Chapter 5 Female Pelvis

OBGYN LECTURE FALL 2026

Ultrasound

popular imaging modalities used to evaluate the female pelvis

• high resolution imaging

• non-ionizing radiation

Two Approaches for Pelvic Ultrasound

Transabdominal and transvaginal

Transabdominal pelvic imaging

provides global view of the pelvic anatomy and allows the sonographer to visualize the true and false pelvis

visualization of the anatomy and physiology of the urinary bladder

lower frequency setting are used

• increase depth, lower resolution

Full Bladder

Transvaginal Pelvic Imaging aka…

Endocavity, Endovaginal

Transvaginal Pelvic Imaging

High frequency

• increased resolution

• decreased depth

Female Pelvis 3 Functions

1.) Weight bearing bridge between spine and bones of lower extremities

2.) Directs pathway of fetal head during childbirth

3.) Protects reproductive and other pelvic organs

4 bones in Pelvis are,,,

The sacrum & coccyx (posterior)

Two large innominate bones (form the ilium, ischium, and pubic bone) (form the lateral and anterior walls of the pelvis)

Linea terminalis

Divides the pelvic cavity into 2 regions (false pelvis & true pelvis)

Greater Pelvis supports what…

Intestines

Lesser pelvis supports what

Bladder, uterus, ovaries, fallopian tubes, vagin(a)

rectus abdominis does what

forms most of the anterior body wall

extend from xiphoid to pubic symphysis

Psoas major muscle

originates from lower thoracic and lumbar vertebrae

courses laterally and anteriorly through the abdomen

Iliopsoas muscle (tendon)

combination of the medial aspect of the iliacus and psoas muscle below the iliac crest

inserts through the lesser trochanter of the femur

Iliacus muscle

arises at the iliac crest and extend inferiorly until is merges with the psoas major

forms lateral parts of the pelvic basin

false pelvis region

Obturator muscle

Triangular sheet of muscle anchored along the brim of the true pelvis

extends posteriorly and medially along the side wall of the true pelvis

can be mistaken for ovaries

Piriformis Muscle

locate deeply posterior in the true pelvis

starts from the sacrum and courses laterally to the greater trochanter of the femur

Coccygeus muscle (most posterior)

forms posterior pelvic floor

functions to support sacrum

not seen on ultrasound

found in true pelvis

Levator Ani Group (most anterior and middle)

Iliococcygeus

Pubococcygeus

Puborectalis

found in true pelvis

Pelvic diaphragm is made up of what?

Coccygeus muscle & Levator Ani group

Cardinal Ligament (suspensory ligament)

from the lateral aspect of the cervix

connects to uterus at the level of the cervix to the lateral pelvic wall (obturator internus muscle)

provides supports for the uterus and cervix

Uterosacral ligament (suspensory ligament)

posterior aspect of the uterus, near the cervix, to the anterior aspect of the sacrum

provide posterior support

Round ligament

anterior of the braod ligaments, inferior to the fallopian tubes

attaches to the uterine cornu to the anterior pelvic wall

most common complaint in pregnancy

Ovarian Ligament aka

utero-ovarian ligament

attaches the inferior ovary to the uterine cornu

can help find ovaries

Broad “ligament”

extend fromlateral side of uterus and attaches to lateral side of pelvic side wall

divides the true pelvis into anterior and posterior compartments

ovaries attach to the posterior aspect of the broad ligament

only seen when excessive free fluid (ascites) is present

Mesovarian ligament

attaches the ovary to the posterios layer of the braod ligament

Pelvic Organs

external genitalia

urinary bladder and urethra

vaginal canal, uterus, fallopian tubes

ovaries

colon & rectum

Urinary bladder location

Between the symphysis pubis and the vagina

Ureters insert where?

posteriorly & inferiorly

Vaginal canal

7-10cm of smooth muscle

extends from cervix to external genitalia

lies posterior to urinary bladder and anterior to rectum and anus

Vaginal fornices

upper portion of vagina surrounding the cervix creating gutters

Anterior fornix

surrounds the anterior aspect of the external cervix

smaller than posterior fornix

Posterior fornix

surrounds the posterior aspect of the external cervix

frequent site of vaginal fluid collections due to gravity dependence

Lateral fornices

surround the lateral aspect of the external cervix on either side

Space of Retzuis aka

Retropubic prevesical space

anterior to bladder

Anterior Cul-De-Sac aka

Vesicouterine space

posterior to bladder, anterior to uterus

Posterior Cul-De-Sac aka

Pouch of Douglas or Rectouterine space

most common site for peritoneal fluid

posterior to the uterus

Uterus

pear shaped organ located between the bladder and rectum

Segments of the uterus

Fundus

Body or Corpus

Isthmus

Cervix

Isthmus

marks the transition from the corpus to the cervix

most flexible portion of the uterus and grows the most at a rapid rate during pregnancy

Cervix

cylindrical projection into the vagina which provides an alkaline secretion that helps with sperm penetration

acts as a sphincter during pregnancy

Internal os

opening from the cervix into the uterus

external os

opening from the cervix into the vagina

Cervix has a what

internal and external os

Perimetrium

serous outermost layer of the uterus (not seen in ultrasound)

Myometrium

middle muscular layer of the uterus

appears relatively homogenous sonographically

endometrium

inner mucous membrane

consists of the deeper permanent basal layer and superficial functional layer

Functionalis

layer seens as hypechoic halo encompassing

Basalis layer

the thin surrounding hyperechoic outermost echo

Layers of the Uterus in Order

Perimetrium

Myometrium

Basalis

Functionalis

(Papa, Mama, Baby, fetus)

Uterine Size on Age and Parity (2-8yrs)

Length: 3.3 cm

AP: 0.8cm

Uterine Size on Age and Parity (9-Menarche)

Length: 4.3cm

AP: 1.3cm

Uterine Size on Age and Parity (nulliparous)

Length: 8cm

AP: 3.0cm

Uterine Size on Age and Parity (multiparous)

Length:9cm

AP: 4cm

Uterine Size on Age and Parity (Postmenopausal)

varies based on parity and years since menopause

Newborn Uterus size and Cervical Length

2/3 cervix

1/3 body and fundus

Normal adult proportions

1/3 cervix

2/3 body and fundus

Variant positions of the Uterus

Anteflexed

Anteverted

Retroflexed

Retroverted

flexion

refers to axis of uterine body compared to cervix

version

refers to axis of cervix compared to vagin(a)

Anteflexion

bending of the fundus toward the abdominal wall

anteverted

tipping the entire uterus towards the anterior

anteflexed

bending of the fundus towards the anterior

retroflexed

bending of the fundus towards the posterior

retroverted

tipping of the entire uterus towards the posterior

internal illiac arteries aka

hypogastric artery

internal iliac artery

dives deep into the pelvis and divide into anterior and posterior trunks

Anterior branch gives rise to

vaginal arteries

uterine arteries

Uterine vasculature

Uterine

Arcuate

Radial

Spiral

U Are Really Smart

Fallopian Tubes aka

oviducts or salpinges

Fallopian Tubes

tubes that extend from the fundal portion of the uterus and open to the peritoneal cavity at the lateral end

trasnports the fertilized ovum to the uterus by peristalic contractions

length: 7-14cm