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72 Cards in this Set
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- Back
- 3rd side (hint)
Glomerular Filtration Rate (GFR) hpic |
•Influenced by two factors –Net filtration pressure –Hydrostatic pressure –colloid osmotic pressure –fluid pressure –Filtration coefficient –Surface area of glomerular capillaries available for filtration regulated by mesangial cells –Permeability of interface between the capillary and Bowman’s capsule |
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Intrinsic GFR Regulation |
•Myogenic response –Intrinsic ability of vascular smooth muscle to respond to pressure changes –Similar to autoregulation in other systemic arterioles •Tubuloglomerular feedback –Paracrine control from the macula densa –Too much flow (NaCl) at macula densa means GFR is too high –Response is to constrict the AA |
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Tubuloglomerular feedback |
•Macula densa is a chemoreceptor. •If there is too much flow or too much NaCl delivery -> there is more work to do than the distal tubule can handle •That means the GFR is too high. •The Macula densa sends a chemical signal to constrict the AA so the GFR is brought down to level that is better for homeostasis |
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Why regulate the GFR? |
•The GFR is the means by which the kidney cleans the blood. Plasma is filtered.. The useful substances are reabsorbed and the wastes are secreted and excreted... •If the GFR is too low, the blood is not being cleaned? •BUT if the GFR is too high, the tubules is not able to process the filtrate .... Valuable water and electrolytes could be lost in the urine... this would be a threat to blood pressure maintenance. |
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Regulators of GFR hnotes |
•Tone of arterioles (Fig 19-6 c,d,e) •Atrial natriuretic peptide dilates AA–GFR •Blood pressure –hypotension↓ GFR •Blood volume – dehydration–↓ GFR •Constriction of Mesangial cells –↓ GFR •Sympathetic stimulation -↓ GFR until BP can be returned to normal •Angiogensin II –↓ GFR until BP can be returned to normal |
Why is low GFR good? so you dont lose valuable liquids? maintaining blood pressure |
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LEARNING OBJECTIVES |
•Can you draw a nephron and label the parts? •Can you explain the filtration process distinguish between freely filterable and non filtered substances? •Can you explain how the myogenic response (auto regulation) maintains the GFR in the face of changing pressure? •How tubuloglomerular feedback ensures the GFR is not too high? •How do extrinsic factors regulate the GFR? |
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1) exists a Na+ ATPase 2) chloride leak channel here (anion sneaks between cells, at a tight junction) 3) coming through aquaporines 4) they arrive after the other ones because new gradient has been formed. (PARAcellular movement) sneaking between cells
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Reabsorption hnotes |
•Epithelial transport (transcellular transport) –Substances cross apical and basolateral membranes of the tubule epithelial cells –The proximal tubule is responsible for the reabsorption of Na+, glucose, amino acids, Ca2+, and other electrolytes. –Reabsorption is iso-osmotic because water follows particles. •Paracellular pathway –Substances pass through the cell –cell junction between two adjacent cells |
proximal tubule does roughly 66% of the filtration, rest goes to the loop of henle |
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notice that this is one of the few times that glucose must be diffused accross the entire cell. |
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Secretion |
•Transfer of molecules from extracellular fluid into lumen of the nephron –Active process •Important in homeostatic regulation –K and H •Increasing secretion enhances nephron excretion •A competitive process –Penicillin and probenecid |
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Excretion hnotes |
•Excretion = filtration –reabsorption + secretion •Clearance –mL of plasma per minute cleared of a particular substance –Measure of how fast the body gets rid of a substance –Noninvasive way to measure GFR –Inulin and creatinine are used to measure GFR |
highly likely test question: be able to define clearance: ITS BASED ON PLASMA, NOT THE URINE. its a flow that measures the amount of plasma thats been cleaned all forms of clearance has its own clearance rate high clearance = something we normally get rid of low clearance= something we normally dont get rid of. |
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Clearance |
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Measuring GFR |
In your text, GFR is measured by the clearance of inulin... this is true. Best clinical measure of the GFR and renal function is the clearance of creatinine... this is how GFR is measured in clinical settings. Why? Because creatinine is an endogenous substance that is freely filtered, not reabsorbed and only slightly secreted. |
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if you have a low blood volume blood pressure and volume responses hpic |
causes lack of stretch in Atria. otherwise too high. |
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if blood pressure and blood volume is too high..... |
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How kidneys can conserve water |
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Water Balance hpic (osmolarity changes in the nephron) |
•The kidneys cannot replenish lost water; all they can do is conserve it •Diuresis: the removal of excess water in urine –Diuretics: drugs that promote urine excretion •Membrane recycling allows vasopressin/ADH to control which parts of the cell membrane are permeable to water in the distal tubule/collecting duct |
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Loop transporter |
reabsorbs Cl, K, Na, and leaves H20 behind in the nephron. this happens around the loop of Henle. Aquaporins allow water to reabsorb into the body, the more there are, the more that are used. |
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Long medullary Loops of Henle |
•Descending limb –Permeable to water but not salt –Filtrate becomes more concentrated as flows deeper in medulla •Ascending limb –Permeable to salt but not water –Filtrate becomes less concentrated as flow back toward cortex |
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where does that NaCl and KCl and water go |
•It enters the vasa recta capillary bed. •Some of it leaves the medulla by the vasculature. •Much of it stays in the medulla....... •What keeps the particles in the medulla? countercurrent mechanimsm |
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Vasopressin/ADH action to save water is the goal |
•The countercurrent makes the medulla hyperosmotic so that ADH can help a person save water if they need to for homeostasis. •So let’s talk about the collecting duct first. |
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ADH (anti-diuretic-hormone) helps you save water |
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Loop in the Vaso Recta partially obstrict K, Ca, and Cl from leaving medulla. |
this is also opposite of how it works in the loop of henle. |
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Fluid and Electrolyte Balance |
•Vasa recta removes water –Close anatomical association of the loop of Henle and the vasa recta •Urea increases the osmolarity of the medullary interstitium •Because urea is penetrating to RBC... the RBC do not shrink as much as they would in the presence of all non penetrating solute. |
because there is so much urea in the medulla, it is hyperosmotic. Saves the RBC from shrinking until its a raisin. |
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response to eating salt |
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•How is the regulation of the ADH secretion a negative feedback mechanism? –What parameter is being monitored? –What is the stimulus? –What is the response of the body? |
parameter: ECF and osmolarity stimulus: response: ADH helps retain water
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Distal tubule/CD vs. Proximal tubule |
DistalTubule and Collecting Duct •DT/CD fine tunes renal processes according to what is needed for Homeostasis •Smaller amounts of Na reabsorbed •K secretion •Extensive Hormonal regulation |
Proximal tubule •PT is the work horse of the nephron doing the bulk of the work. (called the work horse b/c reabsorption of all the glucose) if you are hyperglycemic, often pee glucose and you have diabetes. •2/3 of Na and water •All glucose and aa •Most drug secretion •Some hormonal regulation |
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Fluid and Electrolyte Homeostasis |
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Blood pressure Regulation is also part of homeostasis |
•Neural •Baroreceptors: are Fast, good at Position changes •Hormonal •RAAS (renin attention aldosterone system) regulates sodium and volume, Slower than baroreceptors. •Volume and Na+ changes |
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RAAS |
•Renin is a kidney enzyme released from the juxtaglomerular apparatus •Catalyzes the production of angiotensin I •Angiotensin converting enzyme catalyzes the production of angiotensin II •Angiotensin means “blood vessel contraction” Angiotensin II is a powerful vasoconstrictor. •Ang II also stimulates the secretion of aldosterone (thirst, ADH secretion, cardiac effects). •Both hormones raise blood pressure via negative feedback |
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The primary action of aldosterone is renal sodium reabsorption. |
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Q: Notice that elevated plasma K+ also stimulates aldosterone. Why is this beneficial? ANS: Cardiac regulation. we dont want depolarization, we need normal resting potential. Extra cellular Potassium: normally at 4mM, at 6mM it hurts, at 10mM you are dead. aldosterone saves you. |
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Aldosterone is a steroid Works via gene transcription |
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If blood pressure is too low |
1.Baroreceptors are less stretched and activate sympathetic afferents. 2. The afferent arteriole is less stretched. 3.The GFR decreases and less NaCl/flow arrives at the macula densa |
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Potassium Balance |
•Regulatory mechanisms keep plasma potassium in narrow range –Aldosterone plays a critical role •Hypokalemia –Muscle weakness and failure of respiratory muscles and the heart •Hyperkalemia –Can lead to cardiac arrhythmias |
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Acid–Base Balance |
•Normal pH of plasma is 7.36 –7.44 •H+ concentration is closely regulated –Changes can alter three -dimensional structure of proteins •Abnormal pH affects the nervous system –Acidosis: neurons become less excitable; CNS depression –Alkalosis: hyperexcitable •pH disturbances –Associated with K+ disturbances |
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Acid and Base Input |
•Acid –Organic acids –Diet and intermediates –Under extraordinary conditions –Metabolic organic acid production can increase –Ketoacids –Diabetes –Production of CO2–Acid production •Base–Few dietary or metabolic sources of bases |
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pH Homeostasis |
•Buffers –Moderate changes in pH –Combine with or release H+ –Cellular proteins, phosphate ions, hemoglobin, bicarbonate •Ventilation –Rapid response –Corrects 75% of disturbances; can also cause them •Renal regulation –Receptor -mediated endocytosis –Directly by excreting or reabsorbing H+ Indirectly by changing in the rate at which HCO3– buffer is reabsorbed or excreted |
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Renal Compensation: Transporters |
•Apical Na+-H+exchanger (NHE) –more in PT •Basolateral Na+-HCO3=symport •H+-ATPase = More DT and CD •H+K+-ATPase = More DT and CD |
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pH homeostasis along tubule |
•PT –H+ is secreted across the luminal membrane via secondary active transport in exchange for Na+ •DT–small amounts of Na left in the filtrate. H+ secreted across the luminal membrane by primary active transport •Both tubules –HCO3- reabsorbed across the basolateral membrane by some mediated mechanism |
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Acid base Homeostasis |
•If the blood is acidic, the urine will be acidic –Tubules secrete more H+ and reabsorb more HCO3- •If the blood is basic, the urine will be less acidic) –Tubules reabsorb less HCO3-(andsome cells secrete HCO3-), secrete lessH+ |
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Wall of the gut |
•Mucosa (inner most layer) –Created from epithelial cells, lamina propria, and muscularis mucosae –Modifications increase surface area –Rugae and plicae –Villi (only in small intestine) –Gastric glands, crypts, and submucosal glands (both small and large intestine) –Peyer’s patches of the gut -associated lymphoid tissues (GALT) |
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Wall of the gut |
•Submucosa (regulates sectretion) –Connective tissue (most of it) –Contains submucosal plexus of the enteric nervous system •Muscularis externa (source of motility, moving mucosa around) –Consists of two layers of smooth muscle (circular"makes is smaller" and longitudinal layer "makes it shorter") –Contains myenteric plexus of the enteric nervous system •Serosa –Continuation of the peritoneal membrane, which forms sheets of mesentery |
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Four processes of the Digestive system |
Digestion: chemical and mechanical breakdown of food into absorbable units. breaking bonds Absorption: movemnt of material from GI lumen to ECF ( stomach to blood) not regulated, responds to other three processes Motility: movement of material through GI tract as a result of muscle contraction Secretion: movement of material from cells into lumen of ECF |
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Motility |
•Slow -wave potentials –Originate in interstitial cells of Cajal (pacemaker type cells) if its below threshold, everything is relaxed –Intrinsic activity that is modulated by presence of food, ANS, hormones (food activates everything) •Peristalsis (mainly in large intestine) –Wave like contractions that move chyme forward. –Found throughout the GI tract. •Segmentation (mainly in small intestine) –Several ring like contractions along the gut –Promotes mixing and absorption –Major motility in small intestine |
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Polarizations of GI tract |
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types of segmented movement peristalsis and segmentation hpic |
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Autonomic nervous system |
•Sympathetic nervous system (SNS) (inhibit everything, secretions, bloodflow) –Postganglion neurons release NE –Tends to inhibit digestive activity •Parasympathetic nervous system (PNS or VAGUS) –Postganglionic neurons release acetylcholine –Tends to stimulate digestive activity –Mostly vagus controls but sacral nerves control lower GI tract •Enteric nervous system (ENS) lots of intrinsic neurons, regulated by extrinsic neurons –Can serve as a control center for local reflexes |
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ENS Shares Features with CNS |
•Intrinsic neurons –As many neurons in ENS as in spinal cord –Modulation by Extrinsic neurons (autonomic neurons) that bring signals from CNS to digestive system •Neurotransmitters and neuromodulators •Acetylcholine and serotonin are major neurotransmitters •Glial support cells •Diffusion barrier •Integrating center –Minibrain of the GUT |
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Endocrine Secretion -Digestive Hormones |
•Gastrin family –Gastrin and cholecystokinin (CCK) •Secretin family –Secretin, vasoactive intestinal peptide (VIP), glucose-dependent insulinotropic peptide (GIP), and glucagon-like peptide-1 (GLP-1) •Others –Motilin all found in CT.11.3 use table 21.1 to fill it slide15 |
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Exocrine Secretion |
•Digestive enzymes secreted into mouth, stomach, and intestine •Mucous cells in stomach, serous cells in salivary glands, and goblet cells in intestine –Mucins •Saliva is an exocrine secretion •Liver hepatocytes secrete bile –Bile salts, bile pigments, and cholesterol –Gallbladder stores and concentrates –Hepatic duct and common bile duct |
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Wrapping up digestion |
-GI is big long tube, exocrine secretions are brough to the gut (like saliva) secretions from the liver and pancreas, like bile and other enzymes. -pacemaker cells (interstitial cells of Ga-kal?) -in order, Cephalic system (feedforward) when you smell --> Gastric phase --> intestinal phase (feedback) ---> integration |
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The Cephalic Phase |
•Chemical and mechanical digestion begins in the mouth •Salivary secretion is under autonomic control –Softens and lubricates food –Chemical digestion: salivary amylase and some lipase –Saliva also has a protective function, antibacterial •Chewing: mastication |
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Sensory system |
Cephalic phase: see food -> medulla oblongata -> parasympathetic neuron in vagus nerve -> enteric plexus ->postganglionic parasympathetic and intrinsic enteric neurons Gastric phase: secretion of saliva and movement of food towards stomach all sympathetic neuron controlled |
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1.Tongue pushes bolus against soft palate and back of mouth, triggering swallowing reflex. •Starts voluntary •Converts to a reflex 2.Breathing is inhibited as the bolus passes the closed airway. 3.Food moves downward into the esophagus, propelled by peristaltic waves and aided by gravity |
Swallowing is integrated in the medulla oblongata. Sensory afferents in cranial nerve IX and somatic motor and autonomic neurons mediate the reflex. Has to be a long reflex with the CNS as a control center because |
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Esophagus |
-upper esophageal sphincter opens with swallowing -upper third of muscularis is skeletal muscle and transitions to smooth muscle -if bolus of food is stuck, local reflexes continue peristalsis -lower esophageal sphincter is below the diaphragm (positive pressure of abdomen keeps closed, and reflux can occur if LES is pushed into thorax) |
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Gastric phase |
Three functions of stomach: (storage: stomach)( digestion: stom.... unfinished |
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Gastric glands in the gastric mucosa contains cells that secrete hnotes |
•HCl –part of barrier defense •Pepsinogen ->Pepsin –secreted first as a ZYMOGEN –Activated by HCl in the lumen of the stomach. Why is this protective? (you dont want to digest yourown cells, just the food) enzyme waits until it reaches the food until it activates •Mucus –protective layer –Depends on prostaglandins and good blood flow •Intrinsic factor-helps absorb Vitamin B12 •Gastrin: made by G-cells, puts gastrin into the blood, excitatory hormone, activates the gastric system |
pepsin is what actually digests the food, HCl is what activates the pepsinogen to turn into pepsin |
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Acid secretion regulators |
•Proton pumps are not always in the plasma membrane. Inserted with the appropriate stimulus •Gastrin •Vagal stimulation •Acetylcholine •Histamine •Inhibited by somatostatin |
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Acid secretion regulated by negative feedback |
•Food in stomach increases pH –Stimulates ENS->ACH, gastrin, histamine ->increases acid secretion •Emptying decreases pH –Stimulates somatostatin ->inhibits acid, gastrin and histamine |
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Gastric emptying |
Gastric emptying •Pacemakers in upper gastric muscularis start peristalsis •Wave of contraction builds as it travels along the muscularis (starts w/ little depolarizations, then builds till its a giant contraction that shuts pyloric sphincter) •Pylorus contracts and allows no more than a couple of tablespoons of chyme to enter the SI •Gastric contents forced up away from pylorus to churn for awhile •Allows the SI time to process the small amount just emptied |
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structure of the small intestine (short reflex, enteric nervous system) |
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The Intestinal Phase Secretions
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•Bicarbonate neutralizes gastric acid •Goblet cells secrete mucus for protection and lubrication from acid •Bile from the gallbladder(made from liver) for fat emulsion •Digestive enzymes (pepsinogen, mucus, bicarbonate acid, intrinsic factor) –From pancreas –amylase, protease (zymogens), lipase, nuclease –Brush border enzymes(made of microvilli)–lactase, Enteropeptidase |
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THE VILLUS AND A CRYPT IN THE SMALL INTESTINE |
the crypt is going to secrete saline solution that liquifies the contents of small intestine, also crypt secretes hormones, CCK, secretin, motillin. Villus: secretes mucus and absorbs fluids and nutrients. countercurrent for oxygen exists here. |
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exocrine vs endocrine secretions |
exocrine: mucus endocrine: gastrin |
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Digestion and Absorption |
Digestion and Absorption •Nucleic acids (DNA and RNA) are digested into nitrogenous bases and monosaccharides •Intestine absorbs vitamins and minerals –Fat-soluble vitamins are absorbed with fats –Water-soluble vitamins are absorbed by mediated transport –Vitamin B12 is absorbed when complexed to intrinsic factor and absorbed in the ileum –Mineral absorption usually occurs by active transport –Iron and calcium absorption is actively regulated –Sodium is absorbed by enterocytes and colonocytes |
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Absorption Review |
•Glucose –taken up by secondary active transport into cell ->facilitated diffusion basolateral side ->into blood •Amino acids –luminal side by secondary active-> basolateral side by facilitated diffusion ->into blood •Triglycerides –luminal side by diffusion-> basolateral side via chylomicrons->into lymph |
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Motility |
•Slow-wave potentials (electrical event) –Originate in interstitial cells of Cajal –Intrinsic activity that is modulated by presence of food, ANS, hormones •Peristalsis –Wave like contractions that move chyme forward. –Found throughout the GI tract. •Segmentation –Several ring like contractions along the gut –Promotes mixing and absorption –Major motility in small intestine •Motilin and migrating myoelectric complex (happens when nothing is there..) moves residual food through the intestine |
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Pancreatic secretions |
•Pancreatic acini secrete digestive enzymes (regulated by CCK) and bicarbonate (regulated by secretin) this all regulates small intestinal mucosa, because thats where the food is located and where the stimulus is. •Fatty acids and amino acids in duodenum-> plasma CCK ->enzyme rich pancreatic secretion flow through the Sphincter of Oddi to the lumen to digest substrates. •Acid in duodenum ->plasma secretin ->bicarbonate rich pancreatic secretions flow into lumen to neutralize acid. |
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lumen of small intestine |
when we send enzymes into the gut (GI tract) interacts with zymogens. Trypsinogen makes trypsin go into gut and do stuff |
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Bicarbonate secretion in the pancreas and duodenum |
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describe the use of bile |
Bile is a secretion, but it causes the breakdown of things that also make excretory products. bile emulsifies nutrients so that your pancreas can absorb it. |
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