General Features of the Pelvis and Perineum Flashcards
where do the bones of the pelvis join?
acetabulum
what is the sacrum made of?
what do the sacral formamina do?
where does the sacrm articulte with ilieum?
5 fused sacral vertbrae
Sacrial foremina allows the passage of sacral nerves
articulats ith the iliem at the sacroiliac joint
what is the sacral promontary?
anterior projection of bone which forms the posteror margin of the pelvic inlet.
Less prominant in female
WIT coccyx?
Inf to the sacrum
attaches the sacrum via the sacrococcygal symphysis - via the fibronocartilaginous joint
comaprison of male and female pelvis
Pelvic inlet - m: narrow/heart shaped. f: oval and round
sub pubic angle - m: acute f: around >80degrees
ischial spines - m: projects madially f: not project medially
greater pelvis - m: deep f: shallow
lesser pelvis - m: narrow, deep and tapering f: wide, shallow and cylinderical
what is the false pelvis?
upper part of the pelvis and the lumbar vertebrae
true pelvis - lower part of the pelvis below the sacral promontary and the sacrum and coccyx.
they are separated by the pelvc inlet
what is teh perineum?
inf t the pelvic floor. it’s boundaris form the pelvic outlet
what is meant by pelvimetry?
measurement of female pelvic inlet to check if the baby can fit through the canal
measure from the acral promontory to the sup margin of pubic bone AND the distance // the ischial spines
WATtwo main ligaments of the pelvis?
Sacrotuberous = scaral to ischial tuberosity
sacrospinous = sacral to ischial spine
THEY form the GREATER and the LESSER sciatic foramenia
On top the sacrospinous lig = greater. // the two lig = Lesser
which nerves pass trough the lesser sciatic foramen?
Pudendal (into the pelvis)
which nerve passes trhough the greater foramen of sciatic?
sciatic nerve
what forms the wall of the pelvis?
BONES: Sacrum, coccyx and inferior half of the pelvic bone
LIGAMENTS - connecting the pelvic bone to the sacrum and the coccyx
MUSCLES - Piriformis and Obturator internus
^^ these stabilise the hip joint
where does the pedundal arise?
Where does it pudendal nerve leave and enter?
what is the trajectory of the nerve?
S2 - S4
LEAVES via the GREATER sciatic foramen inferior to the periformis.
It crosses teh sacrispinous lig and re-enters the pelvic cavity throigh the lesser sciatic foramen
it passes through the pedundal canal formed by the fascia of the obtruatr internus
what are the branches ofthe pudendal?
Inferior rectal nerve Perineal nerve (superficial and deep) The dorsal nerve of the penis and clitoris
what kind of innervation does the pedendal nerve have?
Sensory, motor and autonomic
External genitalia and skin sensation
Levator ani, external urethral and anal sphincters, bulbospongiousus and ischiocavernosus
Sympathetic fibres to the S2-4
what is meant by a pudendal block?
Used for prain during childbirth/chornic pelvic pain. Local anesthetia is given where the nerve crosses. - lateral aspect of sacrispinous lig and near its attachement on the ischial spine.
What does the pelvic floor separate?
PELVIC CAVITY AND PERINEUM (region containing the genitalia and anus)
What are the two parts of the pelvic diaphragm?
Coccygeus (sacrum+coccyx -> ischial spine) - correspoding the sacrospinous ligament
Levator Ani (formed of 3 muscles) (pubic bone -> ischial spine) LOOK @ DIAGRAM
What is the levator ani formed off?
WAT two gaps allowing passage of structures?
iliococcygeal
puboccocygeal
puborectal
muscles
there are two gaps allowing the passage of structures.
- > Urogential hiatus
- > Rectal hiatus
what is the perineal body?
ill defined, connectibe tissue structure
important structures attaach to the PB:-
Lavetor ani
Skeletal muscle sphincters (ext. urethral and anal) sphincter)
when can a pelvic organ prolapse occur?
if the pelvic organ ike the blader or vagina undergoes trayma or poor muscle tone
or if the perineal body is torn during birth
Can be avoided by EPISIOTOMY (perineal body is disscted to allow the baby’s head to pass through the vagina. -> the clean incision is easier to suture than rough tear
WIT ureter?
where does it cross in the pelvic cavity?
WAT the 3 points/junctions?
Imortantance of tehse Jx
smooth muscle tube formed at the hilum of kidney
around 30cm
enters at pelvic inlet and crosses DUCTUS DEFERNS in men and UTERINE ARTERY in women
Jx
Ureteropelvic junction (at the kidney pelvis)
Crossing the oelvic inlet
Entering the bladder
^ these are the sites which kidney stones ay be lodged
what shape is the bladder?
What is the apex attached to and how?
How is the URETHRA achored ?
triangular pyramid
2 ureters
Apex is attached to the umbilius via MEDIAL UMBILICAL LIGAMENT
Urethra achored to the pubic bone by the pubovesicular (female) and puboprostatic ligament (male)
How many walls does bladder have?
3
- serous - outer layer
- smooth muscle - detrusor muscle: PSNS supply.
- transitional epi
What are the sphincters of the bladder mae of?
what is the detrusor made of?
skeletal muscle
smooth muscle
what does the SNS do to the detrusor?
relaxation and the internal urethral sphincter contraction.
what happens when you pee?
detrusor contraction & internal urethral sphincter relaxation - involuntary control (Pelvic splanchnic nerves)
external urethral sphincter relaxation - voluntary control - this is done by inhibiting the motor signal voluntarily
what implication does the pelvic floor have on the dunctionality of vol and invol sphincters?
divides the voluntary and involuntary sphincters
Urinary continence requires a balance between detrusor relaxation and external sphincter contraction
The pelvic floor muscles exert sphincter action on the urethra
As the bladder fills, bladder pressure is increased. But urethral sphincter pressure (maintained by the pelvic floor) exceeds this, maintaining continence.
Normally, when intrabdominal pressure is high (coughing or sneezing), the pressure in the bladder and urethra increases equally, maintaining continence.
Weakness/damage to the pelvic floor can lead to urinary stress incontinence
Damage to the muscles/pudendal nerve can occur during labour*
Pubococcygeusandpuborectalisare most medial and therefore the more prone to injury*
The pelvic floor can be repaired surgically or strengthened by pelvic floor exercises*
describe the structure of the rectum
S-shaped distal part of GIT
has 3-4 transverse rectal fold which act as shelves for faecal material
Involuntary internal sphincter closes the upper and middle portion of the anal canal
where is the anal canal located?
External to the pelvic floor
What is PUBORECTALIS?
Muscle that forms a sling around the rectum. making a 90degree angle // rectum nal canal
-> The damage to this muscle leads to faecal incontincences?
how is defecation aided by muscles?
The pelvic floor helps increase intrabdominal pressure during defecation
When intrabdominal pressure is high, puborectalis relaxes, straightening the anorectal angle
The internal anal sphincter relaxes
The circular muscles of the rectum undergo a wave of contraction to push faeces forwards
The longitudinal muscles of the rectum and lavator ani bring the anal canal upwards so the faeces are expelled.
What is the ischio-anal fossa?
Lateral to the anal canal
Has adipose tissue and contains the pudendal canal (w/ internal pudendal vessels and nerve)
Boundaries:
Base: Skin over anal region
Medial wall: anal canal & levator ani
Lateral wall: obturator internis & ischial tuberosity
