16 and 17 Flashcards
What does the urinary system consist of
retropertineal structures:
2 kidneys
2 ureters
one bladder
one urethra
what is the positioning of the kidneys
right one lower than left because of the liver on the right side
What is the function of the kidney
excreting wastes
regulating blood ionic composition
regulating blood pH
regulating blood volume
regulating blood pressure
maintaining blood osmolarity
producing hormones
regulating blood glucose
What are the three layers of tissue surrounding the kidney
renal capsule (inner): maintains shape
perineal fat capsule: adipose tissue
renal fascia (outer): connective tissue sleeve
What will happen as a result of loss of perineal fat
drooping (ptosis) of then kideny and potential “kinking” or the ureter – fluid back up in the kidney
What are the two regions of the kidney
outer cortex
inner medulla
Describe the medulla
consists of renal pyramid
- apex of pyramid is the papilla (points towards the renal hilum)
What is between the renal pyramids
renal columns
Describe the path of urine flow in the kidney
collecting duct
- papillary duct
minor calyx
major calyx
renal pelvis
ureters
urinary bladder (storage)
Urethra (discharge of urine)
Where can kidney stones get lodged in
ureteropelvic junction
crossing the iliopsoas muscle (and internal ilac artery)
ureterovesical junction
What would happen if the ureters were obstructed
expansion of the renal pelvis (hydronephrosis) and ureters (hydroureter)
What are blockages of the ureters caused by
renal ptosis, kidney stones, pregnancy, or strictures that form weh nteh ureter is scarred
What are the layers of the ureter
mucosa (urothelium and lamina propria) – innermost
muscularis (inner long., outer circ)
adventitia – outermost, glues ureter onto post abdominal wall
What type of movements aid in movement of urine to bladder
peristaltic contractions
What does the pysiological valve do
exists at the ureterovesical junction
- prevents urinary reflkux and provides some opposition to vacterial movement (prevents from going backwards)
How does the ureterovesical junction work
as the bladder fills, pressure on the blasser wall collapses the ureter, preventing backflow
What happens when the bladder is full
bladder is spherical and extends beyond the tip of the pubic bone
Where is the bladder in males
anterior to the rectum and superior to the prostate
What are the three segments of the bladder in males
prostate
pelvic floor muscles
penis
Where is the bladder in females
anterior to the vagina and inferior to the uterus
What covers the bladder
What does it do
peritoneum which aids in maintaining its position within the pelvis (anchors)
What lines the bladder
transitional epithelium that forms rugae when empty
What type of muscle does the bladder contain
involuntary smooth muscle
(detrusor mecules)
What is the bladder trigone
the openings of the paired ureters and single urethra
What are sphincters derived from the pelvic floor muscles
internal urethral sphincter (smooth muscle)
external urethral sphincter (skeletal muscle)
what are different words for the discharge of urine
micturition
discharge
voiding
What are stretch receptors stimulated
when the bladder fills with about 200-400 mL of urine
what happens after stretch receptors are stimulated
sends messages to the sacral portion of the spinal cord (afferent signals)
triggers an autonomic (parasymp) reflex which causes the detrusor muscle to contract and the internal urethral sphincter (in males) to relax
Which sphincter can be consciously controlled
external urethral sphincter (in males and females)
there must be a conscious effort to relax the external sphincter before urine can be passed through
What are the main parts of the nephrons
renal corpuscle – where blood plasma is filtered
tubules – where renal filtrate is modified by tubular cells absorption and secretion
What is the renal corpscule made of
glomerulus (capillary network) and a glomerular capsule (captures glomerular filtrate)
Describe the pathway through the tubules
proximal convoluted tubule
nephron loop:
- descending limb (thin)
- ascending limb (thick)
distal convoluted tubule
where does glomerular filtration occur
in the renal corpuscle
Where does tubular reabsorption and secretion occur
along the renal tubule and collecting duct
What structure surrounds the tubules
peritubular capillaries
What lines the glomerular capsule
parietal layer
What is the glomerulus lined by
visceral layer
What does the glomerulus do
where the filtrate is made
What is between the glomerular capsule and glomerulus
capsular space (where filtrate is collected)
What is the juxtaglomerular apparatus
next to the glomerulus and helps to regulate its function
What are the layers of the juxtaglomerular apparatus
MD: macular densa
- sense how much filtrate passing through
GC: granular cells
- makes renin
MC: mesangial cells
- modified smooth msucle to regulate size of capillaries
What is the filtration membrane of the glomerulus made of
fenestrated endothelial cells (capillary)
basal lamina
pedicels of podocytes that form filtration slits
what principle does filtration follow
size exclusion principle
high capillary hydrostawtic pressure drives filtraawtion while blood oncotic pressure and capsular hydrostatic pressure oppose filtration
What do the pedicels of podocytes do
from filtration slits
How is glomerular filtration regulated
- what change the rate
autoregulation – mechanisms are internal (intrinsic) to the kidney
altered by blood pressure changes in the clomerulus or leakiness of the capillaries
What are the two machanisms that regulat changes in the glomerular blood pressure
myogenic mechanism (built into muscles)
tubuloglomerular feedback (distal tubules talking back to glomerulus)
What is myogenic mechanism
smooth muscle of the afferent arteriole stretched by the increase in BP and the afferent arteriole responds with constriction which decreases GFR
arterial pressure increases the afferetn arteriole is stretched –> flow increases
vascular smooth muscle responds by contracting thus increasing resistance –> flow returns to normal
What is tubuloglomerular feedback
the macula densa of the juxtaglomerular apparatus detects high amounts of filtrate flow
– increases adenosine release/ production which constricts the afferent arteriole which decreases GFR
what are the steps of tubuloglomerular feedback of GFR
- high concentration or flow of Na+ in the distal convoluted tubule is sensed by the cells of the macula densa – release of adenosine
- adenosine causes constriction of the afferent arteriole,, reducing GFR
What is the main hormones that regulate GFR
Ang-II and atrial natriueretic peptide (ANP)
What does angiotensin II do to GFR
- decrease in blood pressure & sympathetic nervous system stimulation
- juxtaglomerular apparatus
- angiotensinogen –> renin
- angiotensin 1 –> ACE
- angiotensin II
- Constriction of systemic and glomerular afferetn arterioles
- blood pressure increases
decreases GFR because it constricts the afferent arterioles but increases blood pressure because it also constricts systemic arterioles
What substances are completely reabsorbed
glucose
amino acids
bicarbonate ion
What substances are regulated and thus partially reabsorbed
water
sodium
potassium
chloride
What substances are excreted as waste
urea
creatinine
drugs and drug metabolites
What mechanisms work in reabsorption
active transport (requires energy)
passive transport (substances moving down their electrochemical gradient)
osmosis (movement of water following its concentration gradient through a semipermeable membrane)
What drives osmosis
movement of the solutes from the tubules to the interstitial fluid
often requires energy
What does obligatory reabsorption mean
90% of water movement
has to happen
dragged along by the solutes being moved from tubule sto intersitial fluid
What does facultative reabsorption mean
10% of water movement
can increase or decrease depending on the amount required by the body
Where will obligatory reabsorption occur
proximal convoluted tubule and descending loop of Henle
- areas have tubules permeable to water
What controls facultative water reabsorption
antidiuretic hormone
- makes the cells in the collecting duct permeable to water
What drives osmosis
passiive reabsorption (diffusion) of several ions as well as the waste product urea
Where is reabsorption most acitve
proximal convoluted tubuule
- by the end, 100% of organic solutes have been reabsorbed, 60% of water reabsorbed
What are the routes in passive transport
paracellular route: solutes slip between the tight junctions of the cell
transcellular route: into or out of the cells by following their electrochemical gradient
How is passive transport facilitated
by transport proteins as in the movement of glucose from inside the tubular cells to the interstitial fluid
by leakage channels for some ions to facilitate their walk down the concentration gradient
What are the two types of active transport
primary active transport: strictly with the use of ATP
secondary active transport: uses the energy of the movement of ions down their concentration gradietns to transport other solutes
- symporter: transport protein moves solutes in the same direction
- antiporter: transport protein moves solutes in the opposite direction
- both are called co-transporters
Where does the reabsorption of glucose from the filtrate occur
proximal convoluted tubule
where does the Na+/H+ antiporter operate
proximal convoluted tubule
