**Questionnaire Module 7 Digestive System – 2023** --------------------------------- 1. **Draw a diagram of a stomach.** --------------------------------- 2. **Explain the path taken by a flaxseed (or insoluble fiber) from the mouth to the anus.** The path of a flaxseed (or insoluble fiber) through the digestive system involves the following steps: 1. **Mouth**: The flaxseed is chewed, broken down mechanically, and mixed with saliva, which contains enzymes like amylase that begin carbohydrate digestion (though insoluble fiber is unaffected by enzymes). 2. **Esophagus**: The flaxseed is pushed down the esophagus via peristaltic movements into the stomach. 3. **Stomach**: In the stomach, the flaxseed is mixed with gastric juices, including hydrochloric acid and enzymes. While proteins and fats begin breaking down here, insoluble fiber remains largely unchanged and contributes to forming the bulk of the food mixture (chyme). 4. **Small Intestine**: The chyme enters the small intestine, where most nutrient absorption occurs. Enzymes from the pancreas and bile from the liver aid in digesting fats, carbohydrates, and proteins, but the insoluble fiber passes through undigested, adding bulk to the intestinal contents. 5. **Large Intestine (Colon)**: In the colon, insoluble fiber helps regulate water absorption and facilitates stool formation. Some of the fiber may be fermented by gut bacteria, producing gases and short-chain fatty acids, which can have beneficial effects on gut health. 6. **Rectum and Anus**: The remaining fiber, along with waste products and undigested material, is expelled as feces through the rectum and anus. Insoluble fiber like flaxseed primarily serves to aid digestion by adding bulk, promoting regular bowel movements, and supporting healthy gut function without being digested or absorbed. --------------------------------- 3. **The pancreas is an organ with both exocrine and endocrine functions.** - Name the main endocrine hormones that regulate blood glucose levels. *(Average blood glucose levels: 4.7 mmol/L or 0.85 g/L)* - Name the pancreatic enzymes and the substrates they break down. ### Endocrine Function: Hormones Regulating Blood Glucose Levels The pancreas produces two main endocrine hormones that regulate blood glucose levels: 1. **Insulin**: - Secreted by **beta cells** in the islets of Langerhans. - Lowers blood glucose levels by facilitating the uptake of glucose by cells and promoting its storage as glycogen in the liver and muscles. 2. **Glucagon**: - Secreted by **alpha cells** in the islets of Langerhans. - Raises blood glucose levels by stimulating glycogen breakdown (glycogenolysis) and glucose production (gluconeogenesis) in the liver. ### Exocrine Function: Pancreatic Enzymes and Their Substrates The pancreas secretes digestive enzymes into the small intestine to break down macronutrients: 1. **Amylase** - Substrate: **Starches (complex carbohydrates)** - Breaks them down into maltose and simple sugars. 2. **Lipase** - Substrate: **Triglycerides (fats)** - Breaks them down into glycerol and free fatty acids. 3. **Proteases (e.g., Trypsin, Chymotrypsin, Carboxypeptidase)** - Substrate: **Proteins** - Break them down into smaller peptides and eventually into amino acids. 4. **Nucleases (e.g., Deoxyribonuclease, Ribonuclease)** - Substrate: **Nucleic acids (DNA and RNA)** - Break them down into nucleotides. These enzymes and hormones work together to regulate energy metabolism and ensure proper digestion and nutrient absorption. --------------------------------- 4. **Name the 3 anatomical features of the small intestine (SI). What are their purposes?** - Draw a detailed diagram of an intestinal villus. The small intestine (SI) has three key anatomical features that maximize its efficiency in digestion and nutrient absorption: ### 1. **Circular Folds (Plicae Circulares)** - **Structure**: Large, permanent folds in the inner lining of the small intestine. - **Purpose**: Increase the surface area for absorption and slow down the movement of chyme, allowing more time for nutrients to be absorbed. ### 2. **Villi** - **Structure**: Finger-like projections of the mucosal layer lining the small intestine. - **Purpose**: Further increase the surface area for nutrient absorption. Each villus contains a network of capillaries and a lacteal (a lymphatic vessel) for the absorption of nutrients into the blood and lymph. ### 3. **Microvilli** - **Structure**: Tiny, hair-like extensions of the epithelial cells that line the villi, forming the **brush border**. - **Purpose**: Dramatically enhance the absorptive surface area. They also house enzymes (brush-border enzymes) that complete the final stages of digestion, breaking down disaccharides and peptides into absorbable monosaccharides and amino acids. Together, these features increase the surface area of the small intestine by hundreds of times, facilitating efficient digestion and absorption of nutrients. --------------------------------- 5. **Draw a cross-section of the digestive tract, providing detailed labels of the components of the "MS-MS".** --------------------------------- 6. **What is a gallstone (biliary lithiasis)?** - What is the main reason that leads to the formation of a gallstone? *(Etiology)* - Briefly explain the classic symptoms of an acute episode when the gallstone migrates and becomes lodged in the ducts. - Name the complications of an acute episode. ### **What is a gallstone (biliary lithiasis)?** A gallstone is a solid, pebble-like formation that develops in the gallbladder, a small organ beneath the liver that stores bile. Gallstones are composed of cholesterol, bile pigments, or calcium salts, and can vary in size from tiny grains to larger stones. --- ### **Main Reason for Gallstone Formation (Etiology)** The primary causes of gallstone formation include: 1. **Imbalance in Bile Composition**: - Excess cholesterol in bile can crystallize and form stones. - Reduced bile salts or excessive bilirubin can also contribute. 2. **Gallbladder Function**: - Incomplete or infrequent emptying of the gallbladder allows bile to stagnate, promoting stone formation. 3. **Risk Factors**: - Obesity, rapid weight loss, high-fat diets, genetics, pregnancy, and certain medical conditions like liver disease or diabetes. --- ### **Classic Symptoms of an Acute Episode (Biliary Colic)** When a gallstone migrates and becomes lodged in the bile ducts, it can cause an acute episode. Symptoms include: 1. **Severe Pain**: - Sudden, intense pain in the upper right abdomen or center of the abdomen. - Pain may radiate to the right shoulder or back. 2. **Nausea and Vomiting**: - Often accompanies the pain. 3. **Jaundice**: - If the bile duct is completely blocked, bile buildup can lead to yellowing of the skin and eyes. 4. **Fever and Chills**: - May occur if infection (cholangitis) develops. --- ### **Complications of an Acute Episode** 1. **Acute Cholecystitis**: - Inflammation of the gallbladder, often due to prolonged blockage. 2. **Pancreatitis**: - Inflammation of the pancreas if a gallstone blocks the pancreatic duct. 3. **Cholangitis**: - Infection of the bile ducts. 4. **Biliary Obstruction**: - Complete blockage can lead to bile buildup, infection, or liver damage. 5. **Gallbladder Rupture**: - Rare but serious, it can cause peritonitis (infection in the abdominal cavity). Prompt medical intervention is often required to address acute gallstone episodes and prevent complications. --------------------------------- 7. **What is celiac disease?** ### **What is Celiac Disease?** Celiac disease is a chronic autoimmune disorder triggered by the ingestion of gluten, a protein found in wheat, barley, and rye. In individuals with celiac disease, gluten consumption leads to an abnormal immune response that damages the lining of the small intestine, specifically the villi. --- ### **Key Characteristics:** 1. **Immune Reaction**: - When gluten is consumed, the immune system mistakenly attacks the villi in the small intestine. - This damage impairs the intestine's ability to absorb nutrients properly, leading to malnutrition and a range of symptoms. 2. **Triggers**: - Gluten-containing foods (e.g., bread, pasta, cereals). - Even small amounts of gluten can trigger symptoms and intestinal damage. --- ### **Symptoms**: Celiac disease symptoms vary widely and may include: - **Digestive Symptoms**: - Diarrhea, bloating, abdominal pain, gas, nausea, and vomiting. - **Nutritional Deficiencies**: - Iron-deficiency anemia, weight loss, and vitamin/mineral deficiencies. - **Systemic Symptoms**: - Fatigue, joint pain, skin rashes (dermatitis herpetiformis), headaches, and depression. - **Growth Issues**: - In children, it can cause stunted growth, delayed puberty, and irritability. --- ### **Complications** (if untreated): - Osteoporosis or bone weakness due to poor calcium absorption. - Infertility or miscarriages. - Neurological issues, such as peripheral neuropathy or ataxia. - Increased risk of intestinal cancers. --- ### **Diagnosis**: - **Serological Testing**: Detects specific antibodies (e.g., anti-tissue transglutaminase antibodies). - **Intestinal Biopsy**: Confirms villous atrophy in the small intestine. - **Genetic Testing**: Looks for HLA-DQ2 and HLA-DQ8 genes associated with celiac disease. --- ### **Treatment**: - The only effective treatment is a **strict lifelong gluten-free diet**. This allows the intestine to heal and prevents further damage. - Adherence to this diet alleviates symptoms, reduces inflammation, and minimizes complications. end