female pelvis

3. ⦿ The female pelvis because of its
characteristics, aids in child birth. The bony pelvis in
normal standing posture transmits the body weight of
head, trunk and the upper extremities to the lower
extremities. In female it is adapted for child bearing.
The obstetrical anatomy of a typical female pelvis is
best considered as one unit.

4. INTRODUCTION
 The pelvis is a basin like structure which connects
the spine to lower limbs.
 It is an important part of the skeletal system.
 It transmits the weight of the trunk to the legs.
 It takes the weight of the sitting body.
 It allows movements of walking and running.
 It protects the pelvic organs.
 In addition the female pelvis is adapted for
childbearing with an increased width and
rounded brim.

5. ⦿The primary function of the pelvic girdle is to allow
movement of the body, especially walking and running. It
permits the person to sit and kneel. The women pelvis is
adapted for child bearing, and because of its increased width
and rounded brim women are less speedy than men.
⦿The pelvis transmits the weight of the trunk to the legs,
acting as a bridge between the femur. This makes it necessary
for the sacro-iliac joint to the immensely strong and virtually
immobile. The pelvis also takes the weight of the sitting body
on to the ischial tuberosities.
⦿The pelvis affords protection to the pelvic organs and, to a
lesser extent, to the abdominal contents. The sacrum
transmits the cauda equina and distributes the nerves to the
various parts of the pelvis.

9. Pelvic bones
⦿There are four pelvic bones
◾ Two innominate( nameless) or hip bones
◾ One sacrum
◾ One coccyx

10. ⦿Innominate bones: each innominate bone is composed of
three parts
o Ilium
o Ischium
o Pubic bones
⦿The ilium- ilium is the larger flared out part. When the
hand is placed on the hip it rests on the iliac crest, which is
the upper border. At the front of the iliac crest can be felt a
bony prominence known as the anterior superior iliac
spine .
A short distance below it is the anterior inferior
iliac spine. There are two similar points at the other end of
the iliac crest, namely the posterior superior and the
posterior inferior iliac spines. The concave anterior surface
of the ilium is the iliac fossa.

12. ⦿ The ischium- ischium is the thick lower part. It
has a large prominence known as the ischium
tuberosity, on which the body rests when sitting.
Behind and a little above the tuberosity is an
inward projection, the ischial spine. in labour
the station of the fetal head is estimated in
relation to the ischial spines.

13. ⦿The pubic bone- this bone forms the
anterior part. It has a body and two oar like
projections, the superior ramus and the inferior
ramus. The two pubic bones meet at the
symphysis pubis and the two inferior rami from
the pubic arch, merging into a similar ramus and
the ischium. The space enclosed by the body of
the pubic bone, the rami and the ischium is called
the obturator foramen.

15. ⦿The innominate bone contains a deep cup to articulate with
the head of the femur. This is termed as Acetabulum . all
three parts of the bone contribute to the acetabulum in the
following proportions: 2/5th ilium, 2/5th ischium and 1/5th
pubic bone.
⦿On the lower border of the innominate bone are found two
curves. One extends from the posterior inferior iliac spine
up to the ischial spine and is called the greater sciatic notch.
It is wide and rounded. The other lies between the ischial
spine and the ischial tuberosity and is the lesser sciatic
notch.

16. ⦿ Sacrum: the sacrum is a wedge shaped bone
consisting of five fused vertebrae. The upper border of the
first sacral vertebra juts forward and id known as the sacral
promontory. The anterior surface of the sacrum is concave
and is referred to as the hollow of sacrum. Laterally the
sacrum extends into a wing or ala. Four pairs of holes or
foramina pierce the sacrum and through these, nerves
from the Cauda Equina emerge to supply the pelvic organs.
The posterior surface is roughened to receive attachments
of muscles.

17. ⦿Coccyx: the coccyx is a vestigial tail. It
consists of four fused vertebra forming a small
triangular bone. With its base uppermost
articulating with the lower end of
the sacrum. During labour it moves
backward, having more space for the
delivery of the fetus this is called nodding.

18. Pelvic joints
There are four pelvic joints
⦿ One symphysis pubis
⦿ Two sacroiliac joints
⦿ One sacro-coccygeal joint

19. ⦿The symphysis pubis is formed at the junction of the
two pubic bones, which are united by a pad of
cartilage.
⦿The sacroiliac joints – these are the strongest joints in
the body. They join the sacrum to the ilium and thus
connect the spine to the pelvis.
⦿The sacro coccygeal joint – this joint is formed where
the base of the coccyx articulate with the tip of the
sacrum.

20. ⦿ In the non-pregnant state there is very little movement in
these joints, but during pregnancy endocrine activity causes
the ligaments to soften, which allows the joints to give. This
may provide more room for the fetal head as it passes
through the pelvis. The symphysis pubis may separate
slightly in later pregnancy. If it widens appreciably, the
degree of movement permitted may give rise to pain on
walking.
⦿ The sacro-coccygeal joint permits coccyx to the
deflected backward during the birth of the head.

22. The sacrotuberous and sacrospinous ligaments complete the
greater and lesser sciatic foraminae

23. Pelvic ligaments
Each of the pelvic joints is held together by ligaments
⦿Interpubic ligaments at the symphysis pubis
⦿Sacro-iliac ligaments
⦿Sacro-coccygeal ligaments
⦿
There are two other ligaments important
in midwifery
⦿The sacro-tuberous ligament
⦿The sacro-spinous ligament

24. ⦿ The sacro-tuberous ligament runs from the
sacrum to the ischial tuberosity and the sacro-
spinous ligament from the sacrum to the ischial
spine. These two ligaments cross the sciatic notch
and from the posterior wall of the pelvic outlet.

25. STRUCTURE OF PELVIS
FALES PELVIS
TRUE PELVIS

26. The pelvis is broadly divided into true pelvis and false
pelvis.
⦿The false pelvis: is divided by the linea terminalis
into the false pelvis above this demarcation and the
true pelvis below it. The false pelvis is the portion
above the pelvic brim. It has no obstetric significance
relevant to the passage of the fetus through the
pelvis.
⦿ The true pelvis: the true pelvis constitutes the bony
passage through which the fetus must pass through to
be born vaginally. Therefore, its construction planes
and diameters are of utmost interest in obstetrics.

27. TRUE PELVIS
 The true pelvis is the bony canal through which
the fetus passes during birth.
 It has three parts-
BRIM CAVITY OUTLET

28. Boundaries of true pelvis;
The true pelvis has the following as its boundaries
⦿Superiorly it is bounded by the sacral promonitory, linea
terminalis and the upper margin of pubic bones.
⦿Inferiorly it is bounded by the inferior margins of the
ischial tuberosities and the tip of the coccyx.
⦿Laterally it has sacroiliac notches and ligaments, and
inner surface of ischial bones
⦿Anteriorly by the obturator foramina an dthe
posterior surface of the symphysis pubis, pubic
bones and the ascending rami of ischial bones.
⦿Posteriorly bounded by the anterior surface of
sacrum and coccyx.

29. ⦿ The true pelvis has three parts namely brim, a
cavity and an outlet
⦿ The brim or inlet – its boundaries are the sacral
promontory and wings of the sacrum behind the iliac
bones in the front. The shape of the pelvic inlet is
transversely oval, with a slight posterior indentation
caused by the sacral promontory.

30. THE PELVIC BRIM OR INLET
 It is formed by the sacrum posteriorly, the iliac
bones laterally and the pubic bones anterior.
 Shape: it is almost rounded with anterio
posterior diameter being the shortest.
 Its boundaries are the sacral promontory and
wings of the sacrum behind the iliac bones on
the sides and the pubic bones in front.

32. LANDMARKS OF THE
BRIM
 Sacral promontory
 Sacral ala or sacral
wing
 Sacroiliac joint
 Iliopectineal line
 Iliopubic eminence
 Pectineal line
 Pubic tubercle
 Pubic Crest
 Symphysis pubis

33. Land marks of the brim: the inlet has the landmarks, these
are the fixed anatomical points on the brim.
1. Sacral promontory
2. Sacral wing or sacral ala
3. Sacro-iliac joint
4. The ileo-pectineal line- the edge formed at the
inward aspect of the ilium
5. The ilio-pectineal eminence- a roughened area where
the superior ramus of the pubic bone meets the ilium
6. Superior ramus of the pubic bone
7. Upper inner border of the body of pubic bone.
8. Upper inner border of the symphysis pubis.

35. DIAMETERS OF THE BRIM
 Anterio posterior
 Transverse
 Oblique

36. ANTERIO POSTERIOR (11CM)
 it is a line from the sacral promontory to the upper
border of symphysis pubis. This diameter is of three
types-
 Diagonal conjugate- distance between lower border of
symphysis pubis to mid point on sacral promontory it is 12
cm.
 Obstetrical conjugate- it is distance between midpoint of
sacral promontory to prominent bony projection in mid line
of symphysis pubis. it measures 10 cm
 True conjugate - it extends from the sacral promontory to
the top of the symphysis pubis. Its normal measurement is
11 cm or more.

37. Transverse (13cm) –
it is the distance between the two farthest points
on the pelvic brim over the Iliopectineal lines.
Oblique (12cm) –
it starts from the sacroiliac joint to the
opposite iliopubic eminence.

39. ⦿The pelvic cavity
This extends from the pelvic brim to the pelvic outlet. It
forms the curve of Carus, which the fetus has to navigate
in order to be born and has no specific landmarks.
The pelvic outlet
This is either an ovoid or diamond-shaped space; its
perimeter is partially comprised of ligaments. The
landmarks of the pelvic outlet are as follows:
⦿_ Lower border of the symphysis pubis
⦿_ Pubic arch
⦿_ Ischial spines and ischial tuberosities
⦿_ Sacrotuberous and sacrospinous ligaments
⦿_ Lower aspect of the sacrum and the coccyx

40. THE PELVIC CAVITY
 The cavity extends from the brim above to the
outlet below.
 Shape: its shape is almost rounded. It consist of
-
 Anterior border: Symphysis pubis
 Posterior border: Sacral hollow
 Lateral border: Soft tissues
 All diameters- measure 12cms.

41. THE PELVIC OUTLET
ANATOMICAL OUTLET:
 It consists of the lower border of all bones and
Sacro tuberous ligament.
 It consists of lower border of symphysis pubis,
Sacro coccygeal joint and Sacro ischial spine.
 Shape: it is antero – posteriorly oval.

42. OBSTETRICAL OUTLET:
 This outlet has greater practical significance,
because it includes the narrow pelvic strait
through which the fetus must pass.
 It is otherwise known as bony outlet.
 Shape: it is diamond shaped.

43. DIAMETERS OF OUTLET:
 Antero-posterior diameter (13cm): it Extend
from lower border of symphysis pubis to the tip
of coccyx.
 Oblique diameter (12): it extend from Rt. & Lt.
Sacro spinous ligament to Obturator
foramen
 Transverse diameter (11cm): between the
ischial spines.

44. TYPES OF PELVIS
GYNAECOID ANTHROPOID ANDROID
PLATYPELLOID

45. 1.Gynaecoid pelvis: (50%)
 It is commonly known as the
female pelvis because that type
occurs most frequently in
women.
 Most suitable for childbirth.
 Wider brim.
 Ischial spines are blunt
 Sub pubic angle is 90º

46. 2.Anthropoid pelvis: (25%)
 It favors a posterior position of
the fetus.
 Oval in shape
 Transverse diameter is shorter
 Seen in tall women with
narrow shoulders

47. 3.Android pelvis: (20%)
 It is commonly known as
male pelvis because it occurs
more frequently in men.
 Heart shaped brim
 Anterior posterior diameter
is shorter
 Transverse diameter is
wider
 Childbirth is difficult

48. 4.Platypelloid (flat) pelvis:
(5%)
 This type of pelvis is rare.
 Kidney shaped brim
 Anterior posterior diameter is
smaller
 Transverse diameter is
wider
 Not conductive to vaginal
delivery

49. DEFORMITIES OF PELVIS
 Contracted pelvis
 Rachitic pelvis
 Asymmetrical pelvis
 Roberts pelvis
 Nageles pelvis
 Osteomalacis / maacosteon pelvis
 Assimilation pelvis
 Others- Kyphosis, scoliosis, spondylosisthesis

50. The diameters of the pelvis
The major obstetric interest in the female bony pelvis is that
it is not distensible, with only minor degrees of movement
being possible at the symphysis pubis and sacroiliac joints.
The various dimensions of the pelvis are therefore
particularly significant in the context of childbirth and the
successful passage of the fetus through the bony pelvic
structure. The most common type of female pelvis
(gynaecoid) is considered to be the optimal shape and size
for childbirth; this is providing the fetus isn’t above average
size and the pelvis isn’t smaller than average, or where
there is a combination of both factors.