Normal anatomy & physiology of The female pelvis

Normal anatomy & physiology ofThe female pelvisPresentation by Meg Sullivan & Shannon WrightCHAPTER 39Two approaches are used to evaluate the female pelvis sonographically: transabdominal and transvaginal.

The transabdominal approach:Requires a full urinary bladder.Uses a 3.5-5 MHz transducer.Offers a wider field of view for general screening.

The transvaginal approach:Performed with an empty bladder.Uses a higher frequency transducer, typically 7.5-10 MHz.Offers a more detailed study but is limited in its field of view and depth of penetration.

A complete pelvic examination should consist of a transabominal scan followed by a transvaginal examination.Ultrasound of the female pelvisPELVIC LANDMARKSExternal Landmarks

The Bony Pelvis

The Pelvic Cavity and PeritoneumThe external genitalia in the female, also known as the vulva or pudendum, consist of the mons pubis, labia majora, labia minora, clitoris, urethral opening, and vestibule of the vagina.

The vagina itself is the part of the female genitalia that forms a canal from the orifice through the vestibule to the uterine cervix. It is behind the bladder and in front of the rectum.

These external structures are important to recognize when using translabial and transvaginal scanning techniquies.External landmarks

The mons pubis is a pad of fatty tissue and thick skin that overlies the symphisis pubis and is covered by pubic hair after puberty.External landmarks

The labia are folds of skin at the opening of the vagina. The labia majora is the thicker external folds. The labia menora is the thin folds of skin between the labia majora.External landmarks

The clitoris is located anterior to the urethra and is usually partially hidden between the labia major.External landmarks

Posterior to the clitoris, the urethral opening and vestibule of the vagina can be normally identified between the labia minora. The most posterior orifice is the anus.External landmarksThe bony pelvis consists of four bones: two innominate (coxal) bones, the sacrum, and the coccyx.

The Ileopectineal Line is an imaginary line that dissects the pelvis, dividing it obliquely into two anatomical compartments.

Pelvis Major (False Pelvis) above pelvic brim; communicates with the abdominal cavity

Pelvis Minor (True Pelvis) below pelvic brim; considered to be the Pelvic Cavity

The bony pelvisMUSCLESOF THE PELVISThe Abdominal Wall

Muscles of the False Pelvis

Muscles of the True Pelvis

These muscles extend from the xiphoid process to the symphysis pubis.

Rectus abdominis, external oblique, internal oblique, transversus abdominis.The abdominal wall Include the psoas major and iliacus muscles, which form the pelvic side wall.

The psoas major muscles join with the iliacus muscles to form the iliopsoas muscles, which do not enter the true pelvis.

Muscles of the false pelvisInclude the piriformis muscles, obturator internus muscles, and muscles of the pelvic diaphragm.

The piriformis muscles form the posterolateral wall.

The obturator internus muscles form the anterolateral pelvic side wall.

The pelvic diaphragm is formed by the levator ani and coccygeus muscles to make up the pelvic floor.Muscles of the true pelvis

Muscles of the true pelvis The ureters are the two tubes that carry urine inferiorly from the kidneys to the urinary bladder.

The urinary bladder is located in the anterior portion of the pelvic cavity.

The function of the bladder is to collect and store urine until it empties through the urethra.Bladder&ureterschange layout to "title slide" The vagina is a collapsed muscular tube that extends upward and backward, from the external genitalia to the cervix of the uterus.

It lies posterior to the urinary bladder and urethra, and anterior to the rectum.

It is the passageway for menstruation and is extended during sexual intercourse and childbirth.Vagina

change layout to "title slide"UTERUSNormal Anatomy

Endometrium

Uterine Ligaments

Positions The uterus is a pear-shaped organ that consists of a fundus, body, and cervix.

Size varies with age and parity; 6-8 cm in length and 3-5 cm in anteroposterior and transverse dimensions.

The uterine cavity is a potential space for fluid accumulation, allowing for dynamic changes during menstrual cycle and pregnancy.Normal anatomy

UTERUS At the lateral borders of the fundus (widest, most superior portion) are the cornua, where the fallopian tubes enter the uterine cavity.

The body (corpus) lies between the fundus and the cervix and is the largest portion of the uterus.

The cervix is the lower cylindrical portion that projects into the vaginal canal.Normal anatomy

UTERUS The uterine wall consists of 3 histologic layers:

The serosa or perimetrium, is the external layer.

The myometrium is the muscular middle layer (thickest).

The endometrium is a mucous membrane lining the glandular tissue.Normal anatomy

UTERUS The endometrium changes dynamically in response to the cyclic hormonal flux of ovulation.

It varies in sonographic appearance and histologic structure.

Two primary layers:

Superficial functional layer: consisting of glands and stroma (supporting tissue) that sheds with menses.

Basal layer: the thin layer of the ends of endometrial glands that regenerates new endometrium after menses.endometriumUTERUS The uterus is supported in its midline position by paired broad ligaments, round ligaments, uterosacral ligaments, and cardinal ligaments.

Uterine ligaments

Broad Ligaments are a double fold of peritoneum that drape over the fallopian tubes, uterus, and ovaries.

Extend from the lateral sides of the uterus to the side wall of the pelvis.

Contain uterine blood vessels and nerves.

Mesosalpinx: upper fold that encloses fallopian tube.

Mesovarium: posterior portion that encloses the ovary.Uterine ligaments

Round ligaments are fibrous cords that occur in front of and below the fallopian tubes between the layers of the broad ligament.

These two cords commence on each side of the superior aspect of the uterus, course upward and lateral to the inguinal canal and insert into the labia majora.

Helps hold the uterine fundus and body in a forward position.Uterine ligaments

The cervix is the only portion of the uterus that is firmly supported.

It is fixed in position by the cardinal ligaments (continuation of broad ligaments) and the uterosacral ligaments.Uterine ligaments

Although variable, the average uterus position is considered to be anteverted and anteflexed.

It is not unusual to see a uterus that has variations of version and flexion.

Abnormal dropping of the uterus (uterine prolapse) occurs if the uterine ligaments and pelvic floor muscles are weak.

The uterus may also tilt to the right (dextro) or left (levo) of the midline.

Filling of the bladder will affect uterine position; a full bladder will tip the average anteverted, anteflexed uterus backward.Positions of the uterus Anteversion

Most common position

The cervical canal forms a 90-degree or smaller angle with the vaginal canal.Positions of the uterus

Anteflexion

The body and fundus of the uterus are curved forward upon the cervix.Positions of the uterus

Retroflexion

The uterine fundus or body curves backward upon the cervix.Positions of the uterus

Retroversion

The cervical canal forms an angle less than 90-degrees with the vaginal canal.

In multiparous females, the entire uterus may tip backward rather than forward.Positions of the uterus

Retroversion with retroflexion

The entire uterus is tilted backward with the fundus and body folded posteriorly upon the cervix.Positions of the uterus

The fallopian tubes are oviducts that are coiled, muscular tubes that open into the peritoneal cavity and their lateral end.

Approximately 10-12 cm in length;1-4 mm in diameter.

Four anatomic portions:

Infundibulum Ampulla Isthmus Interstitial

Fimbriae: fringe-like extensions which move over the ovary, directing the ovum into the fallopian tube after ovulation.FALLOPIANTUBESchange layout Infundibulum

Wide trumpet-shaped lateral portion

Contains fimbriaeFallopian tubes

Ampulla

Longest and most coiled portion of the fallopian tube

Area in which fertilization of the ovum most often occursFallopian tubes

Isthmus

Medial segment of the fallopian tubeFallopian tubes

Interstitial

Segment that passes through the uterine cornua

Narrowest segment of the fallopian tubeFallopian tubes

Position & Size

Normal Anatomy

Ovarian LigamentsovariesovariesPosition & Size Almond-shaped structures Measure approximately 3 cm long Lie in ovarian fossa, posterior to the uterus Dual blood supply:ovarian arteryuterine artery The ovarian vein drains blood into IVC on the right, and into the renal vein on the left.ovariesNormal Anatomy Outer cortexConsists of follicles in various developmental stagesTunica albuginea: dense covering connective tissue of cortexGerminal epithelium: thin layer of cells surrounding tunica albuginea Central medullaConnective tissue containing blood, nerves, lymphatic vessels, and some smooth muscle at the region of the hilum Ovaries produce the reproductive cell, the ovum Two steroidal hormones:Estrogen secreted by the folliclesProgesterone secreted by the corpus luteumResponsible for producing and maintaining secondary gender characteristics and for preparing the uterus for implantation of a fertilized ovum and for development of the mammory glands in the female.

ovariesOvarian Ligaments Supported medially by the ovarian ligaments. Originate bilaterally at the cornua of the uterus Supported laterally by the suspensory (infundibulopelvic) ligaments. Extend from infundibulum of the fallopain tube and ovary to the sidewall of the pelvis The ovaries are also attached to the posterior aspect of the broad ligament by a fold of peritoneum called the mesovarium.PELVIC VASCULATUREPelvic vasculatureVesselLocationExternal iliac arteriesMedial psoas borderExternal iliac veinsMedial and posterior to arteriesInternal iliac arteriesPosterior to ureters & ovariesInternal iliac veinsPosterior to arteriesUterine arteries & veinsBetween layers of broad ligaments, lateral to uterusArcuate arteriesArclike arteries that encircle uterus in outer third of myometriumRadial arteriesBranches of arcuate arteries that extend from myometrium to base of endometriumStraight & Spiral arteriesBranches of radial arteries that supply zona basalis of endometriumOvarian arteriesBranch laterally off aorta, run within suspensory ligaments and anastomose with uterine arteriesOvarian veinsRight vein drains into IVC directly; left drains into left renal veinPelvic vasculature

Pelvic vasculature

PHYSIOLOGYThe Menstrual Cycle

Follicular Development & Ovulation

Endometrial Changes

Abnormal Menstrual CyclesThe Menstrual cyclePHYSIOLOGYReproductive years begin with onset and end with cessation of menses

Menses: periodic flow of blood & cellular debris that occurs during menstruationAverage length: ~ 28 daysRegulated by hypothalamusDependent on cyclic release of estrogen & progesterone from ovaries

Menstruation: days 1 4 of the menstrual cycle

Menstrual StatusPremenarche pre-puberty; before onset of mensesMenarche post-puberty; menses occurs every 28 daysMenopause - cessation of mensesFollicular development & ovulationDevelopment of ovarian follicles monthly release of an ovum (ovulation)

PHYSIOLOGYOvulatory Cycle: cyclic release of estrogen & progesterone from ovariesLasts ~28 daysDetermines course of menstrual cycleOccurs in 2 phases Follicular and Luteal

Follicular development & ovulationPHYSIOLOGYFSH stimulates follicular development

Follicles secrete increasing amounts of estrogen as they grow

One follicle, the graafian follicle, reaches maturity

High estrogen levels trigger pituitary LH secretion

LH triggers ovulation on about day 14

Graafian follicle ruptures, releasing an ovum

Follicular PhaseDays 1-14 first day of menstruation through ovulationFollicular development & ovulationPHYSIOLOGYLuteal PhaseDays 15-28 corresponds to secretory phase of menstrual cycle

Ruptured follicle cells form corpus luteum (luteinization)

Corpus luteum secretes progesterone

Progesterone stimulates endometrial growth

Corpus luteum degenerates (9-11 days after ovulation)

Progesterone declines

Menstruation occurs; cycle begins againFollicular development & ovulationPHYSIOLOGYEndometrial changesPHYSIOLOGYVarying levels of EE & P endometrial change

Endometrial Cycle: characteristic changes in endometrium

Changes occur during menstrual cycle

Determined by hormonal changes during ovulatory cycle

Endometrial changesPHYSIOLOGY

3 phases of endometrial cycle:MenstrualProliferativeSecretoryEndometrial changesMenstruationDays 1-4Declining P spiral arteriole constrictionDecreased blood to endometrium ischemia & shedding of zona functionalisPHYSIOLOGY

Endometrial changesProliferative PhaseDays 5-14 corresponds to follicular phase of ovarian cycleThin endometriumOvarian follicles develop; estrogen increasesUterine lining regenerates & thickensOvulation on day 14PHYSIOLOGY

Endometrial changesSecretory PhaseDays 15-28 corresponds to luteal phase of ovarian cycleRuptured follicle becomes corpus luteumCorpus luteum secretes progesteroneEndometrium thickensIf no pregnancy, estrogen and progesterone decreaseMenses on day 28PHYSIOLOGY

PhaseSonographic Appearance of EndometriumMenstrualVarying levels of fluid & debris

Thickness decreasesProliferativeEarly: thin echogenic line

Mid-Phase: thickens to 4-8 mm; hypoechoic with three line sign

Before ovulation: 6-10 mm; becomes isoechoic with myometriumSecretory7-10 mm (thickest dimension)

Echogenic; three line appearance blurredEndometrial changesPHYSIOLOGYabnormal Menstrual cyclesMenorrhagia: Abnormally heavy or long periods

Oligomenorrhea: Menstrual cycles prolonged >35 days

Polymenorrhea: Menstrual cycles with interval