The pelvic diaphragm divides the pelvic cavity into the main pelvic cavity and perineum below. The perineum is diamond shaped and bounded by the pubic symphysis, coccyx, and ischial tuberosities. The anal triangle in the posterior perineum contains the anus, anal canal, ano-coccygeal body, and ischio-rectal fossae. The anal canal has two halves with different epithelial linings and blood supply. It is surrounded by internal and external anal sphincters. The pudendal nerve supplies the anal region. Hemorrhoids and fistulae can develop from issues in the anal region.

1. Pelvic Diaphragm :
N.supply :perineal branch of
S4 N. and perineal branch of
pudendal N.
It is formed of levator ani
Ms.+ small coccygeus Ms. + their
covering fascia.
It is incomplete anteriorly to
allow passage of urethra in males
/and urethra & vagina in female.

2. The pelvic diaphragm : divides
the cavity of pelvis into main pelvic
cavity above & perineum below.
The perineum is diamond
shaped ,bounded anteriorly by
symphysis pubis …posteriorly by
coccyx … laterally by
ischial tuberosities.
Anal triangle : it is the posterior
division of perineum /bounded
posteriorly by tip of coccyx… and
on each side by ischial tuberosity
& sacrotuberous lig. overlapped by
lower border of gluteus
maximus.

3. Contents of Anal triangle :
 Anus.
 Lower part of Anal canal.(upper part lies in pelvis)
 Ano-coccygeal body (or raphe) :a fibrofatty mass that
extends from anus to tip of coccyx.
 Ischio-rectal fossa on each side.

4. Anus :
lies in midline.
The skin around anus and
over ischio-rectal fossa on
each side is supplied by
inferior rectal N. (somatic).
Lymph vessles of the
skin of anus drain into
medial group of superficial
inguinal L.N.

5. Anal Canal
It is about 1,5 in. long,
descending from rectal ampulla to
anus.
Posteriorly : anococcygeal
body, which is a mass of fibrous
tissue lying between anal canal &
coccyx.
Laterally : fat-filled ischiorectal
fossae.
Anteriorly :
-In male : perineal body,
urogenital diaphragm,
membranous part of urethra, and
bulb of penis.
-In female : perineal body,
urogenital diaphragm, and lower
part of vagina.

6. Structure of anal
canal
Mucous membrane of upper ½
is derived from hindgut entoderm.
It is lined by columnar epithelium.
It is thrown into vertical folds-anal
columns, which are joined together at their
lower end by semilunar folds called anal
valves.
Nerve supply : autonomic hypo-
gastric plexus (as rectal mucosa), sensitive
only to stretch.
Arterial supply : superior rectal artery
–of inferior mesenteric/ sup.rectal v., a
tributary of inf. Mesenteric and portal v.
Lymphatic drainage : along sup.
Rectal artery to pararectal nodes, then to
inferior mesenteric nodes.

7. Structure of anal canal Mucous membrane of lower ½
is derived from ectoderm of proctodeum.
It is lined by stratified squamous
epithelium, which gradually merges at anus
with perianal epidermis.
No anal columns.
Nerve supply : somatic inferior
rectal N., sensitive to pain, temperature,
touch and pressure.
Arterial supply : inferior rectal
artery –of internal pudendal /inf.rectal v.,
a tributary of int. pudendal v. and drains
to internal iliac v. (systemic venous
drainage)
Lymphatic drainage : to medial
group of superficial inguinal ligament.

8. Structure of anal canal
Pectinate line: it is the line of joining
between upper & lower halves of anal canal/
at the level of anal valves..
Muscle coat : as rectum- consists of
outer longitudinal & inner circular layer of
smooth muscle. The longitudinal muscle
descends between the internal & external anal
sphincters.
Anal sphincters :
1-Involuntary internal sphincter: is
formed by thickening of smooth circular L.of
muscular coat at upper end of anal canal.
2-Voluntary external sphincter:
a-Subcutaneous part : surrounds the
lower end of anal and has No bony attachment.
b-superficial part : attached to coccyx
behind and the perineal body in front.
c-deep part : encircle upper end of
anal canal and has no bony attachments.

9. Puborectalis muscle
It is fibres of the two levator ani
muscles, forming a sling around the
junction of rectum & anal canal.
It is attached in front to pubic bones.
At the junction of rectum & anal
canal, the internal sphincter, deep part
of external sphincter & puborectalis
muscles form a ring called anorectal
ring which can be felt on rectal
examination.
Involuntary internal sphincter
supplied by …by symp. Fs. .from
inferior hypogastric plexus.
Voluntary external sphincter… by
inferior rectal N. + perineal branch of
S4 N.

10. Ischiorectal Fossa :
Its base is the skin of
perineum.
Its medial wall is levator ani
& anal canal.
Its lateral wall is obturator
internus, covered with pelvic
fascia.
Contents :dense fat , pudendal
nerve & int.pudendal vessels inside
the pudendal canal on the lat.wall of
the fossa , inf. Rectal N.& vessels
cross fossa to reach anal canal.

11. Pudendal Nerve :
Branch of sacral plexus.
It leaves pelvis through
greater sciatic foramen ,
crossing back of
sacrospinous ligament, and
passes through lesser sciatic
foramen to enter perinum.
It passes in the pudendal
canal in ischiorectal fossa.

12. Branches of Pudendal Nerve :
Inf. rectal N… supplies
ext.anal sph., m.m.of lower
½ of anal canal & perianal
skin.
Perineal N… supplies
muscles of urogenital triangle
,and skin of scrotum (or
labia majora).
Dorsal N. of penis… to
penis (or clitoris).

13. Internal Pudendal Vessels :
 Internal pud.artery … branch of internal iliac
artery ,passes from gluteal region to pelvis through
G.S.foramen and enters perineum through lesser
sciatic foramen.
 Branches of int. pud.artery :1-inf. Rectal artery
supplies… lower ½ of anal canal. 2-branches to
penis (or labia majora & clitoris).
 Int. pud. Vein : drains into int. iliac vein.

14. Internal Hemorroids (piles) :
Are due to varicosities of
tributareis of superior rectal vein.
Hemorrhoid is a fold of m.m. &
submucosa containing a varicosed
tributary of sup. Rectal vein. (B)
It occurs in upper ½ of anal canal
where m.m. innervated by
autonomic N.S., so they are painless
and sensitive only to strech.
Position of varicosed tributaries
of the vein lie in anal columns at 3-
,7-,and 11-o’clock positions. (C)
A, normal tributary of superior rectal vein within
the anal column. B, varicosed tributary of
superior rectal vein forming internal homorroids.
C, positions of varicosed tributaries of the vein.

15. External Hemorroids :
Are varicosities of tributaries
of inf. Rectal vein.
They are covered by m.m of
lower ½ of anal canal or skin
& commonly associated with
internal hemorrhoids.
Innervated by inf. Rectal
nerves, so they are painful &
sensitive to pain,temp, touch &
pressure.
It is recognized as a small
acute tender swelling at the
anal margin.

16. Perianal Abscesses :
Produced by fecal trauma to
anal mucosa , or infection of
anal fissure (due to tearing of anal
valve), or infection of
anal mucosal gland.
Types :
1-Submucous abscess.
2-Subcutaneous(beneath perianal skin)
3-Ischiorectal abscess.
4-pelvirectal abscess (bet.ampulla of
rectum & upper surface of levator ani.
Ischiorectal abscess may involve the
opposite fossa by spread of infection
across midline behind anal canal.

17. Anal Fissure :
In chronic constipation … the anal
valves may be torn down to the anus
forming the fissure.
It is elongated linear ulcer which lies
most commonly in midline posteriorly.
It is a very painful condition
specially during defecation because the
fissure extends to the lower ectodermal
part of anal canal which is supplied by
somatic nerve (inf.rectal nerve).
Anal fissre is examined under local
anesthesia.

18. Anal Fistula : Due to inadequate treatment of
anal abscesses ,leading to fistula.
It opens between the anal canal
lumen., and skin close to anus.
If the abcess opens onto only one
surface, it is known as a sinus.
The most important part of
sphincteric mechanism of anal
canal is the anorectal ring ,it
consists of : 1-int. sphincter.
2-puborectalis part of levator ani.
3-deep part of ext.sph.
Damage to ano-rectal ring will
produce fecal incontinence.

19. Cancer and lymph drainage of lower
Anal Canal :
 Lower ½ of m.m.of anal canal is drained to
superficial inguinal L.N.
 Cancer of lower ½ of anal canal leads to
secondary deposits in inguinal L.N.

21. It is bounded
Anteriorly… by pubic arch.
Laterally … by ischial
tuberosities.
Posteriorly : transverse line
passing through the 2 ischial
tuberosities.
It lies in diamond -shaped
perineum.
Urogenital Triangle

22. Fascia of Urogenital Triangle :
Superficial fascia :
1- fatty layer (fascia of camper) : it is
continuous with fat of ischiorectal fossa
+ superficial fascia of thigh. In scrotum,
the fat is replaced by smooth muscle –
dartos muscle.
2- membranous layer (colles’fascia) :
it is attached posteriorly to posterior
end of urogenital diaphragm/laterally
to pubic arch/anteriorly, it is
continuous with : the fascia of scrotum
(or labia majora) , fascia of penis,
membranous layer of superficial fascia
of abdomen (Scapa’s fascia).

23. Urogenital Diaphragm It is a musculofascial diaphragm ,lies in
anterior part of perineum (in
urogenital triangle) , filling in the gap of
pubic arch.
 It is formed by sphincter urethrae &
deep transverse perineal Ms ,which are
enclosed between the superior fascial
layer & inferior fascial layer
(or perineal membrane).
 The closed space between superficial &
deep layers of fascia is known as Deep
perineal pouch.
 The opened space between the
urogenital diaphragm above/ and
membranous layer of superficial fascia
below is called – superficial perineal
pouch, which is anteriorly
communicates with the space between
superficial fascia of abdomen &
anterior abdominal Ms. Laterally, it is
closed by its attachment to pubic arch.

24. Contents of Male & Female
Urogenital triangle
 In Male :
1-Penis.
2-Scrotum.
 In Female :
1-External genitalia
(Clitoris).
2-Orificies of Urethra
and /Vagina.

25. The root of penis is formed of
3 masses of erectile tissue : the bulb
and right +left crura of penis.
The bulb lies in midline and is
attached to undersurface of urogenital
diaphragm. It is covered by
bulbospongiosus muscle. It is
continued forward into body of penis
forming the corpus spongiosum.
It is traversed by the urethra.
Each crus is attached to side of
pubic arch and covered by
ischiocavernosus muscle. The 2 curura
converge anteriorly into the body of
penis forming corpora cavernosa.
The body of penis, +glans penis,
containing the external urethral meatus.
Contents of Male
Urogenital Triangle

26. Male urethra :
Prostatic urethra : it is 1 ½ inch-
widest & it is the most dilatable part.
Membranous urethra : ½ inch long,
lies within the urogenital diaphragm
,surrounded by sphincter urethrae
muscle ,it is least dilatable part of
urethra
Penile urethra :6 inch long, enclosed
in the bulb, corpus spongiosum and
glans of penis.
-The part of urethra that lies in glans
penis is dilated to form fossa terminalis.
-The bulbourethral glands open into
penile urethra below urogenital
diaphragm.
-The external meatus is the narrowest

27. Blood supply/ Lymph drainage /innervation
of penis :
 Arteries : 1-Corpora cavernosa : by
deep artery of penis.
2-Corpus spongiosum : by artery of
bulb + dorsal artery of penis…..all of
these arteries are branches of internal
pudendal arteries.
 Veins : drain into internal pudendal
veins.
 Lymph drainage : skin : into
superficial inguinal L.Ns. / Deep
structures : into internal iliac L.Ns.
 Nerve supply : pudendal N. + pelvic
plexus.

28. Contents of Male
Urogenital Triangle
Scrotum & its wall :
1-skin.
2-superficial fascia : smooth
dartos muscle (replace fatty layer
of abdominal wall) + Colles’s
fascia (membranous layer of superficial
fascia). 3-
External spermatic fascia from
external oblique.
4-Cremasteric fascia from internal
oblique.
5-Internal spermatic fascia from
fascia transversalis.
6-Tunica vaginalis : is a closed sac
that covers anterior, lateral, and medial
surfaces of testis.

29. Blood supply/ Lymph drainage /innervation of
Scrotum
 Arteries : 1- external pudendal of femoral artery.
2- scrotal branches of internal pudendal arteries.
 Veins : as the arteries. drain into femoral or internal
pudendal vein.
 Lymph drainage : skin : into medial group of superficial
inguinal L.Ns. / Testis & epididymis :into Lumbar (para-
aortic) L.Ns.
 Nerve supply : 1-Anterior surface : by ilio-inguinal Ns.+
genital branch of genitofemoral N.
2-Posterior surface : by scrotal branches from perineal N.
+ perineal branch posterior cutaneous N. of the thigh.

30. Contents of female Urogenital Triangle
 External genitalia.
 Orifices of urethra & vagina.
 The vagina is directed upward
& backward.
 The cervix pierces its anterior wall.
 Its upper ½ lies above pelvic floor
within the main pelvis between U.B.
anteriorly & rectum posteriorly.
 Its lower ½ lies in perineum
between urethra anteriorly & anal
canal posteriorly.
 Supports of vagina :
1-upper 1/3 …levator ani,
transverse cervical ,pubocervical,
and sacrocervical lig. 2-middlle 1/3
…urogenital diaphragm.
3-lower 1/3 …perineal body.

31. Contents of Superficial Perineal Pouch
In male : Root of penis + its covering Ms. As
bulbospongiosus (covers bulb of penis
on each side) & ischiocavernosus
muscles (cover crus penis on each side).
Superficial transvrse perineal Ms
arise from ischial ramus and inserted
into perineal body… it fix perineal
body in the center of perineum.
All Ms. of pouch+ skin are Supplied
by perineal branch of pudendal N.
Perineal body : a small fibrous mass
lies at the center of posterior margin of
Urogenital diaphragm/. it gives attachment to : 1-ext.anal sphincter.
2-bulbospongiosus muscle. 3-superficial transverse perineal Ms.

32. Contents of Superficial Perineal
Pouch in Female : Bulbospongiosus muscle,
surrounds orifice of vagina and
covers vestibular bulbs.
Ischiocavernosus muscle,
covers crus of clitoris on each side.
Superficial transverse
perineal muscles.
Perineal body …. Lies
between vagina & anal canal.
Perineal branch of
pudendal N… suppling
muscles & skin (as in male).

33. Contents of Deep perineal Pouch in
male : Membranous urethra …lies in
urogenital diaphragm.
Sphincter urethrae muscle
circular & transverse Fs.,/supplied
by perineal branch of pudendal N.
Bulbourethral glands …ducts
pierce perineal membrane to enter
penile urethra.
Deep transverse perineal Ms.
One on each side, small muscle Lie
posterior to sphincter urethrae muscle.,
inserted into perineal body. It help fixation
of perineal body.
Internal pudendal vessels.
Dorsal N. of penis.
Coronal section of
pelvis

34. Contents of Deep Perineal Pouch In
Female :
Part of urethra .
Part of vagina.
Sphincter urethrae ,which
is pierced by urethra &
vagina.
Deep transverse perineal
Ms., as in male.
Internal pudendal
vessels.
Dosal N.of clitoris.
Coronal section of pelvis

35. Pudendal Nerve Block
Indication : during second stage of difficult
labor, using forceps delivery and episiotomt.
Area of anesthesia: is the skin of
perineum.
Transvaginal procedure :
-The bony landmark used is ischial spine by
passing the neddle through vaginal mucous m.
-On passing sacrospinous ligament, injection
of solution is performed around pudendal N.
Perineal procedure :
-The bony landmark is ischial tuberosity, by
palpating it subcutaneously at the buttock..
-The neddle is introduced into pudendal canal -
1 in. deep to ischial tuberosity, so local
anesthetic drug infiltrates around pudendal N.

36. Injury of perineum during childbirth
 The perineal body : is a fibromuscular mass lying
between bulb of penis & anal canal in male /and between lower
part of vagina & anal canal in female, supporting post. Vaginal
wall. It is fixed in position by insetion of perineal Ms. + levator
ani (anterior Fs.)./it is much larger in femal than in male.
 In most cases during childbirth , there is abrasion of post.
Vaginal wall /In spontaneous delivary of child, it results in a
severe tear of lower 1/3 of post. Vaginal wall, perineal body, and
overlying skin, so lacerations may extend into anal canal and
damage the external sphincter.
 Breech deliveries + forceps diliveries are usually preceded by an
episiotomy, through surgical incision in perineal skin in a
posterolateral direction to avoid the anal sphincters

38. Perineal membrane
(inferior fascia of
urogenital diaphragm) in
male is piersed by :
1-urethra.
2-internal pudendal artery.
3-dorsal N.of penis.
Perineal membrane in
female is pierced by :
1-urethra. 2- vagina.
3-internal pudendal artery.
4-dorsal N. of clitoris.

39. Clinical Notes :
 Injury to pelvic floor :during childbirth can result
in loss of support of pelvic viscera leading to
uterine & vaginal prolapse ,and alteration in
position of bladder neck & urethra leading to
stress incontinence.
 Visceral pelvic fascia and infection : the pelvic
fascia in the region of uterine cervix is referred
to as parametrium.it is a common site for spread
of acute infections from uterus & vagina ,so the
infection becomes chronic pelvic inflammatory
disease.