deck_1555952 Flashcards
Define micturition
Wanting to pass urine
Describe the urinary bladder
Is a smooth muscle organIS derived from the hindgutBelongs to “midline structures”
What components make up the urinary bladder?
Body TrigoneNeck
Describe the body of the bladder
Is temporary store of urineIs supplied by the autonomic nervous system so not under voluntary controlIs operated by reflex pathways in the spinal cord
Describe the trigone
Angles of a triangle made between the ureteric orifices and the internal urethral orifice.
Describe the neck of the bladder
Connects the bladder tot he urethra
What are the main muscles that make up the bladder?
Detrusor urinaeInternal urethral sphincterExternal urethral sphincter
Describe the detrusor urinae
Smooth muscle fibres arranged in layers of differing direction. Allow bladder to stretch in any direction and still have strength. Lined with transitional epitheliumFound in true/lesser pelvis of the adult
Describe the nerve supply to the detrusor urinae muscle.
Is from the spinal cordIs bilateral
Why are disorders of the nerve supply varied for the bladder?
Have different nerve supplies to different areas, so can have many combinations of nerve disorders
What are the differences between the internal and external urethral sphincter?
IS is an physiological sphincter – ES is an anatomical sphincterIS is smooth muscle – ES is skeletal muscle IS is involuntary – ES is voluntary
Give the characteristics of the internal urethral sphincter
Is a continuation of the detrusor muscleSmooth musclePhysiological sphincter – no muscle thickening, sphincter action is due to its structure
Give the characteristics of the external urethral sphincter
Derived from pelvic floor musclesSkeletal muscles, under voluntary controlConstricts in order to hold in urineMuscle is thickened in order to facilitate action
What is the parasympathetic innervation of the detrusor muscle?
Pelvic nerve (S2-S4)ACh at M3 receptorsCauses contraction
What is the sympathetic innervation of the detrusor muscle?
Hypogastric nerve (T10-L2)NA at beta3 receptorsCauses relaxation
What is the sympathetic innervation of the internal urethral sphincter?
Hypogastric nerve (T10-L2)NA at alpha1 receptorsCauses contraction
What is the somatic innervation for the external urethral sphincter?
Pudendal nerve (S2-S4)Has spinal motor outflow from Onof’s nucleus (ventral horn of the cord)ACh at nicotinic receptorCauses contraction
What is the continence phase of the urinary bladder controlled by?What does damage to this structure cause?
Neuronal apparatus called the continence neurones .Damage leads to a failure to store urine which reduced the filling capacity, therefore increasing the frequency of passing urine is greater.
Define incontinence
The failure to store urine
Describe the normal voiding reflex
–Afferent signals pass to brain micturition centres, to spinal micturition centres and then to parasympathetic neurones. – Increased stimulation of the pelvic nerve causes the detrusor muscle to contract, increasing intravesicular pressure, causing the internal urethral sphincter to relax. – Cerebral cortex makes a conscious decision to urinate, which reduces the somatic stimulations to the external urethral sphincter causing it to relax– The combination of contraction of the detrusor muscle and relaxation of the external urethral sphincter causes voiding to occur.
Describe the storage of urine in the urinary bladder
Walls of bladder distend when filling with urine due to rugae. Intravesicular pressure hardly changes. Afferent nerves in bladder wall (stretch receptors) signal to void the bladder. Signal to brain micturition centres, which signal to the spinal cord and then the sympathetic neurones which causes the detrusor muscle to relax and the external urethral sphincter to contract, constricting the urethra. This reduced the intravesicular pressure and constricts the urethra.
What are the four functions of the nervous system in relations to the lower urinary tract?
– provide sensations of bladder filling and pain– allow bladder to relax and accommodate urine– initiate and maintain voiding so bladder empties completely– to provide an integrated regulation of the smooth muscle and skeletal muscle sphincters of the ureters.
What types of muscle fibres make up the detrusor muscle?
Longitudinal fibres for the inner and outer layers with circular muscle in the middle layer
What neurones exclusively mediate continence?
Sympathetic neurones
What is the name for the centre on the brain that controls the storage of urine?
Pontine storage centre
What occurs when the bladder wall is stretched?
There is an increase in frequency of action potentials from the urinary bladder to the sacral regions and then onto the ascending spinal pathways to the pons and cerebrum.
What functional parts of the bladder do sympathetic efferents innervate?
DetrusorInternal urethral sphincterTrigone
What functional parts of the bladder do parasympathetic efferent fibres innervate?
DetrusorInternal urethral sphincterTrigone
