Renal system: L34 - The Ureters, Urinary Bladder and Urethra Flashcards
Explain ureter transport pathway. How do they act as valves/sphincters to prevent urine backflow?
2 ureters, one each arise from their respective renal pelvis at the hilum. The ureters are slender tubes that carry urine from kidneys to bladder. They descend vertically retroperitoneally through the abdomen. Peristaltic waves move urine to bladder. Each ureter runs obliquely for about 2cm through the bladder wall (at it’s posterolateral corners) and opens at the lateral angles of the trigone of the bladder. Because of the oblique course through the bladder wall, the ends of the tube act as valves/sphincters when the bladder is full (they are compressed with increased bladder pressure) to prevent backflow of urine.
What is transitional epithelium?
A special epithelium that is made of stratified, rounded cells (stratified for protection) that flatten when stretched. Variably shaped, seemingly randomly displaced within the stratification layers so that it can stretch but still remain strong.
What are the three layers of tissue in the ureter?
An inner layer of transitional epithelium, a muscular middle layer (different to GI: inner longitudinal smooth muscle and outer circular layer for propelling urine through peristalsis) and an outer layer of fibrous connective tissue of adventitia. There are also protein plaques on surface for further protection (repels water) to not damage muscle or adventitia.
What is the function of the urinary bladder?
To store and eject urine.
Describe the inflating and collapsing of the urinary bladder and the shape of the bladder when this occurs.
The bladder sac is made from detrusor muscle, it is a muscular sac that is capable of being inflated and collapsed. When it is empty, the urinary collapses along it folds. This turns the bladder into a pyramidal shape and lies within the pelvis. When full, the bladder expands without great increase in pressure. The bladder shape becomes more spherical and expands superiorly into the abdominal cavity. When bladder is full it can be felt above the pubic symphysis.
Describe the openings to the bladder and the clinical significance of the trigone.
The right and left ureter openings lie at the posterior corners of the triangle-shaped floor and the urethral opening lies at the anterior lower corner.
The trigone is very sensitive to expansion and signals from this area indicate fullness of the bladder to the brain. It also is of clinical importance as infections persist in this area.
Describe the bladder wall.
The mucosa is of transitional epithelium which functions as an osmotic barrier against the high concentrations of urine. (Submucosa is basically fused with mucosa).
Thick muscular layer of detrusor muscle (3 layers of randomised smooth muscle to push urine in all directions) that squeezes urine from the bladder during urination.
The outer most layer is adventitia.
Describe the difference in location of urinary bladder between male and female.
Male bladder -Anterior to rectum, superior to prostate gland (which wraps around the urethra).
Female bladder - Anterior to vagina and uterus.
Describe how the epithelium changes in the urethra.
Transitional near bladder, columnar, stratified squamous (protective) near external opening.
Describe the structure of the urethra generally.
Thin walled muscular tube, drain urine from the bladder, out of the body. Mucous glands found in urethra secrete mucous to help protect epithelium from corrosive urine.
Explain the urethral sphincter (like in GI tract where there is an internal and external).
Internal sphincter - located at junction of bladder + urethra, made of detrusor muscle, involuntary control.
External sphincter - located where urethra passes through urogential diaphragm, skeletal muscle, voluntary control (although not complete control).
Explain the process of urination.
Bladder fills with urine and expands. Action potential sent to brain. Urgency increases as signal increases. Inner sphincter relaxes. Conscious relaxation of external sphincter. Issues with pregnancy-control can occur here.
Explain the significant differences between male and female urethra.
Male have much longer urethra (approximately 25cm) whilst females have shorter urethra (5cm). The male urethra is part of the reproductive system while the female’s is separate from the reproductive system. Male’s urethra is in 3 sections: Prostatic (in the prostate), membranous (urogenital membrane) and spongy/penile (through penis, tissue is spongy).
