Flashcards in Session 8 - Micturition and incontinence Deck (70)
Give the three main parts of the bladder
Give the histological layers of the bladder wall
• Transitional epithelium
• Lamina propria
• Detrusor muscle
What is the body/fundus of the bladder?
• Temporary store of urine
What is the trigone?
• Ureteric orifices and internal urethral orifice are at the angles of a triangle
What is the neck of the bladder?
• Connects the bladder to the urethra
Outline the structure of the detrusor urinae muscle
• Made from a meshwork of muscle fibres in roughly 3 layers
○ Inner longitudinal
○ Middle circular
○ Outer longitundinal
Why does the bladder have three layers of muscle?
• Arrangement of muscle gives the bladder strength regardless of direction it is being stretched in
What is detrusor muscle supplied by?
• Autonomic nervous system, not under voluntary control
Spinal nerve supply is bilateral
What is the internal urethral sphincter?
• Continuation of the detrusor muscle and made of smooth muscle
• Physiological sphincter at the bladder neck
What is a physiological sphincter?
• A sphincter which is indistinguishable from surrounding tissue at autopsy
What is the primary muscle of continence?
• Internal Urethral Sphincter
What is the external urethral sphincter
• Anatomical sphincter
○ Localised circular muscle thickening to facilitate action
What is the external urethral sphincter derived from?
• Pelvic floor muscles
What type of muscle is the external sphincter?
• Skeletal muscle under somatic, voluntary control
• Contracts to constrict urethra and hold in urine
What are the two innervations of the detrusor?
Outline the parasympathetic innervation of the detrusor
• Pelvic nerve (S2-S4)
• Ach - M3 receptors
Outline the sympathetic innervation of the detrusor?
• Hypogastric nerve (T10-L2)
• NA -> B3 receptors
What is the innervation of the internal urethral sphincter?
• Hypogastric nerve (T10 - L2)
• NA -> a1 receptors
• Pelvic nerve
What is the innervation of the external urethral sphincter?
• Pudendal nerve (S2-S4)
• Spinal motor outflow from Onof's nucelus of the ventral horn of the spinal cord
• Ach -> Nicotinic teceptor
What are the four main functions of the nervous system in relation to the bladder?
• Provide sensation of bladder filling and pain
• Allow the bladder to relax and accomodate to increasing volumes of urine
• To initiate and maintain voiding so bladder empties completely, with minimal residual volume
• To provide an integrated regulation of the smooth muscle
and skeletal muscle sphincters of the urethra
What prevents retrograde ejaculation in men?
• Prostatic urethra
Give the nerve roots which control urine storage
• L1 & L2
Give the nerve roots which control bladder voiding
What are the two phases of the bladder?
What occurs in the filling phase?
• The bladder relaxes and accommodates increasing volumes of urine
• The urethral sphincters increase their tone to maintain continence
What volume of urine is usually required to cause the urge to urinate?
What is the overall capacity of the urinary bladder?
• 350 - 750ml
Outline the nervous pathway which is activated once bladder has a volume of >400ml and urge to urinate arises
• Brain micturition centres -> Spinal micturition centres -> parasympathetic neurones -> Pelvic nerve -> Contraction of detrusor muscle -> Rise in intravesicular pressure
What occurs once there is a rise in intravesicular pressure in the bladder?
• Cerebral context makes a concious, executive decision to urinate by reducing sympathetic stimulation to the external urethral sphincter