Pelvic Floor, Pelvic Organs and Perineum Flashcards
Where is the Pelvic Cavity located?
- Lies below the level of the pelvic inlet at the pelvic brim
- Bounded inferiorly by the pelvic diaphragm/floor
- Located inferoposteriorly to the abdomen and it is continuous with the abdominal
Where is the false pelvis located?
Above the pelvic brim
Where is the true pelvis located?
Below the pelvic brim
Where is the perineum located?
• Located inferior and superficial to the pelvic diaphragm and is outside the true pelvis
What is Sexual Dimorphism in the Pelvis?
- Sexual dimorphism is a result of the adaption for childbirth in the female
- The heavier build and larger muscles in male’s results in more robust bony markings
Why are the Pelvic Diameters measured?
• Clinically the diameters of the lesser pelvis are measured to determine the capacity of the pelvis for childbirth
Sexual Dimorphism in the Pelvis: Comparison between Males and Females
o The pelvic inlet is oval in female and heart shaped in male
o The female pubic arch/subpubic angle is larger and wider
o The greater sciatic notch is wider in females
o The obturator foramen is oval or triangular in females and round in males
What is the Greater Sciatic Notch?
• Greater Sciatic Foramen without the ligaments
What are the Diameters of the Pelvis?
- AP Diameter (Anterior/Posterior)
- Oblique Diameter (Diagonal)
- Transverse Diameter (Horizontal)
Measurements of the AP Diameter (Anterior/Posterior)
o Brim is shortest in this diameter o Outlet of the pelvis is wider o Cavity is 12 cm o Brim is 11 cm o Outlet is 13 cm
Measurements of the Oblique Diameter (Diagonal)
o Cavity is 12 cm
o Brim is 12 cm
o Outlet is 12 cm
Measurements of the Transverse Diameter (Horizontal)
o Brim is longer in this diameter o Outlet is the narrowest o Cavity is 12 cm o Brim is 13 cm o Outlet is 11 cm
Importance of Shape in the Female Pelvis
• Shape is important for determining the suitability for childbirth
Main Female Pelvic Shapes
Gynecoid
Android
Platypelloid
Anthropoid
Gynecoid
Typical female shaped pelvis with an oval shaped inlet
Most suitable for childbirth (43%)
Android
A masculine pelvic shape with a heartshaped inlet, prominent ishcial spines and a narrower pelvic outlet (33%)
Platypelloid
Shortened in the anteroposterior dimension of the pelvic inlet and wider in the transverse dimension (2%)
Anthropoid
Oval shaped inlet with a greatly elongated anteroposterior dimension and a shortened transverse dimension
It possesses a larger outlet (24%)
Location of the Pelvic Wall
Posteriorly and laterally
Pelvic Wall muscles
o Piriformis x 2
o Obturator Internus x2
Pelvic Floor (pelvic Diaphragm) Location
Located centrally
Pelvic Floor muscles
o Levator ani and its three parts x2
o Coccygeus x2
Location and Formation of the Sacral Plexus
- Left and right is formed by the ventral rami of spinal nerves L4-S4
- Both lies on the pelvic surface of the piriformis muscle
Major periphreal nerves arising from the sacral plexus
o Sciatic nerve
o Pudenal Nerve
Sciatic Nerve
Largest nerve in the body
Follows the piriformis muscle through the greater sciatic foramen and innervates the leg (except the thigh, this is done by the femoral nerve)
Pudendal Nerve
Passes through the greater sciatic foramen but then re-enters through the lesser sciatic foramen and innervates the structures of the perineum
Lumbosacral Plexus
• The lumbar and sacral plexus combined
Male Pelvic Organs and Structures
- Peritoneal Cavity
- Pelvic Ureters (origin at the pelvic brim)
- Urinary bladder (holds about 500mL of urine)
- Ductus deferens
- Seminal Vesicles
- Prostate gland
- Rectum
- Sigmoid Colon
- Blood Vessels
- Lymphatics
Retrovesical Pouch
- Posterior recess between the urinary bladder and rectum
- The lowest point in the abdomen in males
- The location where fluid may pool when standing upright
Male Parietal Peritoneum
• Can be seen lining the superior surface of the urinary bladder
Location of the Prostate Gland
• Located medial to the Levator ani muscles, superior to the deep perineal pouch and inferior to the urinary bladder
5 surfaces of the prostate gland
o Base/Superior Surface
o Anterior Surface
o Inferoposterior Surface
o Two lateral surfaces