25) Urinary System: Flashcards
1-11 from quiz, 12-52 from lecture notes
part of the nephron responsible for the majority of secretion and reabsorption
proximal convoluted tubule
hormone that drives calcium reabsorption
parathyroid hormone (PTH)
antidiuretic hormone targets this to insert aquaporins
collecting duct
hormone responsible for the reabsorption of sodium and secretion of potassium
aldosterone
glomerulus and the glomerular capsule
renal corpuscle
part of the nephron involved in the countercurrent mechanism
nephron loop
the concept of actively absorbing sodium to passively absorb water
countercurrent mechanism
urination reflex
micturition
important in regulating the secretion of renin
juxtaglomerular apparatus
microscopic functional unit of the kidney
nephron
only reabsorption of water via osmosis takes place here
descending limb of nephron loop
urinary system
*maintaining composition, pH, and volume of body fluids
*removes metabolic waste and substances present in excess
organs of the urinary system
*kidneys
*ureters
*urinary bladder
*urethra
kidney
*lie on either side of vertebral column, in a depression on the posterior abdominal wall
*held in retroperitoneal position by parietal peritoneum (tough fibrous capsule)
*Left slightly higher than right kidney
kidney function
*remove urea and other waste products from metabolic activities
*regulate amount of water in the bood
*adjust concentrations of various substance (i.e. electrolytes) in blood
*controls RBC formation (secretes erythropoietin)
kidney structure
renal sinus
*hollow chambers of kidneys
*blood vessels, nerves, lymphatic tissue, and ureter pass through the hilum (entrance of the renal sinus)
renal pelvis
*located in the renal sinus, is the expanded, superior end of the ureter
*subdivided into the major and minor calyces (tubes) as it goes into the kidneys
renal medulla
*inner layer
*contains conical-shaped masses of tissue (renal pyramids)
*apexes of pyramids form renal papillae that extend into the minor calyces
renal cortex
*outer layer
*granular in apperance and forms the outher sufrace of the kidneys
*part of renal cortex seperates the renal pyramids and is know as renal columns
renal capsule
protective outer layer that helps maintain the shape of the kidneys
nephrons
*functional unit of the kidneys
*each kidney has 1 million nephrons
*site of urine production
*consists of renal corpuscle and renal tubules
renal blood vessels
*abdominal aorta> renal arteries> “segmented arteries”> interlobar>,arcuate arteries>, cortical radiate arteries>, afferent arterioles>glomerulus, efferent arterioles>peritubular capillaries
*from the nephron blood then travesl out of the kidney thru:
*cortical radiate vein> arcuate vein, interlobar vein, renal vein> inferior vena cava
structure of nephron
*renal corpuscle- coiled cluster of blood capillaries (glomerulus) and a saclike structure (glomerular capsule) that surrounds the glomerulus
*renal tubule- continues from glomerulus capsule, becomes coiled (proximal convoluted tubule)> (nephron loop), (distal convoluted tubule)> renal cortex> collecting ducts> renal pelvis
glomerulus & glomerular capsule
glomerulus: *coiled cluster of blood capillaries
*filters blood, first step of urine formation
glomerular capsule: *enlargement at end of renal tubule that receives filtrate from glomerulus
proximal convoluted tubule
*from glomerular capsule, continues and is very coiled
nephron loop
renal tubule straightens and makes a U-turn
distal convoluted tubule
*distal tubules merge in the renal cortex, form collecting duct (calyx) in the medulla
**
cortical nephrons
*85% of nephrons
*in the cortex of the kidney
*efferent arteriole supplies peritubular capillaries
juxtamedullary nephrons
*important in producing concentrated urine
*long nephron loops deeply invade medulla
*thick and thin segments
*efferent arteriole supplies casa recta
juxtaglomerular apparatus
*distal convoluted tubule passes between the afferent and efferent, is in contact with them
*surrounded by smooth muscle cells (juxtaglomerular cells)
*important in regulating and secretion of renin
*renin-regulates the renin=angiotensin system, increases blood pressure
urine formation (three steps)
*glomerular filtration
*tubular reabsorption
*tubular secretion
glomerular filtration
*hydrostatic pressure moves substances from the blood in the glomerulus to the glomerular capsule
*water and small dissolved molecules are filtered, larger molecules stay in the blood
*fenestrations increase permeability
*podocytes-filtration slits filter fluid
glomerular filtrate
fluid that has been filtered thru glomerulus
glomerular filtration rate (GFR)
*directly proportional to the net filtration pressure
*GFR of average adult= 125mL/min or 180L/day
*blood plasma filtered about 60 X/day
*small percentage of the filtrate is actually excreted as urine
control of filtration rate
*autoregulation
*sympathetic nervous system- keeps GFR constant by changing blood pressure conditions, causes afferent and efferent arteriols to constrict
*renin-angiotensin system- responds to a decrease in blood pressure
*ANP & BNP hormone control
Atrial Natriuretic Peptide (ANP) & Ventricular Natriuretic Peptide (BNP)
*ANP= secreted in response to > blood volume
*BNP= secreted in response to > blood pressure
*hormones inhibit the renin-angiotensin system by increasing sodium and water excretion from the kidneys
tubular reabsorption
*some glucose, water, minerals must be recycled back into body and are secretively reabsorbed from the glomerular filtrate
*moved by active transport
*most reabsorption in the proximal convoluted tubule
different types of transport for substance in tubules
active transport: *movement of substance against their concentration gradients
*transport limited due to number of carrier proteins
osmosis: *water reabsorption
endocytosis: *small protein reabsorption
sodium and water reabsorption
sodium and water reabsorption
*water reabsorption in proximal convoluted tubules by osmosis
*as sodium ions are actively reabsorbed, negatively charged ions (chlorine, bicarb, phosphate) are passively reabsorbed
*97-99% of glomerular filtrate is reabsorbed each day
tubular secretion
*substances move from the plasma of peritubular capillaries into renal tubules by active transport
*substances are wastes, to be excreted in the urine
*drugs like penicillin and histamine are actively secreted
*secretion of ions like potassium ions and hydrogen ions
regulation of urine concentration and volume
*distal convoluted tubules are impermeable to water in absence of ADH
*if ADH is present, segments become permeable (aquaporins) and water is reabsorbed by osmosis
*urine becomes concentrated because of ADH
countercurrent mechanism
*fluid flows in opposite directions in two adjacent segments of same tube with hairpin turn
*countercurrent multiplier & countercurrent exchanger
*work together to establish and maintain medullary osmotic gradient from renal cortex through medulla
countercurrent multiplier
*interaction of filtrate flow in ascending/descending limbs of nephron loops of juxtamedullary nephrons
*creates gradient
countercurrent exchanger
*blood flow in ascending/descending limbs of vasa recta
*preserves gradient
urea
*product of amino acid catabolism
*plasma concentration reflects the amount of protein in diet
urine composition
*95% water
*metabolic waste: urea, uric acid, creatinine
*trace amounts of amino acids and electrolytes
*0.6 - 2.5L/day: 50-60mL of urine output/hour is normal
elimination of urine
nephrons> collecting ducts> renal papillae> minor & major calyces> renal pelvis> ureters> urinary bladder> urethra> out of body
ureters
*muscular tubes carry urine from kidneys to bladder
*peristaltic contractions
*begin as funnel-shaped renal pelvis (3 layers): mucous coat (inner layer), muscular coat (middle layer), fibrous coat (outer layer)
urinary bladder
*hollow, muscular organ, expands as urine is collected
*trigon- triangular area at the floor of bladder has openings at 3 corners, two to the ureters, one to the urethra
*walls have four layers: mucous coat (inner layer), submucous coat (2nd layer), muscular coat-detrusor muscle (3rd layer), serous coat (outer layer)
urethra
*tube that takes urine from urinary bladder to outside the body
*in females, urethra is ~4cm long
*in males, urethra is ~20cm long
micturition
*urine leaves the bladder by micturition or urinary reflex
*as bladder distends, stretch receptors are stimulated
*micturition center activates in sacral portion of spinal cord
*parasympathetic nerve impulses cause detrusor muscles to contract
*external urethral sphincter- voluntary contraction and relaxation disallows/allows urination
