Flashcards in Repro 5.2 The Pelvis Deck (35)
What shape is the bony pelvis?
What structures make up the pelvis?
Inominate (hip) bones
Dense ligaments bind the bones to each other
What is the superior aperture?
The pelvic inlet
What is the inferior aperture?
The pelvuc outlet (narrower than the inlet)
What demarcates the pelvic inlet?
The broad wings of the iliac bones, the sacrum and the pubic symphysis
What demarcates the pelvic outlet?
Paired inferior rami
What is the position of the pelvis in the erect position?
Tilted so that the plane of its inlet is at an angle of 60 degrees to the horizontal
What is the greater pelvis?
The false pelvis - the space surrounded by the upper portion of the iliac bones and upper part of the sacrum posteriorly (actually the lower portion of the abdominal cavity)
What is the lesser pelvis?
The true pelvis - More deep than the false pelvis, surrounded by the obturator foramen and ischial spines and the lower portion of the sacrum (contains the true structures of the pelvis - internal genitalia and the bladder)
What are the important muscular diaphragms in the pelvis?
What do the pelvic and urogenital diaphragms do?
close off the pelvic outlet and form a barrier between the visceral contents of the pelvis and the exterior
What are the 2 main differences between male and female pelvises?
1. The heavier build and stronger muscles in the male account for the stronger bone structure and better-defined muscle markings
2. Comparatively wider and shallower pelvic cavity in the female is correlated with its specialisation to accommodate the passage of the infant's head
What other features distinguish the male and female pelves on plane x-rays?
The pelvic inlet is heart-shaped in the male and oval in the female
The subpubic angle (angle between the inferior pubic rami) is narrow in the male and wide in the female
The soft tissue shadow of the penis and scrotum can usually be seen when not shielded by a lead screen
What is the pelvic floor?
Muscular and fibrous tissue diaphragm that fills the lower part of the pelvic canal and closes the abdominal cavity. It defines the upper border of the perineum and supports the pelvic organs
What is the function of the pelvic floor?
Contributes to continence - sphincter mechanism directly and indirectly on vagina and rectum and can resist increases in intra-abdominal pressure associated with coughing, defecation, heavy lifting etc.
Contributes to childbirth and truncal stability
Retains uterus and bladder in correct position
What structures are in the pelvic floor?
Pelvic diaphragm consisting of the levitator any and coccyges and related fascial coverings
Superficial muscles and structures (anterior and posterior perineum)
Describe the levator ani.
Paired muscle forming 3 slings of muscle extending from the posterior aspect of the pubic bone, the fascia over the obturator interns and the ischial spine
Name the 3 slings of the levator ani.
Anterior fibres around prostate or vagina
Puborectalis - Intermediate fibres around rectum
Pubococcygeus -pubic bone to coccyx
Iliococygeus - Posterior fibres to anococcygeal body and coccyx
How might damage to the pelvic floor occur?
Consequence of child birth
What might be the result of damage to the pelvic floor?
May lead to urinary stress incontinence
Stretching of related nerves, muscles and ligaments
Stretch of pudendal nerve -> neuropraxia and muscle weakness
Organ prolapse due to ineffective muscles
Describe the anterior perineum.
AKA urogenital perineum
Urogenital diaphragm fills the gap of the pubic arch stretching between the converging ischiopubic rami. It is a triangular sandwich with striated muscle fibres between two layers of fascia:
Inferior or superficial fascia - thickened and known as the perineum membrane
It also contains the bulbourethral glands and is pierced by the urethra and vagina (through the urogenital hiatus)
What structures are in the perineum?
Transverse perineal muscles
What structures are below the perineal membrane in the male?
Superficial transverse perineal membrane
Superficial perineal pouch
What is the superficial perineal pouch?
The site of collection of urine if the urethra is ruptured below the perineal membrane
What is the most important structure in the perineal body?
A fibromuscular node at the junction of anterior and posterior perineum. It is the point of attachment of the anal sphincters, bulbospongiosus, superficial transverse muscles and fibres of levator ani.
What might happen as a result of damage to the perineal body?
weakness in the pelvic floor -> prolapse of vagina etc
How is damage to the perineal body avoided in childbirth?
Where is the posterior perineum?
aka anal perineum. Between the ischial tuberosities on each side and the coccyx (triangle)
What is in the posterior perineum?