Urinary system 3 Flashcards
Urine elaborated in the nephrons is collected in the _____ _______ of each kidney
renal pelvices
Urine is conveyed by the ureters from the kidneys to the _______
bladder
Urine is stored in the bladder before voiding; urethral resistance is _____
high
Relations of the bladder in the male
Anterior:
pubic symphysis
Posterior:
rectum
ductus deferens
seminal vesicles
Superior:
peritoneum
intestines
Inferior:
prostate gland
Relations of the bladder in the female
Anterior:
pubic symphysis
Posterior:
vagina
Superior:
uterus
Inferior & lateral:
muscles of the pelvic floor & sidewall
What is the role of the Ureter?
Tubes carry urine from each kidney to bladder
25–30 cm long & ~3-4 mm in diameter
Pass urine by peristaltic waves (smooth muscle)
Enter the back of bladder
Urine backflow - prevented by ureterovesical valves
Structure of the bladder
Hollow smooth muscle organ
Bladder can be divided into two parts:
1) Body (lying above ureteral orifices)
2) Base (Consisting of trigone and bladder neck
Its muscular wall is formed of smooth muscle cells (detrusor)
Anatomy of the Urinary Bladder
(be able to label and name)
Urothelium
Uretal Orifice
detrusor muscle
Ureter
trigone
Pelvic Floor Musculature
Internal sphincter
External Sphincter
Urethra
Urinary Bladder
The only involuntary organ in the body under voluntary control
All humans are incontinent at birth
Activation of numerous neurologic reflexes are learned in early life to control the bladder
35+ reflexes coordinate activities of bladder smooth muscle, plus striated & smooth muscle of the urethra
Bladder filling and voiding
requires co-ordination between contractile motions of the bladder and reciprocal motions of the bladder neck
Bladder filling:
The detrusor is relaxed
The bladder neck is closed
Bladder Voiding:
The detrusor contracts
The bladder neck opens
Urinary bladder: Micturition reflex
When is ti activated?
when urinary bladder is STRETCHED
= Results in micturition
Control of the Micturition Reflex by Higher Brain centres requires coordination:
- Central nervous system
- Spinal cord ( integrated sacral region)
- Autonomic nervous system (pelvic & hypogastric nerves)
- Somatic nervous system (mainly pudendal nerve)
Micturition reflex /
The bladder switches between 2 phases:
Storage Phase <> Voiding Phase
Storage phase
As the Bladder fills
pressure stays low
due to a highly elastic nature
Manifestation of Laplace Law:
Pressure = 2 x wall tension
in sphere radius
(pressure ^ = radius ^)
i) Bladder full - pressure is detected
ii) Messages sent to brain
Voluntary & local reflexes cause
a switch to Voiding phase
Voiding phase
i) Voluntary signals relax
external sphincter (somatic)
ii) Autonomic contraction
of detrusor muscle
Urethra - excitatory role
which maintains flow till
bladder is empty
Micturition Reflex
Cortex Frontal lobe
Social appropriateness
Periaqueductal
Grey Matter
Neuronal input
(Pelvic nerve) to
Dorsal spinal cord
Sensory nerve endings
detect detrusor muscle stretch
Bladder fills
Medial Pontine - Micturition Centre
Motor nerves
Autonomic & Somatic
Ventral spinal cord
Detrusor muscle
contracts
External sphincter - relaxes
Autonomic innervation of Bladder
= which type of system?
Parasympathetic system
Autonomic innervation of Bladder
= Sympathetic system
Pudendal nerve role
voluntary constriction of
external sphincter to prevent micturition
Micturition reflex
Activated by stretch of urinary bladder (trigone)
Eventually Action potentials travel along sensory nerves in pelvic nerve to sacral region of spinal cord
Integrated at spine - AP travel Along parasympathetic nerve to urinary bladder
- Bladder contracts
External sphincter normally contracted as result of somatic motor nervous system
- Decreased AP cause Urethral sphincter to relax
Micturition reflex
= Normally activated by stretch of urinary bladder (trionge)
- can be activated by irritation from. actuarial infections - in urinary bladder
- desire to void
-occurs when bacteria pass up along urethra, causing inflammation - cause by bacteria from the GI tract, eg E.coli
WBC and RBC in urine
