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UKCD Histo Urinary

answers to test objectives for urinary system

QuestionAnswer
What is the structural/functional unit of the kidney? The nephron.
List the component parts of a nephron. The renal corpuscle (glomerulus + Bowman’s capsule), proximal convoluted tubule, loop of Henle, distal convoluted tubule
What types of nephrons can be classified based on their location in the cortex? Cortical, juxtamedullary, intermediate.
What implication(s) does nephron location have on their loops of Henle? Cortical have the shortest loops of Henle within the medulla as they are located furthest from it. The juxtaglomerular have the longest loops extending down into the medulla as they are closest.
Where might collecting tubules be located? In addition to being in the medulla, they also extend up into the cortex as medullary rays.
Where do collecting tubules terminate? On the renal papilla.
Where does the newly formed urine go after it passes the renal papilla location? It is collected by the funnel-like minor calyx. It is then funneled into a major calyx, then into the renal pelvis and out into the ureter proper.
What composes a renal corpuscle? The glomerulus (capillary) and Bowman’s capsule.
What cells comprise the vascular layer of Bowman’s capsule (Glomerular epithelium)? Podocytes.
What cell types would be found in a renal corpuscle? Podocytes, endothelial cells, mesangial cells (all in the glomerulus) and simple squamous epitheliial cells of the parietal layer of Bowman’s capsule.
What is the function of podocytes and where is it specifically located? Podocytes form the filtration barrier
What is the filtration slit? The space between the pedicels of adjacent podocytes processes.
What crosses the filtration slit? A filtration slit membrane extends across the filtration slit like a filter.
What is the implication of actin microfilaments in the podocyte pedicels? Adds contractility as a function of the pedicels - allowing them to change the width of the filtration slit.
hat are the specific components of the Glomerular basement membrane? The fused basement membranes of the podocyte and glomerular capillary. From the capillary lumen outward you encounter the lamina rara interna, the lamina densa, and the lamina rara externa.
What is the function of the Glomerular basement membrane (GBM)? It filters material from the lumen prior to its entering the filtration space as urinary filtrate.
What keeps it clean of debris/macromolecules? Mesangial cells clean the filtration membrane.
What other function(s) do these specific cells have? Also provide structural support for the glomerulus.
What specific portions of the GBM are responsible for the selective filtration of ions? Of macromolecules? The lamina rara specifically filters out positively charged molecules. The collagen fibers of the lamina densa act as a physical barrier preventing molecules of more than 70,000 Daltons from entering the urinary filtrate.
Which cell type secretes new BL to repair damage to the GBM? The podocyte.
What does excess protein in the urine indicate? A damaged filtration barrier
Where are mesangial cells located? A stalk-like group at the vascular pole that extend out into the glomerulus (for supporting framework). They also extend out along the JG complex as lacis cells.
By what other name are mesangial cells referred to elsewhere? Where is this? Known as lacis cells that extend out along the JG complex.
What is the macula densa? A crowded area (more epithelial cells per unit area) of the distal convoluted tubule wall.
Where is macula densea located? Be specific! The macula densa is found in the wall of the distal convoluted tubule in region of the vascular pole of the renal corpuscle.
Where is the JG complex located? Within the wall of the afferent arteriole.
hat are the component parts of the J-G complex? The macula densa of the distal convoluted tubule, JG cells (modified smooth muscle cells of the afferent arteriole wall) and extraglomerular mesangial (lacis) cells.
What is the function of the JG complex? Regulate blood pressure within the glomerular capillary as well as body-wide.
How does the JG complex work? Macula densa sense decreased NaCl in DCT, stimulates JG to secrete renine to increase blood pressure, Pressure increases dilate wall of afferent arteriole, negative feedback mechanism to shut down renine release and lower blood pressure
What are the distinguishing morphological features of the proximal convoluted tubule? Large high cuboidal cells with indistinct lateral cell boundaries, ragged apical borders and a striated basal border. There are more PCT profiles than DCT profiles (as it is longer than the DCT).
How do the PCT cells integrate with the function of PCT region of the nephron? Their microvillous apical border and striated basal border indicate an effective increase in surface area as well as basal membrane active-transport to exchange large volumes of fluid and electrolytes from the lumen into surrounding capillaries.
Where would the majority of the loop of Henle be located? Generally, within the medulla.
Describe the appearance of the wall of the loop of henle segment of the nephron. Loops of Henle are composed of low to high squamous epithelial cells.
How does the release of renin result in increasing blood pressure? converts plasma-bound angiotensinogen to angiotensin I,is converted to angiotensin II cause vasoconstriction or aldosterone secretion from suprarenal cortex or causes sodium and water retention in the DCT. Both result in an increase of blood pressure.
Which other organ of the body is always involved in this increasing blood pressure, why? The lung. It is the site of angiotensin conversion enzyme (ACE) within the endothelial cells of this organ needed to convert angiotensin I to angiotensin II.
What other structure(s) have an intimate relationship with it the thin portion of the loop of Henle? A coiled capillary bed.
How can you tell these two structures apart? The loops of Henle do not have blood cells in their lumena.
What specific function occurs in the region of the thin loop of Henle? Water, sodium ions and chloride ions are resorbed from the urinary filtrate in this segment of the nephron.
How do cross sectional profiles of the distal convoluted tubule differ from those of the proximal region? 1. PCT are more numerous than DCT 2. PCT stain darker w/ less nuclei 3. PCT are higher cuboidal epithelium w/ rough luminal microvillous border; 4. PCT exhibit striated basal regions due to basal infoldings and mitochondria required for active transport.
Where are the collecting tubules located? In the medulla as well as in medullary rays.
Of what are collecting tubules composed? Tall cuboidal to low columnar epithelium with distinct lateral cell membranes.
What happens to the urine as it passes through the collecting ducts? It becomes more concentrated. Water and electrolytes lost during filtration in the glomerulus are withdrawn by the capillary network surrounding the tubular portion of the nephron.
List three mechanisms that can trigger JG cell release of renin. 1. Macula densa acts as an osmoreceptor and senses decreased sodium; 2. JG cells act as baroreceptors and sense decreased stretch (blood pressure) of the afferent arteriole; and 3. Sympathetic nerve stimulation of JG cells due to decreased sodium levels.
How is effeicient filtration accomplished in the renal corpuscle? Fenestrated glomerular capillaries (without diaphragms) and high hydrostatic pressure.
How much of the urinary filtrate is resorbed in the PCT? Approximately 80%.
List the structural features that facilitate this massive resporption. Apical microvilli, basal membrane infolding with associated mitochondriaon (striated basal membrane).
How many capillary beds are traversed in this pathway? Two.
?Why are two capillary beds unusual? Usually arterioles lead to capillaries which lead to venules, NOT an efferent arteriole.
What is the specific function of each of these two sets of capillaries? Glomerular capillaries function in effective filtration of the blood (loss of water and electrolytes); the peritubular capillaries surrounding the tubular portion of the nephron functions in resorbing the lost water and electrolytes.
What specific type of epithelium lines the urinary passageways? Transitional - a form of stratified epithelium
What do the vesicles in the apical regions of the uppermost layer of epithelial cells in this epithelial lining represent? Extra thick portions of cell membrane that become exposed when the cells stretch.
What is different about the cell membrane in these thick plates? It’s supposed function? It contains a different type of membrane lipid - cerebrosidewhich is the major component of the polar lipid fraction. Protects the epithelial cells from the acidic urine in the bladder lumen.
Does the ureter exhibit a submucosa? No submucosa only a fibroelastic lamina propria.
How are the smooth muscle layers of the ureter wall arranged? An inner longitudinal and outer circular layer of smooth muscle in the wall of the ureter.
What is the function of the urinary bladder? To store urine prior to elimination from the body.
What is the function of endothelial cells and where is it specifically located? endothelial cells are fenestrated for effective filtration;
What is the function of mesangial cells and where is it specifically located? mesangial cells support the glomerulus as well as clean the filtration barrier;
What is the function of simple squamous cells and where is it specifically located? simple squamous cells of the parietal layer of the capsule - line the outer aspect of the filtration (Bowman’s) capsule.
Created by: wiechartm
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