Urinary System Pt. 3 Flashcards
How much of the total cardiac output do the kidneys receive?
About 20-25% of the cardiac output
What is the primary role of the renal arteries?
To deliver blood to the kidneys
How does the renal blood flow compare to other organs?
Renal blood flow is higher than in most other organs
What is the role of the afferent arterioles in renal blood flow?
They supply blood to the glomerulus
What do efferent arterioles do in the context of renal blood flow?
They take blood away from the glomerulus
What are the peritubular capillaries in the kidneys?
A network of tiny blood vessels surrounding the proximal and distal convoluted tubules
What is the vasa recta in the kidneys?
Specialized peritubular capillaries that supply the nephron loop
Why do the kidneys have a large amount of blood flow?
To maintain the necessary pressure and flow for filtration
What is autoregulation in the kidneys, and how does it work?
The kidneys can regulate their own blood flow by adjusting the diameter of the afferent and efferent arterioles
What is the myogenic mechanism in autoregulation?
A response to increased blood pressure, causing a constriction of afferent arterioles
What is the tubuloglomerular feedback mechanism?
A response to increased blood pressure causing a reduced GFR
What is the juxtaglomerular apparatus (JGA)?
A region in the nephron where the distal convoluted tubule contacts the afferent and efferent arterioles
What cell types are present in the JGA?
Macula densa cells, granular cells (juxtaglomerular cells), and extraglomerular mesangial cells
What is the role of macula densa cells in the JGA?
They monitor the composition of the fluid in the distal convoluted tubule, and if it has enough sodium. If it doesn’t, it releases renin.
How do granular cells (juxtaglomerular cells) respond to changes in blood pressure?
They can contract when blood pressure drops and relax when it rises
What is the role of extraglomerular mesangial cells in the JGA?
They provide structural support and can communicate with each other and other JGA cells
What triggers the release of renin by granular cells?
Low blood pressure or sympathetic stimulation
What does renin do when it’s released into the blood?
It initiates a cascade that ultimately results in increased blood pressure
What are the three processes of urine formation in the nephron?
Filtration, reabsorption, and secretion
What is reabsorption in the nephron?
The process of moving substances from the filtrate back into the bloodstream
What is secretion in the nephron?
The movement of substances from the blood into the tubular fluid
In which part of the nephron does the majority of reabsorption occur?
Proximal convoluted tubule
What substances are typically reabsorbed in the proximal convoluted tubule?
Glucose, amino acids, ions, and water
What is the descending limb of the nephron loop primarily permeable to?
Water
What is the ascending limb of the nephron loop impermeable to?
Water
What is the role of the distal convoluted tubule in reabsorption and secretion?
It fine-tunes the composition of tubular fluid and plays a role in calcium ion regulation
What is the collecting system in the nephron, and what happens there?
It is where variable amounts of water are reabsorbed, and urine is formed
What is the countercurrent multiplier system, and what is its purpose?
It is a system in the nephron loop that concentrates urine by creating a gradient of increasing osmolarity
How does the countercurrent exchange system work in the vasa recta?
It helps maintain the osmotic gradient in the medulla by exchanging solutes and water
What hormones influence water reabsorption and urine concentration?
Antidiuretic hormone (ADH) and aldosterone
What is the role of ADH in water reabsorption?
ADH increases water reabsorption by the collecting ducts
Where is ADH produced, and what stimulates its release?
ADH is produced by the hypothalamus and released in response to increased blood osmolarity or decreased blood volume
What is the primary target of aldosterone, and how does it affect the nephron?
Aldosterone’s target is the distal convoluted tubule, and it promotes sodium reabsorption and potassium secretion
What is atrial natriuretic peptide (ANP), and what is its role in water and electrolyte balance?
ANP is a hormone released by the heart in response to high blood pressure, and it promotes sodium and water excretion
How do the kidneys help regulate blood pH?
By excreting hydrogen ions and reabsorbing bicarbonate ions
What is the role of the buffer systems in maintaining blood pH?
Buffers can temporarily bind to excess hydrogen ions, preventing drastic changes in blood pH
How do the kidneys help regulate calcium ion levels in the blood?
By reabsorbing or excreting calcium ions in the distal convoluted tubules
What hormones are involved in regulating calcium ion levels?
Parathyroid hormone (PTH) and calcitonin
What is the role of PTH in calcium regulation?
PTH increases calcium ion reabsorption in the distal convoluted tubules
What is the role of calcitonin in calcium regulation?
Calcitonin decreases blood calcium levels by inhibiting calcium reabsorption in the kidneys
