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Questions and Answers
What causes the blood in the glomerulus to be under very high pressure?
What causes the blood in the glomerulus to be under very high pressure?
The efferent arteriole is smaller in diameter than the afferent one.
What are the stages of osmoregulation carried out by the nephron in order? (Select all that apply)
What are the stages of osmoregulation carried out by the nephron in order? (Select all that apply)
- Reabsorption of glucose and water by the proximal convoluted tubule (correct)
- Reabsorption of water by the collecting duct
- Maintenance of a gradient of sodium ions in the medulla by the loop of Henle (correct)
- Formation of glomerular filtrate by ultrafiltration (correct)
What part of the nephron does ultrafiltration take place?
What part of the nephron does ultrafiltration take place?
The Bowman's capsule and glomerulus.
Explain the process of ultrafiltration.
Explain the process of ultrafiltration.
What three layers do substances need to move through during filtration? (Select all that apply)
What three layers do substances need to move through during filtration? (Select all that apply)
Describe how ultrafiltration occurs in a glomerulus.
Describe how ultrafiltration occurs in a glomerulus.
Approximately what percentage of glomerular filtrate is reabsorbed back into the blood?
Approximately what percentage of glomerular filtrate is reabsorbed back into the blood?
Where does selective reabsorption take place?
Where does selective reabsorption take place?
What is the purpose of selective reabsorption?
What is the purpose of selective reabsorption?
Explain the process of selective reabsorption.
Explain the process of selective reabsorption.
What is usually found in urine? (Select all that apply)
What is usually found in urine? (Select all that apply)
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Study Notes
Blood Pressure in the Glomerulus
- High pressure in the glomerulus is due to the efferent arteriole being smaller in diameter than the afferent arteriole.
Stages of Osmoregulation by Nephron
- Formation of glomerular filtrate occurs via ultrafiltration.
- Proximal convoluted tubule reabsorbs glucose and water.
- Loop of Henle maintains sodium ion gradient in the medulla.
- Water is reabsorbed in distal convoluted tubule and collecting ducts.
Location of Ultrafiltration
- Ultrafiltration takes place in the Bowman's capsule and glomerulus.
Process of Ultrafiltration
- Blood enters the glomerulus through the afferent arteriole under high pressure.
- High pressure pushes water, ions, urea, and glucose out to form glomerular filtrate.
- Blood cells and large proteins remain in the blood due to their size.
Layers for Substance Movement
- Water, ions, urea, and glucose pass through three layers: capillary wall, basement membrane, and epithelium of Bowman's capsule.
- Podocytes in the epithelium have gaps, allowing for easier movement.
- Endothelium of glomerular capillaries has fenestrations for filtration.
Ultrafiltration in Glomerulus
- High hydrostatic pressure facilitates filtration.
- Small substances such as water, glucose, and ions pass through capillary pores and basement membrane.
Reabsorption of Glomerular Filtrate
- Approximately 85% of glomerular filtrate is reabsorbed back into the bloodstream.
Selective Reabsorption Location
- Selective reabsorption primarily occurs in the proximal convoluted tubule (PCT).
Purpose of Selective Reabsorption
- To recover useful substances from the filtrate into the blood.
Mechanism of Selective Reabsorption
- Sodium ions (Na+) are actively transported from PCT cells into blood capillaries, lowering Na+ concentration in cells.
- Creates a Na+ concentration gradient between the PCT lumen and epithelial cells.
- Na+ diffuses from the lumen into epithelial cells, while glucose and amino acids are co-transported with Na+.
- Nutrients then diffuse into the bloodstream, and water follows by osmosis due to lower water potential in blood.
Composition of Urine
- Urine typically contains water, dissolved salts, urea, and excess vitamins.
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