Download obstetric anatomy midw 201

OBSTETRIC ANATOMY
MIDW 201
BY
ESTHER A. M. ANYIDOHO
17TH NOV., 2014
COURSE OBJECTIVES
By the end of the course students should be
able to:
1. Describe the female and male reproductive
systems
2. Describe the physiology of ovulation and
fertilization
3. Describe the placenta and its functions
4. Describe the various types of female pelvis
and their relationship in labour and delivery
THE FEMALE PELVIS
• Objectives: By the end of the session, students
should be able to:
a. List the parts of the female bony pelvis
b. Describe each component part of the bony
pelvis
c. List the types of the female bony pelvis
d. List 2 effects of each type of the female bony
pelvis on labour and delivery
Female Bony Pelvis cont’d
• General description:
 The bony pelvis is located between the trunk and
the lower limbs of the body.
 It articulates superiorly with the 5th Lumbar
vertebra
 It articulates inferiorly with the coccygeal
vertebrae which form part of it
 It articulates laterally with the left and right
femoral heads in a depression called the
Acetabulum
The Female Bony Pelvis cont’d
The anterior border is the Symphysis Pubis.
 Bones of the Bony Pelvis is made up of 4
bones:
1. The Sacrum
2. The Cocyx
3. Two Innominate bones
These bones together make the bony pelvis the
largest bone formation in the human body
The Female bony Pelvis cont’d
The Sacrum: It is made up of 5 fused vertebrae. It is
triangular in shape with the apex pointing
downwards.
It lies between the right and left innominate bones
It articulates with the 2 innominate bones
It has 4 pairs of foraminae (windows or holes).
These communicate with the sacral canal. The
foraminae serve as exit for nerves from the spinal
cord at the level, blood vessels and lymphatic
channels as well.
The Female Bony Pelvis cont’d
The Sacrum has a hollow which is the anterior
concave surface. The concavity of the hollow
increases the capacity of the pelvis.
It has a widened portion on each of the first sacral
vertebra which are referred to as alae
(wings).
The Promontory is the centre point of the upper
border of the first sacral vertebra. This protrudes
over the hollow with the fifth lumbar vertebra.
The Female bony Pelvis cont’d
• The Sacral canal runs longitudinally through the
sacrum and opens at the level of the fifth lumbar
vertebra. The spinal nerves fan out through the
canal at the level of the 2nd and 3rd sacral
vertebrae to form the Cauda equina
• Obstetric Importance:
Anaesthetic agent is introduced through the caudal
canal to relieve pain from uterine contractions
during labour. This causes temporal paralysis of
the nerves leading to the relief of the pains.
The Female Bony Pelvis cont’d
• The Cocyx (Tail): This is four tiny fused vertebrae.
It is also triangular in shape. The base articulates
superiorly with the inferior aspect of the 5th
sacral vertebra. It serves as an attachment for
muscles and ligaments.
• Obstetric importance:
In the female, during the second stage of labour,
the cocyx tips backwards to widen the exit of the
birth canal for the head of the baby to pass
through.
The Female Bony Pelvis cont’d
 The Innominate Bones: These bones form the
lateral aspects of the bony pelvis.
 Each bone developed from 3 primary centres
of ossification. This formed three bones thus –
Ilium, Ischium and Pubis.
 The 3 bones meet in cup-shaped depression
called Acetabulum
The Female Bony Pelvis cont’d
• The ILIUM is the biggest and the uppermost of
the innominate bones. The uppermost end is
called the Iliac crest which is easily palpable
(the waist) by the hands resting on the hips. It
has four projections, two anterior and two
posterior called spines.
• The ilium articulates anteriorly with the
antero-superior iliac spine and posteriolry,
with the postero-superior iliac spine.
The Female Bony Pelvis cont’d
• The Antero-inferior lies approximately 2.5cm
below the antero-superior iliac spine. The
postero-superior iliac spines are located in the
dimples at the lower back of the individual.
The postero-inferior iliac spines mark the
upper border of the Greater Sciatic Notch
through which the Sciatic Nerves pass.
• The ilium forms the upper two-fifth of the
Acetabulum.
The Female Bony Pelvis cont’d
• The inner concave surface is smooth and the
outer surface is rough for attachment of the
gluteal muscles forming the buttocks.
• The ISCHIUM is the lowest portion of the
innominate bone. It forms the lower two-fifth
of the acetabulum. It has two projections
called the Ischial spine and the Ischial
Tuberosity respectively. The Ischial spine
terminates into the Lesser Sciatic Notch.
The Female Bony Pelvis cont’d
• The Ischial Tuberosity is the thickened portion
of the Ischium on which the weight of the
body rests in a sitting position.
• The Ischial spine separates the Lesser Sciatic
Notch from the Greater Sciatic Notch.
• The PUBIS is the smallest bone of the
innominate bone. It forms the lowest one-fifth
of the Acetabulum.
The Female Bony Pelvis cont’d
• There are two Pubic bones which are united
anteriorly to form the a square-shaped pubic
bones. The two bones are fused together by a
pad of cartilage in the middle, called the
Symphysis Pubis.
• The Superior Pubic Ramus forms the upper
portion. It unites with the ilium to form the
Iliopectineal eminence.
The Female Bony Pelvis cont’d
• The right and left descending Rami form the
Pubic Arch. Its importance is during the birth
of the baby, it widens out.
• The Ischium and the Pubis surround a
foramen called the Obturator Foramen