Renal Structure and Function Flashcards
Two main functions of the kidneys
Rid the body of waste that is either ingested or produced by metabolism
Control the volume and electrolyte composition of the blood
The average kidney in an adult weighs about _____.
150 grams (⅓ pound)
T/F the kidneys lie on the posterior wall of the abdominal cavity, outside of the peritoneum
T
The outside layer of the kidney is a tough, fibrous _______, which is protective
Renal Capsule
the Renal Cortex is where the ___ and ___ are located
glomeruli and arterioles
Within the renal medulla, each kidney contains 8-10 cone-shaped structures called _____
Renal Pyramids
The major calyces join in the middle of the kidney to form the _____
Renal Pelvis
T/F The ureter is a contractile structure
T
urine is stored until emptied through the Urethra by_____
micturition
Motor _____ fibers from S2-S4 initiate bladder contraction
parasympathetic
Which fibers cause contraction of external sphincter muscles, preventing urination until “it’s time” ?
Pudendal somatic motor fibers (under cerebral and brainstem control)
Each human kidney contains roughly _____ urine-creating Nephrons
0.8 - 1 million
T/F The kidneys are continuously generating new nephrons if they become diseased or injured
F - The kidneys are not able to generate new nephrons if they become diseased or injured.
By 80 years of age, a healthy individual will have about ____ of nephrons left
40%
a tuft or ball of capillaries in each nephron, through which large volumes of fluid are filtered from the blood
Glomerulus
The efferent arteriole of the nephron becomes a complex network called the _____
Peritubular Capillaries
The renal circulation is unique in having ____
two capillary beds
Purpose of the bowmans capsule
Collects the filtrate
From Bowman’s Capsule, the filtrate flows into the _____
Proximal Convoluted Tubule
From the Loop of Henle, the fluid passess right by the glomerulus and then reaches the _____ back in the renal cortex.
Distal Convoluted Tubule
Each large collecting duct collects urine from as many as _____ nephrons
4000 nephrons
Two types of nephrons
Cortical Nephrons
Juxtamedullary Nephrons
No matter how deep a nephron lies within the kidney, the _____ is found within the renal cortex
glomerulus
Which loop of henle extend deeper? Cortical or Juxtamedullary?
Juxtamedullary
20-30% of all the nephrons are Juxtamedullary and have long Loops of Henle that extend very deep.
Draped over and through these long Loops of juxtoglomeruler nephrons are a specialized peritubular capillary called _____
Vasa Recta
Blood flow to the kidneys accounts for about ___% of total cardiac output.
22
Arcuate Arteries and Veins run ____ of the renal medulla and renal cortex
along the border
The Peritubular Capillaries drain into the ____
Interlobular Veins
Three excretion processes
Glomerular Filtration
Tubular Reabsorption
Tubular Secretion
Filtrate in Bowman’s Capsule is almost identical to _____.
the plasma
Of all the plasma passing through the glomerulus, ____% of the plasma is filtered
20
the glomerular capillaries have a _____ intravascular pressure
Higher
Systemic capillaries- About 17 mmHg
Glomerular capillaries- About 60 mmHg
The Glomerular Filtration Rate (GFR) is the volume of fluid that _____
filters into Bowman’s Capsule per unit of time.
In an average, healthy adult, the GFR is about_____
125 mL/min
T/F less than 1% of the plasma is eventually excreted in the urine
T
The Filtration Membrane is 3 layers thick:
Capillary Endothelium
Basement Membrane
Epithelial (Podocyte) Cells
The Capillary Endothelium allows for a high rate of filtration because the wall is perforated by thousands of small holes called ____
Fenestrations
What is found in the capillary entothelium?
Contains negatively charged membrane proteins as well (repels plasma proteins)
The Basement Membrane is made of a meshwork of ___ and ____
collagen and negatively charged proteoglycans
As filtered fluid (filtrate) leaves Bowman’s Capsule and moves through the Tubules, it is modified in two different ways:
Reabsorption of water and specific solutes back into the blood
Secretion of other substances from the capillaries into the tubules
all three layers of the filtration membrane have some degree of a ____ charge because of membrane proteins or proteoglycans.
negative
There are two main advantages of a high GFR (125 mL/min or 180 L/day)
It allows the kidneys to rapidly remove waste products
It allows all body fluids to be filtered several times each day.
An example of a waste that is not reabsorbed at all is ____, so essentially all that is filtered gets excreted
Creatinine
Substances that are partially reabsorbed from the tubules back into capillary blood, rate of excretion < rate of filtration
This pattern is typical for many electrolytes, such as Sodium, Chloride, & Bicarb ions
Substances that are freely filtered and not excreted because they are 100% reabsorbed
most of the nutritional substances in the blood, such as glucose, amino acids
Substances freely filtered, not reabsorbed at all, but additional quantities are secreted from the blood into the tubule as the fluid moves along, leading to an excretion rate greater than that of the filtration rate
acids and bases
secretion plays a large role in regulation of the amount of ____ and ____ ions (and others) excreted in the urine
Potassium and Hydrogen
T/F Most waste products of metabolism (such as Urea, Creatinine, Uric Acid, etc.) are easily filtered but poorly reabsorbed (if at all), so excretion rates are high as long as GFR remains high.
T
How are solutes reabsorbed into the capillaries?
Solutes are transported through the cells (transcellular path) by passive diffusion or active transport, or between the cells (paracellular path) by diffusion.
How is water reabsorbed into the capillaries?
Water is transported through and between the cells by osmosis.
The Glomerular Filtration Rate can be increased or decreased depending on alterations to certain variables, including
Glomerular Hydrostatic Pressure
Bowman’s Capsule Pressure
Glomerular Colloid Osmotic Pressure
Capillary Permeability
Relative Resistance of Afferent or Efferent Arterioles
The Net Filtration Pressure is the sum of the ____
Hydrostatic and Colloid Osmotic forces across the glomerular capillaries that either favor or oppose the process of filtration.
What is the primary means of physiologic GFR regulation?
Glomerular Hydrostatic Pressure
Increasing the hydrostatic pressure in the glomerulus ____ the GFR
increases
3 main things than can increase (or decrease) glomerular pressure:
1) Increasing (or decreasing) arterial blood pressure;
2) Afferent arteriole resistance;
3) Efferent arteriole resistance (more to come)
increase in Colloid Osmotic Pressure works to ___ GFR.
decrease
This pressure works against filtration as it directly pushes back on the Glomerular Hydrostatic Pressure
Bowman’s Capsule Hydrostatic Pressure
decreasing the permeability of the capillary membrane will ____ the GFR.
decrease
When required, the kidneys are capable of producing urine that is ___ times the osmolarity of the plasma
4-5
Requirements for excreting concentrated urine
High levels of Antidiuretic Hormone (ADH)
Hyperosmotic Renal Medulla
ADH effect on the kidneys
Increases the permeability to water by stimulating the insertion of Aquaporins into the tubular membrane, thereby opening a channel for water diffusion
This increases the reabsorption of water into the blood and results in small volumes of concentrated urine.
By a process called the _____, the Loop of Henle is used to produce a hyperosmotic renal medulla
Countercurrent Multiplier System
