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44 Cards in this Set
- Front
- Back
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Three mechanisms used by urinferous tubule to produce urine:
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1) Filtration
2) Reabsorption 3) Secretion |
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Contents of the filtrate
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Small moecules of blood plasma.
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What is reclaimed during reabsorption?
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Most nutrients, water and essential ions. 99% of renal volume is reabsorbed.
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What kind of waste dispolsal is moved during the active process of secretion? Where does it move?
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Additional undesirable molecules are moved into the tubucle from the blood of surrounding capilaries.
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What are the parts of the Nephron?
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Renal corpuscle and a turular section consisting of the prximal convoluted tubule, loop of Henle, and distal convoluted tubule.
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What is contained within renal corpulscls and where are they located?
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Occur strictly in the cortex, consist of a tuft of capillaries called a glomerulus surrounded by a cup shaped, hollow glomerular capsule (Bowman's capsule).
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What is unique about the endothelium of the glomerulus?
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It is fenestrated (has pores).
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What is the result of having pores in the endothelium of the glomerulus?
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Large quantities of fluid and small molecules can pass from the capillary blood intot he hollow interior of the glomerular capsule, the capsular space.
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What percentage of the fluid leaves the glomerulus and enters the capsular space?
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20%
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What are the name of the branching epithelial cells located on the visceral layer of Bowman's capsule?
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Podocytes
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What are the pedicels and what do they do?
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They are the foot processes or end branches of podocyte cells. These "litter feet" interdigitate with each other as they surround the glomerular capillaries. The filtrate passes through filtration slits or slit pores located between the foot processes. They filter material from the filtrate.
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What are the three layers of the filtration membrane or barrier located between the glomerulus and Bowman's capsule?
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1) The fenestrated endothelium of the capillary
2) The filtration slits between the foot processes of podocytes, each of which is covered by a thin slit diaphragm 3) An intervening basement membrane consisting of the fused basal laminae of endothelium and podocyte epithelium. |
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What are the roles of the fenestrated capillaries and the podocyte epithelium?
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The capillary pores restrict the passage of the larges elements such as blood cells, whereas the basement membrane and slit diaphragm hold back all but the smallest proteins while letting rhough small molecules such as water, ions, glucose, amino acids and urea.
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What are the three sections of the tubular part of a Nephron?
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1) Elaborately coiled proximal consoluted tubule
2) A hairpin loop called the loop of Henle 3) Another winding and twisting part called the distal convoluted tubule which ends by joining a collecting tubule. |
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What is the primary function of the proximal convoluted tubule?
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Reabsorption and secretion.
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What is the cell structure of cells in the proximal convoluted tubule?
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Its walls are cuboidal epithelial cells with long microvilli on the luminal surface.
The cells contain many mitochondria which provide the energy for reabsorption. A highly infolded basolateral membrane (plasma membrane) on their basal and lateral cell surfaces that contain many ion-pumping enzymes responsible for reabsorbing molecules from the filtrate. |
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What kinds of ion-pumps are found in the cells lininig the proximal convoluted tubule?
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Open Na+ channels - apical region
Open Na+/K+ channels - basular region Na+/AminoAcid cotransporters - extracellular side Na+/Glucose cotransporters - extracellular side |
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How does a cotransporter work for the Na+/AminoAcid and Na+/Glucose cotransporters?
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When an Na+ and AminoAcid molecule attach to a cotransporter, it will flip from the extracellular side to the intracellular side of the cell. The molecules will then be released.
The same for the Na+/Glucose transporters. |
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What are the parts of the loop of Henle?
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1) Descending limb - continuous with the proximal tubule
2) Thin portion of descending limb \ 3) Ascending limb (may contain a thin then thick portion) |
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What type of epithelial cell lines the thin segment of the descending limb of the loop of Henle?
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Simple squamous.
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What type of endothelial cell lines the distal convoluted tubule?
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Simple cuboidal
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What are the two classes of nephrons and there abundance?
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1) Cortical nephrons are located almost entirely withint he corlex with their loops of Henle dipping only a short distance into the medulla (~85% of all nephrons).
2) Juxtamedullary ("near the medulla") for which thre renal corpuscles lie near the cortex-medulla junction, and they have long loops of Henle that deeply invade the medulla. |
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What is the purpose of the juxtamedullary nephrons?
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To concentrate urine.
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What is the most important role of the collecting tubules and distal tubules of the nephron?
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Conserve body fluids.
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What happens regarding the pituitary gland when the body needs to conserve water?
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It secretes antidiretic hormone which increases the permeability of the collecting tubules and distal tubules to water.
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The glomerulus is a capillary bed fed and drained by arterioles - an afferent arteriole and an efferent arteriole. What does this mean for the gloerulus?
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The blood pressure can be quite high for a capillary bed, thus making filtration easy.
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What is the role of the peritubular capillaries?
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They are low-pressure, porous capillaries that readily absorb solutes and water from the tubule cells after these substances are reabsorbed from filtrate. All molecules that are secreted by the nephrons into the urine are derived from the blood of these nearby peritubular capillaries.
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Where are the peritubular capillaries?
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They lie in the interstitial connective tissue of the renal cortex and cling closely to the convoluted tubules and empty into tnearby venules of the renal venous system. They arise from efferent arterioles draining the cortical glomeruli.
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Where is the vasa recta?
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In the deepest part of the renal cortex. They look like a rope ladder hung on top of the juxtamedullary nephron. They are fed by efferent arterioles fromt eh juxtamedullary glomeruli.
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What is the role of the vasa recta?
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They are part of the kidney's urine-concentrating mechanism.
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The juxtaglomerular apparatus is associated with what two structures? Where is it located?
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1) Structures of both the tubule and arteriole are modified.
2) The apparatus is a specialized area of contract between the first part of the distal convoluted tubule and the afferent arteriole. |
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Where are juxtagloerular cells and what is there purpose?
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The are contained on the wall of the afferent arteriole and are modified smooth muscle cells with secretory granules containin the hormone renin. These are mechanoreceptors that secrete renin into the afferent arteriole in response to falling BP.
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Where is the macula densa?
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It is the portion of the distal tubule adjacent to the juxtaglomerular cells.
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What is the cell type for the macula densa?
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Tall, closely packed epithelial cells.
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What is the purpose of the macula densa?
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The cells act as chemoreceptors for monitoring solute concentrations in the filtrate. Whenever such solute concntrations fall below a certain level, they send a signal to the juxtaglomerular cells to secrete renin.
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What does renin do?
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This hormone is secreted by the kidneys in response to hyptension; it convers the plasma protein angiotensinogen to angiotension I, leading indreicty to a rise in blood pressure.
It also increases blood-solute concentraion and blood volume. |
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What is the purpose of the macula densa?
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The cells act as chemoreceptors for monitoring solute concentrations in the filtrate. Whenever such solute concntrations fall below a certain level, they send a signal to the juxtaglomerular cells to secrete renin.
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What is significant about the afferent arterioles versus the efferent arterioles which feed and drain the Glomerulus?
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The afferent are larger than the efferent, thus building up the pressure in the Glomerulus.
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The concentration gradient that exists from the cortex to the medulla of the kidney is produced by the
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loops of the juxtamedullary nephrons
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The major nitrogenous waste product in humans is:
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urea
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The correct sequence of blood flow through the kidney is:
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interlobular artery > afferent arteriole > glomerulus > efferent arteriole > peritubular capillaries
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Should blood pressure rise, one means of renal autoregulation would involve:
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constriction of the afferent arteriole
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What is aldosterone?
Where does it have an effect? What ion is this responsible for moving? How is the movement of water related to aldosterone? |
A hormone.
Causes the DCT and cortical portion of the CD to reabsorbe more Na+. Na+ Water follows the Na+ out of the collecting tube (osmosis). |
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What is the antidiuretic hormone and where does it exert its affect?
How does it function to move water out of the collecting ducts? |
The permeability of hte CDs is affected by ADH. Increasing ADH will cause the CDs to synthesize additional aquapores which in turn will result in more reabsorption of water.
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