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