The Pelvic Girdle Flashcards
What bones make up the bony pelvis (pelvic girdle)?
Sacrum, Coccyx, Right Hip Bone, and Left Hip Bone.
What are the primary functions of the bony pelvis?
- Transmits body weight from the vertebral column to the femur.
- Contains, protects, and supports pelvic organs (e.g., bladder, rectum, reproductive organs).
- Provides attachment points for lower limbs and trunk.
- Anchors the roots of the external genitalia.
What are the key joints of the pelvic girdle and their functions?
- Sacroiliac joint: Transfers weight from sacrum to hip bones.
- Lumbosacral joint: Connects the lumbar spine to the sacrum.
- Sacrococcygeal joint: Connects the sacrum and coccyx.
- Pubic symphysis: A secondary cartilaginous joint that can soften and stretch during pregnancy, causing pain.
What is the subpubic angle, and where is it located?
The subpubic angle is the angle between the two pubic arches (formed by the left and right ischiopubic rami).
What is the acetabulum, and at what age does it fully form?
The acetabulum is the socket in the hip bone where the femur head articulates. It is formed by the fusion of the ilium, ischium, and pubis, which occurs around 16–18 years old.
What are the main joints of the pelvic girdle?
Sacroiliac joint, Lumbosacral joint, Sacrococcygeal joint, Pubic symphysis.
What is the function of the sacroiliac joint?
It transfers weight from the sacrum to the hip bones.
What type of joint is the pubic symphysis, and what happens to it during pregnancy?
It is a secondary cartilaginous joint that can soften and stretch during pregnancy, potentially causing pain
At what age do the three hip bones fuse, and where?
They fuse at the acetabulum around 16-18 years old.
What three bones form each hip bone?
Ilium, Ischium, and Pubis
What is the acetabulum?
A concave surface formed by the fusion of the ilium, ischium, and pubis, where the femur articulates with the hip bone.
Name two anterior landmarks of the hip bone.
Anterior superior iliac spine and Anterior inferior iliac spine.
Name two posterior landmarks of the hip bone.
Posterior superior iliac spine and Posterior inferior iliac spine.
What is the ischial tuberosity?
A bony prominence on the ischium that supports body weight when sitting.
What is the function of the subpubic angle?
It is the angle between the two pubic arches (formed by the left and right ischiopubic rami) and is useful in determining the pelvic outlet.
What is the obturator foramen?
A large opening in the hip bone, bordered by the pubis and ischium, allowing nerves and blood vessels to pass through.
What is the iliac crest?
The superior border of the ilium, forming the prominent “hip” bone.
What are the greater and lesser sciatic notches?
Depressions in the posterior hip bone:
Greater sciatic notch allows passage for the sciatic nerve.
Lesser sciatic notch allows passage of structures from the pelvis to the gluteal region.
What is the pubic tubercle?
A prominent point on the superior pubic ramus, used as an attachment site for the inguinal ligament.
What is the function of the obturator membrane?
It covers most of the obturator foramen and reduces its size.
Where does the sacrotuberous ligament run?
It runs between the sacrum and the ischial tuberosity.
Where does the sacrospinous ligament run?
It runs between the ischial spine and the sacrum and coccyx.
What is the function of the sacroiliac ligament?
It is a weight-bearing ligament that stabilizes the sacrum to the ilium.
What is the greater sciatic foramen, and what is its function?
It is a route of communication between the pelvic cavity and the lower limb.
What is the function of the lesser sciatic foramen?
It provides a route of communication between the pelvic cavity and the perineum and gluteal region.
What is the obturator canal, and what structures pass through it?
It is a passage for the obturator nerve and vessels to supply the thigh.
What role does the obturator membrane play in the obturator foramen?
It reduces the size of the obturator foramen.
Where does the piriformis muscle pass through, and what is its function?
It passes out through the greater sciatic foramen and functions in stabilizing the hip and rotating the thigh laterally.
Describe the structure and function of the obturator internus muscle.
It is a fan-shaped muscle whose tendon turns 90 degrees as it passes out through the lesser sciatic foramen. It is covered in obturator fascia, which thickens to form the tendinous arch.
What structures pass through the obturator canal?
The obturator nerve and vessels, which supply the thigh.
In anatomical position, which two structures lie in the same vertical plane (pelvic cavity)?
The anterior superior iliac spine and the superior edge of the pubic symphysis.
What is the pelvic inlet?
The bony boundary through which an infant’s head passes during birth.
Which line demarcates the boundary of the pelvic inlet?
The Linea terminalis.
List the structures that form the Linea terminalis of the pelvic inlet.
Pubic symphysis
Pubic crest
Pectin pubis (ridge of the superior pubic ramus)
Arcuate line of the ilium
Margin of the ala of the sacrum
Sacral promontory
How does the pelvic inlet divide the pelvic girdle?
It divides it into the greater (false) pelvis superiorly and the lesser (true) pelvis inferiorly.
What is the function of the greater (false) pelvis?
It provides support for the abdominal organs and does not contain the pelvic organs.
What is the function of the greater (false) pelvis?
It provides support for the abdominal organs and does not contain the pelvic organs.
What is the function of the lesser (true) pelvis?
It contains and protects the pelvic organs, including the bladder, rectum, and reproductive organs.
Where is the greater (false) pelvis located?
Above the pelvic inlet
What anatomical structures bound the greater (false) pelvis?
Posteriorly: Lower L5 and S1 vertebrae
Laterally: Flared iliac fossae
Anteriorly: Lower part of the anterior abdominal wall
What structures does the greater (false) pelvis contain?
The sigmoid colon and loops of ileum.
How does the greater pelvis contribute to pregnancy and childbirth?
It helps to guide the fetus into the true pelvis during labor.
Where is the lesser (true) pelvis located?
Below the pelvic inlet and above the pelvic outlet.
What does the lesser (true) pelvis include?
It includes the true pelvic cavity and the deep parts of the perineum, separated by the pelvic floor.
What does the lesser (true) pelvis include?
It includes the true pelvic cavity and the deep parts of the perineum, separated by the pelvic floor.
What organs does the lesser (true) pelvis contain?
The pelvic organs, including the bladder, rectum, and reproductive organs.
Why are the shape and dimensions of the true pelvis important?
They are crucial for obstetricians to assess suitability for childbirth.
What is the shape of the pelvic outlet?
Diamond-shaped.
What structures form the anterior and posterior parts of the pelvic outlet?
Anteriorly: Bony structures.
Posteriorly: Ligamentous structures.
What encloses the pelvic outlet?
The pelvic floor.
Which terminal parts of the body pass through the pelvic outlet?
The terminal parts of the urinary tract, gastrointestinal tract, and the vagina (in females).
Which terminal parts of the body pass through the pelvic outlet?
The terminal parts of the urinary tract, gastrointestinal tract, and the vagina (in females).
What are the main borders of the pelvic outlet?
Anteriorly: Pubic arch.
Laterally: Ischial tuberosities and sacrotuberous ligaments.
Posteriorly: Tip of the coccyx.
How does the pelvic outlet differ between males and females?
Female: Wider and more oval to facilitate childbirth.
Male: Narrower and more heart-shaped.
How does the subpubic angle differ between males and females?
Female: Wider, typically >80 degrees.
Male: Narrower, typically 50-60 degrees.
Describe the position of the ischial tuberosities in females vs. males.
Female: Farther apart to increase pelvic outlet width.
Male: Closer together, resulting in a narrower outlet.
