| Question |
Answer |
| 4 Major Functions of Digestive System | 1. Motility to propel and mix food; 2. Gland secretion to aid in digestion and absorption; 3. Digestion of food into absorable molecules; 4. Nutrient, electrolyte, and H2O absorption into bloodstream. |
| 4 Layers of Digestive Tract | Mucosa, Submucosa, Muscularis, Serosa |
| Mucosa | contains epithelial tissue, lines lumen, produces mucus |
| Submucosa | Beneath mucosa, blood &lymphatic vessels, exocrine glands. |
| Muscularis | Circular muscle & longitudinal muscle |
| Serosa | Visceral peritoneum forming outer layer of tract |
| Enteric Plexus | 2 networks of nerve fibers between submucosa and muscularis layers |
| Mesenteries | hold organs in abdominal cavity together, contain 2 layers of serious membranes. |
| Greater Omentum | Long, double fold of mesentery, creates a pocket where fat accumulates. |
| Saliva | produced at a rate of ~1L/day by parotid and submandibular glands. |
| Salivary Amylase | Enzyme; Breaks down starch into disaccharides; does NOT break down cellulose (source of fiber) |
| Lysozyme | Enzyme; weak antibacterial properties |
| Mucin | lubricating protien found in saliva |
| Salivary secretion regulated mostly by __ | ANS. |
| 3 phases of deglutination (swallowing) | 1. Voluntary Phase 2. Pharyngeal Phase 3. Esophageal phase |
| Voluntary Phase | Bolus is pushed by toungue into oropharynx |
| Pharyngeal Phase | Refles initiated when food is detected by mechanoreceptors in oropharynx. 3 Pharyngeal constictor muscles contract in succession and upper esophageal sphincter relaxes, allowing bolus to be pushed into esophagus |
| Esophageal Phase | Muscular contractions of esophagus, called peristaltic waves, push bolus down into the stomach. |
| Gastroesophageal Reflux Disease | Heartburn; defined by mucosal damage to the esophagus duw do stomach acid reflux.Complications: Chronic esophagitis, difficulty swallowingCauses: Caffeine, stress, alcohol, fatty food, obesity, smoking, and tight clothing. Acid inhibitor treatment |
| Stomach | enlarged segment of digestive tract in left superior part of abdomen; contains additional inner oblique muscle layer |
| Gastric Pits | In stomach; invagination of simple columnar epithelial cells. |
| 4 Cell types of Gastric Pits | Mucus cells(secrete HCO3-, protects stomach from acid), chief cells (secrete pepsin, break down proteins), endocrine cells (secrete gastrin), parietal cells (produce HCL and intrinsic factor, activates Pepsin). |
| Intrinsic Factor | Binds Vitamin B12 making it more readily absorbed by small intesting. B12 is critical for DNA synthesis and RBC production. |
| Both __ and __ mechanisms regulate gastric secretion | neural and hormonal |
| Cephalic stage of Stomach secretion | first stage; anticipatory; taste, smell of food activate parasympathetic NS, stimulating stomach secretions, particulary gastrini which acts on parietal cells for HCL production |
| Gastric Phase of stomach secretion | greatest gastric secretion; reflex initiated by distention of the stomach |
| Intestinal phase of stomach secretion | inhibits gastric secretion, presence of chyme in duodenum initiate neural and hormonal resoponses |
| Neural: | Chemoreceptors in duodenum detect HCl or lipids, sent dignals to medulla to inhibit parasympathetic activity |
| Peptic Ulcer | Results from erosive and digestive actions of H+ and Pepsin. |
| Major causative factor of Peptic Ulcers | Helicobactor pylori infection, secretes cutotoxins, damage mucosal layer, secrete enzyme called urease, which alkinalizes the local enviro. |
| Treatment of Peptic Ulcers | Antibiotics, Proton pump Inhibitors (Block H+ secretion) |
| Mixing waves | Weak contractions; mix food w. stomach secretions to form chume; push more fluid part toward pyloric sphincter & olid part back toward body |
| Peristaltic Waves | Stronger contractions; force food toward and through pyloric sph. little bit at a time. |
| Why must chyme be emptied slowly? | so it can be neutralized by HCO3- |
| CCK | Decreases stomach secretions, also acts to slow gastric peristaltic waves |
| small intestine | ~6M long, duodenum, jejunum, ileum. Major site of digestion and absorption. |
| Circular folds | Run perpendicular to length of small intestine (Increase SA) |
| Villi | projections of mucosal layer (^SA) |
| Microvilli | cell membrane extensions of individual mucosal eptihelial cells |
| Mucosa of SI 4 Cell types | Absorptive cells ( have microvilli, produce enzymes & absorb food), Goblet Cells, Granular Cells (protect from bacteria), Endocrine Cells(Produce hormones which stimulate liver and pancreatic secretions) |
| Digestive Enzymes in Brush Border | Peptidases, Disaccharidases |
| Lactose Intolerance | Deficiency in disaccharidase, lactase, Can cause asmotic diarhhea. |
| Segmental contractions | propagated for only short distances and mix intestinal contents |
| Hepatocytes | Liver cells; process nutrients and detoxify harmful substances from blood |
| Liver is responsible for | Nutrient storage/release, Nutrient Conversion, Sunthesis of important blood proteins such as albumin, fibrinogen and glouline |
| Blood supply into and out of liver | Hepatic artery delivers O2 rich blood, Hepatic Portal Vein delivers 02 poor blood containing nutrients absorbed from SI, Hepatic Veins empty into inferior vena cava. |
| Liver is divided into | lobules by connective tissue septa, have portal triads at corners |
| Triads | Consist of hepatic portal veins, hepatic arteries, and hepatic ducts. |
| Bile | produced by liver, secreted into duodenum, contains amphipathic ile salts, which emulsify fats in the duodenum |
| Bile secreted by | CCk |
| CCK Response | released by endocrine cells in response to chyme from stomach. cck travels to gallbladder where it causes contraction. |
| Cirrhosis | refers to damage and death of hepatocytes and replacement by connective scar tissue. Treatment seeks to slow progression |
| Pancreas | posterior to stomach in left upper quatrant of abdomen. Composed of exocrine and endocrine tissues |
| endocrine tissue | composed of acinar glands |
| pancreatic juice | rich in HCO3- which neutralize acidic chyme. contain pancreatic proteases, such as trypsin, pancreatic amylase which breaks down starchinto disaccharides and pancreatic lipase which breaks down lipids into glycerol and fatty acids |
| pancreatic juice secretions | in response to neural and hormonal activity |
| Large Intestine | cecum colon rectum anal canal. |
| cecum | proximal end of LI, SI AND LI meet at ilocecal junction. |
| colon | longest part of LI consisting of ascendind, transverse, descending and sigmoid segments, mucosal lining contains crypts which contain goblet cells |
| colon functions | converts chyme into feces, absorbs water& salts, mucus secretion & activity of bacteria. |
| mass movements | propel feces long distances through the colon, occur every 8-12 hours |
| defecation reflex | distention of rectal wall, parasympathetic response causes strong peristaltic contractions and relaxation of internal anal sphincter |
| Irritable bowel syndrom | abdominal pain, twice as common in adult females, highly correlated with stress or depression. treated by stress management, increased fiber, or anxiety drugs. |
| Types of digestion | Mechanical: breaking food into smaller particles. Chemical: breaking of covalent bonds in nutrients by digestive enzymes |
| Carbohydrate digestion | begins in oral cavity. |
| Carbohydrate absorption | Absorbed as monosaccharides. Apical membrane transport; glucose and galactose cotransported with NA; secondary active transport driven by NA, K, ATPase on basal membreane. enter capillaries of intestinal villi and are transported to liver via hepaticportv |
| Protein digestion | Proteases digest protein and polypeptides into smaller polypeptides. Brush border peptidases break down small polypeptides into absorbable forms, Tripeptides, Dipeptides and amino acids. |
| Protein absorption | amino acids, dipeptides or tripeptides. apical membrane transport. amino acids cotransported with NA secondary driven by Na, K, ATPase on basal membrane. |
| Major Ingested Lipids | Triglycerides ( can be saturated or unsaturated), phospholipids ( recall major constituent of cell membrane), steroids (cholesterol and hormones), fat-soluble vitamins such as vitamin E |
| Lipid Digestion | Emulsification: Amphipathic bile salts break large lipid droplets into much smaller droplets |
| Absorption of Lipids | Occurs when micelles containing products of lipid digestion feely diffuse across apical surface of intestinal cells |
| Lipid Digestion | Emulsification: Amphipathic bile salts break large lipid droplets into much smaller droplets |
| Absorption of Lipids | Occurs when micelles containing products of lipid digestion feely diffuse across apical surface of intestinal cells |
| Lipoproteins transport | Triglycerides and Cholesterol. |
| LDL | Low Density Lipoproteins;; transport cholesterol from liver to tissues for use by clls. High cholesterol content and low protein content. |
| HDL | High Density Lipoproteins transport cholesterol from tissues to liver where its metabolized or excreted in bile. |
| about __L of H20 enters GItract daily | 9 |
| 92% of water absorbed by | SI |
| 7% of water absorbed by | LI |
| 1% of water | lost in feces |
| water moving across GI Tract | Passive, direction determined by osmotic gradient |
| Electroltes such as NA, K, Ca are __ across intestinal epithelium | actively transported |
| Ca2 absorption requires | Vitamin D. Acts on intestinal epithelial cells to increase synthesis of a Ca binding portien called Calbindin. |
| Diarrhea | Major cause of Death worldwide. responsible for 18% of childhood deaths. Loss of fluid >> loss of extracellular fluid>> low blood volume >> low BP > death. |
| secretory diarhhea | Vibrio cholerae. cholera toxin released, causes crypt cells to secrete large amounts of fluid>> can be fatal within hours. Easily treated by replacing fluid and electrolytes. |
| Nutrients | Ingested chemicals. |
| Major classes of nutrients | carbohydrates, lipids, proteins, vitamins, minerals, water |
| Essential nutrients | ex: linoleic acid must be ingested. important for blood clotting. Nonessenial are necessary but can be synthesized from esential nutrients. |
| Benefits of a healthy diet | reduction in heart and chronic diseases |
| Caloric restriction | Restrict calories by 10-25%. decrease in heart disease, diabetes, and cancer shown (in rats) monkeys less likely to develop Alzheimer's. Increased insulin sensitivity and reduced LDL cholesterol. Humans: lower BP and cholesterol, possibly lifespan. |
| Glucose | Principal energy source for cells. Glycolysis yeilds ATP. help build DNA and RNA. |
| When Glycogen stores are full... | The liver converts excess glucose to riglycerides which are exported to adipose tissue for long term storage. |
| Insulin | Released from Beta cells of pancreas in response to a raise in blood sugar; promotes uptake and storage of glucose as well as fats and proteins. |
| Insulin uptake & storage | Binds to receptor>intracellular phosphorylation of proteins> insertion of GLUTs in cell membrane > increased glucose Uptake |
| Glucagon | hormone of starvation. During periods of fasting, raises glucose levels. triggered by low blood glucose levels. |
| Glucagon release | Breakdown of glycogen> glucose in lover, break down of fats in adipose tissue and breake down of amino acids from muscle; all enter bloodstream. |
| Gluconeogenesis | Liver can synthesize glucose from other nutrient sources such as amino acids and glycerol in triglycerides |
| Insulin dependent diabetes mellitus | cause by distruction of beta cells in pancreas so body produces no insulin |
| Characterization of Type 1 diabetes | hyperglycemia, osmotoic diuresis, bypotension treated by administration of synthetic insulin |
| non insulin dependent diabetes mellitus (type 2) | caused by increased resistance of target tissues to insulin. assoc. w. obesity. Caloric and cab restriction and drugs |
| Carb. restriction | Atkins;; Utilization of glycogen stores, gluconeogenisis keeps these people alive |
| glycemic index | predicts whether absorbed carbs are used for immediate energy needs or sent to long term storage: Low value indicates slower digestion higher = quicker |
| factors which affect glycemic indes | type of starch, physical entrapment of starch, presence of fat and protein, organic acids such as vinegar |
| high glycemic index foods | promotes storage as fat; reduces insulin sensitivity |
| nutrient timing | popular in athletic training; involves significant carb intake during periods before or after intense physical activity. outside of that small window, carb intake is restricted |
| Fatty acids are classified by.. | degree of saturation |
| saturated | carbon chain has all single bonds. each c atom in chain is saturated with hydrogen atoms |
| unsaturated | carbon chain has one or more double bonds. |
| Monounsaturated | unsaturate; one double bond |
| polyunsaturated | unsaturated; more than 1 double bond |
| sources of each fatty acid. | Sat: meat, dary, eggs, nutsMono:olive, canola, certain nuts/seedsPolyunsat: fish, safflower, certain nuts/seeds |
| Homeostasis | maintenence of a relatively stably environment with respect to a given variable |
| which substances can freely diffuse across CM? | Lipids and other hydrophobic molecules (CO2 and 02 both can) an exception: water CAN freely diffuse |
| osmosis | diffusion of water across a membrane from high to low concentration |
| diffusion | movement of molecules across a membrane from high to low concentration |
| how are substances movs across CM against concentration gradient? classic example? | active transport: proteins. |
| How is the body able to produce different cell types? | Gene Regulation controls which cells get made my regulating which cells get copied, or transcribed |
| Action Potential (1) | a Ligand binds to a ligand gated Na+ channel, releasing a bunch of Na+. This floods the cell because of how much more Na is on the outside. This strongly depolarizes the cell. This reaches the threshold potential needed to open the voltage gated Na |
| AP(2) | Channels, releasing more Na, making the membrane go up to +40mV. Finally, the slower-opening K+ channels open, causing K+ to rush out of the cell, repolarizing it. |
| Steps of Neurotransmission | current is detected by voltage gated Ca2+ channels, which open allowing Ca2+ to move down its conc. gradient. Ions flow into vessicle and associate with vessicles containing neurotransmitters. vessicles fuse with CM, releasing 10000s of neurotransmitter |
| Neurotrans (2) | molecules into extracellular space. difuse across synapse and bind specific receptors. leads to channel opening and depolarization of postsynaptic membrane. |
| how is touch sensation detected and transmited to somatosensory cortex | Skin > spinal cord > thalamus > somatosensory cortex |
| how brain initiates skeletal muscle movement | planning in premotor area, primary motor cortex initiates signals which result in movement; lower motor neurons project to skeletal muscle fibers; |
| how brain initiates skeletal muscle movement | planning in premotor area, primary motor cortex initiates signals which result in movement; lower motor neurons project to skeletal muscle fibers; |
| 2 divisions of ANS and functions neurotransmitters released from each | Sympathetic: fight of flight norepiParasympathetic: resorative or vegetative body functions ach |
| 2 divisions of ANS and functions neurotransmitters released from each | Sympathetic: fight of flight norepiParasympathetic: resorative or vegetative body functions ach |
| motor unit | all muscle fibers a single lower motor neuron innervates. |
| motor unit | all muscle fibers a single lower motor neuron innervates. |
| motor unit | all muscle fibers a single lower motor neuron innervates. |
| intercellular events occuring during muscle contraction and relaxation | release of Ca2+ cells, opens voltage gated Ca channels, in SR, Ca is released into sarcoplasm, allows myosin to bind to actin, myosin binds and unbinds, pulling a little each time and burning one ATP each time. called cross bridge cycling. Ca is pumpedbac |
| intercellular events occuring during muscle contraction and relaxation | release of Ca2+ cells, opens voltage gated Ca channels, in SR, Ca is released into sarcoplasm, allows myosin to bind to actin, myosin binds and unbinds, pulling a little each time and burning one ATP each time. called cross bridge cycling. Ca is pumpedbac |
| electrical conduction through heart | release of Ca2+ cells, opens voltage gated Ca channels, in SR, Ca is released into sarcoplasm, allows myosin to bind to actin, myosin binds and unbinds, pulling a little each time and burning one ATP each time. called cross bridge cycling. Ca is pumpedbac |
| electrical conduction through heart | initiated in SAnode, right A wall, Left A wall, AV node, AV bundle, Ventricles, Purkinje fibers |
| electrical conduction through heart | initiated in SAnode, right A wall, Left A wall, AV node, AV bundle, Ventricles, Purkinje fibers |
| Elec activity coordinates atria- ventricle contraction | Slow conduction through AV node |
| Elec activity coordinates atria- ventricle contraction | Slow conduction through AV node |
| baroreceptor reflex alters heart function | drop in atrial pressure, less barometric stretch, info sent to cv center; sympathetic response., efferent fibers project to sa node and vent. muscle, release norepi, sa increases HR, ventricles contract more forcefully raising bp, raises arterial pressure |
| RAAS respons to increase BP | angiotensin causes vasoconstriction, aldosterone increases NA reabsorption causing higher blood volume & thus pressure |
| breathing | diaphragm contraction causes increase in thorassic pressure, ^ pleural cavity volume, V pleural pressure, expansion of lungs, lowered pressure drives air in. Expiration is natural, lungs have recoil naturally |
| how 02 and c02 are exchanged in pulmonary and systemic capillaries | partial pressures drive the gasses between alveoli and pulmonary capillaries. hemoglobin in systemic capillaries. |
| how do kidneys handle Na & main site of reabsorption & how handling relates to blood volume | kidneys can alter serum levels of sodium salts; proximal tubule, more Na, higher BP |
| Hormone which determines wheter urine is dilute or concentrated by altering water permeability of distal renal tubule | ADH |
| good fats | Poly and mono unsaturated: Decresase LDL and increase HDL |
| bad fats | Saturated fats raise LDL and HDL. Really bad fats are transfats, Raise LDL and lower HDL. |
| 1g TG yeilds | as much caloric energy as 2gs FA. |
| ketosis | excess ketones in blood |
| vitamins | organic molecules that exist in minute quantities in food that are essential to a normal metabolism |
| minerals | inorganic nutrients that are essential for normal metabolic function |
| role of Mineral, Calcium | builds n maintains bones and teeth; neurotransmission, heart rhythm, muscle contraction, blood clotting. |
| osteoperosis | results from deficiency in dietary calcium; causes bones to be porous and fragile. prevention includes excercise, vit D, sun exposure |
| Vit D | facilitates absorption of dietary calcium in intestinal epithelium. |
| healthy bones | not calcium but vitamin d |
| folate, Vitamin B9 | plays an important part in nucleic synthesis and replacement. important for RBC synthesis. deficiency can cause spina bifida in unborn babies; |
| folate, VB6 VB12 | may reduce risk of CVD and/or stroke by reducing homocysteine which causes CVD and Stroke. |
| Folate lowers risk of | colon and breast cancer; unless preexisting, when it may make them worse! |
| alcohol consumption | decreases absorption of folate in the blood |
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