Urinary System Ch. 23—Saladin

Front 1

KIDNEY PATHWAYS

Back 1

Pathway of urine & Pathway of blood through nephron

Front 2

Pathway of urine

Back 2

glomerular capsule  proximal convoluted tubule  nephron loop  distal convoluted
tubule  collecting duct  papillary duct  minor calyx  major calyx  renal pelvis  ureter
 urinary bladder  urethra

Front 3

Pathway of blood through nephron

Back 3

-afferent arteriole (incoming)
-efferent arteriole (outgoing)
-glomerulus is between them
afferent art.  glomerulus  eff. arteriole

Front 4

URINE FORMATION

Back 4

1) glomerular filtration

2) tubular reabsorption

3) tubular secretion

urine = wastes and excess water and electrolytes to be excreted from body
uses a balance of three processes

Front 5

1) glomerular filtration

Back 5

-plasma is filtered by the capillaries of the glomerulus
-fluid moves from capillaries out into the glomerular capsule
-180 L filtered every 24 hours (more than 4x total body water!)

-most of this water is returned to blood by the second process:

Front 6

2) tubular reabsorption

Back 6

-moves substances from renal tubules to blood in peritubular caps.
-“keeping the good stuff”
-retains water, electrolytes, glucose, amino acids, bicarbonate ion
-wastes are not reabsorbed, but are eliminated by the third process;

Front 7

3) tubular secretion

Back 7

-moves substances from blood in peritubular caps. to renal tubules
-“getting rid of the bad stuff”
-these substances are then eliminated in urine
-secretes wastes (such as ammonia), excess electrolytes, also drugs

Front 8

Summary of urinary excretion

Back 8

urinary excretion = glomerular filtration + tubular secretion – tubular reabsorption

Front 9

Glomerular Filtration Rate (GFR)

Back 9

-depends on glomerular hydrostatic pressure
-the pressure of water in blood pushing out of the glom. caps.
-this is BP within the glomerular caps.

-usually high compared to other body caps., so filtration rate is relatively
high

Front 10

normal GFR of both kidneys

Back 10

is about 125 ml per minute, 180 L in 24 hours (about 45 gallons!)
-this means all of your plasma is filtered about 25 times a day
-most of this fluid is reabsorbed (by tubular reabsorption) and re-enters plasma
-about 0.6 – 2.5 L becomes urine per day

Front 11

Control of Filtration Rate

Back 11

1) myogenic mechanism

2) juxtaglomerular apparatus

3) Renin-angiotensin-aldosterone system

Front 12

1) myogenic mechanism

Back 12

-myogenic = produced by muscle
-an autoregulatory system (kidney regulates itself without input from NS or endocrine system)
-keeps GFR relatively constant during normal changes in systemic BP
-afferent arteriole’s smooth muscle can constrict or dilate
-controls flow of blood into glomerular caps.

Front 13

1) myogenic mechanism pathways

Back 13

systemic BP increases  aff. art. constricts  blood flow into glom. remains
constant  GFR remains constant
OR systemic BP decreases  aff. art. dilates  blood flow into glom. remains
constant  GFR remains constant

Front 14

2) juxtaglomerular apparatus

Back 14

-also an autoregulatory mechanism of the kidney (does not require NS or hormones)
-tweaks the GFR to maintain relatively stable rate during normal systemic BP changes
-uses two types of cells: jg cells & Mascula densa cells

Front 15

JG cells on afferent arteriole

Back 15

-enlarged, specialized smooth muscle cells

-dilate or constrict to control flow through aff. art.
-this effect controlled by secretions from the macula densa cells
-mechanism still not clearly understood

JG cells also secrete renin,

Front 16

macula densa cells on DCT

Back 16

-somehow monitor flow and composition of fluid in DCT
-secrete substances to cause JG cells to dilate or constrict, as needed

Front 17

How the JG apparatus works (1)

Back 17

1) macula densa senses increase in GFR
2) secretes some messenger that goes to JG cells
3) JG cells contract, constricting the aff. art.
4) GFR is reduced to normal

Front 18

How the JG apparatus works (2)

Back 18

1) macula densa senses decrease in GFR
2) secretes some messenger that goes to JG cells
3) JG cells relax, dilating the aff. art.
4) GFR is increased to normal

Front 19

3) Renin-angiotensin-aldosterone system

Back 19

a) angiotensinogen

b) renin

c) angiotensin-converting enzyme (ACE)

d) angiotensin II

Front 20

a) angiotensinogen

Back 20

-made by the liver

Front 21

b) renin

Back 21

-made by JG cells of kidney
-converts angiotensinogen to angiotensin I

Front 22

c) angiotensin-converting enzyme (ACE)

Back 22

-produced by lungs
-converts angiotensin I to angiotensin II