block 6- the gastrointestinal system Flashcards

Question

describe the pancreatic enzymes

Answer 1

pancreatic amylase - digests starch pancreatic lipase - digests fat ribonucleoase - digests RNA deoxyribonclease - digests DNA -amylase, lipase and nucleases are secreted in active form but require ions or bile for optimal activity - proteases secreted in inactive form and activated by the duodenum - trypsinogen is activated to trypsin by brush border enzyme enteropeptidase - procarboxypepidase and chymotrypsinogen are activated by trypsin

Answer 2

- Insulin, glucagon (regulate glucose homeostasis). - the other 2% - a cells secrete glucagon in response to a fall in blood glucose - this stimulates glycogenolysis and gluconeogenesis - b cells secrete insulin in response to a rise in blood glucose - this is inhibited by adrenaline in acute stress - allows cells to utilise glucose - 8 cells secrete somatostatin which is stimulated by cholinergic innervation - inhibits gastrin release

Answer 3

Bile: -Produced by hepatocytes (liver cells) and stored in the gallbladder. -Composition: Bile salts, bilirubin, cholesterol, phospholipids, electrolytes. -bile is secreted into bile canaliculi then bile ductules then the bile ducts Functions: -Aids in lipid digestion (emulsifies fats). -Neutralizes stomach acid providing optimum pH for enzymes -Excretes waste products (e.g., bilirubin). -Bile Release: Triggered by food intake, stored bile is released into the small intestine.

Answer 4

- is a thin walled, pear shaped muscular sac on the ventral surface of the liver - stores and concentrates bile by absorbing its water and ions - releases ble via the cystic duct, which flows into the bile duct

Answer 5

Mucus: Protects the intestinal lining and lubricates food for smoother passage. Watery Secretions: Aid digestion and absorption.

Answer 6

1. Cephalic Phase (Preparation) -Triggered by sight, smell, taste, or thought of food. -CNS Activation: Signals salivary and gastric glands to prepare for food. -Facial, glossopharyngeal and vagus nerves are activated (cranial) 2. Gastric Phase (Food in the Stomach) -Stimulation: Distension of the stomach and increased pH activate stretch receptors and chemoreceptors. -Response: Peristalsis and gastric juice secretion to break down food. -Negative Feedback: When food moves to the duodenum, it decreases gastric secretion. 3. Intestinal Phase (Food in the Small Intestine) -Inhibition: Prevents more food from entering the stomach and slows gastric motility. -Hormones Involved: Cholecystokinin (CCK): Inhibits gastric secretions and motility. Secretin: Stimulates pancreatic secretions and inhibits gastric acid. Enterogastric Reflex: Neural feedback that slows gastric emptying.

Answer 7

Ingestion: Taking in food. Digestion: Breakdown of food into absorbable nutrients. Absorption: Nutrients are absorbed through the intestinal lining into the bloodstream. Excretion: Undigested materials and waste are eliminated from the body.

Answer 8

primary = Active transport directly uses energy (usually ATP) to move molecules against their concentration gradient through a carrier protein. secondary = Does not directly use ATP but relies on the electrochemical gradient created by primary active transport. It uses the energy stored in the gradient of one molecule (e.g., sodium) to move another molecule against its concentration gradient. (a co-transporter)

Answer 9

Types of Carbohydrates: 1. Polysaccharides: Long chains of monosaccharides that can be digestible or non digestible (e.g., starch made of glucose). Found in rice, pasta 2. Sugars: Shorter chains, such as monosaccharides and disaccharides. Found in fruits, vegetables, dairy, etc. Enzymes Involved in Digestion: Lactase: Breaks down lactose into glucose and galactose. Amylase: Breaks down starch into smaller sugars. Absorption: Fructose: Absorbed via facilitated diffusion. Glucose & Galactose: Absorbed via secondary active transport using the sodium gradient. Energy is required for absorption. These monosaccharides are absorbed at the brush border to avoid bacterial use of nutrients in the small intestine.

Answer 10

mouth -> salivary amylase: breaks down starch to maltose pancreas -> pancreatic amylase: breaks down starch to maltose small intestine microvilli -> specific oligosaccharides: produce monosaccharides

Answer 11

Galactose and glucose

Answer 12

Digestion: Broken down into smaller peptides and amino acids by enzymes (e.g., pepsin, trypsin). Absorption: Small Peptides (up to 3 amino acids): Absorbed via secondary active transport. Amino Acids: Absorbed via facilitated diffusion or secondary active transport.

Answer 13

stomach -> pepsin: produces smaller polypeptide chains pancreas -> trypsin, chymotrypsin, carboxypeptidase: produce smaller peptide chains small intestine microvilli -> specific peptidases: produces tripeptides, dipeptides and amino acids

Answer 14

types of Lipids: Triglycerides, phospholipids, cholesterol, fat-soluble vitamins. Digestion: Lipase: Breaks triglycerides into monoglycerides and fatty acids. Emulsification: Lipid droplets are broken down into smaller droplets by bile salts and stomach churning to increase surface area. Absorption: Fatty acids and monoglycerides are absorbed into enterocytes and recombined into triglycerides. Chylomicrons are formed (contain triglycerides, cholesterol, phospholipids, and proteins). Chylomicrons enter lymphatic vessels (lacteals) as they are too large to enter blood vessels.

Answer 15

too large to enter blood as cannot pass through capillary wall - Lymphatic capillaries lack basement membrane and are more permeable to large particles

Answer 16

Fat-Soluble Vitamins (A, D, E, K): Absorbed with lipids via micelles. Water-Soluble Vitamins (C, B, B12): Absorbed by passive or active transport. Vitamin B12: Requires intrinsic factor for absorption via endocytosis. In the Large Intestine: Vitamin K and B vitamins from bacterial metabolism are absorbed. - vitamins are organic substances that cannot be manufactured by the body

Answer 17

=vitamin E is fat soluble so must be carried via a micelle Bile duct delivers bile to SI to allow micelle generation

Answer 18

Electrolyte Absorption: Iron: Absorbed by divalent metal-ion transporter 1. Calcium: Absorption regulated by vitamin D and parathyroid hormone. Sodium (Na+): Absorbed with glucose and amino acids. Potassium (K+): Absorbed via passive diffusion in response to osmotic gradients. - occurs mostly along the length of the small intestine - usually by active transport

Answer 19

-Around 9L of fluid is absorbed daily. 95% of water is absorbed in the small intestine by osmosis. -Water absorption is coupled with solute absorption to maintain osmotic gradients.

Answer 20

= any condition that prevents us absorbing nutrients into the body causes: - interference of delievry of bile or pancreatic juice - damaged intestinal mucosa - Gluten-sensitive enteropathy- condition affecting intestines (celiac disease) - Gluten damages the intestinal villi and brush border – Treated by eliminating gluten from the diet

Answer 21

mouth -> lingual lipase: digests <10% of lipid stomach -> gastric lipase: small amount pancreas -> pancreatic lipase: majority of lipids

Answer 22

1. large fat globules are emulsified(physically broken up into smaller fat droplets) by bile salts in the duodenum 2. digestion of fat by the pancreatic enzyme lipase yields free fatty acids and monoglycerides. these then associate with bile salts to form micelles. 3. fatty acids and monoglycerides leave micelles and diffuse into epithelial cells where they are recombined and packaged with other lipoid substances and proteins to form chylomicrons 4. chylomicrons are extruded from the epithelial cells by exocytosis. the chylomicrons then enter lacteals. they are carried away from the intestine by lymph.

Answer 23

Simple Diffusion: Movement of non-polar, small molecules (e.g., oxygen) across the membrane. Facilitated Diffusion: Movement of larger or charged molecules (e.g., glucose, sodium) through specific transport proteins. Active Transport: Primary Active Transport: Direct energy use via a carrier protein (e.g., sodium-potassium pump). Secondary Active Transport: Uses the concentration gradient of one substance (e.g., sodium) to transport another (e.g., glucose).

Answer 24

-Largest internal organ (~1.5 kg), in the upper right quadrant of the abdomen. -Protected by the rib cage, located under the diaphragm. lobes: -Right (larger) & Left (smaller), separated by falciform ligament. -Quadrate (top) & Caudate (bottom) lobes (part of the right lobe).

Answer 25

-Hepatic artery (oxygen-rich blood) from the celiac trunk of aorta. - smaller -Hepatic portal vein (nutrient-rich, deoxygenated blood) from the GI tract. - main supply

Answer 26

- Once blood has passed through the liver it is drained into the inferior vena cava by 3 hepatic veins - Left hepatic vein supplies left lobe - Right hepatic vein to right lobe - Middle hepatic vein to central region

Answer 27

- the portal hepatis is the main site where structures enter and leave the liver including portal triad, nerves and lymphatics portal triad consists of: - hepatic artery and vein which bring nutrients to the liver - the bile duct which leaves the liver

Answer 28

- a portal system connects one organ to another without returning to the heart first - Blood draining from GI tract, pancreas and spleen is carried to the liver first -

Answer 29

hepatocytes (80% of liver cells) – perform metabolic & detox functions. Hexagonal lobules: Each has a central vein & portal triad (at each corner). Sinusoids (specialized capillaries): -Fenestrated endothelium allows nutrient/metabolite exchange. -Contain Kupffer cells (macrophages that break down RBCs). -Bile Canaliculi: Tiny ducts collecting bile from hepatocytes.

Answer 30

=sit within plasma within the space of disse -inactive in healthy individuals if liver is damaged cell is activated, involved in collagen production and storage of vitamin A

Answer 31

- made up of different hepatocytes all going towards the central vein - The hepatocytes and vessels of the liver are arranged in hexagons with branches of the portal triad at each corner and a central vein

Answer 32

is a space between a hepatocyte, and a sinusoid in the liver. It contains the blood plasma.

Answer 33

- blood from the hepatic artery and portal vein enter these specialised capillaries - they are large, low pressure vessels - drain the blood it receives into the central vein

Answer 34

1. Metabolism Carbohydrates: Glycogen storage & breakdown (glucagon vs insulin). Lipids: Lipoprotein synthesis (for fat transport). Proteins: Deamination of amino acids → urea cycle (removes toxic ammonia). 2. Detoxification 3. Excretion Bilirubin excretion (by-product of RBC breakdown). 4. Storage Glycogen (carbs), triglycerides (fats), vitamins (A, D, B12), minerals (iron, copper). 5. Synthesis Bile salts (for fat digestion). Plasma proteins (albumin, clotting factors). Cholesterol, angiotensinogen (blood pressure regulation). 6. Phagocytosis Kupffer cells remove old RBCs & pathogens. 7. Heat Production High metabolic activity → generates body heat.

Answer 35

Phase I (Modification): drug is turned into a metabolite by the addition of reactive and polar groups, this prevents free diffusion across the membranes Phase II (Conjugation): Makes molecules water-soluble for excretion through the attatchment of an ionised group Phase III (Excretion): Eliminates via urine (smaller metabolites by kidneys) or bile (larger metabolites by faeces).

Answer 36

- Primarily performed by cytochrome P450 enzymes located in smooth endoplasmic reticulum of hepatocytes Enzymatic incorporation of polar groups (O or OH): * Oxidation * Reduction * Hydrolysis

Answer 37

Addition of an ionised group: * Glutathione * Sulphate * Glycine * Glucuronic acid - occurs in cytoplasm of hepatocytes - makes metabolite water soluble for trasnport and inactivates it

Answer 38

- formed from red blood cells breakdown - broken down by macrophages -is bound to albumin in plasma for transport - excess billirubin causes jaundice - free billirubin cab be potentially toxic if it crosses the blood brain barrier - Bilirubin conjugated to glucuronic acid to form bilirubin glucuronide. - The conjugated bilirubin is more soluble and can be excreted by the hepatocyte into the biliary canaliculi

Answer 39

Bilirubin breakdown: RBCs → Heme → Bilirubin (toxic, must be processed). Transported to liver bound to albumin, conjugated for excretion in bile. Neonatal Jaundice: Immature liver lacks enzyme for bilirubin conjugation. Phototherapy converts bilirubin to a water-soluble form for excretion.

Answer 40

-Hepatocytes divide to maintain function. -Severe damage activates liver stem cells. -Cirrhosis impairs regeneration ability

Answer 41

= Maintains blood glucose homeostasis by storing or releasing glucose. - High blood glucose: Insulin stimulates glycogenesis (glucose → glycogen for storage). - Low blood glucose: Glucagon stimulates glycogenolysis (glycogen → glucose for energy). - If glycogen stores are depleted, gluconeogenesis occurs (new glucose formed from non-carbs like amino acids). - maintaining glucose levels is vital as too high levels could lead to impaired nervous system dysfunctiona and too low could lead to complications with diabetes

Answer 42

- uptake of glucose via GLUT2 receptors in respose to high glucose levels -insulin is released from the pancreas - glucose -> glucose-6-phosphate via glucokinase liver converts G6P -> glycogen via glycogen synthase (glycogenesis) - increased triglyceride synthesis

Answer 43

- glucagon is released from the pancreas liver converts glycogen -> glucose-1-phosphate via glycogen phosphorylase (gluconeogenesis) - synthesis of glucose from amino acids and triglycerides - is a 11 enzyme catalysed reaction - requires ATP and GTP

Answer 44

-Synthesizes lipoproteins (for fat transport in the blood). -Stores triglycerides (fat storage). -Beta-oxidation: Breaks down fatty acids to generate ATP. -Cholesterol synthesis: Produces cholesterol, some used for bile salt production.

Answer 45

-Deamination: Removes amino groups from amino acids → produces ammonia (toxic). -Urea cycle: Converts toxic ammonia into urea, excreted in urine. -Synthesizes plasma proteins (albumin, clotting factors). - synthesises all non-essential amino acids

Answer 46

main role = homeostasis others: - Waste Disposal – Removes metabolic waste. Osmoregulation – Maintains fluid and ion balance. Blood Volume & Pressure Regulation – Adjusts blood volume by controlling water excretion. Blood pH Regulation – Controls H+ and HCO3- levels. Hormone Production – Produces hormones like erythropoietin and renin.

Answer 47

Kidneys – Filter blood, produce urine. Located retroperitoneally (behind peritoneal cavity) at the level of the 12th rib. Left kidney higher than right. Receives 20-25% of cardiac output (~1200ml/min) via renal arteries from the aorta. - blood returned to inferior vena cava via renal veins -Ureters – Transport urine from kidneys to bladder. -Bladder – Stores 700-1000ml of urine. -Urination involves urethral sphincter relaxation & detrusor muscle contraction. -Urethra – Allows urine to exit the body.

Answer 48

Fibrous Capsule – Protective, non-flexible outer layer. Cortex – Outer dark brown region. Medulla – Inner lighter region where urine is formed. Urine Flow: Urine flows from medullary region → minor calyx → major calyx → collecting tubules → ureter.

Answer 49

= Is the functional unit of the kidney. Consists of: Renal Corpuscle (in cortex) → Filtration. Renal Tubule (spans cortex & medulla) → Reabsorption & secretion.

Answer 50

- where blood plasma is filtered composed of: 1. Glomerulus (Capillary Bed) – Where filtration occurs. 2. Bowman’s Capsule – Collects filtrate. - space between the two layers is the capsular space, where the filtrates flow through Special Blood Supply: Capillaries are supplied & drained by arterioles (instead of veins). Arterioles can constrict/dilate to regulate filtration pressure. Epithelium Type: Simple squamous (thin for filtration). Filtration Process: Allows: Water, sodium, glucose, chloride. Prevents: RBCs, large proteins.

Answer 51

1. Proximal Convoluted Tubule (PCT) – Reabsorbs glucose, sodium, other solutes. 2. Loop of Henle – Creates osmotic gradient for water/solute exchange (counter-current multiplier). 3. Descending limb – Water permeable, solute impermeable. 4. Ascending limb – Water impermeable, solute permeable. 5. Thick ascending limb – Active transport of sodium/chloride. 6. Distal Convoluted Tubule (DCT) – Water reabsorption, drains into collecting duct. 7. Collecting Duct – Controls final urine concentration (permeability changes based on hydration).

Answer 52

- Glomerular filtration is the first step of urine production * Water and most solutes in blood plasma pass from glomerular capillaries to glomerular capsule – Glomerular filtrate * Filter 180 litres/day * Eliminate 2 litres/day urine * Glomerular capsule drains into renal tubule

Answer 53

1. Antidiuretic Hormone (ADH/Vasopressin) – Water Retention - Increases aquaporin channels → More water reabsorbed → Urine concentrated. - Low ADH → Water diuresis (dilute urine). - Also acts as vasoconstrictor → Increases blood pressure.

Answer 54

- Kidneys release renin → Triggers angiotensin II production. Angiotensin II effects: Vasoconstriction → Raises BP. Stimulates aldosterone → Increases sodium & water retention. - increasing blood pressure

Answer 55

- Released from stretched heart atria. - Acts on kidneys to increase urine output → Lowers blood volume/BP. - lowering blood pressure

Answer 56

1. sympathetic nerves - can decrease sodium and water excretion - increase angiotensin 2 formation 2. parathyroid hormone - increased reabsorption of calcium in DCT

Answer 57

Descending Limb → Permeable to water, impermeable to salt → Water leaves, filtrate becomes concentrated. Ascending Limb → Permeable to salt, impermeable to water → Salt pumped out, filtrate becomes dilute. Creates a salt gradient in the medulla, allowing more water to be reabsorbed from the collecting duct when needed. ADH regulates water reabsorption → More ADH = concentrated urine, Less ADH = dilute urine.

block 6- the gastrointestinal system Flashcards

(81 cards)