chapter 26: urinary system Flashcards
the kidney can assist the liver during starvation by performing what, the creation of glucose from non-carbohydrate molecules?
gluconeogenesis
what is the layer of collagen that functions to keep the kidney anchored to the body wall?
renal fascia
the renal medulla consists of many what?
renal pyramids
most of the renal sinus is taken up by what, which funnels urine into the ureters?
renal pelvis
inflammation of the kidney from an untreated UTI is called what?
pyelonephritis
cortical nephrons have a shorter what than juxtamedullary nephrons?
nephron loop
the glomerulus is covered with what visceral epithelium cells are called that intertwine to create filtration slits?
podocytes
the part of the renal tubule that is composed of cuboidal epithelium with microvilli is what?
proximal convoluted tubule (PCT)
what does secretion mean in the context of the distal convoluted tubule?
removal of wastes from the peritubular capillaries into the filtrate
The juxtaglomerular apparatus consists of what endocrine cells of the DCT & juxtaglomerular cells from the afferent arteriole?
macula densa
the JGA produces two regulatory substances: renin and what else?
erythropoietin
what molecule supplies the normal yellow color of the urine?
urobilin
of the total filtrate produced by the glomeruli, what percent is reabsorbed by the
renal tubule before urine exits the papillary ducts?
99%
as blood pressure declines, what happens to the GFR?
GFR declines
what is the main function of the nephron loop?
water reabsorption, ability to concentrate the urine
when aldosterone is present how will the DCT respond?
return sodium to the blood & discard potassium into the filtrate
how can the DCT assist in regulating blood pH?
optimal removal of H+ to reduce acidity
what triggers the insertion of aquaporin proteins into the cells of the DCT?
ADH
how can alcohol consumption lead to dehydration?
alcohol inhibits ADH, ADH allows for concentration of filtrate to reduce loss of water
what epithelium lines the ureters & urniary bladder?
transitional
the three layers of smooth muscle in the wall of the urinary bladder are
collectively what muscle?
detrusor
what’s the outermost layer of the urinary bladder which
anchors it to the pelvic floor?
adventitia
what’s reflex controls the timing of urination?
micturition
what is the inability to voluntarily control urine excretion?
incontinence
urinary retention in men is a result of what?
enlarged prostate
urinary system components/ urinary tract
-kidneys
-ureters
-urinary bladder
-urethra
excretions (function of the urinary system)
kidney
-removes organic wastes from blood
elimination (function of the urinary system)
urinary tract
-discharge wastes to enviroment
regulation of plasma volume & solute concentration (function of the urinary system)
kidney
-blood volume
-conc. of ions
-stabilize blood pH
-conserve nutrients
-assist liver: deamination, detoxification
what are other kidney functions?
a. gluconeogenesis during starvation
b. produce renin (regulate BP)
c. produce erythropoietin (RBC production)
d. convert VitD to calcitrol (Ca++ absorption in GI)
kidney
1% of body weight
-retroperitoneal, posterior abdominal wall
-adrenal gland anchored superior
-3 layers of CT anchoring: renal & adipose capsule, renal fascia
-has 2 layers: cortex & medulla
renal capsule(kidneys)
collagen fibers covering organ
adipose capsule(kidneys)
adipose cushion around renal capsule
renal fascia (kidneys)
collagen fiber fused to renal capsule and deep fascia of body wall & peritoneum
renal ptosis
floating kidney
-starvation or injury, kidney loose from body wall, could twist blood vessels or ureters
hilum of the kidney
-where renal arteries, renal veins, ureters enter/exit
-opens to renal sinus
renal sinus
lined with renal capsules, contiguous with outside
cortex (kidney)
superficial, contact renal capsule, houses filtration structure (nephrons)
medulla (kidney)
6-18 renal pyramids, parallel bundles of collection tubules
papilla (kidney)
apex of medulla points toward renal sinus
renal lobe
-divides kidney into sections
-renal pyramid + surrounding cortex or renal columns
-lobe is complete site of urine production
urine production:
nephron (cortex) -> collecting ducts (medulla) -> papilla -> minor calyx -> major calyx -> renal pelvis
renal pelvis
fill majority of renal sinus. funnels urine into ureter
pyelonephritis
inflammation of kidney, infection usually enters from ureter & spreads up through ducts to nephron
blood supply & innervation to kidney:
-receives 20-25% cardiac output
-highly vascularized, many capillaries (nephrons)
-innervation from renal plexus controlled by ANS
when is innervation of the kidney sympathetic?
- adjust rate of urine formation (change BP & flow at nephron)
- stimulate release of renin (restricts water & Na+ loss at nephron)
nephron
-smallest functional unit of kidney
-more than 1 million per kidney
-two important capillary beds: glomerulus & pertitubular
-two major parts: renal corpuscle & tubule
renal corpuscle (nephron -> kidney)
glomerular capsule + glomerulus
renal tubule (nephron -> kidney)
proximal convoluted tubule (PCT) + nephron loop + distal convoluted tubule (DCT)
glomerulus (nephron -> kidney
capillary bed associated with nephron
-filtration
-connected to arterioles: afferent -> capillary -> efferent
peritubular capillaries (nephron-> kidney)
capillary bed associated with nephron
-reclaim filtrate, concentrate urine
-connected to arterioles: afferent -> capillary -> efferent
cortical nephron
majority nephron, in cortex, short nephron loops
juxtamedullary nephron
15% of nephrons, at cortex/medulla interface, long nephron loops, important for water conservation & concentrated urine
renal corpuscle (nephron -> kidney)
-site of filtration
-2 parts: glomerular capsule & glomerulus
glomerular capsule (renal corpuscle -> nephron -> kidney)
thin parietal epithelium forms capsule around glomerulus
glomerulus (renal corpuscle -> nephron -> kidney)
fenestrated capillaries covered by podocytes
podocytes (glomerulus -> renal corpuscle -> nephron -> kidney)
visceral epithelium, intertwine to create filtration slits on surface of capillaries, slits smaller than fenestrations in glomerular capillaries to restrict filtration of large molecules
glomerulonephritis
inflammation of glomeruli prevents filtration, can be result of antigen/Ab complexes trapped in filtration slits following allergy or blood infection
renal tubule(nephron -> kidney)
-reabsorption to process raw filtrate into urine
-3 parts: PCT, nephron loop & DCT
proximal convoluted tubule (PCT) (renal tubule -> nephron -> kidney)
simple cuboidal epithelium with microvilli, reabsorbs organic nutrients, ions, water & salt plasma proteins from filtrate exiting glomerular capsule
nephron loop (renal tubule -> nephron -> kidney)
simple squamous epithelium, reabsorbs Na+, Cl- & H2O from filtrate, important to regulate volume & solute conc. of urine, has descending & ascending limbs
distal convoluted tubule (DCT) (renal tubule -> nephron -> kidney)
simple cuboidal epithelium, flat surface, has four important functions
functions of DCT (renal tubule -> nephron -> kidney)
- secretion: removal of wastes from peritubular capillaries into filtrate
- reabsorb Na+ & Ca2+ from filtrate
- optional H2O reabsorption from filtrate under hormonal control
- formation of juxtaglomerular apparutus
juxtaglomerular apparutus (JGA)
-consists of two cells
1. endocrine cells of DCT = macula dense
2. granular cells of afferent arteriole = juxtaglomerular cells
renin
-monitored & produced by JGA cells
-enzyme, restricts Na+ & H2O at nephron
erythropoietin
-monitored & produced by JGA cells
-hormone stimulates RBC production
collecting system of urine:
-collecting ducts + papillary ducts nephrons -> 1 collecting duct (renal pyramid) many collecting ducts -> papillary duct
final osmotic concentration of filtrate adjusted by collecting duct, after urine is complete & exits kidney:
papillary duct (renal papilla) -> minor calyx -> major calyx -> renal pelvis -> ureter
polycystic kidney disease
genetic, cysts form that cause swelling of kidney tubules; compression reduces function
renal physiology
urinary system functions to regulate blood volume and conc. removes wastes & produce urine
filtrate
everything in blood plasma except large proteins & cells
urine
metabolic waste, 1% filtrate
urea (common waste in urine)
from catabolism of amino acids
creatinine (common waste in urine)
from catabolism or damage of skeletal muscle tissue (creatine phosphate is energy storage of muscle)
uric acid (common waste in urine)
from recycling of RNA
urobilin (common waste in urine)
from breakdown of hemoglobin (yellow color)
dialysis
blood filtering machine, used for patients with kidney failure
glomerular filtration (urine formation)
blood hydrostatic pressure forces water & solutes through glomerular wall
tubular reabsorption (urine formation)
selective uptake of water & solutes from filtrate
tubular secretion (urine formation)
transport of wastes from capillaries to tubules
glomerular filtration process:
-occurs through filtration membrane
-filtration is passive but all small solutes escape (glucose)
1. fenestrated endothelium of glomerular capillaries (restrict cells)
2. podocytes restrict solutes protein sized & larger
3. fused basal laminate for both
glomerular filtration depends on:
- large surface area
- high glomerular BP
- good permeability
glomerular filtration rate (GFR)
amount of filtrate kidneys produce/minute
~125ml/min -> 180L/day
-99% reabsorbed, 1% lost as urine
-drop in BP = ↓ GFR (↓ 15% BP = 0 GFR)
autoregulation (regulation of GFR)
functions to maintain constant GFR with abnormal BP fluctuation in systemic arteriole
reduce blood flow/BP triggers (autoregulation -> regulation of GFR):
-dilation of afferent arteriole
-dilation of glomerular capillaries
-constriction of efferent arteriole
all functions to ↑ pressure at glomerulus to ↑ GFR
high blood flow/ BP triggers (autoregulation -> regulation of GFR):
-constriction of afferent arteriole
-constriction of glomerular capillaries
-dilation of efferent arteriole
all function to ↓ pressure at the glomerulus to ↓ GFR
hormonal regulation (regulation of GFR)
extrinsic regulation aimed at maintain systemic blood pressure
renin released by JGA in response to (hormonal regulation -> regulation of GFR):
-decline in BP at kidney
-decline in osmotic concentration of filtrate
-direct sympathetic stimulation
renin activates angiotensin in blood to form angiotensin II, which triggers (hormonal regulation -> regulation of GFR):
-arteriole constriction to elevate BP
-secretion of aldosterone from adrenal glands (aldosterone promotes sodium reabsorption in kidney tubules)
-thirst
-release of ADH from pituitary (ADH promotes water uptake in tubules)
effect of renin (hormonal regulation -> regulation of GFR):
↑ blood volume, ↓ urine production (conservation of water)
natriuretic peptides (hormonal regulation -> regulation of GFR):
hormones released in response to stretching in heart or aorta (↑ blood volume)
natriuretic peptide triggers (hormonal regulation -> regulation of GFR):
dilation of afferent arteriole, constriction of efferent arteriole
effect of natriuretic peptide (hormonal regulation -> regulation of GFR):
↑ GFR, ↑ urine production, ↓ blood volume
autonomic nervous system (regulation of GFR):
sympathetic causes vasoconstriction = ↓ GFR, ↓ urine production
-prolonged sympathetic stimulation can cause hypoxia of kidneys & water accumulation in blood
tubular reabsorption process:
-transport proteins in renal tubule cells return substances from filtrate to plasma
-when carrier proteins are saturated by substance they carry (max. velocity) renal threshold for that substance has been reached, additional amounts of substance will be lost in urine
glycosuria
glucose in urine: glucose levels in blood/filtrate exceed renal threshold
PCT reabsorption (tubular reabsorption)
- PCT reabsorbs 60-70% of filtrate
1. reabsorption of 99% of organic nutrients by facilitated diffusion & cotransport
2. passive reabsorption of ions by diffusion
3. selective reabsorption of ions by active transport (ion pumps controlled by hormones)
4. reabsorption of water by osmosis
nephron loop reabsorption (tubular reabsorption)
-functions to concentrate filtrate
-reabsorbs half remaining water & 2/3 Na+ & Cl- by countercurrent multiplication: ascending limb pumps ions from filtrate to medulla, high ion conc. then causes water to move by osmosis out of descending limb
DCT reabsorption (tubular reabsorption)
-aldosterone promotes Na+ uptake & K+ loss via sodium-potassium pump
-parathyroid hormone & calcitriol promote Ca2+ uptake
-ADH stimulates water uptake
tubular secretion
-selectively removes solutes from blood, delivers them to filtrate
-secretion carried out mostly by DCT, but some also occurs in collecting ducts
tubular secretion process:
- dispose of drugs & wastes that weren’t filtred
- eliminate wastes that were reabsorbed
- rid body of excess K+
- control blood pH: remove H+ CO2 + H2O <-> H2CO3 <-> H+ + HCO3-
-bicarbonate ions used to buffer blood pH but H+ must be secreted into filtrate
control of water volume in urinary system
obligatory water reabsorption occurs by osmosis in PCT & descending nephron loop (cannot be prevented)
facultative water reabsorption can occur in DCT & collecting ducts (impermeable) (control of water volume in urinary system):
ADH causes formation of water channels by triggering insertion of aquaporin
aquaporins
-proteins in cell membranes of DCT & collecting duct cells
-allow more osmosis to concentrate urine & conserve water
diuretics
substances that causes water loss
osmotic diuretics
substances that can’t be reabsorbed and thus take water with them
hypertension & edema meds
prevent Na+ uptake (water follows salt)
alcohol in urinary sytem
inhibits ADH, preventing facultative water reabsorption
diabetes insipidus
not enough ADH, produces large quantities of dilated urine, up to 24 L/day (1.2L normal)
anuria
low urinary output, less than 150ml/day, usually due to events that block filtration (nephritis, immune reactions, crushing injuries)
urine transport, storage & elimination
-urine production & modification: renal tubules & collecting system
-once in renal pelvis, urine complete, excreted via ureters, bladder, urethra
nephrolithiasis
blockage of urinary passage
ex: calculi (kidney stone)
calculi (kidney stone)
crystallized deposits of calcium, magnesium, or uric acid form in renal pelvis & can become lodged in ureters
-large ones disrupted by lithotripter
ureters
-connect renal pelvis to urinary bladder
-wall layers:
1. mucosa with transitional epithelium
2. muscularis with 2 layers of smooth muscle
3. adventitia: attaches to posterior body wall
-contractions occur every 30sec to force urine toward bladder
urinary bladder
-wall folded into rugae when empty (expands)
-wall layers:
1. mucosa with transitional epithelium
2. muscularis with 3 layers of smooth muscle
3. adventitia: fibrous, anchors bladder to pelvic floor
detrusor muscle (urinary bladder)
-contraction causes expulsion of urine from bladder
-thickened around urethral opening to create the internal urethral sphincter (involuntary control over release of urine)
urethra
-single tube, connects bladder to environment
-lined with pseudostratified columnar epithelium
-passes through band of skeletal muscle that forms external urethral sphincter under voluntary control, relaxation results in micturition
micturition (urination) reflex
-when bladder contains ~200ml urine, stretch receptors triggered, signal conscious awareness of pressure & stimulate contraction of detrusor muscle
-voluntary maintenance of contracted external urethral sphincter prevents urination, detrusor will relax
- continued increase in urinary volume will repeatedly trigger reflex
what happens when the urinary volume in the bladder exceeds ~500ml?
forced relaxation of internal & external urethral sphincters will result in non-voluntary urination/ micturition
incontinence
inability to voluntarily control urine excretion, due to: loss of muscle tone, damage to sphincters, damage to nerves or control centers in brain
age-related changes for urinary system
- ↓ functional nephrons
- ↓ GFR (damage or ↓ blood flow)
- ↓ sensitivity to ADH = dilute hormone
- ↑ incontience
- ↑ urinary retention (enlarged prostate)
