5.16 Female Internal Genitals

Uterus (345-8)

Flattened pear-shaped organ 8x5x3

Fundus: above entrance of tubes, convex, serous coat of peritoneum over top.

Body: tapers down, flat anteroposteriorly, covered with peritoneum ® broad ligament laterally

-           receives tubes at cornu, jx of fundus and body

-           posterior intestinal surface faces up, with intestines coiled on it

-           anterior vesicular surface down, on bladder, vesicouterine pouch intervening.

-           Lower 1/2cm of body = isthmus (of body), forms ‘lower segment’ at birth / C-section.

Cervix: tapers below body, clasped by vaginal vault, protrudes into vagina

-           surrounded by fornix, deepest posteriorly.

-           Posterior surface covered in peritoneum – rectouterine pouch of Douglas.

-           Anterior surface is deep in vesicouterine pouch; no peritoneum, attached by c.t. ® trigone

Ureter is 2cm from cervix as it passes lateral to then in front of fornix

-           may be closer to one side than the other, as uterus is rarely midline.

Canal of the cervix: continuous with cavity of body at internal os (lower vaginal opening = external os)

-           circular in nulliparous, transverse slit after childbirth, anterior lip lower than posterior.

 

Uterine Tubes (346)

10cm long each, with 1cm embedded in uterine wall.

-           then lies in upper edge of broad ligament, embraced in peritoneal fold = mesosalpinx.

Isthmus: adjacent to uterus, straight and narrow.

Ampulla: adjacent; >1/2 tube length;

Infundibulum: at end is covered in fimbriae into which ova drop;

-           one fimbria is longer and attached to ovum, open end behind broad ligament ® lat pelvic wall

Histology

2 layers of visceral muscle (inner circular, outer long), mm thrown into folds, ciliated mainly at fimbriated end, the least muscular portion.  Beat ® uterus.

Blood Supply

Uterine artery (br of internal iliac) ® uterus; passes medially across floor in base of broad ligament.

-           branches ® cervix & vagina

-           then turns up ® between layers of broad lig ® cornu with branches penetrating uterus walls

-           ® anastomose across midline with fellow branches

-           ® anastomoses with tubal branch of ovarian artery across tubes.

Veins course below artery at lower edge of broad lig = wide plexus across floor.

-           communicate with vesical and rectal plexi ® internal iliac veins; tubal vein joins ovarian veins.

Lymph

Cervix ® External and internal iliac nodes and to sacral nodes (via uterosacral ligaments)

Lower part of body ® external iliacs

Upper part & tubes with ovaries ® para-aortic nodes

-           few to external iliacs, and few from cornu ® superficial inguinal. 

Note lymph from cervix won’t reach inguinal nodes.

Nerves

Uterus = branches of inferior hypogastric plexus; SNS = vasoconstrictor and facilitates muscle

-           however high division does not affect contractility, even labour.

-           Pain via pelvic splanchnic nerves; except body / cervix ® SNS (eg in labour) T10-L1

-           Note however presacral neurectomy (cutting hypogastric nerves from superior hypogastric plexus does not abolish labour pain.

-           Distension ® pain, but relatively insensitive to cutting and burning; tube sensitive to touch and cold

Structure

Myometrium = 3 layers; ill-defined, outer longitudinal (expulsive), inner constrict vessels, tubes, os.

Endometrium = columnar epithelium ® dips into stroma as glands (varies with cycle)

Mucosa = mucous secreting, not cyclical, changes ® stratified squamous just inside external os.

Supports

Normally antiflexed (leans forward over bladder) and anteverted (leans forward from vagina)

-           20% nulliparous women = retroflexed (benign)

Cervix is most fixed portion; attachment to back of bladder, fornix, pelvic diaphragm, fascial condensations (as ligaments) and some peritoneal attachments.

-           pubovaginalis part of levator and perineal body support vagina, assist holding cervix up

-           stretching in childbirth ® posterior wall prolapses, uterus retroverts.

Broad ligament

Lax fold of peritoneum lateral to uterus (not supportive); peritoneum flows over uterus & bladder.

-           at base, passes forwards and backwards to line the pelvic cavity (ureter under post layer)

-           laterally, crosses obturator nerve, superior vesical / obliterated umbilical vessels, obturator artery and vein.

-           Upper is free: contains tubes and laterally ovarian vessels & lymph ® extends over external iliac vessels as suspensory ligament of ovary.

-           Anterior layer bulges forward (due to round lig just below tube)

-           Posterior has a fold projecting back, suspending the ovary (mesovarium)

-           Between the layers = parametrium (loose areolar tissue); lying in it are: uterine vessels and lymph, round ligament, lig of ovary and vestigial mesonephric epoophoron & paroophoron

Round ligament

From jx of uterus & tube to deep inguinal ring

-           ® continuous with lig of ovary (together = female gubernaculum)

-           ® inguinal canal ® fibrofatty tissue of labium majus of vulva

Supplied by branch of ovarian artery in broad ligament & inferior epigastric in inguinal canal.

Smooth muscle and fibrous tissue \ holds uterus in anteflexion & anteversion in face of bladder pressure and gravity.

Transverse cervical ligament

Thickening of c.t. in broad lig base: from cervix & vaginal fornix laterally ® pelvic side wall

-           traversed by: ureter, uterine artery, inferior hypogastric plexus.

Imparts lateral stability to cervix and supports uterus.

Uterosacral ligaments

Fibrous c.t. & smooth muscle: from cervix below peritoneum ® rectouterine pouch ® sacrum

-           palpable on rectal examination; keep cervix braced back against pull of round ligament

-           \ help maintain anteversion

Development

Paramesonephric (Mullerian) ducts = linear evagination in coelomic epithelium on lat mesonephros

-           grow caudally lateral to the ducts, then cross ventrally & fuse caudally ® uterus

-           continue to reach dorsal wall of urogenital sinus ® upper wall of vagina

-           cranial ends persist = uterine tubes

Incomplete fusion = median septum in uterus or bicornuate uterus.

Surgical Approach

Abdominal or vaginal; Broad, round and ovarian ligaments and tubes divided on each side near uterus.

-           lower ends of ureters need safeguarding (esp when uterine arteries divided)

Ant and post walls cut across below cervix (cervix preserved in subtotal procedure)

 

Ovaries

3x2x1 cm (smaller during non-ovulatory years); lying almost vertical when standing.

-           upper extremity tilted laterally and overlapped by fimbriated end of uterine tube

-           lower tilted toward uterus, attached by ligament of ovary (continuous with round lig at cornu)

-           anterior surface attached to posterior layer of broad ligament by mesovarium.

-           posterior faces peritoneal cavity, covered in cuboidal epithelium.

-           Laterally lies b/n internal & external iliac vessels, on peritoneum (under which is obturator nerve  laterally and ureter posteriorly ® referred pain to inner thigh)

-           Medial surface related to uterine tube.

Line and location changes in pregnancy

Can be palpated through vagina by tip of finger

Overlain by loopy sigmoid and ileum in rectouterine pouch.

Blood (247-8)

Ovarian artery from aorta just below renal; runs behind peritoneum and colic vessels ® crosses ureter on psoas ® over brim of pelvis ® enters suspensory lig at lateral edge of broad ligament

-           branch given to uterine tube ® meets  uterine artery (runs b/n broad lig)

-           then ends at ovary

Veins form a plexus in the mesovarium and suspensory lig (pampiniform plexus cf testes)

® paired ovarian veins accompanying the artery ® single vein ® IVC / L renal vein.

Lymph

Para-aortic nodes alongside the artery origin (L2)

-           can reach inguinal nodes (via round lig and inguinal canal) & opposite ovary across uterus

Nerves (383,6)

SNS (vasoconstrict) = from aortic plexus along vessels (preganglionic from T10,11)

PNS reach the ovary from inferior hypogastric plexus (vasodilatory) via uterine artery

-           nerve supply not needed by follicles; no supply

Sensory = SNS, hence referred periumbilically (cf testes)

Structure

Vascular medulla and outer cortex (contains follicles)

-           encapsulated by tunica albuginea (fibrous c.t.) then cuboidal cells / superficial epithelium

Oogonia derived from endoderm of yolk sac migrate to developing cortex early in fetal life

-           multiply ® primary oocytes, surrounded by 1x layer of follicular cells = primordial follicles.

-           1million at birth, 40,000 by puberty, few at a time ® develop in cycles; 1 ® mature, ovulates

-           primordial follicle ® primary ® secondary ® tertiary (Graafian) follicle, surrounds = theca.

-           undergoes meiosis before ovulation (= secondary)

-           At ovulation, liquor folliculi escapes, and granulosa (+some theca) ® corpus luteum.

-           Later scars up ® corpus albicans.

Only 400 ova can be shed ® atretic follicles.

Development

Ovary develops from paramesonephric ridge from intermediate cell mass.

-           origin in peritoneum of post abdo wall; descends preceded by gubernaculum

-           gubernaculum passes through inguinal canal ® labium majus; but cf testes, descent arrested prior to deep ring at uterus.

Mesonephric ducts normally disappear; if they persist = remnants in broad ligament

-           epoophoron = tubules at right angles (persisting mesonephric duct in mesosalpinx)

-           duct of Gaertner = opening into lateral fornix of vagina from remnant duct

-           paroophoron = nearer base of broad lig (minute tubules); can enlarge as cysts.

 

Vagina (345)

Highly expansile fibromuscular tube (10cm) ® up and back from introitus

-           H shaped with ant/post walls opposed; anteroposterior cleft at introitus

-           Anterior to rectum, anal canal and perineal body, Post to bladder and urethra

-           Rectovaginal septum (thin) separates it from the bladder.

Upper end expanded to receive cervix: margin = vaginal fornix (ant, post & lateral; post deeper)

-           post fornix covered by rectouterine pouch peritoneum (only part of vagina to have peritoneum)

-           Ureter first adjacent to lateral fornix ® cross to anteriorly ® insert into bladder

-           Ureters thus embedded in vaginal wall, base of bladder in contact with anterior vagina also

Passes down through pubovaginalis parts of levator ani ® through urogenital diaphragm & perineal membrane ® superficial perineal space; where orifice lies in the vestibule

-           internal remains of hymen, vestibular glands to sides, urethra ant w/ lesser vestibular glands b/n

Blood supply

Vaginal branch of internal iliac

Supplemented by uterine, inferior vesicle, middle rectal ® anastomotic plexus

Veins ® plexus on pelvic floor ® internal iliac

Lymph

To external and internal iliac nodes;

Lowest part below hymen level (like other perineal structures) ® superficial inguinal nodes

Nerves

Lower vagina = sensory from perineal, posterior labial branches of pudendal nerve, and ilioinguinal nerve (latter with anterior vulva)

-           ANS via inferior hypogastric plexuses (® vessels, muscles, glands)

-           Upper vagina sensitive only to stretch, ® afferent fibres with SNS.

Structure

Muscular smooth muscle, lined internally by mucous membrane, externally by fibrous tissue continuous with pelvic fascia (except post vagina fornix = peritoneum)

-           outer longitudinal and inner circular interlace

Mucous membrane = stratified squamous non-keratinising epithelium overlying c.t. lamina propria

-           large thin-walled veins inside = erectile-type tissue

No muscularis mucosa and no glands

Before parturition, mm of anterior and posterior walls have medial longitudinal ridges = several transverse rugae extend bilaterally.

VE

Upper – cervix, with bladder, urethra, pubic symphysis in front

Posterior = rectouterine pouch

Can feel body of uterus, ovaries and uterine tubes around lower abdo wall.

Development

Mostly like uterus from fused paramesonephric ducts; lower part from urogenital sinus (epithelium replaces that derived from ducts).

Labia minora from urogenital folds ® bound orifice.

Female Urethra

4cm.  Neck of bladder ® external meatus.

Embedded in anterior vaginal wall except at upper end

Pubovaginalis fibres embrace it at exit from bladder and help compress it.

Catheterisation is easy but note in late pregnancy may be 10cm long due to stretching.

-           pubic symphysis anteriorly; fetal head may compress urethra against it.

Blood Supply

Upper: Inferior vesical and vaginal arteries

Lower: internal pudendal artery

Veins: ® vesical plexus & internal pudendal vein

Lymph

® internal iliacs; some reach external

Nerve

Inferior hypogastric plexus and perineal branch of pudendal nerve.

Structure

Urothelium proximally, non-keratinised stratified squamous distally

Few mucous glands in wall (largest = Skenes / paraurethral glands)

-           open into a single duct on each side inside external meatus (female homologue of prostate)

Superficial trigonal muscle ® extends into urethra

Muscle mainly longitudinal ® contraction shortens urethra, widens lumen

-           outside = sphincter urethrae, thickest at middle, mainly at front; (pudendal n.)

Development

Urogenital sinus; corresponds with prostatic urethra in male.