Renal Physiology 1 Flashcards
What are the main functions of the kidney?
- Maintain water balance in the body
- Regulate concentration of ions in extra-cellular fluid
- Maintain plasma volume (blood pressure)
- Maintain acid-base balance (pH)
- Maintain osmolarity (concentration of solutes)
A change in one function affects the others.
What does the kidney excrete?
- Waste products of body metabolism (e.g., urea, uric acid, creatinine)
- Foreign compounds (e.g., drugs, pesticides, food additives)
- Erythropoietin
- Renin
- Active vitamin D
The kidney must filter out toxins generated from metabolism or consumed.
What is urine?
An excretory product of kidney function produced by filtration, reabsorption, and secretion.
Urine exits the kidneys through the urethra.
What are nephrons?
The basic functional units of the kidney, approximately 1 million per kidney.
Nephrons can be lost with age and vary in number based on body size.
What components make up a nephron?
- Vascular component (glomerulus)
- Tubular component (Bowman’s capsule, proximal tubule, Loop of Henle, distal tubule)
The glomerulus acts like a ‘sieve’ for filtering blood.
What is the function of the Loop of Henle?
Establishes an osmotic gradient essential for concentrating urine.
The length of the Loop of Henle varies between species based on water retention needs.
What are the three main renal processes?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
These processes occur at different locations and rates within the nephron.
What is the glomerular filtration rate (GFR)?
The rate at which plasma is filtered through the glomeruli, averaging 125 ml/min.
GFR can be measured using substances like inulin.
What is renal clearance?
The volume of blood plasma completely cleared of a substance per minute.
Clearance rate helps measure the kidney’s filtering ability.
What happens if a substance is filtered and reabsorbed but not secreted?
Plasma clearance < GFR.
Example: All filtered glucose is reabsorbed, so its clearance rate is 0.
What is renal plasma flow?
The amount of plasma being filtered by the kidneys, averaging 625 ml/min.
This represents about 20% of total cardiac output.
What are the mechanisms of autoregulation in the kidneys?
- Myogenic mechanism
- Tubuloglomerular feedback mechanism
- Neural mechanism
These mechanisms help maintain GFR despite fluctuations in blood pressure.
What is tubular reabsorption?
The process by which useful products of glomerular filtration are recovered from the filtrate.
It is highly selective and variable.
Fill in the blank: The majority of sodium reabsorption occurs in the _______.
proximal tubule
Sodium reabsorption is crucial for reabsorbing other substances.
What are the types of transport involved in tubular reabsorption?
- Passive transport
- Active transport
Active transport requires energy whereas passive transport occurs down gradients.
True or False: Glucose is excreted in the urine of healthy mammals.
False
All filtered glucose is reabsorbed in healthy individuals.
What is the role of phosphate reabsorption in the kidneys?
Tubules can reabsorb phosphate up to normal plasma concentration, with excess excreted in urine.
Phosphate levels are not tightly controlled as deficiencies are rare.
How does the body maintain water balance?
By regulating water excretion through kidney function.
Water constitutes about 60% of body weight.
What percentage of reabsorption occurs in the proximal convoluted tubule?
65%
Important in reabsorption of glucose, amino acids, water, urea and chloride ions
What is the role of the Loop of Henle in urine concentration?
25% reabsorption through passive transport
Allows production of urine of varying concentrations
What percentage of reabsorption occurs in the distal tubule?
8%
Active transport and subject to hormonal control
What percentage of body weight is made up of water?
60%
This remains fairly constant due to regulation by the kidneys
What are the two components of body water?
- Intracellular fluid
- Extracellular fluid
What is the typical osmolarity of isotonic fluids?
300 mosm/l
