Pelvic anatomy - the Royal College of Obstetricians and

Anatomy of the female pelvis and vaginal birth

© Royal College of Obstetricians and Gynaecologists

Take a look at the bony pelvis you have been given.

View it from the front.

In the following slides, the bony landmarks will be described.



Innominate bone


Sacrum


Coccyx


Sacroiliac joint


Sacrococcygeal joint


Symphysis pubis


Ischial spine


Ileopectineal line


Obturator foramen


Pubic arch


Sacral promontory


Anterior foramina


Now look at the pelvis from one side.

In the following slides, more landmarks will be shown.

You will also see how the pelvis is orientated when a woman is standing up straight.


Anterior superior iliac spine

Symphysis pubis

Vertical plane


Ischium

Ileum

Pubis


Acetabulum

Obturator foramen


Look at the pelvis from the front again.

In the following slides, you will be shown a little more anatomy.

Look at the position of the sacrotuberous and sacrospinous ligaments.


Sacrotuberous ligament


Sacrospinous ligament


Look at the pelvis from behind.

Look at the position of the sacrotuberous and sacrospinous ligaments.

These delineate the greater and lesser sciatic foraminae.







Greater sciatic foramen

Lesser sciatic foramen


We are now going to add in some muscles.

You will see piriformis from front and back.

You will see obturator internus from the back.


Piriformis


Piriformis


Obturator internus


We are now going to add in blood vessels and nerves.





Common Iliac A

Internal Iliac A


External Iliac A


Common Iliac V

Internal Iliac V


The Lumbosacral Plexus


Sciatic nerve


Pudendal nerve


Obturator nerve


Look at the pelvis from the side.

We will look at the muscles and ligaments on the side wall of the pelvis.

You will see where the levator ani muscles originate.

You will also see the critical dimensions of the pelvis.







Obturator canal


Obturator internus

Muscle

Covered by

Fascia


Pudendal canal


Line of attachment of levator ani


Critical pelvic dimensions

Pelvic inlet



Pelvic midplane



Pelvic outlet


Pelvic inlet

Pelvic outlet

Pelvic cavity

Pubic arch

Female Male



Imagine a ‘coronal’ plane through the middle of the pelvis.

You will see the rectum coming through the pelvis.

You will see where the levator ani muscles originate.

You will see which structures form the pelvic diaphragm.


Iliac crest

Pelvic brim

Ischial tuberosity


Rectum


Obturator

Internus

With Fascia


Levator ani

Plus coccygeus

Makes

Pelvic diaphragm


There are some structures above the pelvic diaphragm.

There are some structures below the pelvic diaphragm.


Peritoneum


Subperitoneal space


Contains:

Pubocervical

Trans cervical

Sacrocervical

Ligaments


Perineum everything under pelvic diaphragm © Royal College of Obstetricians and Gynaecologists

Ischiorectal fossae


Now look at the pelvis from below.

Look at the layout of the bones and the ligaments.

They define the pelvic outlet.


Obturator membrane

Obturator canal


Pubic arch Symphysis pubis

Inferior pubic ramus

Ischial ramus



Ischial tuberosity

Sacrum / coccyx


Pelvic outlet


Urogenital triangle

Anal triangle


Keep looking at the pelvis from below.

Imagine the anatomy above the pelvic diaphragm.

The following slides show the structures encountered as you descend through the pelvis.


Bladder

Cervix

Rectum

Above the

Pelvic diaphragm


Pubocervical ligament

Above the

Pelvic diaphragm


Transverse cervical ligament

Above the

Pelvic diaphragm


Sacrocervical ligament

Above the

Pelvic diaphragm


Pelvic diaphragm

Levator ani:

Pubococcygeus

Iliococcygeus

Ischiococcygeus

Coccygeus



Imagine the anatomy as you descend below the pelvic diaphragm.

The following slides show the structures encountered as you continue to descend through the pelvis.


Urogenital diaphragm

Superior layer of fascia



Sphincter urethrae

Deep transverse peroneal muscles


Perineal membrane


Structures in

Superficial pouch

Clitoris & crus

Bulb of vestibule

Vestibular glands


Muscles in

Superficial pouch

Ischiocavernosus

Bulbospongiosus

Supl transverse peroneal muscles


Perineal body



You have now reached the most superficial level.


Labium majus

Labium minus


Mons pubis

Prepuce of clitoris

Vestibule vagina

Fourchette


Here is the female abdomen and pelvis viewed from one side.

The structures shown should now be familiar to you.



Peritoneum


Pubocervical ligament

Sacrocervical ligament


Pelvic diaphragm




Here is the rectum.

Look at its anatomical relations.


Perineal body

Rectum

Sacrum

Anococcygeal body


Puborectalis

Deep

Superficial

Subcutaneous


Take your fetal skull and view it from above.

Note the near central position of the anterior fontanelle.


coronal sutures frontal bones parietal eminence lambdoid sutures occiput anterior fontanelle saggital suture posterior fontanelle


The following slides will demonstrate the orientation of the fetal skull as it passes through the pelvis in normal labour.


passenger the head flexes as the uterus contracts the head descends and engages in the pelvis the leading part approaches the ischial spines


passenger the occiput starts to rotate anteriorly the occiput reaches the pelvic floor (levator ani)

internal rotation continues to achieve an occipito-anterior position


passenger the occiput clears the symphysis pubis the head extends to deliver


passenger the head sits on the maternal perineum


passenger the fetal head realigns itself with the fetal shoulders - restitution


passenger the shoulders contact the pelvic floor and rotate so that the bisacromial diameter lies in an anteroposterior orientation the head therefore continues to rotate - external rotation


Pelvic anatomy - the Royal College of Obstetricians and

Anatomy of the female pelvis and vaginal birth

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Pelvic anatomy - the Royal College of Obstetricians and

Anatomy of the female pelvis and vaginal birth

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