Anatomy of urinary bladder, urethra and micturition Flashcards
How much urine triggers urinating
400-600ml
Name of superior wall of bladder
Bladder apex
What is the urethral sphincter?
Converge of bladder walls
How is detrusor muscle controlled?
Autonomic innervation (not voluntarily controlled)
What is the internal urethral sphincter?
Autonomically innervated, stops flow of urine into urethra to stop micturition
Where is the prostate in relation to urethra?
Surrounds it
Can we control external sphincter?
Yes it is striated
What is the trigone?
Smooth muscle where ureters enter
What makes the bladder wall tough?
Detrusor
What is the uracus?
In embryo takes urine to be excreted but normally disappears, leaving median umbilical ligament
Function of pubovesical ligament
From pubic bone, around bladder neck and back yo bone, holds neck rigid
Another name for pubovesical ligament in men
Puboprostatic ligament
What is transitional epithelium?
Cells in cube like structure, very organised, sits on lamina propria
What is the serosa?
Flexible fascia
Layers surrounding bladder, outwards to inwards
Perivesical fat Serosa Detrusor muscle Submucosa Lamina propria Transitional epithelium
How do ureters enter bladder?
Oblique fashion on posterior wall
Where is the perineum?
Pubic symphysis to coccyx
Which section of the pelvis is the bladder in?
Lesser
Where does the pelvis divide?
Pelvis inlet - bordered by sacrum and pubic bones
Function of medial umbilical ligament
Inserts into anterior abdominal wall, makes bladder tetrahedral
Two pouches in females
Recto-uterine and utero-vosica;
What is the sigmoid colon?
Large bowel that enters rectum
Why is the lesser pelvis shaped like a funnel?
Levator ani
What is the perineal membrane
Runs in anterior perineum between ischial tuberosities and pubic bone - halfway between perineal layers
Layers of perineal
Deep pouch Perineal membrane Superficial pouch Deep fascia Superficial fascia
Where does the aorta divide and what does it form
L4, forms common iliac arteries
Which artery supplies pelvis?
Internal iliac
Blood supply to bladder
Aorta - common iliac - internal iliac - vesical arteries
Venous drainage of bladder
Vesical venous plexus
Drains to internal iliac vein at multiple points
Continuous with prostate/vaginal plexus
Lymph drainage of bladder
- Deep abdominal and pelvic organs drain to lymph nodes around arteries
- Superficial channels - lymph nodes around major veins
- Bladder drains to internal, external iliac arteries
Which plexus helps with micturition
Inferior hypogastric
How do p/s neurones reach plexus
Pelvic splanchnic nerves
How do sympathetic neurones reach plexus
Sacral splanchnic nerves
Function of pudendal nerve
S2,3, innervates external urethral sphincter for voluntary contraction and inhibits micturition
Which neurones inhibit micturition
Sympathetic
Function of trigone in micturition
Stimulates visceral afferent nerves
Where is the micturition centre
Pons
What happens to bladder at rest?
At rest, visceral afferent nerves stimulate sacral splanchnic nerves to inferior hypogastric plexus - runs to detrusor muscle to relax it - internal urethral sphincter contracts to stop urine reaching urethra
Spinal nerves parasympathetic - pelvic splanchnic nerves and inferior hypogastric plexus
S2-4
Spinal nerves sympathetic - pelvic splanchnic nerves and inferior hypogastric plexus
T11-L2
How does the urethra reach skin?
Anterior aperture of elevator ani Enters deep perineal pouch Enters superficial pouch In F enters vestibule In M enters glans
Where is external urethral sphincter?
Deep pouch
What is cystitis
Irritation of bladder wall
Why are females more susceptible to UTIs
Urethra is only 4cm long
What are Skene’s glands?
Mucous glands wither side of urethra - homologous to prostate
How is the urethra divided in men?
preprostatic, prostatic (dilatable, receives ejaculatory ducts), membranous (narrow, surrounded by external sphincter - catheters get resistance here), penile (receives bulbourethral glands, ends as navicular fossa)
How does epithelium change along urethra?
transitional at beginning, then most is pseudostratified columnar, then stratified squamous (skin
Which muscles help to clear urine from urethra?
Bulbospongiosus in M
Bulbocavernous in F
Blood supply to urethra
M: P: Inferior vesical
M: bulbourethral (from inf vesical)
P: interior pudendal
F: mix of vesical/vaginal/pudendal arteries
Nervous supply of urethra
M: prostatic plexus, pudendal nerve
F: vesical plexus, pudendal nerve
Lymph drainage of urethra
M: anterior drains to inguinal lymph nodes, posterior to iliac lymph nodes
F: iliac nodes
Where is the narrowest part of the urethra in men?
Membranous
Where will a catheter encounter resistance in men?
Prepubic angle
Infrapubic angle
Suprapubic catheter
- Ultrasound to verify full bladder
- Abdominal skin prepared and lidocaine injected into 2 centimetres above symphysis pubis
- Risks: bowel perforation, bleeding, infection, enterovesical fistula
- Indications: urethral injury, absolute urethral obstruction, long-term catheterisation
- Method: direct puncture (mushroom catheter straightened with stylet and advanced into bladder, once catheter is confirmed within bladder, stylet removed) and seldinger technique (needle is inserted until urine aspirated, guidewire placed through needle into bladder and needle removed, dilator advanced over wire enlarging the tract. Dilator replaced with sheath, guidewire removed and catheter placed through sheath, which is peeled away. Balloon is inflated and catheter with drawn until tension felt, catheter connected to drainage system and secured)
