Exam V: Pelvic Structures Flashcards
Function, Contents, and Associated Structures of the Pelvis
Function: contains and supports the bladder, rectum, anal canal, and reproductive tracts, gateway to other areas of the body
Contents: bladder, prostate, uterus, uterine tubes, fallopian tubes, vas deferens, sigmoid colon, rectum, vagina, ovaries, seminal vesicle, ejaculatory duct, ureters, urethra
Related structures: external genitalia, scrotum, sacrum, pelvic bones
4 Parts of the Pelvis
The Pelvis is composed of 4 parts
os coxae x2/ innominate bones
sacrum
coccyx
Pelvic Inlet and Outlet Components
Inlet: Promontory: S1 Ala: wings of sacrum Sacroiliac joint Linea terminalis made of arcuate line, pectin pubis, and pubic crest pubic symphysis
Outlet:
Pubic symphysis, pubic arches, ischial tuberosity, coccyx and sacrotuberous ligament
Pelvic Bone Components
- Ilium
- Ischium
- Pubis
Pelvic Joints and Ligaments
Lumbosacral Joint – symphysis (secondary cartilaginous); intervertebral disc, iliolumbar ligament
*L5-S1 most frequent site of disc herniation
Two zygapophyseal (facet) joints (plane synovial)- between superior and inferior articular facets
Sacroiliac – compound joint, plane synovial & syndesmosis; anterior/posterior sacroiliac lig., sacrotuberous & sacrospinous ligaments
Sacrococcygeal – sacrococcygeal ligament
Pubic symphysis – secondary cartilaginous, superior/inferior pubic (arcuate) ligament
Obturator membrane within the obturator foramen
Histology of Pubic Symphysis
Composed of fibrocartilage covered in hyaline cartilage
Direction of Pubic Bones Within the Body
The pubic bones are directed inferiorly in anatomic position
The sacrotuberous and sacrospinous ligaments stabilize the sacrum and prevent upward tilting of the inferior sacrum
Maintain the posture of the pelvis when standing; limits upward tilting of sacrum
Ischial tuberosity to sacrum = sacrotuberous ligament
Sacrum to spinous process = sacrospinous ligament
L5 to S1 Forward Sliding
Area of most frequent slippage
Articular processes and liolumbar ligaments prevent it from forward slipping
Spondylolisthesis
Forward moving of vertebral body
L5 moving on top of S1 from fracture or too much pressure = Meyerding Grade 1
Scotty dog collar: pars interarticularis fracture
Difference Between Male and Female Pelvic Structure
Male pelvis is heart shaped and female are more circular
Males have narrower pelvic angle than female
Ischial spines are wider in females than in males
Greater sciatic notch is wider in females than in males
Conjugate Line Diameter
anterior/posterior diameter, superior border of pubic symphysis to middle of sacral promontory
True Conjugate Diameter
from back of pubic symphysis to promontory, slightly shorter than conjugate, narrowest region between pubic symphysis and promontory (inlet)
Diagonal Conjugate Diameter
from bottom of pubic symphysis to sacral promontory, the only diameter that can be measured per vaginam
Oblique Diameter
sacroiliac joint to the iliopubic eminence on the opposite side
Transverse Diameter
at inlet and outlet; outlet=between the ischial tuberosities
maximum diameter of inlet is transverse
AP Diameter of Outlet
Maximum diameter of outlet is AP diameter
between lower border of pubic symphysis and tip of coccyx
Changes During Pregnancy/Childbirth
Pubic symphysis has increased mobility near end of pregnancy
Ischial spines and linea termalis lines are both the narrowest parts of the pelvis, which need to be wide enough for the baby’s head or C section
Relaxin released when closer to childbirth to widen the muscles, ligaments, and bones of the pelvis
Pelvic Fractures
If you fracture one part of the pelvis, it will usually cause fractures in other places of the pelvis as well
This is like a pretzel, if you break the pretzel, it will cause other areas to be broken too
Open book fracture – fracture of pubic symphysis
Muscles of the Pelvic Wall
Obturator Internus
Piriformis
Obturator Internus
Origin: anterolateral wall of true pelvis (deep surface of the obturator membrane and surrounding bone)
Insertion: medial surface of greater trochanter of femur
Innervation: nerve to obturator internus L5-S1
Function: lateral rotation of the extended hip joint; abduction of flexed hip
Piriformis
Origin: anterior surface of sacrum between anterior sacral foramina
Insertion: medial side of superior border of greater trochanter of femur
Innervation: branches from S1-2
Function: lateral rotation of the extended hip joint; abduction of flexed hip
Obturator Canal
contains the obturator nerve and vessels
Greater Sciatic Foramen
connects the pelvis to lower limbs
Piriformis muscle pass through, which divides the greater sciatic into two parts:
- above: superior gluteal nerves and vessels
- below: inferior gluteal nerves and vessels, sciatic nerve, pudendal nerve, inferior pudendal vessels, posterior femoral cutaneous nerves, nerves to obturator internus, and quadratus femorus muscles
Lesser Sciatic Foramen
obturator internus passes through along with pudendal nerve and internal pudendal vessels that loop around from the greater sciatic foramen portion below the piriformis muscle
Pelvic Diaphragm
Levator ani + coccygeus muscles = diaphragm
Levator Ani Components
Made up of 3 parts (medial to lateral):
- Puborectalis- starts at pubic bone wrapping to rectum
- Pubococcygeus: anococcygeal raphe
- Iliococcygeus: meets at anococcygeal raphe as well
Levator Ani Origin
Origin: line around the pelvic wall beginning on the posterior aspect of the pubic bone and extending across the obturator internus muscle as a tendinous arch to the ischial spine
Levator Ani Insertion
Insertion: anterior part attached to the superior surface of the perineal membrane, the posterior part meets its partner on the other side at the perineal body around the anal canal along the ano-coccygeal ligament
Levator Ani Innervation
Innervation: branches direct from the anterior ramus of S4, and by the inferior rectal branch of the pudendal nerve S2-4
Levator Ani Function
Function: contributes to the formation of the pelvic floor, which supports the pelvic viscera; maintains the angle between the rectum and anal canal; reinforces the external anal sphincter and, in women, functions as a vaginal sphincter
Coccygeus
Origin: ischial spine and pelvic surface of the sacrospinous ligament
Insertion: lateral margin of coccyx and related border of sacrum
Innervation: braches from anterior rami of S3-4
Function: contributes to the formation of the pelvic floor, which supports the pelvic viscera; pulls coccyx forward after defecation
Puborectalis Function
Forms a sling around the terminal portion of the GI tract
Maintains perineal flexure
Relaxation leads to defecation
Anterior, Lateral, Posterior, and Pelvic Floor Components
Anterior wall: made of pubic bones with pubococcygeus and puborectalis attached to it
Lateral wall: obturator internus and piriformis
Posterior wall: coccygeus
Pelvic floor: puborectalis and pubococcygeus
Urogenital Diaphragm
Inferior to the pelvic diaphragm
Perineal membrane: inferior boundary of deep perineal pouch (UGD)
Deep perineal pouch = urogenital diaphragm
Pelvic Fascia
From outermost to innermost:
- Peritoneum
- Parietal Pelvic Peritoneum
- Visceral Pelvic Peritoneum
- Endopelvic Fascia
Thickened Pelvic Fascia
Pubovesical Ligament
Transverse Cervical
Uterosacral Ligament
* all support the viscera
Broad Ligament
Wide fold of peritoneum that connects the sides of the uterus to the walls and floor of the pelvis
Components:
- Mesometrium - the mesentery of the uterus; the largest portion of the broad ligament
- Mesosalpinx - the mesentery of the Fallopian tube
- Mesovarium - the mesentery of the ovaries.
