Chapter 17: Urinary System Flashcards
Outer region of the kidney
Renal Cortex
Inner region of the kidney
Renal Medulla
Drainage of each renal pyramid =
Renal pyramid -> Minor Calyx -> Major Calyx -> Renal Pelvis -> Ureter
Nephrolithiasis
Kidney Stones
- crystallized minerals (80% are calcium)
- at risk when dehydrated
- obstruct urine flow and painful to pass
Detrusor Muscles
Line the wall of the urinary bladder, have gap junctions to connect smooth muscle cells so that the bladder contracts in unison
What kind of neurons innervate the bladder? What do they release, on what kind of receptors?
Parasympathetic neurons, release acetylcholine onto muscarinic ACh receptors
2 sphincters surrounding the urethra: (and what type of muscle)
Internal urethral sphincter: smooth muscle
External urethral sphincter: skeletal muscle
Micturition
Urination
Control of Micturition
Information sent by stretch receptors in the bladder to the spinal cord
Guarding Reflex
Prevents involuntary emptying of the bladder
- neurons from stretch receptors to the spinal cord normally inhibit parasympathetic nerves to detrusor muscle, somatic motor neurons to the external urethral sphincter are stimulated (NO URINATION)
Voiding Reflex
Initiated by stretch of the bladder, info sent to up the spinal cord to the pons (micturition center)
- parasympathetic neurons cause contraction of detrusor muscles
- inhibition of sympathetic innervation to the internal urethral sphincter relaxes it
How does someone hold their bladder, when the stretch receptors signal that it is full?
By controlling their external urethral sphincter
Nephron
Functional unit of the kidney
- more than a million in each kidney
Filtrate
Fluid in the glomerular capsule
- water and solutes from the blood
Renal corpuscle
Glomerular (Bowman’s) Capsule and the glomerulus
Passage of fluid from renal arteries to bladder:
- Filtered into the glomerulus from the Bowman’s capsule (called FILTRATE)
- Into the proximal convoluted tubule
- Into the descending/ascending limbs of the Loop of Henle
- Into the distal convoluted tubule
- Into the collecting duct (now called URINE)
- Drain into a minor calyx->major calyx->renal pelvis->ureter->bladder
Type of capillaries in the glomerulus
Fenestrated
Layers that the filtrate must pass through in the glomerular corpuscle
Capillary fenestrae -> Glomerular basement membrane -> visceral layer (podocytes - have extensions called pedicles)
Net filtration pressure
Hydrostatic pressure of the blood + Colloid osmotic pressure
= ~10 mmHg
Glomerular Filtration Rate
GFR
- volume of filtrate produced by both kidneys each minute
= 115-125 mL = 180 L/day
- total blood volume is filtered every 40 min
GFR regulation
via vasoconstriction/dilation of afferent arterioles
- extrinsic and intrinsic regulation
Extrinsic GFR regulation
Via sympathetic nerves
- fight/flight = vasoconstriction of afferent arterioles = divert blood to heart/muscles = decreased urine formation to compensate for drop in BP
Renal autoregulation
Intrinsic GFR regulation
- maintained at a constant level even with great BP fluctuation
- dilate afferent arterioles if BP < 70 (increase flow)
- constrict afferent arterioles if BP > normal (decrease flow)
Myogenic constriction
smooth muscles in arterioles sense an increase in BP
- release Ca = contraction = sense
Tubuloglomerular feedback
Macula densa (cells in the DCT) sense rise in water + sodium when BP increases
- send ATP (Chemical signal) to constrict afferent arterioles (decrease flow to compensate high BP)
Reabsorption
return of filtered molecules to the blood from the filtrate (85% in the loop of Henle)
It is isoosmotic in the _________
in the glomerular capsule
- osmolarity of filtrate and blood plasma is equal
Countercurrent Multiplier System
Water will not move into the extracellular fluid if its isotonic
- so the loop of Henle (specifically the ascending portion) creates a concentration gradient to promote osmosis
- done by actively pumping salt into the interstitial fluid
Which limb of the loop of Henle is permeable to salt or water?
Ascending: permeable to salt, NOT WATER
Descending: permeable to water, NOT SALT
Vasa Recta
Specialized blood vessels around the loop of Henle that help create the countercurrent system (take in salts and loose them again)
Collecting Duct
Last point of water removal from urine, depends on the number of aquaporin channels = determined by ADH
Process of ADH and aquaporin formation
ADH binds to receptors on collecting duct cells -> cAMP -> Protein kinase -> aquaporin vesicles fuse to plasma membrane -> water is reabsorbed
Homeostasis of plasma osmolarity and ADH
Low osmolarity = less ADH = less water reabsorbed into blood = more urine
High osmolarity = more ADH = more water reabsorbed into blood = less urine
2 types of diabetes insipidus
- Central Di = inadequate secretion of ADH
- Nephrogenic Di = inability of kidneys to respond to ADH (caused by genetic defects in aquaporin channels or ADH receptors)
Reabsorption in the PCT
Active transport of Na+ (with Cl- following passively) from filtrate into the interstitial fluid causes osmosis of water to follow
- Apical side has tight junctions with microvilli, basal side has Na/K pumps to create a low [Na+] inside the cells
