Gastrointestinal System Quiz

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Questions and Answers

What is the primary role of Peyer's Patches in the gastrointestinal tract?

Producing gastric acid for digestion

Facilitating muscular contractions in the stomach

Participating in immune surveillance (correct)

Absorbing nutrients from digested food

Which muscle layer of the stomach is specifically noted for its role in churning food?

Submucosal layer

Circular layer

Oblique layer (correct)

Longitudinal layer

What is the innermost layer of the gastrointestinal tract?

Mucosa (correct)

Submucosa

Serosa

Muscularis

Which of the following statements about the jejunum is true?

It has tall villi but less than in the duodenum. Signup and view all the answers

What is another name for the myenteric plexus?

Auerbach's plexus Signup and view all the answers

What role does the pyloric sphincter play in digestion?

Regulates the passage of food into the duodenum Signup and view all the answers

What type of plexus is the submucosal plexus also referred to as?

Meissner's plexus Signup and view all the answers

Which of the following statements accurately describes Crohn's Disease?

It features transmural inflammation and may form fistulas. Signup and view all the answers

What is the primary function of the duodenum in the small intestine?

Serve as the main site for enzymatic activity and mixing chyme. Signup and view all the answers

Which motility movement in the small intestine is characterized by circular muscle contractions?

Segmentation Signup and view all the answers

During swallowing, what occurs in the body?

The epiglottis tilts over the glottis while the UES relaxes. Signup and view all the answers

What is NOT a characteristic of ulcerative colitis?

Presence of skip lesions. Signup and view all the answers

Which of the following conditions is classified under esophageal dysmotility?

GERD Signup and view all the answers

What is the primary role of the colon in the gastrointestinal system?

Transporting waste and absorbing water. Signup and view all the answers

Which type of motility involves large coordinated contractions in the colon?

Peristalsis Signup and view all the answers

What aspect of gastric motility is responsible for allowing food to enter the stomach?

Accommodation of the fundus. Signup and view all the answers

Which hormone is primarily affected by ACTH in terms of stimulation of the adrenal cortex?

Glucocorticoids Signup and view all the answers

What is the primary clinical feature of prolactinoma in males?

Testicular atrophy Signup and view all the answers

What diagnostic method is primarily used to assess growth hormone underproduction?

Insulin-induced hypoglycemia test Signup and view all the answers

What abnormality is characterized by increased levels of ACTH and cortisol, but decreased CRH?

Cushing’s Disease Signup and view all the answers

Which treatment is typically used for overproduction of growth hormone?

Transsphenoidal hypophysectomy Signup and view all the answers

Which condition results in elevated levels of CRH and ACTH while cortisol levels drop?

Adrenal Insufficiency Signup and view all the answers

What is a typical symptom of a pituitary mass effect on the optic chiasm?

Bitemporal hemianopia Signup and view all the answers

Which of the following treatments is not appropriate for Cushing’s Syndrome management?

Dopaminergic agents Signup and view all the answers

What is the primary clinical manifestation of underproduction of growth hormone?

Malaise Signup and view all the answers

What reveals the most cortisol in a healthy individual during the day?

AM measurement Signup and view all the answers

What initiates the secretion of insulin in pancreatic beta cells?

Increase in glucose uptake via GLUT-2 Signup and view all the answers

Which pathway is directly involved in promoting beta cell mass and insulin production?

cAMP pathway Signup and view all the answers

In type II diabetes mellitus, which factor is primarily associated with insulin resistance?

Decreased adiponectin levels Signup and view all the answers

Which of the following complications is NOT commonly associated with diabetes?

Gastroenteropathy Signup and view all the answers

What is the most common viral cause of type I diabetes mellitus?

Mumps virus Signup and view all the answers

What does the process of glycosylation result in within the context of diabetic microvascular disease?

Formation of advanced glycosylated end products (AGEs) Signup and view all the answers

Which mechanism do viruses primarily use to enhance their virulence?

Adherence to host cells for prolonged propagation Signup and view all the answers

In diabetic nephropathy, which factor can contribute significantly to the risk of its development?

Strong genetic disposition to kidney disease Signup and view all the answers

What is the significance of the GLUT-2 transporter in glucose metabolism?

It facilitates glucose entry into liver and beta cells Signup and view all the answers

What best describes the accumulation of polyols and advanced glycosylated end products (AGEs) in diabetic complications?

They contribute to small vessel damage. Signup and view all the answers

What is the role of Glycoprotein 120 (GP120) in HIV adherence?

It binds to CD4 receptors and recruits chemokines. Signup and view all the answers

Which mechanism of adherence is specifically associated with Gram (-) bacteria?

Binding via antigens on flagella, pili, or fimbriae. Signup and view all the answers

What is the primary function of fimbriae in bacteria such as E. coli?

Enabling adherence to host cells. Signup and view all the answers

What is the effect of LPS (lipopolysaccharide) in E. coli pathogenesis?

It acts as an endotoxin promoting inflammatory responses. Signup and view all the answers

What characteristic is NOT associated with the mechanism of adherence for viruses?

Use of peptidoglycans for attachment. Signup and view all the answers

Study Notes

Gastrointestinal Pathophysiology

The GI tract has 4 layers: serosa (outermost), muscularis (longitudinal and circular layers with myenteric and submucosal plexuses), submucosa, and mucosa (innermost).
The enteric plexus is made up of the myenteric and submucosal plexuses. The submucosal plexus is also called Meissner's plexus, and the myenteric plexus is also called Auerbach's plexus.
Peyer's patches in the mucosa are key players in immune surveillance for the GI tract.
Small intestine has 3 parts: duodenum, jejunum, and ileum.
Duodenum: tall layer of mucosa, many villi for nutrient absorption, and does the most absorption.
Jejunum: tall villi but less than in duodenum.
Ileum: short, tightly packed villi.
Stomach has 3 muscle layers: longitudinal, circular, and oblique.
The lower esophageal sphincter (LES) prevents reflux.
The pyloric sphincter prevents food from moving into the duodenum until it's churned and mixed with stomach acid.
Stomach lining has multiple cell types.
Chief cells produce pepsinogen.
Parietal cells produce hydrochloric acid (HCl) and intrinsic factor.
G cells produce gastrin.
Endocrine cells produce somatostatin and histamine.

GI Tract Circulation

Oxygenated blood circulates to GI organs via branches of the abdominal aorta (hepatic artery to liver, celiac artery to stomach, spleen, and pancreas, superior mesenteric artery to pancreas, small intestine, and proximal colon, and inferior mesenteric artery to distal colon and rectum).
Deoxygenated blood from GI organs drains into the portal vein, which carries it to the liver for processing.
Liver is the major glycogen storage site.

Process of Acid Secretion

Gastric acid secretion is stimulated by vagal nerve stimulation (acetylcholine), gastrin, and histamine.
H2 antagonists inhibit acid secretion.
Fasting gastric pH is around 5-5.5.
Eating stimulates HCl secretion, leading to gastric pH around 1.5.

Process of HCl Production

CO2 in the blood enters parietal cells and combines with H2O to form carbonic acid (H2CO3).
Carbonic anhydrase cleaves carbonic acid into bicarbonate (HCO3-) and a proton (H+).
Bicarbonate is secreted back into the blood in exchange for chloride (Cl-).
Proton is secreted into the stomach lumen by the H+/K+-ATPase pump.
H+ and Cl- combine to form HCl in the stomach lumen.

Peptic Ulcers

Peptic ulcers occur when there is an imbalance between damaging (acid) and protective (mucosal) forces.
Duodenal ulcers are most commonly found in the first portion of the duodenum.
Gastric ulcers are caused by a deficiency in mucin production.
H. pylori is a major cause of peptic ulcers.
NSAIDs are a major cause of gastric ulcers.

Digestion and Absorption of Carbs

Carbohydrate digestion begins in the mouth with salivary amylase, breaking down carbs into polysaccharides.
Pancreatic amylases travel through the pancreatic duct to the duodenum. This aids in digestion of carbohydrates.
Enzymes in the brush border of the small intestine (lactase, sucrase, and maltase) further break down polysaccharides into monosaccharides (glucose, galactose, and fructose).
These monosaccharides are absorbed into the bloodstream via a sodium-glucose cotransporter.

Digestion and Absorption of Proteins

Pepsin and HCl in the stomach break down proteins into smaller peptides (proteoses and peptones).
Pancreatic enzymes (trypsin, chymotrypsin, and carboxypeptidase) further break down proteoses and peptones.
Enzymes in the brush border of the small intestine (aminopeptidases and dipeptidases) break down these peptides into amino acids.
Amino acids are absorbed via proton amino acid antiporter and a sodium-amino acid symporter and transported to the liver.

Digestion and Absorption of Fats

Bile salts emulsify fats.
Pancreatic lipase breaks down fats into monoglycerides and glycerol.
Monoglycerides and glycerol are absorbed through lacteals and transported to the liver via the lymphatic circulation.
Short-chain fatty acids are absorbed by capillaries in the villi and travel to the liver via the portal vein.

Absorption and Secretion

Different sections of the GI tract absorb specific nutrients.
Stomach: alcohol
Duodenum: most nutrients due to tightly packed villi.
Ileum: vitamin B12.
Electrolytes are absorbed and secreted via various transporters throughout the GI tract, including sodium, chloride, and bicarbonate

Electrolyte Transport

Absorption moves materials from the GI tract to the extracellular fluid (ECF).
Secretion moves material from the ECF to the lumen of the GI tract.
Sodium is transported by proton exchangers, chloride transporters, and glucose cotransporters in the duodenum and jejunum.
Duodenum and jejunum have "leaky epithelium," enabling H2O and electrolytes to move through gap junctions.
Terminal ileum and colon primarily use chloride/bicarbonate exchangers and sodium-chloride cotransporter for electrolyte transport.
Diarrhea results in loss of bicarbonate in feces as a result of bicarbonate secretion in the ileum/colon, causing metabolic acidosis.
The terminal colon has a sodium channel for absorption.

Diarrhea

Diarrhea is increased stool mass, fluidity, or frequency typically > 200 grams per day.
Four types: secretory (isotonic, persistent, doesn't resolve with fasting), osmotic (excess water drawn into the bowels by solutes inhibiting normal absorption), malabsorptive (inability to absorb nutrients, resolves with fasting), and exudative (purulent, bloody, doesn't resolve with fasting).

Bacterial Causes of Diarrhea

Key information on various bacterial causes of diarrhea (e.g., Cholera - "rice water stools," Salmonellosis, Enterotoxigenic E. coli, Enterohemorrhagic E. coli). Includes transmission, geography, symptoms, and potential complications.

Cholera

Cholera toxin has an alpha and beta subunit.
Cholera toxin stimulates the enzyme adenylate cyclase, converting ATP into cAMP.
cAMP opens chloride channels, leading to chloride exiting cells and water following.
End result is profuse watery diarrhea.

Celiac Disease

Celiac disease is an autoimmune disease.
Ingested gluten is metabolized into gliadin.
Gliadin is deamidated by tissue transglutaminase (tTG).
Deamidated gliadin triggers an immune response, leading to damage of villi and crypt elongation, and thinning and loss of intestinal epithelium.

Inflammatory Bowel Disease (IBD)

The exact cause of IBD is unknown but likely familial.
Certain bacteria permeate the epithelium more readily in IBD than in healthy individuals.
Dendritic cells take up these bacteria, initiating an immune response (e.g., TH1 → macrophages and cytotoxic T cells).
Key component of inflammatory process is TNF-alpha.

Crohn's Disease vs. Ulcerative Colitis

Crohn's disease: skip lesions throughout the ileum to colon (may be transmural).
Ulcerative colitis: continuous lesions affecting only the colon—no skip lesions, mucosal lesions only.

GI Motility

Swallowing involves contraction of the UES, relaxation of the UES, and epiglottis moving over the glottis.
Stomach motility includes accommodation (fundus and proximal ⅓ of corpus relax to allow food entry) and emptying (remaining corpus, antrum, and pylorus grind and sieve solids to pass into duodenum).
Small intestine motility involves propagation (wavelike peristalsis), segmentation (circular muscle constricts to mix chyme), and pendular movement (longitudinal muscle shortens and lengthens the intestine).
Colonic motility includes repetitive, non-propulsive contractions to mix waste into stool form and propagating stool forward.

Motility Disorders

Esophageal dysmotility includes GERD, achalasia, dysphagia, and strictures. Stomach dysmotility includes gastroparesis. Colonic dysmotility includes constipation and diarrhea.

Colon Cancer

Normal colon → mucosa at risk → adenomas → carcinoma. (memorize driving mutations at each stage)

Liver, Bile, and Bilirubin Metabolism

Liver functions include making bile, proteins, cholesterol, and storing glycogen.
Liver clears toxins. Processes hemoglobin. Stores iron.
Functional unit: hepatocyte—centered around central veins; drains filtered blood; bile from canaliculi goes to gallbladder.
Bile is made in the liver and stored in the gallbladder.
Bile is made up of bile salts, bilirubin, water, electrolytes, and phospholipids.
Bile salts emulsify fats, lipids are absorbed in the jejunum, bile salts are absorbed in the terminal ileum (95% recycled).
Cholesterol excretion/bile acid resins prevent reabsorption (cholestyramine and colestipol and colesevelam).

Bilirubin Metabolism

RBC breakdown yields heme, which becomes biliverdin and then unconjugated bilirubin.
Unconjugated bilirubin is combined with glucuronic acid (in the liver) becoming conjugated bilirubin (water soluble).
Conjugated bilirubin is excreted in the stool.

Slanchnic Circulation

Blood flow to GI organs (supplied by the celiac artery, superior mesenteric artery, and inferior mesenteric artery) is drained through the portal vein which circulates to liver and processed.
Processed deoxygenated blood is sent through the hepatic veins to the inferior vena cava.

Cirrhosis

Chronic liver disease that results in healthy liver tissue being replaced by scar tissue (fibrosis).
Inflammation and production of II-1, TNF, and TGFB stimulate stellate cells to differentiate into myofibroblasts.
Myofibroblasts produce collagen, leading to progressive fibrosis.
Kupffer cells release cytokines, promoting hepatocyte death.

Gallstones and Cholecystitis

Gallstones (cholelithiasis): Most common are cholesterol stones (formed by excess fat in bile or stasis), or pigment stones (caused by excess bilirubin, e.g., alcohol excess or parasites)

Pancreas

Pancreas functions include endocrine (islet cells produce insulin and glucagon) and exocrine (acinar cells produce enzymes for digestion of proteins and fats).

Leptin and Ghrelin

Leptin, ghrelin, and adiponectin help the body balance caloric intake and expenditure.
Leptin increases energy expenditure and decreases weight gain.
Ghrelin stimulates fat building and encourages feeding desire.
Adiponectin is involved in inhibiting aging and increasing energy expenditure.

Endocrinology

Hormones are substances produced by one cell to act on a different cell.
Hormones act through two modes of action: cell membrane (non-steroid hormones e.g., tyrosine kinases, cytokine receptors, G-protein coupled receptors) and nuclear (steroid hormones).
Feedback loops (positive and negative) regulate hormone levels.

Hypothalamic/Pituitary Axis

The hypothalamic/pituitary axis coordinates most endocrine and nervous system messages.
The hypothalamus (control center in the brain) secretes hormones with direct effects on tissues, and hormones that regulate the production and secretion of other hormones.
Posterior Pituitary hormones affect water balance (ADH), reproductive system (OT), and stimulate the release of thyroid hormone, milk production, body growth, and metabolism.

Anterior Pituitary

Anterior pituitary is Glandular tissue that secretes substances into the blood. It has its own portal venous system.

Steroid and Non-steroid Hormones

Steroid hormones pass easily through the cell membrane (and bind to receptors inside). Non-steriod hormones do not pass easily through the cell membrane (and bind to receptors on the surface).

Pituitary Mass Effect

Symptoms of pituitary mass effect include bitemporal hemianopia (from optic chiasm compression), headache, and increased intracranial pressure (ICP).

Prolactinoma

Clinical features include galactorrhea, amenorrhea, and infertility in females and testicular atrophy, and sexual dysfunction in males.
Diagnosis through measurement of prolactin levels in blood and imaging techniques (e.g., MRI of the pituitary gland).
Treatment is via dopamine-receptor agonists and surgery.

Growth Hormone Abnormalities

Clinical features of growth hormone (GH) overproduction include gigantism (in children) and acromegaly (in adults).
Clinical features of GH underproduction include energy loss, malaise, and depression.
Diagnostics involve measuring GH (and possibly evoking response with insulin-induced hypoglycemia or arginine with GHRH).
Treatment involves surgery, radiation, and/or octreotide (antagonist) for over-production.
Treatment involves GH replacement for underproduction.

Adrenal Pathophysiology

Adrenal cortex layers include zona glomerulosa (aldosterone), zona fasciculata (cortisol), and zona reticularis (estrogens/androgens).
ACTH stimulates the adrenal gland, particularly to regulate glucocorticoids. It doesn't impact mineralocorticoids and sex hormones.

Cushing's Disease/Syndrome

Cushing's disease: ACTH-secreting pituitary adenoma causes excess cortisol production.
Cushing's syndrome: any condition causing excess cortisol (e.g., exogenous glucocorticoid use, adrenal tumors).
Diagnostics include measuring AM/PM cortisol and dexamethasone suppression test.
Treatment often involves surgery or radiation.

Addison's Disease (Primary Adrenal Insufficiency)

Autoimmune destruction/insufficient production of cortisol and aldosterone.
Presentation includes weight loss, malaise, hypotension, and Addisonian crisis.
Diagnostics include serum cortisol levels, a cosyntropin (synthetic ACTH) stimulation test.
Treatment includes glucocorticoid and mineralocorticoid replacement.

ACTH Abnormalities

Clinical features of overproduction often include obesity, proximal muscle weakness, glucose intolerance, etc.
Clinical features of underproduction often include weight loss, malaise, and hypoglycemia.
Diagnosis using AM/PM cortisol measurements, dexamethasone suppression/cortrosyn stimulation tests.
Treatment involves surgery, radiation, and/or cortisol/corticosteroid replacement.

Thyroid Pathophysiology

TSH binds to TSHR → stimulates production of thyroglobulin in Golgi→ transported to lumen→ upregulates the uptake of iodine→thyroid hormone synthesis.
Iodine is needed for thyroid hormone synthesis.

TSH Abnormalities

Clinical features of overproduction (rare) - thyromegaly, hyperthyroidism.
Clinical features of underproduction (common) - hypothyroidism.
Treatment is either surgery or radiation or octreotide for overproduction.
Treatment involves thyroid hormone replacement (levothyroxine) for underproduction.

Hyperthyroidism (Grave's Disease)

Symptoms include weight loss, nervousness, palpitations, tremor, weakness, and bowel frequency.
Signs include proptosis (bulging eyes), tachycardia, warm moist skin, myxedema, and hair loss.
Diagnosis involves measuring serum TSH, T3, and T4 levels; thyroid uptake scans.
Treatment includes anti-thyroid drugs, radioactive iodine, or surgery.

Hypothyroidism

Symptoms include tiredness, weight gain, cold intolerance, depression, and constipation.
Signs include delayed DTRs, non-pitting edema, coarse skin, bradycardia, and hypothermia.
Diagnosis involves measuring serum TSH, T3, and T4 levels.
Treatment includes thyroid hormone replacement (levothyroxine).

Pancreatic Endocrine Function

Pancreatic endocrine function is critical to regulating glucose levels by secreting insulin and glucagon.
Insulin facilitates glucose uptake to lower blood glucose levels.
Glucagon increases blood glucose.

Glucose Uptake in Cells

Different glucose transporter types: GLUT-1 in RBCs (no mitochondria - glycolysis), GLUT-3 in brain (purely glycolysis), GLUT-4 in muscle, adipose, and liver (glycogen pathway), and GLUT-2 in liver.

Insulin Secretion and Action

Insulin secretion is stimulated by elevated glucose levels, while inhibited by low glucose.
Insulin signaling pathways regulate glucose uptake, production of glycogen, gluconeogenesis, protein synthesis, and many other processes.

Carb Metabolism

Four major pathways: glycolysis, glycogenesis, gluconeogenesis, and glycogenolysis

Diagnostic Criteria for Diabetes

Pre-diabetes: Fasting blood glucose (FBG): 100–125mg/dL, postprandial BG 140-199mg/dL, and HgbA1C 5.7–6.4%.
Diabetes: FBG > 125mg/dL, postprandial >200mg/dL, and HgbA1C >6.4%.

Type I Diabetes

Autoimmune destruction of insulin-producing beta cells.
Leads to insulin deficiency → Diabetic ketoacidosis (DKA)
Diagnosis frequently through measurement of blood glucose, insulin, and ketones.

Type II Diabetes

Characterized by impaired glucose uptake and defective insulin secretion/action.
Often associated with genetic mutations and/or obesity-related hormone imbalances, e.g., decreased adiponectin, increased leptin.

Diabetic Complications

Microvascular disease (retinopathy, neuropathy, nephropathy).
Macrovascular disease (accelerated atherosclerosis related to lipid dysregulation).
Many complications associated with damage from AGE (advanced glycosylated end products).

Infectious Disease

Mechanisms of virulence include encounter, evasion of immune system, multiplication and spread, cell/tissue damage, shedding

Infection Sources

Endogenous infections – originate from within body tissues/organs/cells, e.g., skin, colon
Exogenous infections – originate from sources outside the body, e.g., viruses, bacteria, fomites, animals.

Mechanisms of Adherence

Viruses use receptors and proteins on viral capsids. Bacteria use peptidoglycans (gram positive) and various types of antigens (gram negative) that attach to cell surface molecules (e.g., pili, fimbria).
HIV uses glycoprotein p120 to bind to CD4 receptors and chemokines.

Infectious Disease Transmission

Direct transmission occurs when the disease is passed directly from one person or animal to another (e.g., person-to-person contact, droplets—coughing or sneezing, fecal-oral).
Indirect transmission occurs when a disease is transmitted without direct contact (e.g., via air, fomites).
Vector transmission requires another organism to transmit a disease from one person to another or from animal to person (e.g., insect bites).

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Description

Test your knowledge of the gastrointestinal tract with this quiz covering Peyer's patches, muscle layers of the stomach, and various functions of the intestines. Assess your understanding of conditions like Crohn's Disease and ulcerative colitis, as well as gastrointestinal motility movements. Suitable for students studying human anatomy and physiology.