Lecture 30- The ureters, bladder and urethra

Question 1

What is the special type of epithelium often found in the renal system? What is it’s purpose?

Answer 1

• Transitional epithelium
• This is made of stratified, rounded cells which flatten when stretched
• This gives protection as means that cells don’t break apart and allow urine to leech backwards

Question 2

Where are the ureters found and what are their purpose?

Answer 2

• Arise from each renal pelvis at each hilum
• They are slender tubes that carry urine from the kidneys to the bladder
• Descend retroperitoneally through abdomen, vertically from hila

Question 3

What motility pattern is responsible for pushing urine down the ureters?

Answer 3

Peristaltic waves move urine down the ureters to the bladder

Question 4

What is the histology of the ureters like?

Answer 4

Three layers:
-Transitional epithelium
-Muscularis (inner longitudinal,
outer circular)
-Adventitia (outer covering of fibrous connective tissue)

-There are also folded protective protein plaques on inner surface

Question 5

Is the Muscularis of the ureter the same as the GI tract?

Answer 5

• Opposite to the GI tract which has circular layer on the insider and longitudinal layer on outside
• The Muscularis of the ureter is arranged the way it is (circular on outside and longitudinal on inside) as when circular contracts it causes the longitudinal fibers to close over the lumen preventing backflow of urine

Question 6

Where do the ureters run in terms of the bladder? What does this mean about the role of the bladder wall?

Answer 6

• Run obliquely through the wall of bladder at its posterolateral corners
• Bladder wall acts as a sphincter/valve: compressed by increased bladder pressure to prevent backflow

Question 7

What is the urinary bladder like?

Answer 7

• Collapsible muscular sac

- Stores and expels urine

Question 8

What is the bladder like when empty as opposed to full?

Answer 8

-When empty the bladder collapses along folds (Rugae). It is pyramidal in shape and lies within the
pelvis
-When full, the bladder expands without great increase in pressure (~500ml). It can do this as like the stomach it contains Rugae. This causes the shape to become more spherical as it expands superiorly into abdominal
cavity.

Question 9

Why can the bladder expel urine?

Answer 9

It has a muscular wall which can contract

Question 10

What is a trigone?

Answer 10

• Triangular region between 2 openings of entry of ureters and 1 opening for urethra
• This is a place where urine and pool and so is often a source of urinary tract infections (breeding ground of bacteria)

Question 11

What is the role of the urethra?

Answer 11

Carries urine out of bladder

Question 12

Where can a full bladder be palpitated?

Answer 12

Above pubic symphysis

Question 13

How does the location of the bladder differ between males and females?

Answer 13

• Male bladder: Anterior to rectum and superior to prostate gland (wraps around urethra)
• Female bladder: Anterior to vagina and uterus (this causes pressure and frequent peeing when pregnant)

Question 14

What is the wall of the bladder like?

Answer 14

-Folded into Rugae for expansion
-Muscosa of transitional epithelium
-Thick smooth muscle layer called detrusor. This contains longitudinal, circular and oblique fibers.
Contractions of these muscle fibers expel urine from bladder into urethra during urination

Question 15

Name three structures that protect the urinary tract…

Answer 15

• Transitional epithelium
• Protein plaques (waxy substance that sits on surface of epithelium cells)
• Entrance to bladder prevents backflow

Question 16

Why is the muscle in the bladder wall not arranged in neat distinct layers?

Answer 16

Because the muscle layer of the bladder is not for motility just want the whole thing to collapse from all angles to expel urine when fibers contract

Question 17

Name the muscle that forms the wall of the bladder.

What is its function?

Answer 17

Detrusor, to expel urine

Question 18

What is the urethra?

Answer 18

• Thin walled muscular tube

- Drains urine from the bladder out of the body (external)

Question 19

How does the epithelium change along the urethra?

Answer 19

• Transitional near bladder
• Columnar
• Stratified squamous near external opening

Question 20

What is an additional feature of the tissue surrounding the urethra?

Answer 20

Mucus glands to protect epithelium from urine

Question 21

How are the male and female urethras different?

Answer 21

Female:

• shorter (~5cm)
• separate from reproductive system

Male:

• longer (~25cm)
• part of reproductive system
• initial section surrounded by prostate gland (produces seminal fluid)
• 3 sections: prostatic, membranous, spongy/penile

Question 22

How many urethra sphincters are there and how do they differ?

Answer 22

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 23

How does urination occur/ how is it controlled?

Answer 23

• 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 causes expulsion of urine at the appropriate place

Question 24

Which of the following statements is INCORRECT about the bladder?
A. Detrusor muscle forms the bladder wall
B. It is lined with transitional epithelium
C. It is a collapsible sac which stores and expels urine
D. The trigone is a triangular area between the openings of the ureter and two urethras
E. When empty, the bladder collapses along folds called rugae

Answer 24

D. The trigone is a triangular area between the openings of the ureter and two urethras

Not true as there are 2 ureters and 1 urethra

Question 25

Name three places in the urinary tract you would find transitional epithelium.

Answer 25

• Ureters
• Urinary bladder
• Initial part of the urethra