Intro to renal and filtration Flashcards
What percentage of cardiac output is attributed to the kidneys?
20%.
List the main functions of the kidney.
- Filtration of blood
- Detoxification (including drugs)
- Regulation of blood pressure
- Regulation of blood pH
- Regulation of haematopoiesis
- Making vitamin D.
What is the primary challenge in designing the kidney’s filter?
To create a very fine filter that does not clog while filtering a large volume of fluid in a small space.
What is the cut-off size for the kidney filter?
Approximately 4nm (40 Å).
What is the slit diaphragm?
A structural component of the kidney filter that allows for selective filtration.
True or False: Only about 3% of the total area of the slit diaphragm is actually slit.
True.
What happens when the afferent arteriole is restricted?
Blood pressure in capillaries drops and filtration rate decreases.
What happens when the efferent arteriole is restricted?
Blood pressure in glomerular capillaries rises and filtration rate increases.
What is one method the kidney uses to prevent clogging?
Pinocytosis of trapped proteins.
Fill in the blank: The typical blood flow to the kidneys is ______.
1.2L/min.
What is the typical plasma flow to the kidneys?
0.66L/min.
What is the rate of filtration through glomeruli summed across all?
0.13L/min.
Approximately what percentage of plasma is removed as filtrate?
20%.
What is the purpose of the fresh dialysate in an artificial glomerulus?
To be full of the ‘wanted’ small molecules of the blood to prevent net loss.
How many renal corpuscles are typically found in a human kidney?
50,000 – 1,000,000.
What hypothesis relates nephron number to a mother’s amino acid nutrition?
Barker hypothesis.
What is a major source of resistance to fluid flow in the kidney filter?
The slit diaphragm.
What is the role of mesangial cells in the kidney?
To clean the filter and renew it.
What is the significance of osmotic pressures in kidney filtration?
Pressure is needed to oppose the osmotic pressures from proteins and small molecule solutes.
What are the main parts of the nephron?
Renal corpuscle, Proximal tubule, Distal tubule, Henle’s loop
The nephron is divided into these four main sections.
What substances do nephron epithelia recover?
- Na+
- K+
- Ca2+
- Mg2+
- Cl-
- HCO3-
- PO42-
- H2O
- Amino acids
- Glucose
- Proteins
These are essential for various physiological processes.
What is the significance of understanding renal transport systems for medics?
Many components are drug targets used to control renal function and are vulnerable to damage by drugs
Knowledge of these transport systems aids in pharmacology and patient care.
What are Solute Carrier Family (SLC) proteins?
About 300 proteins, many are co-transporters powered by established concentration gradients
They are involved in secondary active transport.
What is the function of Aquaporins?
They are water channels that facilitate water transport across cell membranes
Essential for maintaining water homeostasis.
What is the role of the Na+/K+ ATPase?
It actively exports 3 Na+ out and imports 2 K+ into the cell, creating an ion gradient
This gradient powers passive transport of other solutes.
How does sodium recovery occur in the proximal tubule?
Via Na+/H+ exchanger (SLC9A3) and Na+/K+ ATPase
This is a primary mechanism for sodium reabsorption.
What transporter is responsible for sodium chloride co-transport in the distal tubule?
Sodium chloride co-transporter (SLC12A3)
This transporter facilitates sodium and chloride recovery.
What is the role of the Na-K-Cl cotransporter in the Loop of Henle?
It is responsible for potassium recovery
The transporter is known as SLC12A2.
How are amino acids recovered in the proximal tubule?
Using Na+/2Cl- co-transporters (SLC6a18/SLC6a19) and other specific channels
Various channels carry different neutral amino acids.
What is the primary mechanism for glucose recovery in the kidneys?
Active transport via SLC5A1/SLC5A2
Glucose is reabsorbed mostly in the proximal tubule.
What is the relationship between plasma glucose levels and glucose excretion?
As plasma glucose increases, reabsorption reaches a threshold, leading to excretion
This is significant in conditions like diabetes mellitus.
What do Organic Cation Transporters (OCTs) do?
They allow passive movement of cations in either direction
Examples include OCT2 and OCT3.
What do Organic Anion Transporters (OATs) transport?
- Methotrexate
- Furosemide
- Penicillin
These are important for excreting various drugs and metabolites.
What is the function of the SLC34A1 transporter?
It is involved in phosphate recovery in the proximal tubule
This transporter plays a role in maintaining phosphate balance.
What is the significance of bicarbonate recovery in the kidney?
It helps regulate acid-base balance in the body
The mechanism involves bicarbonate and hydrogen ion exchange.
How is ammonia produced in the kidneys?
From glutamine metabolism in the proximal tubule
Ammonia can be transported and excreted as ammonium ions.
What do intercalated cells in the kidneys do?
They regulate acid-base balance by secreting or absorbing hydrogen ions
Type A cells secrete H+, while Type B cells absorb H+.
What is the primary mechanism for calcium transport in the kidneys?
Calcium is mainly transported paracellularly and passively driven by osmotic gradients
This occurs once urine is concentrated.
What is the summary of solute recovery mechanisms in the kidneys?
Recovery mostly relies on the sodium gradient created by the Na+/K+ ATPase pump
Each solute has specific transport systems, mainly SLC proteins.
Fill in the blank: The kidney has several ways to play with ______ balance of the body.
acid-base
This is crucial for maintaining overall homeostasis.
What is the primary function of the proximal tubule?
Recovery of sodium, chloride, phosphate, and calcium
Achieves 65% recovery of these ions
What gradient drives the reabsorption of glucose and amino acids in the proximal tubule?
Sodium gradient
Sodium is pulled through by the basal pump
Fill in the blank: Potassium is dumped into the tubule lumen due to the _______.
basal pump
What happens to osmolarity in the proximal tubule?
Tries to lower osmolarity, causing water to flow passively from the tubule
This occurs to counteract solute movement
What is the role of aquaporins in the proximal tubule?
Facilitate the passive flow of water
Water flows from the tubule to the interstitium
True or False: The proximal tubule concentrates urine.
False
The proximal tubule maintains roughly iso-osmotic conditions
What is the function of the sodium chloride co-transporter SLC12A2?
Pulls sodium and chloride from the tubule to the tissues
What is the permeability characteristic of the descending thin limb of the Loop of Henle?
Permeable to water, impermeable to ions and urea
What occurs in the thick ascending limb of the Loop of Henle?
Active recovery of ions driven by the sodium pump
How does the Loop of Henle affect the osmolarity of tubular contents?
Gets more diluted due to ion recovery
Mainly because so much has been recovered
What is the role of the vasa recta in maintaining the hypertonic region of the medulla?
Facilitates countercurrent exchange of water and ions
Fill in the blank: The distal tubule is primarily involved in the recovery of _______.
ions
What percentage of NaCl is recovered by the time it reaches the distal tubule?
95%
What does the collecting duct regulate?
Permeability to water
What hormone regulates water permeability in the collecting duct?
Vasopressin
How much filtered water can be removed by the collecting duct?
Up to 24%
What anatomical arrangement is crucial for the function of the Loop of Henle?
Separation between normal and hypertonic zones
What is the effect of low renal oxygen on erythropoiesis?
Stimulates erythropoietin release, leading to more red blood cells
What three mechanisms control blood flow to the glomerulus?
- Systemic blood pressure
- Constriction of afferent arterioles
- Constriction of efferent arterioles
What is the function of the macula densa?
Regulates afferent arteriole constriction based on sodium concentration
Fill in the blank: Elevated glomerular blood pressure results in _______ flow of filtrate.
faster
What is the role of the macula densa?
Regulates glomerular filtration rate (GFR) by sensing NaCl concentration
How does elevated glomerular blood pressure affect the macula densa?
Filtrate flows faster, leading to less time for solute recovery and more NaCl remaining in the distal tubule
What do macula densa cells release in response to increased NaCl?
Adenosine
What effect does adenosine have on the afferent arteriole?
Causes constriction
What do juxtaglomerular cells release in response to macula densa signaling?
Renin
What type of enzyme is renin?
Protease
What is the action of Angiotensin II on kidney cells?
Promotes active export of Na+ and H+
What is the function of the Na+/H+ exchanger SLC9A3?
Facilitates sodium and hydrogen ion transport
What is the role of aldosterone in kidney function?
Enhances Na+ recovery and K+ secretion
What type of cells does aldosterone act upon?
Principal cells and α-intercalated cells in the collecting duct
What is the effect of Arginine Vasopressin (AVP) on kidney cells?
Increases water reabsorption by regulating aquaporin channels
True or False: AVP is also known as antidiuretic hormone (ADH).
True
What does Atrial Natriuretic Peptide (ANP) do in the kidneys?
Blocks Na+ re-uptake in collecting ducts, promoting sodium loss
What is the primary site for calcium recovery in the kidney?
Distal convoluted tubule (DCT)
Which hormone regulates calcium recovery in the kidney?
Parathyroid hormone (PTH)
How does the body typically maintain acid-base balance?
By removing excess acid through urinary excretion
What is the primary function of loop diuretics?
Increase urine output by inhibiting Na+ recovery in the thick ascending limb of Henle’s loop
What happens to electrolytes when loop diuretics are used?
Loss of Na+, K+, and Cl- due to failure to recover in the TAL
What is a major side effect of loop diuretics?
Hypercalcuria and potential kidney stones
What distinguishes thiazide diuretics from loop diuretics?
Thiazides are effective for hypertension control and drive calcium recovery
Fill in the blank: The mechanism of action of thiazide diuretics primarily targets _______.
SLC12A3/NCC
What is a characteristic of potassium-sparing diuretics?
They prevent potassium loss while promoting sodium excretion
What is the effect of acidosis on potassium reabsorption?
Increases potassium reuptake due to increased H+ out-pumping
What is the effect of alkalosis on potassium reabsorption?
Decreases potassium reuptake and increases potassium loss
What are carbonic anhydrase inhibitors used for?
They increase bicarbonate in the lumen, resisting water egress osmotically
What effect does high plasma glucose have on diuresis?
Can lead to osmotic diuresis, causing water loss without significant Na+ loss
