Urinary system part 2 Flashcards
diverticulitis
when pressure builds up in sigmoid colon, weakened walls form out pockets called diverticula = diverticulosis
- when things get stuck and the diverticula get inflamed, it results in diverticulitis
- fistula can form = a canal b/w 2 organs
treatment of mild diverticulitis
antibiotics to treat infection
high fiber diet
fluid diet until healed
treatment of severe diverticulitis
colonoscopy: 2 parts
1. surgically remove part of inflamed colon, take healthy part and attach it to a hole in the abdominal wall called a stoma and put a bag on it
2. once colon has healed, reattach colon to rectum again
true vs false diverticula
true are made up of all layers of large intestine
false are only pockets that consist of serosa
3 processes in urine production
- glomerular filtration
- tubular reabsorption
- tubular secretion
results in fully filtered blood and production of urine
glomerular filtration
occurs in renal corpuscle,
where water and solutes move into Bowman’s capsule
renal bloodflow
20-25% of CO goes to kidneys at rest
this is about 1.2 L/min
renal plasma flow rate
55% of renal blood flow
is about 650 mL
- this is the amount of fluid that COULD be filtered
filtration fraction/ somewhat lumped with glomerular filtration rate
16-20% of the plasma flow rate
is about 125 mL/min OR 150-180 L/day
contributors to net filtration pressure (NFP)
- glomerular blood hydrostatic pressure
- capsular hydrostatic pressure
- blood colloid osmotic pressure
- the last 2 both work against GBHP
glomerular blood hydrostatic pressure (GBHP or GCP)
55mmHg
- the driving pressure in the afferent arteriole that works towards producing filtrate
- same as regular BP bc pressure in efferent arteriole is less which gives driving pressure
capsular hydrostatic pressure (CHP)
15mmHg
- pressure in capsular space due to the constant presence of some amount of glomerular filtrate
- works against producing filtrate
blood colloid osmotic pressure (BCOP)
30mmHg
- because filtration membrane doesn’t allow proteins to leave the glomerulus, the proteins on the inside are attracting the water outside to their area of higher concentration inside the glomerular capillaries
- works against producing filtrate
how is net filtration pressure calculated and what is it?
NFP = GBHP - CHP - BCOP
= 55 - 15 - 30
= 10 mmHg
glomerular filtration rate
the amount of filtrate formed in all renal corpuscles in both kidneys per minute
- average rate for women is 105 mL/min,
for men is 125 mL/min
- filtration stops if GCP (GBHP) drops to 45mmHg bc NFP becomes 0 then
what happens when GFR is too high
we may not be able to absorb things quickly enough and things that we want could be leaving the body
what happens when GFR is too low
filtrate may spend too much time in renal tubules and things we don’t want might be reabsorbed
ways GFR is regulated
2 ways:
- adjusting blood flow (by decreasing BF, we decrease the amount of filtrate produced)
- altering glomerular capillary surface area (less SA means less filtrate produced)
mechanisms of GFR control
- renal autoregulation
- neural regulation
- hormonal regulation
renal autoregulation of GFR
keeps rate relatively constant despite changes in BP, etc
incl: myogenic mechanism and tubulogomerular feedback
myogenic mechanism
a mechanism of renal autoregulation
- fast response to BP changes
- an increase in BP causes afferent arteriole walls to stretch causing smooth muscles to contract and decrease blood flow to glomerulus, thus GFR returns to normal
- prevents high BP from affecting GFR too much
- also works in response to a decrease in BP
tubuloglomerular feedback
a mechanism of renal autoregulation
- slower because have to wait for fluid to move through tubules and back to juxtaglomerular apparatus to know if adjustments need to be made or not
- GFR increases when Na+, Cl- and water are not reabsorbed, leaving more stuff in tubules
- this is detected by macula densa and inhibits release of nitric oxide (a vasodilator) from juxtaglomerular apparatus, causing afferent arterioles to constrict, decreasing blood flow to glomerulus and decreasing GFR
neural regulation of GFR
sympathetic ANS innervation
not a lot at rest
not a lot when moderate sympathetic stimulation
- larger sympathetic stimulation ex. exercise: vasoconstriction of afferent arterioles causes a decrease in blood flow and GFR, lowering urine output and allows blood flow to other tissues
hormonal regulation of GFR
2 methods:
- atrial natriuretic peptide
- angiotensin II
atrial natriuretic peptide (hormonal regulation of GFR)
increases GFR
- stretching of atria occurring bc of increase in blood volume causes ANP to be released from cells near atria
- relaxes glomerular mesangial cells which increases capillary SA, producing more filtrate, urine and decreasing blood volume to get back to norm
angiotensin II (hormonal regulation of GFR)
reduces GFR
- a vasoconstrictor that narrows afferent AND efferent arterioles therefore decreasing blood flow and GFR
tubular reabsorption
- nephron reabsorbs 99% of filtrate
- most reabsorption occurs in PCT
- water, solutes, glucose, AA, urea, ions (Na, Cl, Ca2+, bicarbonate, phosphate) and small proteins
tubular secretion
transferring materials from blood into glomerular filtrate/tubular fluid
- controls blood pH (H+ secretion)
- eliminates substances (ammonia, creatinine, K+, some drugs)
primary active transport
ATP dependant transport used to move ions against their concentration gradients
ex. Na+/K+ pump
secondary active transport
driven by ion’s electrochemical gradient via symporters and antiporters
symporter
bring substances in same direction (towards cell)
ex. Na brings glucose with in into the cell and we need active transport to create a low concentration of Na+ inside the cell, keeping the electrochemical gradient
antiporter
move substances in opposite directions
ex. Na+-H+: for every Na+ that enters, a H+ leaves the cell, levels of Na+ inside stay low because of Na+/K+ ATPase
methods of water reabsorption
obligatory water reabsorption
facultative water reabsorption
obligatory water reabsorption
90% of water
water follows the solutes absorbed via osmosis
aquaporin-1: a protein water channel found in apical and basolateral membranes of PCT and descending limb of nephron loop
- facilitates water transport and helps water movement
facultative water reabsorption
10% of water
- water reabsorbed based on need regulated by ADH
- primarily occurring in collecting ducts and end of DCT
overall reabsorption in the PCT
65% of water, all glucose and AAs reabsorbed here
sodium symporters and antiporters
passive reabsorption of ions later in PCT
Na+ symporters reabsorption in PCT
- help reabsorb glucose, AAs, lactic acid, water-soluble vitamins, other nutrients in first half of PCT
Na+ antiporters reabsorption in PCT
help reabsorb Na+ while H+ secreted into PCT aides in bicarbonate reabsorption
reabsorption in 2nd half of PCT
passive reabsorption of Cl-, K+, Ca2+, Mg2+, urea, by diffusion, and water by osmosis
- osmolarity in this region is the same as in the blood bc water is constantly following movement of solutes in this region
reabsorption in descending limb of nephron loop
simple squamous cells here
- 15% of water reabsorbed and small diffusion of solutes back into tubule drives out more water
- concentration of solutes gets greater as loop of Henle dips further into medulla and os more water is reabsorbed through simple squamous cells
reabsorption in ascending limb of nephron loop
cells impermeable to water here so water is not absorbed, but ions are
thin: simple diffusion out
thick: active transport of K+, Na+, Cl- out
reabsorption in DCT
PTH controls Ca2+ reabsorption here
10-15% water reabsorbed
Na+ and Cl- are reabsorbed by symporters
principal cells
reabsorb Na+ and secrete K+ into end of DCT and collecting duct
- controlled by ADH and aldosterone
intercalated cells
reabsorb K+ and bicarbonate ions and secrete H+ into end of DCT and collecting duct
- helps maintain blood pH
osmolarity
the number of solutes in a given amount of fluid
ex high osmolarity means a high amount of solutes
hormonal regulation of tubular reabsorption and secretion
5 hormones regulate Na+, Cl-, Ca2+, and water reabsorption along with K+ secretion in renal tubules angiontensin II aldosterone antidiuretic hormone atrial narurietic peptide parathyriod hormone
renin-angiotensin system
the steps needed to produce the active form of angiotensin II triggered by a decrease in blood volume and/or blood pressure:
- less stretch in afferent arterioles (and increases in SNS)
- juxtaglomerular cells secrete renin into blood
- renin concerts angiotensinogen into angiotensin I
- angiotensin converting enzyme (ACE) converts angiotensin I into angiotensin II
renin
acts like an enzyme, released from the kidneys into the blood
- meeds to find its substrate (angiotensinogen) to have action
angiontensinogen
- released from the liver
- renin cleaves off some AAs to create angiontensin I
ACE
angiotensin converting enzyme
- made in lungs
- cleaves off a few more AAs and converts angiotensin I into angiotensin II
angiotensin II
- decreases GFR by vasoconstriction of afferent arterioles to prevent loss of too much fluid
- increases Na+, Cl+ and therefore water reabsorption in PCT by stimulating Na+/H+ antiporters (Na takes Cl bc of charge and ion movement brings water w it)
- causes adrenal CORTEX cells to secret aldosterone: principal cells in collecting duct reabsorb Na+, Cl- and water and secrete K+
antidiuretic hormone (ADH)
key to making concentrated or dilute urine, works when BP/volume are low
- increases water permeability of principal cells by facultative water reabsorption through insertion of aquaporin-2 channels from inside the cell into the cell membrane
- regulated by negative feedback loop, detected by osmoreceptors going to hypothalamus causing ADH to be released from posterior pituitary, when BP gets low
atrial natriuretic peptide (ANP)
target: mesangial cells of glomerulus and tubules
- works when BP/volume is high
- release from heart stimulated by a large increase in blood volume
- - inhibits reabsorption of Na+ and water in PCT and collecting ducts
- - suppresses secretion of aldosterone and AND which causes more Na+ and water to be excreted and more urine to be produced
parathyroid hormone (PTH)
- released from parathyroid glands in response to low blood Ca2+
- stimulates cells in early DCT to increase reabsorption of Ca2+
- also inhibits phosphate reabsorption in the PCT
production of dilute or concentrated urine
- despite varying fluid uptake, we still maintain homeostasis of fluids in the body
- kidneys regulate water loss in urine
- ADH controls whether dilute or concentrated urine is produced—- dilute urine is the default until ADH gets released
formation of dilute urine
glomerular filtrate and blood have same osmolarity of 300mOsm/Liter
- tubular osmolarity changes due to concentration gradient in medulla
when dilute urine is formed, osmolarity in the tubule:
- increases in descending limb: water moves out freely bc of aquaporin-1
- decreases in ascending limb: only ions can move out, leaving more water in tubule
- decreases even more in collecting duct: water not freely moving, only ions move out and filtrate gets more dilute
what does it mean for urine to be dilute
it has fewer solutes than plasma present
formation of concentrated urine
everything is the same until the collecting duct where lots of water gets reabsorbed when ADH increases
- compensation for low water intake or heavy perspiration
- principal cells move water (ADH present) if interstitial fluid surrounding nephron loop has high osmolarity
- long loop juxtamedullary nephrons create gradient by Na+/K+/Cl- symporters reabsorbing Na+ and Cl- to create osmotic gradient in medulla
characteristics of normal urine
- 1-2 L produced per day
- yellow or amber colour, may vary with diet
- transparent, shouldn’t be cloudy
- pH ranges from 4.6-8, avg of about 6, but varies with diet
- slightly aromatic
anatomy of ureters
25-30 cm long, 1-10mm diameter
- run from renal pelvis to bladder where they enter halfway down on the posterior
- retroperitoneal
ureter valve anatomy
physiological valves
when bladder is empty, valve is open and urine can flow in
when bladder is stretched, it closes the valves so the bladder doesn’t get too full
flow through ureters results from
- gravity
- peristalsis: alternating contractions of circular and longitudinal muscle
- hydrostatic pressure: urine moves from high to low pressure areas
mucosa layer in ureter wall
- transitional epithelium that stretches and changes shape and lamina propria holds epithelial cells together
- goblet cells produce mucous and prevents cells from contacting the urine bc its pH can vary a lot
muscularis layer of ureter wall
2 layers of smooth muscle: inner longitudinal and outer circular
- distal 1/3 has additional outer longitudinal layer which is the same organization as found in the bladder
adventitia layer of ureter wall
layer of areolar CT that holds ureters in place
urinary bladder
- distensible, hollow and very muscular organ
- holds 700-800 mL
- located posterior to pubic symphysis
in females is anterior to vagina and inferior to uterus
in males is anterior to rectum
trigone
mucosa layer pulled tighter here
- triangle shaped region between ureteral openings and internal urethral oriface
detrusor muscle
smooth muscle that contracts to push urine into urethra, just the 3 layers that make up the muscularis layer
internal urethral sphincter
smooth muscle therefore involuntarily controls opening and closing of urethra
- an extension of the muscularis layer
external urethral sphincter
located in deep muscles of peritoneum, voluntarily controls opening and closing of urethra because composed of skeletal muscle
- part of muscles of pelvic floor and people with weak pelvic floor muscles have less control of opening since it wraps around the urethra to control it
micturition reflex
- urination reflex
1. stretch receptors activated when volume is 200-400mL
2. impulse is sent to micturition centre in sacral SC (S2 and S3) and reflex is triggered
3. parasympathetic fibers cause detrusor muscle to contract, and external and internal sphincter muscles to relax - this inhibits the signal from coming to the external urethral sphincter so it stays relaxed
4. cerebral cortex recognizes the urge to urinate so it can initiate micturition or delay it’s occurrence for a limited period of time
- this inhibits the signal from coming to the external urethral sphincter so it stays relaxed
male urethra
20 cm long
has mucosa and muscularis layers
3 regions
regions of the male urethra
prostatic urethra
intermediate urethra
spongy urethra
prostatic urethra
1st portion of male urethra
- transitional epithelium becomes stratified/pseudostratified columnar
- runs through prostate gland and seminal gland region
- sperm and seminal fluid are added to urethra here
intermediate (membranous) urethra
2nd portion of male urethra
- stratified or pseudostratified columnar epithelium
- passes through perineum and runs through pelvic floor muscles which control opening of urethra consciously
spongy urethra
3rd portion of male urethra
- stratified or pseudostratified columnar epithelium becomes stratified squamous near exterior
- passes through penis
female urethra
4 cm long
- external orifice is b/w clitoris and vagina
- transitional epithelium changes to stratified or pseudostratified columnar and then stratified squamous epithelium near orifice
- has mucosa and muscularis layers
