Anatomy of the Pelvis

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Questions and Answers

What percentage of the acetabulum is formed by the body of the ilium?

One-fifth

Two-fifths (correct)

Four-fifths

Three-fifths

What muscle arises from the upper two-thirds of the anterior iliac fossa?

Iliacus muscle (correct)

Obturator internus muscle

Gluteus maximus

Levator ani muscle

Which ligament is attached to the roughened iliac tuberosity?

Sacrospinous ligament

Sacroiliac ligaments (correct)

Obturator externus muscle

Sacrotuberous ligament

What lies above the conical ischial spine?

Greater sciatic notch Signup and view all the answers

What muscle is attached to the medial surface of the ischial spine?

Levator ani muscle Signup and view all the answers

What surface of the ilium has the iliac crest?

Gluteal surface Signup and view all the answers

What is the function of the sacrotuberous ligament?

Attaches to the hamstring muscles Signup and view all the answers

What is the name of the notch above the ischial spine?

Greater sciatic notch Signup and view all the answers

What is the shape of the brim of the male pelvis?

Heart-shaped Signup and view all the answers

What is the purpose of performing symphysiotomy?

To enlarge the birth canal for delivery Signup and view all the answers

What is the direction of the maximum diameter of the pelvic inlet in females?

Transverse Signup and view all the answers

What is the characteristic of the subpubic angle in males?

It is often less than 90 degrees Signup and view all the answers

What type of joint is the symphysis pubis?

Secondary cartilaginous joint Signup and view all the answers

What is the direction of the maximum diameter of the pelvic outlet in females?

Anteroposterior Signup and view all the answers

What is the characteristic of the ischiopubic ramus in males?

It is everted Signup and view all the answers

What is the posture of the pelvis when it lies obliquely?

Erect Signup and view all the answers

What is the primary function of the sacrospinous and sacrotuberous ligaments in the pelvis?

To resist the rotation of the sacrum forwards Signup and view all the answers

Which part of the pubic bone articulates with the apex of the sacrum?

Lateral end of the crest Signup and view all the answers

What is the purpose of introducing anaesthetic solutions into the sacral canal?

To numb the birth canal, pelvic floor, and perineum Signup and view all the answers

What is the site of fusion of the 2nd and 3rd sacral vertebrae?

Lateral mass of sacrum Signup and view all the answers

What is the sacrum formed of?

Five fused sacral vertebrae Signup and view all the answers

What nerve block is often used during labour to block the pain of an episiotomy?

Pudendal nerve block Signup and view all the answers

What is the function of the pectineal line?

It gives attachment to the inguinal ligament Signup and view all the answers

What is the sacral canal?

A canal that conveys the segmental nerves Signup and view all the answers

What is the function of the piriformis muscle relative to the sacrum?

It is not directly related to the sacrum Signup and view all the answers

What is the term for the opening at the lower end of the sacrum?

Sacral hiatus Signup and view all the answers

What is the function of the interosseous sacroiliac ligament?

It unites the auricular surfaces of the sacrum and ilium Signup and view all the answers

What is the promontory?

The anterior margin of the sacrum Signup and view all the answers

What is the function of the ventral sacroiliac ligament?

It unites the auricular surfaces of the sacrum and ilium Signup and view all the answers

What is the name of the joint formed between the sacrum and the ilium?

Sacroiliac joint Signup and view all the answers

What is the main purpose of measuring the pelvis in pregnant women?

To assess whether problems may occur in childbirth Signup and view all the answers

What is the shape of the pelvic brim in females?

Round or oval Signup and view all the answers

What is the posterior wall of the pelvic cavity?

Three times longer than its anterior wall Signup and view all the answers

What is the boundary of the pelvic outlet in females?

The lower border of the pubic symphysis and ischiopubic rami Signup and view all the answers

What is the significance of the lesser pelvis in obstetrics?

It forms the birth canal Signup and view all the answers

What is the common consequence of fractures of the pelvis?

Injuries to related soft tissues Signup and view all the answers

What is the function of the pelvic fascia?

To give attachment to the obturator internus Signup and view all the answers

What is the method used to measure the pelvis in pregnant women?

Ultrasound Signup and view all the answers

Study Notes

Pelvic Girdle

The pelvis is formed by the fusion of four bones: ilium, ischium, and pubis.
The ilium forms the upper two-fifths of the acetabulum and expands superiorly into a flattened plate, the ala.
The gluteal surface of the ilium gives attachment to the glutei muscles.
The medial surface of the ilium is divided into a posterior auricular surface and an anterior iliac fossa.
The ischium forms the lower two-fifths of the acetabulum and expands inferiorly to form the ischial tuberosity.
The ischial tuberosity gives attachment to the hamstring muscles and the sacrotuberous ligament.
The pubis forms the anterior part of the pelvis and articulates with the femur.

Sacrum

The sacrum is formed by the fusion of five sacral vertebrae.
The sacrum is triangular in shape with a base superiorly, an apex inferiorly, and a dorsal, pelvic, and two lateral surfaces.
The sacrum is divided into a median portion and a pair of lateral masses.
The pelvic and dorsal sacral foramina communicate with the central sacral canal and convey the sacral segmental nerves.

Joints and Ligaments of the Pelvic Girdle

The sacroiliac joint is a plane synovial joint between the irregular auricular surfaces of the sacrum and ilium.
The sacroiliac ligaments are very strong and unite the auricular surfaces of the sacrum and ilium.
The interosseous sacroiliac ligament is also very strong and unites the auricular surfaces of the sacrum and ilium.
The sacrospinous and sacrotuberous ligaments resist the rotation of the sacrum forwards.

Symphysis Pubis

The symphysis pubis is a secondary cartilaginous joint between the two pubic bones.
The articular surfaces are united by a fibrocartilaginous disc.
Little movement occurs except for a slight separation of the pubic bones in late pregnancy.

The Articulated Pelvis

The pelvis lies obliquely in the erect posture with the anterior superior iliac spines and pubic symphysis in the same vertical plane.
The pelvis is divided into greater and lesser parts by the pelvic brim.
The greater (false) pelvis is above the brim and bounds the lower abdominal cavity.
The lesser (true) pelvis lies below the brim and forms the birth canal.

Sex Differences

The male pelvis is rougher, thicker, and heavier than the female pelvis.
The male pelvis has a heart-shaped brim, whereas the female pelvis has a round or oval brim.
The male pelvis has a longer and narrower cavity than the female pelvis.
The male pelvis has a larger acetabulum and an everted ischiopubic ramus.

Pelvimetry

Obstetricians require measurements of the pregnant woman's pelvis to assess whether problems may occur in childbirth.
Pelvimetry is now achieved ultrasonically.

Fractures of the Pelvis

Fractures of the pelvis are commonly caused by crush injuries and frequently result in injuries to related soft tissues.
Bladder and urethral trauma are associated with fractures of the pubis and major vessel trauma with sacroiliac fractures and dislocation.

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Description

This quiz covers the structure and formation of the pelvis, including the ilium and ischium bones, and their roles in the acetabulum and muscle attachments.