Lecture 12 - Urinary System
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57 Terms
What is another name for the urinary system?
The excretory system.
What is the main function of the urinary system?
To filter blood to remove metabolic waste, toxins, and excess water, producing urine to maintain homeostasis.
What organs make up the urinary system?
2 kidneys, 1 urinary bladder, 2 ureters, and the urethra.
What is the function of the kidneys?
To filter waste from blood and form urine.
What is the function of the urinary bladder?
To store urine.
What is the function of the ureters?
To connect each kidney to the bladder.
What is the function of the urethra?
Where liquid waste is eliminated.
7 functions of kidneys
urine formation
excretion
regulation of blood volume and pressure
regulation of blood solute concentrations
regulation of extracellular pH
regulation of red blood cell synthesis
regulation of vitamin D synthesis
Urine formation - what is it composed of
Excess water, excess ions, metabolic waste, and toxins.
Kidney excretion
Eliminating waste products during urination.
How do kidneys regulate blood volume and pressure?
By controlling extracellular fluid volume through production and concentration of urine.
How do kidneys regulate blood solute concentrations?
By controlling sodium, calcium, and urea.
How do kidneys regulate extracellular pH?
Through secretion of H⁺.
How do kidneys regulate red blood cell synthesis?
Through secretion of erythropoietin (EPO). - More available oxygen means more EPO production, making more mature red blood cells.
How do kidneys regulate vitamin D?
They form the final bioactive form (calcitriol), which supports bone homeostasis, immune support, and neuro+muscular health.
What is the shape and location of the kidneys?
Two bean-shaped organs located from T12 to L3 vertebrae.
What is the size and weight of each kidney?
About the size of a fist and ~130 grams.
What is the hilum of the kidney?
The concave medial aspect of the kidney
What enters the kidney at the hilum?
Renal artery and nerves.
What exits the kidney at the hilum?
Renal vein and ureter.
What are the two major regions of the kidney?
Renal cortex (superficial) and renal medulla (deep).
What is the function of the renal cortex?
Location of blood-filtering structures.
What composes the renal medulla?
Many cone-shaped renal pyramids.
What are renal pyramids?
Structures whose bases project into the cortex.
What is the renal papilla?
The medullary tip of a pyramid.
What are renal columns?
Extensions of cortical tissue between pyramids.
What is the renal sinus?
A fat-filled cavity in the middle of the kidney that cushions structures and contains tubes that collect urine for movement to the bladder.
What is a nephron?
The functional unit of the kidney.
How many nephrons are in each kidney?
Over 1 million.
What are the two main parts of a nephron?
Glomerular capsule (Bowman’s capsule) and renal tubule.
What is a collecting duct?
A shared duct where many nephrons connect.
Steps in nephron function
glomerulus filtration
tubular reabsorption and secretion
water conservation
What happens during glomerulus filtration?
Blood is filtered; high osmotic pressure and high solute concentration allow water and solutes to leave blood and enter the capsule.
What is glomerular filtrate?
The fluid that enters the nephron after filtration.
What happens during tubular reabsorption?
Water and solutes (Na, K, Cl, glucose, amino acids) are reabsorbed from tubule into capillaries.
What happens during tubular secretion?
Metabolic waste and other products are secreted into the tubule.
What happens during water conservation?
Urine is concentrated at the collecting duct through water reabsorption.
What is glomerular filtration rate (GFR)?
A blood test that determines how much blood passes through the glomerulus each minute.
How stable is GFR?
Very stable and does not significantly change with large changes in blood pressure.
What factors affect GFR?
Age, sex, and race.
How is GFR determined?
By comparing values of serum proteins (albumin or creatinine) between blood and urine.
What is a normal GFR?
~120 mL/min.
What GFR value is considered abnormal?
Below 90 mL/min.
What GFR value indicates kidney failure?
Under 15 mL/min.
What is hemodialysis?
Using an external machine as an artificial kidney to filter blood.
What is a dialyzer?
A machine that cleans blood and returns it to the body.
How does hemodialysis work?
Blood circulates outside the body, is cleaned, and returned.
What does the term dialysis usually refer to?
Hemodialysis (no difference between terms).
How often is hemodialysis typically done?
4 hours per session, 3 times per week.
When is hemodialysis used?
As an alternative to kidney replacement or while awaiting a transplant.
How many people in the USA have chronic kidney disease?
Over 37 million (~15% of adults).
What are the two treatment options for kidney disease?
Hemodialysis and kidney transplant.
Which treatment provides longer life expectancy?
Kidney transplant.
Kidney transplant advantages:
Patients don’t have to worry about what they eat and drink
Cheaper for NHS overall
Kidney transplant disadvantages
Must take immune-suppressant drugs, increasing risk of infection
shortage of organ donors
kidney only lasts 8-9 years on average
Kidney dialysis advantages
available to everyone
no need for immunosuppressant drugs
kidney dialysis disadvantages
patient must limit salt and protein intake between dialysis sessions
expensive for the NHS
regular dialysis sessions - impacts on the patient’s lifestyle