genitourinary Flashcards
- 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 erythropoeitin and renin
- 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?
- What does stretching of the trigone to its limit lead to?
Detrusor muscle - Contracts to build pressure in the urinary bladder to support urination
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 are the 2 different cell type classes in the distal convoluted tubule and the collecting duct and describe their mitochondria density?
Principal cells - Low density of mitochondria, the main Na+ reabsorbing cells and the site of action of aldosterone K+ sparing diuretics
Intercalated cells - High density of mitochondria, regulation of acid-base homeostasis
- What are the anatomical differences between the juxtamedullary and superficial nephrons?
The glomerulus of the superficial nephron is in the upper cortex, 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 juxtamedullary nephron has its one extending into the inner medulla
- Why does the cortex have a granular appearance, whereas the medulla has a striated appearance?
Loop of Henle extending through the medulla gives it its striated appearance
- What are the main functions of this juxtaglomerular apparatus?
- What forms the juxtaglomerular apparatus?
GFR regulation through tubular-glomerular feedback mechanism
Renin secretion for regulating blood pressure
macula densa on distal convoluted tubule
juxtaglomerular cells
extraglomerular mesangial cells
- What are the 4 main renal proccesses?
Glomerular filtration
Reabsorption Secretion Excretion
- 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?
- What substances can pass through these spaces?
Fenestrae
70nm in diameter
Water, ions and small proteins
- What substances can pass through the slit diaphragm of the glomerular basement membrane?
- What are podocytes?
Water and small solutes only
Highly specialised cells of the kidney glomerulus that wrap around capillaries and that neighbour cells of the Bowman's capsule
- How do you calculate the net ultrafiltration pressure?
Puf = HPgc - HPbw - πgc
Puf - Net ultrafiltration pressure HPgc - hydrostatic pressure in glomerular capillaries HPbw - hydrostatic presure 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
- Describe the myogenic mechanism used to regulate the GFR when arterial pressure is high
Arterial pressure increases, so Afferent arteriole stretches
Ateriole contracts Vessel resistance rises Blood flow reduces GFR stays the same
- Describe the tubulo-glomerular feedback mechanism used to regulate the GFR (if increase, converse for decrease)
Increase in GFR
Increased NaCl in Loop of Henle Change detected by macula densa Increased ATP and adenosine discharged Afferent arteriole constricts GFR stabilises
- What is meant by renal clearance?
Number of litres 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
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?
- Since inulin is not found in mammals, what must be done?
Inulin
Transfuse it It is a plant polysaccharide so we do not have the enzymese to diffuse it, meaning it cannot be taken orally
- How can creatinine be used to assess renal function?
- Why is creatinine not the ideal molecule like inulin and why is it still commonly used despite this?
If renal function is stable, the creatinine amount in urine is stable
Low creatinine clearance or high plasma creatinine may indicate renal failure
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?
Volume of plasma that reaches the kidney (afferent arteriole) per unit time
If the total amount of a molecule entering the kidney equals amount excreted, then the renal clearance of this molecule is the same as the renal plasma flow
- What molecule is therefore used to measure the renal plasma flow?
- What is meant if a substance is freely filtered?
Para aminohippurate - all of it is removed from the plasma passing through the kidney through filtration and secretion
Means they can be found in the ultrafiltrate and plasma at same concentration
- What is meant by the filtration fraction and how is this calculated?
Ratio of amount of plasma filtered, and which arrives via the afferent arteriole is defined by Filtration Fraction
FF = GFR/RPF
- What is the difference betwen primary and secondary active transport?
- Is endocytosis a primary or secondary active transport mechanism?
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
Primary - small proteins are reabsorbed in the PCT using an ATP molecule
- Explain how the Na+Glucose symporter works
- Explain how the Na+/H+ antiporter 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+ moves down its electrochemical gradient into the cell This provides energy to actively transport H+ against its electrochemical gradient out of the cell
- In the epithelial cell layer of the renal tubules, how does water follow the transcellular pathway?
It is transported from tubular fluid → Epithelial cells → blood via aquaporins in the epithelial cells
- In the epithelial cell layer of the renal tubules, how does water follow the transcellular pathway?
It is transported from tubular fluid → Epithelial cells → blood via aquaporins in the epithelial cells
- How does trancellular Na+ reabsorption occur?
3Na+ is transported from epithelial cells into blood via Na+/K+ ATPase
This creates a concn. gradient for Na+ as it is lower in the epithelial cell so Na+ from the tubular fluid diffuses into cell 2 K+ is transported from 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?
- How does Angiotensin II regulate the Na+ reabsorbed?
Substances such as water, Ca2+, K+, Cl- and urea are transported through the tight junctions between the epithelial cells
By increasing the number of Na+/H+ antiporters
- How does Na+ and Bicarbonate reabsorption occur in the early proximal convoluted tubule?
Na+/K+ ATPase creates a low Na+ concn. in the epithelial cell
CO2 enters epithelial cell by diffusion and binds to H20, catalysed by carbonic anhydrase to form bicarbonate and H+ Na+/H+ antiporter then transports Na+ down its concn. gradient into the cell from tubular fluid and H+ out into the tubular fluid against concn. gradient using the energy from transportation of Na+ Na+/HCO3- symporter transports Na+ down concn. gradient into blood and bicarbonate is transported into blood against conc. gradient using energy from transportation of Na+
- How does glucose reabsorption occur in the early proximal convoluted tubule?
Na+/K+ ATPase creates concn. gradient with less Na+ in the epithelial cell
Na+/Glucose symporter (SGLT2) transports Na+ from tubular fluid into epithelial cell and this provides energy to transport glucose against its 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 occurs
Na+Cl- passively leaves thin ascending limb into the medulla and leaves actively from the thick ascending limb
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 however since it is impermeable to Na+Cl-, the fluid is hyperosmolar ( will have a high oncotic pressure)
At the tip of the thick ascending limb, the tubular fluid is hypoosmolar as the salt has been reabsorbed far more
- How does Na+Cl- reabsorption in the thick ascending limb of the Loop of Henle occur?
Na+/K+ ATPase creates concn. gradient with low conc. 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 back into the blood from the epithelial cell
There is also a passive chorine channel passing through basolateral membrane from cell to blood
