Lecture 33 Flashcards
What is transitional epithelium and where is it found?
Transitional epithelium is stratified, rounded cells with random shapes, larger at the top which flatten when stretched and act to provide protection. It is found in the ureters, bladder and part of the urethra.
What are the ureters? What layers do they have and what do they do?
The ureters arise from each renal pelvis at each hilum and are slender tubes which carry the urine from the kidneys to the ladder, it descends retroperitoneally through the abdomen vertically (with some bends) from the hila and movement of urine is via peristaltic waves and gravity. They have three layers, the transitional epithelium is the innermost (closer to lumen, folded protective protein plaques are also secreted from this layer, a waxy substance which provides an osmotic barrier on the apical surface of the cells.), then the muscularis (inner is longitudinal, outer circular, this is opposite to GI tract and is done to prevent urine flowing backwards), lastly is the adventitia, an outer covering of fibrous connective tissue.
How does the ureter entry point into the bladder prevent backflow?
The ureters run obliquely through the wall of the bladder at its posterolateral corners, this oblique angle acts as a sphincter/valve to prevent backflow.
What is the bladder and what are the entry points? What is the clinical importance?
The bladder is a muscular sac which stores and expels urine, when empty the bladder collapses along folds (rugae), it expands without a great increase in pressure when full and has three openings, two for entry of the ureters and one for the urethra out the bottom, the triangular region between these three entry points is known as the trigone andinfections tend to persist here.
What is the bladder shape and location?
When the bladder is empty it is pyramidal and lies within the pelvis, as it fills it becomes more spherical and expands superiorly into the abdominal cavity, it can even be palpated above the pubic symphysis. The male bladder is anterior to the rectum and superior to the prostate gland (wraping around the urethra), the female bladder is anterior to the vagina and uterus.
What are the walls of the bladder?
The bladder wall has three layers, the external adventitia, the massively thick detrusor muscle which contracts to push the urine out using longitudinal, circular and oblique muscle fibres randomly arranged, lastly innermost is the mucosa of transitional epithelium.
What is the urethra, what epithelia does it have and what are the differences between male and female?
The urethra is a thin walled muscular tube which drains urine from teh blader out of the body, the epithelium is transitional near the bladder, then columnar (goblet cells for mucous are here) and then near the external meatus is the stratified squamous for protection. There are mucous glands to provide protection. The male urethra is about five times longer than the female (5 cm vs 25 roughly), and is part of the reproductive system as opposed to the female which is seperate. The male urethra is also divided into three sections (prostatic, membranous and spongy/penile).
What are the two urethral sphincters?
Urethral sphincters have an internal and external sphincter, the external is skeletal muscle and the internal is smooth muscle.
How does urination occur? What is a good example of something which causes issues with this in women?
Urination occurs via bladder filling with urine and expanding, this sends action potentials to the brain via stretch receptors, the urgency increases with signal and the inner sphincter relaxes, conscious relaxation of the external sphincter then occurs and urine leaves. Issues with control can occur due to pregnancy or other issues which lead to incontinence.
