Urinary system Lecture Review Flashcards
what is the functions of the urinary system
1) Filters blood (to produce urine)
2) Excretion of metabolic waste products & water soluble toxins
3) Maintains fluid balance (regulates Blood volume & BP)
4) regulates solute conc. in body osmolarity
5) Maintains blood ph
where are the kidneys
retroperitoneal
T12-L3
what is fibrous capsule
collegen on kidney surface
what is adipose capsule
cushion & support kidney
what is renal fascia
dense CT, anchors kidney to muscle or dorsal wall of abdomenopelvic cavity
what are the 3 regions of the kidneys & what is in them
1) Cortex
2) Medulla - medullary columns & pyramids
3) Sinus - renal pelvis, major calyx, minor calyx
Explain the flow of urinary drainage
1) Collecting ducts in medullary pyramids
2) Minor calyx
3) Major calyx
4) Renal pelvis
5) Ureter
6) urinary bladder
7) Urethra
what is the functional unit of the kidney called
nephron
what are the 3 functions of a nephron
1) Filtration
2) Reabsorption
3) Secretion
Explain nephron filtration
-Filtrate of blood pushed across glomerulus to form urinw
explain nephron reabsorption
-Movement of useful molecules from tubules back into blood **So they aren’t lost in urine
explain nephron secretion
-transport undesirable molecules (so they can be excreted into urine) from blood into tubules
where are peritubular cappillaries
Material exchange (DCT & PCT)
where is the vasa recta
around loops of nephron (material exchange)
what are the ureters lined with
transitional epithelium & smooth muscle
what is the urinary bladders mucosa layer do
Lined with traditional epithelium, forms rugae & stretched
what is the submucosa of the urinary bladder
connective tissue
what do the muscular of the bladder form
the detrusor muscle that expels urine
what does the internal urinary sphincter do
prevents leakage (smooth muscle)
what does the external urinary sphincter do?
Voluntary control ( Skeletal muscle)
explain micturition reflex
Bladder fills - stretch receptors sense - signal passes on sacral nerve -reflexive contraction of detrusor muscle - relaxation of internal urinary sphincter
- Cycles become more freq. as the bladder reaches capacity
- Center in PONS can promote micturition of storage
- Conscious relaxation of external sphincters still needs to happen for urination to occur
how much urine is output per day & how is it formed
1/2 L a day & by filtering blood
what are the 3 components of nitrogenous waste
1) Urea
2) Creatinine
3) Uric acid
how is urea formed
Amino acid breakdown
how is creatinine formed
creatine-P breakdown
how is uric acid formed
nucleotide breakdown
What electrolytes are found in urine
Na+, Cl-, K+, Mg2+, ca2+, H+, bicarbonate ion, PO4-
what is urobillin
yellow pigment from heme breakdown
how do hormones get into urine
b/c they’re in the blood
what is it called when there is glucose in urine
glycosuria (Diabetes)
what is it called when there is proteins in urine
Proteinuria (Kidney disease/ damage)
what is it called when there is blood/ hemoglobin in urine
hematuria (Inflammation, infection, kidney stones, trauma)
what is it called when there is bile pigments in urine
Billirubinura (Liver disease)
what is it called when there is ketones in the urine
Ketonuria (Starvation, abnormal fat metabolism, diabetes)
what is the general idea of glomerular filtration
Hydrostatic pressure in glomerular capillaries forces a filtrate of blood into glomerular capsule
What does the filtrate contain
It is filtered plasma
- Water, electrolytes, nutrients (glucose, aminos), urea, uric acid, creatinine
- contains everything in plasma except blood cells & protein
where does filtration occur
across the filtration membrane
What is the filtration membrane
Membrane of renal corpuscle that filters blood from filtrate
-Formed from Endothelium of fenestrated capillaries & basement membrane & podocytes
how does filtrate move through the filtration membrane
moves through pore in-between epithelial cells & through basement membrane
Then it moves through a filtration slit in between the podocytes
what is the visceral epithelium of the capsule
The podocytes
What is glomerular filtration rate
Volume of filtrate formed per minute
what is glomerular filtration rate affected by
Renal blood pressure
For glomerular filtration to occur:
Glomerular hydrostatic pressure must be greater than the sum of capsular hydrostatic pressure & blood colloid osmotic pressure
what is the GHP
push from capillary into capsule
what is the CsHp & BCOP
pushing back into the blood
what is the NFP
net filtration pressure, has to be positive for filtration to occur
-needs adequate BP
how do u regulate glomerular filtration
by regulating the renal BP & Blood flow
what are the 3 mechanisms of renal bp & blood flow
1) Autoregulation
2) Neural regulation
3) Hormonal regulation
what is autoregulation
Local
-Kidneys adjusts it’s own BP & blood flow
The efferent arteriole ALWAYS has a smaller diameter than the afferent arteriole even when both are fully dilated
-Also used myogenic mechanism & tubular mechanism
what is the myogenic mechanism
smooth muscle in the arterioles CONTRACTS when stretched and RELAXES when not stretched.
-Decreased BP to kidneys-> decrease GFR -> decreased stretch, so relaxation-> vasodilation of AFFERENT arteriole-> increased glomerular filtration rate
what is the tubular mechanism (what is the macula dense)
-the MACULA DENSA monitors Na+ concentration in filtrate. The macula dense is modified epithelial cells in the DCT that release chemicals that cause vasoconstriction of afferent arteriole when NA+ is in high concentration. They’re also called the sodium sensing cells.
Nacl concentration in DCT is related to flow rate, meaning it is so high that there is less time for reabsorption.
-Increased GFR-> increased Na+-> vasoconstriction of afferent arteriole -> decreased GFR
explain the neural regulation of glomerular filtration
fight/flight/exercise/blood loss all divert blood away from kidneys. This is how it works:
Sympathetic ANS -> Norepinephrine -> Vasoconstriction of afferent arteriole -> decreased glomerular filtration rate
**can override local control.
***Hormones can also help maintain GFR by also causing vasoconstriction of efferent arterioles
Explain hormonal regulation of glomerular filtration rate
-All hormones that affect BP, affect GFR.
Renin angiotensin aldosterone system.
1) The Jg cells detect less stretch, & macula densa detects less Na+ in filtrate
2) indicates low GFR
3) Jg cells release renin
4) Activates angiotensinogen into angiotensin 1
5) ACE enzyme in lungs activates angiotensin 1 into angiotensin 2
6) This causes release of aldosterone & vasoconstriction
7) The aldosterone will increase sodium & h20 reaborptiin in DCT, & vasoconstriction will increase BP which will increase GFR
what is tubular absorption
reabsorption of substances in filtrate back into blood
Recovery of lost solutes
where does most of the tubular absorption take place
the PCT b/c cubical epithelium has microvilli = huge SA
Can occur all along the nephron loop DCT & collecting ducts too
what methods of reabsorption happen in tubular absorption
- Active transport of Na+ (80% of it)
- Facilitated transport & cotransport with Na+ (Glucose, amino acids, vitamins) (100%)
- diffusion of Cl-, K+, bicarbonate, magnesium, calcium (80% down electrochemical gradient)
- osmosis of h20 following the solute
which hormones effect tubular reabsorption of ions
- Parathyroid hormone (increased Ca2+ reabsorption from DCT)
- aldosterone (increased Na + reabsorption from DCT)
what is a transport maximum (Tubular absorption)
the transport carriers become saturated. if renal threshold (plasma conc. @ which carriers become sat.) is exceeded, substances will appear in urine. For example glycosuria.
What is Tubular secretion
the secretions of substances from peritubular blood into tubular filtrate
- the removal of undesirable solutes
- Active transport of waste into filtrate
- secretion occurs along length of renal tubule
what hormones affect secretion
Aldosterone (increases K+ secretion) (K+ secretion is coupled to the reabsorption of Na+)
- stimulates active transport of NA+/K+ pump.
- regulates both sodium & potassium levels
what are the 2 ways that urine is concentrated & their effectiveness
- Obligatory water reabsorption (H2O follows solute, 85% recovery)
- Facultative water reabsorption (can recover up to 99% of water to produce very concentrated urine. 4X more conc. than plasma)
where is most water reabsorption from filtrate done by
Juxtamedullar nephrons (in cortex) & collecting ducts
why is facultative water reabsorption urine concentration possible ? (3 reasons)
1) medullary gradient
2) Counter current mechanism
3) ADH
What is the medullary gradient
progressive increase in solute conc. of intersisitial fluid from contex (300) to medulla (1200).
what creates the medullary gradient
Due to active transport of na+ and cl- out of the ascending nephron loops of juxtamedullary nephrons & diffusion of urea from collecting ducts
what is the counter current mechanism
blood in the vasa recta flows the opposite direction to filtrate.
- filtrate in descending loop flows opposite direction to ascending loop
- this establishes & maintains the medullary gradient & enhances the reabsorption of water
- **and reabsorption is further enhanced by special nephron loop properties
what is the special property of the descending nephron loop
- thin
- h2o permeable -> leaves due to gradient
what is the special property of the ascending nephron loop
- thick
- impermeable to h20
- nacl actively transported out (creates gradient)
what does antiduiretic hormone or vasopressin do to increase urine concentration
- peptide hormone produced in hypothalamus, stored in post. pituitary.
- secreted in response to dehydration (hi. solute concentration in plasma)
- EFFECT: causes aquaporins to appear in collecting ducts -> H20 leaves filtrate & concentrates urine
if you’re well hydrated you have ….
less ADH, collecting duct impermeable, no water leaves & u have dilute urine
if you’re dehydrated you have…
more ADH, collecting duct permeable, h20 leaves, and it is concentrated urine
how is fluid, electrolyte & ph balance mainly regulated
-adjusting urine concentration & volume
what are the 2 electrolyte compartments & how do they differ
ICF(intracellular fluid - within cells) & ECF (extracellular fluid - Interstitial or plasma)
-electrolytes differ
what is ECF
extracellular fluid (outside of cells either interstitial fluid (outside normal cells) or plasma (surround blood cells)
what is ICF
intracellular fluid (WITHIN CELLS)
where is 60% of the fluid held
intracellular
40% is extracellular
what electrolytes is in intracellular fluid
k+, protein, mg2+, HpO4-2
what electrolytes are in interstitial fluid
na+, cl-, HCO3- (Bicarbonate ion) (NO PROTEIN)
what electrolytes are in plasma
Na+, Cl-, Bicarbonate ion, protein
is osmolarity in ICF & ECF similar ?
yes, & water can move between any compartments
what is osmolarity
moles of solute contributing to osmotic pressure
what is fluid balance input sources
beverages, food, metabolism (cell respiration)
what is fluid output balance sources
urine, sweat, feces, exhalation
what is the main mechanism for regulating fluid balance
regulation of urine volume
explain how dehydration leads to decreased urine volume, which is important in fluid balance
1) Dehydration
2) Increased plasma osmolarity & decreased plasma volume
3) the increased osmolarity causes osmoreceptors in the hypothalamus to react
4) The decreased plasma volume causes the barororeceptor in the arterioles to react
5) Both the osmoreceptors & baroreceptors cause the thirst enters in the hypothalamus to react
6) The hypothalamus triggers you to increase fluid intake by feeling thefts & it released ADH from it’s pitutitary glad
7) The thirst centre also causes the small intestine to rapidly absorb H20
8) The kidneys react by increaseing h20 reabsorption by pumping out Na+
9) Meanwhile, baroreceptors in the arterioles also activates the RAAS system
10) Aldosterone is released and causes Na+ to be reabsorbed also
11) all this H20 reabsorption decreases urine volume & decreases H20 Lost
electrolyte balance is important in…
- Water balance (blood vol. +Bp)
- acid base balance (H+ conc.)
- electrochemical gradients (nt. function)
- cellular metabolism
what does sodium do
accepts Blood volume, nerve & muscle function
what hormones affect sodium
1) Aldosterone
2) Natriuretic peptides
3) cortisol & estrogen
what does aldosterone do to na+
increases reabsorption from DCT
what does natriuretic peptides do to sodium
decrease sodium reabsorption, decrease aldosterone secretion
what does cortisol & estrogen do to sodium
aldosterone like effects. (increases reabsorption)
what is hypernatremia
Hi levels of na+ in blood.
what is hypernatremia causes by
dehydration, burns, diabetes insidious
what is hyponatremia
low na+ in blood
what is hyponatremia caused by
excessive water intake, renal failure, vomiting & diarrhea
what does potassium do
affects nerve & muscle function (electrochemical gradient)
-k+ secreted when na+ is reabsorpted so a lot of it is lost in urine
but when filtrate is acidic, Na+ is exchanged for h+ instead which decreases k+ loss in urine.
Must replenish K+ with fruit & veg
what is hyperkalemia
hi levels of potassium
what causes hyperkalemia
renal disease, antihypertensive meds, decreased aldosterone, chronic acidosis
***IT IS A MEDICAL EMERGENCY
what is hypokalemia
low k+ levels
what is hypokelemia causes by
diarrhea, vomit, some diuretics
what does calcium do
important in neuromuscular function, coagulation, intracellular signal & enzyme cofactor
what is the hormonal regulation of calcium
- Parathyroid hormone increases Ca2+ reabsorption from DCT & absorption in intestines to increase blood calcium
- the can be stored in bones
what is hypercelcemia
increased ca 2+ levels due to hyperparathyroidism
what is hypocalcemia
decreased ca2+ levels do to hypoparathyroid, renal disease or vitamin D deficiency
how is phosphate regulated
by parathyroid hormone & ca affect ca2+ levels. Increased phosphate causes decreased parathyroid which causes ca2+ excretion
what is ph
-log of hydrogen ion concentration
what is the normal ph of plasma & ECF
7.35-7.45
anything below or above 7.35-7.45 is either acidosis or alkalosis
these have dangerous systemic effects
metabolic processes do what to blood ph
lower blood ph. The main problem is acidosis
how is respiratory acidosis caused
Aerobic resp. -> increased CO2 (it’s a product) -> carbonic acid -> respiratory acidosis
how is metabolic acidosis caused
1) Anaerobic resp. -> lactic acid -> metabolic acidosis
2) Lipid metabolism -> fatty acids -> metabolic acidosis
3) Protein metabolism -> Amino acids & ketone acids -> Metabolic acidosis
how is alkalinosis caused
from hyperventilation or bicarbonate ion poisoning
what are the 3 main buffering systems
1) Buffers
2) Resp. System / compensation
3) Urinary system
what are the 3 types of buffers
1) Protein
2) Phosphate
3) bicarbonate
What is the function of buffers
reduce changes to pH by binding or releasing H+
Both ICF & ECF have buffers
explain the protein buffer system
- most common buffering in plasma & ICF (Cytoplasm)
- If it is alkalosis in the blood, than the amino acids release h+
- if it is acidosis in the blood than the amino acids bind h+
Explain the phosphate buffer system
-HPO4-2 (Monohydrogen phosphate) buffers acid in ICF and urinary filtrate
Explain the bicarbonate buffering system
this is the main mechanism in ECF
-Hco3- (bicarbonate ion) can mop up h+
HCO3- + H+ -> H2Co3 (carbonic acid) -> Co2 +H20
what is the alkaline reserve in bicarbonate buffering system
Refers to blood conc. of bicarbonate ion, much of what i in the from of NaHCO3 (Sodium bicarbonate)
Explain the respiratory systems / respiratory compensation buffering system
-Acidosis and increased H+ due to carbonic acid, stimulates the resp. centres.
Increased resp. rate corrects Co2 by exhaling
explain the urinary system buffering system
Renal correction of acidosis & Alkilosis
Urine pH varies.
Renal correction of acidosis: Increased secretion h+ (acidic urine) and reabsorb HCO3- (Bicarbonate ion)
What is renal correction of alkalosis: increased reabsorption of H+ and secretion of HCO3- (Barcarbonate ion) (alkaline urine)
