EXAM 4 A&P II De Leon @ UTRGV
the 3 chemicals that stimulate parietal cells are
-acetylcholine: inc. intracellular Ca -gastrin: inc. intracellular Ca -histamine *** All are necessary for max HCl secretion
pancreatic enzymes
-acinar cells involved in breakdown -protease -pancreatic amylase -lipases -nucleases
submucosa layer of the GI tract
-areolar connective tissue with elastic fibers, blood & lymph vessels, lymphoid follicles, nerve fibers, and submucosal nerve plexus (ganglia)
bile, a yellow-green alkaline solution, contains
-bile salts -phospholipids -bilirubin from RBC breakdown -cholesterol -triglycerides
the regions of the stomach are (in order from entrance to exit)
-cardia -fundus -body -pyloris
3 phases of stimulatory/inhibitory events for regulation of gastric secretion
-cephalic (reflex): conditioned reflex triggered by aroma, taste, sight, thought -gastric: lasts 3-4 hrs & provides 2/3 of gastric juice released -intestinal: brief stimulatory effect as partially digested food enters duodenum followed by inhibitory effects
what 3 things does the small intestine receive
-chyme from stomach -digestive enzymes and bicarbonate from pancreas -bile from liver and gallbladder
muscularis externa layer of GI tract
-circular & longitudinal sections -responsible for segmentation & peristalsis -myenteric nerve plexus -in some areas the circular layer thickens to form sphincters which prevent backflow
receptive relaxation of smooth muscle
-coordinated by swallowing center of the brain -mediated by the vagus nerve (parasympathetic)
bicarbonate
-duct cells -neutralize acidic chyme
the small intestine is made up of what 3 parts
-duodenum -jejunum -ileum
what are the 5 major types of cells that make up the small intestine
-enterocytes -goblet cells -enteroendocrine cells -paneth cells -stem cells
in response to fatty chyme & proteins, what 3 things does cholecystokinin (CCK) stimulate
-gallbladder to contract and release bile -pancreas to release digestive enzymes -hepatopancreatic sphincter to relax
the stomach has sphincters at both ends, called the ________ and the ________
-gastroesophageal sphincter -pyloric sphincter
gastric pits of the mucosa of the stomach
-have gastric glands -secrete gastric juice (most is produced in the fundus and body of stomach)
digestive processes (6)
-ingestion -propulsion -mechanical breadown -digestion -absorption -defacation
short reflexes
-intrinsic controls -local control of enteric plexus
enteric nervous system (the "3rd division of the ANS")
-intrinsic nerve supply in the wall of the GI tract -a complete reflex circuit -functions mostly independently of the CNS, but is modulated by the sympathetic/parasympathetic nervous system (reacts to either stimuli in the digestive tract or signals from the ANS)
the functions of saliva include
-moistens & cleanses mouth -dissolves food chemicals for taste -moistens food & aids in bolus formation -contains enzymes that begin breakdown of starch -mucin, lysozyme, IgA antibodies, defensins
all of the parts of the alimentary canal
-mouth -pharynx -esophagus -stomach -small intestine -large intestine -anus
organs of the GI tract have ____ basic layers
4
only ______ percent of bile is newly synthesized each time
5
parietal (oxynetic) cells (in the glands of the mucosa of the stomach) secrete...
HCl & intrinsic factor (for B12 absorption in sm. intestine)
the muscularis externa of the stomach has a 3rd additional layer, called the _______, which allows the stomach to ________________
oblique layer; mix, churn, & pummel food while being moved
movement via peristalsis is ______________
one-way; directional
chemoreceptors in the GI tract wall respond to
pH and nutrients
pancreatic fluid contains _________ and _______
pancreatic enzymes; bicarbonate
histamine, in response to gastrin, stimulate ______ to release HCl
parietal cells
gastrin, which regulates secretion & motility, also stimulates _______ to release HCl and ______ cells to secrete pepsinogen
parietal cells; chief
absorption
passage of digested end products from GI lumen to blood & lymph by active & passive transport
chief (zygomatic) cells (in the glands of the mucosa of the stomach) secrete....
pepsinogen for protein digestion & lipases to help digest lipids
movement via segmentation is __________
primarily mixing (forward then backward)
the stomach's ability to secrete intrinsic factor is required for the intestinal absorption of vitamin B12, which is important because it is needed to...
produce maturation of RBC's
submucosal nerve plexus of the ENS
regulates glands & muscularis mucosae
during vomiting, _____ is inhibited
respiration
the stomach has ______, which look like little wrinkles that allow expansion
rugae
somatostatin inhibits __________ &________
secretions; motility
the _________ is the major site of digestion and absorption
small intestine
serotonin stimulates _______________
smooth muscle contraction
arrival of fatty chyme into the duodenum triggers a neural and endocrine reflex. the endocrine reflex does what
stimulates the gallbladder to contract, causing bile to be transported through common bile duct and injected into the duodenum a major stimulus is cholecystokinin, which is secreted from sm intestine when fat is detected
the function of the gallbladder is to
store & concentrate bile
deglutition
swallowing
when the bolus arrives at the pharynx, the ________ reflex via the nervous system is triggered, movement of the larynx tips the ______ down preventing food from entering the trachea. at the same time the _________ relaxes allowing the bolus into the esophagus and the trachea then reopens, meanwhile ________ contractions move the bolus into the stomach
swallowing; epiglottis; esophageal sphincter; peristaltic
in response to acidic chyme, what does secretin stimulate
the pancreas to release bicarbonate to neutralize the chyme
mucous neck cells (in the glands of the mucosa of the stomach) secrete...
thin acidic mucous
what is the exocrine function of the pancreas
to secrete pancreatic fluid into the duodenum through the pancreatic duct
proteases
trypsin, chymotrypsin, carboxypeptidase (activated forms); breakdown proteins into polypeptides
bile destroys nonfunctional _______
RBC's
the parasympathetic ________ salivation while the sympathetic ________ it
activates; depresses
peristalsis involves ____ segments of the alimentary canal organs alternately contracting and relaxing
adjacent
the digestive system is made up of 2 groups of organs, the __________ and the _________
alimentary canal; accessory digestive organs
the presence of ______, ______, ______ chyme in the duodenum, plus distention, will cause inhibition of gastric emptying
fatty; hypertonic; acidic
alimentary canal
gastrointestinal tract
the _________ and _________ control entry of bile & pancreatic juice into the duodenum
hepatopancreatic ampulla; sphincter
enteroendocrine cells (in the glands of the mucosa of the stomach) secrete ____________ into the lamina propria
hormones (enterogastrones) that regulate digestion: -histamine -serotonin -somatostatin -gastrin
mechanical breakdown _________ the surface area of food
increases
parasympathetic stimulation via the vagus nerve _____________ secretion of gastric juice for digestion
increases
short nerve reflexes in the enteric nervous system stimulation _________ secretion of gastric juice for digestion
increases
proton pump inhibitors
inhibit the H+/K+ ATPase proton pump so to halt the formation of HCl (for conditions like heartburn, reflux, etc)
the 1st stage of digestion is ___________
mechanical (mastication)
enteric nervous supply to the GI tract wall controls _______ & _______
motility and secretions
alimentary canal is from the _______ to the _______
mouth; anus
propulsion
moving food through the GI tract, includes swallowing (voluntary) and persitalsis (involuntary)
the stomach lining is protected by the ________
mucosal barrier
segmentation involves ______ segments of the alimentary canal organs contracting and relaxing
nonadjacent
the 4 basic layers that organs of the GI tract have are...... (inner to outer)
-mucosa (epithelium, lamina propria AKA loose areolar connective tissue, and muscularis mucosae AKA smooth muscle) -submucosa (areolar connective tissue with elastic fibers) -muscularis externa (controls mobilities such as propulsion) -serosa (epithelium- meso, and connective areolar tissue)
the glands of the mucosa of the stomach include which secretory cells
-mucous neck cells -parietal (oxynetic) cells -chief (zygomatic) cells -enteroendocrine cells
mucosa layer of the GI tract
-mucus membrane from mouth to anus -secretes mucus, enzymes, and hormones -absorbs nutrients -protects against infectious diseases
what are the structural modifications of the small intestine that increase surface area for digestion and absorption
-numerous folds -the epithelial lining is covered with villi -the villi are covered with microvilli (brush border) (have enzymes)
the mechanism of HCl formation
-parietal cells pump H+ (from carbonic acid breakdown) into the stomach lumen via H+/K+ ATPase (proton pumps) -as H+ are pumped into lumen, HCO3- are exported back to blood via a Cl- and HCO3- antiporter (inc in HCO3- in blood is called alkaline tide) -Cl- pumped out to lumen, joins with H+ to form HCl
gastric accomodation
-plasticity (stress-relaxation response) of visceral sm. muscle -expansion to accommodate inc volume without causing strong contractions
what are the 3 phases of peristaltic waves in the stomach
-propulsion: peristaltic waves move from fundus toward pylorus; distension of the stomach/gastrin inc this gastric motility -grinding: vigorous peristalsis/mixing action close to the pylorus; pyloric end of stomach acts as pump, delivering small amts of chyme into duodenum -retropulsion: peristaltic waves close the pyloric valve, forcing most of contents back into stomach (this back and forth movement breaks up solids)
what 2 factors cause pressure to remain constant in the stomach, up until 1.5 L of food is ingested
-receptive relaxation (of sm. mucle) -gastric accomodation
enterohepatic circulation (recycling mechanism) of bile salts
-secretion into the duodenum -reabsorption at the ileum into the hepatic portal vein -travel up the hepatic portal vein to the liver
the enteric nervous system participates in 2 reflex arcs:
-short reflexes -long reflexes
the main difference between short & long reflexes is...
-short reflexes deal with stimuli in the GI tract wall and the local nerve plexus sends signals to the effectors (muscles/glands) to respond -long reflexes deal with stimuli in the GI tract wall and send signals to the CNS, which then sends signal via the vagus nerve to the nerve plexus in the GI tract wall to send a signal to the effectors to respond
the enteric nervous system is composed of two intrinsic nerve plexuses:
-submucosal nerve plexus -myenteric nerve plexus
the accessory digestive organs are:
-teeth -tongue -gallbladder -digestive glands @ the pancreas, liver, and salivary glands
the function of the stomach is to
-temporarily store food -begin protein digestion -convert food into chyme
3 factors of the mucosal barrier of the stomach
-thick layer of bicarbonate-rich mucus -tight junctions -damaged cells are replaced very quickly (3-6 days)
long reflexes
-uses CNS & Autonomic nerves -extrinsic controls -parasympathetic enhances digestive process -sympathetic inhibits digestion
hepatic portal circulation
-venous portion of the splanchnic circulation -collects nutrient-rick blood from digestive organs via the hepatic portal vein
serosa layer of the GI tract
-visceral & parietal peritoneum -in the esophagus, its replaced by adventitia -retroperitoneal (outside) organs have both a serosa & an adventitia
the liver's function is to secrete...
bile
bile
bile pigments (waste products) & bile salts (for emulsification/breaking down into droplets of fats, as well as absorption)
what is the most powerful stimulus for bile secretion
bile salts returning from enterohepatic circulation
of all of bile's components, only ______ and ____ aid in the digestive process
bile salts; phospholipids
splanchnic circulation
blood flow to the digestive organs
arteries that branch off the abdominal aorta to serve digestive organs include
branches of the celiac trunk & mesenteric arteries (superior & inferior)
lipases
breakdown fats into free fatty acids & monoglycerides
nucleases
breakdown nucleic acids into nucleotides
pancreatic amylase
breakdown polysaccharides into shorter sugars
what neural factors inhibit gastric emptying
chemoreceptors and stretch receptors in the sm intestine trigger the enterogastric reflex, decreasing contractile force of stomach and decreasing rate of stomach emptying
mechanical breakdown
chewing (mouth), churning (stomach), segmentation (rhythmic constrictions in the small intestines)
myenteric nerve plexus of the ENS
controls GI tract motility
sympathetic stimulation _______ secretion of gastric juice for digestion
decreases
HCl's role in digestions is to...
denature proteins
The function of the alimentary canal
digest and absorb food
what hormonal factors inhibit gastric emptying
duodenum enteroendocrine cells in the sm intestine secrete enterogastrones (inhibit HCl & pepsin secretion) which decrease contractile force of stomach & decrease rate of stomach emptying
most enzymatic hydrolysis occurs in the ________ while absorption occurs primarily in the __________ but also the ______
duodenum; jejunum; ileum