Topic 6 Urine Formation overview Flashcards
Renal Function top reasons? (4)
- Regulation of water and electrolyte balances*
- Regulation of body fluid osmolality and electrolyte* concentrations
- Regulation of blood pressure*
- Regulation of acid-base balance
Urea comes from ?
amino acid metabolism
Secreted in urine
Creatinine comes from?
from muscle creatine
Creatine used to create phosphocreatine which serves as energy source for production of ATP in muscle. Each day 1 to 2% of muscle creatine converted to creatinine
Secreted in urine
Uric acid comes from ?
from nucleic acids
Secreted in urine
End products of hemoglobin break down to what?
bilirubin
Secreted in urine
Fluid / salt intake usually depends on what?
individual eating / drinking habits
Kidneys are able to respond to what levels of fluctuation of Na concentration with still small changes in ECF Vol? (mEq/day)
- 10 mEq/day to 1500mEq/day
- Able to respond to huge differences in sodium intake with relatively small changes in ECF volume or [Na+]
- Also true for most other electrolytes
Kidneys work with what other systems for acid base regulation?
Lungs
Body Buffer Systems
sulfuric and phosphoric acid come from what?
Byproducts of protein metabolism
Acid base Regulation. what do Lungs and kidneys control?
-Lungs remove carbon dioxide
-Kidneys control hydrogen ion and bicarbonate
concentration and only way to remove sulfuric and phosphoric acid
Almost all erythropoietin is secreted from where?
Kidney
which stimulates red blood cell production by hematopoietic stem cells in bone marrow
What is a major stimulus for Erythropoietin production?
hypoxia
Patient’s with severe renal disease will develop what bc of lack of production of erythropoietin?
severe anemia due to lack of erythropoietin production
Glucose Synthesis occurs when?
- During prolonged fasting
- Significant quantities can be produced from kidneys
Gluconeogenesis (aka glucose synthesis)
-Kidneys synthesis glucose from amino acids and other precursors during fasting
Glomerular Capillaries - high hydrostatic pressure produces/causes what? what mmHg?
High pressure (60mmHg) produces high/rapid rate of fluid filtration
Peritubular Capillaries - low hydrostatic pressure produces/permits what? what mmHg
Low pressure (13 mmHg) produces high/rapid rate fluid reabsorption
Each kidney weighs what approx? gms
150 grams
By adjusting the resistance of afferent and efferent arterioles the kidneys can regulate what?
hydrostatic pressure in both glomerular and peritubular capillaries this changing glomerular filtrate and tubular reabsorption.
Peritubular capillaries empty into what?
vessels of venous system
% of all nephrons that are juxtamedullary nephrons?
20 to 30% of all
Each kidney contains how many nephrons?
800,000-1 million nephrons
After age 40 what happens to the # of nephrons?
lose 10% every 10 years
Each nephron contains what two things>
1) glomerulus - where fluid filtered (tuft of glomerular capillaries)
2) Long tubule - where filtered fluid is converted into urine
Micturition - what kind of reflex?
An Autonomic reflex but can be inhibited/facilitated by centers in cerebral cortex or brain stem (voluntary)
what is Micturition?
process by which bladder empties when it becomes filled
Detrusor muscle - type of muscle?
smooth muscle chamber
muscle fibers go in all directions
Urinary bladder inner lining what?
rugae
Trigone
above bladder neck
its inner mucosa (lining) is smooth
Micturition 2 steps?
- Bladder fills, tension rises above threshold level
2. A nervous reflex (micturition reflex) empties bladder or causes conscious desire to pee
Bladder Innervation, main supply of nerves come from ?
Pelvic nerves
Pelvic nerves
sensory nerve fibers - detect stretch
motor nerve fibers - parasympathetic fibers
Pudendal nerve
Skeletal motor fibers come thru this nerve to the ext. sphincter.
–skeletal muscle fibers provide Somatic (voluntary) control of external sphincter
Sympathetic control (innervation) of bladder via what nerves?
- hypogastric nerves
- Control mainly the blood vessels (as opposed to controlling contraction.
Ureters well supplied with what type of nerves?
pain nerves
Ureterorenal Reflex stimulated by what?
pain impulses in ureters causing a sympathetic reflex back to kidney to constrict renal arterioles thereby decreasing U.O. from kidney.
Important for preventing excessive flow of fluid into pelvis of a kidney w/a blocked ureter
Stimulated when blocked ureters respond with intense reflex constriction which sends sympathetic stimulation back to kidneys to constrict renal arterioles
Ureterorenal Reflex
prevents excessive flow of fluid into pelvis of a kidney w/a blocked ureter
Ureterorenal Reflex
Renal calyces act as what?
pacemaker for peristaltic contraction of smooth muscle forcing urine down into the renal pelvis, down the ureters into the bladder
Increased stretch of calyces increases what rate?
peristaltic rate
Parasympathetic innervation does what to peristalsis (peristaltic contractions in Ureter)?
enhances peristalsis (peristaltic contractions in Ureter)
sympathetic innervation does what to peristalsis (peristaltic contractions in Ureter)?
inhibits peristalsis (peristaltic contractions in Ureter)
The normal tone of the detrusor muscle does what?
Prevents backflow from bladder to ureters, aka REFLUX, esp when a person builds up in bladder during micturition or bladder compression (aka esp during bladder contraction)
If ureter is not long enough to pass through wall of bladder, what will occur?
reflux
Peristaltic waves down/along ureter increases pressure within ureter to do what to bladder?
to open passage to bladder
so region passing through bladder wall opens and allows urine to flow
Urination occurs when inhibitor signals are stronger than what signals to do what?
voluntary constrictor signals being sent to external sphincter
Micturition contractions stimulated by what?
stretch receptors/reflex, initiated by sensory stretch receptors in bladder wall
Provides positive feedback to stretch receptors resulting in further increase in pressure
What are micturition contractions ?
Tonic pressure changes during filling of the bladder, periodic acute increase in pressure that last sec-min, caused by micturition reflex.
As bladder fills more and more what happens to the micturition reflex?
inhibited time decreases (more frequent contractions) and resulting contractions become more powerful
Once micturition reflex is strong enough it stimulates inhibitor signals to where?
the external sphincter
Once Micturition Reflex begins it is what?
“Self regenerative”
initial contraction activates stretch receptors to cause a greater increase in sensory impulses, cycle of contractions repeat until there is a strong degree of contractions
After a while it starts to fatigue and permits bladder relaxation for some time and than starts again.
Internal sphincter–tone
holds urine in bladder
smooth muscle
External sphincter
–skeletal muscle
–voluntary control by nervous system
–conscious prevention of urination
