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What does renal mean?
Pertaining to the kidneys
What is the main function of the renal system?
Regulation of extracellular fluid environment in the human body through urine formation
Name four other functions the renal system has:
Regulates blood volume
Eliminates organic waste products of metabolism
Regulates balance of electrolytes
With the respiratory system, maintains acid-base balance/pH of plasma
Name the structures within the renal system:
Kidneys (2)
Ureters (2)
Urinary Bladder
Urethra
Kidney functions
formation of urine
water and electrolyte balance
secretion of toxins and drugs into urine
gluconeogenesis
What is gluconeogensis?
Synthesis of glucose from AAs during prolonged fasting (also occurs in liver)
Ureters function
transfer of urine to bladder
Urinary Bladder function
storage and micturition
Urethra function
micturition
In the Female Renal System, what do the kidneys do?
Form a filtrate of the blood that's modified by reabsorption and secretion
Urine destined for ________ moves from the kidneys along the ______ to the _______.
excretion; ureters; bladder
*remember KIDNEYS -----> URETERS -----> BLADDER
Where is the urine excreted?
Through the urethra
What is the outer layer of the kidney called?
Renal Cortex
What is the renal cortex the site of?
Glomerular filtration and convoluted tubules
What is the inner layer of the kidney called?
Renal Medulla
What is the renal medulla the site of?
Loops of Henle
Drainage of collecting ducts into the renal pelvis and ureter
What is Micturition?
Contractions of smooth muscle in ureter wall (another word for urination)
What does micturition cause?
Urine to move from ureter to bladder
Bladder walls are made up of what type of muscle?
Smooth muscle (detrusor muscle)
Contraction of detrusor muscles produces what?
Micturition
At the base of the bladder is the:
Internal urethral sphincter
Below the internal urethral sphincter is the:
external urethral sphincter
What does the external urethral sphincter do?
Surrounds the urethra
Contractions can prevent urination
What two things determine the contraction/relaxation of these muscles?
Neuronal input due to stretching of the bladder when it fills
Voluntary decision making
How does blood enter and exit the the kidney?
Enters through the renal artery
Exits through the renal vein
What is the Nephron?
The functional unit of the kidneys, consists of a renal corpuscle and tubule
What two things make up the renal corpuscle?
Glomerular capsule + Glomerulus
About how many nephrons are there in a kidney?
1,000,000
What does the branching of the renal artery lead to?
Afferent Arterioles
What do the afferent arterioles do?
Bring blood to the glomeruli
Blood from renal artery ----> afferent arterioles ----> glomeruli
How much percent of plasma filters out of the glomerulus? And where does it filter out to?
20%; and into surrounding glomerular capsule & then into a tubule
Name the order of what occurs after the filtration of plasma
Plasma filtrates from glomerulus ----> glomerular capsule ----> tubule -----> collecting duct -----> renal pelvis -----> ureters
What does the remaining 80% blood do?
Exits renal corpuscle through efferent arteriole to the peritubular capillaries -The blood then drains into veins that exit kidney as the renal vein
Name the order of what occurs to the 80% of blood
80% of blood in glomerulus -----> efferent arteriole ----> peritubular capillaries ----> renal veins
What does the glomerular/bowman's capsule do?
surrounds glomerulus
In the nephron, fluid filters from the ______ into the _____.
glomerulus; glomerular capsule
What does the proximal convoluted tubule do?
Filtrates from glomerulus, enters its lumen
Reabsorption of salt, water into peritubular capillaries that surround tubule
Secretion of substances into filtrate
What does the collecting duct do?
Distal convoluted tubule empties into it
Duct drains into renal pelvis and then ureters
Glomerula Filtration:
Appx 20% of plasma filters out of glomerulus (capillaries) into the glomerular capsule
How is the plasma filtered?
Filters through large pores in glomerular capillaries called fenestrae
Around _____ L of glomerular filtrate is produced each day, but urine ______ is only around _____ L per day.
180; excretion; 1-2
How much percent of the filtrate is excreted as urine?
1%
How much percent of the filtrate is reabsorbed to the vascular system? And why?
99%; to maintain blood volume and pressure
What is reabsorption?
Return of filtrate from tubules to peritubular capillaries by osmosis
Urine volume varies on what?
On fluid needs of body, so volume of fluid that's reabsorbed also varies
Where is salt and water in filtrate reabsorbed?
Proximal tubule or descending limb of loop henle
What does filtration refer to?
Movement of fluid/solutes from the glomerulus into the capsule and then into the tubules
*Glomerulus ---> Capsule ----> Tubules
What does reabsorption refer to?
Movement of materials from the tubules into peritubular capillaries
Which electrolyte is actively transported out of filtrate, and which one follows?
Na+ and Cl- follows passively by electrical attention
Due to _______, _______ follows salt into the peritubular capillaries
osmosis; water
If water wants to be reabsorbed into the bloodstream by osmosis what needs to happen to the ISF?
The ISF that surrounds the tubule must be hypertonic
Why is the fluid hypertonic?
B/c of the Countercurrent Multiplier System
What allows limbs to interact to create high osmotic pressure in the ISF?
Countercurrent flow in ascending and descending limbs in nephrons and close proximity of limbs
What occurs in the ASCENDING limb of the loop of Henle?
Na+ is actively PUMPED into ISF
Cl- follows Na+ bc of electrical attraction
Not permeable to water so fluid in ascending limb becomes diluted
NaCl accumulates in the ISF here, which increases the osmolarity of ISF
The countercurrent multiplier system does which of the following? A) pumps CI- out of the tubule B) secretes NaCl into the urine C) allows water to diffuse out of the ascending limb D) pumps Na+ out of the tubule E absorbs water into the tubule
D) pumps Na+ out of the tubule
What occurs in the DESCENDING limb of the loop of Henle?
permeable to water but not salt
ISF is hypertonic compared to filtrate here, so water leaves descending limb by osmosis ---> ISF ----> capillaries
hypertonic fluid then enters the ascending limb, where Na+ is actively pumped out and Cl- follows, creating diluted tubular fluid and more concentrated ISF
What is the 3 steps within the Countercurrent Multiplier System in Tubule?
Extrusion of NaCl from ascending limb makes ISF more concentrated. Na+ is pumped out, Cl- follows due to electrical attraction
In descending limb, water diffuses out by osmosis and enteres capillaries. This increases osmolarity of tubular fluid and decreases its volume as the fluid descends
Fluid at the bend of the loop has a high osmolarity, 1200 mOsm. The saltiness of the ISF is multiplied here b/c of the lack of permeability to water
Fluid that enters the collecting duct is _____. What does this conclude?
hypotonic; ISF surrounding collecting duct is hypertonic
What is the collecting duct permeable to and not permeable to? What does this cause water to do?
Permeable to water but not salt so water diffuses out of duct into hypertonic ISF by osmosis
What causes ADH secretion to increase?
Plasma osmolarity increasing
Why must both plasma osmolarity and ADH secretion increase?
To increase permeability of collecting duct to water
What is the action of osmoreceptors in ADH secretion?
Senses changes in water intake that alters plasma osmolarity
Release of _____ is altered to affect water _______ in the kidneys. What does this affect?
ADH; Reabsorption
It affects the volume of urine excretion to maintain blood volume
What is renal plasma clearance?
Volume of plasma that's "cleared" of a substance by kidneys per unit time
How are substances from the plasma removed?
By filtration from glomerulus, or secretion into filtrate
What is secretion?
Movement of substances from the peritubular capillaries into the tubular fluid for excretion in the urine
During Renal Plasma Clearance what occurs to the filtered glucose and AAs?
They're completely reabsorbed in the proximal tubule by active transport
What happens when the concentration of glucose exceeds the capacity of the transporters?
The excess glucose is exerted in the urine = glucosuria
When there is excess glucose in the urine, this is called glucosuria. A)True B) False
A)True
When is filtered Na+ and K+ reabsorbed?
In early part of nephron
What do the concentrations of Na+ and K+ in the urine excreted depend on?
Physiological needs/homeostasis and are adjusted late in the nephron
What do decrease plasma [Na+] activate?
Renin-angiotensin-aldoesterone system
Name some results in secretion of aldosterone (adrenal cortex)
Stimulates Na+ reabsorption to increase plasma
Causes passive reabsorption of Cl-
Water follows by osmosis to increase blood volume
What is the main function of ADH in regards to homeostasis of Plasma Na+
Regulates water reabsorption to regulate urine volume and blood volume
What does the Renin-angiotensin-aldoesterone system do?
Stimulates secretion of aldosterone when Na+ intake is low
What does aldosterone do?
Stimulates Na+ reabsorption in the cortical collecting ducts
How is Potassium filtered?
From the glomerulus, some is reabsorbed
What does aldosterone do when [K+] is high?
Stimulates potassium secretion
What's the equation for Renal Control of Acid/Base Balance?
CO2 + H20 -----> H2CO3 -------> H+ + HCO3-
How do kidneys regulate blood pH?
By excreting H+ in the urine and by reabsorbing bicarbonate
Why is urine slightly acidic?
Almost all of the filtered bicarbonate is reabsorbed in tubules and H+ is excreted
What occurs in acidosis?
Increase plasma [H+] and more in filtrate
Bicarbonate is synthesized in proximal tubule cells to compensate
Bicarbonate enters blood
What occurs in alkalosis?
Decreased plasma [H+] and less in filtrate
Less bicarbonate is reabsorbed to compensate
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