Module 5 - The Urinary System Flashcards
What are the 4 key urinary system organs?
- kidneys
- ureters
- urinary bladder
- urethra
What are the 6 functions of the urinary system?
- regulates ion levels in the blood (Na+, Ca2+, K+, Cl-)
- regulates pH of the blood
- secretes erythropoietin (RBC synthesis)
- regulates blood volume and blood pressure
- activates vitamin D (calcium homeostasis)
- Excretes wastes and foreign substances
Where are the kidneys located?
located between the peritoneum and the posterior abdominal wall at the level of T12-L3
Why is the right kidney located lower than the left kidney?
The liver is in the way
What part is the renal hilum of the kidney?
It is part of the external kidney
It is an indentation on the medial surface of the kidney
it is where the ureter, blood vessels, lymphatic vessels and nerves enter and exit
What are the two main regions of the kidney?
- renal cortex (outer)
- renal medulla (inner)
- renal pyraminds (~8-14 cone shaped structures containing kidney tubules)
- renal columns (region between renal pyramids containing blood vessels)
What is the path of urine drainage?
- collecting duct
- minor calyx
- major calyx
- renal pelvis
- ureter
What supplies blood to and from the kidney?
- renal artery
2. renal vein
What is the nephron? What is it comprised of?
the nephron is the basic functional unit of the kidney
comprised of
- the renal corpuscle
- filters blood - renal tubule
- transport filtered fluid
What is the renal corpuscle comprised of and where is it located?
it is located in the kidney cortex
consists of:
- glomerulus
- capillary network - bowman’s capsule
- double walled structure receiving filtered fluid
What is the renal tubule and what are the 3 main sections?
the filtrate passes into the renal tubule
three main sections:
- the proximal convoluted tubule (cortex)
- loop of henle (medulla)
- distal convoluted tubule (cortex)
How does urine formation happen?
Nephrons form urine by 3 processes
- glomerular filtration
- tubular reabsorption
- tubular secretion
What is glomerular filtration?
blood pressure forces water (95%) and solutes through the filtration membrane
glomerular filtration rate: 105-125mL/min
MUST BE KEPT CONSTANT
if too high –> needed substances pass through the tubule system too quickly to be reabsorbed
if too low –> too many filtrate components are reabsorbed, including wastes
Filtered substances: water and all solutes present in blood (except proteins) including ions, glucose, amino acids, creatinine
What gets through the filtration membrane and what does not?
turned back: erythrocytes, white blood cells, platelets, plasma proteins e.g. albumin clotting factors, antibodies, lipoproteins
passed through filter: water, electrolytes, glucose, amino acids, fatty acids, vitamins, urea, uric acid, creatinine
How is GFR used to assess kidney function?
GFR decreases with:
kidney disease, toxic damage to tubules
low blood pressure (e.g due to hemorrhage, severe dehydration, heart failure)
urinary tract obstructions: kidney stones (renal calculi), severe prostatitis (men), tumours, etc
What is tubular reabsorption?
-tubular reabsorption returns most of the filtered water and many solutes back into the blood, about 99%
substances needed by the body (i.e glucose, water, ions) are retained
Water reabsorption is primarily driven by Na+ transport
-Na+ is reabsorbed and water follows by osmosis (to an area of higher Na+ concentration)
Hormones regulate water reabsorption in response to changes in blood pressure or the concentration of blood solutes
- antidiuretic hormone (ADH) makes kidney tubules more permeable to water
- aldosterone increases Na+ reabsorption (and water)
What is tubular secretion?
substances not needed by the body: excess ions (i.e excess ions, ammonia, urea, drugs) are transported from capillaries into the renal tubule (and urine)
the kidneys help maintain blood pH
i.e if blood pH decreases (high [H+]), the kidneys:
- secrete hydrogen ions (acid)
- reabsorb bicarbonate (base)
Maintaining blood pH by the kidney
ALKALOSIS (blood pH too high)
H+ into the blood and HCO3- excreted
ACIDOSIS (blood pH too low)
H+ excreted and HCO3- into the blood
the kidney can selectively secrete or reabsorb H+ and HCO3- ions to maintain pH homeostasis. This occurs mostly in the PCT and the collecting duct
What are ureters? what is their function
=tubules (30cm long) that move urine from the kidneys (renal pelvis) to the bladder
movement occurs by peristalsis (assisted by gravity and fluid pressure)
transitional epithelium allows stretch to accommodate greater volume
mucus producing glands protect the ureter walls from acidic urine
filling of the bladder compresses the ureters to prevent backflow of urine into the kidneys
What is the urinary bladder and its function?
=hollow organ located posterior to the pubic symphysis
inner wall is lined with transitional epithelium
detrusor muscle (smooth, involuntary) forms the bulk of the wall
functions to store urine prior to urination (also called micturition)
What is the urethra and its function?
terminal portion of the urinary system
moves urine from the bladder to the exterior of the body
length in males is 20cm and females is 4cm
in males, semen is also ejaculated through the urethra
in females there is a complete separation of the urinary and reproductive systems
two sphincters control the opening of the urethra:
- internal urethral sphincter –> smooth muscle, involuntary
- external urethral sphincter –> SKELETAL muscle, VOLUNTARY
What is the micturition (urination) reflex?
- 200-400mL of urine in the bladder stimulates stretch receptors to stimulate a urination reflex
- parasympathetic neurons cause (1) the contraction of smooth muscle in the wall of the bladder, and (2) the relaxation of the internal urethral sphincter
a sensation of bladder fullness occurs before the reflex
learned control of the external urethral sphincter (after age of 2-3) can delay or initiate urination
What are bladder infections and cystitis?
females have a much shorter urethra than males, which means microorganisms can more easily gain access to the bladder
bladder infections are therefore more frequent in females
inflammation produces symptoms of pain, difficulty in urination (dysuria) and frequency of micturition
inflammation of the bladder is called CYSTITIS
