Normal Pelvic Anatomy

What are the most posterior and inferior boundaries of the pelvis?

sacrum and coccyx

What are the innominate bones?

• hip bones

• ilium, ischium, & pubic symphysis

What is the linea terminalis?

imaginary line from pubic symphysis to sacral prominence (top of sacrum) that separates true and false pelvis

What is the true pelvis?

• deep and below the linea terminalis

• contains all of the structures seen on transvaginal imaging

  • bladder, small bowel, ascending & descending colon, rectum, uterus, ovaries, fallopian tubes, internal iliacs, and 5 muscles

What muscles are contained in the pelvic diaphragm?

levator ani and coccygeus

What is the function of the pelvic diaphragm muscles?

• hammock shaped and give support to pelvic organs

• weakened muscles lead to uterine prolapse

What is the location of the pelvic diaphragm muscles?

• level of vagina when scanning in transverse

• posterior to bladder, vagina, and rectum

What are the adnexal muscles?

• OPI muscles

• obturator internus, piriformis, iliopsoas

What is the location of the adnexal muscles?

• adjacent or lateral to bladder/ovaries/uterus

• obturator internus: lateral to bladder

• piriformis: posterolateral

• iliopsoas: anterolateral

What is the broad ligament?

double fold of peritoneum that extends from lateral sides of uterus to walls of pelvis and supports pelvic organs

What is the only ligament that can ever be visualized on sonography?

broad ligament

When can the broad ligament be visualized on sonography?

with pelvic ascites

What is the round ligament?

between folds of broad ligament and supports the fundus of the uterus superiorly

What is the cardinal ligament?

contains vasculature of the uterus

Where is the retropubic space/space of Retzius?

anterior to bladder

Where is the anterior CDS/vesicouterine pouch?

between the bladder and uterus (anterior to uterus)

Where is the posterior CDS/rectouterine pouch/pouch of Douglas?

between the uterus and rectum (posterior to uterus)

What is the adnexa?

lower quadrants of abdomen and lateral spaces to uterus that contain the ovaries

Where do the uterine arteries originate?

the internal iliac artery

What do the arcuate arteries supply?

periphery of myometrium

What do the radial arteries supply?

deeper into myometrium

What do the straight arteries supply?

basal layer of endometrium

What do the spiral arteries supply?

functional layer of endometrium

Where do the ovarian arteries originate?

aorta

What is another name for the ovarian arteries?

gonadal arteries

Where do ovaries receive their blood supply?

dual blood supply from ovarian artery and uterine artery

What do the uterine veins drain into?

internal iliac veins

Where does the right ovarian vein drain?

IVC

Where does the left ovarian vein drain?

left renal vein

What is the longest pelvic vessel?

left ovarian vein

Where is the uterus located?

• retroperitoneum

• anterior to rectum and posterior to bladder

What are the 4 divisions of the uterus?

• fundus

• corpus

• isthmus

• cervix

What is the fundus of the uterus?

most superior and widest part of uterus

Where do the fallopian tubes attach?

uterine cornu

What is the corpus of the uterus?

body, largest area of uterus

What is the isthmus of the uterus?

the lower uterine segment during pregnancy

What are the two parts of the cervix?

internal and external os

What surrounds the external os?

vaginal fornix—ring like pouch or recess

What are the three layers of the uterus?

• serosa/perimetrium

• myometrium

• endometrium

What is the serosa/perimetrium?

outermost/organ fascia of uterus

What is the myometrium?

muscular layer of uterus

What is the endometrium?

mucosal layer of uterus containing basal and functional layers

Which layer of the uterus sheds during menses?

functional layer

Describe the neonatal uterus:

• prominent uterus due to maternal hormone stimulation

• cervix enlarged with 2:1 ratio—>cervix double the size of the body

Describe the prepubertal uterus:

• tubular in shape

• body and cervix are same size

Describe the uterus during puberty/reproductive years:

• increased fundal diameter—>pear shaped

• 6-8 cm

Describe the uterus during menopause:

decreased uterine size (4-6cm)

What is an anteverted uterus?

body tilts forward, 90 degree angle with cx

What is an anteflexed uterus?

body tilts forward, comes in contact with cx (folds)

What is a retroflexed uterus?

body tilts back and comes in contact with back of cx (folds)

What is a retroverted uterus?

body tilts back without a bend

What are some alternative names for the fallopian tubes?

• oviducts

• uterine tubes

• salpinges

What is the size and location of the fallopian tubes?

7-12 cm extending from cornu within the broad ligaments to the adnexa

What is the function of the fallopian tubes?

• means of fertilization and transportation to uterus

• cilia inside move back and forth to aid in movement of fertilized ovum

When can the fallopian tubes be seen on ultrasound?

when pathology is present or when distended by fluid

What are the 5 segments of the fallopian tube?

• interstitial

• isthmus

• ampulla

• infundibulum

• fimbria

What is the interstitial segment of the fallopian tubes?

most proximal segment where tubes attach to uterus (at cornu)

What is the isthmus segment of the fallopian tubes?

the bridge that connects interstitial to ampulla

What is the ampulla of the fallopian tubes?

longest and most tortuous part

Where is the most common location of fertilization and ectopics?

ampulla of the fallopian tubes

What is the infundibulum of the fallopian tubes?

the distal and widest portion

What are fimbria?

fingerlike extensions of infundibulum that draw unfertilized egg into tube

What is the ovarian ligament?

supports ovary from lateral side of uterus to ovary

What is the suspensory ligament?

supports ovaries from lateral pelvic side walls

What hormones do the ovaries produce?

estrogen and progesterone

What hormones stimulate the ovaries?

FSH and LH

What is the outer cortex of the ovary?

site of oogenesis/follicles

What is the medulla of the ovaries?

contains the vasculature and lymphatics

What is the Graafian follicle?

dominant follicle that ovulates

What is the cumulus oophorus?

where the egg is inside the dominant follicle

What is the corpus luteum?

replaces Graafian follicle after ovulation

What is the corpus albicans?

replaces corpus luteum when it regresses