112 terms


List the functions of the kidney
Removal waste
Regulate fluid volume
Regulate pH
Produce hormones
Name the three processes that formation of urine depends on.
Name the cone-shaped masses in the renal medulla, the apex of these masses and the tissue between these masses.
Renal pyramids
Renal columns
Starting with the renal papillae, trace the course of urine through the kidney to the ureter.
Papillae drain to minor calyx
Minor calyx drains to major calyx
Major calyx drains to renal pelvis
Renal pelvis drains into the ureter
Starting from the renal artery, trace the blood flow from the renal artery to the afferent artery of the glomerulus.
Renal artery to segmental artery
Segmental artery to lobar artery
Lobar artery to interlobar artery
Interlobar artery to arcuate artery
Arcuate artery to interlobular artery.
Name the venous blood return in order starting from the interlobular veins to the renal vein.
Interlobular vein drains into the arcuate vein
The arcuate vein drains into the interlobar vein
The interlobar vein empty directly into the renal vein
What is the functional and structural unit of the kidney?
Name the tufts of capillaries in a nephron and what property makes them functional in the nephron?
Capillaries are fenestrated (very permeable)
The cup end of the renal tubule that surrounds the glomerulus is the?
Bowman's capsule
The glomerulus and Bowman's capsule combined form the?
Renal corpuscle
Name the components of the renal tubule.
Bowman's capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct
What are the forces utilized in tubular resorption?
Facilitated diffusion
Active transport
Of the filtrate that leaves Bowman's capsule, how much is returned to the circulation, under normal conditions?
99% is returned
Describe the exposed surface of the proximal convoluted tubule.
Thick covering of microvilli that reabsorbs water and secretes substances
List all the substances reabsorbed by the proximal convoluted tubule.
All nutrients
Amino acids
Lipid-soluble solutes
Small protein
What substances are secreted by the proximal convoluted tubule?
Para-aminohippuric acid
Bile pigment
Uric acid
Describe the filtrate that has passed through the proximal convoluted tubule.
Volume is reduced by 65%
Concentration is the same as the concentration of the interstitial fluid
300 mOsm/kg
List the substances reabsorbed in the loop of Henle
Descending limb
Water (freely permeable)
Ascending limb
What is the significance of the loop of Henle dipping into the medulla of the kidney?
Concentration of solutes in the interstitial fluid is high
Describe the filtrate by the time it reaches the end of the descending limb.
Volume reduced another 15%
Concentration of the filtrate is equal to that of the interstitial fluid
1200 mOsm/kg
Describe the fluid that surrounds the ascending limb of the loop of Henle.
Less concentrated as the tubule ascends
Describe the filtrate as it leaves the ascending limb of the loop of Henle.
Solutes diffuse out, making the filtrate less concentrated
100 mOsm/kg
What are the characteristics of the epithelium of the distal convoluted tubule?
Devoid of microvilli
Plays a role in secreting solutes and reabsorbing substances
Contrast the difference between the concentration of the fluid in the filtrate and that of the surrounding interstitial fluid around the convoluted distal tubule.
Filtrate is more dilute than the interstitial fluid
List the substances reabsorbed by the distal convoluted tubule.
What is the special circumstance for water to be reabsorbed by the distal convoluted tubule?
Only permeable to water in the presence of ADH
What is secreted by the distal convoluted tubule?
Where do distal convoluted tubules drain?
Collecting ducts
List the substances reabsorbed by collecting ducts.
Where do collecting ducts drain?
Runs through the renal pyramids and drains urine through the renal papillae
List the two types of nephron beds found in the glomerulus and what their function is.
Glomerulus - produces filtrate
Peritubular capillaries or vasa recta - reclaims most of the filtrate
List the characteristics of the vasa recta.
Receives about 10% of the renal blood supply and flow is sluggish
Freely permeable to water and NaCl
What happens to the blood traveling through the vasa recta?
As blood flows into the medullary depths, it loses water and gains salt and as it emerges from the medulla the process is reversed and the blood picks up water and loses salt
What is the basis for the countercurrent multiplier?
There is a constant difference in the concentration of the filtrate in the descending and ascending loop of Henle
Because of countercurrent flow, the loop of Henle is able to multiply these small changes into a gradient along the vertical length of the loop
The two loops are not in contact with each other but share the same interstitial fluid
What is the relationship between sodium and water in the ascending and descending limb of the loop of Henle?
The more water that diffuses out of the descending limb the 'saltier' the filtrate becomes
The more NaCl the ascending extrudes, the more water diffuses out of the descending limb
Establishes a positive feedback mechanism that produces the high osmolality of the fluid in the descending limb and interstitial fluid
What is the countercurrent exchanger?
Vasa recta (peritubular capillaries)
Describe what happens to urea in the nephron past the proximal convoluted tubule?
Urea in the loop of Henle and distal convoluted tubule remains high because they are impermeable to it
The collecting duct is highly permeable to urea where it diffuses out into the medullary interstitial fluid
Contributes to high osmolality
What is the force that drives fluid and solutes out of the glomerulus?
Blood pressure
The region where the distal convoluted tubule comes in contact with the afferent arteriole and are modified at the point of contact is known as the?
Juxtaglomerular apparatus
What are the characteristics of and function of juxtaglomerular cells?
Smooth muscle cells that are mechanoreceptors and contain secretory granules filled with renin
What are the cells that are found in the distal convoluted tubules that are chemoreceptors monitoring the solute content of the filtrate?
Macula densa
What are the phagocytes that surround the juxtaglomerular apparatus?
Mesangial cells
What is the porous membrane of the glomerulus that allow free passage of water and solutes smaller than plasma proteins?
Name the three layers of that membrane
Filtration membrane
3 layer
Fenestrated endothelium of the glomerular capillaries
Visceral membrane
Intervening basement membrane
What is the significance of the basement membrane?
Confers electrical selectivity to the filtration process
What is the driving force of glomerulus filtration?
Hydrostatic pressure
List and define the factors involved in net filtration pressure.
Glomerular hydrostatic pressure (HPg)
Essentially blood pressure
Colloid osmotic pressure (OPg)
Opposes filtration
Capsular hydrostatic pressure (HPc)
Opposes filtration
NFP = HPg-(OPg + HPc)
What is glomerular filtration rate and what factors govern it.
Volume of filtrate formed each minute by all the glomeruli in each kidney
Governed by:
Total surface area
Net filtration pressure
What is the relationship of glomerular filtration rate to net filtration rate and what happens to glomerular filtration in increased blood pressure and dehydration?
GFR is directly proportional to NFR
GFR rises in elevated blood pressure
GFR drops in dehydration
What type of renal autoregulation is based on the tendency of vascular smooth muscle to contract when stretched? What happens in high blood pressure and low blood pressure?
Myogenic mechanism
Increased blood pressure causes the afferent arterioles to constrict so the blood pressure is not relayed to the glomerulus
Declining blood pressure causes dilation of the afferent arterioles that raise glomerular hydrostatic pressure
Tubuloglomerular feedback is monitored by what type of cells and by what parameters?
Monitored by macula densa cells of the juxtaglomerular apparatus
Monitors filtrate flow rate and filtrate osmolality
With regard to tubuloglomerular feedback, what happens in:
Slow flow, low osmolality
Rapid flow, high osmolality
Slow flow and low osmolality causes vasodilation of the afferent arterioles allowing more blood to the glomerulus
Rapid flow and high osmolality causes the release of a vasoconstrictor that allows more time for the filtering process
What is the hormonal system intrinsic to the kidney that regulates glomerular filtration?
Renin-angiotensin system
What are the factors that induce the renin-angiotensin system?
Reduced stretch of granular JG cells
Stimulation of JG cells from activated macula densa cells
Stimulation of JG cells by renal sympathetic nerves
List the steps involved started with renin and ending in angiotensin II.
Renin released by the JG cells cleaves angiotensinogen to angiotensin I
Angiotensin I is converted to angiotensin II by angiotensin converting enzyme (ACE) produced by the lungs
What is the effect of angiotensin II?
Potent vasoconstrictor that causes the resorption of sodium
List the components of filtrate that are reabsorbed in the proximal convoluted tubule?
All glucose, lactate, and amino acids
90% bicarbonate
65% sodium and water
50% potassium and chloride
List the components of the filtrate that are either absorbed or secreted in the loop of Henle.
Water can leave the descending limb only
Reabsorbed in the ascending limb
Secreted from the descending limb
Absorbed or secreted
List the characteristics of the nephron with regard to the regulation of urine concentration.
The process taking place in the proximal convoluted tubules and the descending limb of the loop of Henle are constant
The distal convoluted tubule and collecting duct can be regulated allowing for drastic changes in the formation of urine
List the hormones that affect the distal convoluted tubule and what their effect are?
Antidiuretic hormone (ADH) causes the tubule to be more permeable to water
Atrial natriuretic peptide (ANP) inhibits the reabsorption of sodium
What is the basic mechanism for the production of dilute urine?
Collecting ducts become impermeable to water due to an absence of aquaporins (aquaporins are present in the presence of ADH)
What hormone is responsible for the formation of concentrated urine and by what mechanism?
Antidiuretic hormone (ADH) produces aquaporins which make the tubules more permeable to water
List the characteristics of the nephron with regards to the regulation of urine concentration.
The process taking place in the proximal convoluted tubules and the descending limb of the loop of Henle are constant
The distal convoluted tubule and collecting duct can be regulated allowing for drastic changes in the formation of urine
What is the relationship of the secretion of ADH and serum osmolality?
Release of ADH is triggered by increases in serum osmolality
Release of ADH is inhibited by decreases in the serum osmolality
What is the relationship of release of ADH and blood pressure?
Increase in blood pressure inhibit the release of ADH
Decreases in blood pressure cause a release of ADH
What is the relationship of serum osmolality and blood pressure regarding ADH?
Secretion of ADH is affected by small changes in serum osmolality but requires big changes in blood pressure
Where is renin produced?
Juxtaglomerular apparatus
What stimulates the release of renin?
Decrease in the blood pressure in the afferent arteriole
Decrease in the Na+ concentration of the filtrate as it passes by the macula densa cells of the juxtaglomerular apparatus
Describe the renin - angiotensin cascade.
Renin converts angiotensinogen to angiotensin I
Angiotensin I is converted to angiotensin II by angiotensin converting enzyme (ACE) produce by the lung
List the effects of angiotensin II.
Potent vasoconstrictor
Stimulates secretion of aldosterone
Increases the thirst sensation
Increase salt appetite
Stimulates ADH secretions
List all the factors that cause the release of aldosterone.
Angiotensin II
Large decrease in the concentration of Na+ in the interstitial fluid or an increase in K+
What is the effect of aldosterone?
Increases the transport of Na+ across the nephron into the interstitial fluid
What provokes the release of atrial natriuretic peptide?
Blood volume in the right atrium increase stretching the cardiac muscle
List the effects of ANP.
Dilates arteries and veins
Inhibits the release of ADH
Inhibits Na+ reabsorption
What is the purpose of autoregulation and what is its mechanism?
Autoregulation is the maintenance of a stable glomerular filtration rate over a wide range of systemic blood pressure
Autoregulation involves the changes in the degree of constriction of the afferent arteriole
What influences autoregulation?
Rate of flow of filtrate past cells of the macula densa
What is the effect of an increase in systemic blood pressure?
Causes constriction of the afferent arteriole to prevent an increase in renal blood flow and filtration pressure
What is the effect of a decrease in systemic blood pressure?
Causes a dilation of the afferent arterioles preventing a decrease in renal blood flow and filtration pressure across the filtration membrane
What is the effect of sympathetic innervation of the afferent arteriole?
Constricts the afferent arteriole which decreases the rate of filtrate formation
What are the two mechanisms by which urine is made dilute?
In the absence of ADH water is not reabsorbed in the distal convoluted tubule
Solutes are removed from the filtrate in the distal convoluted tubule
How dilute can urine become?
As low as 50 mOsm or 1/6th the concentration of plasma
What hormone is necessary for the production of concentrated urine?
By what mechanism does ADH work?
Creates aquaporins in the distal convoluted tubule through which water can pass into the interstitium
Name the two different types of nephrons and which is responsible for producing concentrated urine.
Cortical nephrons
Juxtamedullary nephrons are responsible for concentrating urine
How concentrated can urine become and what determines how concentrated urine can become?
The degree to which urine can be concentrated is dependent on how much ADH can be released
With maximal ADH secretions, up to 99% of the water in filtrate can be reabsorbed
Less than 1 L of urine can be produced in a day
What is water reabsorption that is dependent on ADH known as?
Facultative water reabsorption
What causes ADH to be released?
ADH is continuously released in small amounts unless blood solute concentrations drop too low
ADH release is enhanced when the serum osmolality rises above 300 mOsm/kg
The portion of the cardiac output that is filtered by the kidneys is known as?
Renal fraction
What is the normal range for the renal fraction?
12 to 30%
Average 21%
What is the renal blood flow rate?
1176 mL/min
Define the renal plasma flow rate.
Plasma filtered by the kidney
Renal blood flow rate X portion of the blood made up from plasma
Approximately 650 mL plasma/minute
Define filtration factor.
Plasma that is filtered through the glomerulus into Bowman's capsule and becomes filtrate
Is about 19%
About 125 mL/min
The amount of filtrate produced by the kidney each day is known as the?
Glomerular filtration rate
About 180 L/day
What passes through the filtration membrane?
Proteins under 7nm in diameter or 40,000 daltons
What is the fate of small proteins that pass into the proximal convoluted tubule?
Metabolized by cells of the PCT
What is the formation of filtrate dependent on?
Filtration pressure
What is the formula for calculating filtration pressure?
Filtration pressure = glomerular capillary pressure - (capsule pressure + colloid osmotic pressure)
Define renal clearance and give the formula for determining renal clearance.
Volume of plasma that is cleared of a particular substance in a given time (usually one minute)
RC - renal clearance
U - concentration of the substance in urine
V - volume of urine formation (ml/min)
P - concentration of substances in plasma (mg/ml)
What gives urine its color?
Urochrome - pigment from the destruction of blood
What is a normal pH for urine and what factors cause the pH to vary?
pH 4.5 - 8.0
High protein diet
Whole wheat product
Vegetarian diet
Prolonged vomiting
Urinary tract infection
What measurement on an urinalysis shows if the urine is concentrated and what is the normal range for that test?
Specific gravity
Normal 1.001 - 1.035
List the solutes normally found in urine.
Uric acid
What tube connects the kidneys to the bladder and where is it in relationship to the contents of the abdominal cavity?
List the three layers of the ureters.
Lining mucosa
Muscularis with 2 layers of smooth muscle
What is the nervous innervation of ureters and what is the relationship to the nerves and peristalsis in the ureter?
Autonomic - both divisions
Pain fibers
Peristalsis has more to do with stretch than with muscle
What is the triangular region of the bladder outlined by the openings of the ureters and urethra?
What type of epithelium is found in the bladder?
What is the name of the smooth muscle in the bladder and how are the muscles arranged?
Detrusor muscle
Inner and outer longitudinal smooth muscle with a circular middle layer
What is the epithelial lining of the urethra?
Pseudostratified columnar epithelium
List the two sphincters of the urethra and where they are found.
Internal urethral sphincter formed by the detrusor muscle
External urethral sphincter formed by the urogenital diaphragm
List the three regions of the male urethra.
Spongy or penile
Stretching of bladder activates visceral afferent receptors that activate what?
Spinal reflex
What role does the autonomic nervous system and somatic motor nervous system play in micturition?
Sympathetic inhibits the detrusor muscle
The pudendal motor fiber contracts the external urethral sphincter
Parasympathetic stimulates the detrusor while relaxing both sphincters