Renal Phys 1 Flashcards
The kidney filters
The entire body blood supply - blood flow 20% of CO
Kidney contributes less than ___ % of total body weight
Less than 0.5% of total body weight
Kidney functions
1 Excretion of metabolic waste products and foreign substances
2 Regulation of body fluids and electrolytes balance, acid base balance and arterial blood pressure
3 Elaboration of endocrine hormones
4 Synthesis of glucose
System approach to kidney functions - How the kidney communicates with the rest of the body - Kidney to extrarenal environment (body)
Excretion of - metabolic waste products, foreign substances
Adjustment of - fluid volume, solute concentration
Elaboration of endocrine hormones
Gluconeogenesis
System approach to kidney functions - Extrarenal environment (body) to Kidney
Blood pressure and volume
Plasma composition
Neuroendocrine
Body sends signals to kidney when changes in these occur
System approach to kidney functions - Intrarenal process
Basic kidney process
Local control of - renal auto regulation and autocrine/paracrine systems
Kidneys are located
just below the rib cage, one on each side of the spine
Urine flows from the kidneys to the ___ through two thin tubes of muscle called ___, one on each side of the bladder
Urine flows from kidney to bladder
Through ureters
When bladder fills with urine - the bladder walls are
relaxed
When the bladder empties, urine flows out through the
urethra
In a bisected kidney, the two major regions visualized are the
Cortex (outer region)
Medulla (inner region)
The medulla of the kidney is divided into
Multiple cone shaped masses of tissue called renal pyramids
The base of each renal pyramid terminates in the ____ which projects into the ____
Base of pyramid terminates in papilla which projects into space of renal pelvis
Functional unit of the kidney
Nephron
Each kidney in the human has how many nephrons
About 1 million
Each nephron of the kidney has was
A filtering component called the glomerulus
A transporting component called the tubule
The glomerulus consists of
A network of capillaries (glomerular capillary) that is supplied by the afferent arteriole and drained by the efferent arteriole
Glomerulus is encased in
Bowman’s capsule
Permeability of the glomerular capullaries is what compared to skeletal muscle
About 50 times that of capillaries in skeletal muscle
The glomerular capillary membrane is similar to other capillaries except
It has 3 (instead of 2) major layers:
Endothelium of capillary
A basement membrane
A layer of epithelial cells (podocytes)
The glomerular capillary membrane is similar to other capillaries except it has 3 major layers - these layers make up the
Filtration barrier - through which large amounts of fluid are filtered from the blood with high filtration rate
Fluid filtered from the glomerular capillaries flows into the ____ and then into the ____
Glomerular capillaries - Bowmans capsule - renal tubule
Where is filtered fluid converted into urine
Renal tubule
Renal tubule is dividded into
Proximal tubule
Loop of Henle
Distal tubule
Collecting duct
The renal artery enters the kidney and then
Branches progressively
The venous system runs ___ to the arteriolar vessels
parallel
The _____ supplying the juxtamedullary nephron differ from those supplying the cortical nephrons
Vascular structures differ
Cortical nephrons =
Nephrons that have glomeruli located in the outer cortex and short loop of henle
Juxtamedullary nephrons =
Nephrons that have glomeruli located deep in the cortex and long loop of henle (20-30%)
Microcirculation of nephron - cortical nephrons are surrounded by
Extensive network of the peritubular capillaries
Enter = afferent
Leave = efferent
Microcirculation of nephron - cortical nephron - Renal circulation is unique because it has
Two capillary beds - the glomerular and peritubular capillaries
Microcirculation of nephron - cortical nephron - The glomerular and peritubular capillaries are arranged in series and separated by the
efferent arteriole
Microcirculation of nephron - Juxtamedullary nerphrons are surrounded by
Specialized peritubular capillaries called vasa recta
Microcirculation of nephron - Juxtamedullary nerphron - The vasa recta extend to
Downward to the medulla - lying side by side with the loop of henle
Microcirculation of nephron - Juxtamedullary nerphron - the specialized network of capillaries in the medulla plays an essential role in the formation of
Concentrated urine
Basic steps in urine formation - Urine composition depends on
The rates at which different substances are excreted from the body
Basic steps in urine formation -Urinary excretion is determined by
3 processes
1) Glomerular filtration
2) Tubular re-absorption
3) Tubular secretion
Urine excretion - Filtration
Glomerular filtration
Movement of substances from the glomerular capillaries into Bowmans capsule
Urine excretion - re absorption
Tubular re-absoprtion
Movement of substances from the tubular lumen to the peritubular capillary (to the blood)
Urine excretion - secretion
Tubular secretion
Movement of substances from the peritubular capillary (from the blood) to the tubular lumen
Urine excretion =
Filtration - re absorption + Secretion
Renal blood flow =
The volume of blood delivered to the kidneys per unit time
Resting, it is about 20-25% of Cardiac output
Blood flow through kidney serves several functions =
1 Delivers substrate for excretion in urine
2 Deliver O2, nutrients, and hormones to cell of nephron and return CO2 and re absorbed fluid and solutes to the circulation
3 Influence GFR
4 Modify rate of solute re absorption
5 Participate in concentration and dilution of urine
Glomerular filtration -
The filtration of plasma from the glomerular capillaries into the bowmans capsule
Urine formation begins with glomerular filtration
Filtrate is termed
Glomerular filtrate or ultrafiltrate
Glomerular filtrate contains ____
Exception to this
all plasma constituents except plasma proteins (albumin) and cellular elements (RBCs)
Exception to this = substances (like Ca and fatty acids) that are bound to plasma proteins
Renal blood flow vs. Renal plasma flow
RBF = the volume of blood delivered to the kidneys per unit of time
RPF = volume of blood plasma delivered to the kidneys per unit time
GFR =
The volume of fluid filtered from the glomerular capillaries into the Bowman’s capsule per unit of time
GFR is determined by the
1 Glomerular capillary filtration coefficient
2 Net filtration force (pressure)
Is GFR a fixed rate?
No - but it is subject to physiological regulation - which causes a change in the net filtration forces due to neural and hormonal input to the afferent and efferent arterioles
Net filtration force (pressure) =
the movement of fluid across a capillary wall is determined by the net filtration force (pressure) that is equal to the sum of the starling forces
- Hydrostatic force (pressure)
- Colloid osmotic force (pressure)
Note - these are the starling forces that control fluid movements across the capillary beds
Hydrostatic Force (pressure) =
In the capillary, it is the force that is exerted by a fluid against the wall of capillary
Colloid Osmotic pressure (oncotic pressure) =
In the capillaries, it is the pressure exerted by proteins in the plasma
Summary of forces causing fltration by the glomerulus capillaries - Favoring filtration
Glomeular hydrostatic pressure
Summary of forces causing fltration by the glomerulus capillaries - Opposing filtration
Glomerular colloid osmotic pressure
Bowmans capsule pressure
Summary of forces causing fltration by the glomerulus capillaries - Net filtration pressure =
Glomeruluar hydrostatic pressure (-) Bowmans capsule pressure (-) glomerular oncotic pressure
Effect of changes in resistance on GFR - VC of afferent arteriole
DECREASED GFR
Effect of changes in resistance on GFR - VC of efferent arteriole
INCREASED GFR
Effect of changes in resistance on GFR -VD of efferent arteriole
DECREASED GFR
Effect of changes in resistance on GFR - VD of afferent arteriole
INCREASED GFR
How long does it take to filter the entire plasma volume - A standard person has about 3.5 L of plasma and GFR is 125 ml/min
3500 ml of plasma/125 ml/min filtered = 28 minutes
How many times a day would a standard person filter 100% of the plasma (if it takes 28 minutes to filter the entire plasma volume)
24 x 60 minutes / 28 minutes = 51 times
Sodium re absorption along the nephron
Filtered = 100% freely
Re absorbed = 98-99%
Excreted = 1-2%
Urine = 1-2%
Amino acid re absorption along the nephrone - how much is exccreted in urine
0%
Glucose re absorption along the nephron - how much excreted in urine
0%
Tubular secretion - what is secreted
Organixc anions and cations Para amino hippurate Urea Potassium Proton
Urea, K, Proton = are re absorbed and secreted before to be excreted
Organic cations and anions - endogenous and drug - Renal secretion of a substance refers to
Direction of flow, from the peritubular capillary (blood) into the lumen fo the nephron
Organic cations and anions - endogenous and drug - Many of the organic compounds are
End product of the metabolism that circulates in the plasma or drugs
Also - many are bound to plasma proteins and are not freely filtered
Organic cations and anions - endogenous and drug - Excretion by filtration alone eliminates only a small portion of these potentially toxic substances from the body - Secretory mechanisms are
powerful and remove all the organic compounds entering the kidney from the plasma
The transport mechanisms have low specificity - several organic compounds compete for the transport pathway
Organic cations and anions secretion along the nephron
Filtered = not freely
Secreted - 100% from proxmila tubule
Excreted = 100%
Potassium re absorption and secretion along the nephron
Filtered = freely
Re absorbed = 99%
Secreted = 1%
Excreted = 15%
Tubular reabsorption is highly
Selective!
Kidney regulates the rate of tubular re absorption of solutes independently of one another
This capacity of the kidney is essential for precise control of composition and volume of urine
Selectivity of tubular re absorption is due to the characteristics of the renal tubule cells
Re absorption of filtered fluid and solutes form the tubular lumen into the blood
Mvmnt from lumen of nephron into cell
Mvmnt from cell into itnerstitial fluid
Mvmnt from interstitium to the capillary
Transcellular pathway - primary and secondary active transport
1 - Metabolic substrates (like glucose, amino acids and fatty acids)
2 - All of these various fuels are converted in energy ATP
3 - Electrochemical gradients such as low cell Na and negative voltage drive a whole array of transport processes
Net re-absorptive forces - Hydrostatic and colloid osmotic forces
Favoring re absoprtion =
Colloid osmotic pressure in peritubular capillary
Hydrostatic pressure in the renal interstitium
Net re-absorptive forces - Hydrostatic and colloid osmotic forces - Opposing re absorption
Hydrostatic pressure in peritubular capillary
Colloid osmotic pressure in renal interstitium
Pathogenesis of edema in nephrotic syndrome - due to
A disturbance in the forces that normally partition fluid into the various sub compartments of extracellular fluid space
The blood volume remains contracted even though extracellular fluid volume is expanded
Glomerular injury - proteinuria - reduced colloid osmotic pressure - edema - reduced plasma volume
Original problem is at level of glomerulus
