Module 4: Urinary System Flashcards
Role of kidneys?
Filter blood and produce urine
Role of ureters?
Receive urine from kidneys and carry urine down to bladder via gravity and peristalsis
Role of bladder?
Receives and stores urine; micturition
Role of urethra?
Carries urine from bladder to external environment
Functions of urinary system?
- Filters blood plasma
- Prevents nutrient loss, regulates blood volume, pressure, pH, glucose levels
- Releases hormones
Location of kidneys?
Retroperitoneal paired organs sitting either side of vertebral column; left kidney slightly superior to right because of liver positioning
What is the periotoneum?
Abdominal sac around intestines
What structures protect the kidneys?
11th and 12th ribs, visceral organs, fat, and connective tissue layers
What is the hilum?
Entry/exit point for renal artery, renal nerves, renal vein, and ureter
Function of renal artery?
Supplies kidney with approximately 20% of resting cardiac output, from the abdominal aorta, to be filtered
Function of renal vein?
Takes blood out of kidney to inferior vena cavae
What is the fibrous capsule?
Innermost CT layer of kidney; surrounds entire kidney, comprised of collagen fibres
What is the perinephric/perirenal fat?
Middle CT layer of kidney; thick, cushioning layer of adipose tissue
What is the renal fascia?
Outermost CT layer of kidney; dense, fibrous layer anchoring kidney to surrounding structures
Where is the renal cortex?
Outermost ~1cm of kidney
Role of renal cortex?
Where filtration and reabsorption - namely, waste products/water removed form blood, glucose/proteins/AAs reabsorbed from filtrate into blood - occurs
Where is the renal medulla?
~2-3cm region below renal cortex
Role of renal medulla?
Regulates concentration of urine
Where is the renal sinus? What comprises it?
Central cavity of kidney; renal pelvis, renal calyces, blood vessels, fat
Where are the renal pyramids?
Conical structures extending from cortex to sinus
How many renal pyramids per kidney?
8-18 per kidney
Role of renal pyramids?
Transport urine from the renal cortex to the renal sinus
What is a renal papilla?
Apex of a renal pyramid (facing sinus) which projects into the lumen of a kidney calyx and through which collecting ducts discharge urine
What are renal columns?
Bands of tissue separating adjacent renal pyramids
What comprises kidney lobes?
Renal pyramid + overlying renal cortex + adjacent tissues of renal columns
Role of kidney lobes?
Functional units where urine is produced
Role of minor calyces?
Collect urine produced by a single kidney lobe
What are major calyces?
Fusion of 4-5 minor calyces
Role of major calyces?
Collect urine from minor calyces
What is the renal pelvis?
Large funnel-shaped chamber which is continuous with ureter
How frequently do ureters drain urine from the kidney and transport it to the bladder?
Every ~30 seconds
What are the ureters?
Pair of retroperitoneal muscular tubes extending from kidneys to urinary bladder, firmly attached to posterior abdominal wall, ~25-30cm long
Describe the mucosa of the ureters.
Transitional epithelium (stratified cuboidal/squamous), allowing for expansion of ureter diameter
Describe the muscularis externa of ureters.
Layer of smooth muscle outside mucosa that facilitates peristalsis
- Upper two-thirds: 2 layers (inner longitudinal, outer circular)
- Lower one-third: 3 layers (inner longitudinal, middle circular, outer longitudinal)
Describe the mucosa of the bladder.
Transitional epithelium (stratified cuboidal/squamous), with rugae
Describe the muscularis externa of the bladder.
Layer of smooth muscle outside mucosa that facilitates expulsion of urine; 3 layers (inner longitudinal, middle circular, middle longitudinal), with sphincters
What are sphincters of the bladder?
Bands of skeletal muscle that act as valves, controlling urine flow
Different between internal urethral sphincter and external urethral sphincter?
- Internal urethral sphincter = involuntary
- External urethral sphincter = voluntary
Role and length of urethra in males?
~20-25cm in males, transporting urine and semen
Role and length of urethra in females?
~4cm in females, transporting urine
Describe the mucosa of the urethra.
- Proximal (near bladder): transitional epithelium
- Middle: stratified and pseudostratified columnar
- Distal: stratified squamous
Describe the muscularis externa of the urethra.
- Proximal: 2 layers of smooth muscle (inner longitudinal, outer circular)
- Distal: some skeletal muscle, associated with external urethral sphincter
What is micturition?
Urination; expulsion of urine
When does the urge to urinate occur?
When urine in bladder is at ~200mL
What triggers the micturition reflex?
Stretch receptors in bladder wall
What occurs if the micturition reflex is ignored?
Urine continues to accumulate, and at 500mL, detrusor muscle contractions force internal urethral sphincter open
In what populations does micturition occur involuntarily? Why?
If neurological pathway for control of external urethral sphincter is not established (infants), or not powerful enough to prevent (elderly), micturition occurs involuntarily