GI - Structure & Function Flashcards by Justin Bynum

What’s the major function of the GI tract?

Mechanical & Chemical Breakdown

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This is a hollow tube that extends from the mouth to the anus.

GI Tract

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The walls of the GI tract have several layers, what are they?

1) Mucosa
2) Muscularis mucosae
3) Submucosa
4) Tunica muscularis (Circular & Longitudinal muscle)
5) Serosa

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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
Enteric
Hormones

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Digestion begins with the mouth with chewing & salivation. What’s the digestive component of saliva?

Alpha-amylase

-Initiates carb digestion

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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

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What term describes how the food is propelled through the GI tract by the tunica muscularis?

Peristalsis

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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

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What has to open to admit swallowed food into the stomach and then closes to prevent regurge?

Lower esophageal sphincter

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The stomach is a baglike structure that ________ digestive juices, ______ and ______ food, and _______ partially digested food (chyme) into the duodenum.

Secretes
Mixes & Stores
Propels/Moves

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What are the smooth muscles of the stomach?

Outer longitudinal
Middle circular
Internal oblique

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What nerve stimulates gastric (stomach) secretion and motility?

Vagus

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What hormones stimulate & delay gastric emptying?

Stimulate = Gastrin & Motilin

- Delay = Secretin & Cholecystokinin

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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.

Intrinsic Factor

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What cells in the stomach secrete pepsinogen & what’s pepsinogen converted to in the acid environment created by hydrochloric acid?

Chief cells

- Pepsin

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What stimulates acid secretion?

1) Vagus nerve
2) Gastrin
3) Histamine

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What inhibits acid secretion?

1) Sympathetic stimulation

2) Cholecystokinin

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What NT stimulates pepsin secretion?

Acetylcholine

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What is the function of mucus in the stomach?

Protection of the stomach wall from acid and digestive enzymes

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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)

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What 3 segments make of the small intestines?

1) Duodenum
2) Jejunum
3) Ileum
- 5m total length

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What occurs in the small intestines?

Digestion and absorption of all major nutrients & most ingested water occurs in SI

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The peritoneum is a double layer of membranous tissue that contains what two layers?

1) Visceral (covers ab. organs)

2) Parietal (along ab. wall)

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What is the primary blood supply to the SI provided by?

Superior Mesenteric Artery

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The duodenum receives chyme from the stomach through what valve?

Pyloric 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 _________ & _________.

- Liver | - Digestion & Absorption

Biles alkalinity helps neutralize ______, thereby creating a pH that enables the _________ enzymes to digest proteins, carbs, & sugars.

- Chyme | - Pancreatic

What are enzymes secreted by the small intestines that act in SI to digest Cabs, Pros, & Fats?

1) Maltase 2) Sucrose 3) Lactase

What are the Pancreatic enzymes that act in the SI for digestion of macronutrients?

1) Proteases 2) Amylase 3) Lipase

Besides SI & Pancreatic enzymes, what other substance is needed to aid in digestion w/in the SI of Macronutrients?

Bile salts

Digested substances are absorbed across the _________ wall and then transported to the _______ through the _______ vein, where they are metabolized further.

- Intestinal - Liver - Portal

What valve connects the small and large intestines and prevents reflux into the small intestine?

Ileocecal valve

What are the small, finger-like projections that extend from the SI mucosa and increase its absorptive surface area?

Villi

Sugars, AA's, and Fats are absorbed primarily by the ______ & ______; bile salts and Vit. B12 are absorbed by the _______.

- Duodenum & Jejunum | - Ileum

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.

- Hydrolyze - Micelles - Brush

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) - Lymphatics - Liver

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?

Ileogastric reflex

This reflex inhibits intestinal motility when one's intestinal segment is over distended?

Intestinointestinal reflex

This reflex increases intestinal motility when gastric motility increases?

Gastroileal Reflex

What does the large intestine consist of? (parts)

1) Cecum 2) appendix 3) Colon: Ascending, Transverse, Descending & Sigmoid 4) Rectum 5) Anal Canal

These are three bands of longitudinal muscle that extend the length of the colon?

Teniae Coli

These are pouches of colon that are formed with alternating contraction and relaxation of the circular muscles?

Haustra

The mucosa of the _______ intestine contains mucus-secreting cells and mucosal folds, but no _____.

- Large | - Villi

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.

- Gastrocolic | - Propulsion

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?

Colon | -Anaerobes consist of Bacteroides, Clostridia, Coliforms, & Lactobacilli

The intestinal tract is ______ at birth and becomes totally colonized within __ to __ weeks.

- Sterile | - 3-4 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?

1) Digestive 2) Metabolic 3) Hematologic 4) Vascular 5) Immunologic

What are the ligaments that support the liver?

1) Falciform 2) Round 3) Coronary

What are the functional cells of the liver?

Plates of hepatocytes

What artery supplies blood to the liver?

Hepatic artery

What vein receives from the inferior and superior mesenteric veins?

Portal vein

What are the small channels that hepatocytes secrete bile into & these channels drain bile into the common bile duct and then to the duodenum?

Bile Canaliculi

What are the capillaries located b/w the plates of the hepatocytes?

Sinusoids

What is the name of the cells that are part of the mononuclear phagocyte system, line the sinusoids and destroy microorganisms in sinusoidal blood?

Kupffer cells

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.

- Cholesterol - Bile Salts - Deconjugation

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?

Bilirubin

Fat absorbed by intestinal lacteals is primarily ___________, which are hydrolyzed to _______ and _____ ______ _____.

- Triglycerides - Glycerol - 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?

Gallbladder

Stimulated by ___________, the gallbladder contracts and forces bile through the _____ duct and into the _____ bile duct.

- Cholecystokinin - Cystic - Common

This is a gland located behind the stomach that has endocrine and exocrine functions?

Pancreas

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?

1) Trypsin 2) Chymotrypsin 3) Carboxypeptidase 4) a-amylase 5) Lipase

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.

- Acini | - Common

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.

- Gastric - Stool - Blood

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

Aging reduces gastric motility and secretions, particularly of __________ ______. These changes slow gastric ________ & ________.

- Hydrochloric Acid - Digestion - Emptying

GI - Structure & Function Flashcards

(82 cards)