Biology 212
Anatomy & Physiology I
Dr. Thompson
Renal
Renal (Urinary) System
Primary function:
Disposes of
while retaining
Organs of Renal System
Kidney
Mass ~ 150g
Size ~ 12 cm x 6 cm x 3 cm
Kidney
Capsule:
Cortex:
Medulla:
Pelvis:
Kidney:
This is where filtration will
occur to begin formation of
urine (more on that in a
moment).
Each renal artery divides
into lobar arteries,
interlobar arteries,
arcuate arteries,
interlobular arteries,
afferent arterioles,
glomeruli,
efferent arterioles,
peritubular capillaries
Blood then flows into
interlobular veins or
arcuate veins,
interlobar veins, and
lobar veins to reach the
renal vein which carries it to
the inferior vena cava.
Let’s go back to the glomerulus:
This series of tubes is called
a nephron.
Each kidney contains ~ 1,000,000 nephrons
Pattern of nephrons creates pattern of cortex and medulla:
Functions of nephrons:
Thus:
Primary function of renal system: Maintains homeostasis
by regulating concentrations of both water and solutes in
the blood.
Disposes of metabolic wastes
excess water
excess ions
toxins
while retaining proper amount of water
proper concentrations of ions
nutrients
anything else needed in blood
Two types of “pressure” are involved in these processes of
filtration, reabsorption, and secretion.
1)
2)
Two types of “pressure” are involved in these processes of
filtration, reabsorption, and secretion.
A.
Two types of “pressure” are involved in these processes of
filtration, reabsorption, and secretion.
B.
Filtration
Structure of Glomerulus
Filtration:
a)
b)
c)
Thus: only things smaller than
~ 7 nm can be filtered from
blood into urine
Filtration:
In general:
This fluid filtered out of the blood flows into
As this filtrate passes through the nephron:
a) Most solutes needed by
body & most of the water
are reabsorbed back into
the blood in peritubular
capillaries
b) Excess solutes & excess
water stay in urine
c) Additional unwanted ions
and molecules secreted
into urine
Key Feature of Kidney:
Nephrons can concentrate urine by reabsorbing most of
the water filtered out of the glomerulus
Substance:
Water ( L )
Sodium ( g )
Glucose ( g )
Urea ( g )
Amount
filtered
per day
180
630
180
54
Amount
excreted
per day
1.8
3.2
0
30.0
Reabsorption
(%)
99
99.5
100
44
Key Feature of Kidney:
(Nephrons concentrate urine by reabsorbing most of the water filtered
out of glomerulus. This requires kidney to create a large concentration
gradient in extracellular fluid of medulla, surrounding loops of Henle)
Key Feature of Kidney:
(Nephrons concentrate urine by reabsorbing most of the water filtered
out of glomerulus. This requires kidney to create a large concentration
gradient in extracellular fluid of medulla, surrounding loops of Henle)
Low osmolarity (concentration of solutes) closer to cortex
High osmolarity (concentration of solutes) deeper in medulla
so that
As newly formed urine passes
through collecting, most of the
water will diffuse out of collecting
duct, into the extracellular fluid,
from which it will diffuse back into
blood of the peritubular capillaries,
leaving high concentration of
solutes in urine which reaches pelvis & leaves kidney
Your text goes into great detail about how this happens
(including these diagrams):
You don’t need to understand details, but you should
understand that it allows the final urine to be concentrated by
pulling water out of it as it passes through the collecting duct.
How much water gets pulled out can increase or decrease if
body needs to retain or lose water. This is under control of
(How much water gets pulled out can increase or decrease if body needs to
retain or lose water. This is under control of antidiuretic hormone (ADH)
produced by posterior pituitary).
Increase
in ADH
Decrease
in ADH
Kidney also has important function in regulating systemic
blood pressure.
(Each nephron has a juxtaglomerular apparatus which detects blood
pressure in afferent arteriole and secretes hormone renin. The lower
the blood pressure in the afferent arteriole, the more renin the
juxtaglomerular apparatus will secrete.)
Urine passes from
Urine leaving the pelvis
enters
Ureters:
Ureter:
Mucosa:
Muscularis:
Adventitia:
Urinary Bladder:
Urinary Bladder:
Mucosa:
Muscularis:
Adventitia
Serosa
Urinary Bladder:
Urethra:
Adventitia:
Muscularis:
Mucosa:
Urine not modified in ureter
bladder
urethra
Thus:
Also:
Tonight:
On yourself or another person, locate kidneys
ureters
bladder
urethra