Flashcards in GI - Structure & Function Deck (82):
What's the major function of the GI tract?
Mechanical & Chemical Breakdown
This is a hollow tube that extends from the mouth to the anus.
The walls of the GI tract have several layers, what are they?
2) Muscularis mucosae
4) Tunica muscularis (Circular & Longitudinal muscle)
Except for swallowing and defecation, which are controlled voluntarily, the functions of the GI are controlled by _________ & _________ autonomic nerves...collectively called the ________ plexus and intestinal __________.
-Intrinsic & Extrinsic
Digestion begins with the mouth with chewing & salivation. What's the digestive component of saliva?
-Initiates carb digestion
The esophagus is a muscular tube (tunica muscularis) that transports food from the mouth to stomach. What are the two muscle types w/in the esophagus?
-Upper = striated
-Lower = smooth muscle
What term describes how the food is propelled through the GI tract by the tunica muscularis?
Swallowing is controlled by the swallowing center in the reticular formation of the brain. What are the two phases of swallowing?
1) Voluntary - Oropharyngeal
2) Involuntary - Esophageal
What has to open to admit swallowed food into the stomach and then closes to prevent regurge?
Lower esophageal sphincter
The stomach is a baglike structure that ________ digestive juices, ______ and ______ food, and _______ partially digested food (chyme) into the duodenum.
-Mixes & Stores
What are the smooth muscles of the stomach?
What nerve stimulates gastric (stomach) secretion and motility?
What hormones stimulate & delay gastric emptying?
-Stimulate = Gastrin & Motilin
-Delay = Secretin & Cholecystokinin
Gastric glands in the funds and body of the stomach secrete this, which is needed for Vit. B12 absorption, and hydrochloric acid, which dissolves food fibers, kills microorganisms, and activates the enzyme pepsin.
What cells in the stomach secrete pepsinogen & what's pepsinogen converted to in the acid environment created by hydrochloric acid?
What stimulates acid secretion?
1) Vagus nerve
What inhibits acid secretion?
1) Sympathetic stimulation
What NT stimulates pepsin secretion?
What is the function of mucus in the stomach?
Protection of the stomach wall from acid and digestive enzymes
What are the three phases of acid secretion by the stomach?
1) Cephalic phase (anticipation & swallowing)
2) Gastric phase (Food in stomach)
3) Intestinal phase (Chyme in intestines)
What 3 segments make of the small intestines?
-5m total length
What occurs in the small intestines?
Digestion and absorption of all major nutrients & most ingested water occurs in SI
The peritoneum is a double layer of membranous tissue that contains what two layers?
1) Visceral (covers ab. organs)
2) Parietal (along ab. wall)
What is the primary blood supply to the SI provided by?
Superior Mesenteric Artery
The duodenum receives chyme from the stomach through what valve?
The presence of chyme in the duodenum stimulates this to occur from liver, gallbladder, & pancreas?
-Liver & GB = Bile
-Pancreas = Digestive enzymes and alkaline secretions
Bile and enzymes flow into the duodenum through an opening guarded by what sphincter?
Sphincter of Oddi
Bile, produced in the ______ is necessary for fat _________ & _________.
-Digestion & Absorption
Biles alkalinity helps neutralize ______, thereby creating a pH that enables the _________ enzymes to digest proteins, carbs, & sugars.
What are enzymes secreted by the small intestines that act in SI to digest Cabs, Pros, & Fats?
What are the Pancreatic enzymes that act in the SI for digestion of macronutrients?
Besides SI & Pancreatic enzymes, what other substance is needed to aid in digestion w/in the SI of Macronutrients?
Digested substances are absorbed across the _________ wall and then transported to the _______ through the _______ vein, where they are metabolized further.
What valve connects the small and large intestines and prevents reflux into the small intestine?
What are the small, finger-like projections that extend from the SI mucosa and increase its absorptive surface area?
Sugars, AA's, and Fats are absorbed primarily by the ______ & ______; bile salts and Vit. B12 are absorbed by the _______.
-Duodenum & Jejunum
Bile salts emulsify and _______ fats and incorporate them into water-soluble ________ that transport them through the unstirred layer to the _______ border of the intestinal mucosa.
The fat content of the micelles readily diffuses through the epithelium into _______ in the villi. From there fats flow into __________ and into the systemic circulation, which delivers them to the ______.
-Lacteals (Lymphatic ducts)
Minerals and water-soluble vitamins are absorbed by _____ & _____ transport throughout the SI.
-Passive & Active
What are the jobs of the longitudinal & circular muscles of the intestines?
-Longitudinal = propels chyme along
-Circular = mix chyme & promote digestion
This is a reflex that inhibits gastric motility when the ileum is distended?
This reflex inhibits intestinal motility when one's intestinal segment is over distended?
This reflex increases intestinal motility when gastric motility increases?
What does the large intestine consist of? (parts)
3) Colon: Ascending, Transverse, Descending & Sigmoid
5) Anal Canal
These are three bands of longitudinal muscle that extend the length of the colon?
These are pouches of colon that are formed with alternating contraction and relaxation of the circular muscles?
The mucosa of the _______ intestine contains mucus-secreting cells and mucosal folds, but no _____.
What are two functions of the large intestine?
1) Massage of the Fecal mass
2) Absorbs water & electrolytes
Distention of the ileum with chyme causes the _________ reflex, or the mass __________ of feces to the rectum.
When is defecation stimulated?
-When the rectum is distended with feces
For defecation to occur after stimulation, what has to happen with sphincters?
Internal relaxes & External also has to voluntarily relax
Where are the largest number of intestinal bacteria located?
-Anaerobes consist of Bacteroides, Clostridia, Coliforms, & Lactobacilli
The intestinal tract is ______ at birth and becomes totally colonized within __ to __ weeks.
What are three ways that endogenous infections of the GI tract occur?
1) Excessive proliferation
2) Perforation of intestine
3) Contamination from neighboring structures
What is the functions of the liver?
What are the ligaments that support the liver?
What are the functional cells of the liver?
Plates of hepatocytes
What artery supplies blood to the liver?
What vein receives from the inferior and superior mesenteric veins?
What are the small channels that hepatocytes secrete bile into & these channels drain bile into the common bile duct and then to the duodenum?
What are the capillaries located b/w the plates of the hepatocytes?
What is the name of the cells that are part of the mononuclear phagocyte system, line the sinusoids and destroy microorganisms in sinusoidal blood?
The primary bile acids are synthesized from __________ by the hepatocytes. The primary acids are then conjugated to form _____ _____. The secondary bile acids are the product of bile salt ___________ by bacteria in the intestinal lumen.
Most bile salts and acids are recycled. What's the absorption of bile salts and acids from the terminal ileum and their return to the liver known as?
Enterohepatic circulation of bile
What is a pigment liberated by the lysis of aged red blood cells in the liver and spleen?
Fat absorbed by intestinal lacteals is primarily ___________, which are hydrolyzed to _______ and _____ ______ _____.
-Free Fatty Acid
What is the saclike organ located in the inferior surface of the liver that stores bile b/w meals and ejects it when chyme enters the duodenum?
Stimulated by ___________, the gallbladder contracts and forces bile through the _____ duct and into the _____ bile duct.
This is a gland located behind the stomach that has endocrine and exocrine functions?
What are the endocrine pancreas hormones?
Glucagon & Insulin
What is the exocrine pancreas alkaline solution and enzymes that are secreted and digest proteins, carbs, & fats?
What stimulates the pancreas to secrete alkaline fluid and enzymes?
Alkaline fluid = Secretin
Enzymes = Cholecystokinin & Ach
Pancreatic secretions originate in _____ and ducts of the pancreas and empty into the duodenum through the ______ bile duct or an accessory duct that opens directly into the duodenum.
What are the most commonly used tests to evaluate structure in addition to direct observation by endoscopy?
Radiographs & Scans
______ & ______ analysis and ______ studies provide important info about digestion, absorption and secretion.
What are commonly used to used to Dx alterations in liver function?
Plasma chemistry levels and imaging procedures
What are the enzymes of particular importance when assessing plasma chemistry levels?
LDH, AST, & ALT
What does plasma bilirubin levels reflect?
Alterations in bilirubin & bile metabolism
What liver issues may manifest in prolonged prothrombin times?
Hepatitis & Chronic Liver Disease
What is indicative of obstructive disease of the gallbladder?
Elevated serum bilirubin
Elevated Urine urobilinogen
Increased Fat stool
What's the most significant indicators of pancreatic dysfunction?
Serum amylase & Stool fat
-Both will be increased