Urology & Renal Flashcards
What is the urinary system composed of?
Kidneys, ureters, bladder, and the urethra
What are the main functions of the kidney?
Excretion of metabolic products such as urea, uric acid, creatinine
Excretion of foreign substances
Homeostasis of bodily fluids, electrolytes, and acid-base balance
Regulates blood pressure
Secretes hormones such as erythropoietin and renin
What are the anatomical structures of the kidney?
Cortex, medulla, minor calyx, major calyx, ureter, renal artery, and renal vein
Where does the urine once formed, travel through in the kidney?
Minor calyx to the Major calyx and then through the ureter
What are the functions of the peritubular capillaries?
Provide oxygen and nutrients to the nephron to allow them to perform their functions
Help in reabsorption of different substances along the nephron and then take it away to the circulatory system
Help in secretion of different substances into the tubular fluid
What is the function of the detrusor muscle?
Contracts to build pressure in the urinary bladder to support urination
What does stretching of the trigone to its limit lead to?
Signals sent to the brain about the need for urination
Is it the internal or external sphincter that gives involuntary control to prevent urination?
Internal sphincter - must be relaxed for urination to proceed
External sphincter gives voluntary control to prevent urination
What is the function of the bulbourethral gland?
Produces thick lubricant which is added to watery semen to promote sperm survival
What are the 2 different cell type classes in the collecting duct and describe their mitochondria density?
Principal cells - Low density of mitochondria
Intercalated cells - High density of mitochondria
What are the anatomical differences between the juxtamedullary and superficial nephrons?
The glomerulus of the superficial nephron is in the upper cortex of the kidney, whereas the juxtamedullary nephron has its glomerulus closer to the medullary border
The Loop of Henle in the superficial nephron only extends to the outer medulla, whereas the one in the juxtamedullary nephron extends into the inner medulla
Why does the cortex have a granular appearance, whereas the medulla has a striated appearance?
The loop of Henle extending through the medulla gives it its striated appearance
What are the 3 cell types making up the juxtamedullary apparatus?
Extraglomerular mesangial cells, macula densa (distal convoluted tubule), and juxtaglomerular cells (afferent arteriole).
What are the main functions of the juxtaglomerular apparatus?
GFR regulation through tubular-glomerular feedback mechanism
Renin secretion for regulating blood pressure
What are the 4 main renal processes?
Glomerular filtration
Reabsorption
Secretion
Excretion
Is glomerular filtration a passive or active process?
Passive
Describe the permeability of the filtration barrier
Highly permeable to fluids and small solutes
Impermeable to cells and proteins
What is the name of the spaces between capillary endothelium and how big are they?
Fenestrae
70nm in diameter
What substances can pass through fenestrae?
Water, ions, and small proteins
What substances can pass through the slit diaphragm of the glomerular basement membrane?
Water and small solutes only
What are podocytes?
Highly specialized cells of the kidney glomerulus that wrap around capillaries and that neighbor cells of the Bowman’s capsule
What is the name of the ‘pulling’ pressure exerted by the solutes?
Oncotic pressure - fluid molecules are drawn in across a semipermeable membrane
What is the name of the force that causes the glomerular filtration from the glomerulus into the Bowman’s capsule?
Hydrostatic pressure from glomerular capillaries
How do you calculate the net ultrafiltration pressure?
Puf = HPgc - HPbw - πgc
Puf - Net ultrafiltration pressure
HPgc - hydrostatic pressure in glomerular capillaries
HPbw - hydrostatic pressure in bowman’s capsule
πgc - Oncotic pressure of plasma proteins in glomerular capillaries
What is meant by the glomerular filtration rate and how do you calculate it?
Amount of fluid filtered from the glomeruli into the Bowman’s capsule per unit time (ml/min)
GFR = Puf x Kf
Kf - ultrafiltration coefficient (membrane and surface area available for filtration)
What is the GFR for a healthy male and female respectively?
Male -> 90-140ml/min
Female -> 80-125ml/min
What does a fall in GFR show about the excretory products in the plasma?
That there is an increase in the excretory products in the plasma
Describe the myogenic mechanism used to regulate the GFR when arterial pressure is high
Arterial pressure increases Afferent arteriole stretches Arteriole contracts Vessel resistance rises Blood flow reduces GFR stays the same
Describe the tubuloglomerular feedback mechanism used to regulate the GFR
Increase/Decrease in GFR
Increased/Decreased NaCl in Loop of Henle
Change is detected by macula densa
Increased/Decreased ATP and adenosine discharged
Afferent arteriole constricts/dilates
Blood flow decreases/increases
GFR stabilizes
What is meant by renal clearance?
Number of liters of plasma that are completely cleared of the substance per unit time
Therefore it is only concerned with the excretory role of the kidneys
How would you calculate renal clearance?
C x P = U x V therefore C = (U x V)/P ml/min C = Renal Clearance U = Concentration of substance in urine V - Rate of urine production P = Concentration of substance in plasma
If a substance is only filtered in the kidneys and not reabsorbed or secreted, then what value is the GFR the same as?
Renal clearance
Give an example of a molecule that is only filtered and so it follows this principle?
Inulin
Since inulin is not found in mammals, what must be done?
Transfuse it
How can creatinine be used to assess renal function?
If renal function is stable, the creatinine amount in urine is stable
Low creatinine clearance or high plasma creatinine may indicate renal failure
Why is creatinine not the ideal molecule like inulin and why is it still commonly used despite this?
It is secreted in small amounts into the nephron
However, the process for estimating creatinine in the blood and urine can account for that to allow for GFR calculations
What is the renal plasma flow?
The volume of plasma that reaches the kidney (afferent arteriole) per unit of time.
If the total amount of a molecule entering the kidney equals the amount excreted, then the renal clearance of this molecule is the same as the renal plasma flow
What molecule is used to measure the renal plasma flow?
Para aminohippurate (PAH) - all of it is removed from the plasma passing through the kidney through filtration and secretion
What is meant by the filtration fraction and how is this calculated?
The ratio of the amount of filtered plasma that arrives via the afferent arteriole.
FF = GFR/RPF
e.g - a value of 0.15 implies that 15% of the plasma has been filtered
What is the difference between primary and secondary active transport?
Primary - Uses ATP directly to transport molecules in and out of the cell
Secondary - Movement of one solute along its electrochemical gradient provides energy for the other solute to move against its own electrochemical gradient
Is endocytosis a primary or secondary active transport mechanism?
Primary - small proteins are reabsorbed in the PCT using an ATP molecule
Explain how the Na+-Glucose symporter works
Na+ moves down its electrochemical gradient into the cell
This provides the energy to transport glucose against its electrochemical gradient into the cell
Na+ and glucose move in the same direction
Explain how the Na+/H+ antiporter works
Na+ moves down its electrochemical gradient into the cell
This provides energy to actively transport H+ against its electrochemical gradient out of the cell
Na+ and H+ move in opposite directions
In the epithelial cell layer of the renal tubules, how does water follow the transcellular pathway (substances move through the cells from the basolateral side to the apical side and vice-versa)?
It is transported from tubular fluid → Epithelial cells → blood via aquaporins in the epithelial cells
How does transcellular Na+ reabsorption occur in the renal tubules?
3Na+ is transported from epithelial cells into the blood via Na+/K+ ATPase
This creates a concentration gradient for Na+ as it is lower in the epithelial cell so Na+ from the tubular fluid diffuses into the cell
2 K+ is transported from the blood into epithelial cells via Na+/K+ ATPase so this is an active transport as ATP is used
What is meant by the paracellular pathway in the renal tubules?
Substances such as water, Ca2+, K+, Cl- and urea are transported through the tight junctions between the epithelial cells
How does Na+ and Bicarbonate reabsorption occur in the early proximal convoluted tubule?
Na+/K+ ATPase creates a low Na+ concentration in the epithelial cell
CO2 enters the epithelial cell by diffusion and binds to H20, catalyzed by carbonic anhydrase to form bicarbonate and H+
Na+/H+ antiporter then transports Na+ down its concentration gradient into the cell from tubular fluid and H+ out into the tubular fluid against its concentration gradient using the energy from the transportation of Na+
Na+/HCO3- symporter transports Na+ down its concentration gradient into the blood and bicarbonate is transported into the blood against its concentration gradient using energy from the transportation of Na+
How does Angiotensin II regulate the Na+ reabsorbed?
By increasing the number of Na+/H+ antiporters
How does glucose reabsorption occur in the early proximal convoluted tubule?
Na+/K+ ATPase creates a concentration gradient with less Na+ in the epithelial cell Na+/Glucose symporter (SGLT2) transports Na+ from the tubular fluid into epithelial cells and this provides energy to transport glucose against its concentration gradient from the tubular fluid into the epithelial cell Glucose transporter (GLUT2) transports glucose into the blood from the epithelial cell via facilitated diffusion
Explain the general processes of reabsorption involving the Loop of Henle
Na+ and Cl- passively leave the thin ascending limb into the medulla and leaves actively from the thick ascending limb actively
This creates a low water potential in the medulla and so water leaves through the descending limb passively
Describe and explain the osmolarity of the tubular fluid in the different parts of the loop of Henle
At the point where the descending limb enters the ascending limb, the tubular fluid is hyperosmolar as water has been passively reabsorbed from the descending limb but since it is impermeable to Na+ and Cl-.
At the tip of the thick ascending limb, the tubular fluid is hypoosmolar as the salt has been reabsorbed far more
How does Na+ and Cl- reabsorption in the thick ascending limb of the Loop of Henle occur?
Na+/K+ ATPase creates a concentration gradient with a low concentration in the epithelial cell
Na+/K+/2Cl- symporter transports these ions from the tubular fluid into the epithelial cell
K+ is recycled back out into the tubular fluid
K+/Cl- symporter allows reabsorption of these ions from the epithelial cell into the blood
How does Na+ and Cl- reabsorption occur in the early distal convoluted tubule?
Na+/K+ ATPase creates a concentration gradient with a low concentration in the epithelial cell
Na+/Cl- symporter transports Na+ and Cl- into the epithelial cell from the tubular fluid into the epithelial cell
K+/Cl- symporter then transports the K+ and Cl- from the epithelial cell into the blood
Is the early distal convoluted tubule permeable to water?
No
How does active Ca2+ reabsorption occur in the early distal convoluted tubule?
Na+/K+ ATPase creates a concentration gradient with low concentration in the epithelial cell
Na+/Ca2+ antiporter transports Na+ into epithelial cell from the blood and Ca2+ is transported from the epithelial cell into the blood against its concentration gradient
Ca2+ ATPase pump transports Ca2+ against its concentration gradient as well into the blood from the epithelial cell
How do the principal cells work to correct hyperkalemia?
By transporting the K+ out of the epithelial cells and into the tubular fluid
Is the later part of the distal convoluted tubule permeable to water?
Yes, it has aquaporins
How does aldosterone increase Na+ reabsorption?
By increasing the apical Na+ channels and basolateral Na+/K+ ATPase pumps
How does ADH increase water reabsorption?
Increases the apical aquaporins
Basolateral aquaporins are almost always present
How do Na+ reabsorption and K+ secretion occur in the principal cells of the distal convoluted tubule and collecting duct?
Na+/K+ ATPase creates a concentration gradient with low concentration in the epithelial cell so that Na+ is reabsorbed
K+ is transported into the epithelial cell from the blood and so it is secreted actively
How do the alpha and beta intercalated cells of the distal convoluted tubule and collecting duct maintain an acid-base balance?
The alpha intercalated cells facilitate HCO3- reabsorption and H+ secretion, whereas the beta intercalated cells facilitate HCO3- secretion and H+ reabsorption
Alpha intercalated cells have Cl-/HCO3- antiporters on the basolateral side, whereas beta intercalated cell have them on the apical side
Then the H+ ATPase pump is on the apical side on the alpha intercalated cells and on the basolateral side on the beta intercalated cells
These two cell types work together to act as a buffer to changes in pH
What are the consequences of kidney failure?
Filtration failure
Unwell with an accumulation of waste substance
Haematuria and proteinuria, low serum protein,
including albumin in the blood
Hypertension, water retention
Metabolic acidosis
Anemia - lack of erythropoietin production
Vitamin D deficiency and secondary hyperparathyroidism
What is inflammation of the bladder called?
Cystitis
What are some of the non-infective causes of inflammatory urinary disorders?
Metabolic
Diabetic nephropathy
Immunological
Nephritic syndrome
Nephrotic syndromeWhat are the different types of urological disorders?
Inflammatory
Infective
Non-infective
Obstructive
Neoplastic
Developmental/geneticWhat are some of the causes of obstructive urinary disorders?
Stones
Benign prostatic hypertrophy
What are some examples of neoplastic urinary disorders?
Kidney, bladder, prostatic or testicular cancer
What are some developmental or genetic urinary disorders?
Polycystic kidneys, horseshoe kidney
What are some of the potential mechanisms that immune system damage to the kidney might occur?
Through antibodies or inflammatory cells (neutrophils, monocytes, macrophages, or T cells)
What is glomerulonephritis?
The inflammation of the microscopic filtering units of the kidney
What are some of the clinical presentations of immunological disorders?
Nephritic syndrome
Proteinuria
Nephrotic syndrome
Damage to other organs may also be present
How might you go about diagnosing immunological causes of the inflammatory urological disorder?
History and physical examination
Urine Test (urine dipstick, microscopy, and protein:creatinine ratio)
Blood Test (kidney function and immunology tests)
Imaging (start with an ultrasound)
Kidney biopsy
What is a horseshoe kidney?
When 2 kidneys fuse together at the bottom
When does horseshoe kidney occur?
When a baby is growing in the womb as the baby’s kidneys move into place
How may we know if a patient has horseshoe kidney?
Imaging of the abdomen or pelvis
What are the consequences of horseshoe kidneys?
Increased risk of obstruction, stones, and infection
