W3: Pelvic walls and floor Flashcards
Pudendal canal
Childbirth = pudendal block
Located in the lateral wall of the ischiorectal fossa
Pudendal nerve, artery and vein
Where does inferior rectal come from?
Internal pudendal
What surrounds pelvic brim/inlet?
The pelvic brim is formed by the sacral ala, arcuate line of the ilium, pectineal line of the pubis and pubic crest.
What surrounds pelvic outlet
The pelvic outlet is a diamond-shaped space bounded anteriorly by the pubic symphysis, posteriorly by the coc- cyx, and laterally by the inferior pubic ramus, ischial tuberosity and sacrotuberous ligament.
What does pelvic floor consist of?
Levator ani – formed from three separate muscle components, called the puborectalis, pubococcygeus and iliococcygeus. Fibres insert into the central perineal body. Puborectalis forms a sling around the lower part of the rectum, creating a sphincter-like structure. Relaxation of the sling allows defaecation if combined with relaxation of the internal and external anal sphincters.
Coccygeus – posterior part of the pelvic floor, situated behind the levator ani and anterior to the sacros- pinous ligament.
Pelvic fascia – contributes to the floor of the pelvis by enveloping the superior and inferior aspects of the pelvic diaphragm.
Anococcygeal raphe (body) – a musculotendinous structure passing between the anterior coccyx and the posterior aspect of the anus.
Perineal body – a fibromuscular structure into which many muscles of the perineum, as well as the levator ani, insert. The structure lies just deep to the skin, between the urogenital and anal triangles of the perineum.
Where does perineum lie?
Below pelvic diaphragm
Draw triangles of perineum. Describe
Urogenital triangle – lies between the pubic symphysis anteriorly, the ischiopubic rami and a line betweenthe ischial tuberosities posteriorly. Contains the external genitalia and urethra. Has an additional layer of fascia called the perineal membrane, through which the urethra and, in females, the vagina pass.
Anal triangle – lies between the posterior border of the perineal membrane and body anteriorly and the ischial tuberosities, sacrotuberous ligaments and coccyx posterolaterally. Contains the anal canal and the ischioanal fossae (fat filled triangular spaces lateral to the anal canal).
What is perineal body?
a fibromuscular structure into which many muscles of the perineum, as well as the levator ani, insert. The structure lies just deep to the skin, between the urogenital and anal triangles of the perineum.
Compare urogenital triangle in male and female
Trauma to perineum
Can occur during childbirth
Chronic pain and incontinence - if tearing reaches anal sphincter
Treatment: lateral incision into the perineum to control the tear of the perineal body to lateral side
Called episiotomy
Discuss pelvic floor damage
Etiology, what happens, treatment
Etiology:
- Childbirth (less frequently)
- Previous pelvic surgical procedures
- Chronic straining during bowel
movements.
Weakening of the supportive pelvic
floor can lead to a prolapse of pelvic
floor can lead to a prolapse of pelvic
viscera into the vaginal canal:
Uterine prolapse
Rectocoele (rectal prolapse),
Cystocoele (bladder prolapse)
Enterocoele (small bowel prolapse),
Urethrocoele (urethral prolapse).
Treatment:
pelvic floor exercises
pessary
surgery to support the pelvic organs /
hysterectomy in uterine prolapse.
Summarise pelvic arteries
Internal iliac -> rectum, bladder, internal genitalia (except gonads)
What is the pelvis innervated by?
Pelvic girdle is innervated by the sacral and coccygeal plexuses
Summarise sacral plexus
Describe coccygeal plexus
Coccygeal plexus (S4-S5) innervates the muscles of the pelvic floor (levator ani and coccygeus).
Describe orientation of bony pelvis
The correct orientation of the pelvis is often poorly appreciated. When standing up, the pelvis is tilted in such a way that the anterior superior iliac spines are in the same coronal plane as the pubic symphysis and pubic tubercles. This means that the pelvic inlet inclines anteriorly at 50-60° to the horizontal, whilst the pelvic outlet inclines anteriorly by around 10-15°
What passes through obturator foramen
obturator nerve, artery and vein pass through to reach the lower limb.
What two important ligaments attach to ischium? What foramina do they form?
Sacrospinous ligament – runs from the ischial spine to the sacrum, thus creating the greater sciatic foramen through which lower limb neurovasculature (including the sciatic nerve) transcends.
Sacrotuberous ligament – runs from the sacrum to the ischial tuberosity, forming the lesser sciatic foramen.
Sciatic foramina
Greater = Sacrospinous
Lesser = Sacrotuberous
Differences between male and female body pelvis
Gaps in pelvic floor
Urogenital hiatus – an anteriorly situated gap, which allows passage of the urethra (and the vagina in females).
Rectal hiatus – a centrally positioned gap, which allows passage of the anal canal.
Discuss levator ani muscles
Puborectalis
- pubic bones -> rectal canal (U shaped)
- contract = anorectal angle, bending anteriorly
Pubococcygeus
- Pubic bone -> coccyx
Iliococcygeus
- Ischial spines -> coccyx
Discuss perineal membrane
Describe layers (deep to superficial)
Has pouches on superior and inferior surfaces
The layers of the urogenital triangle (deep to superficial):
Deep perineal pouch – a potential space between the deep fascia of the pelvic floor (superiorly) and the perineal membrane (inferiorly). It contains part of the urethra, external urethral sphincter, and the vagina in the female. In males, it also contains the bulbourethral glands and the deep transverse perineal muscles.
Perineal membrane – a layer of tough fascia, which is perforated by the urethra (and the vagina in the female). The role of the membrane is to provide attachment for the muscles of the external genitalia.
Superficial perineal pouch – a potential space between the perineal membrane (superiorly) and the superficial perineal fascia (inferiorly). It contains the erectile tissues that form the penis and clitoris, and three muscles – the ischiocavernosus, bulbospongiosus and superficial transverse perineal muscles. The greater vestibular glands (Bartholin’s glands) are also located in the superficial perineal pouch. The pouch is bounded posteriorly to the perineal body.
Perineal fascia – a continuity of the abdominal fascia that has two components:
- Deep fascia: covers the superficial perineal muscles and protruding structures (e.g. penis & clitoris).
- Superficial fascia is composed of a further two layers of fascia:
Superficial layer – continuous with Camper’s fascia of the anterior abdominal wall
Deep layer (Colles’ fascia) – continuous with Scarpa’s fascia of the anterior abdominal wall
Skin – The urethral and vaginal orifices open out onto the skin.
Describe clitoris
Anteriorly, the labia minora join to enclose around the clitoris. The clitoris is formed from the glans clitoris and two erectile bodies, made up of paired vestibular bulbs (equivalent of the corpus spongiosum in males) and paired corpora cavernosa.
