Urinary System Flashcards
principal organs of excretion in humans
lungs, liver, skin, kidneys
What is the function of the kidney?
to maintain proper solute concentration in the blood through formation and excretion of urine
3 regions of the kidney
outer cortex, inner medulla, renal pelvis
what is a nephron?
a bulb called bowman’s capsule–> encapsulates a capillary bed known as the glomerulus–> lead to a long series of tubes known as: proximal conv tube; loop of henle; distal conv tubule; collecting duct
how is the nephron position?
loop of henle and collecting duct run through medulla while the Bowman’s capsule and convoluted tubules are in the outer/renal cortex
how does concentrated urine get excreted?
concentrated urine flows into the renal pelvis through a funnel like region that opens into the ureter–>ureters from the kidney empty into the urinary bladder, where urine collects and is expelled via the urethra
what surrounds the nephron, and what is its purpose?
a complex peritubular capillary network that facilitates reabsorption of amino acids, water, salts, and glucose
how is urine formed?
filtration, secretion, reabsorption
describe filtration
- -blood pressures for 20% of the blood from the blood stream into the BC through the capillaries
- -fluids and small solutes entering the glomerulus are called filtrate (which is isotonic with the blood)
- -is a passive process–the hydrostatic pressure from the blood drives the process of filtration; if blood pressure increases, hydrostatic pressure increases, and this exerts extra pressure on kidney tissues leading to damage over time
describe secretion
nephron secretes waste (e.g. ions, acids, metabolites) from intestinal fluids into the filtrate via passive and active processes–happens mostly in the dist. conv. tub
describe reabsorption
essential substances such as glucose, salts, and water, are reabsorbed from the filtrate into the blood
–occur mainly in the proximal convoluted tubule; is mainly an active process; movement of these molecules causes the passive movement of water as well; creates concentrated urine, hypertonic to the blood–happens mostly in the prox conv tub
primary function of nephron
to clean out unwanted substances from the blood
how does the nephron achieve its primary function?
- -will selectively rabsorb substances back into plasma from the filtrate
- -nutrients reabsorbed at prox conv tub
- -loop of H and collecting duct have roles in water, Na, and K concentrations in the nephron
- -dist conv tub is the major site for secretion of substances into filtrate
describe the loop of H permeabilities
descending loop v permeable to water but not Na or K; thin part of the ascending loop v permeable to Na and K but not to water; thick part of the ascending loop Na, K, and Cl are actively reabsorbed by from the urine
describe the osmolarity gradient in tissues which forms concentrated urine
tissue osmolarity increases from the cortex to inner medulla; the gradient depends on the counter-current multiplier system–a system in which energy is used to establish an osmolarity gradient
how does the counter-current multiplier system affect the tissues in the kidney?
causes the interstitual space in the medull to be hyperosmolar (containing more osmolytes) compared to the dilute filtrate; as water flows down the collecting duct to the the renal pelvis and ureter, water flows from the duct into the tissues via osmosis as the tissue is hyperosmolar (water returns to systemic circulation via capillaries in the medulla); the amount of reabsorption of water depends on the permeability of the collecting duct to water
How is permeability of the CD controlled?
via antidiuretic hormone (aka vasopressin); ADH INCREASES the permeability of the CD to water, allowing water to flow out into the medulla and a more concentrated urine to form; some disease states cause people to released too much ADH and retain too much fluid
how does aldosterone affect the kidney?
a steriod hormone that increases transport of Na and K in the dist. conv. tub and CD; results in a decreased excretion of Na and an increased excretion of K into the urine; water flows into urine?? more dilute?? has the same affect as ADH
aldosterone does not affect renal blood flow
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how do ADH and aldosterone differ?
o ADH has the same net effect of increased water reabsorption as aldosterone
♣ However, ADH directly affects water absorption b ythe DCT and CD, opening additional aquaporins—allows water to be reabsorbed more readily
♣ Both ADH and aldo. Cause a decrease in urine output and a corresponding increase in blood pressure
♣ This allows the human body to compensate for periods of dehydration or other causes of low blood pressure
Diuretics
–caused more water to go into urine; loop diuretics inhibits the ascending loop’s uptake of Na; thiazide diuretics inhibit the Na-Cl transporter in the DCT; both have the same net affect of creating a more dilute urine
How does the kidney maintain a consistent body fluid pH?
kidney removes CO2 (from lungs) and H ions
How is pH assessed clinically?
arterial pH, arterial partial pressure of CO2, plasma bicarbonate ions (HCO3-)
What are the two types of acid-bases disorders?
respiratory acidosis and alkalosis (affects blood pH by increases Pco2, metabolic acidosis and alkalosis(affects blood pH by causing changes in HCO3- concentration)
describe respiratory acidosis
increased Pco2; blood pH decreases, body compensates by increasing HCO3-;
describe metabolic alkalosis
increased HCO3-, increases pH, increase Pco2
describe metabolic acidosis
decreased HCO3-, decreased pH, decreased Pco2
describe respiratory alkalosis
decreases pco2, increased pH, decrease HCO3-
♣ Compensation mechanisms that affect Pco2 are performed by the respiratory system and can effect change quickly
♣ However, compensation mechanisms that affect HCO3- are performed by the kidneys
• Therefore the compensatory effect can take longer to manifest
• Changes in acid-base chemistry within the body, as well as the cause of the change (respiratory or metabolic), dictate how a patient will be treated medically
• E,g, a change in pH due to a change in respiratory rate or function may be the result of airway obstruction or chronic obstructive pulmonary disease (COPD)
o Whereas metabolic acidosis may be due to a kidney dysfunction or volume loss;
• These diseases must be treated accordingly
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