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A&P 2 Urinary System
Urinary System, Fluid, Electrolyte, & Acid-Base Homeostasis
| Question | Answer |
|---|---|
| Urinary system organization | 2 kidneys, 2 ureters, 1 urinary bladder, and 1 urethra |
| Location of kidneys | retroperitoneal between the last thoracic & L-3 vertebrae; right is slightly lower due to liver position |
| Renal capsule | transparent fibrous membrane continuous with ureter |
| Adipose capsule | fatty tissue for protection and anchoring |
| Renal fascia | thin dense, irregular connective tissue to anchor kidney to abdominal wall |
| Nephroptosis | floating kidney |
| Renal hilus | deep fissure on the concave border through which urether leaves kidney and blood, lymph, & nerve supply enters the kidney |
| Renal sinus | cavity within the kidney where hilus enters |
| Renal cortex | superficial "rind-like" region extending medially to form renal columns |
| Renal medulla | darker inner-most region containing 8-18 renal pyramids |
| Papillary ducts | drainage area for nephron collecting tubules |
| Renal pelvis | single large cavity receiving urine from major calyces |
| nerve supply for kidneys | innervated by nerves from the sympathetic division of the autonomic nervous system |
| blood supply for kidneys | abdominal aorta branches into the R&L renal arteries receives 1200 mL blood/min |
| Nephron | functional unit of the kidney 1 million/kidney=85 miles |
| Renal corpuscle | lies in the renal cortex and is where plasma is filtered composed of glomerulus & Bowman's capsule |
| Glomerulus | special capillary network between the afferent & efferent arterioles; basement membrane blocks passage of blood cells & large plasma proteins |
| Bowman's capsule | epithelial cup surrounding glomerulus that forms a 3-layered filtration membrane |
| Renal tubule | lies in the renal cortex and extends into medulla |
| Function of renal tubule | passageway for the filtrate from Bowman's capsule; composed of proximal convoluted tubule (PCT), loop of Henle (descending & ascending), and distal convuleted tubule (DCT) |
| PCT cells | cuboidal cells with microvilli for increased surface area for reabsorption & secretion |
| Descending loop cells | simple squamous cells for osmosis & diffusion |
| Thick ascending loop | contains macula densa cells |
| Macula densa cells | special cells where loop touches afferent arteriole; monitor Na+ & Cl- levels in filtrate (incoming material) |
| Juxtaglomerular(JG)cells | special muscle cells in afferent arteriole that can constrict to regulate renal bp |
| Juxtaglomerular apparatus (JGA) | Macula densa & JG cells |
| DCT cells | contain special principal cells that respond to hormones ADH & aldosterone to help balance fluid, electrolytes, & water level |
| What is the secondary capillary system that surrounds each nephron? | peritubular (vasa recta) capillaries |
| What are the two types of nephrons? | Cortical & Juxtamedullary |
| Cortical nephron | glomerulus lies in outer region of renal cortex; short loop of Henle (80-85%) |
| Juxtamedullry nephron | Loop goes deep into medulla for urine concentration/dilution (15-20%) |
| What are the three basic processes performed by the nephrons while producing urine? | Filtration, reabsorption, & secretion |
| Glomerular filtration | bloop pressure forces water & dissolved plasma components (filtrate) through glomerulus & Bowman's capsule |
| What is the amount of glomerular filtration? | 180 L (48 gal)=125 cc/min filtrate enters yet only 1-2 L excreted/day (60X/d) |
| Why does so much material enter tubule system? | Glomerular capillaries are very thin,contain many fenestrations (pores), and are covered with mesangial cells Glomerular bp (hydrostatic pressure) forces fluid into Bowman's capsule |
| Tubular reabsorption | selective return of water & solutes to bloodstream; 99% of filtrates reabsorbed into secondary capillary bed (peritubular capillaries) |
| How does so much material get reabsorbed from the tubule system? | Plasma proteins DO NOT enter tubule system, their presence in the peritubular capillaries acts as a magnet to draw fluid back into bloodstream (oncotic pressure) |
| Tubular secretion | Movement of material from blood into filtrate Takes place via the peritubular capillaries Maintains plasma pH and for elimination of creatinine,NH3,H+,K+,Rx, misc |
| Urinary excretion | Final elimination of wastes, excess H2O, and electrolytes =glomerular filtration+tubular secretion-tubular reabsorption |
| Renal Plasma Clearance | Blood nitrogen ->Kidneys ->Urine |
| Layers of glomerular filtration from inner to outer | Endothelial fenestration, Basal lamina, and Slit membrane |
| How is renal function measured? | Measured as glomerular filtration rate (GFR) and dependent on constant blood flow to kidney |
| GFR | averages 105-125 mL filtrate/min and maintained at this rate over a 80-180 mmHG bp range |
| How is renal regulation achieved? | Renal autoregulation Neural regulation Hormonal regualtion |
| Renal autoregulation | intrinsic process for short-term regulation |
| Neural regualtion | during high activity level or with hemorrhage, sympathetic system nerves promote renal arteriole constriction to shunt blood back to heart and decrease GFR |
| Hormonal regulation | multi-system process for long-term regulation |
| regulation of urine concentration | affected by hormone levels & countercurrent flow |
| countercurrent flow | descending loop fluid flows next to but in opposite direction of fluid in ascending loop |
| Caffeine | blocks Na+ reabsorption |
| Alcohol | blocks secretion of ADH |
| Lasix | blocks Na+ reabsorption at different points along the tubule (esp in Loop region) |
| Urinalysis | analysis of volume, physical, chemical & microscopic properties of urine |
| Blood urea nitrogen (BUN) | measures how much urea is in blood increased urea=decreased GFR |
| Plasma creatinine | end product of skeletal muscle metabolism; produced at steady daily rate; almost completely removed from blood increased plasma creatinine=decreased GFR |
| Ureters | transport urine from renal pelvis via peristalsis & gravity (1-5 waves/min) |
| rugae | folds in mucosal lining of bladder that allow for increased surface area (volume) |
| max capacity of bladder | 700-800 mL |
| internal urethral sphincter | the smooth muscle layer of bladder responsible for internal involuntary control |
| external urethral sphincter | the smooth muscle layer of the bladder responsible for external voluntary control |
| urination | control of micturition |
| incontinence | lack of urinary control |
| urethra | terminal passageway for urine also duct for reproductive secretions in males 1.5 inches in females 6-8 inches in males |
| Total Body Water (TBW) | Body fluid/water and its dissolved solutes (electrolytes) |
| Average Total Body Water | Females=55% Males=60% |
| Intracellular fluid (ICF) | fluid located within cells; 2/3 TBW |
| Extracellular fluid (ECF) | fluid NOT located within cells; 1/3 TBW |
| ECF has 3 distinct locations in body | <20% plasma(intravascular(IV))-within blood vessels <80% interstitial(IF)-between cells <5% misc specialized fluids (third spaces) |
| Movement of fluids is primarily driven by? | Osmosis |
| Osmosis | movement of water and small dissolved molecules across a semi-permeable barrier |
| Sources of body fluid (water) gain | Ingested water - 2300 mL/day Metabolic water - 200 mL/day (krebs) |
| Sources of body fluid (water) loss | Kidney - 1500 mL/day via urine Skin - 600 mL/day via evaporation & perspiration Lungs - 300 mL/day via respiration GI tract - 100 mL/day via feces; also menstrual losses |
| Electrolyte | Substance that forms ions when dissolved in water |
| Ion | Charged atom (cation+;anion-);conduct weak electrical current; ie Na+,K+,Cl-,H+,HCO3- |
| Nonelectrolyte | Substance that does not ionize when dissolved in water due to strong covalent bonds holding molecule together; ie glucose, urea, proteins |
| Functions of electrolytes | a.Regulate movement of water(osmosis) between body compartments b.Help maintain acid-base balance c.Function as cofactors for certain enzymes d.Carry weak electrical current->action potential->neuromuscular activity |
| Functions of nonelectrolytes | a.Regulate movement of water between body compartments via oncotic pressure b. Nutrients or waste products of cellular metabolism |
| milliequivalents/liter(mEq/L) | Relates charges carried by ions; important for maintaining neutrality of body fluids |
| milliosmoles/liter(mOsm/L) | relates total number of particles in a solution; important for determining if H2O will move in/out of compartment |
| Exchange of fluids between IF and ICF occurs | across cell membranes via osmosis |
| Exchange between plasma(IV) and IF occurs | across capillary walls via: a.Vesicular transport b.Diffusion c.Filtration d.Reabsorption |
| Osmotic pressure(OP) | concentration of electrolytes in fluid |
| Vesicular transport(transcytosis) | endo & exocytosis of large molecules ie nutrients & hormones |
| Diffusion | direct movement across capillary walls based on concentration difference=osmotic pressure (OP) |
| Filtration(bulk flow) | movement from IV to IF driven by blood pressure=hydrostatic pressure(HP) |
| Reabsorption | movement of water from IF into IV driven by concentration of plasma nonelectrolytes=oncotic pressure(OCP) |
| Unequal movements of fluid across cell membranes or capillary walls can result in? | Edema |
| Edema | accumulation of fluid in IF due to decreased reabsorption into IV(plasma) |
| Ascites | Abdominal edema |
| What causes edema? | a.Increased Na+ intake->water retention=increased bp b.decreased fluid output by kidney=increased bp c.decreased circulation of fluid due to cardiac, blood, or lymph vessel problems d.decreased plasma protein(albumin)->decreased OCP=decreased PULL of m |
| Acidity is determined by what? | H+ |
| Alkalinity is determined by what? | OH- |
| ECF pH range | 7.35-7.45 |
| Removal of excess H+(or OH-) occurs via what three mechanisms? | a.Buffer Systems b.Respiration c.Kidney Excretion |
| What are the three types of buffer systems? | a.protein buffers b.phosphate buffers c.carbonic acid-bicarbonate buffer |
| Which buffer system is the most important? | carbonic acid-bicarbonate buffer |
| Buffer systems | instantly, but temporarily bind excess H+ to remove it from ECF, but NOT body; buffer="sponge" that converts strong acids/bases into weak acids/bases |
| Phosphate buffer | found in ICF & kidney cells |
| Carbonic acid-bicarbonate buffer | found in plasma & kidney cells |
| Respiration | rapid adjustment of pH via exhalation of H2CO3=volatile acid |
| Kidney excretion | slow adjustment of pH via secretion of nonvolitile(fixed) acids into urine and reabsorption of HCO3- by kidney |
| Acidosis | blood pH <7.35 s/s-depression of CNS |
| Alkalosis | blood pH >7.45 s/s-overexcitability of CNS |
| Compensation | physiological response to acid-base imbalance that attempts to restore the body to homeostasis |
| How much TBW do infants have? | 75-90% (most is in ECF) |
| How much TBW do the elderly have? | 50% |
| Urine leaves the urinary bladder through the | Urethra |
| Which of the following structures are found in the renal cortex? | Distal convoluted tubules |
| Fenestrations are associated with the | Glomerulus |
| Urine contains | Waste products of metabolism |
| The renal pelvis | Drains into the ureter |
| The kidneys help control blood pressure by the secretion of | Renin |
| Sodium is moved out of the cells of the proximal convoluted tubule and into the interstitial fluid by the process of | Active transport |
| The outer layer of the three layers of tissue that surround the kidney is the | Renal fascia |
| In renal interstitial fluid | Sodium chloride concentration increases from cortex to medulla |
| Filtration of blood | Occurs in glomerulus |
| The loop of Henle is associated with | Reabsorption |
| A function of the kidney is to | Regulate blood ionic composition |
| Which of the following molecules cannot pass the filtration membranes in the kidney? | Large proteins |
| The innermost layer of the three layers of tissue that protect the kidney is the | Renal capsule |
| The renal papillae contain papillary ducts which empty into the | Minor calyces |
| Reabsorption is the movement of molecules from the_________into the________. | renal tubules, peritubular capillaries |
| Very little water reabsorption occurs in the | thick ascending loop of Henle |
| Sodium ions move through the apical membranes of principal cells of the collecting duct by | Diffusion |
| Glomerular filtrate is produced as a result of | blood hydrostatic pressure |
| The external opening of the urinary system is the | external urethral orifice |
| The kidneys secrete the hormone erythropoietin, which functions to | control the rate of red blood cell production |
| The pathway of fluid through a juxtamedullary nephron | proximal convoluted tubule, descending loop of Henle, ascending loop of Henle, distal convoluted tubule |
| Urine reaches the urinary bladder through the | ureter |
| The nephron has two parts. What are they? | renal corpuscle and renal tubule |
| The visceral layer of Bowman's capsule is covered with specialized cells called | podocytes |
| Increased sodium and chloride ion concentrations in the interstitial fluid of the renal medulla is the result of | countercurrent mechanism |
| Externally, the kidney is protected and supported by connective tissue and | adipose tissue |
| Renal blood pressure remains fairly constant due to the function of the | juxtaglomerular apparatus |
| Chloride ions are actively reabsorbed from the | thick ascending limb of the loop of Henle |
| Potassium ions are actively secreted in the tubular fluid of the | distal convoluted tubule |
| Most reabsorption occures in the | proximal convoluted tubule |
| The proximal convoluted tubule is made up of | cuboidal cells with many microvilli |
| Net filtration pressure in the kidney | 10 mm Hg |
| Enzyme secreted by the juxtaglomerular apparatus | Renin |
| The main region of the kidney tubule that is impermeable to water is the | thick ascending limb of the loop of Henle |
| During the micturition reflex_________. | parasympathetic fibers conduct impulses from the spinal cord that cause contraction of the detrusor muscle |
| The only place in the kidney where filtration occurs is the | renal corpuscle |
| The urinary bladder in the female lies inferior to the | uterus |
| Bone, DNA, RNA, ATP, and cell membranes all have one thing in common. They all contain_________. | Phosphate |
| Intracellular fluid has | A higher concentration of potassium than interstitial fluid |
| Parathyroid hormone | Causes renal tubule cells to reabsorb calcium |
| Lower than normal blood concentration of sodium | Characterized by muscular weakness, tachycardia, and dizziness |
| Regulated by aldosterone | Sodium |
| Electrolytes | Dissociate into anions and cations |
| Sodium Ions | Necessary for generation of action potentials |
| Reabsorption of sodium from the tubules of the nephron establishes an osmotic gradient that causes______to move back into the blood. | Water |
| Hyperventilation during a panic attack causes an increase in blood_______. | pH |
| The only way the body can get rid of the huge acid load produced by metabolic reactions is to | excrete hydrogen ions in the urine |
| The urinary bladder in the male lies anterior to the | Rectum |
Created by:
jarushing
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