WK3 Exam 1 Study Guide PDF

**Week 1 Study Guide: Upper Digestive System** 1. **[Organs of the Digestive System]** - **Gastrointestinal Tract (Alimentary Canal)** - **Structure:** Muscular tube approximately 16 feet long. - **Components:** Mouth, pharynx, esophagus, stomach, small intestine, large in...

**Week 1 Study Guide: Upper Digestive System** 1. **[Organs of the Digestive System]** - **Gastrointestinal Tract (Alimentary Canal)** - **Structure:** Muscular tube approximately 16 feet long. - **Components:** Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum. - **Accessory Organs** - **Function:** Aid digestion but not part of the GI tract. - **Components:** Teeth, tongue, salivary glands, liver, gallbladder, pancreas. 2. **Major Functions of the Digestive System** - **Ingestion:** Intake of food. - **Secretion:** Enzymes and glandular products introduced (e.g., saliva). - **Propulsion/Motility:** Movement and mixing of food (e.g., peristalsis). - **Digestion:** Breakdown of food mechanically and chemically. - **Absorption:** Uptake of nutrients and water into cells/blood/lymph. - **Compaction/Defecation:** Consolidation and elimination of waste as feces. 3. **Digestion Types** - **Mechanical Digestion** - **Process:** Physical breakdown (teeth, churning, segmentation). - **Location:** Mouth, stomach, small intestine. - **Chemical Digestion** - **Process:** Catabolic reactions breaking down macromolecules. - **Enzymes:** Produced by salivary glands, stomach, pancreas, small intestines. - **Location**: Mouth, stomach, small intestine. - **Salivary amylase**: enzyme that helps break down starch into simpler sugars.  - **Lingual lipase:** enzyme that breaks down dietary fat (lipids) in the mouth and stomach. 4. **Layers of the Gastrointestinal Tract** - **Mucosa (Deep):** Inner lining; includes epithelium, lamina propria, muscularis mucosae. - **Functions:** Digestion, nutrient absorption. - **Submucosa:** Loose connective tissue with blood vessels, lymphatics, nerve plexus. - **Functions:** Nutrient absorption, stimulus detection. - **Muscularis Externa**: Two layers of smooth muscle (longitudinal and circular). - **Special Feature**: Extra oblique muscle layer in the stomach. - **Functions:** Propulsion and mixing. - **Serosa (Superficial):** Areolar tissue with simple squamous mesothelium. - **Functions:** Support and surround GI tract. 5. **Propulsion and Motility** - **Peristalsis:** Contraction and relaxation pushing contents forward. - **Mixing Waves:** In the stomach to create chyme. - **Segmentation:** Separates contents for absorption. - **Haustral Churning:** Segmenting movements in the large intestine. - **Mass Movement:** Large peristaltic contractions in the large intestine. 6. **Mesenteric Peritoneum** - **Mesentery:** Double-layered peritoneum supporting intraperitoneal organs. - **Posterior Mesentery**: Suspends intestines. - **Anterior Mesentery:** Includes greater omentum (insulation/protection) and lesser omentum (stabilization). - **Peritoneal Folds** - **Parietal Layer**: Lines abdominopelvic cavity. - **Visceral Layer:** Covers abdominal/pelvic organs. - **Peritoneal Cavity:** Contains serous fluid to reduce friction. - **Positions Relative to Peritoneum** - **Intraperitoneal Organs:** Enclosed by mesentery (e.g., stomach, liver). - **Retroperitoneal Organs**: Covered only on anterior side (e.g., duodenum, pancreas). 7. **Upper Digestive System** - **Oral Cavity** - **Functions**: Ingestion, taste, chemical digestion, speech, respiration. - **Components**: Lips, cheeks, palate, uvula, tongue. - **Palate:** Hard (maxillae/palatine bones) and Soft (muscular). - **Tongue**: Contains papillae (taste buds) and aids in mastication and deglutition. - **Cranial Nerves** - 9 and 10 cranial nerves are important for digestion - 12 cranial nerves moves the tongue important for digestion too - **Teeth** - **Types:** Incisors, canines, molars. - **Structure:** Alveolus, cementum, enamel, dentin, pulp. - **Salivary Glands** - **Intrinsic Glands**: Moistening, secreting lingual lipase. - **Extrinsic Glands:** Parotid, submandibular, sublingual. - **Chemical Digestion in Oral Cavity** - **Saliva Composition**: Mucus, electrolytes, lysozymes, immunoglobulin A, salivary amylase, lingual lipase. - **Pharynx** - **Function:** Connects oral cavity to stomach. - **Regions:** Nasopharynx, oropharynx, laryngopharynx. - **Phases of Swallowing**: Oral, pharyngeal, esophageal. 8. **Esophagus** - **Function**: Transports bolus from pharynx to stomach. - **Composition:** Mucus-secreting esophageal glands. - **Sphincter:** Lower esophageal sphincter prevents reflux. - **Wall Composition** - **Cervical:** Skeletal muscle. - **Thoracic:** Mixed skeletal and smooth muscle. - **Abdominal:** Smooth muscle. 9. **Stomach** - **Regions:** Cardiac, fundus, body, pylorus. - **Endocrine Gland** - **Functions**: Churning, mixing, secretion of gastric juices and hormones. - **Layers of the Stomach Wall** - **Mucosa**: Contains mucous, parietal, chief, and G-cells. - **Submucosa:** Dense connective tissue. - **Muscularis** Externa: Three layers of muscle. - **Serosa:** Connective tissue continuous with peritoneum. - **Hydrochloric Acid Production** - **Process:** CO₂ and H₂O combine to form carbonic acid, which dissociates into hydrogen and bicarbonate ions. - **Functions:** Activates enzymes, breaks down connective tissues, denatures proteins, etc. - Stomach Curve towards the right (J shape) primary site physical and chemical digestion - Duodenum, the first part of the small intestine, the main site of absorption - Oblique muscle helps turn the bolus into chyme 10. **Accessory Organs** - **Liver** - **Endocrine Gland** - **Location:** Inferior to diaphragm, right hypochondriac and epigastric regions. - **Histology:** Hepatic lobules, sinusoids, Kupffer cells. - **Functions:** Metabolism, processing hormones, bile production, etc. - Hepatic Portal Vein delivers nutrients to the liver - The hepatic Vein brings deoxygenated blood to the heart - The liver wraps around the IVC - **Gallbladder** - Function: Stores and concentrates bile; emulsifies fats. - **Pancreas** - **Location:** Posterior to stomach. - **Functions:** Hormone production (e.g., glucagon, insulin) and enzyme secretion for digestion (e.g., amylase, lipase). - The pancreas is exocrine and endocrine - **Biliary Tree** - Flow: Liver →R/L Hepatic ducts → Common hepatic duct → Cystic duct → Common bile duct → Small intestine. 11. **Neural Innervation of the Gut** - **Enteric nervous system**-\"brain of the gut\" network of nerve cells in the digestive system that controls digestion. - Controls secretions, blood flow, hormone release, and motility (GI muscle contraction). - **Autonomic Nervous System** - **Parasympathetic "Rest and Digest"** - **Sympathetic "Fight or Flight"** - **Submucosal plexus**-regulating water and ion reabsorption, blood flow and secretion, and innervating secretory cells - **Myenteric plexus**-network of neurons and ganglia that runs from the esophagus to the rectum. Controls Motility 12. **Deglutition** - **Stage 1: Oral (Voluntary) Phase** - Voluntary control - Mastication - Bolus Formation - **Stage 2: Pharyngeal Phase** - Involuntary control - Soft palate and tongue block nasopharynx - Epiglottis covers larynx to suspend respiration. - **Stage 3: Esophageal Phase** - Involuntary control - Peristalsis drives bolus towards stomach - Enters stomach through cardiac sphincter 13. **Gastric Glands and Cell Types in the Stomach** - **Mucous Cells** - **Location:** Found mainly in the cardia and pyloric regions of the stomach. - **Primary Secretion**: Mucus. - **Function:** - Protects the stomach lining from being degraded by stomach acid. - Provides a protective barrier to prevent damage to the epithelial cells. - **Parietal Cells** - **Location:** Found predominantly in the gastric glands of the stomach. - **Characteristics:** Contain a complex network of canaliculi (tiny channels). - **Secretions:** - **Hydrochloric Acid (HCl):** - Aids in the denaturation (unfolding) of proteins. - Activates pepsinogen to pepsin for protein digestion. - **Intrinsic Factor:** - Essential for the absorption of vitamin B12 in the small intestine. - **Ghrelin:** - A hormone that stimulates appetite. - **Chief Cells** - **Location:** Most numerous gastric glandular cells. - **Secretions:** - **Gastric Lipase:** - Aids in the digestion of lipids (fats). - **Pepsinogen:** - An inactive precursor to pepsin, which is crucial for protein digestion. - **G Cells** - **Type:** A specific type of enteroendocrine cell. - **Secretions:** - **Gastrin:** - Stimulates the secretion of hydrochloric acid and digestive enzymes. - Enhances intestinal motility. - Relaxes the ileocecal valve (the valve between the ileum and the cecum of the large intestine). 14. **Bile Production, Transport, and Function** - **Role of Bile** - **Function:** Bile acts as an emulsifier that helps mix fats with water, aiding in the digestion and absorption of dietary fats. - **Bile Production and Transport Pathway** - **Bile Production:** - **Location:** Produced by liver cells (hepatocytes). - **Drainage and Transport:** - **Liver**: Bile is secreted into the right and left hepatic ducts. - **Hepatic Ducts**: The right and left hepatic ducts merge to form the common hepatic duct. - **Common Hepatic Duct:** This duct carries bile towards the cystic duct. - **Storage:** - **Cystic Duct:** Bile flows from the common hepatic duct into the cystic duct. - **Gallbladder**: Bile is stored and concentrated here until needed. - **Release and Delivery to the Duodenum:** - **Gallbladder:** When needed (e.g., after eating), bile is released from the gallbladder. - **Pathway:** Bile flows from the gallbladder through the cystic duct into the common bile duct. - **Common Bile Duct:** Bile travels down this duct and enters the duodenum (the first part of the small intestine) via the ampulla of Vater. - **Emulsification:** Bile salts in bile break down large fat droplets into smaller droplets, increasing the surface area for digestive enzymes to act on. - **Bile and Pancreatic Ducts:** - Bile does not enter the pancreatic duct. - The common bile duct and the pancreatic duct merge before entering the duodenum at the ampulla of Vater. **Week 2 Study Guide: Lower Digestive System** **Overview of Small Intestine** 1. **Parts of the Small Intestine** - **Duodenum** - Begins at the pyloric sphincter. - Receives stomach contents, pancreatic juice, and bile. - Neutralizes stomach acid. - Emulsifies fats with bile. - Pepsin is inactivated - Chemical digestion by pancreatic enzymes. - **Jejunum** - Longer than the duodenum. - Located in the upper left quadrant and umbilical region. - Primary site for digestion and nutrient absorption. - **Ileum** - Final segment, located in the hypogastric region. - Connects to the large intestine at the ileocecal junction. - Absorbs vitamin B12 and bile salts. 2. **Functions of the Small Intestine** - Mixes chyme with digestive juices. - Completes digestion of carbohydrates, proteins, and lipids; initiates and completes digestion of nucleic acids. - Absorbs \~90% of nutrients and water. 3. **Histology and Microanatomy** - **Mucosa:** Simple columnar epithelium for nutrient absorption. - **Submucosa:** Contains lacteals and lymphatic capillaries. - **Muscularis:** - Inner circular smooth muscle layer. - Outer longitudinal muscle layer. - **Serosa:** Continuous with the mesentery (intraperitoneal jejunum and ileum). 4. **Intestinal Modifications** - **Circular Folds:** Increase surface area, slow chyme movement. - **Villi:** Projections with absorptive and goblet cells. - **Microvilli:** Smaller projections with brush border enzymes. 5. **Small Intestine Glands** - **Intestinal Glands:** Secrete intestinal juice; include absorptive, goblet, enteroendocrine (secrete secretin and CCK), and Paneth cells (secrete lysozymes). - **Duodenal (Brunner's) Glands:** Secrete alkaline fluids and mucus. - **Peyer's Patches:** Lymphatic tissues in the ileum for immune support. **Overview of the Large Intestine** 1. **Anatomy and Regions** - **Cecum:** Pouch in the lower right abdomen; connected to the appendix. - **Vermiform Appendix:** Stores beneficial bacteria. - **Colon:** Includes ascending, transverse, descending, and sigmoid colon. - **Rectum:** Leads to the anal canal. 2. **Functions of the Large Intestine** - Continues digestion. - Conducts haustral churning, peristalsis, and mass peristalsis. - Houses intestinal bacteria for nutrient processing. - Compacts waste into feces and facilitates defecation. 3. **Histology and Microanatomy** - **Mucosa:** Simple columnar epithelium with deep crypts and abundant goblet cells. - **Submucosa:** Rich in lymphatic tissue. - **Muscularis:** Thick longitudinal fibers (taenia coli) form haustra. 4. **Anatomy of the Rectum** - **Internal Anal Sphincter**: Smooth muscle, involuntary control. - **External Anal Sphincter:** Skeletal muscle, voluntary control. 5. **Defecation Reflex** - **Intrinsic Reflex:** Mediated by the myenteric plexus, activating peristalsis and relaxing the internal sphincter. - **Parasympathetic Reflex:** Intensifies peristalsis and relaxes the internal sphincter; regulated by spinal reflexes. - **Voluntary Control:** External anal sphincter remains closed due to brain impulses. 6. **Clinical Connection: Fecal Properties** - **Brown:** Normal. - **Green:** Bacterial infection, excess bile. - **Black:** Excess iron, internal hemorrhaging (tar-like). - **Dark Red:** Red foods, bleeding in lower gut. - **Bright Red**: Red foods, hemorrhoids. - **Yellow:** Excessive fat, sinus infection. - **White/Clay:** Anti-diarrheal medications, biliary/liver dysfunction. - **White Spots:** Parasitic infection. **Digestion and Absorption of Macromolecules** 1. **Digestion of Macromolecules in the Oral Cavity** - **Mechanical Breakdown** - **Mastication:** Food is broken down mechanically by chewing. - **Formation of Bolus:** Food is shaped into a bolus for swallowing (deglutition). - **Chemical Breakdown** - **Carbohydrates** - Enzyme: Salivary amylase - Function: Breaks down starch into maltose (disaccharide). - **Lipids** - Enzyme: Lingual lipase (activated by stomach acids). - **Proteins and Nucleic Acids** - No proteolytic enzymes: Proteins are not broken down here. - No nucleases: Nucleic acids are not broken down here. 2. **Digestion of Macromolecules in the Stomach** - **Mechanical Breakdown** - **Gastric Churning:** Extra oblique muscle layer facilitates mixing (mixing waves). - **Formation of Chyme:** Bolus is mixed into a paste-like substance. - **Chemical Breakdown** - **Carbohydrates** - **Duration:** Carbohydrate digestion lasts \~15-20 minutes. - **Effect of Acid**: Salivary amylase is denatured by hydrochloric acid. - **Lipids** - **Enzymes:** Lingual lipase (activated by hydrochloric acid) and gastric lipase (produced by chief cells). - **Proteins** - **Denaturation:** Proteins are denatured by stomach acids. - **Enzyme:** Pepsinogen (converted to pepsin) breaks down proteins into amino acids. - **Nucleic Acids** - **No digestion**: No nucleases in the stomach. 3. **Digestion in the Small Intestine: Brush Border Enzymes** - **Mechanical Digestion** - **Peristalsis and Segmentation**: Move and mix chyme with digestive enzymes. - **Brush Border Enzymes** - **Carbohydrates** - **Sucrase:** Breaks sucrose into fructose and glucose. - **Lactase:** Breaks lactose into glucose. - **Maltase:** Breaks maltose and oligosaccharides into glucose. - **Proteins** - **Dipeptidase and Aminopeptidase**: Break down dipeptides into amino acids. - **Nucleic Acids** - **Phosphatases:** Convert nucleotides into nucleosides and a phosphate group. - **Nucleosidases:** Convert nucleosides into nitrogenous bases and pentoses. 4. **Digestion in the Small Intestine: Pancreatic Juices** - **Addition to Chyme** - **Starches:** Pancreatic amylase breaks down partially-digested starches into oligosaccharides, maltose, and glucose. - **Lipids:** Pancreatic lipase converts triglycerides into monoglycerides and fatty acids. - **Proteins:** - Enzymes: Elastase, trypsin, chymotrypsin, and carboxypeptidase break down proteins into polypeptides and peptide fragments. - **Nucleic Acids:** - **Nucleases:** Deoxyribonuclease (DNAse) and ribonuclease (RNAse) break down DNA and RNA. 5. **Digestion of Lipids** - **Challenges** - **Large Fat Droplets:** Pose problems for enzymatic digestion due to low surface area. - **Hydrophobic Nature:** Lipids are not water-soluble. - **Emulsification** - **Bile Salts**: Amphipathic molecules produced by the liver. - **Micelles:** Formed by bile salts to increase surface area and facilitate digestion by pancreatic lipase. 6. **Digestion of Macromolecules in the Large Intestine** - **Indigenous Microbiota** - **Carbohydrates:** Bacteria break down complex carbohydrates, producing gases (CO₂, methane, hydrogen, H₂S). - **Proteins:** Produce indoles and skatoles (fecal odor). - **Vitamins:** B and K are produced and absorbed. 7. **Absorption of Carbohydrates** - **Mechanisms** - **Glucose**: Transported via sodium-glucose transporters (symporter). - **Fructose:** Transported via facilitated diffusion. - **Solvent Drag:** Additional mechanism due to osmolarity. - **Exit:** Monosaccharides enter the hepatic portal system via facilitated diffusion. 8. **Absorption of Lipids** - **Micelles** - **Function:** Capture fat-soluble vitamins, cholesterol, and fatty acids. - **Conversion:** Fatty acids and monoglycerides are reformed into triglycerides and packaged as chylomicrons. - **Chylomicrons**: Enter lymphatic capillaries, travel through lymphatic vessels, and enter the bloodstream via the thoracic vein. 9. **Absorption of Proteins** - **Mechanisms** - **Amino Acids:** Transported via sodium-dependent cotransporters. - **Dipeptides and Tripeptides**: Hydrolyzed by brush border enzymes before entry. - **Exit:** Amino acids enter the hepatic portal system via facilitated diffusion. 10. **Absorption of Vitamins** - **Fat-Soluble Vitamins:** A, D, E, K absorbed with fats via micelles. - **Water-Soluble Vitamins**: Absorbed by simple diffusion, except B12, which requires intrinsic factor and receptor-mediated endocytosis. 11. **Absorption of Minerals** - **Sodium:** Absorbed with sugars and amino acids via secondary active transport. - **Chloride:** Actively transported in the ileum via antiporter. - **Potassium:** Absorbed by simple diffusion. - **Iron:** Regulated by hepcidin. - **Phosphate:** Active transport. - **Calcium:** Absorbed through channels, regulated by parathyroid hormone. - **Magnesium**: Absorbed via a combination of passive diffusion, solvent drag, and active transport. 12. **Absorption of Bile** - **Reabsorption**: Over 95% of bile salts reabsorbed in the ileum; less than 1 gram excreted in feces. - **Process:** Active transport in ileum and colon, involving sodium ions. 13. **Absorption of Water** - **Daily Water Handling**: Ingestion and secretion of 9.3 liters; about 8.3 liters absorbed in the small intestine, 0.9 liters in the large intestine. - **Excretion:** Approximately 100 mL in feces; the rest processed into urine by kidneys. **Enteric Nervous System and Digestive Regulation** 1. **Enteric Nervous System (ENS)** - **Overview** - Referred to as the \"**brain of the gut\"** due to its complexity and independence from the central nervous system (CNS). - **Receptors:** Located in the mucosal epithelium, detect changes like distension, pH, and chemical presence. - **Plexuses:** - **Submucosal Plexus:** Controls glandular secretions and blood flow in the mucosa. - **Myenteric Plexus:** Regulates gastrointestinal motility by controlling the contractions of the muscularis. - **Function** - **Submucosal Plexus**: Triggers secretion of digestive enzymes and other substances. - **Myenteric Plexus:** Controls contractions of the longitudinal and circular muscles, facilitating motility. 2. **Neural Innervation of the Digestive System** - **Autoregulation:** The digestive system can regulate itself through intrinsic neural mechanisms. - **Sympathetic Innervation:** - **Inhibitory:** Reduces digestive processes, including enzyme and bile secretion, motility, and hormone secretion. - **Sphincters**: Stimulates closure of pyloric and ileocecal sphincters. - **Parasympathetic Innervation:** - **Stimulative:** Enhances digestive processes, including enzyme and bile secretion, motility, hormone secretion, and vasodilation. - **Effect:** Increased blood flow promotes more active smooth muscles and improved absorption. 3. **Digestive Reflexes** - **Short (Myenteric) Reflexes:** - **Activation:** Stretch or chemoreceptors in the digestive tract. - **Response:** Stimulates local contractions of the muscularis layers via the myenteric plexus. - **Long (Vagovagal) Reflexes:** - **Activation:** Sensory autonomic nerve fibers send signals to the brainstem. - **Response:** Vagus nerve and sacral nerve branches modulate motility across the GI tract. 4. **Phases of Gastric Secretion** - **Cephalic Phase:** - **Trigger:** Thought, smell, or sight of food. - Response: Stimulates gastric secretion and motility before food enters the stomach. - **Gastric Phase:** - **Trigger:** Food in the stomach activates stretch and chemoreceptors. - **Response:** Increases gastric secretions via reflexes and release of histamine and gastrin. - **Intestinal Phase:** - **Trigger:** Food entering the small intestine. - **Response:** Releases secretin and cholecystokinin (CCK), inhibits gastric secretion and motility, and stimulates the enterogastric reflex. 5. **Hormones of the Stomach** - **Gastrin:** - **Stimulus:** Stomach distension, pH changes, proteins, caffeine. - **Actions:** Promotes gastric juice secretion, motility, cell proliferation, and regulates sphincters. - **Ghrelin:** - **Stimulus**: Cephalic phase, mealtime. - **Actions:** Stimulates hunger. 6. **Hormones of the Small Intestine** - **Secretin:** - **Stimulus:** Acidic chyme in the small intestine. - **Actions:** Promotes bile and pancreatic juice secretion (rich in bicarbonate), inhibits gastric juice secretion, and enhances CCK. - **Cholecystokinin (CCK):** - **Stimulus:** Amino acids, triglycerides, fatty acids. - **Actions:** Stimulates pancreatic enzyme secretion, bile ejection, and opening of the hepatopancreatic ampulla; induces satiety. - **Gastric Inhibitory Peptide (GIP):** - **Stimulus:** Lipids in the diet. - **Actions**: Induces insulin secretion, supports pancreatic islet cells, inhibits gastric juice secretion. 7. **Hormones of the Large Intestine** - **Motilin:** - **Released:** During fasting. - **Actions:** Enhances contractions of the stomach and intestines to move chyme. - **Neuropeptide Y:** - **Released:** In the presence of fat in the intestinal lumen. - **Actions:** Suppresses exocrine secretions and motility; induces satiety. - **Substance P:** - **Released:** By enteroendocrine cells and neurons. - **Actions:** Promotes bowel motility; associated with pain perception outside the GI tract. 8. **Hormones of the Adipose Tissue** - **Leptin:** - **Stimulus**: Presence of insulin. - **Actions:** Signals the hypothalamus to limit food intake and induces satiety. **Role of the Digestive System in Maintaining Homeostasis** 1. **Integumentary System** - **Function:** The liver plays a role in detoxification and metabolism. Dysfunction (e.g., in liver disease) can lead to jaundice, characterized by yellowing of the skin and eyes, due to the buildup of bilirubin. - **Impact:** Excessive fat deposits in the dermis and hypodermis from liver dysfunction can also alter skin appearance. 2. **Skeletal System** - **Function:** The small intestine absorbs calcium and phosphates essential for bone formation. - **Impact:** Adequate absorption is critical for maintaining bone density and structure. 3. **Muscular System** - **Function**: The liver metabolizes lactic acid produced by muscles during exercise, reducing fatigue. It also stores iron needed for myoglobin synthesis. - **Impact:** Proper metabolism of lactic acid and iron storage supports muscle function and recovery. 4. **Nervous System** - **Function:** Enteric hormones influence appetite and digestion by stimulating brain centers that control hunger and satiety. - **Impact:** Proper hormonal signaling helps regulate food intake and digestive processes. 5. **Endocrine System** - **Function:** The liver hydrolyzes hormones produced by endocrine glands, modulating their effects. - **Impact:** This regulation ensures balanced hormone levels and prevents excessive hormonal activity. 6. **Cardiovascular System** - **Function:** - Absorption of fluids in the intestines contributes to blood volume. - The liver helps stabilize blood glucose levels and produces clotting factors. - Vitamin B12, essential for red blood cell production, is absorbed in the small intestine after binding to intrinsic factor from the stomach. - **Impact:** Proper fluid absorption and liver functions are crucial for maintaining blood volume, glucose levels, and clotting ability. 7. **Lymphatic System** - **Function:** Absorbed fats from the small intestine travel through lymphatic vessels before entering the bloodstream. - **Impact**: Effective fat absorption and transport are vital for overall energy balance and nutrient distribution. 8. **Urinary System** - **Function:** The liver produces urea, which helps maintain osmotic balance and concentrate urine. - **Impact:** Proper urea production is essential for managing waste and maintaining fluid balance. **Common Gastrointestinal Disorders** 1. **Gingivitis** - **Description:** Inflammation of the gums (gingiva) that causes tenderness, bleeding, bad breath, and potential tooth loss. - **Causes:** Poor dental hygiene, smoking, vitamin C deficiency, hormonal changes, genetic predisposition. - **Symptoms**: Tender, inflamed gums, bleeding, halitosis, potential tooth decay. 2. **Periodontitis** - **Description**: Advanced gingivitis leading to inflammation and damage of the periodontal ligaments. - **Causes:** Untreated gingivitis, bacterial growth in periodontal pockets. - **Symptoms:** Loose teeth, pus near the gumline, potential systemic issues like cardiovascular diseases. - **Complications:** Abscesses, tooth loss, increased risk of heart disease and stroke. 3. **Gastroesophageal Reflux Disease (GERD)** - **Description**: Acid reflux caused by stomach acids escaping through the lower esophageal sphincter into the esophagus. - **Causes:** Obesity, spicy/fried foods, pregnancy, smoking, certain medications. - **Symptoms:** Burning chest sensation, regurgitation, difficulty swallowing. - **Treatment:** Lifestyle changes (weight control, dietary modifications), medications (antacids, H-2 blockers, proton pump inhibitors). 4. **Peptic Ulcers** - **Description:** Erosion of the stomach or duodenal lining due to excess acid/pepsin or Helicobacter pylori infection. - **Causes:** Acid overproduction, H. pylori infection, NSAIDs. - **Symptoms:** Abdominal pain, nausea, vomiting, potential bleeding. - **Treatment:** Antacids, acid-reducing medications, antibiotics for H. pylori, bismuth solutions. 5. **Gallstones** - **Description:** Solid particles in the gallbladder or bile ducts, often composed of cholesterol and other substances. - **Causes:** Concentration of cholesterol, bile composition changes. - **Symptoms:** Excruciating pain, jaundice, improper fat digestion. - **Treatment:** Gallbladder removal (cholecystectomy) to prevent recurrence. 6. **Celiac Disease** - **Description:** Autoimmune disorder causing inflammation in the small intestine due to gluten consumption. - **Causes**: Genetic and environmental factors. - **Symptoms:** Diarrhea, bloating, fatigue, anemia, nutrient malabsorption. - **Treatment**: Strict gluten-free diet. 7. **Crohn's Disease** - **Description:** Chronic inflammatory bowel disease with unknown exact cause; possible genetic and environmental factors. - **Symptoms:** Fatigue, blood/mucus in stool, abdominal pain, joint inflammation, diarrhea. - **Complications:** Anal fissures, fistulas, malnutrition, bowel obstruction, colorectal cancer. - **Detection:** Often diagnosed before age 30. 8. **Diverticulitis** - **Description**: Inflammation of diverticula (small pouches in the colon) that can occur with age. - **Causes:** Obesity, smoking, lack of physical activity, high triglyceride intake, certain pain medications. - **Symptoms:** Lower left abdominal pain, nausea, fever, stool changes. - **Treatment:** Liquid diets, antibiotics, or surgery (bowel resection or colostomy). 9. **Colorectal Cancer** - **Description:** Cancer that begins as polyps in the colon or rectum; can metastasize if untreated. - **Symptoms:** Constipation, abdominal pain, blood in stool, weight loss. - **Risk Factors**: Smoking, alcohol use, sedentary lifestyle, obesity. - **Screening:** Sigmoidoscopy (every 5 years from age 50), colonoscopy (every 10 years from age 50).