bio 30 urinary system
filtration
Where? Glomerulus → Bowman’s capsule
What Moves? Water, ions, glucose, urea, small molecules
Direction? Blood → Filtrate
Selective? No, it's non-selective
process by which water and dissolved particles are pulled out of blood, produces filtrate
reabsorption
Where? Proximal tubule, Loop of Henle, Distal tubule
What Moves? Water, glucose, salts, amino acids
Direction? Filtrate → Blood
Selective? Yes, it's selective
secretion
Where? Distal tubule, Collecting duct
What Moves? Hydrogen ions (H⁺), potassium (K⁺), toxins, drugs
Direction? Blood → Filtrate
Selective? Yes, it's selective
nephron- functional unit of the kidney
Function? Filters blood, forms urine through filtration, reabsorption, and secretion
Main Parts? Glomerulus, Bowman’s capsule, Proximal tubule, Loop of Henle, Distal tubule, Collecting duct
Urine Pathway? Nephron → Collecting duct → Ureter → Bladder → Urethra
1 mil per kidney
composed of many tubes
renal artery D+K
Definition: Supplies the kidney with blood from the aorta, moves into glomerulus
Key Fact: Brings oxygenated blood to be filtered
ureter D+K
Definition: Carries urine from the kidney to the urinary bladder
Key Fact: A tube that prevents backflow with peristalsis
urinary sphincter D+K
Definition: Muscle that controls urine elimination from the bladder
Key Fact: Prevents involuntary urination
filtrate D+K
Definition: The liquid removed from blood by nephrons
Key Fact: Contains water, glucose, ions, and waste
glomerulus D+K
Definition: A cluster of porous capillaries surrounded by Bowman’s capsule, fluid is squeezed out of blood by mechanical filtration
Key Fact: Filters small molecules from blood into the nephron
efferent arteriole D+K
Definition: Carries blood away from the glomerulus, narrower
Key Fact: Leads to peritubular capillaries for reabsorption
renal veins D+K
Definition: Carries filtered blood away from the kidney
Key Fact: Returns blood to circulation
renal pelvis D+K
Definition: The central section of the kidney where filtrate is collected
Key Fact: Connects to the ureter
urinary bladder D+K
Definition: Temporarily stores urine before excretion
Key Fact: Expands when full and contracts when empty
carries blood or filtrate? ureter
filtrate
carries blood or filtrate? glomerulus
blood
carries blood or filtrate? distal tubule
filtrate
carries blood or filtrate? renal vein
blood
carries blood or filtrate? efferent arteriole
blood
carries blood or filtrate? bowmans capsule
filtrate
carries blood or filtrate? urinary bladder
filtrate
carries blood or filtrate? afferent arteriole
blood
carries blood or filtrate? loop of henle
filtrate
carries blood or filtrate? renal pelvis
filtrate
carries blood or filtrate? proximal tubule
filtrate
carries blood or filtrate? renal artery
blood
urethra
Definition: Carries urine out of the body
afferent arteriole
Definition: Carries blood to the glomerulus, wider
loop of henle
Definition: Connects the proximal tubule to the distal tubule, concentrates filtrate by removing more water from it
bowmans capsule
Definition: Receives filtrate from the glomerulus, surrounds the glomerulus, filtrate collected here for transport through the nephron. small molecules and water can pass through, but larger can not
renal cortex
Definition: The outer layer of the kidney
renal medulla
Definition: The middle layer of the kidney, composed of 7 cone shaped renal pyramids- merge to form renal pelvis
kidney
Definition: Cleans the blood and produces urine, bean shaped
distal tubule
Definition: Site of secretion, one of the three urine formation steps
tubular reabsorption
cells in proximal tubule remove h2o and nutrients from filtrate and pass them back into blood, wastes such as urea are retained in the tubule. all glucose (AT), just right salt (AT), least water (O)
tubular secretion
wastes that were not initially filtered out in the bowman's capsule are removed from blood in distal tubule, such as ammonia and drugs (AT)
collecting duct
prepares urine for transport out of the body, then collected in renal elvis where it enters ureter, then bladder, small adjustment to water volume
what do the efferent and afferent arterioles cause
builds up pressure inside because it is wider in and narrower out
mechanical filtration
physical build up of pressure squeezes fluid out of blood, contains all things dissolved in blood plasma
what 3 things does nephron do to filter blood
mechanical filtration, reabsorption, secretion
primary role of kidneys
regulate blood volume and composition so that homeostasis is maintained. this is is achieved through varying the volume and composition of urine
what contributes to blood volume and composition in kidneys
variations in salt and water intake, in the environmental conditions we are exposed to
what hormones are involved in the varying volume and composition of urine
antidiuretic hormone and aldosterone
how is antidiuretic hormone secreted
osomoreceptors in hypothalamus detect fall in concentration of water in blood (relative water volume on each side of a membrane). they stimulate neurosecretory cells in hypothalamus to synthesize and secrete ADH. passes from hypo to the posterior pituitary where its released into blood
what does ADH do
increases permeability of kidney collecting duct to water so more water is reabsorbed and urine volume decreases. (less water in urine)
factors inhibiting ADH release
high fluid intake, high blood volume, low blood sodium levels, alcohol consumption, causes to pee more water. water reabsorption decreases, urine output increases
factors causing ADH release
low fluid intake, low blood volume, high blood sodium levels, nicotine and morphine, causes less water in urine. water reabsorption increases, urine output decreases
factors causing release of aldosterone
low blood volumes stimulate secretion of aldosterone from the adrenal cortex. mediated through complex pathway involving hormone renin from the kindey. causes sodium reabsorption increase, water follows, blood volume restored
What happens to the volume of water in the filtrate as it moves through the Loop of Henle?
The volume decreases because water exits the filtrate.
What happens to the concentration of the filtrate as it moves through the Loop of Henle?
It becomes more concentrated in the descending loop and less concentrated in the ascending loop.
How does sodium (Na+) contribute to the filtration process?
Active transport of Na+ creates a concentration gradient that helps regulate water and solute movement.
Where does the filtrate move after being processed in the Loop of Henle?
Toward the renal vein and eventually to the bladder for excretion.
What is the descending loop permeable to?
Water (but impermeable to solutes).
What happens to water in the descending loop?
Water exits into the medullary interstitium, increasing filtrate concentration.
Where is the most concentrated filtrate found in the Loop of Henle?
At the deepest part of the loop.
What is the ascending loop permeable to?
Solutes (but impermeable to water).
What happens to solutes in the ascending loop?
Solutes exit, making the filtrate less concentrated.
What role does active transport play in the ascending loop?
It pumps out sodium (Na+), reducing filtrate concentration and maintaining the osmotic gradient.
How does the kidney maintain the concentration gradient?
Through active transport of sodium (Na+), which keeps the medullary interstitium salty.
Why is the surrounding medullary tissue salty?
Because solutes exit the filtrate in the ascending loop, increasing osmolarity.
Why does the liver convert ammonia to urea?
Because ammonia is very toxic, and urea is less toxic.
What happens to urea after it is formed?
It is transported to the kidneys and excreted in urine.
What is the main function of urea excretion?
To remove nitrogenous waste from the body safely.
substances excreted by skin
water, salt, urea (sweat)
what organ excretes co2 gas
the lungs
what organ is responsible for deactivating and excreting toxins in the body
the liver
which organs reabsorb water back into the body
kindeys and large intestine
which organs excrete extra water the body doesnt need
kidneys, skin, lungs