Normal GI Flashcards
What is segmentation?
using smooth muscle to squeeze apart food particles and mix them with surrounding material
Where does segmentation take place?
Small intestine
What type of digestion is segmentation?
Mechanical
What are the two types of nerve plexuses in the GI tract?
Short (enteric)
Long (CNS involvement)
What are the three layers of the mucosa?
Epithelium
Lamina propria
Muscularis mucosae
What is found in the submucosa?
Blood vessels, lymph, nerves
What does the submucosa do?
Allows GI tract to expand
Differentiates parts of the small intestine
What is the makeup of the muscularis layer?
2 layers
Inner circular, outer longitudinal
What are the four layers of the alimentary canal?
Mucosa
Submucosa
Muscularis
Serosa or Adventitia
What determine if a layer will be covered by serosa or adventitia?
Esophagus, rectal canal, parts of retroperitoneal are covered by adventitia- rest of structures by serosa
What are the two major intrinsic plexuses?
Submucosal nerve plexus
Myenteric nerve plexus
What do salivary glands do?
Clean mouth, taste, moisten food, chemical breakdown of starch (most are extrinsic)
What are intrinsic salivary glands?
Buccal
Keep mouth moist
How are extrinsic salivary glands described?
Paired, compound, tubuloalveolar glands
What are the three extrinsic salivary glands?
Parotid glands
Submandibular glands
Sublingual glands
What are the two phases of deglutition?
Buccal phase
Pharyngeal-esophageal phase
Where is the swallowing center located?
Medulla and pons
What cell types if mainly found in the stomach in gastric pits?
Goblet cells
What layer of the mucosa is scant in the stomach?
Lamina
What type cell in the gastric gland cells produce intrinsic factor?
Parietal cells
What do chief cells produce?
Pepsin
What extra layer is added to the muscularis in the stomach?
Inner oblique layer
What is the only enzymatic digestion that occurs in the stomach?
Protein degradation
What is rennin
Digests casein in infants
What is pepsin?
Protein digesting enzyme
What does protein degradation denature?
HCl
What does gastrin do?
Stimtulates secretion of enzymes, HCl & other hormones
What are the three phases of gastric secretion?
Cephalic (reflex)
Gastric
Intestinal
What triggers the cephalic phase in gastric secretion?
Aroma, taste, sight or thought of food
Conditioned reflex
What does the cephalic phase of gastric secretion do?
Prepares stomach for digestion
What happens during the gastric phase of gastric secretion?
Distention- stimulates stretch receptors
Causes impulses to medulla along vagus
Gastrin stimulates HCl production
When does the intestinal phase of gastric secretion starts?
When food enters small intestine
What is the excitatory subphase of intestinal secretion?
Presence of acidic chyme in small intestine causes intestine to release gastrin- stimulates gastric glands to produce even more HCl
What are the two subphases of the intestinal phase?
Excitatory subphase
Inhibitory subphase
What sets peristalic wave rate in the stomach?
Pacemaker cells
How much chyme enters the small intestine at a time?
3 ml
What are the three surface area modifications in the small intestine?
Plicae circularis
Villi
Microvilli
What do the plicae circularis do/ where are they found?
Slow chyme and mix with digestive juices
Cork-screwed shaped
Found in duodenum
What do the villi look like?
Finger like projections
What is found in villli?
Lamina propria
Capillary bed
lacteal (lymph cell for fat)
What is microvilli?
Brush border (+ their enzymes) Increases surface area
Where are paneth cells found?
interstinal crypts
What do Paneth cells do?
Secrete lysozyme
What does bile do?
Emulsifies fats- facilitates digestion (makes fat water soluble)
What works with the gallbladder to produce and store bile
Liver
What are the three vessels at the portal triad?
hepatic arteriole
portal venule
bile duct
(there will also be lymph)
What is the main function of the hepatocytes?
Form bile
What do hepatocytes do with glucose?
Store and release it
What other things does the liver store?
Fat-soluble vitamins
Amino acids
what are the cells that are macrophages in liver sinusoids?
Kupffer’s Cells
How is bilirubin formed?
From heme; happens in liver
What happens to the bilirubin in the small intestine?
Converted in small intestine to urobilinogen- brown pigment
what do bile salts do?
Emulsify fats in small intestine (reabsorbed in ilium for resection)
What layer of the alimentary canal is areolar tissues covered with mesothelium?
Serosa
What layer of the alimentary canal is fibrous connective tissue that blends with surrounding structure? What does it cover
Adventitia
Esophagus, rectal canal, parts of retroperitoneal
What does the submucosal nerve plexus control?
Glands and secretions of submucosa
What does the myenteric nerve plexus control?
Muscles of muscularis
What is found in saliva?
Salivary amylas, lysozyme, IgA, metabolic wastes, mucin
Does any absorption take place in the mouth, pharynx or esophagus?
No
What enables chemical digestions in the mouth?
salivary amylase
What are the four types of gastric gland cells?
Mucous neck cells
Parietal cells
Chief cells
Enteroendocrine cells
What is the purpose of the inhibitory subphase of the intestinal phase?
Protects small intestine from acidic chyme
Inhibition of gastric gland secretion
Pyloric sphincter tightens
In the small intestines, what type (histology) cells are in the mucosa layer?
Simple columnar cells
What type of cells are found in the mucosa in the small intestine?
Absorptive cells
goblet cells
enteroendocrine cells
T cells
What are most enzymes in the small intestine associated with?
Brush border
What emulsifies fats and facilitates digestion?
Bile
What is in the center of each liver lobule?
Central vein, blood travels here over hepatocytes through sinusoids
What is bile released into for transport to the triad?
Canaliculi
What does the liver store?
Glucose, fat-soluble vitamins, amino acids
What are macrophages that live in liver sinusoids?
Kupffer’s Cells
What do Kuppfer’s Cells do?
Remove bacteria and worn RBCs
What is bilirubin converted to in the small intestine
Urobilinogen (brown pigment)
What does cholecystokinin cause?
The gallbladder to contract and stimulate secretion of pancreatic enzymes
What does secretin trigger?
The liver to make more bile
pancreatic production of bicarbonate
What are the endocrine islands in the pancreas?
Islets of Langerhans
What are the exocrine portion of the pancreas?
Acinar tissue
What is produced in the Islets of Langerhans?
Insulin
Glucagon
Somatostatin
What is produced in the acinar tissue?
Enzymes
Bicarbonate ions
What are these:
Trysinogen
Procarboxypeptidase
Chymotripsinogen
Proteases produced by the pancreas.
Turn into active form when they reach the small intestine
What produces gas and acidity in the large intestine?
Ferment undigestible carbs
What vitamins are synthesized in the large intestine?
B complex and K vitamins
What are the two types of the propulsions that happen in the large intestine?
Haustral contraction
Mass movements
What is absorbed in the large intestine
Mainly water
ions, vitamins
What is enzymatic hydrolysis?
“split with water”
catabolic process where complex molecules are broken into simple molecules
What are the three type of carbohydrate monomoers
Glucose
Galactose
Fructose
Where does carbohydrate digestion occurs?
Mouth and small intestine
How does fructose cross barriers to get reabsorbed?
Facilitated diffusion
What is the only type of nutrient that is digested in the stomach?
Protein
These are all _____ enzymes
Trypsin
Chymotrypsin
Carboxypeptidase
pancreatic
These are all ____ enzymes
Aminopeptidase
Carboxypeptidase
Dipeptidase
Brush border
What cleaves between tyrosine and phenylalanine?
Pepsin
What digests casein (infants only)?
Rennin
What hydrolyzes aa one at a time from the C terminus?
Carboxypeptidase
What do these two enzymes do:
aminopeptidase
Dipeptidase
Liberate final aa products
What does lipase do?
Produces two free fatty acid and monoglyceride
Where are bile salts absorbed?
Ileum of small intestine
What is the main form of absorption
Active transport
In transepithelial transport, uptake occurs on the ____ side, exocytose occurs on the ____ side
Apical
Basal
Whole proteins are only absorbed in ____
infants
What is a collection of fatty elements and bile salts?
Micelle
Where do micelles break apart in order to be absorbed?
Near apical surface then lipid diffuse into epithelial cell
What is produced in the cytoplasm of epithelium cell when triglycerides combine with phospholipids and cholesterol
Chylomicrons
What hydrolyzes triglycerides in capillaries?
Lipoprotein lipase
Does fat go through the liver?
No, enter lymph system via lacteals
How are fat soluble vitamins absorbed?
Incorporated into micelles
Where is iron and calcium absorption limited to?
Duodenum
How is sodium absorbed?
Coupled to cotransport of glucose and amino acids
What are chloride ions actively transported in exchange for?
Bicarbonate
How are potassium ions reabsorbed?
Vita simple diffusion (osmotic gradients)
Where is iron actively transported into?
Mucosa cells
What is calcium locally regulated by?
Vitamin D
What is water uptake coupled to?
Sodium uptake