Ureters, Bladder and Urethra Flashcards
What is transitional epithelium?
Epithelia that lines calyx’s, urethra and bladder is transitional epithelium. Transitional epithelium is stratified rounded cells, the cells can flatten when they are stretched without pulling apart. Provide protection - we want to stop substances in urine from being exposed to underlying tissues (urine is toxic, acidic and very concentrated - could cause irritation or damage)
What are ureters?
Ureters arise from each renal pelvis at each hilum - slender tubes that carry urine from kidneys to bladder
Renal pelvis is lined by transitional epithelium
Level of hilus is approximately 1st lumbar vertebrae
Ureters descend retroperitoneally through abdomen, vertically from hilum
Peristaltic waves move urine to bladder - urine is propelled via peristalsis along ureters to the bladder
What are the three layers of the ureter?
Layer of transitional epithelium and lamina propria make up the mucosa layer
Smooth muscle is arranged differently in ureters, there is an inner longitudinal layer and an outer circular layer - having circular muscle on outside means when we have peristaltic waves in ureters they close off so things can’t reflux backwards
Adventitia - outer covering of FCT
Folded protective protein plaques found on the inner surface
Where are ureters located?
Ureters run obliquely/diagonally through the wall of bladder at its posterolateral corners - acts as a sphincter/valve: compressed by increased bladder pressure to prevent back-flow
What is the urinary bladder?
The bladder stores and expels urine, full bladder may be 500ml
It is a collapsible muscular sac, when empty bladder collapses along folds (rugae)
What are the different parts of the bladder?
Ureters: carry urine from kidney to bladder
Rugae: folds that allow bladder to expand without greatly increasing pressure
Urethra: carries urine out of bladder
Bladder wall: contains muscle for expulsion of urine
Trigone: triangular region between 2 openings of entry of ureters and 1 opening for urethra (area between 3 openings)
Empty vs full bladder
Empty bladder - pyramidal, lies within the pelvis
Bladder fills - becomes more spherical, expands superiorly into abdominal cavity, can be palpated above pubic symphysis
Where is the bladder located in males and females?
In males, bladder is anterior to rectum, superior to prostate gland (prostate gland surrounds urethra)
In females, bladder is anterior to vagina and uterus, when a female is pregnant uterus expands over bladder hence bladder cannot expand much = need to pee more
What is the urinary bladder wall?
Urinary bladder wall is folded into rugae for expansion. Mucosa of transitional epithelium, below this is detrusor which is smooth muscle under involuntary control. The detrusor has circular, longitudinal and oblique fibres which contract to expel urine from bladder into urethra during urination
What is the urethra?
Urethra is a thin walled muscular tube which drains urine from the bladder out of the body (runs from bladder through to external environment)
Epithelium changes: transitional near base of bladder (for stretch), columnar (useful as has goblet cells - produce mucus), stratified squamous near external opening (protection from abrasion)
Mucus glands protect epithelium from urine, also prevents back-flow
What are the significant differences between males and females urethra?
Females: shorter ~5cm, separate from reproductive system
Males: longer ~25cm, part of reproductive system, initial section surrounded by prostate gland which produces seminal fluid. Has three sections: prostatic (runs through prostate), membranous, spongy/penile
Both: passes through urogenital diaphragm which is where external sphincters are allowing voluntary control over urination
What is the internal urethral/urinary sphincter?
Junction of bladder and urethra, detrusor muscles, involuntary control. If bladder is not too full sphincter is kept shut by sympathetic nervous system (inhibit contraction), once full parasympathetic nervous will relax internal sphincter and overrides SNS to induce urination
What is the external urethral/urinary sphincter?
Located where urethra passed through urogenital diaphragm, skeletal muscle hence under voluntary control
What is urination?
As your bladder fills with urine it expands. Action potentials from stretch receptors are sent to brain. Urgency to urinate increases as signals increase. Internal sphincter relaxes. Conscious relaxation of external sphincter - urination occurs
