Renal Physiology Flashcards
What are the three functions of the kidneys?
- Regulation of blood volume and composition.
- Regulation of blood pressure.
- Contribution to metabolism.
What is the renal hilus?
Deep vertical fissure near the center of the concave renal border. The ureter emerges from the hilus along with lymphatic vessels, blood vessels, and nerves.
What are the three layers of tissue around the kidney?
- Renal capsule.
- Adipose capsule.
- Renal fascia.
What is the renal capsule?
Deepest layer of the kidney, clear and irregular connective tissue that is continuous with the shiny outer lining of the ureter.
What is the function of the renal capsule?
Serves as a barrier against trauma that also maintains the shape of the kidney.
What is the adipose capsule?
Mass of fatty tissue surrounding the renal capsule.
What is the function of the renal capsule?
Barrier against trauma and holds the kidneys firmly placed in the abdominal cavity.
What is the renal fascia?
The superficial layer of the kidney.
What is the function of the renal fascia?
Defence layer, anchors the kidneys to the surrounding structures and to the peritoneum.
What is the renal cortex?
Smooth-textured, reddish area of the kidney, comprises the outer-rind of the kidney.
What is the renal medulla?
The inner section of the kidney, contains cone-shaped renal pyramids.
What are renal pyramids?
Cone-shaped structures within the renal medulla that point toward the renal hilus for renal emptying/clearance.
What are renal papila?
Segments of pyramidal cones in the renal medulla, narrower/apical end
What are the two zones of the renal cortex?
The cortical zone and the juxtamedullary zone.
What is a renal column?
Portion of the renal cortex that extends between renal pyramids.
What is a renal lobe?
Portion of the kidney consisting of one pyramid and half of adjacent columns.
What is the parenchyma?
Functional portion of the kidney consisting of the renal cortex and the pyramids of the renal medulla.
What are the functional units of the kidney? Where are they located?
The nephrons; are located within the parenchyma.
Where does urine formed by nephrons drain?
Into the papillary duct.
What are the papillary ducts?
Ducts that collect urine formed by nephrons, extend through the renal papillae.
Where do papillary ducts drain?
Into minor calyx.
Where do minor calyces drain?
Into a major calyx.
Where do the major calyces drain?
Into the renal pelvis.
What blood vessel supplies the kidneys?
Right and left renal arteries.
List the branching of renal circulation from IN to OUT:
- Renal artery.
- Segmental arteries.
- Interlobar artieries.
- Arcuate arteries.
- Interlobular arteries.
- Afferent artieries.
- Glomerular capillaries.
- Efferent arterioles.
- Pertitubular capillaries.
- Interlobular veins.
- Arcuate veins.
- Interlobar veins.
- Renal vein.
What is a renal lobule?
Group of nephrons that empty into the same collecting duct.
What is unique about the glomerular capillaries?
They are positioned between two arterioles.
What is the vasa recta?
Loop-shaped capillaries supply the tubular sections of the nephron in the renal medulla.
Where does the blood leave the kidney from?
Renal vein that exits the renal hilus.
What is the renal corpuscle?
Glomerular capsule and the glomerular capillary system.
What is the function of the renal corpuscle?
To filter blood plasma into the nephron.
What is the renal tubule?
Consists of the proximal tubule, descending loop of Henle, ascending loop of Henle, and the distal tubule.
What is the function of the renal tubule?
Conducts filtered fluid through the nephron.
What comprises the visceral layer of the glomerular capsule?
Podocytes with footlike projections that wrap around a single layer of endothelial cells of the glomerular capillaries.
What comprises the parietal layer of the glomerular capsule?
Simple squamous epithelium that forms the outer wall of the capsule.
What are the urethral differences between male and female systems?
Male: passes through prostate, longer.
Female: shorter in length.
Are the majority of nephrons cortical or juxtamedullary?
Majority (80%) is cortical, 20% are juxtamedullary.
What are peritubular capillaries?
Long, specialized capillaries that align alongside the juxtamedullary nephron tubules.
What is the juxtaglomerular complex?
Comprised of the ascending limb of the loop of Henle and glomerulus and afferent/efferent arterioles.
What is the morphology of the tubular epithelium?
Epithelial cells are connected mostly by tight junctions; the apical surface faces the lumen while the basolateral surface faces the renal interstitium by resting on the basement membrane.
What kind of fluid enters the tubules through glomerular filtration?
Protein-free plasma like fluid.
What two processes is the filtrate subject to?
Reabsorption and secretion.
What filtrate contents are reabsorbed?
Water and solutes.
Where is filtrate reabsorbed?
Through vasa recta or peritubular capillaries.
What is secretion?
Selective removal of substances from the circulation into the tubular filtrate.
What is the function of the loop of henle?
Descending limb: facilitates water reabsorption.
Ascending limb: facilitates active solute reabsorption.
What kind of filtrate leaves the loop of henle?
Diluted.
What is the function of the distal & convoluted tubule?
Salt and water regulation, varies in permeability based on body needs (in response to hormones)
How is the amount of solute excreted calculated?
Based on the amount of solute filtered minus the amount reabsorped plus the amount secreted into tubules.
What is the filtration fraction?
Proportion of plasma volume that filters into the tubule.
What are the three filtration barriers in the renal corpuscle?
Glomerular capillary endothelium.
Basal lamina (basement membrane)
Epithelium of bowman’s capsule.
What is the morphology of the glomerular capillary endothelium? How is it a filtration barrier?
Contains fenestrated capillaries with pore sizes that permit most solutes but not plasma proteins.
The surface is negatively charged to repel proteins.
What is the function of the glomerular basement membrane? How is it a filtration barrier?
It is the extracellular matrix of the glomerular membrane, separates glomerular capillary endothelium from Bowman’s epithelium.
Negatively charged to repel proteins.
What is bowman’s capsule epithelium? How is it a filtration barrier?
Layer of podocytes with foot processes that wrap around glomerular capillaries with slits for siltration; contain contracile mesangial cells that contribute to blood flow control.
What two Starling forces dictate glomerular filtration?
- Glomerular capillary hydrostatic pressure favors filtration (high pressure wants to move INTO bowman’s space)
- Proteins remaining in the capillaries oppose filtration (lower than glomerular hydrostatic pressure)
What is GFR?
Volume of fluid entering Bowman’s capsule per unit time.
What is GFR influenced by?
Net filtration pressure (altered by renal blood flow)
Filtration coefficient (total surface area, permeability)
What does increased renal nerve activity cause?
Decreased RBF and GFR.
How do RBF and GFR remain stable in face of fluctuating arterial pressures?
Constant operation of renal autoregulatory mechanisms.
What two mechanisms is renal autoregulation composed of?
Myogenic response
Tubuloglomerular feedback mechanism
What is the function of renal autoregulation?
To keep RBF and GFR between 80-180mmHg,
What is the myogenic response?
When RBF increases, hydrostatic pressure against walls of the afferent arteriole also increase.
Stretch receptors in vascular smooth muscle cells nitiate vasoconstriction
RBF decreases, causing pressure in glomerular capsule to decrease, which in turn idecreases the GFR
What is the tubuloglomerular feedback mechanism?
- GFR increases
- Increased tubular flow past macula densa (early distal tubule)
- Paracrine factor released from macula densa.
- Afferent arteriole constricts, resistance increased.
- Glomerular hydrostatic pressure decreased
- decreased GFR
What other system does feedback from the macula densa activate? (Other than constriction of afferent arterioles?)
The RAAS system.
How is water reabsorped?
Sodium is actively transported from the lumen to the interstitium, this creates an electrochemical gradient that drives anion reabsorption. Water moves by osmosis, following solute reabsorption.
What is transcellular reabsorption?
Transport through tubular epithelial cells (via receptors or transporters)