Module 11 - Renal System Flashcards
Homeostasis Control
- Blood volume
- Hydration
- Body temp
TBW Distribution
- Intracellular 67%
- Interstitial 26%
- Plasma 7%
Renal System Regulation
- Water balance
- Electrolyte levels
- Blood pH
- Arterial pressure (long-term)
Kidney Functions
- Remove nonessential substances
- Recover essential substances
- Producing hormones/components of hormonal systems
Kidney Anatomy
- Outer renal cortex
- Middle renal medulla
- Inner calyces
- Renal pelvis
- Ureter
- Bladder
- Urethra
Inner Calyces
- Collect waste from collecting ducts (nephron)
- Drain into renal pelvis
Renal Pelvis
- Collects urine
- Drains into ureter
Nephron Anatomy
- Renal corpuscle
- Proximal tubule
- Descending limb of loop of henle
- Ascending limb of loop of henle
- Distal convoluted tubule
- Collecting duct
Nephron Functions
- Filter blood
- Reabsorb essential substances
- Excrete nonessential molecules & waste
Kidney Blood Flow
- Renal artery
- Interlobar arteries
- Arcuate arteries
- Interlobular arteries
- Afferent arteriole
- Glomerulus (FILTRATION)
- Efferent arteriole
- Peritubular capillaries
- Interlobular vein
- Arcuate vein
- Renal vein
Filtrate
- Solution created by filtration
- Composed of water & all dissolved solutes in blood
- No large proteins
Nephron Processes
- Filtration
- Reabsorption
- Secretion
- Excretion
Nephron Filtration
- Movement of fluid through glomerular capillary
- Due to hydrostatic pressures
- Creates filtrate
Nephron Reabsorption
- Movement of substance from nephron (lumen) back into blood
Nephron Secretion
- Movement of substance from blood into nephron (lumen)
Nephron Excretion
- Removal of substance from body
Glomerular Filtration
- Flow of fluid filtered from blood into glomerular capsule (bowman’s capsule)
- Filtered fluid (filtrate) enters capsular space
Glomerular Filtration Factors
- Extremely permeable capillaries (glomerulus)
- Stirling forces
- Many fenestrations
Hydrostatic Pressure of Glomerular Capillary
- Causes filtration
- Fluid moves into glomerular capsule
Colloid Osmotic Pressure of Glomerular Capillary
- Causes reabsorption
- Fluid moves into plasma
Hydrostatic Pressure of Bowman’s Capsule
- Causes Reabsorption
Colloid Osmotic Force of Bowman’s Capsule
- Causes filtration
- Presence of proteins in glomerular space
Glomerular Filtration Rate (GFR)
- Volume of fluid filtered by glomerulus during certain period
Filtered Load
- Amount of substance filtered by kidneys per day
= GFR x plasma concentration of substance
Amount Excreted Equation
= urine concentration x water excreted per day (1.8L)
Amount Reabsorbed Equation
= filtered load – amount excreted
Fraction Excreted Equation
= (amount excreted/filtered load) x 100
Tubular Transport Mechanisms
- Active transport
- Secondary active transport
- Facilitated diffusion
- Simple diffusion
- Osmosis
Proximal Tubule Reabsorbed Substances
- Glucose
- Amino acids
- Na+
- K+
- Cl-
- HCO3-
- H2O
Proximal Tubule Secreted Substances
- H+
Descending Limb Reabsorbed Substances
- H2O
Descending Limb Secreted Substances
- Nothing
Ascending Limb Reabsorbed Substances
- Na+
- K+
- Cl-
Ascending Limb Secreted Substances
- K+
- H+
Distal Tubule Reabsorbed Substances
- Na+
- HCO3-
- H2O
Distal Tubule Secreted Substances
- Na+
- H+
Collecting Duct Reabsorbed Substances
- H2O
Collecting Duct Secreted Substances
- Na+
- H+
Transcellular Transport
- Regulated or non-regulated
- Transport substances across tubular cell membranes
- From lumen, into interstitial fluid, into blood
Paracellular Transport
- Non-regulated
- Leaky (tight) junctions along nephron
- Substances diffuse between tubular cells
Secondary Active Transport
- Uses concentration gradient established by Na+/K+ pump
- Na+/glucose co-transporter
- Na+/H+ exchanger
Secretion
- Kidneys remove unwanted substances from blood into nephron (lumen)
- Generally, hormonally regulated
- Secreted substances are excreted in urine
Reabsorption Mechanisms Proximal Convoluted Tubule (Na+, Glucose, Amino Acids)
- Simple diffusion
- Na+/glucose co-transporter
- Na+/H+ exchanger
- Na+/amino acid co-transporter
Reabsorption Mechanisms Proximal Convoluted Tubule (H2O)
- Reabsorbed after Na+, glucose, amino acids
- Osmotic gradient established with solute reabsorption
- Aquaporins (special water channels)
- Paracellular & transcellular transport
Reabsorption Mechanisms Proximal Convoluted Tubule (K+)
- Absorbs majority of K+
- Paracellular transport
- Unregulated
- Solvent drag
- Simple diffusion
Reabsorption Mechanisms Proximal Convoluted Tubule (Cl-)
- Transcellular transport
Diabetes Mellitus
- Nephron unable to reabsorb all glucose
- Glucose excreted in urine
- Lack of insulin
Concentration of Filtrate
- 290-300mOsm/kg of water
- Volume difference
Descending Limb Permeability
- High to water
- Low to ions
Ascending Limb Permeability
- Low to water
- High to K+, Na+, Cl-
Reabsorption Mechanisms Descending Limb
- Osmosis
Reabsorption Mechanisms Ascending Limb
- Na+/K+ pump creates concentration gradient
- Special co-transporter (Na+, K+, Cl-)
Secretion Mechanisms Ascending Limb
- Simple diffusion (leaky channels)
- Na+/H+ exchanger
Reabsorption Na+ Distal Tubule
- Regulated by aldosterone
- Na+/K+ pump activity increase
- More Na+ channels on luminal membrane side
Reabsorption H2O Distal Convoluted Tubule
- Controlled by antidiuretic hormone (ADH)
- Depends on hydration level
Secretion K+ Distal Convoluted Tubule
- Response to aldosterone
- Increases activity of Na+/K+ pump
- Increases number of K+ channels in luminal membrane
Reabsorption Collecting Duct (Na+)
- Controlled by aldosterone
- Reabsorbs low amount
Reabsorption Collecting Duct (H2O)
- Depends on ADH
- Reabsorbs low amount
Secretion Collecting Duct (K+)
- Controlled by aldosterone
- Increases Na+/K+ pump activity on basal side
- Make more K+ channels on luminal side
Water Balance
- Regulated by ADH
- Relies on negative feedback
Osmoreceptors
- Sensor in negative feedback system of water regulation
- Located in hypothalamus
- Respond to changes in body fluid concentrations
Dehydration
- Osmoreceptors lose water via osmosis & shrink
- Release of ADH
- Kidneys reabsorb water from distal tubule & collecting ducts
Overhydration
- Osmoreceptors swell
- Less ADH released
- Kidneys reabsorb less water from distal tubule & collecting duct
- More water excreted in urine
Dehydration Effects
- Lower blood volume
- Lower BP
Overhydration Effects
- Increase in blood volume
- Increase BP
Volume Receptors
- Located in left atrium
- Detect change in blood volume
- Control release of ADH
ADH Release
- Stimulates aquaporin formation
- Water reabsorbed via osmosis
Sodium Balance
- Regulated by renin-angiotensin system (RAS) & aldosterone
Aldosterone
- Produced by adrenal glands
- Responses to low Na+ or high K+ levels
- Responds to angiotensin II
- Responds to adrenal corticotropic hormone (ACTH)
Aldosterone Effects
- Tubule cells produce more Na+ & K+ channels
- Increases activity of Na+/K+ pump
Renin-Angiotensin System (RAS)
- Regulates Na+ balance
- Increase reabsorption of Na+ in proximal tubule
- Conversion of angiotensinogen to ang II
Angiotensinogen
- Reacts with renin
- Produced in liver
- Convert angiotensinogen to ang I
Ang I
- Converted to ang II
- Angiotensin converting enzyme (ACE) produced in lungs
Ang II
- Increases Na+ reabsorption
- Proximal tubule & ascending loop
- Increase activity of Na+/H+ exchanger
- Stimulates secretion of aldosterone
- Increase BP (potent vasoconstrictor)
- Thirst sensation (increase blood volume)
- Absorption of H2O & Na+ from GI tract
Renin
- Produced by juxtaglomerular cells
- Na+ reabsorption via RAS
