Lecture 30: The Ureters, Bladder and Urethra Flashcards
What is transitional epithelium?
Stratified, rounded cells that flatten when stretched
What is the purpose of transitional epithelium?
for protection by making a barrier to stop urine leaking through
What are the ureters?
slender tubes that carry urine from the kidneys to the bladder
Ureters arise from each _______ _______ at each _________
renal pelvis
hilum
Ureters descend where?
retroperitoneally through the abdomen, vertically from each hilum
What allows urine to move to the bladder?
peristaltic waves in the ureter
What are the three layers of the ureters?
- transitional epithelium on the lamina propria
- muscularis
- adventitia
Describe the muscularis in the ureter
inner longitudinal, outer circular
Describe the adventitia of the ureter
an outer covering of fibrous connective tissue
What sits on the surface of the transitional epithelium in the ureter?
folded protective protein plaques
What is the advantage of having inner longitudinal and outer circular muscle instead of the other way around?
We don’t want any urine flowing backward back to the kidney so when the outer circular contracts to close over the tube, if there was no longitudinal in the middle, there would always be a little lumen but with both, it would close
How do the ureters enter the bladder?
they run obliquely through the wall of the bladder at its posterolateral corners
What is the advantage to the ureters entering the bladder at an oblique angle?
it acts as a sphinctor/valve compressed by the increased bladder pressure to prevent backflow
What is the urinary bladder?
a collapsible muscular sac which stores and expels urine
What is a feature of the bladder that allows it to expand to accomodate an increased volume?
rugae
What is the bladder wall made of?
detrusor muscle for the expulsion of urine
What is the trigone?
it is the triangular region of the bladder with three openings - one for each of the the two ureters and one for the urethra
What does an empty bladder look like and where does it lie?
it is pyramidal and it lies within the pelvis
What happens as the bladder fills?
is becomes more spherical and expands superiorly into the abdominal cavity
Where is the bladder located in males and how does this differ to the position in females?
- males: anterior to the rectum, superior to the prostate gland (it wraps around the urethra)
- females: anterior to the vagina and uterus
What is the mucosa of the bladder?
- transitional epithelium (with protein plaques closest to the lumen)
What is the detrusor muscle of the bladder made of?
- longitudinal, circular and oblique fibres
What do contractions of the detrusor muscles of the bladder cause?
expulsion of urine into the urethra during urination
What is the urethra?
the thin walled muscular tube that drains urine out of the body
The epithelium changes along the urethra. What are they are where are they?
- transitional epithelium near the bladder
- columnar
- stratified squamous near the external opening
What glands are present in the urethra and why are they needed?
mucous glands secrete mucous to protect the epithelium from the urine
How do the male and female urethra differ?
- females is much shorter and is separate from the reproductive system whereas males is longer and part of the reproductive system
- males have three sections with the initial section surrounded by prostate gland
What are the three sections of the male urethra?
- prostate
- membranous
- spongy/penile
What are the two sphincters of the bladder?
- internal urethra/urinary sphincter
- external urethral/urinary sphincter
Where is the internal urethra/urinary sphincter?
at the junction between the bladder and urethra
Is the internal urethra/urinary sphincter under voluntary or involuntary control? Which muscle is it controlled by?
involuntary
controlled by the detrusor muscle
Where is the external urethra/urinary sphincter?
where the urethra passes through the urogenital diaphragm
Is the external urethra/urinary sphincter under voluntary or involuntary control? Which muscle is it controlled by?
voluntary
controlled by skeletal muscles
What are the 5 steps to urination?
- the bladder fills with urine and expands
- AP from stretch receptors alert the brain
- urgency increases as the signals increase
- internal sphincter relaxed
- conscious relaxation of the external sphincter
