Urinary System Flashcards
Functions of the urinary system
- excretes waste in urine
- regulates blood volume
- regulates blood composition
- regulates blood pressure
- regulates blood pH
- regulates blood glucose levels
- produces calcitriol
- produces erythropoietin
how does the urinary system excrete waste in urine?
substances that have no use in the body
metabolic waste products
- urea - breakdown of amino acids
- creatinine - breakdown of creatine phosphate in muscles
- uric acid - catabolism of nucleic acids
- bilirubin - catabolism of hemoglobin
how does the urinary system regulate blood volume?
conserving or eliminating water in urine
how does the urinary system regulate blood composition?
sodium, potassium, calcium, chloride and phosphate ions
how does the urinary system regulate blood pressure?
secrete renin (increased renin causes an increase in BP)
how does the urinary system regulate blood pH?
excrete H+ in urine
conserve bicarbonate ions in blood (buffers)
how does the urinary system regulate blood glucose levels?
can produce and release glucose into blood
Why does the urinary system produce calcitriol?
active form of vitamin D - regulates calcium homeostasis
Why does the urinary system produce erythropoietin?
stimulates production of red blood cells
important electrolytes
sodium
potassium
calcium
magnesium
phosphate
bicarbonate
sodium
extracellular fluid
osmotic gradients - fluid flow - fluid volume
action potential in muscles and nerves
potassium
intracellular fluid
depolarizing membrane potential
calcium
bone health
blood clotting
skeletal muscle contraction
neurotransmitter release
magnesium
bone health
metabolic reactions
phosphate
bone health
cell membrane - lipids
ATP
Bicarbonate
regulation of pH and CO2 transport
Renal anatomy
right kidney is more inferior compared to left due to liver
oblique 30 anteriorly - hilum is directed to aorta
superior part of kidney is posterior
T12-L3
partially protected by ribs 11 and 12
what does an RPO 30 best demonstrate?
the left kidney
left kidney parallel
right kidney in profile
Diagram slide 150
no really go look
anterior to right kidney
right lobe of liver
descending duodenum
hepatic flexure
ascending colon
anterior to left kidney
tail of pancreas
stomach
splenic flexure
descending colon
Surrounding layers of the kindey
renal capsule
adipose capsule
renal fascia
renal capsule
innermost layer
adipose capsule
middle layer
protection and to help hold the kidney in place
Ptosis is the dropping of the kidney from supine to erect (2”)
(neohroptosis is the dropping of the kidneys)
Ptosis is greatest with asthenic body types
renal fascia
outermost layer
dense tissue that connects the kidney to the abdominal wall, lumbar vertebrae and diaphragm
- respiratory excursion of 1”
Renal cortex
outer layer
renal columns - anchor cortex
renal medulla
inner part
Renal pyramids (8-18) - cone shaped
Renal papilla
- drain urine into minor calyces (8-18)
- drain into major calyces (2-3)
when moving from a full inspiration to a full expiration the kidneys move?
1” superior
Slide 156-158 diagrams
No go look stupid
Flow of urine
minor calyces (8-18) > major calyces (2-3) > renal pelvis (1) > ureter (1)
Renal Hilum
indented area on medial side
renal artery
renal vein
ureter
nerves
lymphatics
when does it change from being referred to as filtrate to being described as urine?
the minor calyces
nephron
functional unit
1 million/kidney
located in renal cortex and renal medulla (pyramid)
what are the parts of the nephron?
- renal corpuscle
- renal tubule
what are the parts of the renal corpuscle?
glomerulus - network of capillaries
bowman’s capsule or glomerular capsule - double walled cup
renal corpuscle
blood plasma is filtered
all parts of the nephron are in the renal cortex except the Loop of Henle which is in the renal medulla
Renal tubule
3 parts
1. proximal convoluted tubule
2. loop of henle
3. distal convoluted tubule
blood supply kidneys
- Kidneys receive 20-25% of resting cardiac output
- Renal Arteries (Right is longer than Left and posterior to veins)
- Segmental Arteries – 1 supplies each segment (5)
- Interlobar Arteries – pass through the renal columns
- Arcuate Arteries – arch between the renal medulla and cortex
- Cortical Radiate Arteries – radiate outwards into renal cortex
- Afferent Arterioles – one per nephron
- Glomerulus – capillary network
- Efferent Arteriole – carries blood away from the glomerulus
- Peritubular Capillaries – surround the tubular parts of nephron
- Cortical Radiate veins
- Arcuate Veins
- Interlobar Veins
- Renal Vein
is the afferent or efferent arteriole larger?
afferent is larger than the efferent
what are the 2 types of nephrons?
- cortical
- juxtamedullary
cortical nephron
80-85%
- renal corpuscles lie in the outer part of the renal cortex
- short loop of henle
juxtamedullary nephrons
15-20%
- renal corpuscles lie deep in the renal cortex (close to medulla)
long loop of Henle
- ascending loop of Henle has a thin and thick portion
- long loops allow the kidneys to excrete very dilute or very concentrated urine
histology of glomerulus
large fenestrations (pores)
leaky
allow solutes to leak out - but not blood cells
histology of bowmans capsule
visceral and parietal layers
beetween the layers is the capsular space - lumen where filtrate is collected
histology of the renal tubules
- Proximal Convoluted Tubule (PCT)
2.Loop of Henle; Descending Loop and Ascending Loop
3.Distal Convoluted Tubule (DCT)
- Principal Cells; Receptors for ADH and aldosterone
-Intercalated Cells; Homeostasis of blood pH
What are the three phases of renal physiology?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
Glomerular Filtration - why is the volume of the fluid filtered by the renal corpuscle much greater than other capillaries
1.Large surface area
2.Thin and porous filtration membrane- 0.1 mm; 50 x’s leakier than normal capillaries (large pores)
3.High glomerular blood pressure; Efferent arteriole is smaller than the afferent arteriole
Glomerular Blood Hydrostatic Pressure (GBHP)
- *most responsible for formation of filtrate
- Forces water and solutes through the filtration membrane
- 55 mmHg
- Exists because afferent arteriole is larger than efferent arteriole
Net Filtration Pressure
Caused by the efferent arteriole being smaller than the afferent arterial
NFP = GBHP – CHP – BCOP
= 55 – 15 – 30
= 10
- If GBHP passes below 45… no filtration
- If afferent arteriole dilates… greater NFP
- If efferent arteriole constricts… greater NFP
Capsular Hydrostatic Pressure (CHP)
- Back pressure exerted by fluids already in the capsular space
- 15 mmHg
Blood Colloid Osmotic Pressure (BCOP)
- Presence of proteins in blood that cannot pass through membrane
- Net result is it tries to pull water into the bloodstream
- 30 mmHg
Glomerular Filtration Rate (GFR)
= the amount of filtrate formed by both kidneys each minute
- measure of how well the kidneys are working
- 125 mL/min - average male
- 105 mL/min - average female
cannot actually measure this
decreases with age
effective GFR (eGFR)
- blood test to measure creatinine level
- age
- gender
- race (black or other)
GFR is regulated by
- Adjusting the blood flow into and out of the glomerulus
- Altering the glomerular capillary surface area available for filtration
- Homeostasis of body fluids requires a constant GFR
- If GFR was to fluctuate…If GFR is too high – needed substances may be lost in the urine- If GFR is too low – waste products may not be excreted
GFR is controlled by
1.Renal Autoregulation
2.Neural Regulation
3.Hormonal Regulation
- All mechanisms work by: Adjusting the blood flow into or out of the glomerulus; Altering the glomerular capillary surface area
Renal Autoregulation
- Kidneys help maintain a normal blood flow and GFR
- Even during exercise
- GFR is nearly constant when the mean arterial blood pressure is anywhere between 80 and 180 mmHg
- 2 mechanisms
1.Myogenic Mechanism
2.Tubuloglomerular Feedback - Renal autoregulation is disrupted with chronic kidney disease
Myogenic Mechanism
normalizes GFR within seconds
- If blood pressure rises, stretch receptors trigger the smooth muscles cells to constrict in the afferent arterioles
- If blood pressure drops…opposite occurs
Tubuloglomerular feedback
- Detect increased sodium and chlorine ions and water (because less time for reabsorption)
- Inhibits release of nitric oxide from cells in the juxtaglomerular apparatus (nitric oxide causes vasodilation), thus cause constriction of the afferent arterioles
- Operates much slower than the myogenic mechanism
Neural Regulation
- Sympathetic ANS supplies nerves to the kidneys
- At rest, this system is not controlling GFR (Renal
Autoregulation) - Sympathetic nerve stimulation cause vasoconstriction of the afferent and efferent arterioles
- When blood pressure drops due to hemorrhage or severe dehydration, both the afferent and efferent arterioles constrict
- Decreases renal blood flow and GFR; Reduces urine output (conserves water); Permits greater blood flow to heart and brain
Tubular Reabsorption
- In 45 minutes, more fluid has entered the PCT than there is total blood volume
- Most of the filtrate is reabsorbed from the tubules back into the bloodstream
- Water, glucose, proteins, urea, ions (Na+ , Cl– , Ca2+ , K+ )
- Passive Transport
- Active Transport
Water Reabsorption - Tubular Reabsorption
99% of water is reabsorbed
Solute reabsorption drives water reabsorption
Occurs via osmosis (passive)
1. obligatory
2. facultative
Obligatory Water Reabsorption
90%
- PCT and descending Loop of Henle
Facultative Water Reabsorption
10%
“Capable of adapting to a need”
Regulated by ADH
DCT and collecting ducts
Tubular Secretion
- Tubular secretion is the movement of substances from the capillaries which surround the nephron into the filtrate
- It occurs at a site other than the filtration membrane (in the proximal convoluted tubule, distal convoluted tubule and collecting ducts) by active transport
- The process of tubular secretion controls pH
- Hydrogen and ammonium ions are secreted to decrease the acidity in the body, and bicarbonate is conserved (acts as a buffer)
How much water is reabsorbed versus secreted?
178-179L per day are reabsorbed and returned back to the blood
1-2L per day excreted as urine
0g of glucose secreted - it is all reabsorbed
Proximal Convoluted Tubule
Reabsorption
- water (65%) - obligatory water reabsorption
- almost 100% of glucose and amino acids
- active transport
- sodium, potassium, magnesium, phosphate and sulfate ions
Secretion
- Na+-H+ antiporter - promotes absorption of Na+ and secretion of H+
Loop of Henle
Reabsorption
- Sodium, potassium, chloride, calcium, magnesium ions
- water (15%)
DESCENDING: impermeable to solutes; permeable to water
ASCENDING: impermeable to water; permeable to sodium and chloride ions
- countercurrent multiplication
Distal convoluted tubule
By the end…. 95% of water and solutes reabsorbed
Principal cells
- contain receptors for ADH and aldosterone
- Controls facultative water reabsorption
Intercalated cells
- Homeostasis of blood pH
Renin-Angiotensin - aldosterone system for blood pressure drops
- Renin is released from kidneys
- Renin activates Angiotensin I (inactive)
- Angiotensin-converting enzyme (ACE) converts Angiotensin I to Angiotensin II (active potent vasoconstrictor)
- Angiotensin II causes constriction of the arterioles increasing BP
- Angiotensin II also triggers adrenal glands to release Aldosterone
- Aldosterone promotes Sodium reabsorption which leads to water retention > increased BP
Antidiuretic Hormone for blood pressure drops
- Low blood pressure causes the release of ADH from the
posterior pituitary gland - Promotes FACULTATIVE water reabsorption in the kidney back into the blood
- Increases BP
Atrial Natriuretic Peptide (ANP) on increased blood pressure
Released from the heart when stretched
- Happens when there is too much blood volume
- Causes afferent arteriole to get bigger; Increases GFR and causes a decrease in BP
what is the nephrogram phase in an X-ray?
when the contrast is in the nephron - need to take this right away after injected - just shows outline of kidneys
Ureters
- Retroperitoneal
- Anterior to psoas muscle
- 10” to 12” long
- Peristalsis moves the urine to the urinary bladder (gravity also helps)
- Middle part of the ureter is the most anterior
- As they approach the bladder, they curve medially and pass through the posterior wall on an oblique angle ending at the trigone
- UPJ – ureteropelvic junction (UP)
- UVJ – ureterovesicle junction (no anatomic valve) (Down Near bladder)
Bladder
- Temporary storage of urine – 700 to 800 mL
- Posterior to the symphysis
- Empty – looks like a deflated balloon, then round, then pear-shaped when really full
- Trigone
What part of the ureter is most anterior?
the middle - to best represent this structure flip the patient prone
What is the trigone?
- 2 ureteral openings
- 1 internal urethral orifice
- Smooth appearance
- Rest of bladder has rugae
male bladder
Directly anterior to rectum
female bladder
anterior to the vagina
inferior to uterus
male urethra
20 cm
1. prostatic
2. membranous
3. spongy (penis) - carries urine and sperm
female urethra
4 cm
directed inferiorly and anteriorly
3 places kidney stones commonly get stuck?
Ureteropelvic Junction
Ureterovesical Junction
Pelvic brim where ureters cross anterior to illiac vessels
what are commonly seen in a pelvic image that looks like kidney stones?
phleboliths
How do you best demonstrate the right UP junction?
RPO 30
How do you best demonstrate the left kidney parallel to the IR?
RPO 30
How do you best demonstrate the right kidney in profile?
RPO 30
How do you best demonstrate the left UV junction?
RPO 45
what is a phlebolith?
calcified vessels or veins, most commonly found in the pelvis/bladder
Why would you watch someone void themselves in a fluoroscopy study?
look for ureteric reflux
bladder anatomy labelling slides 220-221
Did you really go quiz yourself?
when they transplant a kidney where do they place it?
down in the pelvis - to protect it, they also usually don’t remove the old ones
what are osteoblastic lesions? what are they common with?
lesions that have extra calcification/bone - prostate cancer
What would happen if you had a kidney stone at the right UP junction regarding filtration or GFR?
Capsular hydrostatic pressure would increase, filtration would decrease
