Unit 11: Renal System Flashcards
Renal System Components
Kidneys
Ureters
Bladder
Urethra
Kidney Functions (6)
Regulation of
Water balance
electrolyte levels
pH of blood
long term regulation of arterial pressure
removal of non-essential substances from the plasma
recovery of essential substances
Removal of non-essential substances from the plasma
Water metabolites
excess water
electrolytes
Recovery of essential substances
Glucose
Kidneys do not
Produce water or electrolytes but only conserve them by reducing the amount in the body
Elimination of waste by the kidneys include
Drugs
food additives
vitamins that are excreted in the urines
Kidneys also act as an endocrine gland producing hormones or components of hormonal systems
erythropoietin
renin
vitamin D
stenniocalcin
Kidney
Size of a fist
Outer renal cortex
Renal medulla
Inner calyces that drain into the central renal pelvis
renal pelvis drains into the ureter
Nephrons the functional unis the kidneys are located in the renal pyramids
each nephron drains through a collecting duct into a calcyx
Blood flows to the kidneys through the
Renal Artery
Large ____ branches off into several ___ _____ that in turn branch into _____ _____.
Artery
interlobar arteries
accurate arteries
Blood in the ______ ____ flows through the _____ _____ to supply the ______
Arcuate artery
interlobular artery
nephron
Blood supply to the artery drains into the ______ vein the _______ vein, the _____ and then into the _____ vein.
interlobular
arcuate
interlobar
renal
Flow of blood
Renal artery Interlobar artery arcuate artery interlobular artery nephron interlobular vein arcuate vein interlobar vein renal vein
Nephron
The functional unit of the kidney
3 million nephrons in each kidney whose fucntion is to filter the blood
Neprhons reabsorb essential subtances and excrete nonessential molecules and waste
Nephrons are composed of
A highly coiled hollow tube surrounded by a complex blood supply
Renal Corpuscle
A glomerular capsule surrounds a very small highly permeable capillary called the glomerulus
Tubular Portion of the nephron consists of
Proximal convoluted tubule (highly coiled portion of the nephron)
Descending and ascending loop of henle
distal convuluted tubule
collecting duct
Blood from the renal artery reaches the ______ ____ that drains into the ______ _______.
interlobular artery
afferent arteriole
The _____ _____ gives use to the glomerus
afferent arteriole
Blood from the glomerulus enters the
efferent arteriole
Blood then enters the _____ _______
peritubular capillaries
a dense network of capillaries surrounding the tubes of the nephron
Drains into the _______ vein and eventually back to the _______ vein.
interlobular
renal
Renal corpuscle (composition)
Made up of the glomerular capscule and the glomerulus
Site Where the blood is filtered
Glomerular filtration
fluid that is filtered from the blood + water enter the glomerular capsule
Glomerular filtration is facilitated by
A highly permeable capillary endothelium that is surrounded by podocytes
large diameter afferent arteriole and smaller diameter efferent arteriole
Filtration
Movement of fluid through the glomerular capillary due to hydrostatic pressure
Filtrate
The solution created by filtration water+all dissolved soluted in the blood
Reabsorption
Movement of a substance from the lumen of the nephron back into the blood
Secretion
Movement of a substance from the blood into the lumen of the nephron
Excretion
Removal of a substance from the body
Filtration + secretion - reabsorption
Glomerular Filtration
Bulk flow of fluid from the blood back into the glomerular capsule
Filtrate Content
the filtrate contains the same substances as plasma with the excepton of large proteins and RBCs
Glomerular Filtration is Affected by
Extremely permeable capillaries
starling forces
Epithelial cells surrounding the capillaries
Podocytes, large filtration slits formed between pedicles
Starling Forces
Blood hydrostatic pressure
Colloid osmotic pressure due to plasma proteins
Capsular hydrostatic pressure
Net filtration pressure is 10 mmHg out of the glomerulus into the capsular space
Blood Hydrostatic Pressure
60mmHg
Causing filtration of fluid into the glomerular capsule
pressure is due to the difference in arteriole diameters
Colloid Osmotic Pressure
Due to plasma proteins
-32 mmHg
Causing reabsorption of fluid into the plasma
Capsular Hydrostatic Pressure
-18 mmHg causing reabsorption of fluid
Amount of Fluid filtered by the kidneys
180 L/day
Glomerular Filtration Rate
Is the volume of fluid that is filtered by the glomerulus during a certain period of time
Filtered Load
Amount of these substances filtered by the kidneys per day
FL = GFR X Plasma Concentration
Substance that should not be in the urine
Glucose
Urine concentration + amount of solute excreted
Amount of solute that is excreted per unit volume of urine (g/L)
ASE
Actual amount of solute that is excreted in the urine
Amount Excreted
Urine concentration x Amount of water excreted per day
Amount Reabsorbed
FL-ASE
% Excreted
ASE/FL X 100%
Proximal Convoluted Tube to the Collecting Duct
Reabsorption an secretion occurs to different substances in a non-regulated and regulated manner
Transport Mechanisms
Active Transport Secondary Active Transport Facilitated Diffusion Simple diffusion Osmosis
_ _% of the substances filtered in the glomerulus are reabsorbed back into circulation
99
When molecules are reabsorbed back into circulation their are two routes that can be taken
Intracellular
Paracellular
Tubular cells are joined by _____ ______.
Tight junctions prevent substances from crossing between cells.
along the nephron the tight junction vary and can be leaky
Transcellular Transport
From the lumen of the nephron to the tubule cell, to the interstitial space and to the interior of the blood vessel
Na+/K+ Pump
Active transport ATP
3 Na+ out for 2 K+ in
Helps establish the Na+ concentration gradient necessary for secondary active transport
Secretion
The process by which the kidneys remove unwanted substances from the blood into the lumen of the ER
Secretion is generally a _____ ______ but in comse cases can occure without ______ ______.
Hormonally regulated
Hormonal Control
Most substacnes that are secreted are eventually _____ in the ____.
excreted
urine
_ and _ are secreted substances
H+ and K+
Secretion does of K+
Does not rely on the presence of Na+/K+ pump
H+ transportation
H+/K+ exchanger
Na+ Reabsorption takes place in the
Proximal tubule
ascending limb of the loop of Henle
Early distal tubule
Na+ Reabsorption control
Regulated and unregulated Mechanisms
Na+ Hormones Regulating Reabsorption
Angiontensin II
Aldosterone
In healthy individuals
All filtered glucose should be reabsorbed at the proximal tubule
AAs should be reabsorbed in the proximal tubule.
H2O Reabsorption takes place in the
Proximal Tubule
Descending loop of Henle
H2O regulated mechanisms
ADH/Vasopressin acts in the late distal tubule + collecting duct
K+ Reabsorption takes place in the
Proximal tubule
Ascending Loop of Henle
K+ Secretion takes place in the
Ascending Loop of Henle
Late distal tubule
Collecting duct
K+ Hormonally regulated mechanisms
Aldosterone
H+ Secretion occurs in the
Proximal tubule
Ascending loop of henle
late distal tubule
collecting duct
Proximal Convoluted Tube
Reabsorbs 66% of the total filtrate
How is Na+ reabsorbed in the proximal tubule
Via simple diffusion due to the activity of the Na+/K+ cells setting a gradient, Na+ moves into the tubular cells
How are glucose and AA reabsorbed in the proximal tubule
Na+ cotransporters
Reabsorption of Water in the Proximal Tubule
After the reabsorption of AAs the filtrate has a lower solute concentration and a high water concentration compared to tubular cells and the interstial fluid. Water can move by osmosis via aquaporins down its concentration gradient.
Paracellular and transcellular transport
K+ and Cl- reabsorption in the proximal tubule
65% of all filtered K+ and Cl- are reabsorbed in the proximal tubule
Reabsorbed through unregulated paracellular (solvent drag +simple diffusion) + transcellular transport
Transcellular transport of K+
As water exits via osmosis it leaves behind a K+ concentration gradient. K+ can diffuse out of the lumen via simple diffusion
Reabsorption of filtrate back into the circulatory system
Reabsorbed substances leave the cells and enter the interstitial space
How Na+/Glucose/AA/K+ transported into interstitial spce
Na+ leaves via the Na+/K+ pump
Glucose and AA are transported across the basal membrane of the cells by specific facilitated diffusion carriers
K+ via solvent drag and diffusion
_______ ________ cause these fluids to be reabsorbed back into the bloodstream
Starling Forces
Reabsorption of Filtrate (starling forces)
Hydrostatic Force is 13mmHg
Insterstitial hydrostatic force is 6mmHg
Osmotic force ue to plasma proteins 32mmHg
Interstitial osmotic force 15mmHg
-10mmHg back into the capillaries
After reabsorption of solutes the concentration of the filtrate leaving the proximal tubule
Will not change significantly from what it was at the beginning of the tubules
240mmHg-300mmHg
The Loop of Henle
The descending section that extends deep into the medulla of the kidneys and the anscending section that loops back into the cortex.
15% of water and 20% of filtered sodium is reabsorbed in this region
Medulla interstitial concentration
Dramatic change
Medulla-cortex junction: 300 mosm/Kg
Medulla: 1200 mosm/Kg
Descending loop of Henle
Very permeable to water/not permeable to ions
Water moves out of the nephron into the interstitial space via osmosis due to the large concentration gradient in the interstitium.
loss of water results in filtrate concentration increasing dramatically to 1200 mOsm/Kg of water by the time it reaches the ascending limb
Ascending Loop of Henle
Not permeable to water only ions are reabsorbed
Permeable to Na+, K+ and Cl-
transport of all three ions out of the filtrate depends ont he presence of Na+/K+ pumps in the tubule cells
Na+ concentration gradient drives the Na+/K+/Cl- cotransporter
K+ in the ALH
Due to the Na+/K+ pump and the - Na+/K+/Cl- co-transporter K+ concentration inside the tubule cells will increase dramatically
- some K+ will be secreted back out into the filtrate by simple diffusion through leaky channels
Percentage of Na+, Cl-, K+ reabsorbed in the ALH + Filtrate concentration
25%
Decreases form 1200 to 100 mOsm/Kg of water
Distal Convoluted Tubule
Short section of the nephron between the loop of Henle and the collecting duct
12% of Na+ is reabsorbed here
Reabsorption of water in this section of the nephron is controlled by ADH and will depend on the level of hydration of the individual
Amount of water reabsorbed varies form 0-15%
Early Section
Na+ ions diffuse into the tubule cells due to the concentration gradient established by the Na+/K+ pump
Late Section
Closer to the collecting duct
Na+ reabsorption is regulated by aldosterone
Aldosterone (Na+)
Increase the activity of the Na+/K+ pump
decreasing the ceontration of Na+ in the cell
Aldosterone will cause the cell to manfacture more Na+ channels on the luminal cell of the membrane
More Na+ will then be transported out by the increased activity of the Na+/K+ pump
Aldosterone (K+)
K+ is secreted into the lumen of the nephron in response to aldosterone
due to the increased activity of the Na+/K+ pump
Number of K+ transporters are increased in the luminal membrane
Collecting Duct
Collects filtrate form many nephrons and is the final area for processing the filtrate into urine
plays a role in determineing the final concentration of urine
only 10% of all filtered Na+ and water are reabsorbed in this region always under hormonal control
Na+ reabsorption by _____ and water reabsorption by _ _ _
Aldosterone
ADH
Increase of either hormone increases reabsorption
Secretion of K+ in the collecting duct
Takes place in the collecting duct due to the presence of aldosterone
Aldosterone increases the activity of the Na+/K+ pump on the basal side of the collecting duct increasing the concentration of K+ in the tubular cells
Aldosterone causes the cell to manufacture more K+ transporters on the lumen side cuasing K+ to secrete into the lumen
Water is lost through
Lungs, urine, sweating, feces
0.3 L/Day
Regulation of Water balance
Kidneys do not produce water they regulated the amount of water in the body
Water balance in the kidneys is regulated by ADH
ADH
Produced in the hypothlamus and released from the pituitary posterior
negativ feedback control
Osmoreceptors
Sensors that detect water
located in the hypothalamus of the brain
respond to changes in the body fluid concentration
Antidiuretic hormone pathway
Dehydration concentrates the body fluid
Osmoreceptors lose water by osmosis and shrink
shrinking osmoreceptors will signal the posterior pituitary gland to release ADH
ADH will then cause the kidneys to reabsorb more water form the distal tubule and collecting duct
Overhydration
Dilured the body fluid decreasing their osmolarity and causes osmoreceptors to swell
less ADH will be released, less water will be reabsorbed in the distal tubule + collecting
more water is excreted
Dehydration/Overhydration (blood pressure/volume)
Low blood volume and lower blood pressure
Increases blood volume + blood pressure
Blood volume change
Detected by volume receptor in the wall of the left atrium
The blood pressure change is detected by
Baroceptors
Volume receptors
Can control the release of ADH
- ADH causes reabsorption by the distal convoluted tubule + collecting duct directly acting on cells of these regions
- ADH stimulated these cells to manufacture more aquaporins in the luminal membrane
- More water is reabsorbed by osmosis due to the concentration gradient across the luminal cells (lower solute on the outside higher solute on the inside)
- less water is excreted in the urine
- reabsorbed water enters the peritubular capillaries due to starling forces
Na+ Role
Main extracellular ion
determinant of the extracellular fluid volume
plays a role in water balance
water levels affect blood pressure
Na+ levels are regulated by the
RAAS
Renin angiotensin aldosterone system
Aldosterone
Steroid hormone produced by the adrenal glands
secreted into circulation when blood Na+ levels are low or when blood K+ levels are high
Helps return the concentration of ions to normal
Secreted in response to angiotensin ii and in very small amounts by the adrenal corticotropic hormones
- Aldosterone will return Na+/K+ concentration to normal by causing reabsorption of Na+ and the secretion of K+ in the late distal convoluted tubule and the collecting duct
- Aldosterone secretes into the cell and causes the formation of more Na+/K+ channels which are inserted in the luminal membrane
- More Na+ will enter the cells while K+ leaves down their concentration gradients
- Aldosterone increases the activity of the Na+/K+ pumps
RAS
Renin angiotensin system
involves a series of chemical reactions that convert inactive protein to angiotensin II
Angiotensinogen
- produced by the liver
- reacts renin produced by the juxtaglomerular cells located in the walls of the afferent + efferent arterioles
Renin
- released when blood pressure/plasma Na+ levels are low
- converts Angiotensinogen to Angiotensin I
- converted into the active hormone angiotensin II by angiotensin-converting enzyme produced in the lungs
Angiotensin II
increases the reabsorption of Na+ in the proximal convoluted tubule + ascending limb of the loop of Henle
AngII acts directly on the cells of the nephron regions to increase the activity of the Na+/H+ exchanger
AngII stimulates secretion of aldosterone from the adrenal gland which will act on the cells of the distal tubule + collecting duct
Low Na+; low bp
Angiotensin II
- Vasoconstrictor
- increased TPR
- increased bp
- stimulates thirst
