FACTS & HINTS

High-Yield Facts

Clinical Points

Micturition

The bladder has a capacityof 400 to 500 mL

During micturition coordinated reflexive contraction of the detrusor and relaxation of the external urethral sphincter occur Controlled byautonomic and visceral innervation

Visceral afferent fibers traveling along tract of parasympathetic fibers stimulated bystretching (and pain in lower bladder)

Parasympathetic innervation via pelvic splanchnic nerves and pelvic plexus reflexivelystimulates detrusor contraction during micturition.

Sympathetic fibers via hypogastric plexus to bladder neck relaxes bladder neck (internal urethral sphincter) and prevents retrograde ejaculation during micturition in males

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Clinical Points

Fractures of the Pelvis and Bladder Injury

The bladder lies immediatelyposterior to the pubic symphysis and fractures of the pubis can be complicated byrupture of the bladder. The rupture can result in the extravasation of urine intraperitoneallyif the peritoneum is torn

UrinaryTract Infections (UTIs)

As a result of a shorter urethra, women are more susceptible to UTIs Commonlyoccurs in women following sexual intercourse Pathogen is commonlyEscherichia coli

Infection maylead to urethritis, cystitis, or pyelonephritis (inflammation of urethra, bladder, and kidneys, respectively). Symptoms include: dysuria, urgency, frequency, and occasionallyhematuria

UrinaryStress Incontinence

Factors maintaining continence in the female are the external urethral sphincter (striated muscle surrounding middle third of urethra) and support of the bladder and urethra bythe levator ani muscles

Urinarystress incontinence is an involuntaryloss of urine that occurs during coughing, sneezing, laughing, lifting, or exercise, because of the inabilityof these muscles to counter the increase in intra-abdominal pressure.

Urinarystress incontinence is often seen in women who have had multiple pregnancies and vaginal childbirths and in men following prostate surgery

About 50% of all women have occasional urinaryincontinence

Mnemonics

Memory Aids

"Water under the bridge" -denotes relationship of ureter (water) to uterine artery, as it passes under the artery.

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36 Uterus, Vagina and Supporting Structures

STUDYAIMS

At the end of your study, you should be able to:

Describe the anatomyof the uterus and its supporting ligaments

Know the anatomyof the ovaryand the uterine tubes in relation to the pelvic cavity, the peritoneum, and the uterus

Know the anatomyof the cervix

Understand the orientation of the cervixrelative to the position of the uterus and changes with childbirth

Understand the anatomyof the vagina

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GUIDE

Pelvis and Perineum: Uterus, Vagina, and Supporting Structures

[Plate 352, Uterus, Vagina and Supporting Structures]

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[Plate 353, Uterus: Fascial Ligaments]

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[Plate 355, Uterus and Adnexa]

Uterus

Basic structure

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Pear-shaped organ

Approximately8 cm long and 5 cm wide Supported bythe pelvic diaphragm Composed of

Body(corpus) -upper two thirds

Fundus-rounded upper part superior to the entrances of the uterine tubes

Isthmus-narrower area just above the cervix

Cervix(neck) -cylindrical inferior part that projects into the superior vagina Uterine cavityis small (6 cm in length) and slit-like

Uterine horns are superolateral regions where the uterine (Fallopian tubes) enter Uterine wall has three layers

Perimetrium-outer layer of peritoneum with underlying connective tissue

Myometrium-middle, thick layer of smooth muscle

Endometrium-vascular inner mucosal layer the thickness of which varies with menstrual cycle and age The uterus has two surfaces: anteroinferior and posterosuperior

Aportion of the cervix, body, and fundus of the uterus is covered with peritoneum Cervix

Thick-walled canal, 2.5 cm long, connecting the bodyof the uterus with the vagina

Communicates superiorlyvia internal os with uterus

Communicates with vagina inferiorlyvia external os

Approximatelyhalf of the cervixlies above the vagina (supravaginal) and is covered posteriorlywith the peritoneum of the rectouterine pouch

The bladder is separated from the anterior surface of the supravaginal part of the cervixbyconnective tissue The lower half of the cervix(vaginal part) protrudes into the vagina and can be examined clinically

Relationships of the uterus

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PosteriorRectouterine pouch and anterior surface of rectum, loops of intestine in pouch

Vascular supply of uterus (including cervix)

Arterial

Uterine arteries (branches of internal iliac arteries)

Vaginal arteries (branches of uterine arteries with anastomoses with internal pudendal arteries)

Venous drainage: via uterine venous plexus to internal iliac veins

Lymphatics drain to

External iliac nodes

Internal iliac and sacral nodes

Superficial inguinal nodes (along round ligament)

Innervation

From the uterovaginal plexus, a subdivision of the inferior hypogastric (pelvic) plexus

Sympathetic, parasympathetic, and visceral afferents to and from the uterus pass through this plexus

Sympathetic innervation from lower lumbar spinal cord segments via lumbar splanchnic nerves and intermediate plexuses Parasympathetic innervation from pelvic splanchnic nerves (S2,3,4 spinal cord levels) via pelvic plexus

Afferent fibers with pain information from bodyand fundus ascend through plexuses to lumbar splanchnic nerves to reach upper lumber/lower thoracic spinal cord segments

Afferent fibers with pain information from cervixand all information except for pain from bodyand fundus follow parasympathetic fibers back to central nervous system

Vagina

Basic structure

Muscular tube, 8 to 10 cm long

Superior end surrounds the cervix: upper two thirds lie within pelvic cavity Slopes downward and forward through the pelvic diaphragm

Opens inferiorlyinto vestibule between labia minora Lining has multiple transverse folds-rugae

Recessed area of vagina around the cervixis called the vaginal fornix; composed of shallow anterior, deep posterior, and lateral fornices Posterior fornixdirectlyrelated to rectouterine pouch

Relationships of the vagina

Blood supply

Uterine arteries supplies superior part

Vaginal arteries supplymiddle part

Lower part supplied bymiddle rectal and internal pudendal arteries

Venous drainage

Vaginal venous plexus to uterine venous plexus to internal iliac veins

Innervation

Upper three fourths same as uterus

Lower one fourth is somatic via the pudendal nerve

Visceral and sympathetic fibers reach the lower one fourth via the pudendal nerve; no parasympathetics

Variations in Position of the Uterus

When the bladder is empty, bodyof the uterus bent anteriorlyon the cervix: anteflexion

Axis of cervixalso bent forward relative to axis of vagina: anteversion

Thus the bodyof uterus lies on superior surface bladder

Full bladder reduces these angles

Reversal of these angles is called retroversion and retroflexion

Ligaments Associated with the Uterus

Broad ligament

Double layer of peritoneum that sweeps up and over the uterus, ovaries, and the uterine tubes

Thus has an anterior and a posterior lamina

Extends from the sides of the uterus to the lateral pelvic walls

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Part that suspends the ovaryfrom the posterior lamina is the mesovarium

Part of broad ligament above the level of the ovaryand mesovarium that sweeps over the uterine tubes is the mesosalpinx

Part of broad ligament below the mesovarium or the mesenteryof the uterus

Uterine arteries and veins run mediallyfrom the internal iliac arteries to the uterus at its base Encloses the plexus of uterine veins

Ligament of the ovary

Extends from the medial pole of ovaryto the lateral wall of the uterus, just beneath the entrance of the uterine tube, on each side Remnant of proximal part of embryonic gubernaculums

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Round ligament of the uterus

Extends from the lateral wall of the uterus, just beneath the entrance of the uterine tube, to the lateral pelvic wall on each side Crosses external iliac vessel to enter deep inguinal ring

Passes through inguinal canal to labium majus Remnant of distal part of embryonic gubernaculums

Suspensory ligament of the ovary

An extension of the broad ligament superiorlyon the posterolateral pelvic wall

Covers the ovarian vessels, associated nerves, and lymphatics

Uterine (Fallopian) Tubes

Basic anatomy

Approximately10 cm long, extending laterallyfrom the uterine horns to the peritoneal cavitynear the ovaries

Run in free upper border of broad ligament (mesosalpinx)

Provide a channel for ova from ovaryto uterine cavityand site for fertilization

Divided into four parts for descriptive and functional purposes

Infundibulum

Horn-shaped distal end

Opens into peritoneal cavity

Has finger-like processes (fimbriae) at distal end that spread over surface of ovary

Ampulla

Widest and longest part

Where fertilization usuallyoccurs

Connects infundibulum and isthmus

Isthmus

Thick-walled

Enters uterine horn

Uterine part: passes through the wall of the uterus

Blood supply

Arterial (anastomoses)

Uterine arteries

Ovarian arteries

Venous drainage

Uterine venous plexus

Ovarian veins

Lymphatics

To lumbar lymph nodes

Innervation

Ovarian and uterine plexuses = subdivisions of pelvic plexus

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Ovaries

Basic structure

Ovoid in shape

Approximately4 cm long and 2 cm wide

Lie in the ovarian fossa on lateral pelvic wall between external and internal iliac vessels Attached to the broad ligament bymesovarium, which transmits ovarian vessels

Connected to lateral wall bysuspensoryligaments of the ovary, containing ovarian vessels, nerves, and lymphatics

Arterial supply

Ovarian artery

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Branch of abdominal aorta

Terminates in ovarian and tubal branches

Venous drainage

Pampiniform plexus combines to form single ovarian vein

On right this drains into the inferior vena cava

On the left drains into the left renal vein

Lymphatics

Follow ovarian vessels to lumbar lymph nodes

Innervation

Sympathetic and afferent fibers reach the ovaryvia the ovarian vessels

Parasympathetic fibers from pelvic splanchnic nerves (S2,3,4 spinal cord levels) reach ovaryvia same route

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