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Part 3 Physiology 206 Notes Renal System Renal System 1.) Kidney 2.) Urine bladder * Not going to go into this Kidneys - Major function- to regulate: 1.) Total fluid volume 2.) H+ concentration in extracellular fluid 3.) Regulate salt balance 4.) Elimination of wastes - Have 2 kidneys with outer capsule - Beneath capsule is cortex - Beneath that is medulla - Blood came in through renal artery - Blood leaves through renal vein - Some fluid leave blood, in kidneys - This fluid then leaves through ureter - The cortex is red and meaty- highly vascularized - The medulla is dull grey- poorly vacularize - Afferent arteriole breaks into capillary bed, in cup, then glomerulus capillaries - They empty into efferent arteriole, it breaks up into another bed of capillaries, Peritublar Capillaries- blood supply for most of nephron, drain into a venule, which carries blood off. Portal System - you have arteriole drain into capillaries bed to another arteriole to another capillary bed to venule. - Collecting duct gathers from many nephrons. - Collecting ducts eventually flows to ureters. 2 Kinds of Nephrons 1.) 80% are Cortical Nephrons- it is entirely located in the renal cortex. 2.) 20% are Juxtamedullary Nephrons- Bowan’s & convoluted tubule in cortex, but the Loop of Henle is in the medulla; Loop of Henle is very long. -- Only about 15% of blood flow gets into the Renal Medulla. -- The medulla is bigger; so blood flows 20x faster in cortex. Three Major happenings in Kidneys 1.) Glomerular Filtration- just as in other capillaries, does not let out proteins the pressure in glomerulus is higher than most capillaries, due to a resistance vessel. because pressure is higher, more fluid out. -- 20% of plasma volume filtered out- known as glomerular filtrate. plasma without the protein Average everyday, filters out 180 Liters or 50 gallon a day Urinate about a liter a day- reabsorb 179 Liters out of every 180 liters produced. Kidneys will reabsorb about 99% of solute, as well. During the movement through the Nephron: 1.)will reabsorb some stuff-out of lumen into ECF-99.5%; different solutes will be reabsorbed at different rates. 2.) Reabsorption, secretion, and Glomerular Filtration are 3 processes that account for most of the functions of kidneys. Glomerular Filtration Because of 2nd Arteriole: - Pressure in capillary is higher than in most systemic capillaries, so rather little fluid get reabsorbed. - 20% of plasma volume gets pushed into Bowman’s Capsule - Then after moves through second arteriole, into another capillary bed, has lower pressure, due to lower volume, so when it gets into peritubular capillaries, it has lower volume, so it makes it closer to systemic capillaries. - 99% leaves instead of 100%; this is a 2-step process Glomerular Filtration Rate (GFR) Rate = 125mL/min. - this can vary due to the hydrostatic pressure- driving force - Higher pressure = higher rate - Anatomically this is set up to be easy, if you constrict efferent, you increase pressure upstream, which increase GFR. Constrict afferent, reduces GFR. - Most of physiological control, comes from sympathetic stimulation, and the sympathetic nerves supply is much denser to afferent than to efferent, so afferent constricts, so reduces GFR. GF protein is free plasma in out urine - add to secreted. Reabsorption - tends to be active/utgrous (useful) reabsorbed - sluggish/toxious 2 classes for: 1.) Active Transportation - moves uphill against gradient - needs energy (ATP) 2.) Passive Transportation - facilitated diffusion (carrier molecules;mostly protein) High Concentration Low Concentration - Simple Diffusion across cell membrane - Huge amount of sodium & reabsorbed Responsible for osmotic pressure. - Drives passive reabsorption of negative ion - Most other active transport systems only work with sodium reabsorption. Sodium Reabsorption Sodium pumps on Basal part of cell, pumps sodium out of cell into ECF, so inturn, the cell diffuses out of lumen into cell, in which sodium came from. - Most reabsorption happens in the tubule proximal. - Na+ enters Bowman’s capsule 100% ~Not subject to control proximal tubule 100% enters 80% reabsorbed Loop of Henle 20% enters (10-12) ~All control excerted here Distal tubule 8% enters collecting duct; urine 1% or less. - Glucose & Amino Acids Active Transport - Amount of compound entering tubule is called tubular load (plasma concentration x GFR) Average- Normal load- 125mL per minute Transport Maximum- maximum amount of glucose being reabsorbed in nephrons (400mg/min.) Diabetes Mellitus- urine volume goes up with high volumes of glucose. -- When actively reabsorb sodium, passively reabsorb chloride. -- Also reabsorb water due to reabsorption of chloride. Some secretions are added to tubule: Hydrogen Ion (H+)- actively secreted most important for fine tuning of the pH Potassium Ion (H+) & Organics (Drugs)- actively secreted Plasma Clearance - typically produce 1-2L a day (1mL a min.) - that amount is the difference of the plasma that is filtered and the plasma that is reabsorbed. - One useful way to look at amount it is from what volume of plasma would you have to completely remove this compound to get it to show in the mL/min. -- Plasma Clearance = volume of plasma containing amount or “x” that appears in the urine in 1 minute. - this is use because the larger the amount of volume that is cleared; the more efficient the removal is. - Compound named Inulin (Garlic, Onions); one interesting characteristic is that it is filtered as any small compound in kidney, but it is not reabsorbed nor secreted at all. what that means is that the amount of inulin that got into lumen is same amount that is in urine per min. this means that the plasma clearance is the Glomearular Filtration Rate; so if you know the Plasma Clearance; you know GFR = 125mL/min.; how it is measured. Inulin is not something we normally have in the lobby. Alternatively, one can measure creatinine- which is in the body, normal metabolic product. - it is not quite as nice as inulin, it is not secreted & very little reabsorbed. Para-aminohippuric Acid (PAH)- it is not reabsorbed, and it is secreted actively enough, so that it is reasonably true that PAH is completely removed in a single pas through the kidneys can use this measure Renal Plasma Flow. How one Regulate the Concentration of Urine Juxtamedullary: Vasa Recta- straight tube Descending limb in the Loop of Henle, in juxtamedullary: 1.) freely permeable to water 2.) doesn’t pump sodium Ascending limb in the Loop of Henle in juxtamedullary: 1.) has powerful sodium pump 2.) rather impermeable to water -- this is a positive feedback loop that is physiologically normal & important -- this process is due to the fact that H2) can cross descending easily, that sodium can easily be pumped in ascending, and that countercurrent affects the sodium concentration in descending due to pump in ascending. -- the reason that the body doesn’t take up all the sodium, is due to the vasa recta- which carry some sodium away, and at some time will reach a steady rate, and that will occur when around 1200 milliOSM in descending tube, and 300 milliOSM at border with the cortex, where you have great blood flow. -- the lack of great blood flow in medulla is what allows the sodium concentration to build. -- all of the nephrons move into connecting duct; about 300milliOSM. -- If the connecting tube is impermeable to water, it stays at 300milliOSM -- If the connecting tube is freely permeable, than then end result is 1200 milliOSM -- Antidiuretic Hormone (ADH)- reduces urine volume by increasing the water permeability, which reduces the amount of urine. acts in collecting ducts. ** Sodium Diffusion - 180 liters of filtrate per day - osmotically reabsorb 179 liters per day - if water diffuses, the solute becomes more concentrated, even if it can diffuse across - anything that diffuses slower than water, will diffuse out, due to the concentration gradient - there is nothing known that diffuses as rapidly as water - which results in the solutes that would diffuses, become more concentrated. - outcome is, it makes tube long, the difference in amount of water & solute diffused is greatly different. There is higher concentration at 1 end, so higher in urine, when in the plasma. Balance - refers to relationship between what is going on in the input & output Ex.- temperature- amount of heat take in & amount of heat absorbed is equal - when outputs and inputs are equal, it is called Stable Balance Stable Balance : Outputs = Input - If the output is greater than input- Negative Balance - If the input is greater than output- Positive Balance - Can exist in any physiological occurrence Fluid Balance - We exert very little control on the input side- thirst is a primitive way Changes very little day to day - We exert reasonable amount of control on the output Average Person- 150 lbs. 70 kg 42 kg of water 60% Body Weight 28 kg of other stuff -- Water is in two major compartments: 1.) Intracellular- all very similar to each other, not like extracellular = 40% has very high concentrations of Potassium, Proteins 2.) Extracellular- also very similar to each other, not like intracellular = 20% High concentration of Sodium, Cl- The way to regulate the volume, through kidneys, for most part. Sources that we can get rid of Fluid Have control 1.) Ingestion No Control 2.) Metabolism Sources that we can get rid of fluid Have control 1.) Urine No Control 2.) Perspiration No Control 3.) Sweat- in very high fevers, over 105 F, the sweat mechanisms shut down Behavior of Acids & Bases - Ionic Bonds- positive and negative, so they bond. NaCl Na+ ClCation- positive Anion- negative - Dissociation- when you put into water, the two ions come apart- NaCl Na+ Cl this can be reversed, this is called Association - Ions can move - Reason salt water is a better conductors is due to salts - Because salts can carry a current, they are called Electrolytes Law of Mass Action A = Anion; C = Cation AC A- + C+- this is reversible Constant (K) = [A] [C] [AC] -- A consequence of this is that the concentration at all the constituates, in reversible actions depend on each other. If you change one thing, you simultaneously change the other two. Simultaneous Equilibrium- Two salts in some solution, and one ion is found in both solutions, and what will happen is that concentration that each constiuates will equal the constant at same time. AD A- + D+ AC A- + C+ KD = [A-] [D+] KC = [A-] [C+] [AD] [AC] *AC + AD A- + C+ + D+* - Any biological fluid is made up of many salts in solution, with many common cations and anions, simultaneous equilibriums. - Consequence is that when one ion is changed, they are all effected - Hydrogen Ion (H+) is a cation- the greater the H+ concentration, the more acidic - Acid- anything that makes H+ increase - Base- anything that makes H+ concentration decrease When in acidic balance means that H+ concentration is constant - As with any ion, it is reversable. - When an acid dissociates, you get at H+ and an anion - Water dissociates- H2O OH- + H+ KH2O = [OH] [H+] H20 Pure water is around 55.5 M or Moles/Liter always 10 -14 = [OH] [H+] - Water concentration doesn’t change much; H+ = [OH] = 10 -7M- this is called Neutrality - Anything that makes one go up, must make the other one go down. - There is a very wide concentration, 1 to 14 - A way to make this easier, use pH = -log[H+] - Log10 = 1; Log100 = 2; Log1000 = 3 / Log1 = 0; Log0.1 = -1; Log0.01 = -2 the way you can express a number is log rhythm- amount of Os - If [H+] = 10-7 log[H+] = -7…. So –log[H+] = 7 the lower the pH, the higher the H+ concentration. Weak Acid- Acetic Acid- around pH= 4; low tendency to dissociate Strong Acid- Hydrochloric Acid- around pH = 1; high tendency to dissociate K = [H+] [Ac-] [Hac-] ~~ pK = -logK ~~ K will be smaller for acetic than for HCl ~~ If top is big and bottom small, large pK ~~ If big bottom, small top, small pK ~~ K in HCl is in ballpark of 1 - When pH of solution is identical to the pK of the acid, 50% of Acid is Dissociated - Position with differ for each solution. - there is very little change in pH, right around pK Buffering- the ability of an acid to resistance the change of pH when near pK. weak acids can buffer the effect of adding strong acids, and they do this best around their own pK. - If you add an electrolyte, it will dissociate, and effect the H+ concentration NaAc Na+ + Ac- - You can effect pH by adding acid, base, or a neutral salt. H+ Balance - Body has normal H+ Balance; -10-7M + -10-8; around pH = 7.4 Survival- 7.0-7.8 - Body has good ways of getting back to neutral balance in H+ Facts: - Artieral pH ~ 7.45 - Venus pH ~ 7.35- more acidic because body makes CO2 in tissue & when CO2 in H2O; it spontaneously hydrates to form Carbonic acid, which dissociate to form H+ & bicarbonate. add CO2, it will become more acidic in systemic H+ goes up; CO2 goes up in lungs CO2 goes down; H+ goes down - Arterial pH greater than 7.45 = Alkalosis- makes nerves hyperexcitable, which can cause unusual perception & sensation, spasms, and convulsions. - If it is more acidic than normal, below 7.45 = Acidosis- depresses neural activity; can become comatose & stop breathing. ** Can’t go beyond 7.0-7.8 for more than a few minutes ** What Contributes to H+ Balance (Sources) 1.) Diet- input- take in some acid when eat(OJ, Salad Dressing) this is not very important, quantitatively 2.) Most H+ arises Metabolically in production of CO2 3.) Digestion of Meats Inorganic Acids 4.) Metabolic Production of Organic Acids (mostly lactic acid) Disruptions to H+ Balance 1.) Vomiting- acid secreted in stomach, which is normally reabsorbed is gone, which causes person to become Alkalontic. 2.) Diaherrea- lots of alkaline material is not absorbed, person is left acidic. ** Most of physiological systems are trying to get rid of H+ ** Mechanisms for maintaining pH in ECF 1.) Chemical Buffers- work instantly; do not have concentrations in plasma, the quantitative is small, hardly matters if they did exist. 2.) Respiratory System- lose CO2 to Atmosphere; very rapid & high capacity; not very precise 3.) Kidneys- give precise control, to get back to 7.4 Chemical Buffers a.) Most important- Bicarbonate: CO2 + H20 H2 (Carbonic Acid) HCO3 (Bicarbonate) Reason is there is so much CO2 in bicarbonate. limitation; its pK= 6.1; not a terribly effective buffer Two things that make it important 1.) In respiratory system, make very rapid adjustments to CO2 2.) Kidney system make precise adjustments of bicarbonate. b.) Protein- these can buffer in 2 different directions. there is a lot of protein in plasma virtually protein free in ECF Hemoglobin- single most important single protein for buffering; very abundant; most protein in whole body. -- Made more effective by Bohr Effect- Hemoglobin affinity of O2 falls as H+ rises. When in more acidic areas, its affinity for H+ rises. c.) Phosphate - pK right around 7.3, so it has best buffer quality, at ideal spot - doesn’t have very much there though, so not real effective. Respiratory System - Vary alveolar ventilation rate with changes in plasma pH - the greater the alveolar ventilation, the greater we lose CO2 - lose CO2 more rapidly, decrease H+ concentration - loss CO2 less rapidly, increase H+ concentration - when H+ rises, Alveolar ventilation rate goes up, making H+ lower - because more large CO2 amount through lungs, has huge range, which it can respond, but control mechanisms that adjust pH changes, become relatively weak near pH balance, so that you never get quite back, by respiratory system. Kidneys - fine tuning; final precise adjustments - can secrete H+ ion - actively reabsorb bicarbonate - Both secretion & reabsorption amounts controlled by pH - Both are moderate amounts; slow but very precise - Takes about a day to readjust; if hold breath, respiratory system brings it back to around 7.3, then by the next day, kidneys would have it back to 7.45. Alkalosis = Arterial pH greater than 7.45 Acidosis = Arterial pH less than 7.45 - Either one can arise by: 1.) Metabolic- Diaherrea- lose large amounts of bicarbonate; that causes metabolic acidosis, which has nothing to do with respiratory system; your bicarbonate level goes down, in metabolic acidosis. -- Anaerobic exercise produces lots of lactic acid, which makes more acidic; can’t lose through Respiratory System; this process is metabolic. 2.) Respiratory- any imbalance that arises in inappropriate rates of loss of CO2. Ex.- hold breath, will become acidotic because stopped loss of CO2. -- pH is not normal; but Bicarbonate is approx. normal level Digestive system - General- mouth to anus & organs in between (stomach, Small Intestine, large intestine) What it does - Break down food into small particles (mechanical) - Large molecules to small (digestion) to be reabsorbed - Secreted fluid into lumen of gut (stir up) - From lumen into blood stream ** Important to coordinate activities of the GI system ** 2 Major Divisions: 1.) Gastrointestinal Tract Gut, mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus. 2.) Glands that empty into the Gut Salivary glands, exocrine pancreas, biliary system ( liver & gallbladder) Gut’s Properties (tube) - layered structure that is constant throughout. Order of layers (inner to most out) 1.) Lumen 2.) Mucosa 3.) Submucosa (connective tissue) a.) musculeris externs (major smooth muscle coat) 4.) Inner circular muscle = change diameter (smooth muscle) 5.) Outer longitudinal muscle = lengthen & shorten (smooth muscle) 6.) Serosa (through connective tissue) 7.) Mesentery Nervous Networks 1.) Submucosa Plexus = control local activity of each gut region 2.) Mesenteric Plexus (runs length of gut) lies between two muscle layers Works with Submucosa Plexus regulation local gut activity Splanctric Circulation (portal system) - Blood supply to GI system Some Interesting Features: all blood that leaves stomach, pancreas & intestine goes straight to liver absorb through intestine; liver gets crack at it before it gets through body circulation. eat something toxic; liver gets a chance to metabolize/ remove toxins before it enters the body. 4 Things that happen in Digestive Process 1.) Motility (mechanical event) - Muscular contractions move things 2 Types of movements: a.) propulsive b.) mixing 2.) Secretion- adding juices into lumen of gut 3.) Digestion- break down process for absorption 4.) Absorption- out of lumen into circulation Principle of Motility - upper 1/3 of esophagus is skeletal muscle; the rest is smooth muscle - smooth muscle have to do with mixing (VERY IMPORTANT) - 2 types of movement 1.) Perstolic contractions (move food through GI) 2.) Mixing (2 fold function) a.) Mix with digestive juices b.) Facilitate Absorption (exposes contents of lumen to absorbing surfaces) Secretion into Gut 2 Major Sources: 1.) Glands in wall of gut into lumen 2.) External glands that have tubes leading into gut (ex. Pancreas) - Goblet cells in mucosa of gut, which lie throughout inner length of tract. Secrete a fluid which acts as a lubricant (mucosa fluid) Serous Fluid - Adjust pH - Helps digest large molecules - Added to food to make it more fluid like General Mechanisms of Secretion - synthesizes and stores in cell - when it gets stimulated, it activates sodium pumps, in cell, get going. - Cell volume increases, so the membrane by the lumen expands, until it busts & the contents go out into the lumen. - Involves sacrificing cell - A cell life in GI Tract is very short, so if it secretes, it is a good thing. - All things that go on in the gut, need to be coordinated. local mechanisms stimulate, that is why things are all coordinated. Secretion happens mechanically by food particles against cell Mechanical stimuli in gut, cause what gut does -- Two other coordinating systems: 1.) Neural- brain control a.) Short reflex- mechanisms that occur without any info going past plexuses; occur entirely within the wall of the gut. b.) Long reflex- mechanisms that include nerves that go outside gut. 2.) Humoral- controls carried in the blood stream -- Hormones secreted in GI System to stimulate other parts of the GI system. From Head To Toe - most food intake is a big piece the size is big enough that you would have trouble getting it down. Chewing: 1.) Reduces the size of the particle- prevents strangling 2.) Breaks cellulose hulls- humans can’t breakdown cellulose, so it opens it up 3.) Stimulates the Oral Cavity Surface- secretes saliva Chewing Reflex 1.) When you put food in mouth, receptors in roof of mouth are stimulated by pressure, sends afferents to the brain-jaw muscles relax; jaw drops. 2.) Initiated by stretch receptors in jaw muscles activate- afferent; jaw muscles contract- efferent. -- this is a cycle which would go on forever, except that we swallow, which reduces pressure each time. Salivary Secretions Normal Resting Rate = 0.5 mL/min. Which makes you swallow. This is important: 1.) Keeps inside of mouth moist, which is important for speech. 2.) When dehydrated, the secretion goes down, which stimulates thirst. 3.) A source of alkaline fluid in mouth, which balances the acidicness of bacteria between teeth. - Most of stimulation is a result of a mechanical stimulation. - In addition to mechanical stimulation, strong neural stimulation also. - Anything that makes you anticipate eating, does this. Pavlov- conditioned reflexes. 3 Pairs of Salivary Glands: 1.) Parotid 2.) Submaxillary 3.) Sublingual -- On average, produce 1 to 2 Liters a day, which is mostly swallowed. There are 3 kinds of Secretions: 1.) Alkaline Serous- nothing to do with digestion; maintain normal pH around 7.8 2.) Digestive Serous- use in digestion, includes enzyme- Salivary Amylase- which breaks down starch into smaller units. Really doesn’t do much in the mouth because we typically swallow every few seconds. But swallowing goes down into stomach, and Salivary Amylase likes alkaline, which is what empty stomach is, but after 30 minutes, stomach gets too acidic for Salivary Amylase. 3.) Mucous- lubricant Swallow: - We chew, and at some point, we initiate swallowing: Voluntary Phase of Swallowing (takes around 1 sec.) - involves front of tongue pressing against palate pushing food back to the pharynx. This is the END of the Voluntary part. Involuntary Phase of Swallowing - Once bolus gets to soft palate, a bunch of reflexes kick in: 1.) Nasal passages get closed, due to the elevation of the soft palate. 2.) Larynx rises, so the top gets covered by epiglottis. 3.) Muscles in pharynx that allow tissue to contract, so the track leading to esophagus, is like a slit, not allowing big food to enter. 4.) Back of tongue and muscles of pharynx force whatever is in the mouth, into the esophagus. 2 Sphincters in Esophagus: 1.) Pharyngoesophageal Sphincter (skeletal muscle) 2.) Gastroesophageal Sphincter -- Normally they are closed tightly don’t swallow a lot of air- Pharyngoesophageal prevents stomach contents from refluxing into esophagus- Gastro Primary Peristaltic Wave - When bolus is pushed to back, upper sphincter opens automatically, and a wave of peristalsis goes down esophagus, which causes lower sphincter to relax. Wherever the bolus is left in the esophagus, stimulates a 2 nd wave from that spot, to finish job. - Normally takes about 10 seconds - Since skeletal muscle doesn’t propagate action potentials, nerve plexuses are important; they propagate through the whole gut; *only go down; * Very rapid. Heartburn- burning sensation in middle of chest - stomach acid refluxes into the esophagus - Hiatal Hernia- sphincter is in thorax; so when ab pressure, it doesn’t get more tightly closed, like normal, so when pressure gets great enough, stomach contents get pushed into esophagus. Stomach - Functions: 1.) Stores food & gradually releases into intestine (motility)- the flow into intestine is spread out. 2.) Mixes the contents with secretions made in stomach. - Food Storage: -- Receptive Relaxation- smooth muscle able to change its length with very little change in tension. When put food in, smooth muscle relaxes, it gets bigger, but very little change in tension has occurred. So the pressure really isn’t effected. This happens up to about 1 liter, then starts to go up more rapidly. - When there is stuff in stomach, there are peristaltic contractions going on across the length of stomachchurning up the contents. - At the other end of the stomach, another sphincter- Gastroduenal Sphincter (Pyloric) this stays always just a little open, so every contraction, stuff gets squirted into small intestine. -- greater the volume, greater the frequency of peristaltic contractions -- the fuller it is, the faster it empties - Cells in stomach secrete Gastrin- gets released into blood stream: Makes smooth muscle in stomach contract more rapidly; stimulating peristalsis - Stimulus of gastrin is produced by Partly digested protein, so; Stimuli = Partly Digested Protein Response = Secretion of Gastrin to Circulation 2nd Response = Increased gastric peristalsis - In response to high level of acidity, or fat, in small intestine, the small intestine then releases hormone that slows it down, and the same hormone is produced with fat entering, so digestion is slowed down with a high fat meal. Drink cream before going out drinking, slows rate the alcohol is absorbed. Secretion in Stomach - Makes or secretes between 2-3 Liters into lumen - There are glands in stomach walls that secrete directly into lumen 1.) Mucous Cells- in the wall- secrete mucous 2.) Chief Cells- secrete pepsinogen, which can be converted to pepsin, in high acidity- pepsin is a gastric protease, which break down protein. 3.) Parietal Cells- secrete strong HCl acid.- makes stomach contents very acidic, which causes pepsinogen to convert. The high pH also leads to breaking down connective tissue Kills most of the bacteria in food Blood supply to stomach brings HCl into it; and when blood leaves stomach, it is more alkaline. The Secretions have Phases (especially with Parietal) 1.) Cephalic Phase- will release at anything that makes you think food; controlled by CNS 2.) Gastric Phase- secretion that is more or less locally controlled by the amount of food being brought in. 3.) Intestinal Phase- there is neural mechanism- to inhibit & humoral mechanism, or reflex, in intestine, that cause a release of hormone, which inhibits gastric secretion. It is good to have 2 controls: Neural- instantaneous but receptors fatigue, can’t prolong control Humoral- it prolongs the reaction, but isn’t instantaneous - Pepsin is the only digestive enzyme that the stomach produces. Is not the only digestive enzyme working though; Salivary Amylase is also working. - Very little is absorbed through the stomach. Secretion of Pancreas: - Consists of 2 Organs, but for Digestion, only going to focus on one: Exocrine Pancreas- produces alkaline fluid; which is important for neutralizing; venus is acidic. - Produces digestive enzymes- on the list is anything you eat that you can digest- very long list, which includes proteins that are capable of breaking down nucleic acid, fats, etc. Bile - Small intestine sends out hormone, that inhibits stomach, and stimulates gallbladder, to send bile. - Liver Bile Gallbladder Small Intestine - Liver produces Bile Salt = Detergents - Emulsification - Bile gets squirted into small intestine, which promotes the digestion of fats. - Bile Salts coat the fats and absorb; then the bile salts get reabsorbed. - Then go back to the liver, which reabsorb the bile salts ( sort of a recycling system) - In the absence of gallbladder, there is a feedback system , that works fairly well, so if they have fats in moderate levels, they will be ok. Self regulate very rapidly. Small Intestine - 10 ft. long - End connected to the stomach is called Duodenum- 5 ft.- where most happens - Jejunum- 2 1/2 ft. - Ileum- 2 1/2 ft. - Most of digestion happens in small intestine - There is a kind of motility that is peculiar to the small intestine, called Segmentation Contractions- stationary rings of constriction; they relax and new ones form in other places. - Nice stirring mechanism. - There is peristalsis in small intestine- major source of motility- normally extends 3-6 inches - When there is a source of irritation (bacteria) can cause a single peristaltic wave that can move rapidly through whole intestine. The Peristaltic Rush- is trying to remove the irritation rapidly. - 3rd kind of motility is called Muscularis Mucosae the wall of the intestine isn't smooth,it's called villus, so when the M.M. contracts; the villus shortens; volume decreases, and the lost volume goes to ECF into Lacteal, to Veins. ** Important part of absorption** - Have large volumes of fluid entering gut- somewhere around 10 L a day - Reabsorb all but about 100mL - Most reabsorption occurs in Small Intestine- 8-10 L - Amount that leaves Small Intestine is around 500 mL - Most solutes get absorbed through as well - Have active transport systems that actively absorb monosaccharides - Complete digestion of the food we eat and convert into small molecules and walls will absorb nutrients. - Most things left are not nutrients and things that can't be broken down. - The enzyme that causes breakdowns, normally have names that relate to what they breakdown. - There are small percentage of people that cannot breakdown lactose, so cannot be absorbed, so goes to large intestine, which adds fecal matter, causing diarrhea. Large Intestine (Colon) - We normally put in 500 mL and nondigestible materials (cellulose,non-digestcarbos) - Have a pretty good reabsorption of water; all but about 100mL - Cellulose will pass out as stool - Non-Digestible Carbos become food for bacteria, and when they eat, the release gases, or flatus - Average person produces about 1 L of flatus a day. - Has 2 Halves: 1.) Absorbing Colon- where most absorption takes place 2.) Storage Colon- stores contents - Rather few, maybe no peristaltic contractions - Instead, there are Mass Movements-constricted portion extends; very efficient way of pushing things from one end to another. Mass Movements-creating a high resistance pathway in reverse direction, so contents get pushed into Rectum. - Rectum then gets distended, which stimulates deification - The thing that stops deification is the External Anal Sphincter- skeletal muscle, means you have control over; you can inhibit deification. - Not every animal has an External Anal Sphincter.
