Normal Anatomy and Physiology of the Female Pelvis (Ch. 41)

how many bones are in the bony pelvis?

4 bones

what are the bones in the bony pelvis?

• sacrum

• coccyx

• innominate bones (2)

sacrum

forms part of posterior margin

coccyx

forms part of posterior margin

innominate bones

• aka hip bones (consists of ilium, ischium, and pubis)

• forms anterior/lateral margin

what are the 2 regions of the pelvis?

1. greater/false pelvis

2. lesser/true pelvis

false pelvis

• aka greater pelvis

• above linea terminalis

• contains mostly bowel

• “bound posteriorly by the lumbar vertebrae, supported and bound laterally by the iliac fossae and iliacus muscles, and anteriorly by the lower anterior abdominal wall”

• “portion of pelvis found above the brim”

true pelvis

• aka lesser pelvis

• below linea terminalis

• contains uterus, ovaries, and adnexa

• “pelvic cavity found below the brim”

muscles of the false and true pelvis

• false pelvis

  • rectus abdominis

  • psoas major

  • iliopsoas

  • iliacus

• true pelvis

  • piriformis

  • obturator internus

  • levator ani and coccygeus (pelvic floor muscles)

what are the 4 false (greater) pelvis muscles?

• rectus abdominis

• psoas major

• iliopsoas

• iliacus

what are the 4 true (lesser) pelvis muscles?

• piriformis

• obturator internus

• levator ani

• coccygeus

rectus abdominis

• greater pelvis muscle

• paired muscles that run vertically on side of anterior abdominal wall (6-pack)

• extends from symphysis pubic to costal cartilages of ribs

• controls pelvis tilt and curvature of lower spine

SONO: rectus abdominis

• hypoechoic with echogenic striations in LONG

• right and left rectus abdominis muscles join linea alba (echogenic) which courses along abdominal midline

psoas major

• greater pelvis muscle

• origin: lumbar spine

• insertion: lesser trochanter (posterior femur)

• courses inferiorly

• DOES NOT ENTER true pelvis

• joins iliacus muscle to form iliopsoas muscle

• “paired muscles that originate at transverse process of lumbar vertebrae and extends inferiorly through false pelvis on pelvic sidewall, where it unites with iliacus muscle to form iliopsoas muscle before inserting into lesser trochanter of the femur; serves to flex the thigh toward the pelvis”

SONO: psoas major

• visualized while imaging kidneys

• hypoechoic muscle tissue with echogenic striations

iliacus muscle

• greater pelvis muscle

• origin: inner iliac crest/fossa and sacrum

• insertion: lesser trochanter (posterior femur)

• courses inferiorly

• DOES NOT ENTER true pelvis

• joins psoas muscle to form iliopsoas muscle

• “paired triangular, flat muscles that cover the inner curved surface of iliac fossae; arise from iliac fossa and join psoas major muscles to form lateral walls of the pelvis”

iliopsoas muscle

• greater pelvis muscle

• group of muscles:

  • psoas major

  • psoas minor

  • iliacus

• origin: lumbar, sacrum, iliac crest and fossa

• insertion: lesser trochanter (posterior femur)

• functions:

  • hip flexor

  • stabilize lower back and core

  • exits pelvis posterior to inguinal ligament

SONO: iliopsoas muscle

• hypoechoic with echogenic linear striations in LONG

• distal iliopsoas tendon is echogenic

piriformis muscle

• lesser pelvis muscle

• origin: sacrum

• insertion: greater trochanter (lateral femur)

• “flat, pyramidal muscle arising from anterior sacrum, passing through greater sciatic notch to insert into superior aspect of greater trochanter of femur; serves to rotate and abduct the thigh”

• associated with piriformis syndrome (baby pressing on pelvis —> piriformis compressing on nerve, causing nerve injury)

SONO: piriformis muscle

• flat

• triangular-shaped

• hypoechoic

** can be mistaken for ovary—so elongate transducer to see if “ovary” elongates

obturator internus muscle

• lesser pelvis muscle

• origin: anterolateral pelvic wall/pubic ramus/obturator foramen

• insertion: greater trochanter (lateral femur)

• “triangular sheet of muscle that arises from anterolateral pelvic wall and surrounds obturator foramen; passes through lesser sciatic foramen and inserts into medial aspect of greater trochanter of femur; serves to rotate and abduct the thigh”

SONO: obturator internus muscle

• hypoechoic elongated, vertical, ovoid structure

levator ani

• lesser pelvis muscle

• pelvic floor muscles

• group of muscles:

  • pubococcygeus

  • puborectalis

  • iliococcygeus

• spans pelvic floor like hammock to support internal organs

• plays important role in rectal and urinary incontinence

• forms pelvic diaphragm with coccygeus muscle

• kegel exercises strengthen the muscle

• “one of the two muscles of the pelvic diaphragm that stretch across the floor of the pelvic cavity like a hammock, supporting the pelvic organs and surrounding the urethra, vagina, and rectum; a broad thin muscle that consists of pubococcygeus, puborectalis, and iliococcygeus muscles”

coccygeus

• lesser pelvis muscle

• located on posterior pelvic floor

• triangular sheet of muscle

• posterior aspect of pelvic diaphragm

• not usually evaluated on US

• “one of the two muscles in pelvic diaphragm; posterior pelvic floor muscle that support the coccyx”

anatomy of female pelvis

** filled bladder pushes uterus back —> better acoustic window

anatomy of female reproductive system

vagina

• collapsed muscular tube that extends from external genitalia to cervix of uterus

• posterior to bladder and urethra

• anterior to rectum and anus

• forms 90-degree angle with uterine cervix

• vaginal lumen surrounding cervix is divided into 4 fornices:

  • anterior

  • posterior

  • lateral (x2)

• inner walls from vaginal canal

• outer walls form muscular layer

SONO: vagina, cervix, uterus

uterus

• located in lesser (true) pelvis

• posterior to bladder in vesicouterine pouch

• anterior to colon/rectum in rectouterine pouch (aka Pouch of Douglas)

what is A pointing to?

vesicouterine pouch

what is B pointing to?

rectouterine pouch (aka Pouch of Douglas)

potential spaces where fluid may accumulate

• anterior cul-de-sac (vesicouterine pouch)

  • in front of uterus

• posterior cul-de-sac (pouch of Douglas/rectouterine space)

  • behind uterus

  • FF often accumulates here b/c of gravity and bigger space

• Space of Retzius (retropubic space)

  • in front of bladder

  • “between anterior bladder and pubic symphysis”

another name for anterior cul-de-sac

vesicouterine space

another name for posterior cul-de-sac

pouch of Douglas or rectouterine space

another name for space of Retzius

retropubic space

uterus anatomy

• thick walled, pear-shaped, muscular organ

  • uterus must be able to stretch and flex to push baby out

• 3 major sections:

  • fundus

  • body

  • cervix

uterine fundus

• widest, most superior portion

• located above fallopian tubes

uterine body

• aka corpus

• main part of uterus

• largest portion

uterine cervix

• 1-inch long

• projects into vagina

• cylindrical and fibrous

• internos os

• external os

internal os

• “os” = opening

• junction of cervical canal and endometrial canal

• “constricts upper end of cervix”

external os

• “os” = opening

• junction of cervical canal and vaginal canal (cervix to vagina)

• “constricts lower end of cervix”

cornua

• horn-shaped portion

• where fallopian tube is attached to uterus

isthmus

• narrow portion between uterine body and cervix

• point where uterus bends anteriorly or posteriorly with an empty bladder

• isthmus is the narrow region connecting the main uterine body to the cervix

LUS

• lower uterine segment (LUS)

• lower portion of uterus

• includes: internal os, cervical canal, and external os

A?

fundus

B?

body

C?

internal os

D?

external os

E?

LUS

F?

cervical canal

G?

bowel

TA pelvic anatomy in TRANS

starting TRV is easiest way to find ovaries

A?

isthmus

transvaginal pelvic anatomy in LONG

** patient must empty bladder

prepubertal (+ newborn) uterus size

• length: 1-3 cm (2-4 cm)

• width/AP: 0.5-1 cm

• cervix/corpus ratio: 1:1 (2:1)

** newborns have bigger uterus and ovaries because of moms hormones

nulliparous uterus size

adult who has never been pregnant:

• length: 6-8 cm

• width/AP: 3-5 cm

• cervix/corpus ratio: 1:2

parous uterus size

adult who has had a baby:

• length: 8-10 cm

• width/AP: 5-6 cm

• cervix/corpus ratio: 1:2

postmenopausal uterus size

• length: 3-5 cm

• width/AP: 2-3 cm

• cervix/corpus ratio: 1:1

is this uterus normal?

yes, for a normal adult

what is this image showing?

atrophic uterus in post-menopausal women

3 tissue layers of the uterus

1. perimetrium (serosa)

2. myometrium

3. endometrium

perimetrium (serosa)

• thin, external layer

• echogenic

myometrium

• middle, thickest layer

• hypoechoic

• made up of smooth muscle

endometrium

• innermost layer

• thickness and appearance depends on menstruation cycle

• echogenic-mildly hypoechoic

endometrium anatomy (layers)

1. superficial functional layer

2. deep basal layer

superficial functional layer

• innermost layer of endometrium

• sheds during menses

deep basal layer

• layer of endometrium

• regenerates new endometrial tissues after menses

• very vascular

normal uterus and endometrium values

• uterus: 6-8 cm nulliparous; 8-10 cm multiparous

• endometrium: <14 mm (less than 1.4 cm)

uterine ligaments

• ligaments attach bone to bone or organ to organ

• uterus is supported in its midline position by:

  • broad ligaments

  • round ligaments

  • cardinal ligaments

  • uterosacral ligaments

broad ligaments

• double fold of peritoneum that drapes over uterus, fallopian tubes, and ovaries

• lateral side of uterus to sidewall of pelvis

• 3 portions:

  • mesosalpinx

  • mesovarium

  • mesometrium

• “broad fold of peritoneum draped over the fallopian tubes, uterus, and ovaries; extends from sides of uterus to side walls of the pelvis; divided into 3 portions—mesosalpinx, mesovarium, and mesometrium”

mesosalpinx

• upper fold that drapes over fallopian tubes

• “upper portion of broad ligament that encloses fallopian tubes”

** -salpinx=fallopian tubes

mesovarium

• posterior portion that attaches to ovary

• “posterior portion of broad ligament that enclose and hold the ovary in place”

** -ovarium=ovary

mesometrium

medial portion that drapes over uterus

** -metrium=uterus

which ligament is represented by green? red? yellow?

• green=mesosalpinx

• red=mesovarium

• yellow=mesometrium

round ligaments

• fibrous cords between layers of broad ligaments

• cord on each side of superior aspect of uterus; courses upward and lateral to inguinal canal, inserting into labia majora

• stabilizes uterine fundus and body in forward position

• provides anterior support to uterus

• “paired ligaments that originate at uterine cornua, anterior to fallopian tubes, and course anterolaterally within broad ligament to inert into the fascia of the labia majora; hold the uterus forward in its anteverted position”

cardinal ligaments

• one of the two ligaments that anchor the cervix (only portion of uterus that is fixed/firmly supported)

• continuation of broad ligament

• extend across lateral pelvic floor

• “wide bands of fibromuscular tissue arising from lateral aspects of cervix and inserting along lateral pelvic floor; a continuation of the broad ligament that provides rigid support for the cervix”

uterosacral ligaments

• one of the two ligaments that anchor the cervix (only portion of uterus that is fixed/firmly supported)

• attached at uterine isthmus

• extends posterolaterally from cervix and insert over sacrum

• “posterior portion of cardinal ligaments that extends from cervix to sacrum”

fallopian tubes

• aka salpinx

• paired, muscular tubes that extend from cornua laterally to fimbriae

• 10-12 cm in length

• 1-4 mm in diameter

• 3 layers:

  • serosa (outermost)

  • muscular (middle)

  • mucosal (innermost)

what is the middle layer of the fallopian tube called?

muscular

what is the innermost layer of the fallopian tube called?

mucosal

4 segments of the fallopian tubes

1. interstitial

2. isthmus

3. ampulla

4. infundibulum

fallopian tubes: interstitial portion

• comes right off uterus

• proximal portion that passes through uterine wall

fallopian tubes: isthmus

• medial (middle) segment after interstitial portion of uterus

• longer than interstitial portion

fallopian tubes: ampulla

• longest segment

• typical site of fertilization

fallopian tubes: infundibulum

• widest portion of tube

• contains fimbriae—fingerlike projections at end of tube that empties into peritoneal cavity

SONO: fallopian tubes

usually not seen unless significantly distended (from fluid, pus, blood)

normal ovarian anatomy

ovaries:

• paired, ovoid/almond-shaped organs

• suspended in the pelvis by mesovarium

• located medial to external iliac vessels and anterior to internal iliac vessels

• consists of outer layer (cortex) that surrounds central medulla

  • cortex: contains mostly follicles

  • medulla: contains connective tissue, lymphatic vessels, nerves and blood

ovaries produce what cells and hormones?

• produce reproductive cells (ovums)

• 2 hormones:

  • estrogen (secreted by follicles)

  • progesterone (secreted by corpus luteum)

normal ovarian measurements

• ovary measures 3-4 cm with volume between 4-6 mL

• ovarian follicles are normally visible

• dominant follicle (aka Graafian cyst) develops prior to ovulation and measurements ≤ 3 cm

ovary size

• premenarch (before puberty)

  • volume: <2 mL

• menstrual age

  • length: 2.5-5.0 cm

  • width: 1.5-3.0 cm

  • height: 0.6-2.2 cm

• postmenopausal

  • volume: 3-6 mL

what is the normal L x W x H for menstrual age ovary size?

• length: 2.5-5 cm

• width: 1.5-3 cm

• height: 0.6-2.2 cm

ovarian ligaments

1. ovarian ligament

2. suspensory (infundibulopelvic) ligament

3. mesovarium (broad ligament)

ovarian ligament

• originate bilaterally at cornua of uterus

• supports ovary medially

• “paired ligament that extends from inferior/medial pole of ovary to the uterine cornua”

suspensory ligament

• extends from infundibulum of fallopian tube and ovary to sidewall of pelvis

• supports ovary laterally

• “paired ligaments that extend from infundibulum of fallopian tube and lateral aspect of ovary to lateral pelvic wall”

mesovarium

attaches ovary to posterior aspect of broad ligament

common iliac arteries

• courses anterior and medial to psoas muscles

• provides blood to lower extremities and pelvic cavity

• bifurcates into external and internal iliacs

external iliacs

course along pelvic brim and continue inferiorly as common femoral arteries

internal iliacs

• extend into pelvic cavity

• multiple branches that perfuse pelvic structures: like bladder, uterus, vagina, and rectum

• branches into uterine artery and vaginal artery

what branches off the internal iliac artery?

1. uterine artery

2. vaginal artery

uterine artery

• supplies the uterus

• courses above and anterior to the ureter, extending medially in the base of the broad ligament to the uterus at the level of the cervix