Pelvis Flashcards
Which 3 bones make up the pelvic girdle and what is its function
Right and left hip bones and the sacrum
Supports body weight by transferring it to the lower limbs.
Describe the different types of joints found in the pelvis
Joints: synovial sacro-iliac joints exist between the sacrum and hip bones; secondary cartilaginous joint exists at the pubic symphysis
Synovial joint here strange- as there is no movement
Where are the joints in the pelvis found
The sacrum articulates superiorly with the vertebral body of LV at the lumbosacral joint
The pelvic bones articulate posteriorly with sacrum at the sacro-iliac joints and with each other anteriorly at the pubic symphysis
Summarise the pelvic bones
comprised of the ilium (superior), pubis (anterior) and ischium (posterior), forming the acetabular fossa where the head of the femur articulates
What are the two regions of the pelvis
Superior region- upper part of the pelvic bones and lower lumbar vertebrae is the false pelvis (greater pelvis) and is generally considered part of the abdomen
The true pelvis (lesser pelvis) is related to the inferior parts of the pelvic bones, sacrum and coccyx, and has an inlet and an outlet
Describe the components of the pelvic bone at birth
The bones are connected by cartilage in the area of the acetabulum; later between 16-18 they fuse into a single bone
Describe the true pelvis
Cylindrical and has an inlet, a wall and an outlet
The inlet is open, whereas the pelvic floor closes the outlet and separates the pelvic cavity above, from the perineum below
Describe the function of the pelvic inlet
Circular opening between the abdomen and the pelvic cavity through which structures (nerves, blood vessels) traverse between the abdomen and the pelvis
Describe the formation of the pelvic inlet
it is completely surrounded by bones and joints
The promontory of the sacrum protrudes into an inlet, forming its posterior margin in the midline
On either side of the promontory- the margin is formed by the alae of the sacrum
The margin crosses the sacro-iliac joint and then continues along the linea terminalis ( consisting of the arcuate line, pectin pubis/pectineal line and the pubic crest)
Pubic crest is the anterior margin
What is the arcuate line
A ridge separating the upper and lower parts of the ilium.
Describe the pelvic outlet
Diamond shaped, with the anterior part defined by bone and the posterior part by ligaments
Midline anteriorly- pubic symphysis
Extending laterally and posteriorly, the boundary on each side is the inferior border of the body of the pubis, the inferior ramus of the pubis, the ramus of the ischium, and the ischial tuberosity
Together, these elements on both sides form the pubic arch
From the ischial tuberosities, the boundary continues posteriorly and medially along the sacrotuberous ligament on both sides of the coccyx
Describe the function of the pelvic outlet
Terminal parts of the urinary and G.I tracts and vagina pass through the pelvic outlet
The area enclosed by the boundaries of the pelvic outlet and below the pelvic floor is the perineum.
Summarise the pelvic cavity
The Iliac fossae form a shallow basin containing lower abdominal viscera
The axis of the pelvic cavity is antero- inferiorly inclined
Pelvic cavity is conical or cylindrical (birth canal)
Cavity is mainly lined by muscles and nerves
Describe the features of the pelvic cavity
Lined by peritoneum continues with the peritoneum of the abdominal cavity that drapes over the superior aspects of the pelvic viscera, but in most regions does not reach the pelvic floor
What is found in the pelvic cavity
The pelvic viscera are located in the midline of the pelvic cavity
Bladder is anterior and the rectum is posterior
In women, the uterus lies between the bladder and rectum
Other structures, such as vessels and nerves, lie deep in the peritoneum in association with the pelvic walls and on either side of the pelvic viscera.
Describe the axis of the pelvic cavity
angled at 45deg to that of the abdomen (antero-inferior)
Describe the orientation of the pelvic cavity
ASIS and pubic symphysis lie in the same vertical plane- consequently the pelvic inlet is angled at 50-60 degrees
anterior relative to the horizontal plane and the pelvic cavity projects posteriorly from the abdominal cavity
Meanwhile, the urogenital part of the pelvic outlet (the pubic arch) is orientated in a nearly horizontal plane, whereas the posterior part of the outlet is positioned more vertically
The urogenital triangle of the perineum therefore faces inferiorly, while the anal triangle faces more posteriorly
How can the pelvis be split into the abdominal and posterior part
Pelvic bone above the linea terminalis -represents the lateral wall of the false pelvis- which is part of the abdominal cavity
Pelvic bone below this line- represents the lateral wall of the true pelvis- which contains the pelvic cavity
Describe the structure of the pubis
Consists of a body and two arms (rami)
Body- joints with body of other pubic bone at the pubic symphysis. Has a rounded pubic crest on its superior surface- that ends laterally as the pubic tubercule
Superior pubic ramus- projects posterolaterally and joins with ilum and ischium at its base, which is positioned toward the acetabulum
Superior margin of this triangular surface is the pectineal line, anteriorly this line is continuous with the pubic crest- and it is marked on its inferior surface by the obturator groove
Inferior ramus- projects laterally and inferiorly to join with the ramus of the ischium
Describe the ischium
Large body projects superiorly to join with the ilium and the superior ramus of the pubis
a ramus projects anteriorly to join with the inferior ramus of the pubis
posterior margin of bone is marked by a prominent ischial spine that separates the lesser sciatic notch, below, from the grater sciatic notch above
Most prominent feature is the ischial tuberosity- on the psoteroinferior aspect of the bone- important for attachment of lower limb muscles when sitting.
What does the pelvic wall consist of
Sacrum, coccyx, pelvic bones inferior to the linea terminalis, two ligaments and two muscles