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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 |