pH necessary for enzymatic function
*These enzymes include trypsin and chymotrypsin to digest proteins; amylase for the digestion of carbohydrates; and lipase to break down fats.
Contractions of circular muscles (_______) mixes chyme and promotes digestion
segmentation
Inhibits gastric motility when the ileum is distended
Ileogastric reflex
Inhibits intestinal motility when one intestinal segment is over distended
intestinointestinal reflex
Increases intestinal motility when gastric motility increases
gastroileal reflex
- stimulates gastrin and cholecystokinin and decreases epinephrine
- initiates propulsion in the entire colon, usually during or right after eating
Liver lobules contain plates of hepatocytes that are the functional cells of the liver…what do they do?
hepatocytes synthesize 700-1200mL of bile per day and secrete into bile canaliculi – small channels b/w hepatocytes that can drain bile into the common bile duct and then into the duodenum through the sphincter of Oddi
What are canaliculi
small channels b/w hepatocytes that can drain bile into the common bile duct and then into the duodenum through the sphincter of Oddi
Star shaped cells that store lipids including vitamin A
lipocytes in the liver
mononuclear phagocyte system in the liver central to innate immunity
Kupffer cells - phagocytic cells in the liver
contain retinoids (vitamin A) - are contractile in liver injury, regulate sinusoidal blood flow, may proliferate into myofibroblasts, participate in liver fibrosis, remove foreign substances from the blood, and trap bacteria
stellate cells
pit cells in the liver are what? why are they important?
Natural killer cells - important in tumor defense
alkaline, bitter-tasting, yellowish green fluid that contains bile salts, cholesterol, bilirubin, electrolytes, and water
bile secretion
conjugated bile acids that are required for the intestinal emulsification and absorption of fats
bile salts
synthesized from cholesterol by the hepatocytes and are required for intestinal emulsification and absorption of fats
primary bile acids - primary acids are then conjugated to form bile salts
product of bile salts deconjugation by bacteria in the intestinal lumen
secondary bile acids
enterohepatic circulation
recycling of bile salts, also called choleresis
choleretic agent
strong?
substance that stimulates the liver to secrete bile
strong stimulus: high concentration of bile salts
other cholerectic agents? secretin, cholecystokinin, vagal stimulation
pigment which is the by-product of the destruction of aged red blood cells in the liver and spleen
bilirubin
*bilirubin gives bile a greenish black color and produces the yellow tinge of jaundice
unconjugated bilirubin
is lipid soluble and can cross the cell membrane, present in the circulation, bound to plasma protein
conjugated bilirubin
liver changes bilirubin to a water-soluble form that can now be excreted
primary method of bilirubin excretion is in the bile
urobilinogen
in the ileum and colon, conjugated bilirubin is deconjugated by bacteria and then converted
gives feces its brown color
higher percentage of unconjugated bilirubin = ?
heme breaking down, or inability of liver to conjugate
*ex. missing enzyme (congenital), hemolytic anemia
higher percentage of conjugated bilirubin = ?
problem with secretion into bile
*ex. biliary obstruction, hepatitis
liver functions
- vascular and hematologic functions: stores bloods, removes bacteria or foreign particles, synthesizes clotting factors
- metabolizes fats (bile)
- synthesizes phospholipids and cholesterol
- metabolizes proteins - deamination: the removal of ammonia (converted to urea and secreted in urine); converts amino acids into carbohydrates
- metabolizes carbohydrates: liver releases glucose during hypoglycemia; takes up glucose during hyperglycemia; stores glucose as glycogen (glyconeogenesis) or converts it to fat
- detoxification through biotransformation
- storage of minerals and absorption of fat-soluble vitamins *vit K - essential for synthesis of clotting factors; absorption depends on adequate bile production
