Chapter 26 - Urinary System

Front 1

what are the functions of the urinary system?

Back 1

Filtering of blood
Regulation of blood volume through water and salt resorption and retention
excretes wastes

Front 2

what percentage of what enters the kidneys is actually excreted?

Back 2

1%
99% is resorbed

Front 3

function of:
Perirenal fat

Back 3

Perirenal fat - Engulfs renal capsule and acts as cushioning
for protection from trauma

Front 4

what parts of the kidney are considered the cortex?
The medulla?

Back 4

Cortex: Outer area and
Renal columns which extend inward
Medulla: Inner area, only the
Renal pyramids

Front 5

what is the nephron?

Back 5

Nephron: Functional unit of kidney
The smallest piece of the kidney that can operate as a kidney

Front 6

Is the renal cortex hypo- or hyper- osmotic?

Back 6

Hypo-osmotic = less solutes

Front 7

Is the renal medulla hypo- or hyper- osmotic?

Back 7

hyperosmotic = more solutes in it so it draws water into it.

Front 8

describe the path of fluids that leave the blood and enter the kidney.

Back 8

Fluid leave the blood and enter the renal corpuscle (the filter) then the proximal tubule, then the descending limb of loop of Henle, then the ascending limb of loop of Henle, then the destal tubule, the the collecting ducts which lead to a minor calyx.

Front 9

why is it important that the medulla is hyperosmotic?

Back 9

the hyperosmotic state of the medulla cause water to move out of the nephron and into the interstitial fluid thru passive osmosis. If this didn't occur, dehydration would result

Front 10

where does the water move out of the nephron and into the interstitial fluid?

Back 10

in the descending limb of the loop of Henle and collecting ducts

Front 11

what helps increase water resorption in the collecting duct - how?

Back 11

ADH increases permeability of the collecting ducts allowing more water to move out.

Front 12

what kind of transport occurs in the cortex?

Back 12

Active transport of Na+ which causes H2O to be resorbed

Front 13

What is the filtration unit of the renal corpuscle?

Back 13

the Bowman's capsule

Front 14

what is the cardiovascular unit of the renal corpuscle?
Define afferent and efferent

Back 14

the glomerulus
Afferent
Blood to glomerulus
Efferent
Drains

Front 15

How does filtrate move through the kidney?

Back 15

Filtrate moves down the pressure gradient
Collecting ducts have the highest pressure because they have smallest diameter.
Then thru papillary ducts, then minor calyx and then major calyx and then the renal pelvis - which has the lowest pressure b/c largest diameter

Front 16

describe the path of blood in the kidney

Back 16

arcuate artery to afferent arteriole and into the glomerulus (the capillary bed). Blood plasma leaves the glomerulus and enters the Bowman's capsule. Blood that doesn't move into the Bowman's leaves the glomerulus in the efferent arteriole, then to the peritubular capillaries, then to the vasa recta then to arcuate vein

Front 17

what happens to the water that moves out of the descending limb and collecting ducts?

Back 17

It's picked up by the peritubular capillaries and the vasa recta, returning the water to the circulatory system through the arcuate vein and renal vein

Front 18

describe the bowman's capsule.

Back 18

Bowman’s capsule
Parietal layer
Visceral layer - only allows very small substances to filter through (Na+ and H2O)

Front 19

what can't pass through the Bowman's capsule?

Back 19

protein and blood cells

Front 20

what is renal filtrate?

Back 20

Plasma (water and small ions) minus blood cells and blood proteins
Most (99%) reabsorbed

Front 21

describe urine formation

Back 21

fluid leaves the blood and goes into the nephron becoming filtrate
sodium and H2O leave the nephron
anything left (1%) goes out as urine

Front 22

describe the filtration membrane

Back 22

Fenestrated endothelium, basement membrane and pores formed by podocytes in the vesceral layer of the Bowman's capsule

Front 23

what is GCP?

Back 23

Gomerular capillary pressure = causes fluid to leave blood (overcomes CP and COP)

Front 24

What is CP?

Back 24

Capsule pressure = pressure in the opposite direction resisting the GCP

Front 25

what is COP

Back 25

Colloid osmotic pressure = pressure in the opposite direction resisting GCP

Front 26

what is the formula for filtration pressure?

Back 26

GCP - COP - CP = filtration pressure

GCP must be more than COP and CP combined in order for fluid to move out of glomerulus

Front 27

what does hyponutremic mean?

Back 27

not enough Na+

Front 28

describe tubular reabsorption

Back 28

Active transport moves Na+ across nephron wall which sets up the gradient to that H2O can move passively
Other ions and molecules moved by cotransport
Passive transport moves water, urea, lipid-soluble, nonpolar compounds

Front 29

what are the structures responsible for H2O resorption?

Back 29

proximal tubules
descending limb of loop of Henle
ascending limb
collecting ducts

Front 30

where is most N2O resorbed?

Back 30

in the proximal tubules (65%)

Front 31

describe water absorption in the proximal tubules

Back 31

Na+ and other substances removed by active transport
Then water can follow passively
Filtrate volume reduced

Front 32

describe fluid movement in the descending limb of the Loop of Henle (in the renal medulla)

Back 32

Water exits passively, solute enters
Filtrate volume reduced 15%

Front 33

describe fluid movement in the ascending limb of the Loop of Henle

Back 33

There is no water absorption here!
Na+, Cl-, K+ actively transported out of filtrate
Water remains because the ascending limb of Loop of Henle is water impermeable

Front 34

describe fluid movement in the collecting ducts

Back 34

Water movement out regulated by ADH (1% - 19% resorbed here)
If absent, water not reabsorbed and dilute urine produced
If ADH present, water moves out, concentrated urine produced

Front 35

How does low ADH affect H2O absorption in the collecting ducts?

Back 35

water not reabsorbed and lots of dilute urine produced
Fewer pores in the collecting ducts so H2O stays in the nephron

Front 36

How does high ADH affect H2O absorption in the collecting ducts?

Back 36

water moves out, concentrated urine produced
more pores in the collecting ducts so more water is resorbed and less urine is produced

Front 37

where are the collecting ducts?

Back 37

in the renal medulla

Front 38

describe countercurrent flow mechanism

Back 38

Blood moves in the opposite direction of the urine

Front 39

why does blood entering the vasa recta have almost the same osmolality as blood leaving the vasa recta?

Back 39

b/c even though the movement of Na+ into the blood at the ascending limb increases osmolality of the blood, that's cancelled out by water moving into the vasa recta at the descending limb

Front 40

most water resorption occurs in the _______________ of the nephron

Back 40

proximal tubule (65%)

Front 41

why does most water absorption happen in the proximal tubule?

Back 41

b/c this is where Na+ is actively absorbed which causes water to passively follow

Front 42

what happens when a large amount of water is consumed?

Back 42

there's a decrease in ADH b/c you don't need to resorb as much water. So, decreased ADH causes decrease pores in collecting ducts. More water stays in the nephron and is secreted as diluted urine

Front 43

what happens when water is not consumed?

Back 43

there's an increase in ADH which causes more pores in collecting ducts, which then causes more water resorption and a little highly concentrated urine.

Front 44

what are the steps in the ADH mechanism creating more water resorption?

Back 44

1. ADH binds to ADH receptor in the basal membrane of collecting ducts which
2. activates the G protein
3. G protein the activates adenylate cyclase
4. adenylate cyclase produces cyclic AMP which is a second messenger which
5. increase number of water channels, which increases passive resorption

Front 45

How do the following hormones affect water resorption?
ADH
Aldosterone
Renin
Atrial nautriuretic hormone

Back 45

increases
increases
increases
decreases

Front 46

define plasma clearance

Back 46

Volume of plasma cleared of a specific substance each minute

Front 47

define tubular load

Back 47

Total amount of substance that passes through filtration membrane into nephrons each minute
Normally glucose is almost completed reabsorbed

Front 48

what is tubular maximum?

Back 48

Maximum rate at which a substance can be actively absorbed
Each substance has its own tubular maximum

Front 49

what happens if a substance is present in greater concentrations than the tubular maximum?

less than the tubular maximum?

Back 49

then the substance can't be resorbed and it will be secreted into the urine

then there will be none in urine

Front 50

what moves urine through the nephron?

through the ureters?

Back 50

hydrostatic pressure

peristalsis

Front 51

describe the micturition reflex

Back 51

Stretch of urinary bladder stimulates reflex causing bladder to contract, inhibiting urinary sphincters
Higher brain centers can stimulate or inhibit reflex

Front 52

Osmolality = what?

Back 52

solutes
= ---------
solvent

how much Na+ is dissolved in the plasma of blood

Front 53

what is responsible for osmolality

Back 53

the solvent - water

Front 54

what is the primary regulator of osmolality of blood, fluid balance, and water excretion in the body?

Back 54

the kidneys

Front 55

what is ECF?

Back 55

extracellular fluid osmolality

Front 56

what does increased ECF osmolality do?

decrease ECF osmolality?

Back 56

Triggers thirst and ADH secretion

Inhibits thirst and ADH secretion

Front 57

increased ECF volume results in?

Back 57

decreased ADH secretion which results in decrease water resorption and thus less ECF volume

Front 58

Decreased ECF volume results in?

Back 58

increased ADH secretion which increases water resorption and thus increases h2o in ECF

Front 59

what happens if ECF osmolality is too high?

Back 59

then increased ADH is secreted which increases h2o resorption, which dilutes the ECF and decreases osmolality.

Front 60

what happens if ECF osmolality is too low?

Back 60

then decreases ADH is secreted which decreases h2o resorption, which concentrates the ECF and increases osmolality.