27 Questions
What is the primary function of Bowman's capsule?
To filter water and small molecules from the blood
Which structure is responsible for preventing proteins from being filtered into the glomerular filtrate?
Podocytes
What is the condition called when there is an abnormal amount of proteins present in the urine?
Proteinuria
Which layer of Bowman's capsule directly surrounds the glomerular capillaries?
Inner (visceral) layer
Which of the following is NOT a physical barrier that the glomerular filtrate passes through?
Endothelial cells of efferent arteriole
Sodium reabsorption primarily occurs in the distal convoluted tubule.
False
The renin-angiotensin-aldosterone system helps regulate blood pressure by increasing sodium reabsorption in the kidneys.
True
Tubular reabsorption involves the movement of substances from the blood into the renal tubules.
False
Proximal convoluted tubules are responsible for the reabsorption of glucose, amino acids, and bicarbonate.
True
Tubular transport in the kidneys is a passive process that does not require energy.
False
Sodium reabsorption mainly occurs in the distal tubule.
False
The proximal convoluted tubule is more involved in water reabsorption than in salt reabsorption.
False
The loop of Henle is responsible for selective tubular reabsorption.
False
The renin-angiotensin-aldosterone system plays a role in decreasing blood pressure.
False
Proximal tubules are responsible for the majority of water reabsorption in the nephron.
True
Tubular transport involves the movement of substances across the nephron's capillaries.
False
Selective tubular secretion involves the transfer of substances from the blood to the tubules for elimination.
True
Glucose and amino acids in the initial filtrate are reabsorbed by the proximal tubule through primary active transport.
False
The reabsorption of glucose and amino acids depends on the potassium gradient across the apical cell membranes of the epithelial cells.
False
Aldosterone can cause 100% retention of sodium in the body.
False
Natriuretic peptide stimulates sodium reabsorption in the distal and collecting tubules.
False
In the absence of aldosterone, 20mg of sodium per day may be excreted from the body.
True
A fall in NaCl, extracellular fluid volume, and arterial blood pressure stimulates the renin-angiotensin-aldosterone system.
True
Atrial Naturetic Peptide (ANP) stimulates sodium reabsorption in the distal tubules.
False
Ace Inhibitors cause loss of water by promoting salt reabsorption.
False
Glucose reabsorption has a tubular maximum that is reached when the plasma concentration of glucose exceeds 300mg/100 ml.
True
Renal threshold is the maximum amount of glucose that can be reabsorbed by the kidneys.
False
Study Notes
Glomerular Filtration
- The effective filtration pressure is the difference between the blood (hydrostatic) pressure in the capillary and the osmotic pressure generated by the plasma proteins of the blood.
- Hydrostatic pressure in the urinary space of Bowman's capsule and osmotic pressure generated by proteins in the fluid can also be factors, becoming important in disease states.
Glomerular Filtration Rate (GFR) and Renal Blood Flow (RBF)
- In normally hydrated mammals, GFR and RBF remain relatively stable despite minor short-term fluctuations in arterial blood pressure.
- This stability is maintained by mechanisms intrinsic to the kidney, known as renal autoregulation.
Tubular Reabsorption
- 99% of water is reabsorbed, 99.5% of sodium is reabsorbed, 50% of urea is reabsorbed, and phenol is not reabsorbed.
- Proximal convoluted tubule cells are cuboidal, with a luminal border modified with microvilli (brush border).
- Glucose and amino acids are reabsorbed from the filtrate by cells of the proximal tubule.
Glomerular Filtration Barrier
- The glomerular filtration barrier acts like a sieve, allowing all substances up to a molecular weight of about 65,000 daltons to pass through.
- Blood cells are too large to pass, and only a small percentage of plasma proteins pass through the barrier.
- Most other plasma constituents, such as glucose, amino acids, urea, creatinine, sodium, potassium, chlorine, and bicarbonate ions, readily cross the barrier.
Proteinuria and Hematuria
- Proteinuria is the presence of abnormal amounts of protein in voided urine.
- Kidney diseases that localize in or primarily affect glomeruli are often associated with proteinuria or hematuria (blood in voided urine).
Forces Involved in Glomerular Filtration
- The forces determining the rate of movement of fluid across the glomerular filtration barrier are:
- Glomerular capillary blood pressure (mmHg)
- Plasma colloid osmotic pressure
- Bowman's capsule hydrostatic pressure
- Net filtration pressure
Renal Processes
- Three basic renal processes:
- Glomerular filtration: filtering of blood into tubule forming the primitive urine
- Selective tubular reabsorption: absorption of substances needed by the body from tubule to blood
- Selective tubular secretion: secretion of substances to be eliminated from the body into the tubule from the blood
Urine Formation
- Urine formation occurs in the kidneys, and by adjusting the volume and composition of urine in response to changes in dietary intake or metabolism, the kidneys regulate the body balance of water, electrolytes, acids, and bases.
- Signs of kidney diseases include imbalances of water, electrolytes, acids, and bases, and increases in blood levels of urea and creatinine.
The Urinary System
- The urinary system consists of:
- Kidneys
- Blood supply: renal arteries and veins
- Ureter
- Urinary bladder
- Urethra
The Nephron
- The nephron is the functional unit of the kidney, consisting of:
- Bowman's capsule
- Glomerulus
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting duct
- Nephrons in all mammalian kidneys are similar in basic structure and function, but the number of nephrons differs among mammals.
Functions of the Kidney
- The kidney regulates:
- Water balance
- Electrolyte balance
- Plasma volume
- Acid-base balance
- Osmolarity balance
- Excretion
- Hormone secretion
Test your knowledge on the factors affecting effective filtration pressure in capillaries, including blood pressure, osmotic pressure, and disease states. Learn about the role of hydrostatic pressure and osmotic pressure in capillary filtration.
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