Urinary System Flashcards
What do kidneys produce?
urine via removal of metabolic wastes from circulation
What is the function of the ureters?
transport urine toward the urinary bladder
What is the function of the urinary bladder (muscular sac)?
Temporarily store urine prior to urination.
What is the function of the urethra?
Conducts urine to the exterior; in males, it also transports semen.
What is the primary function of the urinary system?
To remove most metabolic wastes produced by body’s cells
Urination/micturition
contraction of muscular urinary bladder forces urine through urethra and out of body
Three functions of the urinary system?
Excretion: removal of metabolic wastes from body fluids.
Elimination: discharge of wastes from body
Homeostatic regulation: of volume and solute concentration of blood.
How does a kidney receive blood?
through a renal artery.
Flow of blood to and away from the nephron:
Afferent arteriole > glomerulus > efferent arteriole > peritubular capillaries
The fibrous capsule
covers the surface of the kidney.
The perinephric fat
protects the kidney from damage
The renal pyramid helps to
with blood filtration and water concentration regulation within your kidneys
Renal nerves help with
innervating kidneys and ureters
enter each kidney at hilum
follow branches of renal arteries to individual nephrons
Nephrons are
microscopic functional units of kidneys
each consists of renal corpuscle and renal tubule
each renal tubule empties into collecting system
Bowman’s capsule
surrounds the glomerular capillary loops and participates in the filtration of blood from the glomerular capillaries.
Bowman’s capsule also has a structural function and creates a urinary space through which filtrate can enter the nephron and pass to the proximal convoluted tubule.
The function of the filtration slits is
to allow some exchange of materials, or “leaking”, from within the fenestrated capillaries of the glomerulus.
The Renal Tubule has two convoluted tubule
Proximal convoluted tubule (PCT)
Distal convoluted tubule (DCT)
What are the PCT and DCT separated by?
the loop of Henle: U-shaped tube + extends partially into medulla
While traveling along the renal tubule, the tubular fluid gradually changes in composition due to
substances being reabsorbed or secreted in various segments of nephron.
Function of the Juxtaglomerular complex (JGC) helps
regulate blood pressure and filtrate formation
What does the JGC consist of?
Macula dense
Juxtaglomerular cells
Extraglomerular mesangial cells
Macula dense contains
chemo and baro-receptors
Juxtaglomerular cells contains
modified smooth muscle cells
Extraglomerular mesangial cells provide
feedback between cells.
Cortical nephron
mainly perform excretory and regulatory functions
The Juxtamedullary nephron helps to do what with urine?
concentrate and dilute urine
Peritubular capillaries
filter waste from your blood so the waste can leave your body through urine
Vasa recta
bring nutrients and oxygen to the medullary nephron segments but, more importantly, they also remove the water and
solute that is continuously added to the medullary interstitium by these nephron segments.
Specialized capillaries in the kidney
What is the main difference between cortical juxtamedullary nephrons?
Cortical nephrons (85% of all nephrons) mainly perform excretory and regulatory functions, while juxtamedullary nephrons (15% of nephrons) concentrate and dilute urine.
What is the goal of urine production? How is this achieved?
to maintain homeostasis.
By regulating volume and composition of blood + excretion of metabolic wastes.
What are the three main metabolic wastes?
Urea: most abundant organic waste.
Creatinine: breakdown of creatine phosphate.
Uric acid: recycling of nitrogenous bases.
Organic wastes are eliminated by being completely
What is this removal accompanied by?
dissolved in the bloodstream
water loss
Functions of the kidney include:
concentrating filtration
reabsorption and retention of sugars and amino acids of valuable materials.
What are the basic processes of urine formation
Filtration
Reabsorption
Secretion
If blood pressure decreases in the glomerular capillaries
Intraglomerular mesangial cells contract; luminal diameter of glomerular capillaries- brings more pressure and increases filtration
If blood pressure increases in the glomerular capillaries
Smooth muscle cells of afferent arteriole contract -> limit blood flow into glomerulus
INCREASE GFR
Cortical and Juxta nephron loops are in the cortex, but differ in that:
the juxta nephron loop is located in the medulla (makes up 15% of nephrons)
What is the importance of the peritubular capillaries?
if we take back anything from the filtrate and help filter blood before having it go back into the venue.
Food going into the stomach
absorption
Food already in the body has elements taken out
reabsorption
What is significant about the fenestrated capillaries?
They have tiny openings to allow solutes to pass through.
Glomerular Filtration is driven by and involves passage across
hydrostatic pressure, filtration membrane
GHP
draws solutes out of the glomerulus - big pressure because afferent arteriole diameter is greater than the efferent arteriole diameter.
CsHP
in the capsular space, once filtrate is out the fluid goes back into the glomerulus
If GFR goes down
the solutes will build up and so will toxins
If GFR goes up
then we may be taking out what we may need
If BP decreases >
intraglomerular mesangial cells contract; luminal diameter of capillaries decreases- brings more pressure and increases filtration.
If BP increases >
smooth muscle cells of afferent arteriole contract -> limit blood flow into glomerulus
Hormonal regulation is initiated by the
kidneys
Autonomic regulation is initiated by the
sympathetic division of ANS
Renin is important in activating
inactive things, most notably angiotensin II
Angiotensin II
constricts arterioles and efferent arterioles
increases aldosterone secretion which increases NA retention which increases h2o retention
The homeostasis of GFR is differentiated between the increase/decrease of BP by
Decreased BP: Constricts arterioles and efferent arterioles, increased ADH production, increased sympathetic division, aldosterone secretion (maintaining blood volume).
Increased BP: Dilate afferent arterioles and constrict efferent arterioles (increases GHP) this increase in pressure will increase urine leaving and reduce blood pressure/volume (trying to get rid of blood volume)
The PCT absorbs how much of the filtrate? Is reabsorption highest here?
60-70%
Reabsorption is highest here.
The descending limb of the nephron loop is freely permeable to ____, but not _____
water, but not solutes
The ascending limb of the nephron loop is impermeable to ____ and passively and actively removes ____ from the tubular fluid. It is also very long in the juxta nephrons, creating ___
impermeable to water, passively and actively removes sodium and chloride ions, and high solute concentrations in peritubular fluid.
Obligatory water reabsorption occurs at ___ and
the PCT and absorbs most of the water.
facultative water reabsorption occurs at the ___ and only occurs if
collecting ducts and occurs if ADH is secreted.
When ADH is present, which of the following parts of the nephron and collecting system are affected?
DCT and collecting duct
Aldosterone helps retain
sodium
Countercurrent
exchange between fluids moving in opposite directions.
Multiplication
Effect of exchange increases as movement of fluid continues
Na and Cl are pumped out of the thick ascending limb leads to
elevated osmotic concentration in peritubular fluid around the descending thin limb
Water flows out of descending thin limb into peritubular fluid leads to
increasing solute concentration of tubular fluid in descending thin limb
Water is reabsorbed by osmosis in the
PCT and descending limb of nephron loop.
ADH increases
osmotic water movement
number of water channels
water permeability of DCT and collecting system
Without ADH
all fluid reaching DCT is lost in urine and large amounts of dilute urine are produced
Urine storage reflex
stimulating contraction of internal urethral sphincter
Pontine storage center
contracts/stimulates external urethral sphincter
The kidney is supplied by blood through
renal arteries
The nephrons are supplied by blood through
afferent arterioles
Juxtaglomerular cells secrete
renin
The PCT has ___ cells with ___ to help maximize surface area for absorption
cuboidal cells with microvilli
Glomerular (Bowman’s) capsule and the glomerulus make up the
renal corpuscle
The process that transports solutes, including many drugs, into the tubular fluid is called
secretion
Reabsorbed water and solutes enter into the
peritubular fluid
What best describes how the autonomic mechanism regulates for GFR?
Sympathetic fibers override local controls to decrease the GFR.
Effects of sympathetic activation:
altered regional blood flow
vasoconstriction of the afferent arteriole
renin release
