Exam 5 Study Guide
Exam 5 Study Guide Biol 2230-001
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This 11 page Study Guide was uploaded by Madeline Notetaker on Friday April 22, 2016. The Study Guide belongs to Biol 2230-001 at Clemson University taught by Dr. John Cummings in Spring 2016. Since its upload, it has received 55 views. For similar materials see Human Anatomy & Physiology II in Biological Sciences at Clemson University.
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Date Created: 04/22/16
Urinary System Objectives Identify the components and the functions of the urinary system. Components • Kidneys (2): organ that filters blood • Ureters (2): extend from each kidney, drains to urinary bladder • Urinary bladder (1): storage tank for urine • Urethra (1): last part of system, the exit pathway Functions 1. Fluid filtration: primarily done by kidneys; filtering blood plasma through filtration membrane; goal is to take wastes out of circulation 2. Regulates blood volume: has a role in regulating blood pressure by determining how much water is lost as urine 3. Maintains salt/water balance: creating osmotic gradients, water follows sodium 4. Maintains acid/base balance: related to reabsorbing bicarbonate and excreting hydrogen ions 5. Gluconeogenesis: making new glucose from amino acids or fatty acids 6. Renin production: kidneys produce renin, a hormone that controls the kidneys 7. Erythropoietin production: hormone produced in kidneys that stimulates production of red blood cells in the bone marrow 8. Activates Vitamin D: by converting one thing to another in the kidneys Describe the structure of a kidney and its coverings. Structure • Capsule: thin outer layer, creates boundary, holds everything together • Cortex: outer section • Medulla: middle section • Pelvis: section that dumps into ureter • Pyramids: triangular shaped • Columns: space between pyramids, extensions of the cortex • Major calyces: a couple minor calyces that have merged • Minor calyces: comes from each pyramid *The kidneys are retroperitoneal, meaning they are not held in place by the peritoneum of abdominal cavity Coverings • Renal capsule: outer thin layer around kidney • Adipose capsule: fat is stored here, a blanket of fat for protection and insulation • Renal fascia: anchors kidneys List the similarities (meaning all the components) and differences between cortical and juxtamedullary nephrons, including the vasculature present. ***Nephron = the structural and functional unit of kidney • About 1 million per kidney ***Filtrate NOT the same as urine; NOT INTERCHANGEABLE Structure of a Nephron • Glomerulus: • special capillary bed in a nephron • exists between 2 arterioles • has highest blood pressure of all capillaries in body • Renal Tublule: • Glomerular (Bowman’s ) capsule: • tubule that surrounds glomerulus • collects the filtrate • Proximal convoluted tubule: • attaches to capsule • Loop of Henle: • attaches to PCT • Distal convoluted tubule: • attaches to loop of henle and connects to a collecting duct • Collecting ducts: • several renal tubules can connect to a single • give the pyramids their striped appearance • Renal corpuscle: glomerulus + glomerular capsule Vasculature of a Nephron • Afferent arteriole: • arrives at glomerulus, delivers blood here • Efferent arteriole: • takes blood away from glomerulus • Glomerulus • Peritubular capillaries: efferent arteriole turns into this, surrounds renal tubule • Vasa recta: a modified peritubular capillary that surrounds the loop of Henle in a juxtamedullary nephron CORTICAL NEPHRONS JUXTAMEDULLARY NEPHRONS 85% of nephrons Part of the loop of Henle extends into the majority of nephron is contained in medulla the cortex Makes more concentrated filtrate because it creates a higher concentration gradient, ** if we need more water/blood, we so takes more water back into blood. send blood to juxtamedullary nephrons Discuss the histology of the juxtaglomerular apparatus and the filtration membrane. Juxtaglomerular Apparatus: modified portion of distal convoluted tubule, comes in contact with afferent arteriole • JG cells: enlarged smooth muscle cells in arteriole. Mechanoreceptors that respond to amount of stretch in afferent arteriole. When activated, release renin • Macula densa cells: chemoreceptors that respond to concentration changes in filtrate. When activated, cause activation of JG cells Filtration Membrane (of the glomerulus). • Determines what can move out of glomerulus into the tubule • Fenestrated epithelium: porous, leaky, allows everything except for red blood cells to come out • Podocytes: cells on epithelium with cytoplasmic extensions that keep proteins from passing; creates little slits/openings • Basement membrane: limits what can leave glomerulus, also stops proteins Describe the process of urine formation. Include the role of pressure in controlling the rate of filtration. Compare the events that occur at the different portions of the nephron. Urine Formation Glomerular Filtration Tubular reabsorption Tubular secretion Occurs in glomerulus. =Taking back the stuff =Moving things from the Fluid is forced out and that we want from the bloodstream into the into Bowman’s capsule. tubule into bloodstream. tubule that we want to get Higher blood pressure Have peritubular rid of. arriving at glomerulus capillaries that run along Could happen if (afferent), get increased the tubule to reabsorb something didn’t get rate of filtration. things. filtered through Filtration does not *What is reabsorbed? glomerulus, or if we require energy Glucose, amino acids, accidently reabsorbed (passive)à uses pressure ions, water something we don’t want differences. Could be both active or to keep. Non-selective passive Predominately happens in membrane, except by Starts in the proximal proximal convoluted size. convoluted tubule, but tubule, but some could Pretty much everything continues along entire happen in collecting duct gets dumped out here length (even things we will want back) Identify factors that can affect renal filtration, and discuss the effects of each. • Filtration pressure o Glomerular hydrostatic pressure: § Pressure of fluid inside glomerulus Aka blood pressure § helps push things out of glomeruls § THE MOST IMPORTANT PRESSURE o Colloid osmotic pressure of intracapsular space: § Pressure created by large molecules inside capsule § Pulls things into capsule o Colloid osmotic pressure of glomerular blood: § Pressure created by large molecules in glomerulus § Pulls things into glomerulus o Capsular hydrostatic pressure: § Pressure of fluid in capsule § Pushes things out of capsule • Constriction and Dilation of afferent and efferent arterioles o RBF (renal blood flow) and GFR (glomerular filtration rate) o Afferent arteriole… § If constricted: RBF decreases, GFR decreases § If dilated: RBF increases, GFR increases o Efferent arteriole… § If constricted: RBF decreases, GFR increases § If dilated: RBF increases, GFR decreases Filtration Regulation: works to keep filtration rate relatively constant!! Mechanism 1. Myogenic Smooth muscle in afferent arteriole mechanism responds to stretch created by pressure. An Intrinsic increase in BP causes stretch, arteriole Mechanism constricts, less blood into glomerulus, (within decreased GFR. An increase in BP causes kidneys) decreased stretch, dilation of arteriole, so get an increased GFR. 2. Tubulogolmerular Controlled by macula densa cells in mechanism of juxtamedullar apparatus that respond to the autoregulation solute concentration in the distal convoluted tubule. If detect a decrease in solute concentration, get vasodilation of arteriole, increased RBF and increased GFR. If detect a high solute concentration, get constriction of arteriole, decreased RBF and GFR. 1. Neural controls * acts in times of stress Extrinsic activates sympathetic fibers in times of Mechanism stress, release norepinephrine which causes vasoconstriction, causes inc blood pressure and blood volumeà increase GFR 2. Hormonal *macula densa cells stimulate JG cells to mechanism produce renin Low blood pressure in afferent arteriole stimulates JG cells to release renin, renin causes adrenal cortex to release aldosterone which causes an inc in sodium reabsorption, water followsà increase in blood pressure and volume so an increase in GFR Other factors 1.Prostaglandins Local signaling molecules; cause vasodilation that counteracts hormonal mechanism 2. Nitric Oxide a vasodilator 3. Adenosine Vasoconstrictor in the kidney but vasodilator everywhere else 4. Endothelin blood vessel lining secretes this; a vasoconstrictor Tubular Reabsorption a. Begins immediately in the proximal convoluted tubule. b. Thing that are not reabsorbed= uric acid, urea c. Things that are reabsorbed= glucose, water, Na, u 1. Anything coming out of the tubule and back into the blood vessels must pass through three barriers: 1. Materials pass from lumen into the cell by crossing over the Luminal membrane 2. Materials then pass from the cell into the interstitial space by crossing over the basolateral membrane 3. Materials then pass from the interstitial space into the capillary by crossing over the endothelial membrane 2. Tight junctions prevent the fluids absorbed from lumen into one cell from moving into another tubular epithelial cell. 3. Reabsorption occurs passively and actively Actions of reabsorption and secretion by region of renal tubules 1. Proximal convoluted tubule a. Most active of all parts b. Some things that are reabsorbed here (and % reabsorbed)… i. Water and sodium (65%) ii. Glucose, amino acids, lactate (100%) iii. Bicarbonate (90%) 2. Descending limb loop of Henle a. Freely permeable to water 3. Ascending limb loop of Henle a. Impermeable to water + b. Na transported out which creates the gradient that draws water out of the descending limb of the loop. i. If something is done to change the sodium that is reabsorbed, the amount of water that leaves the descending limb is changed 4. Distal convoluted tubule and collecting tubule a. Continues the reabsorption process; amount of reabsorption that occurs is highly dependent on hormone action b. Both are usually impermeable to water but are affected by ADH i. ADH increases water reabsorption in these areas ii. ADH concentrates the urine Urine Production Objectives Explain the mechanics of a countercurrent mechanism, then describe how this mechanism creates and maintains the osmotic gradient in the medulla of the kidney. • Counter current mechanism o Referring to the counter “current” of flow of the renal tubule and the capillaries running next to them. o The currents are running in opposite directions so as to ensure that the gradients of particles of both are different at all times in the reabsorption process. • Counter current multiplier (in juxtamedullary nephrons) o Fluids in proximal convoluted tubule about osmotically equal to blood plasma o Descending limb freely permeable to water (drawn out by Na) and impermeable to solutes, becomes more and more concentrated the deeper it goes into the medulla o Ascending limb impermeable to water but selectively permeable to solutes; solutes that leave to interstitial space pulls water from the descending limb o Collecting ducts permeable to urea which also helps create the concentration gradient that makes water move • Counter current exchanger o Vasa recta freely permeable to water and salts Explain how we can alter the concentration of our urine. • Concentration of urine dependent on ADH secretion • Low ADH produces a dilute urine • ADH production increases water reabsorption from distal convoluted tubule and collecting duct Discuss the anatomical composition of the urinary bladder. Urinary bladder • Receives urine via ureter coming from each kidney • Smooth muscle storage tank (involuntary) • Trigone is the triangle between urethra and the two ureter orifices • Bladder has rugae that allow it to hold more volume without stretching (and triggering the release response) o Has an internal and external orifice § External one is voluntary, internal one is involuntary Differentiate male and female urethras. Male: longer, carries reproductive juice and urine Female: shorter, only carries urine Define micturition, and discuss its control. • Micturition: emptying the bladder o Urine accumulates in the bladder o Stretch receptors are activated o Activate voiding reflex; under conscious control § Parasympathetic stimulation contracts bladder and relaxes internal and external sphincters Fluid Balance Objectives • The body is made of 50-60 % water o Water makes things biologically active by putting it into solution o Our body’s percent composition of water can change due to: § Muscle mass § Age § Gender § Body Fat Identify the body’s fluid compartments. • Intracellular o In the cell § Stored as cytoplasm § The majority of water is in the cell • Extracellular o Outside the cell § As interstitial fluid between vessels and cells § In blood vessel as plasma Discuss the composition of body fluids, and explain the osmotic power of each. Composition of body fluids 1. Water: makes up most of the fluids 2. Non-electrolytes: can not dissociate in water; not responsible for osmotic gradient; not ionic a. Ex: glucose, lipids 3. Electrolytes: dissolve in water; makes a powerful osmotic gradient; ions; inorganic a. Ex: salts, acids/bases, proteins Electrolyte Composition • Electrolyte composition is different in different body regions • Blood plasma and interstitial fluid compositions are always pretty similar • Relationship between the extracellular and intracellular compositions: o When one is high, the other is low List the factors that control fluid exchanges, and differentiate the roles each plays in driving exchange between plasma and interstitial fluid; between interstitial and intracellular fluids. Fluid Movement • There is not direct movement between circulation and cells • Fluid must move: • First, between plasma and interstitial fluid • Primarily regulated by hydrostatic pressure • Then between interstitial fluid and intracellular fluid (cytoplasm) • Regulated mainly by osmotic pressure • Plasma membrane being selectively permeable leads to the creation of them List the routes by which water enters and leaves the body. Do the same for electrolytes and acids and bases. Water • If homeostasis is working properly, water intake = water output WATER INTAKE WATER OUTPUT Ingestion- fluids or food we put into Vaporization of breath body Urination Metabolic water- from breakdown of Elimination glucose; results in end product of Perspiration water Electrolytes ELECTROLYTE INTAKE ELECTROLYTE OUTPUT Ingestion Perspiration Metabolic production Elimination of feces Urination NOT by vaporization Also vomiting in extreme cases Acids/ Bases • Important because proteins such as enzymes operate at an optimum pH • pH of blood = 7.35-7.45 • pH of intracellular compartment= 7 • Most things we ingest are acidic • The higher the H+ concentration, the lower the pH Describe the mechanisms that regulate water input and output. Water input/ output regulation • Increase in plasma osmolality or decrease in blood volume promotes thirst • Decrease in extracellular fluid osmolality decreases ADH production o Body doesn’t reabsorb as much water because we have enough • Large decreases in blood pressure increase ADH production Describe the importance of ionic sodium in fluid and electrolyte balance in the body. Sodium Importance • Located mainly in the extracellular fluid compartment • Most important in establishing osmotic gradient o High sodium concentration in the extracellular fluid compartment causes water to move out of the cells and into the interstitial fluid Describe mechanisms involved in regulating sodium (and therefore water) balance. Sodium Regulation • Aldosterone o *most important mechanism o Increases sodium reabsorption o Stimulated by renin/angiotensin mechanism o Reduces urine output • Cardiovascular baroreceptors o Detect and respond to BP o If high BP, baroreceptors detect and send signal to brain to reduce sympathetic activityà vasodilation of afferent arterioles à inc filtration and • Atrial natriuretic peptide o Heart secretes ANP in response to stretch due to high BP, causes vasodilation à more filtration so more dilute urine • Estrogen o Causes an increase in sodium reabsorption and BP • Progesterone o Causes a decrease in sodium reabsorption and BP • Glucocorticoids o Produced in adrenal cortex as a stress response; increases sodium reabsorption and BP Distinguish between acidosis and alkalosis, both respiratory and metabolic. Sources of H+ • Dietary o Ingest • Metabolic o Produce from chemical reactions in body Acidosis Alkalosis pH is dropping Decrease in H+ ion too much H+ ions (CO2 acts as acid) Increase in pH- more basic Respiratory vs. Metabolic causes of Acidosis and Alkalosis • Respiratory Acidosis: if we slow down breathing, we can accumulate CO2 • Metabolic Acidosis: increased amount of other acid in blood • Respiratory Alkalosis: if we speed up breathing, we decrease CO2 in blood • Metabolic Alkalosis: decrease amount of other acid in blood List the three major chemical buffer systems and describe how they resist pH change. Chemical Buffering Systems Bicarbonate Bicarbonate is an ion that acts as a proton donor or acceptor. Temporarily takes acid/base out of a solution Phosphate In the intracellular fluid. Acts like bicarbonate- donates/accepts proton Proteins Amphoteric molecules- can act as acid or base Most effective buffer Temporary- doesn’t eliminate Describe the influence of the respiratory system an acid-base balance. Physiological Buffering System • Slower response than chemical buffers • More effective than chemical buffers RESPIRATORY MECHANISM o Changes in blood pH affect respiration rate § Increase in blood pH decreases respiration rate § Decrease in the blood pH increases respiration rate Describe how the kidneys regulate hydrogen and bicarbonate ion concentrations of the blood. Renal Buffering System • Eliminates all other acids except CO2 • 3 ways the renal mechanism can work, and all 3 are related to bicarbonate o Reabsorbing bicarbonate § Increase amount going into circulation o Bicarbonate synthesis § Create new bicarbonate o Bicarbonate excretion § Stays in tubule and leaves body if we have excess
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