S7) Neuronal Control of Micturition Flashcards
What is micturition?
Micturition is the release of urine from the urinary bladder through the urethra to the outside of the body (urination)
In 5 steps, describe the basic process of micturition
⇒ Urine is made in the kidney
⇒ Urine is stored in the bladder
⇒ Sphincter muscles relax
⇒ Detrusor muscle contracts
⇒ Bladder is emptied through urethra & urine is excreted
Identify 5 functions of the nervous system in relation to the lower urinary tract
- Provides sensations of bladder (distension & pain)
- Relaxes bladder
- Accommodates increasing volume of urine
- Initiates & maintains voiding
- Regulates of smooth & skeletal muscle sphincters
Briefly, describe the structure and location of the bladder
- Location: situated anteriorly in the pelvic cavity
- Structure: hollow, highly distensible, rounded in shape
State 2 functions of the bladder
- Temporary storage of urine (~600ml)
- Assists in the expulsion of urine
The morphological appearance of the bladder varies with filling.
Illustrate this
- When full, it exhibits an oval shape
- When empty, it is flattened by the overlying intestines
The bladder has 3 major functional muscular units that play a critical role in normal functions.
Identify these 3 regions
- Apex
- Neck
- Body
Describe the entry and exit of urine in relation to the bladder
- Urine enters the bladder by the left and right ureters
- Urine exits via the urethra
The internal urethral orifices are marked by the trigone.
What is this?
- The trigone is a triangular area located within the fundus
- In contrast to the rest of the internal bladder, it has smooth walls
There are two sphincters controlling the outflow of urine.
Identify them
Distinguish between the structure of the male and female IUS
- Male IUS consists of circular smooth fibres, which are under autonomic control
- Female IUS has no sphincteric muscle present and is formed by the anatomy of the bladder neck and proximal urethra
The external urethral sphincter has the same structure in both sexes, hence, describe its structure and function
- Structure: skeletal muscle, and under voluntary control
- Function: relaxes during micturition to allow urine flow
Describe the structure and function of the detrusor muscle in the bladder wall
- Structure: specialised smooth muscle, with fibres are orientated in three directions to retain structural integrity when stretched
- Function: allows bladder contract during micturition
Which divisions of the nervous system innervate the detrusor muscle during micturition?
- Parasympathetic nervous system
- Sympathetic nervous system
Where along the extent of the urinary system is the following image from?
Trigone – only location in the bladder where the detrusor muscle consists of three layers
Name the structres M, S, LP shown in the photomicrograph below
M – mucosa
S – submucosa
LP – lamina propria
Which muscle composes layers 1,2,3 shown in the photomicrograph below?
Detrusor muscle – fibres oriented in 3 different directions in area of trigone
In 3 steps, describe the neuronal control over the storage/continence phase of micturition
In 5 steps, describe the neuronal control over the voiding phase of micturition
In the continence phase, as the bladder enlarges what happens to intravesical pressure?
Intravesical pressure increases non-appreciably
Identify structures 1-4 in the coronal section of the male bladder below:
Identify structures 5-9 in the coronal section of the male bladder below:
Identify structures 1-4 in the posterior view of the male bladder below:
Identify structures 5-7 in the posterior view of the male bladder below:
Identify structures 1-4 in the coronal section of the female bladder below:
Identify structures 5-8 in the coronal section of the female bladder below:
Identify structures 9-11 in the coronal section of the female bladder below:
