Renal Flashcards
Functional unit of the kidney and is responsible for maintenance of body fluid homeostasis
Nephron
-within the Bowman’s capsule
-site of filtration
Glomerular capillary bed
-surrounds the nephron tube
-returns reabsorbed substances to systemic circulation
-secretes substances into interstitial space
Peritubular capillary bed
-Hollow structure lined with epithelial cells (tight junctions between cells)
-Site of reabsorption & secretion
Nephron tubule component
Four basic Renal processes:
F
R
S
E
Filtration
Reabsorption
Secretion
Excretion
The _______ consists of most substances dissolved in plasma
Does not include ________ & ______ _____
filtrate
Proteins (some small peptide hormones are)
Blood Cells
-1st step in the process that ultimately leads to the formation of urine by the kidneys
-Involves movement of water and solutes from the plasma into the Bowman’s Space
Filtration
Selectivity of glomerular filtration barrier is crucial for renal function based on:
Molecular Size
-radius
-shape
Electrical Charge
________ ___________ is the process that moves a substance out the tubular lumen across the epithelial layer
Tubular Reabsorption
-Movement across/through (trans) the apical membrane into the epithelial cells
-Can remain inside the epithelial cell or move out across the basolateral membrane to enter the interstitial fluid Paracellular Movement
Transcellular
Movement between/beside (para) cells through the tight junctions into interstitial fluid
Paracellular movement
Total body water constitutes __% of total body weight
-Intracellular Fluid makes up __% (40% total BW)
-Extracellular make up __% (20% total BW)
60%
60%
40%
Extracellular Fluid is divided into three types of fluid:
-_______: Fluid between cells 75%
-______: fluid portion blood 20%
- _______: Specialized Fluid
Interstitial
Plasma
Transcellular
7 FXNS of the kidney
(REGULATE x 5, EXCRETE, MAINTAIN)
-Regulate water/electrolyte
-Regulate systemic BP & Extracellular fluid volume
-Regulate acid-base balance
-Regulate red blood cell production
-Regulate Vit D production, calcium and phosphate balance
-Excrete metabolic waste & foreign substances
-Maintain blood glucose (gluconeogenesis)
Entrance and exit for the kidney is called what?
Hilus
LAYERS:
Outer= _________
Inner= __________
Cortex
Medulla
This region/layer of the kidney:
-lacks glomeruli
-Small vessels (Vasa Recta)
-Parallel arrangement of tubules (reabsorb/secrete)
Medulla
This region/Layer of the kidney:
-Glomeruli
-Tubules (reabsorb/secrete)
-Blood vessels (90% of blood entering)
Cortex
________ act as collecting cups for urine formed by renal tissue in the pyramids
Calyces
Functional unit of the kidney
Nephron
_________ Capillary bed:
-W/in bowman’s capsule
-site of filtration
Glomerular
________ capillary bed:
-Surrounds nephron tubule
-Returns reabsorbed substances to systemic circulation
-Secretes substances into interstitial fluid
Peritubular capillary bed
Movement of water and solutes from the plasma into bowman’s space known as ______ ________
This does not include
-________
-________
-glomerulus filtration
Proteins
Blood Cells
Glomerular filtration barrier is crucial for renal function and is based on what two components:
- Molecular size (weight)
- Electrical Charge (More positive and neutral charged)
-The side of a renal tubular epithelial cell that faces the tubular lumen
-In contact with the filtrate
Apical Membrane
The side of a renal tubular epithelial cell that faces the interstitial fluid and the peritubular capillaries
Basolateral Membrane
The process that moves a substance out the tubular lumen across the epithelial layer
Reabsorption
Reabsorption is a two step-process:
-The movement (passive or active) of water and solutes from the filtrate inside the tubule through the ______ _________ into the renal epithelial cells
-Movement (passive or active) of water and solutes from inside the renal epithelial cells though the _________ _________ into the interstitial fluid and then through the peritubular capillary walls back into the bloodstream
-apical membrane
-basolateral membrane
Movement across/through the apical membrane into the epithelial cells Can remain inside the epithelial cell or move out across the basolateral membrane to enter the interstitial fluid
Transcellular Movement
Movement between/beside (para) cells through the tight junctions into interstitial fluid
Paracellular movement
Process of a substance that enters the tubular lumen via Transcellular and Paracellular Movement
Secretion
Refers to expelling waste products from the body via biological functions
Examples:
Urine
Feces
Excretion
-Rate at which systemic blood is delivered to the kidney
-Typically, ~20 – 25% of normal cardiac output (~1,000 ml/min)
-The entire blood volume is delivered to the kidneys approximately every 5 minutes
Renal Blood Flow
-The portion of RBF that is only plasma
-This is the portion of the blood that is filtered across the glomerular filtration barrier
Renal Plasma Flow
-Fraction of the renal plasma flow that actually moves across the glomerular filtration barrier →
becomes the ultrafiltrate
-~20% under normal circumstances
Filtration Fraction
-Autoregulation of renal blood flow
-Regulation of Afferent and Efferent Arteriolar -Diameter
-Tubuloglomerular Feedback
Intrinsic Mechanisms
Act to “fine-tune” or modify intrinsic mechanisms:
Paracrine
Endocrine
Neural
Extrinsic mechanisms
What influences glomerular filtration rate?
Renal Blood Flow
-Automatic adjustment of blood flow at any given instant
-The intrinsic property of an organ to maintain a constant blood flow despite changes in perfusion pressure
Autoregulation
Renal blood flow is autoregulated through a localized reflexive process called the
myogenic response
↑ renal artery blood pressure stretches afferent arterioles → activates inward-directed Ca2+ channels → depolarization → arteriole contraction these cause this response
Myogenic response
-The primary regulation of glomerular filtration occurs within the ________ itself by constricting and dilating the afferent and efferent arterioles
-This affects the ________ _______ (PH or Pgc) within the glomerular capillaries
hydrostatic pressure
Volume of fluid filtered through all corpuscles of both kidneys per day
-Influenced by renal blood flow:
-Hydrostatic (net) pressure
-Oncotic pressure
Glomerular Filtration Rate (GFR)
Ultrafiltrate leaving Bowman’s Space is called
Tubular flow
↑ renal output of water Known as ______ _______
pressure diuresis
↑ the output of Na+ Known as ________ ________
pressure natriuresis
-↑ systemic/renal artery blood pressure → afferent arteriole __________ (myogenic autoregulation):
-Does what to these parameters: Inflow → RBF → PGC → GFR → tubular flow
vasoconstriction
- Decreases all of them
Afferent arteriole vasodilation (neural/hormonal):
Doe what to these parameters: Inflow → RBF → PGC → GFR → tubular flow
Increases all of them
Efferent Arteriole outflow changes:
___________-↓ outflow → ↑ PGC → ↑ GFR* → ↑ tubular flow but ↓ RBF
_________-↑ outflow → ↓ PGC→ ↓ GFR → ↓ tubular flow but ↑ RBF
Vasoconstriction
Vasodilation
What does RAAS stand for?
Renin–angiotensin–aldosterone system
↓ BP → ↓ afferent arteriole stretch → triggers release of renin from the ________ (juxtaglomerular)
cells within the afferent arterioles
Granular
↑ Renin → ↑ angiotensin I → _ angiotensin II:
-Vasoconstriction of both the afferent and efferent arterioles but with more constriction of the________→ ↑ PGC →↑ GFR but ↓ in RBF
-Stimulates _________→ ↑ Na+ and water reabsorption → ↑ in systemic BP and RBF
↑
efferent
aldosterone
_______ ________ _____
Sense the relative flow of NaCl in the distal tubule, which correlates directly with GFR
↑ NaCl flow (i.e., hi [NaCl]) = ↑ GFR
↓ NaCl flow (i.e., low [NaCl]) = ↓ GFR
Macula Densa cells
High [NaCl] in filtrate (high GFR)
Secrete _______(ADO), which:
-↓ renin secretion from granular cells
-Constricts afferent arterioles (↓ P→ ↓ GFR)
-Dilates efferent arterioles (↓ PGC → ↓ GFR)
Low [NaCl] in filtrate (low GFR)
Stimulate granular cells to secrete ________
↑ renin → ↑ angiotensin II → selectively
constricts efferent arterioles → ↑ PGC → ↑ GFR
Stabilizes (autoregulates) RBF and GFR
adenosine
Renin
________ sympathetic renal nerves are distributed to all segments of the intrarenal vasculature in the renal cortex and outer medulla
Interlobar, arcuate, and interlobular arteries (limited)
Afferent and efferent glomerular arterioles
Highest innervation is to the _________ glomerular arterioles followed by the _________ glomerular arterioles
↑ sympathetic activation → _ norepinephrine release → vaso_______ (α1 receptors)
-efferent
-afferent
-efferent
-↑
-vasoconstriction
Innervation of all parts of the nephron ↑ sympathetic activation → _ renin release ( __receptors)
↑ (β1)
Endocrine Factors/Mediators
Vasoconstrictors:
A
A
E
E
N
T
V
-Adenosine (can also be paracrine)
-Angiotensin II (renin-angiotensin-aldosterone system / RAAS)
-Endothelin
-Epinephrine
-Norepinephrine (circulating)
-Thromboxane A2
-Vasopressin (ADH)
Endocrine Factors/Mediators:
Vasodilators:
A
D
H
N
P
Atrial natriuretic peptide
Dopamine
Histamine
Nitric oxide
Prostaglandins E2 and I2
the process of converting the systemic blood supply into a filtrate, which will ultimately become the urine
Glomerular Filtration
-Found between afferent arteriole and the distal convoluted tubule of the same nephron
-This location is critical to its function in regulating renal blood flow and glomerular filtration rate (GFR)
Juxtaglomerular Apparatus
Located in the tunica media of the afferent arterioles as they enter the glomeruli
Functions:
–Detect changes in renal perfusion pressure (baroreceptor function)
-Secrete renin in response to:
β1 stimulation
↓ in renal perfusion pressure
↓ [NaCl] at the macula densa
Granular cells
A modified region of the distal convoluted tubule epithelium
Respond to changes in the [NaCl] in the distal tubule
Macula Densa
Blood enters the glomerulus via the _______ arteriole
Plasma moves from __________ capillaries through the glomerular filtration barrier
~__% of renal plasma flow is filtered (filtration fraction)
The resulting filtrate (ultrafiltrate) collects in Bowman’s space and exits through into the ________
convoluted tubule lumen
The remaining blood within the glomerular capillaries exits through the efferent arteriole → ________ capillaries → systemic venous circulation
-afferent
-glomerular
-20%
-proximal
-peritubular
Glomerular Filtration Barrier Consists of what 4 layers?
Glycocalyx
Capillary Endothelial Cells
Glomerular basement membrane
Epithelial podocytes
-Between the capillary endothelial cells and the podocytes
-Negatively charged → favors filtration of cations
Glomerular basement membrane
-Contain large fenestrations (windows) that allow free movement of water and small solutes
-Almost completely covered by glomerular basement membrane and podocytes
Capillary endothelial cells
-Surround the capillaries and rest on the basement membrane
-Contain slit diaphragm that assists in the filtration process
Epithelial podocytes
Paracrine Mechanisms:
Arteriole vasoconstrictors (↓ RBF):
A
L
E
Arteriole vasodilators (↑ RBF):
N
P
Adenosine
Leukotrienes
Endothelins
-Nitric oxide (NO)
-Prostaglandins
-These receptors are located Located in the interlobular arteries and afferent arterioles
-These receptors are Located in the renal pelvis
Respond to extracellular [K+] and [H+]
-Baroreceptors
-Chemoreceptors
Formation of urine involves 3 processes:
Filtration (Ultra)
Reabsorption
Secretion
Explain:
Every
Waterfall
Raises Sodium
In exchange for Potassium
for another Waterfall
-Almost EVERYthing filtreed can be reabsorbed
-Descending loop of henle= water reabsorption
-Ascending Loop- reabsorption of Na+
-Distal Tubule: Na+ reabsorption with K+ secretion
-Colleting Duct: downward structure reabsorbs water
Primary Renal process of:
The _______ _______ reabsorbs ~67% of all filtered:
Water
Na+
Cl-
K+
Other solutes
Reabsorbs nearly 100% of filtered:
Glucose
Amino acids
HCO3-
Secondary Renal Process=
Proximal Tubule
Secretion
Epithelial transport requires that cells be __________
Has 5 steps
1. ______extrusion of Na+ from epithelial cell into interstitium across basolateral membrane
2. ______ entrance of Na+ from tubular lumen across the apical membrane into the cell (down gradient)
3. ______ movement of anions (Cl- & HCO3-) → electroneutrality
4. _______ flow of H2O from tubular lumen → interstitium
-Via aquaporin channels (transcellular movement)
-Paracellular movement
5. ______ ____ of Na+ & H2O into peritubular capillaries
-Driven by Starling forces
Polarized
- Active
- Passive
- Parallel
- Osmotic
- Bulk flow
Proximal Tubule: Na+ Reabsorption
1st half: Na+ reabsorbed primarily with ______
-Majority of Na+ reabsorbed here, along with glucose and amino acids
2nd half: Na+ reabsorbed primarily with ___
HCO3
Cl-
Proximal Tubule highly permeable to H2O due to __________ channels
aquaporin 1 (AQP1)
Proximal Tubule: Water reabsorption
aquaporin 1 (AQP1)
-Highly expressed in the kidney
Controls water ________ in both apical and basolateral membranes
-Constitutive (continuous) absorption of >__% of water in the glomerular filtrate
Not regulated by _______ _______ (unlike AQP2 in the collecting tubules and ducts)
-reabsorption
-70%
-arginine vasopressin
Thin descending limb
Primary renal process: _________ __ _____
Impermeable to ___
-Reabsorption of water
-Na+
Loop of Henle (thin & thick ascending limbs)
Primary Renal Process: Reabsorption of _______
Reabsorbs ~__% of filtered NaCl
Starts with Na+/K+-ATPase in _______ membrane
Impermeable to ______ (lacks aquaporin proteins)
Since solutes are reabsorbed but not H2O → fluid produced is dilute relative to plasma → diluting segment
-Solutes
-25%
-basolateral
-water
Distal Tubule (In Exchange for Potassium)
Primary Renal Process: Reabsorption of ____
Mostly Impermeable to ___
-Causes urine to become more _______
Na+ reabsorption in exchange for K+ ________
-NaCl
- H20
-diluted
-secretion
Primary Renal Process: Reabsorption of _____
Absorption of ~__% of water in the glomerular filtrate
Large number of aquaporin proteins
Apical membrane
-AQP2 Regulated by ________ (ADH) via V2 receptor
Basolateral membrane
AQP3
AQP4
-water
-15%
-vasopressin
______ ____________ ________ most important mechanism to counteract temporary / short-term changes in arterial pressure
Arterial baroreceptor reflex
4 distinct pathways to regulate Na+:
- Renal baroreceptors
- sympathetic nervous system input
- Posterior Pituitary release of Vasopressin
- Release of atrial natriuretic peptide
An ↑ in arterial pressure (i.e., hydrostatic pressure) of only a few mmHg alters GFR and can:
-Significantly ↑ renal output of water Known as pressure ______
-Significantly ↑ the output of Na+ Known as pressure ________ ……..Which → ↑ water loss
diuresis
natriuresis
Kidney baroreceptors
Detect changes in renal perfusion pressure (baroreceptor function)
Secrete renin in response to:
-__stimulation (sympathetic input)
- _ in renal perfusion pressure
- _ [NaCl] at the macula densa (chemoreceptor function)
- β1
- ↓
- ↓
In Proximal Tubule:
NE binding to (primary) α1-adrenoceptors stimulates ___ ___________
In Collecting Tubules/Duct:
NE binding to α2-adrenoceptors inhibits ___ ____________
-Na+ reabsorption
-Na+ reabsorption
_________ control distal nephron permeability to water and solutes
Hormones
Angiotensin II stimulates
Na+ ________ in nephron (direct action)
*Water follows Na+
*Secretion of ________ (antidiuretic hormone)
reabsorption
vasopressin
________ is the primary regulator of renal Na+ reabsorption and is regulated by angiotensin II
Produced in the ________ ______
Binds MR receptors in the _______ convoluted tubule
Aldosterone
adrenal cortex
Atrial Natriuretic Peptide acts i 2 ways:
1. Stimulates vaso_______ of the ________ arteriole
and induces vaso______ of the _______ arterioles
- Acts on several segments of nephron to ↓ Na+ reabsorption:
-Early ______ ____ (primary site)
-_______ & _________ tubule
Vasodilation - Afferent
Vasoconstriction- Efferent
Collecting duct
Proximal and Distal
pH must be maintained within a narrow range _____ - ______
7.35 – 7.45
Kidneys regulate acid-base balance by:
-Reabsorb (~99.9%) filtered HCO3-
-Secrete & excrete fixed acid (H+)
-Produce and reabsorb HCO3-
This is the most important extracellular (interstitial fluid + plasma) buffer
HCO3
Macula densa cells detect changes in _____ concentration and provide feedback to the ________ arterioles to regulate renal blood flow.
NaCl
Afferent
The ____________ capillaries play a large role in the reabsorption of solutes and water into the cardiovascular system.
Peritubular
Solutes are responsible for the movement of water between cells and the interstitial fluid by ________.
osmotic pressure
As resistance in the efferent arterioles continues to increase above normal, glomerular filtration rate
Decreases due to a reduction of renal plasma flow, even though the hydrostatic pressure in the glomerular capillaries increases as a result of the reduced outflow of blood from the glomerulus.
A decrease in the sodium concentration in the distal convoluted tubular filtrate is indicative of
A decrease in renal blood flow
When systemic blood pressure increases, blood vessels supplying the kidney will ________ to maintain a steady rate of filtration.
contract:
In response to stretch, vascular smooth muscles vasoconstrict due to the opening of stretch-activated Ca2+ channels (the myogenic response).
________ pressure must be greater on the capillary side of the filtration membrane to achieve filtration.
hydrostatic
As glomerular filtrate moves through the ascending loop of Henle, the filtrate becomes more dilute: why?
The ascending loop of Henle is permeable to ions but impermeable to water.
The presence of which of the following in the urine, even in small amounts, is indicative of a possible problem in the renal system of a patient?
Glucose
Renin is released in response to which of the following?
Innervation by sympathetic neurons.
-Act via B1 receptors
Detection of low glomerular filtrate NaCl concentrations by macula densa cells.
Detection of low blood pressure by baroreceptor cells.
Renal blood flow can be influenced/modified by which of the following?
- NaCl concentration in the glomerular filtrate.
via Tubuloglomerular Feedback. - Vascular tone of the afferent arterioles.
- Glomerular filtration rate.
- Vascular tone of the efferent arterioles.
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