M25: Urine, Ureters, Bladder & Urethra Flashcards
key hormone involved in producing dilute vs concentrated urine
ADH
2 factors that determine if water is reabsorbed
- OSMOLARITY (solute concentration in vs outside of tubule)
- PERMEABILITY OF TUBULE TO WATER
osmolarity inside PCT and cortex
300mOsm/L
at which point are solutes most concentrated in renal tubules? why?
bottom of loop of henle
highest solute concentration outside of tube pulls water from tube out
formation of concentrated urine
- cause: dehydration, heavy expiration
- in collecting duct: in the presence of ADH, principle cells remove water (via AQUAPORIN-2) if surrounding interstitial fluid has high osmolarity
- resulting urine has low water, concentrated solutes
formation of dilute urine
- cause: overhydration, need to get rid of water
- in collecting duct: ADH inhibited, AQUAPORIN-2 not used in principle cells to reabsorb water
- resulting urine has high water concentration
colour in urine due to
- urobilin and urochrome (produced in breakdown of bile)
- colour can also be changed by meds
turbidity (cloudyness) in urine
bacteria, dead cells or fat cause cloudiness when urine left standing
urine pH range
4.6-8.0
average=6.0
anatomy of ureteres
- 25-30cm long, 1-10mm diameter
- renal pelvis to bladder
- retroperitoneal
- attach to bladder on posterior wall, close to floor of bladder
- leads into bladder via URETAL OPENINGS
- PHYSIOLOGICAL VALVE ONLY (no sphincter, closes due to stretch on wall forcing holes closed)
How does urine move through the ureters (3 factors)
- peristalsis
- gravity
- hydrostatic pressure
histology of ureters (deep to superficial)
- MUCOSA
- transitional epithelium (allows stretch)
- lamina propria
- goblet cells produce protective mucous - MUSCULARIS (smooth muscle)
- inner LONGITUDINAL outer CIRCULAR
- distal 1/3 has additional longitudinal layer - ADVENTITIA (layer of areolar CT)
- anchors ureters in place
bladder volume capacity
700-800mL
bladder relative to uterus
bladder is inferior
anatomy of urinary bladder
- URETHRA (passage for urine to leave body)
- TRIGONE (very smooth because mucosa layer pulled tight)
- INTERNAL URETHRAL ORIFACE (bottom of trigone, first of openings out of bladder)
- RUGAE (folds in mucosa layer that allow for expansion)
- DETRUSOR MUSCLE
- 3 layers (longitudinal, circular, longitudinal)
- contracts to push urine into urethra
INTERNAL URETHRAL SPHINCTER - smooth muscle, opens/closes urethra
EXTERNAL URETHRAL SPHINCTER - skeletal muscle
- voluntary opening/closing of urethra
EXTERNAL URETHRAL ORIFACE - opening to outside world!
micturation relfex
urination reflex
- stretch receptors detect volume 200-400mL
- impulses sent to micturation centre at S2 and S3, reflex triggered
- parasympathetic fibres contract detrusor muscle, relax external and internal sphincter muscles
external sphincter not directly relaxed, skeletal muscle signal is blocked instead
- bladder fullness sends signal to brain (desire to urinate)
- cerebral cortex can initiate micturation or delay it for a period of time
What part of the brain controls conscious control of urination?
cerebral cortex
affects external urinary sphincter
anatomy of male urethra
- 20 cm long
- layers: mucosa and muscularis
PROSTATIC URETHRA
- passes through prostate
- internal sphincter stops reproductive secretions from entering bladder
- transitional epithelium becomes stratified columnar or ps columnar
INTERMEDITE (MEMBRANOUS) URETHRA
- passes through perineum (floor of pelvic cavity)
- stratified columnar or ps columnar
SPONGY URETHRA
- passes through the penis
- longest segment
- stratified columnar or ps columnar
- becomes stratified squamous near exterior
EXTERNAL URETHRAL ORIFCE
perineum
floor of pelvic cavity
anatomy of female urethra
- 4cm long
- external orifce between clitoris and vagina
- layers: mucosa and muscularis
- transitional, stratified columnar/ps columnar then stratified squamous
- circular smooth muscle
