Pelvis Lec -1-
It is the part which lies below the abdomen, it contains the pelvic viscera and
surrounded by the pelvic skeleton.
Pelvic skeleton include the two hip bones the sacrum and coccygx.
The hip bone consists of three bones the ilium, ischium and the pubis united to
gather at the acetabulum to form one bone that is the hip bone.
The two hip bones articulate at the pubic symphysis anteriorly and with the
sacrum at the sacroiliac joint posteriorly .
The line which extends from the pubic symphysis anteriorly to the pubic crest to
the pectineal line and to the arcuate line then to the promontory of the sacrum
posteriorly called the pelvic inlet.
Sacrotuberous and sacrospinous ligaments
These are the two ligaments which convert the greater and lesser sciatic notches
to foramens respectively.
Sacrotuberous ligament extends from the ischial tuberosity to the side of sacrum
and coccygx and to both posterior superior and inferior iliac spines.
Sacrospinous ligament extends from the ischial spine to the side of lower part of
sacrum and coccygx.
The pelvis is divided into two parts
The greater or false pelvis which lies above the pelvic inlet related to the
abdomen.
The lesser or true pelvis lies below the pelvic inlet and contains the pelvic viscera.
Differences between male and female pelvis
1- Female pelvis is broader than male pelvis.
2- Pelvic inlet in male is heart shape due to anterior bulging of the sacral
promontory while in female is circular or oval in shape.
3- Pelvic cavity is short in female and long in male.
4- The pubic arch in female is wide while in male is sharp angled.
5- The pelvic cavity in female is cylindrical while in male it become narrower
as it descend downward.
The pelvic outlet ( perineum )
The pelvic outlet is diamond in shape bounded:
Anteriorly pubic symphysis
Anterolaterally by ischiopubic ramus and ischial tuberosity.
Posteriorly sacrum and coccygx.
Posterolaterally sacrotuberous ligament.
The perineum is divided by transverse line extend between the tuberosity
of the two Ischia into:
Anterior urogenital triangle and posterior anal triangle.
The urogenital triangle closed by the urogenital diaphragm.
The anal triangle closed by elevator ani muscle.
Urogenital triangle
Boundaries of urogenital triangle
Anteriorly the inferior border of the symphysis pubis.
Laterally the ischiopubic ramus.
Posteriorly the imaginary line between the two ischial tuberosities.
The urogenital diaphragm
It consist of two layers:
1-The superior fascia of urogenital diaphragm which is the extension of the
membranous layer of abdominal fascia.
2-The inferior fascia of the urogenital diaphragm which is called the
perineal membrane. Which is a trianglar fibrous sheet fill the space
between the 2 ischiopubic rami. Its base pass through the central tendon
(perineal body).
The central tendon (perineal body) it is a fibrous tissue lies between the
anal canal and the bulb of the penis in male and vagina in female.
The perineum composed of two spaces superificial and deep perineal
spaces.
Superificial perineal space
Lies between the skin and superificial fascia and the inferior fascia of the
urogenital membrane (perineal membrane).
Contents in male:
1- The root of the penis which include the two crura of the penis
( corpus cavernosa) covered by ischiocavernosus muscle and the bulb of
the penis (corpus sponginosa) covered by bulbospongiosus muscle.
2- Superficial transverse perineal muscle.
3- Related vessels and nerves these are the perineal nerve and
posterior scrotal vessels and nerves.
Contents of superficial perineal space in female are:
1-The crura of the clitoris covered by the ischicavernosus muscles.
2-Bulb of the vestibule covered by bulbospongiosus muscles.
3-The great vestibular gland.
4-Superficial transverse perineal muscle.
5-Related vessels and nerves these are the perineal nerve and posterior
labial vessels and nerve.
The superficial perineal space in female contains two opening the
urethra and the vagina.
The deep perineal space
It lies between the superior and inferior fascia of the urogenital diaphragm.
It contains in male:
1- Membranous part of the urethra it is 1 cm long continuous superiorly with the
prostatic part of the urethra and inferiorly with spongy part of the urethra.
2- The sphincter urethrae muscle surrounding the urethra.
3- Bulbourethral gland which is a pea size gland embedded in the fibers of the
sphincter urethrae muscle and its duct opens in the spongy part of the urethra.
4- Deep transverse perineal muscle.
5- Internal pudendal vessels and dorsal nerves of penis or clitoris.
The pelvic diaphragm
It is the muscular floor of the pelvic cavity if separates the pelvic cavity above
from the perineum below. It consist of two muscles levator ani and coccygeus.
Levator ani muscle extends from the posterior aspect of the pubic bone and
across the tendinous arch of obturator internus muscle ( thickening of fascia of
the obturator internus muscle) and to the ischial spine.
It consists of three parts
Iliococcygeus, pubococcygeus and puborectalis muscles.
Nerve supply the perineal surface by the inferior rectal nerve and the pelvic
surface by the ventral rami of lower sacral and coccygeal nerves.
Action raise the pelvic diaphragm and compress abdominal viscera in forced
respiration, it also support prostate and posterior wall of the vagina.
Coccygeus muscles arise from the ischial spine and sacrospinous ligament to the
lateral margin of sacrum and coccygx.
Nerve supply by the lower sacral ventral rami.
Action it assist the sacrospinous ligament in supporting the pelvic contents.
Other muscles of the pelvis are:
Piriformis muscle
it is conical in shape originated from the pelvic surface of the sacrum then enters
the gluteal region through the greater sciatic foramen inserted into the tip of the
greater trochanter of the femur.
Nerve supply from the S1 and S2 ventral rami.
Action stabilize the hip joint
Obturator internus
This van shape muscle covers the sides of the lesser pelvis. It arises from
obturator membrane and margin of obturator foramen inserted into the medial
part of the greater trochanter .
Nerve supply from the sacral plexus.
Action it stabilize the hip joint and acts as a lateral rotator of the femur.
Anal triangle
Bounded by
Posteriorly the tip of coccygx.
Anteriorly the posterior margin of Urogenital diaphragm.
Posterolaterlly the sacrotuberous ligament.
Contents of the anal triangle are:
1- Anal canal with the external anal sphincter muscle which consists of three parts
subcutaneous, superficial and deep. It is voluntary muscle while the internal
sphincter muscle of the anal canal is involuntary muscle.
2- Ischiorectal fossa or ischioanal fossa.
The anal canal
It is the direct continuation of the ampullary portion of the rectum. it lies below
the pelvic diaphragm, it is about 2.5-3.5 cm long extends through the anal
triangle and ends in the anus.
The wall of anal canal is lined by mucous membrane in its upper third which
continuous with that lining the rectum, this part consists of 5-10 longitudinal
folds called the anal column these columns connected by transverse mucosal
folds called the anal valves. The line of the these valves called the pectinate line
which separates the upper third of the anal canal from the middle third which
lines by smooth skin. The lower third of the anal canal is lined with pigmented
skin which contains hair follicles and sebaceous glands.
Vessels of the anal canal
Through the inferior rectal artery which is a branch from the internal iliac artery.
The middle rectal artery assists in supply the upper part of the canal.
Nerve supply is autonomic.
The ischiorectal ( ischioanal fossa )
It is a wedge shape space lies on each side of anal canal it has
Base which is the skin and underlining fascia.
Apex extend deep under the pelvic diaphragm.
Lateral wall the fascia of obturator internus muscle and the ischial tuberosity.
Medial wall the pelvic diaphragm.
Contents of the fossa
1- Inferior rectal nerve and vessels.
2- Perineal branch of the S4 nerve.
3- Perineal and posterior scrotal branches of the pudendal nerve. They pass
through the pudendal canal within the lateral wall of the fossa.
The lesser pelvis ( true pelvis)
The cavity of the lesser pelvis lies between the pelvic inlet superiorly and
the pelvic outlet inferiorly.
Contents of the pelvic cavity:
1.Urinary bladder Boundaries of the pelvic cavity:
Superiorly pelvic inlet
Inferiorly pelvic outlet
Anteriorly the posterior surface of the body of the pubis and the symphysis pubis
Posteriorly ventral surface of the sacrum and coccyx
Laterally the inner surface of the ischium and pubis which surround the obturator
foramen , obturator membrane, obturator internus and piriformis muscles.
1- Urinary bladder.
2. Rectum
3. Male and female internal genital organs
4. Blood vessels and nerves
The peritoneum of the pelvis
The viscera of the pelvis partially covered by peritoneum and lie below it.
The peritoneum from the anterior abdominal wall reflects on to the superior
surface of the bladder and descends on its fundus, In male the peritoneum
posterior to the bladder curves on to the rectum forming the rectovesical pouch.
In female the peritoneum reflected from the posterior surface of the bladder on to
the vesical surface of the uterus extends to the vagina then reflected on to the
rectum forming two pouches ,uterovesical pouch between the bladder and the
uterus and rectouterine pouch between the uterus and the rectum. The two layers
of the peritoneum covering both surfaces of the uterus extend laterally to the
pelvic wall these double layers of peritoneum form the broad ligament of the
uterus.
The rectum
It begins at the level of S4 vertebra curving downward and forward in the concavity
of the sacrum and coccygx on to the pelvic diaphragm. its length is 12 cm lies
against the prostate in male and the vagina in female. It turns abruptly downward
and backward to pierce the pelvic diaphragm and continue as the anal canal. The
rectum dilated above the pelvic diaphragm forming the rectal ampulla.
The inner surface of the rectum contains three mucosal folds 8 cm from the anal
canal one anterior and two posterior to support the fecal mass.
Blood and nerve supply of the rectum
1- Superior rectal artery which is the direct continuation of the inferior mesenteric
artery.
2- Middle and inferior rectal arteries branches from the internal iliac artery.
Venous drainage of the rectum is through
1- Superior rectal vein drain to the inferior mesenteric vein and to the portal
circulation.
2- Middle and inferior rectal veins drain to the internal iliac vein then to the
inferior vena cava that is to the systemic circulation.
Nerve supply is autonomic innervations.
Lymphatic drainage of the rectum and anal canal
1- Lymphatic vessels through the superior rectal vessels to the inferior
mesenteric nodes.
2- Lymphatic vessels through the middle rectal vessels to the internal iliac
nodes.
3- Lymphatic vessels through the inferior rectal vessels to the internal iliac
nodes.
4- Some lymphatic vessels pass to the sacral nodes.
5- Lymphatic vessels from the terminal part of the anal canal pass to the
superificial inguinal nodes.
Urinary bladder
It is a hallow muscular organ serve as container to the urine it lies in the anterior
part of the pelvis occupy the space bounded by the symphysis pubis and the
diverging lateral wall of the pelvis.
Relations
Posteriorly urinary bladder in male related to seminal vesicle and ductus deferens
and to the rectum through the rectovesical pouch. In female it is related to the
uterus through uterovesical pouch.
The superior surface is flat when the bladder is empty and covered with
peritoneum.
Inferiorly in male the bladder rest on the prostate and in female it lies on the pelvic
diaphragm.
The inferolateral surface of the bladder is related to the lateral pelvic wall.
Parts of the bladder
The apex connected to the umbilicus by a fibrous band called the urachus which
forms the median umbilical fold.
The fundus or the base of the bladder which is the posteroinferior part of the
bladder related in male to the seminal vesicle and ductus deferens, the duct of
seminal vesicle united with the ductus deferens to form the ejaculatory duct,
The ureter enters the bladder 5-6 cm apart at the superolateral portion of the
fundus.
The interior of the bladder
The mucous membrane of the urinary bladder contains
1- Vesical trigon which is a small triangular area bounded by the opening of the
two ureters and the urethral opening.
2- Interureteric fold which is a fold of mucous membrane between the openings
of the two ureters.
3- The urethral orifice which opens into the prostate.
4- Uvula of the bladder it is an elevation of the mucous membrane behind the
urethral opening due to the presence of the middle lobe of prostate.
Blood supply of the bladder is through the superior and inferior vesical arteries
branches from the internal iliac artery.
Venous drainage through vesical plexus of veins which communicates with the
prostatic venous plexus then end as vesical vein which drain into the internal
iliac vein.
Lymphatic drainage
1- From the superior and inferolateral surface pass to the external iliac nodes.
2- From the posterior surface pass to both internal and external iliac nodes.
3- Some lymphatic vessels from the neck pass to the sacral nodes and to the
median common iliac nodes.
Nerve supply through the vesical plexus of nerves which is the continuation of the
inferior hypogastric plexus contains postganglionic sympathetic and preganglionic
parasympathetic fibers from the splanchnic nerve which join the hypogastric
plexus from the sacral nerves S2,S3,and S4.
The parasympathetic supply has an emptying reflex causes contraction of the
muscles of the bladder. The sympathetic supply reach the blood vessels and carry
the impulses of pain due to over distension.