Ch17: Pelvic Girdle Flashcards
What four bones make up the pelvic girdle?
- Sacrum
- Coccyx
- 2 Innominate Bones
Innominate bones are also known as the…
Hip bones or os coxae
Each irregularly shaped innominate bone is composed of…
The ilium, the ischium, and the pubis, which are fused together into one bone.
The joints or articulations in the pelvic girdle include the…
Right and left sacroiliac joints posterolaterally, the symphysis pubis anteriorly, and the lumbosacral joint superiorly
Functions of the pelvic girdle (pelvis)
- Most important to movement and posture: supports the weight of the body through the vertebral column and passes that force on to the innominate bones via the sacrum.
- Receives the ground forces generated when the foot contacts the ground and transmits them upward toward the vertebral column.
- During walking, the pelvic girdle moves as a unit in all three planes, allowing relatively smooth motion.
- Supports and protects the pelvic viscera
- Provides attachment for muscles
- Makes up the bony portion of the birth canal in females.
Joints of the Pelvic Girdle
Lumbosacral, Sacroiliac, Symphysis Pubis
False Pelvis
(Aka the greater or major pelvis)
- The bony area between the iliac crests and superior to the pelvic inlet.
- There are no pelvic organs within the false pelvis.
Pelvic Inlet
Can be seen by drawing a line between the sacral promontory posteriorly and the superior border of the symphysis pubis anteriorly
True Pelvis
(aka lesser or minor pelvis)
- Lies between the pelvic inlet and the pelvic outlet.
- Makes up the pelvic cavity
- Contains portions of the gastrointestinal (GI) tract, the urinary tract, and some reproductive organs
- In females, it forms the birth canal.
Pelvic Outlet
Can be seen by drawing a line from the tip of the coccyx to the inferior surface of the pubic symphysis
Differences in the Male and Female Pelvis
- Superior opening into pelvic cavity is more oval in females and more heart-shaped in males
- Pelvic cavity is shorter and less funnel-shaped in females, and sacrum is shorter and less curved
- Iliac walls are not as vertical, and the acetabula (plural of acetabulum) and ischial tuberosities are farther apart in females (makes the area within the female pelvic cavity greater than the longer, funnel-shaped cavity of the male pelvis)
- Pelvic arch is wider and more rounded in females
Pelvic Inlet and Outlet
True and False Pelvis
The bony area between the pelvic inlet and outlet is called…
True Pelvis
The bony area above the pelvic inlet is called…
False Pelvis
Male vs. Female Pelvic Arch
female is bigger than male
Sacroiliac Joint
(aka SI joint)
- Synovial, nonaxial joint between the sacrum and the ilium.
- Describes as a plane joint, but its articular surfaces are very irregular.
- Irregularity helps to lock the two surfaces together.
Function of the Sacroiliac Joint
To transmit weight from the upper body through the vertebral column to the innominate bones
- Designed for great stability and has very little mobility
- Like other synovial joints, its articular surface is lined with hyaline cartilage.
- Synovial membrane lines the nonarticular portions of the joint. It has a fibrous capsule reinforced by ligaments.
Function of the Sacroiliac Joint
To transmit weight from the upper body through the vertebral column to the innominate bones
- Designed for great stability and has very little mobility
- Like other synovial joints, its articular surface is lined with hyaline cartilage.
- Synovial membrane lines the nonarticular portions of the joint. It has a fibrous capsule reinforced by ligaments.
SI Joint Motion
The actual type and amount of movement occurring at the SI joint is the subject of considerable controversy
-It is generally accepted that the motions that do occur at the SI joint are nutation and counternutation
Sacroiliac Joint Motions
Nutation and Countermutation
Nutation
(aka sacral flexion)
- Occurs when the base of the sacrum (on the superior end) moves anteriorly and inferiorly which causes the inferior portion of the sacrum and the coccyx to move posteriorly.
- Pelvic outlet becomes larger and can be visualized by drawing a line from the tip of the coccyx to the bottom surface of the pubic symphysis
Counternutation
(aka sacral extension)
- Base of the sacrum moves posteriorly and superiorly, causing the tip of the coccyx to move anteriorly
- Pelvic inlet becomes larger and can be visualized by drawing a line from the base of the sacrum across to the top of the symphysis pubis
How much motion occurs with nutation and countermutation?
Minimal (and it can occur only in conjunction with other joint motions)
Nutation occurs with…
Trunk flexion or hip extension