Name the structures of the Nephron which are in the Medulla.
The loop of Henle, the collecting duct.
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Define Ultrafiltration.
Filtration under pressure that seperates small soluble molecules from the blood plasma.
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Where are the molecules filtered from and to?
From the Glomerulus to the Bowmans Capsule.
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What seperates the Glomerulus and the Bowmans Capsule?
Two cell layers and a basement membrane.
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What is the Glomerular filtration rate?
The rate at which fluid passes from the blood in the glomerular capillaries into the Bowmans Capsule.
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What is this rate determined by?
The difference in water potential between the two areas.
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What is the NET effect of higher pressure in the capillary and lower solute concentration in the Bowmans Capsule?
Fluid moves out of the capillary and into the lumen of the capsule.
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How is high blood pressure maintained in the Glomerulus?
Contraction of the heart (hydrostatic pressure), the afferent arteriole having a wider diameter than the efferent arteriole, the large surface area of the capillaries.
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What does the basement membrane do?
Forms the selective barrier between the blood and the Nephron and acts as a molecular sieve.
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What is the first cell layer?
The wall of the capillary. Single layer of cells, contains many small gaps.
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What is the second cell layer?
The wall of the Bowmans Capsule. The epithelial cells in this layer are called podocytes.
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How can glomerular pressure be altered?
Changes in the diameter of the afferent and efferetn aterioles.
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What is selective reabsorption?
The process by which useful products (e.g. glucose, salts) are reabsorbed back into the blood as the filtrate flows along the Nephron.
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What is reabsored?
Most of the water and salt. All of the glucose.
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Where does this take place?
The proximal convoluted tubule.
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How are the cells in the wall of the tubule adapted for its function?
1. Microvilli = large surface area for reabsorption 2. Mitochondria = provide ATP for the active transport of glucose and salts. Water follows by osmosis.
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Small amounts of what are reabsorbed in the distal convoluted tubule?
Water and salts.
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Where is most of the remaining water reabsorbed?
The collecting duct.
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What do the Loops of Henle do?
Collectively concentrate salts in the tissue fluid of the medulla of the kidney.
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What does a high concentration of salt cause?
Osmotic flow of water out of the collecting ducts thereby concentrating the urine and making it hypertonic to the blood.
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What are the limbs of the loop of Henle called?
The descending limb and the ascending limb.
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Describe the Ascending limb.
The walls are impermeable to water. The cells in the walls actively transport sodium and ions out of the fluid in the tubule and into the tissue fluid between the two limbs. This produces an area of low water potential.
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Describe the Descending limb.
The walls are permeable to water and also sodium and chloride ions. As fluid flows down the tubule, water passes out by osmosis into the region of low water potential. At the same time sodium and chloride ions diffuse into the descending limb.
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Where is the solution most concentrated?
Bottom of the hair pin (loop).
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Other cards in this set
Card 2
Front
What is the definition of osmoregulation?
Back
The mechanism by which the balance of water + dissovled solutes is regulated.
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