Download tutorial 1 GUS

• The functional unit of the kidneys is the
_____________________.
• Urine is eliminated from the bladder through the
______________.
• The two regions of the kidney are an outer
______________and an inner _______________.
• Tubular _____________________ and tubular
_____________________ are selective processes
that occur in the nephron.
• The specialized cells of the
_____________________, located within the
_____________________, detect changes in
the rate at which fluid is flowing past them
through the distal tubule.
Regional differences in nephron structure
 Cortical nephrons
- have glomeruli located in the ------------------------.
- have ______________loops of Henle that
penetrate only a short distance into the
________________
Regional differences in nephron structure
(cont.)
 Juxtamedullary nephrons.
- have glomeruli that lie ______________cortex
near the medulla
- have ______________loops of Henle that dip
deeply into the _________________.
• have specialized peritubular capillaries
_________________
• The kidney produces following hormones :
• Erythropoietin
• 1,25 dihydroxycholecalciferol (Vitamin D3,
calcitriol)
• Renin
• The fluid within the Bowman’s capsule virtually the
same as in the plasma.
• Except
• It is free from:
– _______________
– ________________
• Fluid filtered pass through three layers of the
glomerular membrane
• ________________________
• _________________________
• __________________________
GFR:
Definition:
The volume of plasma filtered from both kidneys
per minute.
• GFR = _______ ml/min = _______ liters/day
• GFR= _____________ x ______________
• Forces determining Net Filtration Pressure
(NFP)
– ___________________
– ____________________
– ________________________
• NFP =
( PGC + BC ) -
( PBC + GC )
• Calculate NFP if
– Glomerular capillary hydrostatic pressure = 60
– Plasma colloidal osmotic pressure is = 40
– Bowman's capsule hydrostatic pressure is = 10
– Ans = 10
• Increase of PBc can be caused by
1. _________________________
2. _________________________
3. _________________________
• plasma colloid osmotic pressure
increases ________________
Decreases __________________
Adjustments of Afferent
Arteriole Caliber to Alter
The GFR
Baroreceptor Reflex
Influence on the GFR
Autoregulation
The major function of autoregulation in the kidneys is
to maintain a relatively constant GFR and renal blood flow
despite considerable arterial pressure fluctuations that
can occur.
Autoregulation:
• Myogenic autoregulation
TWO
THEORIES
• Tubuloglomerular feedback
Myogenic Mechanism
Vascular smooth muscle contraction in response to increased stretch
Arterial
Pressure
Stretch of
Blood Vessel
Cell Ca++
Permeability
Blood Flow
Vascular
Resistance
Intracell. Ca++
Macula Densa Feedback
(Tubuloglomerular feedback)
GFR
Distal NaCl
Delivery
Macula Densa NaCl Reabsorption
(macula densa feedback)
Afferent Arteriolar Resistance
GFR (return toward normal)
What is a Glomerular Filtration Fraction?
• The Filtration Fraction (FF) is the ratio of the
GFR to the renal plasma flow (GFR/TRPF).
• Renal blood flow = 1.1 L/min
• 20-25% of total cardiac output (5 L/min).
• Of the 625 ml of plasma enters the glomeruli via the
afferent, 125 (the GFR) filters in the Bowman’s
capsule, the remaining passing via efferent arterioles
into the peritubular capillaries
• Filtration fraction = (GFR/TRPF) = 0.2
• So, GFR is About 20% of the Renal Plasma Flow
The filtration fraction
The Filtration
Fraction (FF)
is the ratio of the
GFR to the renal
plasma flow =
(GFR/TRPF).
Reabsorption and Secretion
The amount of a substance filtered into Bowman's
space per unit time is called the
filtered load:
• Filtered load = _____
• Excretion rate = _____
_________
__________
• Reabsorption/secretion rate = FL – Excretion rate
Reabsorption ROUTES
Reabsorption - Transport
Mechanisms
WHAT ARE THE DIFF MECHANISMS ?
– Primary active transport
EXAMPLE ?
• Sodium-potassium pumps in basolateral membrane only
– Secondary active transport
– EXAMPLE ?
• co-transport (glucose, amino acids)
• counter-transport (K+, H+)
– Passive Reabsorption
– EXAMPLE ?
• Osmosis (H2O)
• Electrostatic attraction (Cl-)
Sodium Reabsorption
Glucose Reabsorption
SGLT 2
GLUT 2
Reabsorption Transport Maximum(Tmax)
• DEF:_________________________________________
• WHAT creates a limit to the rate of substances
transport. ?
SATURATION OF TRANSPORT PROTEINS
• Therefore, excess of that substance is ____________
• EXCRETED
Glucose Transport Maximum
Figure 27-4;
Guyton and Hall
RENAL THRESHOLD FOR GLUCOSE
• DEFINITION ?
• The is the plasma level at which the glucose first appears
in the urine .
• The actual renal threshold is about
• 200 mg/dL of arterial plasma,
• which corresponds to a venous level of about 180 mg/dL.
• What causes in splay ?
– TmG in all the tubules is not identical and
– All the glucose were not removed from each tubule
when the amount filtered was below the TmG.
GFR = 120 ml/min,
Plasma glucose of 200 mg/dl (2mg/ml),
transport max (Tm) 200 mg/min
What is the glucose excretion for this
patient?
Passive Reabsorption
• Passive reabsorption depends on:
– Electrical gradient (electrostatic attraction).
– Concentration gradient
– Membrane permeability
– Time available in the tubule for reabsorption
Passive Reabsorption
Secondary water Reabsorption via osmosis
Sodium reabsorption makes both intracellular and
extracellular fluid hypertonic to the tubular fluid.
Water follows with sodium into the peritubular
capillaries.
Na+
Na+
H2O
capillary
Tubular cell
Tubular
lumen
Passive Reabsorption
Secondary ion reabsorption via electrostatic
attraction
Negative ions (Cl-) tend to follow with the positive
sodium ions by electrostatic attraction.
Na
Na+
Cl-
capillary
Tubular cell
Tubular
lumen
Urea–Example of Passive Reabsorption
Na+ reabsorption
H2O reabsorption
Increase
concentration of
urea in tubular fluid
Passive reabsorption
of urea
Mechanisms by which Water, Chloride, and
Urea Reabsorption are Coupled with
Sodium Reabsorption
Figure 27-5;
Guyton and Hall
PAH –EXAMPLE OF SECRETION
•
•
•
•
PAH is an organic acid
Used for measurement of renal plasma flow
Both filtered and secreted
PAH transporters located in peritubular
membrane of proximal tubular cells.
• There are parallel secretory mechanism for
secretion of organic bases like quinine and
morphine
PAH Filtration, Secretion & Excretion
References
• Human physiology by Lauralee Sherwood,
seventh edition
• Text book physiology by Guyton &Hall,11th
edition
• Text book of physiology by Linda .s
contanzo,third edition