8 - Micturition And Incontinence Flashcards
What does micturition mean?
To want to pass urine.
What are the two phases the bladder can be in?
Storage phase,
Bladder voiding phase.
What stimulates the storage phase of urine?
The sympathetic nervous system.
What stimulates the bladder voiding phase?
The parasympathetic nervous system.
What other nervous supply stimulates the bladder (apart from para/sympathetic)?
The somatic nervous system.
What are the three main structures of the bladder?
Body, Trigone and Neck.
Why is the trigone of the bladder named in this way?
The two ureteric and the internal urethral orifices are at the angles of a triangle.
What is the basic function of the body?
To temporarily store urine before voiding.
What is the basic function of the neck?
To connect the bladder to the urethra.
What are the three main muscles of the urinary bladder?
Detrusor urinae muscle (detrusor = to push down; found in the lesser pelvis),
Internal urethral sphincter (physiological),
External urethral sphincter (anatomical).
What is the embryonic origin of the bladder?
It is a hollow, smooth muscle organ derived from the hindgut.
What is the arrangement of the detrusor urinae muscle’s fibres?
- Layers of inner longitudinal muscle fibres,
- Circular arrangement of fibres,
- Layers of outer longitudinal muscle fibres.
What is the benefit of the arrangement of the detrusor urinae muscle’s fibres?
It confers strength (inner longitudinal then circular then outer longitudinal) irrespective of which direction it is being stretched in. It cannot commit peristalsis.
What type of epithelium is found in the bladder? Why is this advantageous to it?
Transitional - a specific type called urothelium, found extensively throughout the urinary tract. It confers the ability to the bladder, and other structures of the urinary tract, to distend.
What is the primary muscle of continence?
The internal urethral sphincter. It is a direct continuation of the detrusor urinae muscle (smooth muscle).
What do we mean when we say, physiological sphincter?
The internal urethral sphincter is an example. It functions as a valve, allowing urine to pass through passively. There is no muscle thickening, its action is solely due to its structure.
What are anatomical sphincters?
The external urethral sphincter is an example. Functions as a valve which can be opened and closed at will. This is due to the circular muscle thickening can contract and relax depending on nervous stimulation).
What is the external urethral sphincter formed from?
The pelvic floor muscles (levator ani etc.).
What nervous systems control the external urethral sphincter?
The somatic nervous system (voluntary control). It is made up of skeletal muscle fibres that when contracted, constrict the urethra, preventing unwanted voiding.
What are the boundaries of the lesser (or true) pelvis?
Roof: pelvic brim Anterior: pubic symphysis Posterior: sacrum, coccyx Lateral: obtutaror internus Floor: pelvic floor
The detrusor urinae muscle is within this structure.
What is the nerve supply to the detrusor urinae muscle?
Sympathetic: Relaxation via B3 (Hypogastric Nerve - L10-T2).
Parasympathetic: Contraction via M3 (Pelvic Nerve - S2-S4).
What is the nerve supply to the internal urethral sphincter?
Sympathetic: Contraction(!) via a1 (Hypogastric Nerve - L10-T2).
What is the nerve supply to the external urethral sphincter?
Somatic: Contraction via Nicotinic Receptors (ACh-mediated; Pudendal Nerve - S2-S4).
What is the storage (or continence phase) controlled by?
Continence neurones. Damage to which leads to reduced bladder capacity, urgency, urinary incontinence (failure to store urine).
