Download Anatomy of the genital tract The external genetalia: The external

Anatomy of the genital tract
The external genetalia:
The external genetalia is commonly called the vulva and includes the mons pubis, labia
majora and minora, vaginal vestibule, clitoris and greater vestibular glands.
Mons pubis: a fibrofatty pad covered by hair-bearing skin covering the body of pubic
bones.
Labia majora: two folds of skin with underlying adipose tissue lying either side of vaginal
opening, contain sebaceous, sweat and few apocrine glands.
Labia minora: two thin folds of skin lie between labia majora. Anteriorly, they divide in
two to form the prepuce and frenulum of the clitoris. Posteriorly, they divide to form a
fold of skin at the back of vaginal introitus (fourchette). They contain sebaceous glands
but no adipose tissue.
Clitoris: a 0.5-3.5 cm erectile structure and is made up of paired columns of erectile and
vascular tissue called: corpora cavernosa.
Vestibule: a cleft between the labia minora contains openings of the urethra, Bartholine’s
glands and the vagina.
Bartholine’s glands: are bilateral and open via a 2cm duct into the vestibule below the
hymen and contribute to lubrication during intercourse.
Hymen: a thin covering of mucous membrane across the entrance of the vagina. It is
usually perforated to allow menstruation. It ruptures during intercourse leaving remaining
tags: carunculae myrtifomes.
In the pre-pubertal vulva, no hair and little adipose deposition while during puberty pubic
hair develops and fat deposits within the labia. After menopause labia minora loses fat
and become thinner while vaginal opening becomes smaller.
The internal reproductive organs:
The vagina:
The vagina is a fibromuscular canal lined with stratified squamous epithelium that leads
from the uterus to the vulva. It is longer in the posterior wall (9cm) than the anterior
(7cm). The vault is divided into 4 fornices: posterior, anterior and 2 lateral. It has no
glands and is kept moist by secretions from uterine and cervical glands and from
transudation from its epithelium lining.
The epithelium is thick and rich with glycogen which increases in post-ovulatory phase.
The vagina is devoid of glycogen before puberty and after menopause due to lack of
estrogen. Doderlein’s bacillus is the normal vaginal flora that breaks glycogen to form
lactic acid and produce a PH around 4.5, which protects the vagina by decreasing
pathogenic bacterial growth.
The upper posterior wall form the anterior peritoneal reflection of the pouch of Douglas,
the middle third is separated from the rectum by the pelvic fascia and the lower third
abuts the perineal body. Anteriorly it is in direct contact with the base of the bladder and
the urethra. Laterally at the fornices, the vagina is related to the cardinal ligaments and
below this are the levator ani muscles and the ischio-rectal fossae. The cardinal and
utero-sacral ligaments supports the upper part of the vagina.
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At birth the epithelium is well developed (maternal estrogen influence). After few weeks
the epithelium atrophies and PH is 7, at puberty the reverse occurs and after menopause
the vagina shrinks and the epithelium atrophies.
The uterus:
The uterus is like an inverted pear tapering inferiorly to the cervix and situated entirely
within the pelvis (the non-pregnant state). It is 7.5cm length, 5cm width and 3cm
thickness. The upper part: the body (corpus), the area of insertion of each fallopian tube:
the cornu and the part of the body above the cornu: the fundus. The uterus tappers to a
small constricted area: the isthmus and below this is the cervix that projects obliquely
into the vagina. The constriction at the isthmus where the corpus joins the cervix: the
anatomical os.
The longitudinal axis is approximately at right angles to the vagina and normally tilts
forward: anteversion. The uterus is usually flexed forward on itself at the isthmus:
antiflexion. In about 20% of women the uterus tilts backwards: retroversion and
retroflexion and this have no pathological significance.
The uterus consists of 3 layers: the outer serous layer (peritoneum), the middle muscular
layer (myometrium) and the inner mucous layer (endometrium). The peritoneum covers
the body of the uterus and posteriorly the supra-vaginal part of the cervix. It is intimately
attached to a subserous fibrous layer except laterally where it spreads out to form the
leaves of the broad ligament.
The external layer of myometrium is longitudinal; the larger intermediate layer has
interlacing longitudinal, oblique and transverse fibers while the inner layer is mainly
longitudinal and circular.
The endometrium covered by a single layer of columnar epithelium, undergoes cyclic
changes during menstruation and varies in thickness from 1-5mm.
The cervix:
The cervix is narrower than the uterus, about 2.5cm length. Lateral to the cervix lies a
cellular connective tissue: parametrium, the ureter runs about 1cm laterally to the supra
vaginal cervix within the parametrium. The posterior aspect of the cervix is covered by
the peritoneum of the pouch of Douglas. Its upper part consists of involuntary muscles
while the lower part is mainly fibrous connective tissue. It has deep glandular follicles
that secrete clear alkaline mucous (main component of physiological vaginal discharge).
The cervical canal (endocervix) epithelium is columnar and also ciliated in the upper two
thirds, this change to stratified squamous epithelium around the region of the external os
and the junction of these two types of epithelium is called: sqamocolumnar junction or
transformation zone.
The fallopian tubes:
The fallopian tubes extend outwards from the cornu to end near the ovary. It runs in the
upper margin of the broad ligament (mesosalpinx), the tube is completely covered with
peritoneum except for a narrow strip along its inferior aspect. It is about 10cm length.
It has 4 parts:
1.The interstitial portion: lies within the wall of uterus.
2.The isthmus: the narrow part adjoining the uterus.
3.The ampulla: the widest and longest part.
4.The fimbrial portion (infundibulum): opens into the peritoneal cavity.
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It is surrounded by finger-like processes: the fimbria, into which the muscle coat does not
extend. The muscles of the tube are arranged in inner circular and outer longitudinal
layer. The epithelium contains 2 functional cell types: the ciliated cells (produce current
of fluid in the direction of the uterus) and secretary cells (contribute to the volume of
tubal fluid), these cells undergo changes during menstruation but no shedding occurs.
The ovaries:
The size and appearance of the ovaries depends on the age and stage of the menstrual
cycle; they are small (1.5cm) in a child, they increase to adult size at puberty due to
proliferation of stromal cells and follicle maturation (3cm length, 1cm width and 1cm
thickness). After menopause they are small with wrinkled surface since no active follicles
are present. It is the only intra-peritoneal structure not covered by peritoneum.
It is attached to the cornu of the uterus by the ovarian ligament and at the hilum to the
broad ligament by the mesovarium which contains its nerves and blood vessels. Laterally
each ovary is attached to the suspensory ligament of the ovary with folds of peritoneum
which becomes continuous with that of the psoas muscles. The part of the broad ligament
that is lateral to the fallopian tube opening: infundibulo-pelvic fold, where the ovarian
vessels and nerves pass from the side wall of the pelvis to lie between the 2 layers of the
broad ligament.
It has a central vascular medulla (connective tissue contain elastin fibers and non-striated
muscles) and an outer thicker cortex (network of reticular fibers and fusiorm cells) with
no clear-cut demarcation between the 2 layers. The surface is covered by a single layer of
cuboidal cells (the germinal epithelium) beneath it is ill-defined layer of connective tissue
(tunica albuginea) which increase in density with age.
Vestigial structures:
Vestigial remains of the mesonephric ducts and tubules always present in young
children but are variable structures in adults. The epoophoron: a series of parallel blind
tubules lie in the broad ligament between the mesovarium and fallopian tube. The
paroophoron: a few rudimentary tubules situated in the broad ligament between the
epoophoron and the uterus. The duct of Gartner: is the caudal part of the mesonephric
duct, it runs alongside the uterus to the internal os.
The pelvic muscles, ligaments and fascia:
The pelvic diaphragm:
The pelvic diaphragm is formed by the levator ani muscles: broad and flat muscles with
their fibers passing downwards and inwards constituting the pelvic diaphragm. They arise
by linear origin from:
1.Lower part of the body of the os pubis.
2.Internal surface of parietal pelvic fascia along the white line.
3.Pelvic surface of ischial spine.
They are inserted into:
1.The perineal raphe and central point of the perineum where one muscle meets the other
on the opposite side.
2.The wall of the anal canal where the fibers blend with the deep external sphincter
muscles.
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3.The postanal or anococcygeal raphe where one muscle meets the other on the opposite
side.
4.The lower part of the coccyx.
The muscle is described in two parts:
1.The pubococcygeus: arise from pubic bone and the anterior part of the tendinous part of
the pelvic fascia (white line).
2.The iliococcygeus: arise from the posterior part of the tendinous arch and the ischial
spine.
The medial border of pubococcygeus muscle pass from either side from pubic bone to the
preanal raphe embracing the vagina and on contraction have some sphincteric action.
These muscles support pelvic and abdominal viscera including the bladder, their medial
edge pass beneath the bladder and laterally to the urethra where some of its fibers
inserted forming a loop maintaining the angle between the posterior aspect of the urethra
and bladder base which, during micturition, relaxes to allow the bladder neck and upper
urethra to open and descend.
Urogenital diaphragm (triangular ligament):
Urogenital diaphragm is made up of two layers of pelvic fascia which fill the gap
between the descending pubic rami and lies beneath levator ani muscles. The deep
transverse perineal muscles lie between the two layers and the diaphragm is pierced by
the urethra and vagina.
The perineal body:
This is a mass of muscular tissue lies between the anal canal and lower third of the
vagina, its apex is at the lower end of the rectovaginal septum where the rectum and
posterior vaginal walls come in contact and its base extends from the fourchette to the
anus and covered with skin. It is the point of insertion of the superficial perineal muscles
and bounded above by levator ani muscles where they come into contact in the midline
between posterior vaginal wall and rectum.
The pelvic peritoneum:
Anteriorly, the uterus is covered with peritoneum only as far as the level of internal os,
below this it is reflected onto the bladder forming the uterovescical pouch. The
supravaginal cervix below this is separated from the bladder by connective tissue. The
uterus is completely covered with peritoneum except a narrow area laterally where the
peritoneum sweeps to form the broad ligament. Posteriorly the peritoneum covers the
posterior surface of cervix and upper third of posterior vaginal wall forming the anterior
boundary of the rectovaginal pouch of Douglas then reflects to the rectum where the front
and sides are covered by the peritoneum of rectovaginal pouch of Douglas, the middle
third only the front is covered and the lower third, no peritoneal covering and the rectum
is separated from the vagina by rectovaginal fascial septum.
The peritoneum is reflected from the lateral borders of the uterus to form on either side a
double fold of peritoneum: broad ligament (it is not a ligament but a peritoneal fold and
does not support the uterus).
The ovarian ligament: lies beneath the posterior layer of the broad ligament from the
medial pole of the ovary to the uterus just below the point of entry of fallopian tubes.
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The round ligament: is the continuation of the same structure and runs forward under the
anterior leaf of peritoneum to enter the inguinal canal ending in the subcutaneous tissue
of labia majora.
The pelvic fascia:
The parietal pelvic fascia lines the wall of the pelvic cavity covering obturator and
pyramidalis muscles. There is a thick tendinous arch on the side wall of the pelvis (white
line) from which levator ani muscles arises and cardinal ligaments gain lateral
attachment. It forms the upper layer of the urogenital diaphragm.
Important parts of visceral fascia:
The cardinal ligaments (transverse cervical ligaments): are 2 strong fan-shaped
fibromuscular bands passes from the cervix and vaginal vault to the side wall of the
pelvis; they provide the essential support of the uterus and vaginal vault.
The utero-sacral ligaments: run from the cervix and vaginal vault to the sacrum.
The bladder is supported laterally by condensation of visceral pelvic fascia on each side
and by a sheet of pubocervical fascia which lies beneath it.
Pelvic blood supply:
1.The ovarian artery arise from the aorta below the renal artery (because the ovary
develops on the posterior abdominal wall and later migrates to the pelvis, it carries its
blood supply from the abdominal aorta). The artery divides into branches that supply the
ovary and tube and then anastomoses with the terminal branches of uterine artery.
2.The internal iliac artery begins at the bifurcation of the common iliac artery, divides to
anterior and posterior branches: the branches that supply the pelvic organs are all from
the anterior division.
a.The uterine artery provides main blood supply of the uterus, from the base of the broad
ligament it runs to the upper part of the uterus to anastomose with ovarian artery, in this
part it send many branches into the substance of the uterus. Also supply branches to the
ureter, cervix and upper vagina.
b.The vaginal artery supply the vagina.
c.The vescical arteries supply the bladder and terminal ureter.
d.The middle rectal artery arise in common with the lowest vescical artery.
e.The pudendal artery which leaves the pelvic cavity through the sciatic foramen entering
the ischiorectal fossa giving the inferior rectal artery, its terminal branches supply the
perineal and vulval arteries.
3.The superior rectal artery: a continuation of inferior mesenteric artery that descends in
the base of the mesocolon, divides into two branches supply the rectum.
The pelvic veins:
Venous drainage from uterine, vaginal and vescical plexus is chiefly into the internal iliac
veins. Venous drainage from rectal plexus is via superior rectal veins to the inferior
mesenteric veins, and the middle and inferior rectal veins to the internal pudendal and
then to iliac veins.
The ovarian veins begins in the pumpiniform plexus between the broad ligament layers,
the right vein ends in the inferior vena cava and the left in the left renal vein.
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The pelvic lymphatics:
Lymphatic drainage from lower extremities, vulva and perineal regions is filtered through
inguinal and superficial femoral nodes then along the deep pathway on the side wall of
the pelvis lateral to major blood vessels forming the external iliac, common iliac and
para-aortic group of nodes. Medially, another chain passes from the deep femoral nodes
through femoral canal to obturator and internal iliac groups. The last group receives
lymphatic from upper vagina, cervix and body of uterus.
From the internal and common iliac nodes to para-aortic chain and into the lumbar
lymphatic trunks and cisterna chyli where all the lymph is carried by the thoracic duct to
empty into the junction of left subclavian and internal jugular veins (tumor cells bypass
the pelvic or para-aortic nodes and disseminate via the great veins at the root of the neck).
Lymphatic drainage from the genital tract:
The vulva and perineum medial to labio-crural skin fold lymphatic pass towards mons
pubis to superficial and inguinal nodes which drain into deep femoral nodes (the largest
one of them lie in the upper part of the femoral canal: the node of Cloquet). The lower
third of the vagina drains to the superficial lymph nodes while upper two thirds join the
lymphatics of the cervix.
The cervix mostly drains to the internal iliac, obturator and external iliac nodes, but also
directly to common iliac and lower para-aortic nodes.
Most of the lymphatics of the body of uterus join those of cervix with similar nodes. A
few vessels from the fundus follow ovarian vessels and others along the round ligament
to inguinal nodes.
The ovaries and fallopian tubes drain to para-aortic nodes, on the left they are found
around left renal pedicle while on the right they flow into thoracic duct (early spread of
metastatic carcinoma).
Nerve supply of vulva and perineum:
The pudendal nerve arise from the second, third and fourth sacral nerves, passes along the
outer wall of ischio-rectal fossa gives the inferior rectal branch and divides into perineal
nerve and dorsal nerve of clitoris. The perineal nerve gives the sensory supply of the
vulva and also the anterior part of external anal canal, levator ani and superficial perineal
muscles. The ilioinguinal and genitofemoral nerves supply sensory fibers to mons and
labia and to first lumbar root. The posterior femoral cutaneous nerve carries sensation
from perineum to the small sciatic nerve and thus to the first, second and third sacral
nerves. Levator ani main supply is from third and fourth sacral nerves.
Nerve supply of pelvic viscera:
All pelvic viscera receive sympathetic and parasympathetic innervations. Sympathetic
nerves from preaortic plexus continue with those of superior hypogastric plexus which
lies in front of the last lumbar vertebra which then divide and continue on each side with
fibers passing beside the rectum to join inferior hypogastric (uterovaginal) plexus.
Parasympathetic fibers from second, third and fourth sacral nerves join uterovaginal
plexus. Fibers from (or to) bladder, uterus, vagina and rectum join the plexus.
The ovaries innervated by the ovarian plexus which surrounds the ovarian vessels and
join the preaortic plexus high up.
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