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Urinary System
University of Evansville EXSS113
60
Anatomy
Undergraduate 1
05/03/2010

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Term
Kidneys
Definition
Major excretory organs
Term
Urinary Bladder
Definition
temporary storage reservoir for urine
Term
Ureters
Definition
Transport urine from the kidneys to the bladder
Term
Urethra
Definition
Transports urine out of the body
Term
Kidney Functions
Definition
Removal of toxins& wastes
Blood volume regulation
Gluconeogenesis during prolonged fasting
Renin(blood pressure & kidney function)
Erythropoietin(RBC production)
Activation of Vit D
Term
Nephrons
Definition
Structural and functional units that form urine
Term
Glomerulus
Definition
a tuft of capillaries, part of the nephron
Term
Renal tubule
Definition
begins as cup-shaped glomerular (Bowman's) capsule surrounding the glomerulus
Term
Renal corpuscle
Definition
Glomerulus and its glomerular capsule, part of the nephron
Term
Fenestrated glomerular endothelium
Definition
Tissue of the nephron, fenestrated means it has pores
Term
Glomerular capsule
Definition
Has parietal layer, visceral layer. Visceral layer made of podocytes and filtration slits
Term
Podocytes
Definition
Have little extensions that come off them that end in foot processes or pedicles.
Term
Filtration slits
Definition
Space between the pedicles
Term
Proximal convoluted tubule (PCT)
Definition
part of the renal tubule, made of cuboidal cells with dense microvilli and large mitochondria. The microvilli serve to increase surface area
Term
Loop of Henle
Definition
With ascending (thick) and descending (thin) limbs
Term
Distal convoluted tubule (DCT)
Definition
Cuboidal cells with very few microvilli, function in secretion, not really reabsorption
Term
Collecting ducts
Definition
Receive filtrate from many nephrons, fuse together to deliver urine into minor calyces. Intercalated cells and principal cells
Term
Cortical nephrons
Definition
make up 85% of nephrons. Have short loops of Henle and glomerulus further from the corticomedullary junction
Term
Juxtamedullary nephrons
Definition
Long loops of Henle deeply invade the medulla
Term
Nephron capillary Beds
Definition
Glomerulus, peritubular capillaries, vasa recta
Term
Juxtaglomerular Apparatus (JGA)
Definition
Modified ascending loop of Henle and afferent arteriole.
Granular cells as mechanoreceptors to sense blood pressure
Macula densa as chemoreceptors to sense NaCl content
Extraglomerular mesangial cells connected by gap jctns
Term
Filtration Membrane
Definition
Between blood and capsular space, allows passage of water and solute smaller than most plasma proteins. Consists of fenestrated endothelium; visceral membrane of glomerular capsule; gel-like basement membrane
Term
Filtrate
Definition
Blood plasma minus proteins.
Term
Urine
Definition
Made up from less than 1% of total filtrate and contains metabolic wastes and unneeded substances
Term
Three major renal processes
Definition
Glomerular filtration
Tubular reabsorption
Tubular secretion
Term
Glomerular Filtration
Definition
Passive mechanical process driven by hydrostatic pressure.
The glomerulus is a very efficient filter
Term
Net Filtration Pressure
Definition
The pressure responsible for filtrate formation. Determined by Glomerular hydrostatic pressure.
Opposed by colloid osmotic pressure of glomerular blood and capsular hydrostatic pressure
Term
Glomerular Filtration Rate (GFR)
Definition
Volume of filtrate formed per minute by the kidneys. Governed by total surface area available for filtration, filtration membrane permeability and NFP
Term
Intrinsic Controls
Definition
Maintains a nearly constant GFR. Two types are myogenic mechanism and tubuloglomerular feedback mechanism
Term
Intrinsic Controls: Myogenic Mechanism
Definition
increased BP leads to constriction of afferent arterioles
decreased BP leads to dilation of afferent arterioles
Term
Intrinsic Controls: TUbuloglomerular Feedback mechanism
Definition
Flow-dependent mechanism directed by the macula densa cells. If GFR increases, filtrate flow increases in tubule and macula densa cells respond to increased NaCl by releasing vasoconstricting chemical
Term
Extrinsic Controls: Sympathetic Nervous System
Definition
Under normal conditions renal blood vessels are dilated
Under stress, norepinephrine is released by the SNS and epinephrine is released by the adrenal medulla
Term
Extrinsic controls: Renin-Angiotensin Mechanism
Definition
Triggered when the granular cells of the JGA release renin
Term
Effects of Angiotensin II
Definition
Constricts arteriolar smooth muscle, MAP rises
Stimulates the reabsorption of Na+
Stimulates hypothalamus to release ADH and activates thirst center
Increases fluid reabsorption
Decreases surface area available for filtration
Term
Tubular Reabsorption
Definition
Selective transepithelial process
Transcellular and Paracellular routes
Term
Transcellular route
Definition
1. Transport across laminal membrane
2. Diffusion through the cytosol
3. Transport across the basolateral membrane
4. Movement through the interstitial fluid and into capillary
Term
Paracellular route
Definition
Movement through leaky tight junctions particularly in the PCT
Term
Sodium Reabsorption
Definition
Na+ most abundant cation in filtrate. Primary active transport out of the tubule cell . Passes in through the luminal membrane by secondary active transport or facilitated diffusion mechanisms
Term
Reabsorption of Nutrients, Water, and Ions
Definition
Na+ reabsorption provides the energy and the means for reabsorbing other substances. Water is reabsorbed by osmosis, aided by aquaporins
Term
Reabsorption
Definition
1. At the basolateral membrane, Na+ is pumped into the interstitial space
2. Downhill Na+ entry at luminal membrane
3. Reabsorption of organic nutrients and certain ions by cotransport at the luminal membrane
4. Reabsorption of water by osmosis
5. Lipid-soluble substances diffuse by transcellular route
6. Cl-, K+ and urea diffuse by paracellular route
Term
PCT Reabsorption
Definition
Site of most reabsorption
Term
PCT Reabsorption
Definition
Site of most reabsorption
Term
Loop of Henle Reabsorption
Definition
Descending: H20
Ascending: Na+, K+, Cl-
Term
DCT and collecting duct reabsorption
Definition
hormonally regulated
Ca2+ (PTH), water (ADH), Na+(aldosterone and ANP)
Term
Mechanism of aldosterone
Definition
Targets collecting ducts and DCT
Promotes Synthesis of luminal Na+ and K+ channels
Promotes synthesis of basolateral Na+ K+ ATPases
Term
Tubular Secretion
Definition
Reabsorption in reverse. Solutes move from peritubular capillaries or tubule cells into filtrate
Controls blood pH by altering amounts of H+ or HCO3- in urine
Term
Osmolality
Definition
Regulates Urine Concentration and volume.
Number of solute particles in 1 kg of H20
Reflects ability to cause osmosis
Term
Osmolality of body fluids
Definition
Expressed in milliosmols.
Kidneys maintain osmolality of plasma at 300 mOsm, using countercurrent mechanisms
Term
Countercurrent mechanism
Definition
Occurs when fluid flows in opposite directions in two adjacent segments of the same tube. Establish and maintain an osmotic gradient from renal cortex through the medulla
Term
Countercurrent multiplier
Definition
1. The long loops of Henle of the justamedullary nephrons create the medullary osmotic gradient
2. The vasa recta preserve the medullary gradient while removing reabsorbed water and solutes
Term
Formation of Dilute Urine
Definition
absence of ADH
Term
Formation of Concentrated Urine
Definition
Maximum ADH
Term
Diuretics
Definition
Chemicals that enhance urinary output like osmotic diuretics, ADH inhibitors, and substances that inhibit Na+ reabsorption and obligatory H20 Reabsorption
Term
Renal Clearance
Definition
Volume of plasma cleared of a particular substance in a given time. Tests used to determine GFR, detect glomerular damage, follow the progress of renal disease
Term
Renal Clearance Formula
Definition
RC=UV/P
RC- renal clearance
U-concentration of the substance in urine
V- flow rate of urine formation
P- concentration of the same substance in plasma
Term
Layers of the bladder wall
Definition
1. Transitional epithelial mucosa
2. Thick detrusor muscle (3 layers of smooth muscle)
3. Fibrous adventitia
Term
3 areas of male urethra
Definition
1. Prostatic urethra (within prostate gland)
2. Membranous urethra (passes through the urogenital diaphragm)
3. Spongy urethra (passes through penis & opens via external urethral orifice
Term
Micturition= 3 simultaneous events
Definition
1. Contraction of detrusor muscle by ANS
2. Opening of internal urethral sphincter by ANS
3. Opening of external urethral sphincter by somatic nervous system
Term
Pontine control centers
Definition
1. Pontine storage center inhibits micturition
2. Pontine micturition center promotes micturition
Term
Neural control of micturition
Definition
1. Stretch receptors
2. Signals from parasympathetic fibers in pelvic nerve
3. Efferent signals excite detrusor muscle
4. Efferent signals relax internal urethral sphincter.
5. For voluntary control, pons receives signals from stretch receptors
6. If it is timely to pee, pons relaxes internal urethral sphincter
7. If untimely, pons keeps external sphincter contracted
8. If timely, signals from pons cease and external sphincter relaxes.
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