Unit 4: Renal Physiology Pt 1 Flashcards
What type of organ is the kidney?
Excretory
Regulatory
Endocrine
How are the kidneys excretory organs?
- excrete harmful substances
- excrete things that are in excess
How are the kidneys regulatory organs?
- maintain constant volume
- maintain constant composition
- regulate pH
How are the kidneys endocrine organs?
synthesizes and secretes at least three major hormones
What are the three major hormones the kidney synthesizes and secretes?
- Rening
- Erythropoietin
- 1,25-dihydroxycholecalciferol (aka Calcitriol)
What does renin that is secreted by the kidney, stimulate?
stimulates angiotensin II formation and aldosterone secretion
What does Erythropoietin that is secreted by the kidney, stimulate?
stimulates production of RBCs
What effect does calcitriol (1,25-dihydroxycholecalciferol) have?
widespread effects including Ca++ absorption from the GI tract
- enhances immune function
(will increase Ca++ and Phosphate in ECF)
What is the role of the renal system? (8)
- Filtration, reabsorption, Secretion, Excretion
- Water/electrolyte balance
- pH regulation (HCO3-)
- Control of circulating volume (BP control)
- Hormone secretion (renin, erythropoitin, calcitriol)
- site of hormone action
- gluconeogenesis
- dopamine production
What does the kidney excrete for us?
Rid body of water soluble wastes
- urea
- creatine
- uric acid
- other water soluble metabolites
Eliminate toxins and foreign substances
- drugs
- pesticides
- additives
What organ makes things more water soluble and therefore capable of being secreted?
the liver
What do the kidneys keep electrolyte balance of?
water intake = water output
sodium intake = sodium output
sodium/potassium balance
Does the kidney have a role in glucose regulation?
yes
- reabsorption of virtually all
- uptake of glucose for its own needs
- gluconeogenesis
- glycogenolysis
In general, do we excrete or reabsorb most glucose? Where does this occur?
reabsorb most glucose in Proximal Convoluted Tubule
Does the kidney uptake glucose for its own Energy needs dependent or independent of insulin?
independent of insulin
“BRICKLE”
Can the kidney perform gluconeogenesis? If so, from what? When would this be more active?
yes; create glucose from:
- A.A.s (alanine)
- glycerol
- lactate
during periods of prolonged fasting
Where are the kidneys located when standing? What space are they in?
L1-L4
in retroperitoneal space = space behind the peritoneum
What does the Medulla of the kidney contain?
- 8-10 renal pyramids (top is called papilla)
- major calyces
- minor calyces
What contracts in order to propel urine to bladder?
calyces, renal pelvis, and ureter
What type of innervation does the kidney receive? How does it get to the kidney?
Sympathetic preganglionic fibers from T10-L2
Sympathetic postganlgionic fibers to kidney via Renal Plexus
What do the sympathetic postganglionic fibers project to in the kidney?
individual nephrons
What will SNS stimulation have on the nephrons? What will this cause?
- signals for CONSTRICTION of arterioles–> therefore decrease filtration rate and decrease urinary output
- can also signal kidney to: increase Na+ reabsorption and increase renin release
What effect does SNS stimulation have on renin?
causes renin release–> stimulate RAAS–> (causes aldosterone release at the end which will tell kidney to take in more Na+, therefore bring H2O with and increase BP)
What percentage of cardiac output do the kidneys use at rest?
22%
What makes the blood flow of the kidneys unique?
2 sets of capillary beds and 2 sets of arterioles in series
List the arterial blood flow of the kidney starting from the renal artery.
renal artery interlobar arteries arcuate arteries cortical radial arteries afferent arterioles glomerular capillaries efferent arteriole peritubular capillaries
What do afferent arterioles give rise to? What do efferent arterioles give rise to?
glomerular capillaries (drained by efferent arterioles)
peritubular capillaries
What capillaries of the kidney is where filtraiton takes place? What about reabsorption and secretion?
filtration –> at glomerular capillaries
reabsorption–> at peritubular capillaries
What keeps glomerular capillary filtration pressure constant?
efferent arteriole
What type of pressure does the Glomerular capillaries have? What about the Peritubular capillaries? Why?
Glomerular–> high hydrostatic pressure (45 mmHg); causes rapid fluid filtration*
Peritubular–> lower hydrostatic pressure (13 mmHg); allows for rapid fluid reabsorption*
List the order of blood flow out of the kidney beginning with the peritubular capillaries.
peritubular capillaries interlobar vein arcuate vein interlobar vein renal vein
What is the functional unit of the kidney? About how many are in each kidney?
the nephron; ~800,000 - 1,000,000
What are the two types of nephrons? Which do we have more of? Where are their glomerulus located?
- Cortical Nephron (85%); glomerulus higher in cortex
2. Juxtamedullary nephron (15%); glomerulus closer to medulla
What makes the Juxtamedullary nephron different than the Cortical nephron?
- glomerulus closer to medulla (instead of high up in cortex)
- sig. longer Loop of Henle
- penetrates deeper into medulla
- capable of concentrating urine*
- associated with Vasa recti
What nephron is capable of concentrating urine?
Juxtamedullary nephron (only ~15% of nephrons)
T/F. We can regenerate new nephrons.
false
What what age is there a decrease in our number of nephrons? What is the measure of the decrease?
after ~ 40 years old there is a decrease
~ 10% loss every 10 years
What percentage of original number of nephrons can we get by with to survive and before kidney failure occurs?
25%
you will die of something else before you die of losing nephrons
What are the Glomerular capillaries encased inside?
Bowman’s capsule
What is the order that fluid is filtered from the glomerular capillaries to the ureter?
Bowman's capsule--> proximal tubule--> loop of Henle--> distal tubule--> connecting tubule--> collecting duct--> renal pelvis--> and out
What type of muscle is the urinary bladder and what are the two main parts?
smooth muscle
- Body–> primary part of bladder where urine collects
- Neck–> passes inf. and ant. from body and attaches to urethra
What is the muscle in the bladder? What type of muscle is it made out of? How are the fibers arranged?
Detrusor mucles; smooth muscle of the bladder
fibers intertwined
Does the Detrusor muscle have a low or high resistance to electrical impulses? What does this allow for?
Low-resistance to electrical impulses b/w ms cells
- action potential can spread quickly–> and whole bladder contracts at once
What will the contraction of the Detrusor muscle increase the pressure by?
by 40-60 mmHg
What is found on the posterior wall of the bladder? What enters at the upper part? What is the surface of it?
the Trigone
- ureters enter bladder at upper trigone
- Surface: smooth ms (other pt of bladder is folded rugae)
How do the ureters enter the bladder? Do they remain open?
obliquely through detrusor muscle and penetrates 1-2 cm through detrusor and mucosa
no, tone of detrusor muscle shuts down the ureters–> preventing backflow of urine
What is the posterior part of the urethra called? What it is composed of?
Bladder Neck Composed of: - detrusor muscle - elastic tissue - internal sphincter
What type of muscle is the internal sphincter of the urinary tract? What does it prevent?
smooth muscle under INvoluntary control
prevents emptying of bladder until pressure rises above the critical threshold
What does the urethra pass through?
What is the external sphincter muscle made up of?
urogenital diaphragm
skeletal muscle–> under voluntary control (can consciously contract to prevent urination)
What innervates the urinary bladder?
- Pudendal nerve
- Sympathetic innervation
- Pelvic nerves
- Sensory and Motor nerve fibers
What innervates the external bladder sphincter? What type of control is this under?
Pudendal nerve; somatic nerve fibers; under voluntary control
What does the urinary bladder receive sympathetic innervation through? What does this stimulate?
via hypogastric nerve (L2)
blood supply to bladder
How does the urinary bladder receive its Pelvic Nerve innervation?
through the sacral plexus
- S2,S3 cord segments
What do the sensory and motor fibers to the urinary bladder do?
sensory–> detect stretch of bladder wall
parasympathetic motor fibers–> innervate the Detrusor muscle
What innervates the Detrusor muscle?
parasympathetic motor fibers
What is the flow of urine starting at the nephron.
Nephron--> collecting ducts--> renal calyces--> ureters--> bladder
When urine flows from the collecting ducts to the renal calyces, what does this cause?
peristaltic contractions that occur in the renal pelvis and ureters–> which forces urine from the kidneys to the bladder
What innervates the ureters? What type of muscle are they?
sympathetic and parasympathetic nerves
smooth visceral muscle
What causes the ureters to increase in contraction? What about decrease?
increase–> due to parasympathetic stimulation (pee)
decrease–> with sympathetic stimulation (store)
What type of fibers do the ureters contain? What happens if there is a kidney stone?
a lot of PAIN fibers–> if severe pain due to kidney stone:
Ureterorenal Reflex occurs
What occurs in when the Ureterorenal Reflex occurs?
Due to severe pain from kidney stone:
- Reflex constriction occurs
- Sympathetic reflex occurs back to the kidney
- -> constrict the renal arterioles
- -> decreases flow of fluid into the kidney with a blocked ureter
What is the process of urinary bladder emptying when it is filled?
micturition
What are the steps to getting the bladder to empty?
- Bladder progressively fills–> tension on bladder walls raises above a threshold level
- Micturition Reflex–> Nervous Reflex
- Urge to Urinate–> external sphincter under voluntary control
- Bladder empties
What controls the Micturition reflex?
ANS–> coordinated by centers in the midbrain
What part of the NS predominates when the bladder is filling? What happens to the detrusor ms and internal sphincter?
SNS control (“stores”)
- relaxation of detrusor muscle (beta2)
- contraction of internal sphincter (alpha1)
(external sphincter closed by trained voluntary action)
What senses a full bladder? Where does this signal get sent?
sensed by mechanoreceptors (stretch receptors) in bladder wall–> spinal cord –> brain stem
What part of NS is stimulated to empty the bladder?
PSNS control (“pee”)
- contraction of detrusor muscle will increase pressure in bladder
- relaxation of internal sphincter (urge to urinate)
(recall: voluntary control to relax external sphincter)
What gives us the urge to urinate?
relaxation of the internal sphincter by the PSNS
What is initiated as the bladder fills with urine? What does this cause?
Sensory stretch receptors (mechanoreceptors) –> micturition contractions
- vary in length of contraction and intensity
- generally increases as more urine added to bladder
What do we call the term for how the Micturition reflex causes initial contracture of the detrusor muscle which causes further activation of the stretch receptors?
Self-regenerative
- further increase in reflex contraction
- this cycle repeats multiple times
- will being to fatigue and bladder relaxes
What happens to the Micturition Reflex is the bladder is not emptied? What happens as the bladder continues to fill?
reflex is inhibited for minutes or hours
continues to fill–> increase in frequency of micturition reflex and intensity of it
What happens as the Micturition reflex increases? Where does the reflex pass?
reflex passes through Pudendal Nerve –> to the external sphincter
then voluntary Relaxation of external sphincter–> and urination occurs
Where are centers located that can facilitate or inhibit urination?
in the pons and cerebral cortex –> usually have FINAL control of micturition
How do the Pons and cerebral cortex impact the micturition reflex while we do not have the desire to urinate? How do they effect the external bladder sphincter?
keep micturition reflex partially inhibited
ext. bladder sphincter is kept tonic contraction
What do the Pons and cerebral cortex do when urination is desired?
cause concurrent micturition reflex and relaxation of external bladder sphincter
What occurs during voluntary urination of the Micturition reflex?
- contraction of abd. ms
- increase pressure in bladder
- increase urine that enters bladder neck (stretch walls and stimulate stretch receptors–initiate micturition reflex)
- empties all (or most) of urine from bladder
