Week 9 Science and Scholarship: Urinary System Flashcards
structure of kidneys
bean shaped paired retroperitoneal organs
list the organs of the urinary system
kidneys, ureters, bladder, urethra
structure of ureters
-muscular paired narrow tubes
-made of transitional epithelium
-has muscularis layer (upper 2/3 have 2 layers lower 1/3 has 3 layers)
structure of bladder
hollow organ
-mucosa, muscularis and sphincters
-3 layers of muscularis
-internal (involuntary) and external (voluntary) sphincters
-
structure of urethra
-tube at terminal end of urinary tract
-stratified transitional epithelium
-goes from columnar to squamous
-2 layers of muscularis
-varies in men (20-25cm) and women (4cm)
list the functions of the kidney
plasma flitration
nutrient conservation
BP regulation
blood pH regulation
hormone release
how is the kidney involved in plasma filtration
removes wastes and excess substances from blood
how is the kidney involved in nutrient conservation
reabsorbs essential nutrients and ions to maintain body balance
how is the kidney involved in BP regulation
regulates BP and volume through fluid balance mechanisms
how is the kidney involved in blood pH regulation
maintains blood pH and BGL via various mechanisms
how is the kidney involved in hormone release
secretes hormones like renin and erythropoietin to regulate BP and RBC production
name the external features of the kidney
renal artery, renal vein, hilum, ureter, renal pelvis
function of renal artery
blood vessel carrying oxygenated blood to the kidney for filtration
function of renal vein
blood vessel carrying filtered blood away from the kidney
function of hilum
indentation on the kidney where the renal artery, renal vein and ureter enter and exit
function of ureter
tube that carries urine from kidney to bladder
function of renal pelvis
central collecting chamber where urine from the kidney nephrons is funnelled before entering the ureter
name the internal features of the kidney
fibrous capsule
perinephric/perineal fat
renal fascia
renal medulla
renal cortex
renal sinus
renal pyramids
renal column
kidney lobes
whats the fibrous capsule of kidney
collagen fibres that cover entire organ
whats the perineal fat of kidney
a thick, cushioning layer of adipose tissue
whats the renal fascia of kidney
dense, fibrous outer layer that anchors the kidney to surrounding structures
whats the renal medulla of kidney
layer beneath the cortex that regulates concentration of urine
whats the renal cortex of kidney
outermost area of kidney
-enables filtration and reabsorption of blood
whats the renal sinus of kidney
central cavity that contains renal pelvis, renal calyces, blood vessels and fat
whats the renal pyramid of kidney
cone structures that extend from the cortex to renal sinus,
-8 to 10 per kidney
-transport urine from cortex to sinus
-apex is known as renal papilla
what is the renal columns of kidney
bands of tissue that seperate adjacent renal pyramids
whats the kidney lobes of kidney
consists of a renal pyramid, overlying renal cortex and adjacent tissues of renal columns
List the pathway through which filtrate drains from each kidney lobe into ureter
renal papilla
minor calyces
major calyces
renal pelvis
ureter
function of ureter
transports urine from the kidney to urinary bladder
function of bladder
storage and expulsion of urine
function of urethra
transport urine from bladder to outside of Body
Describe the pathway of blood flow through the kidney (up until nephron)
-oxygen rich blood arrives via renal artery
-renal artery divides into renal sinus and segmental arteries
-segmental arteries branch into interlobar arteries which run along columns
-interlobar arteries continue to branch, until they culminate at the nephron level
Describe the pathway of blood flow through the kidney (nephron onwards)
-the efferent arteriole carries blood from the glomerulus to peritubular capillaries
-the peritubular capillaries surround the renal tubule, water and solvents are absorbed
-peritubular capillaries drain into cortical veins which carry filtered blood back to heart via IVC
Explain the role of peritubular capillaries and vasa recta in filtering blood
-peritubular capillaries surround renal tubules and are vital to reabsorbing substances eg glucose and AA’s into blood
-vasa recta run along side the loop of Henle, they maintain the concentration gradient, vital for concentration of urine
-both structures are very permeable
contrast the types of nephrons
-cortical nephrons are found in the renal cortex whereas juxtamedullary nephrons have longer loops and extend into renal medulla
-cortical nephrons excrete waste products into urine whereas juxtamedullary nephrons concentrate urine
name the structural components of the nephron
-PCT
-Loop of Henle
-DCT
-collecting ducts
function of the proximal convoluted tubule (PCT)
extends from the Bowmans capsule and is essential in reabsorption of nutrients eg glucose, amino acids, ions and water
function of loop of henle
consists of ascending and descending limbs, creates a osmotic gradient in the medulla for water and ions reabsorption
function of distal convoluted tubule (DCT)
further modifies filtrate by selectively reabsorbing ions eg Na,K,Ca (regulate pH)
function of collecting duct
receives filtrate form multiple nephrons and concentrates urine , sending to renal pelvis for elimination (electrolyte balance)
name the 3 functions of the nephron
filtration, reabsorption and secretion
Describe filtration and where it occurs
occurs at renal corpuscle, solutes within the blood pass through filtration membrane into nephron due to hydrostatic pressure
Describe reabsorption and where it occurs
occurs at tubules, transport of water and solutes from tubular fluid into the peritubular fluid
other name for tubular fluid
filtrate
other name for peritubular fluid
blood
Describe secretion and where it occurs
occurs at collecting ducts, solutes (wastes or drugs) are transported from the tubular fluid into peritubular fluid
what makes up the renal corpuscle
glomerulus and bowman’s capsule
function of glomerulus
a tuft of capillaries, where small molecules pass through and larger proteins and cells are retained
function of Bowmans capsule
surrounds glomerulus and collects filtrate, forcing it to renal tubules for further processing
what is the filtration membrane
site of filtration of blood from the glomerulus into the glomerular capsule
Name the features that enhance glomerular filtration at the renal corpuscle
Glomerular pressure
capillary surface area
membrane thickness
how does glomerular pressure enhance glomerular filtration
-afferent arterioles have lower blood pressure than efferent arterioles
-t/f blood is drawn into glomerulus via afferent pathways and exported via efferent pathway
how does capillary surface area enhance glomerular filtration
-the glomerular capillaries have a high surface area, enabling the rapid transport of filtrate
how does membrane thickness enhance glomerular filtration
the filtration membrane is thin, this enables the rapid transport of materials cross it
name the three components of the filtration membrane
fenestrated endothelium
basement membrane
pedicels
function of fenestrated endothelium in filtration membrane
contains fenestrations; this allows some substances to flow through, and prevents the flow of larger substances
function of basement membrane in filtration membrane
prevents the travel of large portions
function of the pedicels in the filtration membrane
filtration sits between pedicels (of podocytes), prevents the transport of medium proteins into the nephron
list the purposes of mesangial cells in the renal corpuscle
structural support
phagocytosis
cytokine secretion
how do mesangial cells provide structural support to renal corpuscle
-provide structural support to the glomerular capillaries and maintain integrity of glomerular tuft
-help prevent collapse and maintain SA
why do mesangial cells allowing phagocytosis aid renal corpuscle
-they can remove debris, engulf immune complexes and other debris that may accumulate in glomerulus
how do cytokine secretions by mesangial cells aid renal corpuscle
-can secrete various cytokines and growth factors that are involved in tissue repair and immune responses of glomerulus
Distinguish between the microscopic appearance of the renal corpuscle and the renal tubules
Renal corpuscle:
-spherical
-glomerulus is tightly packed, has a parietal and visceral layer
-parietal layer is squamous epithelium and visceral layer is podocytes
Renal tubules:
-long
-PCT (contain microvilli) & DCT are convoluted structures with single epithelial lining
-collecting ducts are larger and can have cuboidal or columnar lining
how does concentration of urine work according to the counter-current multiplier mechanism
works between the loop of henle and vasa recta
-descending loop of henle is permeable to water and ascending loop is permeable to ions
-water follows salt and they enter interstitial fluid
-this establishes a concentration gradient
-higher concentration in renal medulla
-water can be reabsorbed at ducts and instead urine is more concentrated
ADH and aldosterone make urine ___ concentrated
more
Describe the influence of the Anti-Diuretic Hormone (ADH) on the renal tubules and collecting ducts
-low water level or high osmolarity (stimulus)
-specialised cells of hypothalamus detect a change in blood osmolarity or concentration
-ADH released by pituitary gland and acts on kidneys to increase water reabsorption
-less water loss (more concentrated urine)
Describe the influence of Aldosterone on the renal tubules and collecting ducts
-mineralocorticoid receptors in tubules and ducts are stimulated
-aldosterone released & stimulates reabsorption of Na+ from collecting ducts
-more water is also reabsorbed as it flows salt
-increased blood volume and BP
-also, K+ is excreted into filtrate to maintain potassium levels
list the components of the juxtaglomerular apparatus
juxtaglomerular cells
macula densa
mesangial cells
extraglomerular mesangial cells
what are juxtaglomerular cells and what do juxtaglomerular cells do in the juxtaglomerular apparatus
-specialised smooth muscle cells in the walls of the afferent arteriole where it comes in contact with glomerulus
-secrete enzyme renin
what is macula densa and what does macula densa do in the juxtaglomerular apparatus
-group of specialised cells in DCT, close to juxtaglomerular cells
-detects sodium chloride concentration in tubular fluid
what are mesangial cells and what do mesangial cells do in the juxtaglomerual apparatus
-supporting cells located between the glomerular capillaries
-help regulate blood flow in glomerulus and support its structure
what are extraglomerular mesangial cells and what do extraglomerular mesangial cells do in the juxtaglomerual apparatus
-cells found in space between afferent and efferent arterioles
-communicate with juxtaglomerular cells and macula densa cells, regulating the glomerulus
define the term diuretic
a medication or substance that increases urine production and excretion from the body
list some common diuretic
caffeine
alcohol
watermelon
cranberries
marijuana
MDMA
nicotine
celery
list three metabolic waste products found in urine
urea, creatine and uric acid
how does BP influence glomerular filtration rate
-when BP increases, afferent arterioles contract, limiting amount of blood flow into glomerular capillaries
-when BP decreases, affect arterioles dilate, increasing amount of blood flow into glomerular capillaries
Explain the concept of haemodynamic regulation of glomerular filtration
-GFR is regulated by blood flow and pressure within glomerular capillaries
involves:
auto regulation of renal blood flow
hormonal regulation of renal blood flow
podocyte contraction
List the primary determinants of GFR
glomerular capillary pressure
renal blood flow
glomerular SA
permeability of filtration barrier
how does glomerular capillary pressure impact GFR
if pressure is too high, more fluid will be filtered than necessary and if its too low less fluid will be filtered
how does renal blood flow impact GFR
-the amount of blood flow into the kidney determines the amount of fluid that is filtered by the glomerulus, if renal blood flow decreases GFR decreases
how does glomerular SA impact GFR
decreased SA (due to damaged glomerular capillaries) , decreases GFR
how does permeability of filtration barrier impact GFR
-permeability determines the quantity of substance that can be filtered, increased permeably increases GFR
outline how GFR is estimated
-using equations that consider age, sex, race and serum creatine levels
what is the most common way of estimating GFR
chronic kidney disease epidemiology collaboration
CKD-EPI
most accurate way of determining GFR
using clearance of exogenous filtration markers
name the ways to measure GFR
CKD-EPI equations
blood tests
creatine clearance
clearance of exogenous filtration markers
Explain inulin clearance
performed using timed urine and blood collections, with insulin clearance calculated as the amount of insulin cleared from blood over set time
why is inulin clearance useful clinically
-insulin can not be reabsorbed or secreted
-used to monitor CKD, medications and dialysis
Explain the concept of ‘first-pass metabolism as it applies to inulin clearance.
-first-pass metabolism is the initial metabolism of a substance that occurs when its absorbed from GI tract and passes through liver before entering systemic circulation
-insulin exogenously administered, bypassing GI tract and liver, meaning its filtered rapidly
-insulin clearance isn’t impacted by first pass metabolism as it doesn’t undergo hepatic metabolism before entering systemic circulation
name the broad categories of drugs that influence the urinary system
-loop diuretics
-Thiazide Diuretic
-Mineralocorticoid antagonist
-Potassium-sparing diuretics
-Angiotensin Converting Enzyme inhibitors (ACE inhibitors)
-Angiotensin Receptor Blockers (ARB
describe the action of loop diuretics
inhibit the sodium-potassium-chloride co-transporter in renal tubules, reducing reabsorption of sodium, chloride and water in the ascending loop of henle
describe the action of thiazide diuretics
inhibit the sodium-chloride co transporter (NCC) in renal tubules, reducing reabsorption of sodium and chloride
describe the action of mineralocorticoid antagonists
block the effects of aldosterone, reducing sodium and water retention
describe the action of potassium-sparing diuretics
inhibit sodium channels or sodium-potassium exchange pumps, reducing sodium reabsorption and potassium secretion
describe the action of ACE inhibitors
block the action of angiotensin converting enzymes, reducing the conversion of angiotensin I into angiotensin II
describe action of angiotensin-receptor blockers
block angiotensin II receptors, preventing its vasoconstrictor and aldosterone-stimulating effects
effect of loop diuretics
increased urine volume and excretion of sodium and other electrolytes
effect of thiazide diuretic
increased urine volume, excretion of sodium and chloride, modest decrease in potassium secretion
effect of mineralocorticoid antagonist
increased sodium and water excretion, while reducing potassium excretion
effect of potassium-sparing diuretics
increased urine volume, with. minimal potassium loss
effect of ACE inhibitors
vasodilation, decreased aldosterone secretion, reduced sodium and water reabsorption, lower BP and lower blood volume
effect of angiotensin receptor blockers
vasodilation, decreased aldosterone secretion, reduced sodium and water reabsorption,
what is intracellular fluid
the fluid that is found inside cells, and is separated from the extracellular fluid by the -PCM (2/3 body fluid)
-high [K+]
what is extracellular fluid
the fluid that is found outside cells, includes interstitial fluid, plasma and lymph
what is plasma
liquid component of the blood, that contains water, electrolytes, hormones, proteins, and other substances
-is separated from the formed elements of blood by the cellular components of blood
-(1/15th body fluid)
-high [Na+]
what is interstitial fluid
fluid that surrounds and bathes cells, and is found in the spaces between cells and capillaries in tissues
how can fluid gain occur
-oral intake of water or consumption of water rich food
-metabolic processes produce water as a byproduct
how can fluid loss occur
-through urine, perspiration, respiratory evaporation
Outline the pathway for ADH in regulation of blood volume
-ADH is released by pituitary gland in response to stimulation by osmoreceptors of the hypothalamus (low water levels)
-ADH acts on kidneys to increase water reabsorption
-concentrated urine and less water loss
Describe alkalosis
a condition characterised by an excess of base in the blood resulting in pH > 7.45
Describe acidosis
a condition characterised by an excess of acid in the blood resulting in pH < 7.45
causes of alkalosis
hyperventilation (lower CO2) t/f high pH
symptoms of alkalosis
muscle twitching, numbness, or tingling
causes of acidosis
-hypoventilation (high CO2) t/f low pH
-kidney disease or diabetics
symptoms of acidosis
lethargy, SOB, cephalgia
where are peripheral chemoreceptors
carotid sinus and aortic arch
where are central chemoreceptors
medulla
Explain the role of the juxtaglomerular apparatus response in regulating BP
-the macula densa (in the DCT) detects decrease in the NaCl concentration in the urine
-macula densa stimulates release of renin by JG cells
-this acts on afferent arterioles
-causing vasoconstriction and decreased GFR
-less Na and water is excreted and reduces urine production
Explain the role of the Renin-Angiotensin-Aldosterone System (RAAS) in the control of blood pressure and electrolyte balance.
-specialised cells in JGA detect low Na+ or low BP and secretes renin
-renin acts on angiotensinogen and converts it into angiotensin I
-angiotensin I is further converted to angiotensin II by ACE
-angiotensin II stimulates release of aldosterone from adrenal glands, causing vasoconstriction of efferent arterioles
-aldosterone acts on DCT and collecting ducts, promoting sodium reabsorption and potassium excretion
-increased sodium reabsorption, increased water reabsorption and blood volume
-negative feedback loops work and Renin is inhibited
the thirst response is regulated by ___
osmoreceptors of hypothalamus
Describe the micturition reflex
-receptors in the wall of the bladder detect stretch and send a signal to spinal chord (via a neuron)
-detrusor muscles surrounding the bladder contract, causing the bladder to ‘squeeze’ urine out
-the internal sphincter relaxes enabling urine to exit the bladder and enter the urethra
-an afferent signal is sent to brain, which processes the response and sends efferent signal to urethra
-external sphincter relaxes or contracts depending on desired outcome
what steps are voluntary and involuntary in micturition reflex
1,2,3 Involuntary
4,5 voluntary
volume of bladder
700-800 mL
at what volume does the urge to urinate begin
200mL
Describe the voluntary and involuntary regulation of urination with reference to appropriate sphincters
-at 200mL there is a voluntary urge to urinate
-at 500mL detrusor muscle contraction forces the internal (involuntary) sphincter to open
-if neurological pathway for external voluntary sphincter hasn’t been established urination occurs involuntarily (Infants)
-if external voluntary sphincter isn’t powerful enough, urination can occur (elderly)
what input does the bladder receive
-receives both parasympathetic and sympathetic input
-spin reflex
describe autonomic innervation of bladder
Consists of detrusor muscle, external and internal sphincter
-detrusor muscle is contracted during urination and receives parasympathetic input
-internal sphincter is relaxed during urination and receives reduced sympathetic outflow
-external sphincter is relaxed during urination and receives somatic nervous innervation
name the three systems that control the micturition reflex
cortical centres
brainstem
spinal chord
how are cortical centres involved in the micturition reflex
-CC in cerebral cortex, provides voluntary control over the inhibition and initiation of micturition through conscious decision making
micturition reflex aka
void reflex
how is the brainstem involved in micturition reflex
-consists of pontine micturition centres and periaquaductal grey (PAG)
-coordinates reflexive aspects of the reflex, involving the coordination between the bladder and external urethral sphincter
how is the spinal chord involved in micturition reflex
-serves as the final integration centre for the reflex
-receives sensory information from the bladder and coordinates the reflex arc that mediates the coordinated contraction of the detrusor muscles and relaxation of external urethral sphincter during voiding
contrast parasympathetic and sympathetic innervation of bladder
-parasympathetic NS contracts detrusor muscles, relaxes internal sphincter and promotes bladder function
-sympathetic NS relaxes detrusor muscles, contract internal sphincter and inhibits bladder function
where does sympathetic innervation of urinary bladder begin and what ganglion are relevant
-thoracolumbar region T10 to L2
-superior hypogastric plexus and inferior mesenteric ganglia
where does parasympathetic innervation of urinary bladder begin and what ganglion are relevant
-sacral region S2-S4
-intramural ganglia in the bladder wall
whats a UTI
bacteria in upper or lower urinary tract
-upper (kidneys and ureter) are more serious
whats a kidney stone
crystallisation of minerals and salts
-painful, more common in men
define acute vs chronic renal failure
Acute is sudden and rapid decline in kidney functions vs chronic is progressive and irreversible loss of kidney function over time
onset of acute vs chronic renal failure
acute develops rapidly within hours to days vs chronic develops gradually, months to years
cause of acute vs chronic renal failure
acute occurs due to sudden injury, infection or dehydration vs chronic occurs due to diabetes, HTN, kidney diseases
symptoms of acute vs chronic renal failure
acute leads to decreased urine output and fluid retention vs chronic leads fatigue, oedema, HTN and anaemia
treatment of acute vs chronic renal failure
acute focuses on cause of condition and supporting kidney function vs chronic may need management, dialysis or transplants
are acute and chronic renal failure reversible
generally, only acute is reversible
name two types of dialysis
peritoneal and haemodialysis
whats heamodialysis
a haemodialyser (machine) is used to withdraw, filter and then return pt blood into bloodstream
whats peritoneal dialysis
-involves use of peritoneal membrane in patients abdomen as natural filter
-dialysate solution is injected via catheter
-dialysate absorbs fluids and wastes from blood vessels lining peritoneal membrane
-after a period of time, dialsyate is drained and replaced
what are aquaporins
provide a mechanistic explanation for polyuria in diabetes
Increased Blood Glucose Levels
Glucose Spillage into Urine
Osmotic Diuresis: glucose in the urine increases its osmotic pressure. This high osmolarity pulls water from the bloodstream into the urine.
Increased Urine Volume:
Polyuria:
what are the microvascular and microvascular complications of diabetes
microvascular=retinopathy,nephropathy,neuropathy
macrovascular= stroke, MI, CVD
symptoms of retinopathy
-blurred vision, dark spots, decreased night vision, vision loss
symptoms of nephropathy
oedema, HTN, fatigue, anaemia, loss of appetite
symptoms of neuropathy
sharp pain, tingling, numbness, loss of reflexes
what kind of medication is ramipril
an ACE inhibitor
how do statins work
Statins lower cholesterol by blocking liver enzyme, reducing “bad” cholesterol and lowering risk of heart disease and stroke.
