Exam V: Pelvic Structures Flashcards Preview

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Flashcards in Exam V: Pelvic Structures Deck (37):

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


Pelvic Inlet and Outlet Components

Promontory: S1
Ala: wings of sacrum
Sacroiliac joint
Linea terminalis made of arcuate line, pectin pubis, and pubic crest
pubic symphysis

Pubic symphysis, pubic arches, ischial tuberosity, coccyx and sacrotuberous ligament


Pelvic Bone Components

1. Ilium
2. Ischium
3. 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



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


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



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:
1. above: superior gluteal nerves and vessels
2. 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):
1. Puborectalis- starts at pubic bone wrapping to rectum
2. Pubococcygeus: anococcygeal raphe
3. 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



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:
1. Peritoneum
2. Parietal Pelvic Peritoneum
3. Visceral Pelvic Peritoneum
4. 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

1. Mesometrium - the mesentery of the uterus; the largest portion of the broad ligament
2. Mesosalpinx - the mesentery of the Fallopian tube
3. Mesovarium - the mesentery of the ovaries.