Gross anatomy of

the pelvis

Dr. K.A.A. Dilhari, Department of Basic Sciences,

FAHS, USJ
 At the end of the lecture, you should be able to

• Describe the boundaries of the bony pelvis and its

subdivisions
• Describe the boundaries of the true pelvis
• Describe the structure of the pelvic walls and pelvic
Objectives diaphragm
• Describe the general arrangement of the pelvic viscera,
vessels and nerves
• Describe the general arrangement of the contents of
the perineum
• Describe the clinical conditions related to the pelvis
 The pelvis

• Formed by the hip bones (2), the

sacrum and the coccyx

• Divided into upper and lower

parts by the brim of the pelvis
Function?
• It transmits the weight of the body from
the vertebral column to the femurs

• It supports and protects the pelvic

viscera

• It provides attachment for trunk and

lower limb muscles
 Hip bones

• Two hip bones articulate with

each other
Anteriorly: at symphysis pubis
Posteriorly: with the sacrum at
sacroiliac joints

• Forms a strong basin-shaped

structure
 • The greater/ false pelvis is above the brim
Subdivisions • The lesser/ true pelvis is below the brim
Greater/ false pelvis
• Bounded by
- lumber vertebrae (behind)
- iliac fossa and iliacus muscles (laterally)
- lower part of the anterior abdominal
wall (in front)

• Clinical importance:
- It supports the abdominal contents
- After the 3rd month of pregnancy, it
helps support the gravid uterus
- During early stage of labor, it helps
guide the fetus into the true pelvis
Lesser/ true pelvis
• True pelvis has
- an inlet
- an outlet
- a cavity

• Female true pelvis (Shape and

dimensions) has a greater
importance of the for obstetrics →
its bony canal through which the
baby passes during birth
 Pelvic inlet / Pelvic
brim

• Bounded by the
- sacral promontory (posteriorly)
- iliopectineal lines (laterally)
- symphysis pubis (anteriorly)
 Pelvic outlet

• Diamond shape
• Bounded by the
- coccyx (posteriorly)
- ischial tuberosities (laterally)
- pubic arch (anteriorly)

• Has 3 wide notches

- Pubic arch (anteriorly, between
ischiopubic rami)
- Sciatic notches (laterally)
 Pelvic cavity
• Extends from the lower end of the
abdominal cavity at the pelvic brim to pelvic
diaphragm
• Lies between pelvic inlet and pelvic outlet
• A short, curved canal
• More roomy
• First directed downwards and backwards,
and then, downwards and forwards
• Has unequal walls (a shallow anterior wall
and a much deeper posterior wall)
Pelvic cavity - Boundaries

• Superiorly – it is continuous with the abdominal

cavity
• Anteriorly – the pubic bones
• Posteriorly – the sacrum and coccyx
• Laterally – ilium, ischium, and pubis
• Inferiorly – the muscles of the pelvic floor
Differences of
the pelvis based
on Gender
• The shape of the female pelvis allows for the passage
of the baby during childbirth

In comparison with the male pelvis,

• the female pelvis has lighter bones, is more shallow
and rounded and is generally roomier
 Activity I
Differences of the pelvis according to the gender

Male pelvis Female pelvis

Pelvic diaphragm/ pelvic floor

• Formed by the lavatores ani

muscles and coccygeus
muscles and their covering
fasciae
• is between pelvis and
perineum
• Anteriorly it is incomplete to
allow passage of the urethra
(in males) and the vagina (in
females)
Perineum
• Refers to the area
between the anus and
external genitals
extending from either the
vaginal opening to the anus
(in females) or the scrotum
to the anus (in males)
 Passage of fetal head during
childbirth
• Cephalic presentation:
Head down is the best
position for the baby
inside the uterus at the
time of delivery
It makes easier and safer
to baby to pass through
the birth canal
Pelvic walls
• Formed by bones and
ligaments
• Partly lined with muscles,
covered with fascia and parietal
peritoneum
• Pelvis has
- Anterior pelvic wall
- Posterior pelvic wall
- Lateral pelvic wall
- Inferior pelvic wall / pelvic floor
Anterior pelvic
wall

• The shallowest wall

• Formed by the bodies
of the
- pubic bones
- pubic rami
- symphysis pubis
Posterior pelvic wall
• Extensive
• Formed by the
- sacrum
- coccyx
- piriforms muscles and
their covering of parietal
pelvic fascia
Lateral pelvic wall
• Formed by the
- part of the hip bone, below the pelvic inlet
- obturator membrane
- sacrotuberous ligament
- sacrospinous ligament
- obturator internus muscle
and its covering fascia
Inferior pelvic wall/ pelvic floor
• Supports the pelvic viscera
• Formed by the pelvic
diaphragm
• Stretches across the pelvis
• Divides it into the main
pelvic cavity above, which
contains the pelvic viscera,
and the perineum below
 Pelvic viscera/ Contents
The pelvic cavity contains the following structures:
• sigmoid colon, rectum and anus
• some loops of the small intestine
• urinary bladder, lower parts of the ureters and the urethra

• In the female, the organs of the reproductive system: the

uterus, uterine tubes, ovaries and vagina

• In the male, some of the organs of the reproductive system:

the prostate gland, seminal vesicles, spermatic cords, deferent
ducts (vas deferens), ejaculatory ducts and the urethra
(common to the reproductive and urinary systems)
Nerves of the pelvis
• Sacral plexus
- Formed by anterior rami of L4, L5 and S1, 2, 3, 4
- L4 and L5 join to form lumbosacral trunk

• Branches of the lumber plexus

- Lumbosacral trunk (L4,5)
- Obturator nerve (branch of L/ plexus L2,3,4)

• Autonomic nerves
- Pelvic part of the sympathetic trunk
- Pelvic splanchnic nerve
- Superior hypogastric plexus
- Inferior hypogastric plexus
Arteries of the pelvis
Branch of the
R/L Internal anterior/
LV
Iliac Artery posterior
divisions
R/L
Aorta Common
Iliac Artery

Thoracic Abdominal
Aorta Aorta
Anterior division
- Umbilical artery (artery to vas deferens (male), superior vesical artery)
- Obiturator artery
- Inferior vesical artery
- Middle rectal artery
- Internal pudendal artery
- Inferior gluteal artery
- Uterine artery (Female)
- Vaginal artery (Female)

Posterior Division
- Iliolumbar artery
- Lateral sacral artery
- Superior gluteal artery
Veins of the pelvis
• External iliac vein
• Internal iliac vein
• Median sacral veins
Lymphatics of the pelvis
• Lymph nodes and vessels are arranged in a chain along the main
blood vessels with which they are associated
• There are external iliac nodes, internal iliac nodes and common iliac
nodes
Perineum
• When seen below from the thighs abducted,
- the perineum is diamond shaped
- bounded anteriorly by the symphesis pubis
- Posteriorly by the tip of the coccyx
- Laterally by the ischial tuberosities

• By an imaginary line passing through two ischial

tuberosites, it is divided into:
- Anal triangle (posteriorly)
- Urogenital triangle (anteriorly)
 Anal triangle
• Bounded by
- tip of the coccyx (posteriorly)
- ischial tuberosity and
sacrotuberous ligament (laterally)
• Overlapped by the boarder of the
gluteus maximus muscle
• The anal canal lies in the midline
and on each side is the ischiorectal
fossa
 Urogenital triangle
• Bounded by
- the pubic arch (anteriorly)
- ischial tuberosity (laterally)
 Per vaginal examination
Per rectal examination
Caudal anesthesia
Clinical Pudendal nerve block
conditions and
Colostomy
procedures
Sigmoidoscopy
Hemorrhoids
Uterine prolapse
 Per vaginal examination

• PV examination
• Inserts 1/ 2 lubricated, gloved fingers of one
hand into the vagina and presses on the
lower abdomen with the other hand
Superiorly cervix is palpated
• Done to
- determine whether the cervix is
open/ closed
- determine the length of the cervix
 Per rectal examination

• To check for a prostate enlargement or prostate

cancer in men
• Look for the cause of symptoms such as rectal
bleeding (blood in the stool), abdominal or pelvic
pain, or a change in bowel habit
• Normal – a normal size for the age with a smooth
surface
 Caudal anesthesia
• Solutions of anesthetics may be injected into the sacral
canal through the sacral hiatus
• The solutions pass superiorly in the loose connective tissue
and bathe the spinal nerves as they emerge from the dural
sheath
• Caudal anesthesia is used in operations in the sacral region,
including anorectal surgery and culdoscopy
• Obstetricians use this method of nerve block to relieve the
pain during the first and second stages of labor
Its advantage is that, administered by this method, the
anesthetic does not affect the infant
 Pudendal nerve block • A common regional anesthesia
technique to provide perineal
anesthesia during obstetric
• The area anesthetized is the skin of the perineum
procedures, including vaginal birth
• Indications during the second stage of labor,
vaginal repairs, and anorectal
- Usually, the head is descending through the vulva
surgeries such as hemorrhoidectomies
- During the second stage of a difficult labor, when
the presenting part of the foetus
- Forceps delivery
- Episiotomy
may be necessary
Transvaginal Procedure
The bony landmark used is the ischial
spine
The index finger is inserted through the
vagina to palpate the ischial spine
The needle of the syringe is then
passed through the vaginal mucous
membrane toward the ischial spine
On passing through the sacrospinous
ligament, the anesthetic solution is
injected around the pudendal nerve
Colostomy
• Indications: Colorectal cancer, Inflammatory
Bowel Disease, Trauma, Congenital
Conditions in infants

• A significant portion of the colon will be

removed
• Then, an artificial opening is created in the
abdominal wall to bypass a diseased or
damaged part of the colon and digested
bowel contents is collected into an external
bag or pouch
• Used to relieve large-bowel obstructions
 Sigmoidoscopy
• A minimally invasive medical examination of
the large intestine with a fibre optic camera
• Provides a visual diagnosis of polyps,
tumors, ulcers, inflammation (redness and
swelling), hemorrhoids, etc
• A screening test for colon cancer and rectal
cancer
• Grants the opportunity for biopsy removal of
suspected lesions
• A sigmoidoscopy is performed using a thin,
flexible tube called a sigmoidoscope
Hemorrhoids
• Painful, dilated/ swollen
veins occurring in relation to
the anus
• Types: Internal and External
Uterine prolapse
• Downward displacement of the
uterus into the vaginal canal
• A condition that can happen as a
woman ages
• With multiple vaginal deliveries,
the muscles and ligaments around
the uterus can weaken
• When this support structure starts
to fail, uterus can sag out of
position
Summary
Thank you