General Boundaries
? Where is it?
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? The perineum lies inferior to the pelvic outlet.
? It is physically separated from the pelvic cavity by the pelvic
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diaphragm.? In the anatomical position, it is the narrow region between
the proximal thighs.
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? In the lithotomy position, its a diamond shaped area.
? It is a diamond-shaped area extending from
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? The mons pubis anteriorly,? The medial surfaces (insides) of the thighs laterally,
? The gluteal folds and superior end of the intergluteal
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(natal) cleft posteriorly .
Definitions
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The perineum is the specific portion of the pelvic region that containsthe external genitalia and the anal opening.
The perineum (perineal compartment) is bounded by the pelvic outlet
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and is separated from the pelvic cavity by the pelvic diaphragm, which is
formed by the levator ani and coccygeus muscles.
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The perinieum consists of structures that fill inferior aperture of pelvis.The pelvic outlet is diamond-shaped and can be divided into 2 triangles:
The anal triangle and the urogenital triangle.
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The superficial part of this region is called the perineum including the
external genitalia ( in the urogenital triangle) and the anus ( in the anal
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triangle). It is also called the pudendal region, being supplied by thepudendal nerves and vessels.
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Specific Deep Boundaries/FibrosseousLandmarks that can be palpated: 4
angles & 4 sides
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Anterior angle: Pubic Symphysis,
arcuate pubic ligament.
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?Note the acute angle in male?Note wider angle in females causing
more flaring of ischial tuberosities
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Anterolateral sides: Ischiopubic rami.
Lateral angles : Two Ischial
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tuberositiesPosterolateral sides: Sacrotuberous
ligaments on the right and left.
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Posterior angle: Tip of coccyx - serving
as a point of attachment for
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Divisions of the Superficial Perineal Region? A line joining the two ischial tuberosities divides the perineum into:
? Urogenital Triangle - the anterior area
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?Anal Triangle - the posterior area
? In the anatomical position, these two triangles are positioned at an
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angle to each other.Urogenital triangle(Anterium Perineum)
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? Laterally by theischiopubic rami.
? Posteriorly by an
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imaginary line between
the ischial tuberosities.
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? Anteriorly by the inferiormargin of the pubic
symphysis
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Membranes in Urogenital Triangle
3 membranes in this region
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stretching across the rami.
From above downwards
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1. Superior fascia of UGD. i.e.part of pelvic fascia
2. Inferior fascia of UGD.
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i.e.perineal membrane.
3. The most superficial
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membrane is membranouslayer of superficial fascia. i.e.
colle's fascia.
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Perineal Fasciae
? The perineal fascia consists of superficial and deep layers.
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? The subcutaneous tissue of the perineum, or superficial perinealfascia, like that of the inferior anterior abdominal wall, consists of
? Superficial fatty layer and Deep membranous layer (Colles fascia).
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? In females, the fatty layer makes up the substance of the labia
majora and mons pubis and is continuous anteriorly and superiorly with
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the fatty layer of subcutaneous tissue of the abdomen (Camper fascia).? In males, the fatty layer is greatly diminished in the urogenital triangle,
being replaced altogether in the penis and scrotum with smooth
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(dartos) muscle. It is continuous between the penis or scrotum and
thighs with the fatty layer of subcutaneous tissue of the abdomen.
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? In both sexes, the fatty layer of subcutaneous tissue of the perineumis continuous posteriorly with the ischioanal fat pad in the anal region.
Membranes in UrogenitalTriangle
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? Between upper & middle is deep perineal space.? Between middle & lower is superficial perineal space.
? Posteriorly all 3 membranes are attached to each other &
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perineal body;thus closing superficial & deep spaces behind.
? Anteriorly superior & inferior fasciae of UGD fuse a little
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behind pubic symphysis & form transverse ligament ofpubis=arcuate pubic ligament.
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Dissection in the urogenital
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triangle region reveals followinglayers from superficial to deep:
1. Skin
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2. Fatty layer of superficial fascia
3. Membranous layer of
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superficial fascia (Colles facia)4. Contents of superficial
perineal space
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5. Perineal membrane (inf. Layer
of urogenital diaphragm)
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6. Contents of deep perinealspace
7. Endopelvic facia (Superior
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fascia of urogenital diaphragm)
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Skin:In male: midline raphe continuous with raphe of scrotum.
In female: perineal raphe leading to midline cleft called vestibule b/w
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labia minora.
Raphe indicates development from fusion of two symmetrical halves.
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Fatty layer of superficial fascia: continuous with the fatty
layer of superficial fascia in lower abdomen - fascia of camper
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Colles fascia:
Membranous layer of
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superficial fascia.Forms lower limit of superficial
perineal pouch.
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Attachments:
lateral: lower margin of
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ischiopubic ramiposterior: attached to
posterior margin of perineal
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membrane
Anterior: continuous with
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dartos muscle of scrotum,superficial fascia of penis and
Scarpa's fascia of lower
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abdomen.
Superficial perineal
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space/pouch:
Interfascial space below
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perineal membraneBoundaries
superior: perineal
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membrane
inferior: Colles fascia
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lateral: ischiopubic ramusposterior: closed by fusion
of perineal membrane and
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colles fascia
anterior: open with deep to
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Dartos muscle andsuperficial fascia of penis
and ant. abdominal wall
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between fascia Scarpa and
External oblique
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aponeurosis.Contents:
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A. Muscles:Ischiocavernosus: cover
crus penis or crus
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clitoridis.
Transversus perinei
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superficialis.Bulbospongiosus: cover
bulb of penis or bulb of
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vestibule.
B. Blood vessels
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Posterior scrotal/labial arteries - branch of perineal or internal
pudendal artery
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Transverse perineal artery- branch of perineal artery.C. Nerves
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Posterior scrotal/ labialnerves: branches of
superficial perineal
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nerve.
Perineal branch of
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posterior femoralcutaneous nerve.
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D. Other structures:Crus penis/ crus
clitoridis.
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Bulb of penis with
urethra traversing it.
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Bulb of vestibulewith greater
vestibular gland.
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Perineal membrane
Inferior fascia of
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urogenital
diaphragm.
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Triangular; apexdirected in the
front.
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Stretched
between
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pubic archAttachments
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lateral: inner surface of ischiopubic ramusanterior: thickened to form transverse perineal ligament.
posterior: perineal body in midline but laterally has free
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margin.
Structures piercing the perineal membrane
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1. Posterior scrotal/labial nerves and vessels
2. Deep artery of penis /clitoris
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3. Dorsal artery of penis or clitoris4. Urethra
5. In male: duct of bulbo-urethral glands and artery to the bulb of penis
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6. In female: vagina
SUMMARY
? The superficial perineal pouch (compartment) is a
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potential space between:
? The membranous layer of subcutaneous tissue
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(colle's fascia).? The perineal membrane (superiorly).
? The ischiopubic rami (laterally).
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? Closed posteriorly and continuous anteriorly
with the space between the membranous layer of
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superficial fascia and external obliqueContents of superficial perineal pouch
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Vessels & nerves of the superficial perineal pouchUrogenital Diaphragm or
Triangular Ligament
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? This consists of two muscles,1. The sphincter urethrae in
which lies the membranous
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part of the urethra (3/4 in.
long), and
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2. The deep transverseperineus.
? These muscles are enveloped
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in two layers of fascia, the
fasciae superior and inferior of
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the urogenital diaphragm(upper and lower layers of the
triangular ligament), forming
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the deep perineal pouch.
Deep perineal Space/pouch:
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Closed interfacial space
inside the urogenital
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diaphragm.Boundaries
?superior: superior facia of
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urogenital diaphragm
?inferior: perineal membrane
(inferior fascia)
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?anterior: transverseperineal ligament
?posterior: fused superior
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and inferior fascia ofurogenital diaphragm
?lateral: inner surface of
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ischiopubic ramiContents:
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A. Muscles?Sphincter urethrae: surround membranous urethra.
?Deep Transverse perinei.
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B. Blood vessels:
?Internal pudendal
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artery and itsterminal branches
?Deep artery of
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penis/ clitoris
?Dorsal artery of
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penis/ clitoris?Artery to the bulb
of penis/ bulb of
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vestibule
C. Nerves
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Dorsal nerve of penis/
clitoris
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D. Other structures
Membranous urethra
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Bulbo-urethral glandsin male
Vagina in female
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CONTENTS OF DEEP PERINEAL POUCHIn Males
In Females
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? Intermediate part of the
? Proximal part of the
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urethraurethra
? External urethral sphincter
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? External urethral sphincter
muscles
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muscles? Bulbourethral glands
. Deep transverse perineal
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? Deep transverse perineal
muscles
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muscles? Related vessels and nerves
? Related vessels and nerves
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APPLIED ANATOMY
Urethral rupture: commonest site is rupture of proximal spongy
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urethra below perineal membrane.
Mode of injury : perineal structure crushed between inferior pubic
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ramus and any hard object like crossbar of bicycleA. In superficial extravasation of urine,Urine escapes through the
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rupture into the superficial perineal pouch, descends into thescrotum, around penis and upto the anterior abdominal wall.
May even reach axilla but never enter thigh due to fusion of fascia
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scarpa and fascia lata just below inguinal ligament.
PERINEAL BODY
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? The midpoint of the line joining the ischial tuberosities is the central point of the
perineum.
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. This is the location of the perineal body, which is an irregular mass, variable in sizeand consistency and containing collagenous and elastic fibers and both skeletal and
smooth muscle.
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? The perineal body lies deep to the skin, with relatively little overlying subcutaneous
tissue, posterior to the vestibule or bulb of the penis and anterior to the anus and anal
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canal.PERINEAL BODY
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? The perineal body is the site ofconvergence and interlacing of
fibers of several muscles,
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including the:
? Bulbospongiosus.
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? External anal sphincter.? Superficial and deep transverse
perineal muscles.
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? Smooth and voluntary slips of
muscle from the external anal
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sphincter, levator ani, andmuscular coats of the rectum.
? Anteriorly, the perineal body
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blends with the posterior border
of the perineal membrane and
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superiorly with the rectovesical orrectovaginal septum
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In MalesIn Females
Disruption of the Perineal Body
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? The perineal body is an especially important structure in
women because it is the final support of the pelvic viscera,
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linking muscles that extend across the pelvic outlet, likecrossing beams supporting the overlying pelvic diaphragm.
? Stretching or tearing the attachments of perineal muscles
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from the perineal body can occur during childbirth, removing
support from the pelvic floor.
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? As a result, prolapse of pelvic viscera, including prolapse ofthe bladder (through the urethra) and prolapse of the uterus
and/or vagina (through thevaginal orifice) may occur.
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APPLIED ANATOMY
Perineal tear:
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Commonly during parturition of nullipara wome
Perineal tear if not repaired cause prolapse
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Prevented by using Episiotomy.Anal triangle(Posterior Perineum)
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Posterior part ofperineum
Boundaries:
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Anteriorly: imaginary
line joining two ischial
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Tuberosities.POSTEROLATERALLY:
sacrotuberous
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ligament
Ischioanal (ischiorectal) fossa:
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A perineal space on both side of anal canal.
Wedge shaped with apex directed upwards.
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Lateral wall vertical and medial wall sloping downward and medially.Fat filled: allows expansion of rectum and anal canal during
defecation.
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Ischioanal (ischiorectal) fossa:
Measurements:
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Vertical- 5cm
Anteroposterior- 5cm
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Transverse- 2.5cmIschioanal (ischiorectal) fossa:
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BoundariesLaterally : obturator internus
and its fascia & ischial
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tuberosity
Medially: levator ani covered by
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anal fascia & external analsphincter
Anteriorly: superficial and deep
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transverse perineal muscles.
Posteriorly: sacrotuberous
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ligament covered by GluteusMaximus
Apex: fusion of obturator and
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anal fascia
Base: skin and superficial fascia
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Ischioanal (ischiorectal) fossa:
Recesses:
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Anterior recess:anterior extension
above the
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urogenital
diaphragm.
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Posterior recess:posterior extension
between
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sacrotuberous and
sacrospinous
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ligamentIschioanal (ischiorectal) fossa:
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Lunate fascia:Arched fascia in ischiorectal
fossa.
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Starts from the periosteum
of ischial tuberosity makes
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medial wall of pudendalcanal, lines obturator fascia
goes towards apex and
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lines anal fascia blends with
it at the level of white line of
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Hilton.Summit of this facia called
tegmentum.
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Ischioanal (ischiorectal) fossa:
Pudendal or Alcock's
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canal:
Fascial tunnel in lateral
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wall of ischiorectal fossa2.5cm above ischial
tuberosity.
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Formed either by
splitting of obturator
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fascia or by separationbetween lunate and
obturator fascia or by
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splitting of perianal
fascia.
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