urinary system Flashcards
what are the major structures in the urinary system
2 kidneys
2 ureters
bladder
urethra
what are the functions of the urinary system
filter blood plasma (conc of ions and remove toxins)
conserves valuable nutrients (prevent loss thru urine)
regulates blood volume and pressure (decrease fluid > decrease blood vol > decrease BP)
regulates blood pH and glucose levels (remove H+ and glucose > maintain homeostasis)
release hormones (erythropoietin and calcitriol)
describe the anatomical position of the kidneys
either side of vertebral column
left slightly superior to right
retroperitoneal
protected by 11th and 12th ribs
what are the 4 structures going in/out of the kidney
renal artery
renal vein
hilum
ureter
what are the 3 CT layers around the kidney
fibrous capsule = collagen fibres
perirenal fat = cushioning layer of adipose tissue
renal fascia = fibrous layer that anchors kidney to surrounding structures
what is the renal cortex
outermost 1cm of the kidney
where filtration and reabsorption occurs
what is the renal medulla
2-3cm below the cortex
regulate concentration of urine
what is the renal sinus
central cavity that contains renal pelvis, renal calyces, blood vessels and fat
what are renal pyramids
in the medulla
extends from cortex to the renal sinus
transport urine from cortex to sinus
apex = renal papilla
what are renal columns
in the medulla
bands of tissue that separate adjacent renal pyramids
what are kidney lobes
in the medulla
they are functional units > where urine is produced
consist of renal pyramid, overlying renal cortex, and adjacent tissues of the renal columns
how is filtrate drained into the sinus
renal papilla >
minor calyces (collects urine produced by a single kidney lobe) >
major calyces (fusion of 4-5 minor calyces / collects urine from minor calyces >
renal pelvis (continuous w ureter) >
ureter (drains urine from kidney to bladder using peristaltic waves)
what are ureters
muscular tubes that go from the kidneys to the posterior wall of the bladder
sit retroperitoneal and are firmly attached to the posterior abdominal wall
what are the histological layers of the ureters
muscosa > transitional epithelium ie urothelium > expansion of ureter
muscularis > peristalsis / upper 2/3 has 2 layers of smooth muscle and bottom 1/3 has 3 layers of smooth muscle
what are the histological layers of the bladder
mucosa > urothelium + rugae > expansion
muscularis > expulsion of urine / 3 layers of smooth muscle
sphincters > bands of skeletal muscle that control urine flow, like valves
what are the 2 sphincters in the bladder
internal urethral (involuntary)
external urethral (voluntary)
what does the urethra do
transport urine from bladder to exterior of body
females = urine only
males = urine + semen
what are the histological layers of the urethra
mucosa > proximal = stratified transitional epithelium / middle = stratified columnar / distal = stratified squamous
muscularis > expulsion of urine / 2 layers of smooth muscle
what do the kidneys do
produce urine
what do the ureters do
carry urine from kidney to bladder
what does the bladder do
receives and stores urine
how does blood flow in the kidney
- O2 rich blood via renal artery
- renal artery divides into segmental arteries in renal sinus
- segmental arteries branch into interlobar arteries in renal columns
- interlobar arteries branch into small vessels > culminate in afferent arterioles that supply each nephron > blood enter glomerulus
- efferent arteriole carries blood from glomerulus to peritubular capillaries
- peritubular capillaries surround renal tubule
- peritubular capillaries drain into cortical veins > filtered back to IVC
what is a nephron
functional units of the kidney
what are the two types of nephrons
cortical - renal cortex / excrete waste product
juxtamedullary - long nephron loops in renal medulla / produce concentrated urine
what are the three main components of the nephron
renal corpuscle
renal tubule
collecting system
what does the renal corpuscle do
site of blood filtration
what does the renal tubule do
site of filtrate modification
what does the collecting system do
urine from each nephron empties into collecting system and then into minor calyces
what are the 3 distinct physiological process kidneys use to maintain homeostasis
filtration
reabsorption
secretion
what does the filtration structure in the renal corpuscle consist of
glomerulus (afferent and efferent arterioles)
glomerular capsule/bowmans capsule
why do efferent arterioles have a smaller diameter than afferent
increase the glomerular pressure which is needed as a driver for filtration to occur as it forces water and solutes out of glomerular capillaries into renal tubule
how does filtrate from the blood get filtered and passed onto the glomerulus capsule from the glomerulus
through a filtration membrane
filtrate move into capsular space while non filterable components exit glomerulus via efferent arteriole
what is the filtration membrane comprised of
fenestrated endothelium - stops cells and platelets
basement membrane - stops large proteins
filtration slits b/w pedicels (processes from podocytes) - stops medium sized proteins
what enhances filtration
thinness of filtration membrane
large SA of glomerular capillaries
higher glomerular BP
what is glomerular filtration rate (eGFR)
based on creatinine levels > gives estimation on kidney function
> GFR90 is normal
GFR 60-90 = CKD1
what are mesangial cells
b/w adjacent capillaries
contract and relax to control capillary diameter and blood flow rate
phagocytosis to keep glomerular filter free of debris
what are the three main parts of the renal tubule
proximal convoluted tubule (PCT)
loop of henle
distal convoluted tubule (DCT)
what is the function and structure of the PCT
reabsorbs most of filtrate (e.g glucose and small proteins)
has microvilli to increase SA, mitochondria for active transport, centrally located nucleus and pink appearance
what is the function and structure of loop of henle
urine concentration
descending limb
thin ascending limb
thick ascending limb
has vasa recta
how does the countercurrent multiplier mechanism work in the loop of henle
descending limb is permeable to water > water leaves descending limb into ISF of medulla
this causes a conc gradient to be established in medulla
the ascending limb is not permeable to water, so in response to ISF becoming dilute, ions such as Na+ and Cl- and K+ are actively transported out into the ISF to make it ‘salty’
this creates a conc gradient again so that water exits the DCT and collecting duct
all this, allows for increase water reabsorption
what is the function and structure of the DCT
Na+ reabsorbed due to release of aldosterone > increase blood Na+ > water reabsorption > increase blood volume and pressure
K+ secreted due to aldosterone release
bicarbonate ions reabsorbed
ADH/vasopressin
has few microvilli, many mitochondria
what is the function of collecting tubules and ducts
tubules unite to form ducts
concentrates urine by passive reabsorption of water into medulla (increase by ADH)
what is the juxtaglomerular apparatus (JGA)
regulates systemic blood pressure using RAAS
what are the components of the JGA
Jg cells = endocrine cells in afferent arteriole > produce renin > aldosterone > increase Na+ reabsorption in DCT
Macula densa (part of DCT) = monitor Na+ level in filtrate
what are diuretics
increase excretion of sodium and water
e.g caffeine, alcohol, medications
what are three main metabolic waste products
urea (by-product of AA breakdown)
creatinine (breakdown of creatine phosphate)
uric acid (byproduct of recycling nitrogenous bases of RNA)
how is dilute urine formed
decrease ADH > decrease water reabsorption in DCT and collecting ducts > dilute urine
how is concentrated urine formed
increase ADH > increase water reabsorption in DCT and collecting ducts > concentrated urine
what affect does podocytes contracting have on glomerular filtration
sympathetic stimulation > contract > decrease filtration coefficient and GFR
what is the normal range of GFR
90-140 ml/min
is GFR same for males and females
no, females are on the lower side of the range
does GFR change w age
10% reduction for every 10 years over 20
why is it important to keep GFR within a specific range
maintain fluid and electrolyte balance
does GFR change w changes in BP
typically not, within the autoregulatory range
what starling forces are involved in GFR
glomerular blood hydrostatic pressure = 55mmHg
capsular hydrostatic pressure = 15mmHg
blood colloid osmotic pressure = 30mmHg
how is net filtration pressure measured (NFP)
GBHP - CHP - BCOP
what is the consequence of being unable to regulate glomerular pressure
rapid decline in kidney function
how does vasoconstriction in the afferent arteriole affect GFR
vasoconstrict > decrease blood flow into glomerulus > decrease glomerular capillary BP > decrease net filtration pressure > decrease GFR