Download 14. Renal System Part 1

Renal System:
Functional unit
is the Nephron.
Kidneys (2)
Ureter (2)
Bladder (1)
Urethra (1)
Functions of the Renal System
1) Regulates ECF volume:
a) Regulates Osmolarity:
b) Regulates ion balance:
2) Regulates pH of body fluids:
Functions of the Renal System
3) Eliminates metabolic waste:
4) Removes foreign substances:
5) 2o Endocrine gland:
a) erythropoietin
b) renin
Outer
renal cortex
Inner
renal medulla
~ 1.25 million
nephrons in
each kidney
~ 180 Liters of
Filtrate made
each day
~ 1.5 Liters of
urine excreted
each day
The Nephron
1. Renal Corpuscle
a) Glomerulus
b) Bowman’s Capsule
c) Bowman’s Space
2. Renal Tubule
a) Proximal CT
b) Loop of Henle
c) Distal CT
In Human Renal System
~85% are Cortical nephrons
– Renal corpuscle higher in cortex.
– Shorter loop of Henle.
~15% are Juxtamedullary nephrons
– Renal corpuscle closer to medulla.
– Loop of Henle extends deep into medulla.
Nephrons
1. Renal Corpuscle (3 parts)

Glomerulus

Bowman’s Space

Bowman’s Capsule
Filtration:
Reabsorption:
Secretion:
Excretion:
Overview of the Renal Process in Nephron
Barriers to Filtration
1. Endothelium
Restricts cells
2. Basement Membrane
Restricts proteins
3. Podocytes
Changes Glomerular Filtration Rate (GFR)
Filtration is favored by
Hydrostatic Pressure
(HP) of Glomerulus.
Opposed by Colloid
Osmotic Pressure
(COP) of blood.
Opposed by
Hydrostatic Pressure
of Bowman’s capsule.
Glomerular Filtration Rate (GFR)
e.g., normally GFR is 180L/day (or 125ml/min)
Things that can influence GFR:
• Changes in blood pressure can change
GFR but this is autoregulated.
Autoregulation of Renal System
Juxtaglomerular Apparatus is:
Macula Densa - specialized portion of the DCT that
sits in between the Afferent and Efferent arteriole
Juxtaglomerular (JG) cells - cells predominantly
around afferent arteriole to adjust diameter.
• Autoregulation
1. Myogenic Stretch
2. Tubuloglomerular Feedback
1. Myogenic Stretch
If ↑ blood pressure in afferent arteriole, this
stretches smooth muscle and it contracts in
response, thus vasoconstricts.
This decreases blood flow (↓ pressure & GFR)
Arteriole Resistance Changes Blood flow and GFR
Juxtaglomerular
Apparatus
2. Tubuloglomerular Feedback
• ANS-Sympathetic Modulation
Both Afferent and Efferent Arterioles are
innervated by SYM neurons.
NE binds to  receptors on smooth muscle,
causing vasoconstriciton.
e.g., if hemorrhage or dehydration,
↑ Sym, vasoconstriction,
↓GFR, conserves fluid volume.
• Hormones
– Angiotensin II – vasoconstrictor.
– Prostaglandins – vasodilator.