The ureters, urethra and bladder

Question 1

describe transitional epithelium

Answer 1

• stratified, rounded cells
• rounded cells sit over each other in a random pattern, all different random shapes too
• flatten when stretched
• for protection (don’t want urine getting though when the epithelium is stretched, because it could hurt us)

Question 2

describe the features of the ureters

Answer 2

• arise from each renal pelvis at each hilum
• slender tubes that carry urine from kidneys to bladder
• descend retroperitoneally through abdomen, vertically from hila (plural for hilum)
• peristaltic waves move urine to bladder
• they are the delivery path

Question 3

describe the histology of the ureters (layers)

Answer 3

Three layers
- mucosa (transitional epithelium and lamina propria)
- folded protective protein plaques on inner surface (acts as urine resistant barrier)
- muscularis (inner longitudinal, outer circular) - OPPOSITE TO GI. supposedly to keep urine from flowing backwards as outer circular closes down but unproven
- adventitia - outer covering of fibrous connective tissue

Question 4

how do the ureters come into the bladder and why?

Answer 4

Run obliquely through the wall of bladder at its posterolateral corners
- acts as a sphincter/valve: compressed by bladder pressure to prevent backflow
- so stuff can come in via peristalsis but difficult for things to get out

Question 5

describe the features of the urinary bladder

Answer 5

• collapsible muscular sac
• stores and expels urine
• when empty the bladder collapses along folds (rugae)
• when full, the bladder expands without great increase in pressure (due to rugae, same as GI)

Ureters: carry urine from kidneys to bladder
Rugae: folds that allow bladder to expand
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

Question 6

describe the empty vs. full bladder

Answer 6

empty bladder:
- pyramidal
- lies within the pelvis
- wall is very thick when empty because of all of the folds and things

as bladder fills:
- becomes more spherical
- expands superiorly into abdominal cavity
- can be palpated above pubic symphysis

Question 7

describe the difference in bladder location in males and females

Answer 7

Males:
- anterior to rectum
- superior to prostate gland (prostate gland wraps around urethra)

Females:
- anterior to vagina and uterus

Question 8

describe the urinary bladder wall

Answer 8

• folded into rugae for expansion
• mucosa of transitional epithelium
• thick smooth muscle called detrusor
  - longitudinal, circular and oblique fibers (not actual layers bc when we have layers its because we want to be able to move them separately, here they all contract at once)
  - contractions to expel urine from bladder into urethra during urination

Layers:
- mucosa (transitional epithelium and lamina propria)
- submucosa (so thin here because don’t need extra space and glands, won’t be asked about it)
- detrusor
- visceral peritoneum

Question 9

describe the urethra

Answer 9

• thin walled muscular tube
• drains urine from the bladder out of the body
• epithelium changes from transitional near bladder, to columnar, to stratified squamous near external opening
• mucus glands (and also goblet cells) to protect epithelium from urine and lubricate the walls

Question 10

describe the difference in male vs. female urethra

Answer 10

significant differences between males and females
Female:
- shorter (~5cm)
- separate from reproductive system
Male:
- longer (~25cm)
- part of reproductive system
- initial section surrounded by probate gland (which produces seminal fluid)
- 3 sections: prostatic (part with prostate gland around it), membranous (very short, where the urogenital diaphragm is), spongy/penile (urethra is going through the length of the penis)

Question 11

describe the urethral sphyncter

Answer 11

internal urethral/urinary sphincter:
- junction of bladder and urethra
- detrusor muscle
- involuntary control

external urethral/urinary sphincter:
- located where urethra passes through the urogenital diaphragm
- skeletal muscle
- voluntary control

Question 12

describe the process of urination

Answer 12

• bladder fills with urine and expands
• AP from stretch receptors to brain
• urgency increases as signals increase
• internal sphincter relaxes
• conscious relaxation of external sphincter
• detrusa muscle contracts and urine is expelled