PERINEUM Flashcards
what is the perineum?
the shallow compartment between the anus and the urethral opening, including both skin and underlying muscle.
position and shape of the perineum, and what does it include
- diamond shape
- lies inferior to the pelvic floor
- includes the anus and external genitalia
- bounded by the pelvic outlet
- contains 2 triangles —> anal triangle and urogenital triangle
how is the perineum separated from the pelvic cavity?
separated by the inferior aspect of the pelvic diaphragm
where does the line extend from, dividing the perineum into the 2 triangles, and what is at the midpoint of this line?
line between the anterior ends of the ischial tuberosities
the midpoint of this line is the location of the perineal body = central tendon of the perineum
what is in the anal triangle?
- anal canal
- anus
- external anal sphincter (maintains closure of the anus)
what is the space surrounding the anus called and what is it filled with?
ischiorectal fossa - filled with fat and connective tissue which allow for the expansion of the anal canal during defacation
what does the urogenital triangle contain?
- external genitalia
- orifices of urethra and vagina
- supportive tissue and fascia
innervation for urogenital triangle
perineal nerve, a branch of the pudendal nerve (S2, S3, and S4)
name the 5 muscles the urogenital diaphragm contains
- superficial transverse perineus
- deep transverse perineus
- bulbospongiosis
- ischiocavernosis
- sphincter urethra (external)
superficial transverse perineus: origin, insertion and action
origin: ischial tuberosity and ramus of ischium
insertion: perineal body
action: fixation of perineal body, support of pelvic floor
deep transverse perineus: origin, insertion, action
origin: medial surface of the ischial ramus
insertion: perineal body ( also some fibres insert into the vaginal wall in females)
action: steadies the perineal body, hence supportive of overall UG diaphragm for pelvic floor and viscera
bulbospongiosis: origin, insertion, action
origin: perineal body
insertion: perineal body
action: stabilises perineal body, assists erection of penis/clitoris, females = (clenches vagina), expresses secretions of greater vestibular glands, male = expels semen and urine from urethra
ischiocavernosis: origin, insertion, action
origin: ischial tuberosity
insertion: clitoris
action: assists the bulbospongiosis muscle
spinchter urethra (external): origin, insertion, action
origin: medial surface of the inferior pubic ramus
insertion: some fibres encircle from the membranous urethra in the male and form a true voluntary sphincter that compresses the urethra. also extends to the base of the bladder and invests the prostate anteriorly and anterolaterally.
action: voluntary sphincter of the urethra constricts the membranous urethra in the male and compresses the urethra and vagina in the female.
what happens to the perineum during childbirth? how is bowl incontinence caused?
during the 2nd stage of labour, the baby’s head pushes down on the perineum which becomes thin, stretched and susceptible to tearing. the tear may extend to the anus — bowl incontinence.
what is the superficial perineal pouch? what is it bounded by? what does it consist of?
= potential space between the perineal fascia and perineal membrane.
- bounded laterally by the ischiopubic rami
- consists of: superficial transverse perineus, ischiocavernosus, bulbospongiosus
what is the deep perineal pouch? what does it consist of? what is it bounded by?
= a potential space between the deep fascia of the pelvic floor and the perineal membrane
- consists of: deep transverse perineus, external urethral sphincter
- bounded inferiorly by the perineal membrane, superiorly by the inferior fascia of the pelvic diaphragm and laterally by the inferior portion of the obturator fascia
which arteries pas through the sciatic foramen to supply the buttock region?
superior gluteal artery and inferior gluteal artery
what arteries supply the bladder?
the superior and inferior vesical arteries
what artery supplies the lower part of the rectum?
middle rectal artery
what artery do the uterine arteries arise from?
the internal iliac artery
where does the internal pudendal artery travel? where does it end up? what do its branches supply?
goes out through the greater sciatic foramen, around the sacrospinous ligament, and back in through the lesser sciatic foramen. Ends up below the pelvic diaphragm.
its branches supply the anal sphincter, the pelvic diaphragm, the external genitalia.
what is an episiotomy?
a surgical incision made in the perineum during the second stage of labour
