Final Exam Flashcards
What is the major function of the renal system?
To filter blood plasma and remove animal body waste and unnecessary molecules.
What are the unnecessary molecules being filtered out by the renal system under normal conditions?
Urea/uric acid, creatinine, and other environmental toxins
What molecules filtered through the renal system reflect animal physiology? provide examples.
Endocrine and metabolic activities. ex) hormones and hormone metabolites, blood glucose, and creatinine
Besides filtering waste, what are the other major functions of the renal system?
Maintain physiological levels of solutes and pH, and maintain physiological levels of water, blood volumes, and blood pressure.
What are the non-major functions of the renal system?
Secretion of erythropoietin to increase red blood cell numbers, convert vitamin D into the active form for calcium absorption in gut, and excretion of pheromones.
What are kidneys?
Organs important for blood plasma filtration, secretion and reabsorption, and urine formation.
What are ureters?
Tubes (1per kidney) that transport urine to the bladder.
What animals are ureters found in?
Fish, amphibians, and mammals.
Where do ureters transport urine in most birds, reptiles, and amphibians?
To the hindgut where it is excreted out the cloaca.
What is the bladder?
The organ in mammals that hold urine.
What is the urethra?
The tube that transports urine from the bladder for excretion.
What is the renal cortex?
The outer most region of the kidney. The location of plasma filtration
What is the renal medulla?
The inner region of the kidney. Has osmotic potential.
What is the renal pelvis?
The area of the kidney in which urine is collected before entering the ureter.
What is the nephron?
The small, microscopic tubule system responsible for blood plasma filtration, secretion, reabsorption, and urine formation. Millions in each kidney.
Where does the nephron tubule system begin and end?
Begins in the cortex and a portion extends into the medulla.
What qualities of kidneys depends on species?
Shape, prevalence of renal lobes, renal pyramids, and true renal pelvis.
In the cortex, what does each kidney include?
A Bowman’s capsule
What is the function of the Bowman’s capsule?
Filtering plasma into the nephron tubule system through the glomerulus.
What is the glomerulus?
A collection of special capillaries found in the Bowman’s capsule that filter plasma into the tubular component.
Nearly all plasma contents except large proteins are filtered into ________.
Tubules
What do some capillaries outside the Bowman’s capsule do?
Secrete molecules into the tubule system.
What happens to important molecules needed by the animal?
They are reabsorbed back out of the tubule and into the capillaries.
The tubule is long, convoluted, and lined with ________ ____ that help reabsorb molecules through _______ and _______.
epithelial cells, channels, carriers
Where does waste/toxic substances continue to after the kidney nephron?
They continue to the renal pelvis, ureters, and bladder for excretion.
Where does osmoconcentration and urine formation occur in the nephron?
Across the membrane of the nephron in the medulla.
What are the nephron tubule structures?
The Bowman’s capsule, the proximal tubule, the loop of henle, the distal tube, and the collecting duct.
Multiple nephrons drain into a _________ ____.
collecting duct
What are the lobes of the cow kidney called?
Lobules
All collecting ducts drain into the _____ _____.
renal pelvis
What does the Bowman’s capsule collect?
The glomerular filtrate.
What occurs in the proximal tubule?
Uncontrolled reabsorption and secretion of selected substances
What is the function of the loop of henle?
It establishes an osmotic gradient in the renal medulla that is important to the kidney’s ability to produce urine of varying concentration.
What occurs in the distal tubule and collecting duct?
Variable, controlled reabsorption of Na+ and H2O and secretion of K+ and H+. Fluid leaving the duct is urine, which enters the renal pelvis.
What are the nephron blood vessels?
The afferent arteriole, the efferent arteriole, the glomerulus, and the peritubular capillaries.
________ occurs in the glomerulus.
Filtration
________ occurs from the peritubular capillaries into tubule. Capillaries continue into ______ and then _____ _____.
Secretion, venules, renal veins
What is the function of the afferent arteriole?
Carry blood to the glomerulus
What is the function of the efferent arteriole?
Carry blood away from the glomerulus.
What are the functions of peritubular capillaries?
Supply the renal tissue with oxygen and make exchanges with fluid in the tubular lumen.
Initial filtration at the glomerulus is not _______.
selective
What is meant by initial filtration at the glomerulus not being selective?
Everything in blood except cells/ cellular material and large proteins are filtered.
Reabsorption along tubule is highly ______ and achieved through ________ ________ _________.
Selective, assisted membrane transport
What major substances are reabsorbed through the nephron tubule?
Glucose (GLUT and SGLT), amino acids and ions (various channels and carriers), and water (aquaporins)
How much of filtered sodium , water, glucose, and amino acids are reabsorbed?
99-100%
Substances are reabsorbed out of the tubule lumen into the ________ _____ and then ________ _______ to continue through circulation.
interstitial space, peritubular capillaries
What distinct barriers must a substance cross in order to be reabsorbed?
The luminal membrane, the cytosol, the basolateral cell membrane, the interstitial fluid, and the capillary wall.
What path does Na+ follow for reabsorption?
Lumen —> tubular cell —-> the basolateral Na+/K+ pump —> interstitial fluid —> capillary
What path does Cl- follow for reabsorption?
lumen —> CFTR or ClC channel —> tubular cell lateral space —> interstitial fluid —> capillary
What path does H2O follow for reabsorption?
lumen —> AQP-1 water channel —> proximal tubular cell (following sodium) —> AQP-1 water channel (next to the basolateral Na+/K+ pump) —> interstitial fluid —> capillary
When are channels and carriers for important substances present in the proximal tubule?
Always present
What is reabsorption for important substances in the distal tubule and collecting duct regulated by?
Hormones
How do hormones regulate reabsorption of important substances in the distal tubule and collecting duct?
They stimulate the presence of channels and carriers. Allows body to balance substances
What major hormones regulate reabsorption in the distal tubule and collecting duct?
Vasopressin and aldosterone
What processes are driven by the Na+/K+ ATPase pump in the tubule cell basolateral membrane?
Transport of sodium by channels and carriers from tubule lumen through apical cell membrane into cell, water and chloride reabsorption, and the activity of glucose and amino acid carriers
What hormones act on the distal tubule and collecting duct and what do they do?
Aldosterone increases the number of tubule cell sodium pumps and channels for sodium reabsorption. Vasopressin increases water absorption by increasing the number of aquaporin channels (AQP-2)
How is water reabsorbed in the proximal tubule?
Passively by osmosis through aquaporin (AQP-1) channels.
___% of glucose is typically reabsorbed along proximal tubule.
100
What happens in the proximal tubule if blood glucose concentrations are too high?
Glucose will be reabsorbed from the tubule until reaching a threshold, after which, glucose begins to be excreted in the urine.
It is important for the animal to regulate the rate of _____ filtration in the kidney.
Plasma
What does too much plasma filtration result in?
The loss of important substances and water.
What do mechanisms that regulate plasma filtration involve?
Modifications to the glomerulus
What is glomerular filtration rate (GFR)?
The volume of plasma filtered from the renal glomerular capillaries per unit of time.
What is the GFR of an adult human?
115-125 ml/min or 180 L/day
What does GFR mostly depend on?
Net filtration pressure in glomeruli
GFR reflects ______ function.
kidney
The structure of the glomerulus promotes _______.
Filtration
Which is smaller, efferent arteriole radius or afferent arterial radius?
Efferent arteriole radius
What does the smaller radius of efferent arterioles cause?
An increase in capillary blood pressure in the glomerulus
What does the increase in capillary blood pressure in the glomerulus do?
It helps to overcome opposing pressures, resulting in a net filtration pressure in tubule.
What can influence net filtration pressure?
Changes in afferent arterial pressure
Reducing the radius of afferent arterioles _____ blood flow into the glomerulus and ______ friction. Achieved by special ______ ______ cells.
reduces, reduces, smooth muscle
What are the smooth muscle cells around afferent arterioles called?
Juxtaglomerular cell or JG cells
Why is the fluctuation of afferent arteriole pressure important?
Important to correct for fluctuations in animal mean arterial pressure that would affect filtration and animal water or solute balance.
An increase in MAP would greatly ______ GFR and animal solute and water loss.
increase
Vasoconstriction _______ blood flow into the glomerulus and _______ GFR.
decreases, decreases
Vasodilation ______ blood flow into the glomerulus and _______ GFR.
increases, increases
___________ prevents unintentional shifts in GFR and solute and water loss due to changes in MAP.
Autoregulation
What mechanisms achieve autoregulation?
Myogenic activity and tubuloglomerular feedback
What is the myogenic activity of the afferent arterioles?
The more the JG cells stretch due to increases in blood pressure, the more they constrict, reducing blood flow into glomerulus
What is tubuloglomerular feedback?
The distal tubule senses changes in sodium concentrations and filtrate volume in tubule due to changes in GFR. Special distal tubule cells (the macula densa) sense sodium and filtrate volume and release paracrine factors that effect JG cell constriction.
What paracrine factors does the macula densa release?
ADP, adenosine, and nitric oxide
What is the juxtaglomerular apparatus (JGA)?
Location where the ascending distal tubule, after the loop of henle, contacts glomerulus.
What does the juxtaglomerular apparatus involve?
Paracrine communication between the macula densa and juxtaglomerular cells.
What extrinsic factor controls GFR?
The sympathetic nervous system
How does the sympathetic nervous system effect GFR?
It constricts JG cells, causing afferent arterial vasoconstriction, decreasing GFR and solute and water loss. Helps to avoid filtration and maintain blood volume and pressure.
What does sympathetic control of GFR contribute to?
Long-term adjustment of blood volume and pressure by avoiding plasma filtration and solute and water loss.
Low blood pressure within the heart triggers activation of sympathetic neurons that extend directly to the kidneys. This ______ afferent arteriole, _______ GFR, and ________ blood volume.
constricts, reduces, increases
The sympathetic nervous system also triggers _____ secretion from JG cells that activate the ___________________ system, increasing blood volume and pressure.
renin, Renin-Angiotensin-Aldosterone
What is the Renin-Angiotensin-Aldosterone system triggered by?
Low blood pressure sensed by baroreceptors (extrinsic), low blood pressure in kidney sensed by JG cells (intrinsic), low sodium and filtrate volume sensed by the macula densa (intrinsic)
What are the steps of the Renin-Angiotensin-Aldosterone system?
- Renin secreted by JG cells into blood
- Renin converts angiotensinogen to angiotensin I
- Angiotensin I converted to angiotensin II (ACE enzyme)
- Angiotensin II travels to adrenal cortex causing it to secrete aldosterone
- Aldosterone travels to kidney, increasing sodium reabsorption from tubule system.
- Water follows sodium by osmosis in tubule system
- Water enters bloop, increasing MAP.
Where is angiotensinogen converted to angiotensin I?
In the blood
Where is angiotensin I converted to angiotensin II?
In the lungs
Where is aldosterone secreted into?
The blood
____________ and activation of __________ stimulate vasopressin release from animal posterior pituitary.
Angiotensin II, osmoreceptors
What stimulates animal thirst and salt hunger?
Angiotensin II
What does aldosterone increase in relation to sodium and potassium channels?
Increases gene transcription of sodium and potassium channels that are distributes along the kidney distal tubule and collecting duct apical membrane.
Along the apical membrane, Na+ is transported into the ____ and K+ is transported into the _____ _____.
cell, tubule lumen
What does aldosterone increase in relation to sodium-potassium ATPase pumps?
Increases transcription of sodium-potassium ATPase pumps that are distributed along the basolateral cell membrane.
Along the basolateral membrane, sodium is pumped into the ________ ____. Water follows by osmosis through ________.
interstitial space, aquaporins
What does increased K+ stimulate and what does this help with?
Aldosterone secretion from the adrenal cortex, helps remove excessive K+ from the animal body.
What are atrial natriuretic peptides (ANPs) released by?
Heart atria myocardiocytes in response to increase blood volume/pressure.
What are the functions of ANPs?
Reduce sympathetic output to heart and arteriole smooth muscle, which reduces CO, TPR, and MAP. Inhibits the Renin-Angiotensin-Aldosterone system, increasing kidney sodium and water secretion in urine, reducing blood volume.
When an animals is in ideal fluid balance, an ______ _____ is produced at a moderate rate.
Isotonic urine
How does solute or osmotic pressure of isotonic urine compare to normal tissues?
The same (usually 300 mOsm in animals)
What happens when an animal is in dehydration?
The kidneys produce a small amount of concentrated urine (low water volume, high solute concentration)
What is anti-diuresis?
Decreased production of urine
What happens when an animal is hydrated?
The kidneys produce a large amount of dilute urine (large water volume, low solute concentration)
What is diuresis?
Increased production of urine
What is reabsorption of water in the loop of henle accomplished by?
Action of vasopressin on the distal tubule and collecting duct
What is mOsm when entering the medulla before the loop of henle?
300 (equal to location in medulla)
What is mOsm after the loop of henle/first water absorption?
600 (equal to location in medulla)
What is mOsm after the second water absorption?
900 (equal to location in medulla)
What is mOsm after the third water absorption?
1200 (equal to location in medulla
What is mOsm before first NaCl absorption?
1000
What is mOsm after first NaCl absorption?
700 (medulla at 900)
What is mOsm after second NaCl absorption?
400 (medulla at 6000
What is mOsm after third NaCl absoprtion/when leaving the medulla)?
100 (cortex at 300)
What is mOsm when entering the medulla in the distal tubule?
100 continuously as the tubule descends
Is water reabsorbed in the distal portion of the nephron?
No
Filtrate in the proximal tubule is ______ with the surrounding cortex region.
isotonic
The descending limb of the loop of henle is _______ to water.
permeable
Describe water permeability in the hairpin and thin ascending limb of the loop of henle.
Low water permeability but permeable to sodium due to leak channels. Sodium leaves lumen into medulla tissues
Describe solute transport and water permeability in the thick ascending limb of the loop of henle.
Sodium and chlorine actively transported out of the lumen, impermeable to water. Sodium pumped out, water stays in.
The medulla interstitial fluid becomes __________ and the exiting loop filtrate is ______ as it enters the distal tubule and collecting duct.
osmoconcentrated, dilute