digestive Flashcards
What layerof the GI tract is the serosa and what is its prupose?
outer tough connective tissue membrane for protection
What does the muscularis extrena of the GI tract do?
longitudinal and circular muscle layers for contraction
What is the submucosa?
Loose connective tissue, blood vessels and glands for secretion
What are the three layers of the GI tract mucosa?
muscularis mucosa (interna), lamina propria made of loose connective tissue, epithelium lining
What is the function of the mucosa layers?
function for digestion and absorption of nutrients
What are the two nerve networks in the enteric nervous system?
myenteric plexus (Auerbach) and submucosal plexus (Meissner)
Where is the myenteric plexus located?
neuron net between circular and longitiudinal muscle layers
What is the function of the myenteric plexus?
contorls contraction of muscularis extrena & controls peristalsis, segmentation, haustration and mass movement
Where is the submucosal plexus located?
scattered neurons in the submucosal layer
What does the submucosal plexus do?
controls contractions of muscularis mucosa (interna) & controls glandular secretion of mucosa
What controls GI secretions and contractions throughout the gut wall?
enteric nervous system reflexes
What do the prevertebral sympathetic gangflia reflexes do?
transmit signals between GI sections such as gastrocolic, enterogastric and colonoileal
What is the name of the reflexes that respond to pain and defecation?
spinal cord and brain stem reflexes
What is the law of the gut?
peristalsis
What is peristalsis?
The GI basic propulsive movement in which a contractile ring moves towards the anus with downstream receptive relaxation
What is mixing?
Local intermittent constrictive waves of regular contractions for chopping and mixing the food.
What is segmentation?
Concentric contractions that divide the small intestine into small segments
What is haustration?
Concentric contractions that divide the large intestine into small haustral segments
What is mass movement?
Propulsive contractions that move fecal matter along the large intestine.
In splanchnic circulation; where do the arterial branches come from?
from the abdominal aorta
What are the three branches of the celiac trunk and where do they go?
hepatic artery proper to the liver, left gastric artery to the stomach and splenic artery to the spleen
Where does the superior mesenteric artery go?
small intestine, ascending colon, tansverse colon
Where does the inferior mesenteric artery go?
descending colon, sigmoid colon and rectum
What does the hepatic portal system consist of?
superior mesentric vein, gastic veins, inferior mesenteric vein and the splenic vein
What do the liver reticuloendothelial and hepatic cells do?
remove bacteria, detoxify chemicals and absorb nutrients from the venous blood
Where does the hepatic vein drain all the venous blood?
inferior vena cava
What does the oral cavity consist of?
Cheeks and lips, tongue, and hard and soft palate
What is the space between the cheeks and teeth called?
vestibule
What do the hard and soft palate do?
Allow breathing and cewing at the same time
What are the palatoglossal and palatopharyngeal arches?
names of the hard and soft palate
What 2 msucles elevate the teeth to crush food?
masseter and temporalis
What 2 muscles swing teeth in side-to-side grinding action of molars?
medial and lateril pterygoids
What 2 types of enzymes does saliva include?
salivary amylase and lingual lipase
What immunoglobulin inhibits bacterial growth in the saliva?
immunoglobulin A
What breaks starch down into disaccharides?
salivary amylase which is secreted by salivary glands
What is the only part of swallowing that is under concious control?
buccal phase
What does the pharyngeal pahse consist of?
soft palate closes nasopharynx & epiglottis closes larynx, food bolus pass from oropharynx into laryngopharynx
When can choking occur?
if foood bolus got stuck in the laryngopharynx
What occurs during the esophageal phase?
the upper esophageal sphincter open, peristalsis propels food bolus down the esophagus toward the sotamch, lower esophageal sphincter opens and food bolus enters stomach
In the stomach; what begins protein digestion?
pepsin
In th estomach; what begins fat digestion?
activated lingual lipase
What secretes the proctective mucous of the gastric glands?
mucous neck cells
What part of the gastric gland ssecrete HCl and IF?
parietal cells
What do the chief cells secrete?
pesinogen, gastric lipase and chymocin
What do entroendocrine cells secrete?
gastric hormones
What is the bottom most layer of the gastric glands?
where regenrative cells produce new cells
What does HCl do?
activates pepsin and lingual lipase, break connective tissue and plant cell walls, liquefies food to form chyme, convert ingested ferric ions to ferrous ions for absorption an duse in hemoglobin synthesis, destroys ingested bacteria and pathogens
What is intrinsic factor needed for?
B12 absorption by small intestine & is necessary for RBCs production and maturation
What does gastric lipase produced by cheif cells do?
digest fat- specifically butter fat of milk in infants
Chymosin
curdles milk by coagulation proteins
What is pepsin secreted as? What converts it to active pepsin?
secreted as inactive pepsinogen zymogens
HCl converts it to active pepsin
What nerve stimulates gastric secretion even before food is swallowed?
the vagus nerve
Food stetches the stomach and activates ____ and _____ reflexes
myenteric and vagovagal
What is the small intestine covered with?
lined with villi, covered with a simple columnaer mucous membrane
What is the single lymph capillary in the small intestine called?
a lacteal which absorbs most fat
What are the 3 function fo the small intestine?
mechanical digestion, chemical digestiona dn absorption of most substances
What are the 6 gastrointestinal hormones?
- gastrin- stimulates gastric acid secretion and mucousal growth
- cholecystokinin- stimulates pancreatic enymes and bicarb secretions, stim gallbladder contractions and gastric emptying
- secretin- stim pepsin and bicard secretion, inhibits gastric emptying
- gastric inhibitory peptide- stim insulin secretion, inhib gastric acid secretion
- motilin- stim gastric and intestinal motility
What cells are the 6 gastrointestinal hormones secreted from?
gastrin- G cells cholecystokinin- I cells secretin- S cells gastric inhibitory peptide- K cells motilin- M cells
What are acinar cells?
exocrine cells that secrete digestive enzymes into ducts
What cells secrete bicarbonates and what do the bicarbonates do?
duct cells
bicarb buffers the acidic chyme from stomach and raise its pH from 2-3 to 7-8
Where is cholecystokinin (CCK) released from and in response to what?
released from duodenum in response to arrival of acid and fat
What does cholecystokinin do?
causes contraction of gallbladder, secretion of the acinar cells pancreatic enzymes and relaxtion of the hepatopancreatic sphincter (sphincter of Oddi)
Where is secretin released from?
released from duodenum in presonse to the presence of acidic chyme
What does secretin stimulate?
stimulates all ductal cells to secrete more bicarbonate
Where is gastrin released from?
stomach and duodenum
What does gastrin do?
weakly stimulates gallbladder contraction and pancreatic enzyme secretion
What are enzymes secreted as?
inactive zymogens
trypsinogen activated to trypsin by ____ enzyme from duodenum epithelium cells.
entrokinase
chemotrypsinogen activated to ____ by the _____ enzyme
chemotrypsin
trypsin
procarboxypeptidase activated by the _____ enzyme to _______
trypsin
carboxypeptidase
What are remaining starch digested into after protein digestion and how?
remaining starch is digested in intestine by pancreatic amylase into disaccharides
What are triglycerides digested by?
digested in the small intestine by pancreatic lipase
What does the digestion of a triglyceride yield?
a monoglyceride molecule and two fatty acid molecules
What is required from the gallbladder for lipase to digest fat more efficiently?
Bile
What is biles pathway?
hepatocytes secrete bile
bile flows from the liver through hepatic ducts into the gallbladder
bile flows from gallbladder down the bile duct into duodenum to mix with and emulsify the fat
What stores and concentrates bile?
gallbladder
What forms the common bile duct?
common hepatic duct and cystic duct from gallbladder unite
Before bile and pancreatic juices can enter the duodenum; what occurs?
common bile ducts unites with pancreatic duct
What are the functions of the liver?
(1) Carbohydrate, lipid and protein metabolism
(2) Removal of waste products & detoxification
(3) Storage of glycogen, vitamins and iron
(4) Phagocytosis by Kupffer cells
(5) Activation of vitamin D to Calcidiol
(6) Bile synthesis and secretion
(7) Plasma proteins synthesis
Where are brush border enzymes located?
on microvilli of intestinal absorptive cells
What do peptidases digest?
peptides to amino acids
What do intestinal lipases digest?
fats to glycerol & fatty acids
What do disaccharidases digest?
digest disaccharides to monosaccharides
What disaccharidase and resulting monosacchrides of sucrose?
sucrase
results in glucose and fructose
What disaccharidase and resulting monosacchrides of maltose?
maltase
results in glucose and glucose
What disaccharidase and resulting monosacchrides of lactose?
lactase
results in glucose and galactose
How are DNA and RNA absorbed in the small intestine?
hydrolyzed by nucleases to nucleotides
nucleosidases and phosphatases of brush border split them into phosphate ions, ribose or deoxyribose sugar and nitogenous bases then absorbed
How are vitamins absorbed in the small intestine?
unchanged
A, D, E and K with other lipids
B complex and C by simple diffusion and B12 bound to intrinsic factor
How are mineral absorbed in the small intestine?
absorbed all along the small intestine
- sodium co-transported w sugars and amino acids
- Cl- exchanged for bicarb
- iron and calcium absorbed as needed
What type of epithelia cells line the large intestine?
simple columnar mucosa
What are 4 function of large intestine?
(1) Feces formation
(2) Limited digestion of undigested food by bacteria
(3) Formation of vitamin K and some B vitamins by bacteria
(4) Absorption of some water, electrolytes, vitamins and bile salts
How much water does the digestive tract receive a day? How much water is absorbed in the small intestine and the large intestine?
9 L/day
small intestine: 8 L/day
large intestine: 0.8 L/day
How is water absorbed?
by osmosis following the absorption of salts and organic nutrients
When does diarrhea occur?
when too little water is absorbed
- feces pass thru too quickly if GI is irritated
- feces contain high conc. of an unabsorbed solute such as lactose or chloride
What is constipation caused by?
poor motility causes greater absorption and hardens feces in transverse colon
What does feces consist of?
water, bacteria, undigested fiber, mucus, fat and sloughed epithelial cells
What are haustral contractions stimulated by?
distention
When does mass movement occur and what triggers it?
1 to 3 times a day
triggered by gastrocolic and duodenocolic reflexes from stomach and duodenum filling
Is made of smooth muscle fibers, relaxed by parasympathetic pelvic nerve stimulation, constricted by sympathetic hypogastric nerve stimulate.. what am I?
internal anal sphincter
Is made of skeletal muscle fibers, innervated by the pudendal nerve, and under voluntary conscious control… what am I?
external anal sphincter
What does an intrinsic reflex do?
activates mass movement that fill the rectum and stimulate rectal stretch receptors
What does a spinal cord reflex do?
cause contraction of the rectum and relaxtion of the internal anal sphincter via parasympathetic pelvic nerve signals
What does a pudendal nerve reflex do?
causes concious voluntary relaxtion of the external sphincter and defecation
What is esophagitis?
inflammation of esophageal mucosa
What is dysphagia?
difficulty swalling caused by any esophageal obstructions or paralysis
What is paralysis of the swallowing mechanism caused by?
muscle dystrophy, myasthenia gravis or diseases that damage the swallowing center
What is achalasia?
failure of relaxation of the lower esophageal sphincter during swallowing due to myenteric plexus damage
In achalasia, food accumulation occurs above the sphincter, what is this called?
megaesophagus
What is gastritis?
inflammation of the gastric mucosa due to gastric barrier damage
What is achlorhydria?
complete failure of hydrochloric acid secretion by the gastric glands
What is pernicious anemia?
intrinsic factor deficiency due to chronic gastritis
What is a peptic ulcer?
excoriated areas of GI mucosa caused by the digestive action of gastric secretions
What is the small intestine abnormal digestion disorder caused by?
can be caused by failure of secretion of pancreatic enzymes due to pancreatitis or pancreatic duct block
What is the small intestine disorder tropical sprue?
malabsorption due to bacterial inflammation of the intestinal mucosa
What is the small intestine disorder nontropical sprue?
malabsorption caused by the toxic effect of gluten as in celiac disease and gluten–sensitive enteropathy
What is Hirschsprung’s disease? (large intestine)
lack of ganglion cells int he myenteric plexus causes absence of the defecation reflexes and fecal accumulation in the sigmoid colon forming a megacolon
What is infectious diarrhea in the large intestine?
caused by viral or bacterial enteritis infections int he large intestine
What is psychogenic diarrhea in the large intestine?
caused by excessive stimulation of the parasympathetic nervous ssytem during periods of high nervous tension
What is ulcerative colitis in the large intestine?
extensive ulceration of the large intestine mucosa caused by allergic or immune destruction leading to severe diarrhea
What is paralysis of defecation?
can be caused by destruction of the conus medullaris nucleus in spinal cord injuries
What is nausea?
subconscious excitation of the vomiting center by irritative impulses fromt he GI tract, lower brain or cerebral cortex
What is vomiting used for?
the means by which the upper GI tract gets rid of its content
can be initiated by irritative impulses to the vomiting center or the chemoreceptor trigger zone
What is ascites?
accumulation of fluid and protein in the abdominal cavity due to decreased pplasma proteins or high protal capillary pressure
What can be causes for obstructions in the GI tract?
due to cancer, fibrotic adhesions or paralysis
What is flatus?
gases accumulation in the GI tract from swallowed nitrogen in the air or bacterial action in the large intestine generaitng hydrogen, methane, hydrogen sulfide, indole and skatole
What are 5 causes of ulcers in the stomach?
- high acid and peptic content
- irritation
- poor blood supply
- poor secretion of mucus
- infection, H. pylori
