Understanding anatomy of perineum, pudendal canal & UGD

1. Perineum, ischioanalPerineum, ischioanal
fossa, pudendal canal,fossa, pudendal canal,
U.G.DU.G.D
DR. Shittu LAJDR. Shittu LAJ

2. objective

3. Perineum
• is generally defined as the surface region in both males and
females between the pubic symphysis and the coccyx
• The perineum is the region of the body inferior to the
pelvic diaphragm and between the legs.
• However, its definition varies, thus it can refer to only the
superficial structures in this region, or it can be used to
include both superficial and deep structures.
• It is a diamond-shaped area on the inferior surface of the
trunk which includes the anus and in females, the vagina.
• a diamond-shaped space forming the outlet of the
pelvis/corresponds to the outlet of the pelvis

4. • The anogenital distance is a measure of
male feminisation measuring the
distance between the anus and the base
of the penis.
• Measuring the anogenital distance in
neonatal humans has been suggested as
a noninvasive method to predict
neonatal and adult
reproductive disorders.
• Studies show that the perineum is twice
as long in males as in females.

5. Areas of the perineum /Structures in the
perineum
• The region of the perineum can be considered a
distinct area from pelvic cavity, with the two
regions separated by the pelvic diaphragm.
The following areas are thus classified as parts of
the perineal region
• perineal pouches: superficial and deep
• External genitalia.
• Anal canal and anal sphincters
• Pudendal canal
• Ischiorectal /and ischioanal fossa.

6. perineum

7. boundaries
Its deep boundaries are as follows:
• in front: the pubic arch and the
arcuate ligament of the pubis
• behind: the tip of the coccyx
• on either side: the inferior rami of the pubis
and Ischium and the sacrotuberous ligament .
• Or anterolaterally - inferior pubic ramus,
ischial ramus and ischial tuberosity;
• And posterolaterally - sacrotuberous ligament.

8. Perineal-Triangles
• The perineum is subdivided into 2
trianglular-spaces by an imaginary line
connecting the ischial tuberosities/
• A line drawn transversely across in front
of the ischial tuberosities and include the:
• the anal triangle
• and urogenital

9. urogenital triangle
• Is the anterior subdivision of the diamond-
shaped perineum;
• its boundaries are: anterolaterally - inferior
pubic ramus, ischial ramus;
• posteriorly - posterior margin of perineal
membrane (corresponds to an imaginary line
connecting the ischial tuberosities)

10. Urogenital triangle
• is the location of the terminal portion
of the urinary tract and genital tract,
o Anterior aspect (apex of triangle):
pubic symphysis
o Lateral aspects: Ischial tuberosities
• Posterior aspect: tip of coccyx bone.

11. UG-triangle

12. Anal triangle
• Is the posterior subdivision of the
diamond-shaped perineum/anal triangle is the
location of the terminal end of the gastrointestinal
tract (anus)
• its boundaries are:
• anteriorly - posterior margin of the perineal
membrane (corresponds to an imaginary line
connecting the ischial tuberosities);

13. • posterolaterally - sacrotuberous ligament
o Apex of anal triangle = the tip of the coccyx
bone.
o Sides of anal triangle = the sacrotuberous
ligaments and the gluteus maximus.
o Base of anal triangle = the ischial
tuberosities

14. • Boundaries between the triangles: A line
going from one ischial tuberosity to the
other one defines the border between the
two perineal triangles.
• The perineal body is in the middle of that
line.
o The line also marks the inferior border of
the urogenital diaphragm.
o NB: Superficial Transverse Perineal Muscle
goes between the anal and UG triangles, and
converges on the perineal body.

15. Name Location Contents
Urogenital
triangle
the anterior
triangle
in females, contains the
vagina
Anal triangle
the posterior
triangle
contains the anus

16. Perineal fascia
• Introduction:
• The terminology of the perineal
fascia can be confusing, and there is
some controversy over the
nomenclature.
• This stems from the fact that there
are two parts to the fascia, the
superficial and deep parts,
• and each of these can be subdivided
into superficial and deep parts.

17. • The layers and contents are as follows, from
superficial to deep:
• 1) Skin
• 2) superficial perineal fascia: Subcutaneous
tissue divided into two layers: (a) A superfi-
cial fatty layer and (b) Colles' fascia- a
deeper, membranous layer.
• 3) deep perineal fascia and muscles:
• 4) fascia and muscles of pelvic floor (levator
ani, coccygeus)
• 4) fascia and muscles of pelvic floor (levator
ani, coccygeus)

18. superficial
perineal pouch
Contains superficial perineal muscles:
transversus perinei superficialis,
bulbospongiosus, ischiocavernosus
inferior fascia of
urogenital
dia-phragm, or
perineal mem-brane
A membranous layer of the deep fascia.
deep perineal
pouch
Contains the deep perineal muscles: transversus
perinei profundus, sphincter urethrae
membranaceae
superior fascia of the
urogenital
diaphragm
Considered hypothetical by some modern
anatomists, but still commonly used to
logically divide the contents of the region.

19. Ischioanal Fossae:
• The potential spaces surrounding the anal
canal, in the anal triangle region, located
between the skin of the anal region and the
pelvic diaphragm.
• The ischioanal fossa (formerly called
ischiorectal fossa) is somewhat prismatic in
shape, with its base directed to the surface
of the perineum, and its apex at the line of
meeting of the obturator and anal fasciae
• The spaces are triangle-shaped.

21. Borders:
• The apex forms superiorly at the lateral border of the
levator ani muscles, where they connect to the obturator
membrane.
o The lateral aspect of the fossae are the obturator
internus muscles.
o The base of each fossa (triangular base) is the perianal
skin.
o The medial aspect of each fossa is the anal canal.
o The posterior aspect of each fossa is the sacrotuberous
ligament and gluteus maximus muscle.
• NB:As you go more anteriorly, the region of the ischioanal
fossae becomes thinner, until it converges on the bladder
anteriorly. There is very little of the anterior recess left,
right next to the pubic symphysis most anteriorly.

22. • Boundaries
• ANTERIOR
* fascia of Colles covering the Transversus perinei
superficialis
* inferior fascia of the urogenital diaphragm
• POSTERIOR
* Gluteus maximus
* sacrotuberous ligament
• LATERAL
* tuberosity of the ischium
* Obturator internus muscle
* obturator fascia
• MEDIAL:
* Levator ani
* Sphincter ani externus
* anal fascia
• SUPERIOR:
* Levator ani

23. Recess of the Ischioanal Fossae
• Anterior Recess of the Ischioanal Fossae is
formed by the reflection of the fossa, anteriorly,
with the urogenital diaphragm.
o This recess is between the pelvic diaphragm
(superior border) and UG diaphragm (inferior
border).

24. o NB: If an abscess were to get into the
anterior recess, the fluid would be superior
to the UG diaphragm and inferior to the
pelvic diaphragm.
• Posterior Recess of the Ischioanal Fossae
is just superior to the sacrotuberous
ligament, where it reflects on the posterior
part of the pelvic diaphragm.
o This is inferior to the pelvic diaphragm.

25. Contents of Ischioanal Fossae:
• Fat! -- which allows the expansion of the anal canal and
therefore the passage of stored feces.
• The contents include:
• Inside Alcock's canal, on the lateral wall
o internal pudendal artery
o internal pudendal vein
o pudendal nerve
• Outside Alcock's canal, crossing the space transversely
o inferior rectal artery
o inferior rectal veins
o inferior anal nerves
• fatty tissue across which numerous fibrous bands extend

26. Pudendal canal

27. The pudendal canal
• also called Alcock's canal is an
anatomical structure in the pelvis
through which the
internal pudendal artery,
internal pudendal veins, and the
pudendal nerve pass.
• Structure
• The pudendal canal is formed by the
obturator internus fascia

28. • Contains pudendal artery, pudendal vein, and
pudendal nerve.
• It runs along the lateral wall of the ischioanal
fossae, just medial to the obturator internus
muscle.
• It runs along the medial surface of the ischial
tuberosity.
• It goes out at the greater sciatic foramen, then
runs laterally along the ischial spine and
sacrospinous ligament, and then comes back in
through the lesser sciatic foramen, and then runs
along the medial aspect of the ischiopubic ramus.
• Internal Pudendal Artery and Vein:
o A branch of the anterior division of the internal
iliac artery / vein.

29. • Pudendal Nerve:
o The only nerve innervating the perineal
region!
• Branches of the Pudendal Canal:
o Inferior Rectal Artery, Vein, and Nerve:
Goes to the rectal area.
o Perineal Artery, Vein, and Nerve: Goes to
the Urogenital area.
o Deep Dorsal Artery, Vein, and Nerve: Goes
to the shaft of the penis (clitoris).
o It travels along the superior aspect of the
UG diaphragm.

30. Urogenital Diaphragm:
• The part of the pelvic diaphragm that extends
medially, between the ischiopubic rami.
• Through and through, it is located inferior to the
pelvic diaphragm.
• Anteriorly, it encloses the sphincter urethrae
muscle.
• Posteriorly, it encloses the deep transverse
perianal muscle.
• Anteriorly, it encircles the urethra on either side.
The anterior recess of the anal fossae becomes
smaller and smaller as you move anteriorly.
• It encloses the Deep Perineal

31. • Pelvic Roof / Peritoneum: The pelvis roof is defined
by the inferior limit of peritoneum, coming down
from the abdomen.
• Peritoneum covers the anterior aspect of rectum,
then reflect off the uterus (in female), forming the
Rectouterine Pouch (of Douglas). That is the
inferior most peritoneal recess of the abdomen.
o Male analogous structure is rectovesical recess,
reflection between the rectum and seminal vesicles,
which are directly posterior to the bladder.
• The peritoneum then covers the uterus and uterine
tubes, before going back up the anterior abdominal
wall.
• Peritoneum does not cover all of the rectum.

32. • Central Tendon of the Perineum
(Male), or Perineal Body (female): The
junction of most of the musculature of
the pelvic diaphragm. It is the central
support for pelvic diaphragm, which in
turn supports the pelvis.
o If it is damaged, incontinence results.
o It is an attachment point for both the
perineum and the pelvis.

33. o Point where fibers from pelvis unite
with those of external anal sphincter.
o It is the posterior attachment point
of the urogenital diaphragm.
o Point where external genitalia
(corpora) muscles attach.
o Point where superficial transverse
perineal muscles attach