what are the basic differences between cortical and juxtamedullary nephrons?
Cortical nephrons: most numerous type, renal corpuscles in outer portion of renal cortex, short loops of Henle lying mainly in cortex and penetrate only into outer region of medulla, loop blood supply is from peritubular capillaries
juxtamedullary nephrons: least numerous, corpuscles lie deep in cortex close to medulla, long loop of henle extending into deepest region of medulla, loop blood supply from vasa recta.
why are the kidneys said to be retroperitoneal?
their position in the body is posterior to the peritoneum of the abdominal cavity.
hilus
Is the place where blood vessels and nerves enter and leave the kidney.
what structures pass through the renal hilus?
Ureter, renal artery, renal vein, lymphatic vessels, nerves
What volume of blood enters the renal arteries per minutes?
At rest, about 20-25% of cardiac output flows through the kidneys. This is on the order of 1200 ml per minute.
Where is the juxtaglumerular apparatus located and what is its structure?
Location: it is where the DCT makes contact with the afferent arteriole
Structure: macula densa cells in the wall of the DCT and juxtaglomerular cells (modified smooth muscle cells) in the afferent arteriole wall.
When cells of the renal tubules secrete the drug penicillin, is the drug being added to or removed from the bloodstream?
secreted penecillin is removed from the blood
Why is there much greater filtration through glomerular capillaries than through capillaries elsewhere in the body?
glomerular capillaries present a large surface area for filtration, are about 50 times leakier than capillaries in most other tissues due to their large fenestrations, and glomerular capillary blood pressure is high.
Micturition
-urination
-center in PONS
-distension of bladder walls initiates spnal reflexes that stim contraction of external urethral sphincters and inhibit the detrusor muscle and internal sphincter.
What chemical substances are normally present in urine?
Is a sterile fluid composed mostly of water,nitrogen-containing waste,and electrolytes.Important nitrogenous waste include urea,uric acid,ammonia,and creatinine.
In which section of the nephrons and collecting ducts does secretion occur?
Secretion occurs in the proximal convoluted tubule, the loop of henle, the last part of the distal convoluted tubule, and the collecting duct
Which part of the filtration membrane prevents red blood cells from entering the capsular space?
glomerular fenestrations
If the urinary excretion rate of a drug such as penicillin is greater than the rate at which it is filtered at the glomerulus, how else is it getting into the urine?
by secretion
What is the major chemical difference between blood plasma and glomerular filtrate?
blood plasma: contains blood cells, platelets, most plasma proteins and nutrients.
glomerular filtrate: contains nutrients but no formed elements and very few, if any, of the plasma proteins.
Which portions of the renal tubule and collecting duct reabsorb more solutes than water to produce dilute urine?
ascending loop of henle and entire collecting duct.
Which solutes are the main contributors to the high osmotic gradient of interstitial fluid in the renal medulla?
Na+, K+ and urea
How does filtered glucose enter and leave a PCT cell?
It enters via Na+ symporters located in the apical membrane and leaves through the basolateral membrane via facilitated diffusion.
Besides ADH, which other hormones contribute to the regulation of water reabsorption?
Angiotensin II and aldosterone
Which hormone stimulates reabsorption and secretion by principal cells, and how does this hormone exert its effect?
Aldosterone-stimulates the principal cells int he collecting ducts to reabsorb more Na+ and Cl- and secrete more K+ with the reabsorption of Na+ and Cl-; when more Na+ and Cl- are reabsorbed, more water is reabsorbed resulting in increased blood volume and a return of blood pressure to normal.
How may kidney function be evaluated?
by urine test or blood test
Which hormones are responsible for influencing the renal reabsorption?
Aldosterone and antidiuretic hormone
How does Na+, K+, Cl-ions is transported in a thick ascending limb of the loop of Henle?
Active NaCl transport in the thick ascending limb is driven by the basolateral Na+-K+-ATPase pump. The activity of this transporter is higher in the thick ascending limb than in other nephron segments, indicating the importance of active Na+ reabsorption at this site [1-3]. The Na+-K+-ATPase pump has two major effects on Na+ handling: it actively transports reabsorbed Na+ out of the cell and back into the systemic circulation via the peritubular capillaries; and it maintains a low cell Na+ concentration that allows luminal Na+ to continue to enter the cell down a concentration gradient [1].
What is the function of the tight junction between tubule cells?
With its barrier function of epithelia, it has long been suspected that tight junctions may be selectively permeable to some ions, because the permselectivity of the paracellular pathway is variable in different segments of the renal tubule.
By what mechanism is water reabsorbed from tubular fluid?
The proximal tubule cells are most active in reabsorption. Most of the nutrients, 65% of the water and sodium ions, and the bulk of actively transported ions are reabsorbed in the PCT.