Perineum Flashcards
What is the most inferior region of the trunk?
the perineum
where is the perineum located ?
at the pelvic outlet, the inferior margin of the pelvis and spinal column
*between the buttocks and the thighs
what are the boundaries of the perineum?
pubic symphysis, ischiopubic rami, the ischial tuberosities and coccyx
a transverse line between the ischial tuberosities subdivides the diamond shaped pelvic outlet into an
anterior urogenital triangle and posterior anal triangle
what passes through the urogenital triangle
urethra and vagina
what passes through the anal triangle?
the anal canal
A sheet of skeletal muscle that closes the pelvic outlet or forms the floor of the pelvis
the pelvic diaphragm
what is the major function of the pelvic diaphragm?
to support the pelvic contents
what muscle runs from the coccyx to the ischial spine and reinforces the pelvic outlet posteriorly?
coccygeus muscle
group of muscles that make up the major portion of the pelvic diagphragm
levator ani
the levator ani is a group of muscles that can be subdivided into?
pubococcygeus, puborectalis and iliococcygeus
most important of the levator ani muscles? what does it do?
puborectalis- it creates a sling that reinforces the rectoanal flexure- this is extremely important for fecal continence
during defecation, what muscle must relax to allow the bend where the rectum joins the anal canal to relax?
puborectalis
where do the fibers of the levator ani decussate between in females and males? what do they decussate into?
in females- between the vagina and anus
in males- between the prostate gland and the anus
they decussate into a mass of fibrous tissue called the central tendon of the perineum
what is the thickest portion of the levator ani and provides main support of the pelvic floor?
central tendon of the perineum
because the pelvic diaphram does not cover the pelvic outlet completely, what space is left open?
urogenital hiatus
what passes through the urogenital hiatus in males and females
men- urethra
female- urethra and vagina
the urogenital diaphragm extends between? what does it consist of?
the two ischiopubic rami and consistes of two layers of fascia with an intermediate layer of skin
the muscular layer of the urogenital diaphragm includes?
the more anterior sphinter urethrae and the more posterior deep transverse perineus
what forms the voluntary sphincter when you relax and begin urinating
sphincter urethrae
what muscle contributes to the perineal body
the deep transverse perineus
what is the arrangement of the layers of the pelvic diaphragm from superficial to deep
muscles of the erectile tissue
UG diaphragm
Pelvic diaphragm
pelvic outlet
the web-shaped space between the pelvic diaphragm and the obturator internus muscle is the?
ischioanal or ishiorectal fossa.
in a normal specimen, what is the ishioanal specimen filled with?
fat, and the inferior rectal vessels and nerves that supply the anal sphincter, lining of the anal canal and perianal skin
what is the purpose of the fa in the ishioanal fossa?
the loos fat allows the anal canal to expand during defecation
where is ischioanal fossa located?
the ischioanal fossa extends anteriorly deep to the urogenital diaphragm on either side of the midline and extend posteriorly between the gluteus maximus muscle and pelvic diaphragm
where is the attachment sire for erectile tissue and its muscular coverings
the perineal membrane (inferior fascia) of the urogenital diaphragm
in both sexes there are two lateral cylindrical masses of erectile tissue called
corpora cavernosa
the portions of corpora cavernosa that attached to the ischipubic rami and perineal membrane are called the
crura
where does the remainder of the corpora cavernosa go?
into the body of the clitoris or penis
the more medial erectile tissue is called the? How is this different from corpora cavernosa?
corpus spongiosum
there is a difference in males and females with this tissue
what is difference between males and females for the corpus spongiosum?
females have two parallel masses of corpus spongiosum that are separated by the urethra and vagina (vestibular bulbs)
males have one single midline mass (they did have two but they fused together in early development to enclose the terminal section of the urethra (penile urethra)
portion of the corpus spongiosum that is attatched to the perineal membrane in males is called? this continues into? and dilates at what end to form what?
bulb
body/shaft of the penis
dilates at its distal end to form the glans penis (head of the penis)`
what covers the components of erectile tissue that are attached to perineal membrane but do not continue onto the body of the clitoris or penis?
Skeletal muscles
what muscles cover the crura? where do they arise from?
ischiocavernosus muscle
ischiopubic rami and the inferior surfaces of the crura
what muscle cover the bulbs? where do they arise from?
bulbospongiosus
the bulb and inferior fascia of the urogenital diaphragm
contraction of the bulbospongiosus in males and females do what?
in males, it ejects any content (urine, semen) from the penile urethra
in females, these muscles are split in the midline allowing the vagina and urethra to pass between two halves
what muscle arises laterally from the ishchiopubic rami at the posterior edge of the urogenital diaphram and insert into the perioneal body.
superficial transverse perineus muscle
some fibers of the superficial transverse perineal muscle blend with?
the external sphincter of the anus that surround the anal opening and keeps the anus closed
the external sphincter of the anus attaches
posteriorly into the anococcygeal ligament
and anteriorly into the perineal body
erectile tissue receives what type of innervation from the pelvic splanchnics?
parasympathetic innervation
what is the pathway of parasympathetic fibers in erectile tissue
the parasympathetic fibers join sympathetic and viscerosensory fibers in the inferior hypogastric plexus (which lies on either side of the rectum)
what is the pathway of fibers in males to erectile tissue
the inferior hypogastric plexus (carrying sympathetic, viscerosensory and parasympathetic fibers) send branches to the seminal vesicles and prostate to from the prostatic plexus around the prostate. some extend superiorly to form the vesical plexus and innervate the bladder. form the prostatic plexus parasympathetic fibers can reach erectile tissue by
- traveling anteriorly beneath the pubic symphysis to supply distal segments of erectile tissue
- traveling inferiorly along the urethra to supply proximal segments of the erectile tisse
because parasympathetic fibers all pass next to the prostate, if these fibers are damage during a prostatectomy what happens?
the patient will be impotent
what is the pathway of parasympathetic fibers in females to erectile tissue
Fibers travel anteriorly from the inferior hypogastric plexus towards the cervix of the uterus and upper vagina to for the uterovaginal plexus. Some fibers from the plexus extend to form the vesical plexus and innervate the bladder. Erectile tissue of the clitoris and vestibular bulbs are innervated by parasympathetic fibers from the uterovaginal plexus that travel
- anteriorly beneath the pubic symphysis to supply the body of the clitoris
- down along the surface of the vagina to the erectile tissue of the vestibular bulbs
if parasympathetic fibers are damaged during a hysterectomy, what happens?
the patient will have a reduced sexual response
trace parasympathetic innervation from its origin in the CNS to its target
lateral horn, S2-S4 ventral rami pelvic splanchnics inferior hypogastrics plexus uterovaginal/prostate plexus penetrate diaphragms
what is the weigh bearing point o the pelvic outel?
central tendinous point (perineum)
several muscle converge at the central tendinous point, what are they? what happens to them at that location?
the bulbospongiosus, superficial transverse perineus, external anal sphincter and deep transverse perineus muscle. they all become fibrous
what fibers provide main support at the central tendon?
pubovaginalis (between the vagina and rectum)
and the levator prostate (between the prostate and the rectum)
muscles attaching to the perineal body include
-puboccygeus (pubovaginalis or levator porstatae) of the pelvic diaphragm
- external anal sphincter
- bulbospongiosus
- deep transverse perineus
- superficial transverse perineus
perineal trauma can be classified as either anterior or posterior and range in severity. What are the degrees?
first degree- (involving the perineal skin only)
fourth degree (extending to the anal sphincter and anal epithelium
ways to prevent perineal trauma?
- perineal massage during late pregnancy,
- use of position changes
- warm compresses on the perineum
- avoidance of directed pushing and fundal pressure during the second stage of labor
- use of vacuum extraction
steps of an episiotomy?
- pudendal block- anesthetizes the pudendal nerve which provides sensory innervation to the area
- physician palpates ischial spine
- physician inserts a needle through the skin and aims it towards the ischial spine to inject the anesthetic
- incision is made through the posterior wall of the vagina and continues along he midline into the perioneal body or diagonally away from the vagina (to avoid the external anal sphincter)
- after delivery the incision is sutured
additional sutures may be placed through the posterio wall of the vagina into the fibrous tissue of the perineal body to tight up any laxity resulting from delivery. This is called?
perineal repair
The major supply to the perineum comes from the
internal pudendal artery and the pudendal nerve
the pudendal nerve arises from?
the sacral plexus- a network of lumbar and sacral vental rami
what fibers are in the pudendal nerve?
somatomotor, somatosensory and sympathetic
inferior rectal artery distribution
anal canal, external anal sphincter and overlying skin
perineal artery distribution
muscles of the urogenital diaphragm and over the erectile tissue (crura and bulb) and over lying skin of the labia/scrotum
dorsal artery distribution
skin of the clitoris/penis
the first stage of the sexual response is? what fibers cause this? what do these fibers travel through?
an erection
parasympathetic innveration causes dilation that increases blood flow to the erectile tissue
they travel through pelvic splanchnic nerves and prostatic/vaginal plexus on their course to erectile tissues
the second step in the sexual response for males is? what fibers cause this? what happens? how do the fibers travel
emission
this is a sympathetic response that causes contraction of smooth muscle in the vas deferens, prostate gland and seminal vesicles
these fibers pass through the inferior hypogastric plexus to reach their target organs
the final stage in the sexual response is? how does this happen? what fibers are responsible?
ejaculation
for ejaculation to occur there must be stimulation of the skin to the penis to cause reflex contraction of the bulbospongiosus muscle to force semen through the urethra
this is a somatomotor response that follows the pudendal nerve and its perineal branch
in females, which two stages of the sexual response are combined? what fibers cause this?
emission and ejaculation stages are combined.
cutaneous stimulation of the clitoris can lead to a sympathetic response that cause contraction of the smooth muscle and simultaneous somatomotor response that cause contraction of the bulbospongiosus muscle to constrict the vestibule
most of the blood from the erectile tissue of the clitoris and penis drain into? where is the flow from in males and females?
the deep dorsal vein
in females the blood drains from the deep dorsal vein through the vesical plexus that surrounds the urinary bladder-then into the internal iliac veins
in males it drains to the prostatic plexus then to the vesical plexus and finally into the internal iliac veins
