1. Female reproductive system. Structure,
position and function of ovary. Uterus, development,
shape, parts, structure and topography. Uterine tubes
2. Structure and topography of vagina, external
reproductive organs and urethra. Topography of small pelvis organs on female
3. Perineal muscles and fasciae on male and female.
Radiograph anatomy of urinary and reproductive organs
Lesson No 17
Theme 1.
Female reproductive system. Structure,
position and function of ovary. Uterus, development,
shape, parts, structure and topography. Uterine tubes.
Genital
Glands. The first appearance of the genital gland is
essentially the same in the two sexes, and consists in a thickening of the
epithelial layer which lines the peritoneal cavity on the medial side of the
urogenital fold. The thick plate of epithelium extends deeply, pushing before
it the mesoderm and forming a distinct projection. This is termed the genital ridge, and from it the testis
in the male and the ovary in the female are developed. At first the mesonephros and genital ridge are suspended by a common
mesentery, but as the embryo grows the genital ridge gradually becomes pinched
off from the mesonephros, with which it is at first
continuous, though it still remains connected to the remnant of this body by a
fold of peritoneum, the mesorchium
or mesovarium. About the seventh week the
distinction of sex in the genital ridge begins to be perceptible.
The Ovary.—The
ovary, thus formed from the genital ridge, is at first a mass of cells derived
from the celomic epithelium; later the mass is
differentiated into a central part or medulla covered by a surface layer, the germinal epithelium. Between the cells
of the germinal epithelium a number of larger cells, the primitive ova, are found, and these are carried into the subjacent stroma by bud-like ingrowths (genital cords) of the germinal epithelium. The surface epithelium
ultimately forms the permanent epithelial covering of this organ; it soon loses
its connection with the central mass, and a tunica albuginea
develops between them. The ova are chiefly derived from the cells of the
central mass; these are separated from one another by the growth of connective
tissue in an irregular manner; each ovum assumes a covering of connective
tissue (follicle) cells, and in this way the rudiments of the ovarian follicles
are formed. According to Beard the primitive ova are early set apart during the
segmentation of the ovum and migrate into the germinal ridge.
Waldeyer
taught that the primitive germ cells are derived from the “germinal
epithelium,” covering the genital ridge. Beard, on the other hand, maintains
that in the skate they are not derived from this epithelium, but are probably
formed during the later stages of cell cleavage, before there is any trace of
an embryo; and a similar view was advanced by Nussbaum as to their origin in amphibia. Beard says: “At the close of segmentation many of
the future germ cells lie in the segmentation cavity just beneath the site of
the future embryo, and there is no doubt they subsequently wander into it.” The
germ cells, “after they enter the resting phase, are sharply marked off from
the cells of the embryo by entire absence of mitoses among them.” They can be
further recognized by their irregular form and ameboid
processes, and by the fact that their cytoplasm has no affinity for ordinary
stains, but assumes a brownish tinge when treated by
osmic acid. The path along which they travel into the embryo is a very definite
one, viz., “from the yolk sac upward between the splanchnopleure
and gut in the hinder portion of the embryo.” This pathway, named by Beard the germinal path, “leads them directly to
the position which they ought finally to take up in the `germinal ridge' or nidus.” A considerable number apparently never reach their
proper destination, since “vagrant germ cells are found in all sorts of places,
but more particularly on the mesentery.” Some of these may possibly find their
way into the germinal ridge; some probably undergo atrophy, while others may
persist and become the seat of dermoid tumors.
Descent of the
Ovaries. In the female there is also a gubernaculum, which
effects a considerable change in the position of the ovary, though not so
extensive a change as in that of the testis. The gubernaculum in the female
lies in contact with the fundus of the uterus and contracts adhesions to this
organ, and thus the ovary is prevented from descending below this level. The
part of the gubernaculum between the ovary and the uterus becomes ultimately
the proper ligament of the ovary, while the part between the uterus and the
labium majus forms the round ligament of the uterus.
A pouch of peritoneum analogous to the saccus vaginalis in the male accompanies it along the inguinal
canal: it is called the
Fallopian tubes. The fallopian tubes are about
Uterus
The uterus is a hollow cavity about the size of a pear
(in women who have never been pregnant) that exists to house a developing fertilised egg. The main part of the uterus (which sits in
the pelvic cavity) is called the body of the uterus, while the rounded region
above the entrance of the fallopian tubes is the fundus and its narrow outlet,
which protrudes into the vagina, is the cervix.
The thick wall of the uterus is
composed of 3 layers. The inner layer is known as the endometrium. If an egg
has been fertilised it will burrow into the
endometrium, where it will stay for the rest of its growth. The uterus will
expand during a pregnancy to make room for the growing fetus. A part of the
wall of the fertilised egg, which has burrowed into
the endometrium, develops into the placenta. If an egg has not been fertilised, the endometrial lining is shed at the end of
each menstrual cycle.
The myometrium is the large middle
layer of the uterus, which is made up of interlocking groups of muscle. It
plays an important role during the birth of a baby, contracting rhythmically to
move the baby out of the body via the birth canal (vagina).
Uterus
"Hystera" and
"Uterine" redirect here. For the state of mind, see hysteria.
"Womb"
The uterus (from Latin
"uterus", plural uteri) or womb is a major female
hormone-responsive reproductive sex organ of most mammals including humans.
One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species. Two
uteri usually form initially in a female fetus, and in placental mammals they
may partially or completely fuse into a single uterus depending on the species.
In many species with two uteri, only one is functional. Humans and other higher
primates usually have a single completely
fused uterus, although in some individuals the uteri may not have completely
fused. In English, the term uterus is
used consistently within the medical and related professions, while the Germanic-derived
term womb is more common in everyday usage.
The uterus consists of a body and a cervix. The cervix protrudes into the vagina. The uterus is held in position within the pelvis
by condensations of endopelvic fascia, which are
called ligaments. These ligaments include the pubocervical,
transverse. cervical ligaments cardinal ligaments,
and the uterosacral ligaments. It is covered by a sheet-like
fold of peritoneum, the broad ligament.[2]
The uterus is essential in sexual response by directing blood flow to
the pelvis and to the external genitalia, including the ovaries, vagina, labia, and
clitoris.
The reproductive function of the uterus
is to accept a fertilized ovum which passes through
the utero-tubal
junction from the fallopian tube. It implants into the endometrium, and derives nourishment from
blood vessels which develop exclusively for this purpose. The fertilized ovum
becomes an embryo, attaches to a wall of the uterus, creates a placenta, and
develops into a fetus (gestates) until childbirth. Due to anatomical barriers such
as the pelvis, the uterus is pushed partially into
the abdomen due to its expansion during pregnancy. Even during pregnancy the
mass of a human uterus amounts to only about a kilogram (
Humans may have a bicornuate uterus, a uterine malformation where the two parts of
the uterus fail to fuse completely during fetal development.
The uterus is located inside the pelvis immediately dorsal
(and usually somewhat rostral)
to the urinary bladder
and ventral to the rectum. The human uterus is pear-shaped and about
Regions
From outside to inside, the path to the uterus is as
follows:
·
Cervix uteri - "neck of uterus"
o
External
orifice of the uterus
o
Internal
orifice of the uterus
·
corpus uteri - "Body of
uterus"
o
Cavity
of the body of the uterus
Layers
The three layers, from innermost to outermost, are as
follows:
The lining of the uterine cavity is called the "endometrium". It consists of the functional endometrium and the basal endometrium from which the former arises. Damage to the basal endometrium results in adhesion formation and/or fibrosis (Asherman's syndrome
). In all placental mammals, including humans, the endometrium builds a lining periodically which is shed or reabsorbed if no pregnancy occurs. Shedding of the functional endometrial lining is responsible for menstrual bleeding (known colloquially as a "period" in humans, with a cycle of approximately 28 days, +/-7 days of flow and +/-21 days of progression) throughout the fertile years of a female and for some time beyond. Depending on the species and attributes of physical and psychological health, weight, environmental factors of circadian rhythm, photoperiodism (the physiological reaction of organisms to the length of day or night), the effect of menstrual cycles to the reproductive function of the uterus is subject to hormone production, cell regeneration and other biological activities. The menstrual cycles may vary from a few days to six months, but can vary widely even in the same individual, often stopping for several cycles before resuming. Marsupials and monotremes do not have menstruation.The uterus mostly consists of smooth muscle, known as
"myometrium." The innermost layer of myometrium is known as the junctional zone, which becomes thickened in adenomyosis.
The loose connective tissue around the
uterus.
Support
The uterus is primarily supported by the
pelvic diaphragm, perineal body and the urogenital
diaphragm. Secondarily, it is supported by ligaments and the
peritoneum (broad ligament
of uterus)
Axes
Normally the uterus lies in anteversion
& anteflexion. Anteversion
is a forward angle between the axis of the cervix and that of the vagina
measuring about 90 degrees, provided the urinary bladder and the rectum are
empty. Anteflexion is a forward angle between the
body and cervix at the isthmus measuring about 125 degrees, provided the
bladder and rectum are empty.
Major ligaments
It is held in place by several peritoneal ligaments, of which the following are the most important (there are two of each):
|
Name |
From |
To |
|
Posterior cervix |
Anterior face of sacrum |
|
|
Side of the cervix |
||
|
Side of the cervix |
Position
The uterus is in the middle of the
pelvic cavity in frontal plane
(due to ligamentum latum uteri).
The fundus does not surpass the linea terminalis, while
the vaginal part of the cervix does not extend below interspinal
line. The uterus is
mobile and moves under the pressure of the full bladder or full rectum
anteriorly, whereas if both are full it moves upwards. Increased intraabdominal pressure pushes it downwards. The mobility
is conferred to it by musculo-fibrous apparatus that
consists of suspensory and sustentacular part. Under
normal circumstances the suspensory part keeps the uterus in anteflexion and anteversion (in
90% of women) and keeps it "floating" in the pelvis. The meaning of these terms are described below:
|
Distinction |
More common |
Less common |
|
Position tipped |
"Anteverted": Tipped forward |
": Tipped backwards |
|
"Anteflexed":
Fundus is pointing forward relative to the cervix |
The pathological changes of the position of the
uterus are:
·
retroversion/retroflexion,
if it is fixed
·
hyperanteflexion - tipped too
forward; most commonly congenital, but may be caused by tumors
·
elevation, descensus,
prolapse
The uterus is
supplied by arterial blood both from the uterine
artery and the ovarian
artery.
Nerve Supply
Development
The Mammæ (Mammary Gland; Breasts)
The mammæ secrete the milk, and are
accessory glands of the generative system. They exist in the male as well as in
the female; but in the former only in the rudimentary state, unless their
growth is excited by peculiar circumstances. In the female they are two large
hemispherical eminences lying within the superficial fascia and situated on the
front and sides of the chest; each extends from the second rib above to the
sixth rib below, and from the side of the sternum to near the midaxillary line. Their weight and dimensions differ at
different periods of life, and in different individuals. Before puberty they
are of small size, but enlarge as the generative organs become more completely
developed. They increase during pregnancy and especially after delivery, and
become atrophied in old age. The left mamma is generally a little larger than
the right. The deep surface of each is nearly circular, flattened, or slightly
concave, and has its long diameter directed upward and lateralward
toward the axilla; it is separated from the fascia covering the Pectoralis major, Serratus
anterior, and Obliquus externus
abdominis by loose connective tissue. The
subcutaneous surface of the mamma is convex, and presents, just below the
center, a small conical prominence, the papilla.
The Mammary Papilla or Nipple (papilla mammæ)
is a cylindrical or conical eminence situated about the level of the fourth
intercostal space. It is capable of undergoing a sort of erection from
mechanical excitement, a change mainly due to the contraction of its muscular
fibers. It is of a pink or brownish hue, its surface wrinkled and provided with
secondary papillæ; and it is perforated by from
fifteen to twenty orifices, the apertures of the lactiferous ducts. The base of
the mammary papilla is surrounded by an areola. In the virgin the areola is of
a delicate rosy hue; about the second month after impregnation it enlarges and
acquires a darker tinge, and as pregnancy advances it
may assume a dark brown or even black color. This color diminishes as soon as
lactation is over, but is never entirely lost throughout life. These changes in
the color of the areola are of importance in forming a conclusion in a case of
suspected first pregnancy. Near the base of the papilla, and upon the surface
of the areola, are numerous large sebaceous glands, the areolar glands, which
become much enlarged during lactation, and present the appearance of small
tubercles beneath the skin. These glands secrete a peculiar fatty substance,
which serves as a protection to the integument of the papilla during the act of
sucking. The mammary papilla consists of numerous vessels, intermixed with
plain muscular fibers, which are principally arranged in a circular manner
around the base: some few fibers radiating from base to apex.
Development.—The mamma is developed partly from
mesoderm and partly from ectoderm—its bloodvessels
and connective tissue being derived from the former, its cellular elements from
the latter. Its first rudiment is seen about the third month,
in the form of a number of small inward projections of the ectoderm, which
invade the mesoderm; from these, secondary tracts of cellular elements radiate
and subsequently give rise to the epithelium of the glandular follicles
and ducts. The development of the follicles, however, remains imperfect, except
in the parous female.
Structure—The mamma consists of gland tissue;
of fibrous tissue, connecting its lobes; and of fatty tissue in the intervals
between the lobes. The gland tissue, when freed from fibrous tissue and fat, is
of a pale reddish color, firm in texture, flattened from before backward and
thicker in the center than at the circumference. The subcutaneous surface of
the mamma presents numerous irregular processes which project toward the skin
and are joined to it by bands of connective tissue. It consists of numerous
lobes, and these are composed of lobules, connected together by areolar tissue,
bloodvessels, and ducts. The smallest lobules consist
of a cluster of rounded alveoli, which open into the smallest branches of the
lactiferous ducts; these ducts unite to form larger ducts, and these end in a
single canal, corresponding with one of the chief subdivisions of the gland.
The number of excretory ducts varies from fifteen to twenty; they are termed
the tubuli lactiferi. They
converge toward the areola, beneath which they form dilatations or ampullæ, which serve as reservoirs for the milk, and,
at the base of the papillæ, become contracted,
and pursue a straight course to its summit, perforating it by separate orifices
considerably narrower than the ducts themselves. The ducts are composed of
areolar tissue containing longitudinal and transverse elastic fibers; muscular
fibers are entirely absent; they are lined by columnar epithelium resting on a
basement membrane. The epithelium of the mamma differs according to the state
of activity of the organ. In the gland of a woman who is not pregnant or
suckling, the alveoli are very small and solid, being filled with a mass of
granular polyhedral cells. During pregnancy the alveoli enlarge, and the cells
undergo rapid multiplication. At the commencement of lactation, the cells in
the center of the alveolus undergo fatty degeneration, and are eliminated in
the first milk, as colostrum corpuscles. The peripheral cells of the alveolus
remain, and form a single layer of granular, short columnar cells, with
spherical nuclei, lining the basement membrane. The cells, during the state of
activity of the gland, are capable of forming, in their interior, oil globules,
which are then ejected into the lumen of the alveolus, and constitute the milk
globules. When the acini are distended by the
accumulation of the secretion the lining epithelium becomes flattened.
The fibrous tissue invests the entire surface of the mamma,
and sends down septa between its lobes, connecting them together.
The fatty tissue covers the surface of the gland, and
occupies the interval between its lobes. It usually exists in considerable
abundance, and determines the form and size of the gland. There is no fat
immediately beneath the areola and papilla.
Vessels and Nerves.—The arteries supplying the mammæ are derived from the thoracic branches of the
axillary, the intercostals, and the internal mammary.
The veins describe an anastomotic circle around the base of the papilla, called
by Haller the circulus venosus.
From this, large branches transmit the blood to the circumference of the gland,
and end in the axillary and internal mammary veins. The nerves are derived from
the anterior and lateral cutaneous branches of the fourth, fifth, and sixth
thoracic nerves.
FEMALE
GENITAL ORGANS are subdivided into
§ internal
female sexual organs:
Ovaries, uterine tubes, uterus and vagina
§ external
female genital organs:
Pudendal area with labia pudenda majora and labia
pudenda minora, vestibule of vagina, clitoris and mons pubis.
The Ovary
is a pair organ, is situated in cavity of lesser pelvis. It has medial
surface and lateral surface, free margin and mesenteric margin,
uterine extremity and tubarius
extremity. Ovary is situated in peritoneal cavity,
it is covered by embryonic epithelium (not by peritoneum). Ovary attaches to
uterus by proper ovaric ligament, and
to pelvis walls - by the medium of suspensory ovaric
ligament. Ovaric mesentery approaches to
anterior margin, through which the vessels and nerves get into ovary hilus. Ovary parenchyma consists of cortex and medulla.
Ovule ripens in cortex, where primary folliculi
are situated, which then transforms into Graaf
vesicle. After that as vesicle blowes up, an oocyte
gets out from the ovary and gets into uterine tube. Vesicle becomes as corpus
luteum [yellow body]. If there is not
fecundation, then corpus luteum transform into corpus
albicans. In case of fecundation corpus luteum grows up and turns into corpus luteum verum, which functions
during pregnancy.
Uterus and right broad ligament, seen
from behind. The broad ligament has been spread
out and the ovary drawn downward.
The ovaries are homologous with the testes in the male. They are
two nodular bodies, situated one on either side of the uterus in relation to
the lateral wall of the pelvis, and attached to the back of the broad ligament
of the uterus, behind and below the uterine tubes. The ovaries are of a grayish-pink color, and present
either a smooth or a puckered uneven surface. They are each about
Adult ovary, epoöphoron, and uterine tube. (From Farre, after Kobelt.) a, a.
Epoöphoron formed from the upper part of the Wolffian body. b. Remains of the uppermost tubes
sometimes forming hydatids. c. Middle set of
tubes. d. Some lower atrophied tubes. e. Atrophied remains of the
Wolffian duct. f. The terminal bulb or hydatid. h. The uterine tube. i.
Hydatid attached to the extremity. l. The
ovary.
Epoöphoron (parovarium; organ of Rosenmüller) lies
in the mesosalpinx between the ovary and the uterine
tube, and consists of a few short tubules (ductuli
transversi) which converge toward the ovary while
their opposite ends open into a rudimentary duct, the ductus
longitudinalis epoöphori
(duct of Gärtner).
Paroöphoron.—The paroöphoron
consists of a few scattered rudimentary tubules, best seen in the child,
situated in the broad ligament between the epoöphoron
and the uterus.
The ductuli transversi
of the epoophoron and the tubules of the paroophoron are remnants of the tubules of the Wolffian body or mesonephros; the
ductus longitudinalis epoöphori is a persistent portion of the Wolffian duct.
In the fetus the ovaries are
situated, like the testes, in the lumbar region, near the kidneys, but they
gradually descend into the pelvis.
Section of the ovary. (After Schrön.) 1.
Outer covering.
Structure. The surface of the ovary is covered by a
layer of columnar cells which constitutes the germinal epithelium of Waldeyer. This epithelium gives to the ovary a dull gray color as compared with the
shining smoothness of the peritoneum; and the transition between the squamous
epithelium of the peritoneum and the columnar cells which cover the ovary is
usually marked by a line around the anterior border of the ovary. The ovary consists
of a number of vesicular ovarian follicles imbedded in the meshes of a stroma or frame-work.
The stroma is a peculiar
soft tissue, abundantly supplied with bloodvessels,
consisting for the most part of spindle-shaped cells with a small amount of ordinary
connective tissue. These cells have been regarded by some anatomists as unstriped muscle cells, which, indeed, they most resemble;
by others as connective-tissue cells. On the surface of the organ this tissue
is much condensed, and forms a layer (tunica albuginea)
composed of short connective-tissue fibers, with
fusiform cells between them. The stroma of the ovary
may contain interstitial cells resembling those of the testis.
Vesicular Ovarian Follicles (Graafian
follicles).—Upon making a section of an ovary,
numerous round transparent vesicles of various sizes are to be seen; they are
the follicles, or ovisacs containing the ova.
Immediately beneath the superficial covering is a layer of stroma,
in which are a large number of minute vesicles, of uniform size, about
The larger follicles consist of an external fibrovascular coat, connected with the surrounding stroma of the ovary by a net-work of bloodvessels;
and an internal coat, which consists of several layers of nucleated cells,
called the membrana granulosa.
At one part of the mature follicle the cells of the membrana
granulosa are collected into a mass which projects
into the cavity of the follicle. This is termed the discus proligerus, and in it the ovum is imbedded. The follicle contains a transparent albuminous
fluid.
The development and maturation of the follicles and ova continue
uninterruptedly from puberty to the end of the fruitful period of woman’s life,
while their formation commences before birth. Before puberty the ovaries are
small and the follicles contained in them are disposed in a comparatively thick
layer in the cortical substance; here they present the appearance of a large
number of minute closed vesicles, constituting the early condition of the
follicles; many, however, never attain full development, but shrink and
disappear. At puberty the ovaries enlarge and become more vascular, the
follicles are developed in greater abundance, and their ova are capable of
fecundation.
Section of vesicular ovarian follicle
Discharge of the Ovum.—The follicles, after
attaining a certain stage of development, gradually approach the surface of the
ovary and burst; the ovum and fluid contents of the follicle are liberated on
the exterior of the ovary, and carried into the uterine tube by currents set up
by the movements of the cilia covering the mucous membrane of the fimbriae.
Corpus Luteum.—After
the discharge of the ovum the lining of the follicle is thrown into folds, and
vascular processes grow inward from the surrounding tissue. In this way the
space is filled up and the corpus luteum formed. It
consists at first of a radial arrangement of yellow cells with bloodvessels and lymphatic spaces, and later it merges with
the surrounding stroma.
Vessels and Nerves.—The arteries of
the ovaries and uterine tubes are the ovarian from the aorta. Each anastomoses
freely in the mesosalpinx, with the uterine artery,
giving some branches to the uterine tube, and others which traverse the mesovarium and enter the hilum of the ovary. The veins
emerge from the hilum in the form of a plexus, the pampiniform
plexus; the ovarian vein is formed from this plexus, and leaves the pelvis
in company with the artery. The nerves are derived from the hypogastric or pelvic plexus, and from the ovarian plexus,
the uterine tube receiving a branch from one of the uterine nerves.
The ovaries are homologous with the testes in the male. They are
two nodular bodies, situated one on either side of the uterus in relation to
the lateral wall of the pelvis, and attached to the back of the broad ligament
of the uterus, behind and below the uterine tubes. The ovaries are of a grayish-pink color, and present
either a smooth or a puckered uneven surface. They are each about
Adult
ovary, epoöphoron, and uterine tube. (From Farre, after Kobelt.) a, a.
Epoöphoron formed from the upper part of the Wolffian body. b. Remains of the uppermost tubes
sometimes forming hydatids. c. Middle set of
tubes. d. Some lower atrophied tubes. e. Atrophied remains of the
Wolffian duct. f. The terminal bulb or hydatid. h. The uterine tube. i.
Hydatid attached to the extremity. l. The
ovary.
Epoöphoron (parovarium; organ of Rosenmüller) lies
in the mesosalpinx between the ovary and the uterine
tube, and consists of a few short tubules (ductuli
transversi) which converge toward the ovary while
their opposite ends open into a rudimentary duct, the ductus
longitudinalis epoöphori
(duct of Gärtner).
The Uterine
tube is a pair organ is situated in area of superior margin of ligamentum latum uteri.
Length of each tube is 8-
§ uterine
part runs in wall of uterus and opens into uterine cavity
by uterine ostium;
§ isthmus
of uterine tube lies closely to uterus;
§ ampulla
of uterine tube is greater part of uterine tube;
§ infundibulum
of uterine tube - is broadened part, which opens by abdominal foramen of
uterine tube into abdominal (peritoneal) cavity and covered by fimbria,
one of which - ovaric fimbria is longer
then other.
Uterine
tube is covered from all sides by peritoneum and has its own mesentery.
Tube has also muscular membrane (longitudinal and circular layers) and mucous
membrane. Fecundation realizes in uterine tube normally, than fertilized
ovule passes into uterus.
Female pelvis and its contents, seen from above and in front.
The Uterus
is an odd hollow organ, pear-shaped object, which is situated in cavity of
lesser pelvis. It has a fundus, body and neck of uterus, which
opens into vagina by uterine ostium, limited
by anterior labium and posterior labium. Uterine neck divided
into supravaginal portion and
vaginal portion. Uterine body has vesical surface
(anterior) and intestinal surface (posterior). Place of transition body of
uterus into neck is called as isthmus. Anterior uterus surface adjoins to
urinary bladder, and posterior - to rectum. Attached to empty urinary bladder
body of uterus is tilted forward. Such position is called anteversio.
Attached to full urinary bladder a fundus and uterus body displaces posteriorly
– this is retroversio. Also between body and
uterus neck is formed a angle, open forward. Such
position is called anteflexio.
Triangle-shaped cavity of uterus above communicate with uterine tubes,
and vagina through the cervical canal and ostium
uteri.
Wall of uterus
consists of three layers:
• mucous membrane (endometrium), submucous
stratum is absent ,so there is no folds on internal surface of uterus;
• muscular membrane (myometrium) is formed by smooth muscle and
consists of internal, middle and external layers;
• serous membrane (perimetrium) is a
peritoneum, which covers an uterus from all sides, except part of front surface
and lateral margins and supravaginal portion of neck
(mesoperitoneal position). Serous membrane
forms ligamentum uteri latum,
which forms mesentery of uterus, mesentery of ovary and mesentery of uterine
tube. Between sheets of ligamentum latum uteri the vessels, nerves, adipose tissue (parametrium) and ligamentum teres uteri are contained. Ligamentum
teres [round] uteri passes through the
inguinal canal to pubis. Also uterus is fixed to pelvic walls by cardinal
ligament.
The uterus is a hollow, thick-walled, muscular organ situated
deeply in the pelvic cavity between the bladder and rectum. Into its upper part
the uterine tubes open, one on either side, while below, its cavity
communicates with that of the vagina. When the ova are discharged from the
ovaries they are carried to the uterine cavity through the uterine tubes. If an
ovum be fertilized it imbeds itself in the uterine wall and is normally
retained in the uterus until prenatal development is completed, the uterus
undergoing changes in size and structure to accommodate itself to the needs of
the growing embryo (see page 59). After parturition the uterus returns almost
to its former condition, but certain traces of its enlargement remains. It is
necessary, therefore, to describe as the type-form the adult virgin uterus, and
then to consider the modifications which are effected as a result of pregnancy.
Sagittal section of the lower part of a female trunk, right segment. SM.
INT. Small intestine
In the virgin state the uterus is flattened antero-posteriorly and is pyriform
in shape, with the apex directed downward and backward. It lies between the
bladder in front and the pelvic or sigmoid colon and rectum behind, and is
completely within the pelvis, so that its base is below the level of the
superior pelvic aperture. Its upper part is suspended by the broad and the
round ligaments, while its lower portion is imbedded in the fibrous tissue of
the pelvis.
The long axis of the uterus usually lies approximately in
the axis of the superior pelvic aperture, but as the organ is freely movable
its position varies with the state of distension of the bladder and rectum.
Except when much displaced by a fully distended bladder, it forms a forward
angle with the vagina, since the axis of the vagina corresponds to the axes of
the cavity and inferior aperture of the pelvis.
The uterus measures about
Body (corpus uteri).—The body
gradually narrows from the fundus to the isthmus.
The vesical or anterior
surface (facies vesicalis)
is flattened and covered by peritoneum, which is reflected on to the bladder to
form the vesicouterine excavation. The surface lies
in apposition with the bladder.
The intestinal or posterior surface (facies intestinalis)
is convex transversely and is covered by peritoneum, which is continued down on
to the cervix and vagina. It is in relation with the sigmoid colon, from which
it is usually separated by some coils of small intestine.
The fundus (fundus uteri) is convex in all
directions, and covered by peritoneum continuous with that on the vesical and intestinal surfaces. On it rest some coils of
small intestine, and occasionally the distended sigmoid colon.
The lateral margins (margo
lateralis) are slightly convex. At the upper end
of each the uterine tube pierces the uterine wall. Below and in front of this
point the round ligament of the uterus is fixed, while behind it is the
attachment of the ligament of the ovary. These three structures lie within a
fold of peritoneum which is reflected from the margin of the uterus to the wall
of the pelvis, and is named the broad ligament.
Cervix (cervix uteri; neck).—The
cervix is the lower constricted segment of the uterus. It is somewhat conical
in shape, with its truncated apex directed downward and backward, but is
slightly wider in the middle than either above or below. Owing to its relationships,
it is less freely movable than the body, so that the latter may bend on it. The
long axis of the cervix is therefore seldom in the same straight line as the
long axis of the body. The long axis of the uterus as a whole presents the form
of a curved line with its concavity forward, or in extreme cases may present an
angular bend at the region of the isthmus.
The cervix projects through the anterior wall of the vagina,
which divides it into an upper, supravaginal portion,
and a lower, vaginal portion.
The supravaginal portion
(portio supravaginalis
[cervicis]) is separated in front from
the bladder by fibrous tissue (parametrium),
which extends also on to its sides and lateralward
between the layers of the broad ligaments. The uterine arteries reach the
margins of the cervix in this fibrous tissue, while on either side the ureter
runs downward and forward in it at a distance of about
The vaginal portion (portio
vaginalis [cervicis])
of the cervix projects free into the anterior wall of the vagina between the
anterior and posterior fornices. On its rounded
extremity is a small, depressed, somewhat circular aperture, the external
orifice of the uterus, through which the cavity of the cervix communicates
with that of the vagina. The external orifice is bounded by two lips, an
anterior and a posterior, of which the anterior is the shorter and thicker,
although, on account of the slope of the cervix, it projects lower than the
posterior. Normally, both lips are in contact with the posterior vaginal wall.
Interior of the Uterus—The cavity of the
uterus is small in comparison with the size of the organ.
The Cavity of the Body (cavum
uteri) is a mere slit, flattened antero-posteriorly.
It is triangular in shape, the base being formed by the internal surface of the
fundus between the orifices of the uterine tubes, the apex by the internal
orifice of the uterus through which the cavity of the body communicates with
the canal of the cervix.
The Canal of the Cervix (canalis
cervicis uteri) is somewhat fusiform, flattened
from before backward, and broader at the middle than at either extremity. It
communicates above through the internal orifice with the cavity of the body,
and below through the external orifice with the vaginal cavity. The wall of the
canal presents an anterior and a posterior longitudinal ridge, from each of
which proceed a number of small oblique columns, the palmate folds,
giving the appearance of branches from the stem of a tree; to this arrangement
the name arbor vitae uterina
is applied. The folds on the two walls are not exactly opposed, but fit between
one another so as to close the cervical canal.
Posterior half of uterus and upper part of vagina.
The total length of the uterine cavity from the external
orifice to the fundus is about
Ligaments.—The ligaments of the uterus are eight in number:
one anterior; one posterior; two lateral or broad;
two uterosacral; and two round
ligaments.
The anterior ligament consists of the vesicouterine fold of peritoneum, which is reflected on to
the bladder from the front of the uterus, at the junction of the cervix and
body.
The posterior ligament consists of the rectovaginal fold of peritoneum, which is reflected from
the back of the posterior fornix of the vagina on to the front of the rectum.
It forms the bottom of a deep pouch called the rectouterine
excavation, which is bounded in front by the posterior wall of the uterus,
the supravaginal cervix, and the posterior fornix of
the vagina; behind, by the rectum; and laterally by two crescentic
folds of peritoneum which pass backward from the cervix uteri on either side of
the rectum to the posterior wall of the pelvis. These folds are named the sacrogenital or rectouterine
folds. They contain a considerable amount of fibrous tissue and non-striped
muscular fibers which are attached to the front of
the sacrum and constitute the uterosacral
ligaments.
The two lateral or broad ligaments (ligamentum latum uteri)
pass from the sides of the uterus to the lateral walls of the pelvis. Together
with the uterus they form a septum across the female pelvis, dividing that
cavity into two portions. In the anterior part is contained the bladder; in the
posterior part the rectum, and in certain conditions some coils of the small
intestine and a part of the sigmoid colon. Between the two layers of each broad
ligament are contained: (1) the uterine tube superiorly; (2) the round ligament
of the uterus; (3) the ovary and its ligament; (4) the epoöphoron
and paroöphoron; (5) connective tissue; (6) unstriped muscular fibers; and
(7) bloodvessels and nerves. The portion of the broad
ligament which stretches from the uterine tube to the level of the ovary is
known by the name of the mesosalpinx.
Between the fimbriated extremity of the tube and the
lower attachment of the broad ligament is a concave rounded margin, called the infundibulopelvic ligament.
The round ligaments (ligamentum
teres uteri) are two flattened bands between 10
and
In addition to the ligaments just described, there is a band
named the ligamentum transversalis
colli (Mackenrodt) on
either side of the cervix uteri. It is attached to the side of the cervix uteri
and to the vault and lateral fornix of the vagina, and is continuous externally
with the fibrous tissue which surrounds the pelvic bloodvessels.
The form, size, and situation of the uterus vary at
different periods of life and under different circumstances.
Sagittal section through the pelvis of a newly born female.
In the fetus the uterus is
contained in the abdominal cavity, projecting beyond the superior aperture of
the pelvis. The cervix is considerably larger than the body.
At puberty the uterus is pyriform
in shape, and weighs from 14 to
The position of the uterus in the adult is liable to
considerable variation, depending chiefly on the condition of the bladder and
rectum. When the bladder is empty the entire uterus is directed forward, and is
at the same time bent on itself at the junction of the body and cervix, so that
the body lies upon the bladder. As the latter fills, the uterus gradually
becomes more and more erect, until with a fully distended bladder the fundus
may be directed backward toward the sacrum.
During menstruation the organ is enlarged, more
vascular, and its surfaces rounder; the external orifice is rounded, its labia
swollen, and the lining membrane of the body thickened, softer, and of a darker
color. According to Sir J. Williams, at each
recurrence of menstruation, a molecular disintegration of the mucous membrane
takes place, which leads to its complete removal, only the bases of the glands
imbedded in the muscle being left. At the cessation of menstruation, a fresh
mucous membrane is formed by a proliferation of the remaining structures.
During pregnancy the uterus becomes enormously
enlarged, and in the eighth month reaches the epigastric
region. The increase in size is partly due to growth of preëxisting
muscle, and partly to development of new fibers.
After parturition the uterus nearly regains its usual
size, weighing about
In old age the uterus becomes atrophied, and paler
and denser in texture; a more distinct constriction separates the body and
cervix. The internal orifice is frequently, and the external orifice
occasionally, obliterated, while the lips almost entirely disappear.
Structure.—The uterus is composed
of three coats: an external or serous, a middle or muscular,
and an internal or mucous.
The serous coat (tunica serosa) is derived
from the peritoneum; it invests the fundus and the whole of the intestinal
surface of the uterus; but covers the vesical surface
only as far as the junction of the body and cervix. In the lower fourth of the
intestinal surface the peritoneum, though covering the uterus, is not closely
connected with it, being separated from it by a layer of loose cellular tissue
and some large veins.
The muscular coat (tunica muscularis)
forms the chief bulk of the substance of the uterus. In the virgin it is dense,
firm, of a grayish color,
and cuts almost like cartilage. It is thick opposite the middle of the body and
fundus, and thin at the orifices of the uterine tubes. It consists of bundles
of unstriped muscular fibers,
disposed in layers, intermixed with areolar tissue, bloodvessels,
lymphatic vessels, and nerves. The layers are three in number: external,
middle, and internal. The external and middle layers constitute the muscular
coat proper, while the inner layer is a greatly hypertrophied muscularis mucosae. During pregnancy the muscular tissue
becomes more prominently developed, the fibers being
greatly enlarged.
The external layer, placed beneath the peritoneum, is disposed
as a thin plane on the vesical and intestinal
surfaces. It consists of fibers which pass
transversely across the fundus, and, converging at each lateral angle of the
uterus, are continued on to the uterine tube, the round ligament, and the
ligament of the ovary: some passing at each side into the broad ligament, and
others running backward from the cervix into the sacrouterine
ligaments. The middle layer of fibers presents no
regularity in its arrangement, being disposed longitudinally, obliquely, and
transversely. It contains more bloodvessels than
either of the other two layers. The internal or deep layer consists of circular
fibers arranged in the form of two hollow cones, the
apices of which surround the orifices of the uterine tubes, their bases
intermingling with one another on the middle of the body of the uterus. At the
internal orifice these circular fibers form a
distinct sphincter.
The mucous membrane (tunica mucosa) is smooth,
and closely adherent to the subjacent tissue. It is continuous through the fimbriated extremity of the uterine tubes, with the
peritoneum; and, through the external uterine orifice, with the lining of the
vagina.
In the body of the uterus the mucous membrane is smooth,
soft, of a pale red color, lined by columnar ciliated
epithelium, and presents, when viewed with a lens, the orifices of numerous
tubular follicles, arranged perpendicularly to the surface. The structure of
the corium differs from that of ordinary mucous membranes, and consists of an
embryonic nucleated and highly cellular form of connective tissue in which run
numerous large lymphatics. In it are the tube-like uterine
glands, lined by ciliated columnar epithelium. They are of small size in
the unimpregnated uterus, but shortly after
impregnation become enlarged and elongated, presenting a contorted or waved
appearance (see page 60).
In the cervix the mucous membrane is sharply differentiated
from that of the uterine cavity. It is thrown into numerous oblique ridges,
which diverge from an anterior and posterior longitudinal raphé.
In the upper two-thirds of the canal, the mucous membrane is provided with
numerous deep glandular follicles, which secrete a clear viscid alkaline mucus;
and, in addition, extending through the whole length of the canal is a variable
number of little cysts, presumably follicles which have become occluded and
distended with retained secretion. They are called the ovula
Nabothi. The mucous membrane covering the lower
half of the cervical canal presents numerous papillae. The epithelium of the
upper two-thirds is cylindrical and ciliated, but below this it loses its
cilia, and gradually changes to stratified squamous epithelium close to the
external orifice. On the vaginal surface of the cervix the epithelium is
similar to that lining the vagina, viz., stratified squamous.
The arteries of the internal organs of generation of the female, seen
from behind.
Vessels and Nerves.—The arteries of
the uterus are the uterine, from the hypogastric; and
the ovarian, from the abdominal aorta.
They are remarkable for their tortuous course in the substance of the
organ, and for their frequent anastomoses. The termination of the ovarian
artery meets that of the uterine artery, and forms an anastomotic trunk from which
branches are given off to supply the uterus, their disposition being circular.
Theme 2. Structure and topography of vagina, external
reproductive organs and urethra. Topography of small pelvis organs on female.
The Vagina
is a tube of 7-
The vagina extends from the vestibule to the uterus, and is
situated behind the bladder and in front of the rectum; it is directed upward
and backward, its axis forming with that of the uterus an angle of over 90°,
opening forward. Its walls are ordinarily in contact, and the usual shape of
its lower part on transverse section is that of an H, the transverse limb being
slightly curved forward or backward, while the lateral limbs are somewhat
convex toward the median line; its middle part has the appearance of a transverse
slit. Its length is 6 to
Relations.—The anterior
surface of the vagina is in relation with the fundus of the bladder, and
with the urethra. Its posterior surface is separated from the rectum by
the rectouterine excavation in its upper fourth, and
by the rectovesical fascia in its middle two-fourths;
the lower fourth is separated from the anal canal by the perineal
body. Its sides are enclosed between the Levatores ani muscles. As the terminal portions of the ureters pass
forward and medialward to reach the fundus of the
bladder, they run close to the lateral fornices of
the vagina, and as they enter the bladder are slightly in front of the anterior
fornix.
Structure.—The vagina consists of
an internal mucous lining and a muscular coat separated by a
layer of erectile tissue.
The mucous membrane (tunica mucosa) is
continuous above with that lining the uterus. Its inner surface presents two
longitudinal ridges, one on its anterior and one on its posterior wall. These
ridges are called the columns of the vagina and from them numerous
transverse ridges or rugae extend outward on either
side. These rugae are divided by furrows of variable
depth, giving to the mucous membrane the appearance of being studded over with
conical projections or papillae; they are most numerous near the orifice of the
vagina, especially before parturition. The epithelium covering the mucous
membrane is of the stratified squamous variety. The submucous
tissue is very loose, and contains numerous large veins which by their
anastomoses form a plexus, together with smooth muscular fibers
derived from the muscular coat; it is regarded by Gussenbauer
as an erectile tissue. It contains a number of mucous crypts, but no true
glands.
The muscular coat (tunica muscularis)
consists of two layers: an external longitudinal, which is by far the stronger,
and an internal circular layer. The longitudinal fibers
are continuous with the superficial muscular fibers
of the uterus. The strongest fasciculi are those attached to the rectovesical fascia on either side. The two layers are not
distinctly separable from each other, but are connected by oblique decussating
fasciculi, which pass from the one layer to the other. In addition to this, the
vagina at its lower end is surrounded by a band of striped muscular fibers, the Bulbocavernosus
(see page 430).
External to the muscular coat is a layer of connective
tissue, containing a large plexus of bloodvessels.
The erectile tissue consists of a layer of loose
connective tissue, situated between the mucous membrane and the muscular coat;
imbedded in it is a plexus of large veins, and numerous bundles of unstriped muscular fibers,
derived from the circular muscular layer. The arrangement of the veins is
similar to that found in other erectile tissues.
Female pudendal area
The major pudenda labia limit a pudenda rima.
Right and left major pudenda labia communicate by each other by the by means of
anterior labial comissura and posterior comissura.
Minor pudendal labia are the skin folds
without adipose tissue, they lie medially from major pudenda labia. Anterior
margin of minor pudendal labia bifurcates and forms prerutium of clitoris and frenulum of
clitoris.
The Clitoris
is by length 2-З cm, is analogue of cavernous bodies of penis and consists of head,
body and legs of clitoris. The legs of clitoris attach to inferior
rami of pubic bone.
The Vestibule vaginae are a fissure between
minor pudendal labia. External urethral ostium, vaginal foramen and ducts of minor and major (Bartolini) vestibular glands open here. Bulbus
vestibuli vagina consists of cavernous tissue, which
is situated on sides from inferior vaginal end (analogue of sponges body of
penis).
Theme 3. Perineal muscles and fasciae on male and female.
Radiograph anatomy of urinary and reproductive organs
The PERINEUM
in narrow aspect is the soft tissues situated between anus and external genital. In wide understanding
a perineum is a complex of soft tissues, which close pelvic outlet.
Perineum is diamond-shaped area, which is limited by coccyx behind, by
inferior margin of pubic symphysis anteriorly and by
sciatic tuber - laterally. Perineum subdivides by line between right and left
sciatic tubers into anterior urogenital triangle and posterior anal
triangle. Anterior triangle lies in oblique frontal plane and urethra
passes through it in males, and in female - a vagina and urethra. Posterior
triangle lies in horizontal plane, is called by pelvic or anal triangle
and terminal portion of rectum passes through it.
The perineal muscles subdivide
into superficial and deep groups.
Superficial
muscles of urogenital triangle:
ü superficial
transversal perineal muscle,
which fixes a perineum;
ü bulbo-spongious muscle,
which compresses an entrance into vagina into female, and into males presses
out sperm or urine;
ü ischiocavernous muscle,
which assists erections of penis or clitoris.
Superficial
muscles of pelvic triangle
ü external
muscle-sphincter ani, which
consists of striped fibres (voluntary).
Deep muscles of perineum form urogenital and pelvic diaphragm.
Deep
muscles of urogenital triangle:
ü deep
transversal perineal muscle,
which fixes a perineum;
ü sphincter
urethrae formed by circular stripped (voluntary) fibres;
Deep
muscles of pelvic triangle
ü levator ani muscle;
ü coccygeal
muscle.
Fasciae of pelvic
area:
Pelvic fascia is continuation of iliac fascia and has a parietal sheet
and visceral sheet. Parietal pelvic fascia covers levator
ani muscle and internal obturatorius
muscle. Visceral pelvic fascia invests the rectum and other organs. Part
of parietal pelvic fasciae, which covers a levator ani muscle above is called superior fascia of pelvic
diaphragm. Inferior fascia of pelvic diaphragm covers the
levator ani muscle below. Membranous
layer limits below external sphincter ani and
ischioanal fossa.
Pelvic
diaphragm = Deep muscles + Superior fascia + Inferior fascia
The ischioanal [ischiorectal] fossa around the wall of the anal
canal are large fascia-lined, wedge-shaped space between the skin of anal
region and the pelvic diaphragm. It contains adiposal
body and pudendal canal (Alcock`s) with
nerves and vessels.
The urogenital triangle
Superior fascia of urogenital diaphragm is
continuation of pelvic fascia and covers from above deep muscles.
A thin and tough sheet, the perineal
membrane ( inferior fascia of urogenital diaphragm) stretches
between the two sides of the pubic arch and covers below the anterior part of
the pelvic outlet. The perineal membrane located
between the superficial and deep muscles. The perineal
body is a fibromuscular mass located in the
midpoint between the anal canal and perineal
membrane.
Urogenital diaphragm = Deep muscles + Superior fascia + Inferior fascia
Superficial perineal fascia
(investing fascia) intimately invests superficial muscles of urogenital
triangle. Anteriorly it is fused to the suspensory ligament of the
penis.
Subcutaneous membranous layer (stratum) passes
superior to the labia majora (in female) and in males
continuous with the dartos fascia in scrotum.
Superficial perineal pouch
(compartment) is the potential space between superficial investing fascia and perineal membrane. In males superficial perineal
pouch contains: root of the penis with associated superficial muscles, pudendal vessels and nerves. In females superficial perineal pouch contains: crura of
the clitoris and bulb of vestibule, associated with them superficial muscles, pudendal vessels and nerves, greater vestibular glands.
Deep
perineal pouch (space) is
not an enclosed compartment; it is open superiorly. This pouch is bounded below
by the perineal membrane. In males deep perineal
pouch contains: membranous part of urethra, external urethral sphincter muscle,
bulbourethral glands, deep transverse perineal
muscles, related nerves and vessels. In females the deep perineal
pouch contains the: proximal part of urethra, external urethral sphincter
muscle, deep transverse perineal muscles, related
nerves and vessels.
The perineum corresponds to the outlet of the pelvis. Its deep
boundaries are—in front, the pubic arch and the arcuate
ligament of the pubis; behind, the tip of the coccyx; and on either side
the inferior rami of the pubis and ischium, and the sacrotuberous
ligament. The space is somewhat lozenge-shaped and is limited on the surface of
the body by the scrotum in front, by the buttocks behind, and laterally by the
medial side of the thigh. A line drawn transversely across in front of the ischial tuberosities divides the
space into two portions. The posterior contains the termination of the anal
canal and is known as the anal region; the anterior, which contains the
external urogenital organs, is termed the urogenital region.
The muscles of the perineum may therefore be divided into
two groups:
1. Those of the anal region.
2. Those of the urogenital region: A, In the male; B, In the female.
The Superficial Fascia.—The superficial
fascia is very thick, areolar in texture, and contains much fat in its meshes.
On either side a pad of fatty tissue extends deeply between the Levator ani and Obturator internus into a space
known as the ischiorectal fossa.
The Deep Fascia.—The deep fascia forms
the lining of the ischiorectal fossa; it comprises
the anal fascia, and the portion of obturator fascia
below the origin of Levator ani.
Ischiorectal Fossa (fossa ischiorectalis) is somewhat prismatic in shape, with its base directed to the surface
of the perineum, and its apex at the line of meeting of the obturator
and anal fasciae. It is bounded medially by the Sphincter ani externus and the anal fascia;
laterally, by the tuberosity of the ischium and the obturator
fascia; anteriorly, by the fascia of Colles
covering the Transversus perinaei
superficialis, and by the inferior fascia of the
urogenital diaphragm; posteriorly, by the Glutaeus
maximus and the sacrotuberous
ligament. Crossing the space transversely are the inferior hemorrhoidal
vessels and nerves; at the back part are the perineal
and perforating cutaneous branches of the pudendal
plexus; while from the forepart the posterior scrotal (or labial) vessels and
nerves emerge. The internal pudendal vessels and pudendal nerve lie in Alcock’s
canal on the lateral wall. The fossa is filled with fatty tissue across which
numerous fibrous bands extend from side to side.
The perineum. The integument and superficial layer of superficial fascia
reflected.
The Sphincter ani externus (External sphincter ani)
is a flat plane of muscular fibers, elliptical in
shape and intimately adherent to the integument surrounding the margin of the
anus. It measures about 8 to
Nerve Supply.—A branch from the
fourth sacral and twigs from the inferior hemorrhoidal
branch of the pudendal supply the muscle.
Actions.—The action of this muscle is
peculiar. (1) It is, like other muscles, always in a state of tonic
contraction, and having no antagonistic muscle it keeps the anal canal and
orifice closed. (2) It can be put into a condition of greater contraction under
the influence of the will, so as more firmly to occlude the anal aperture, in
expiratory efforts unconnected with defecation. (3) Taking its fixed point at
the coccyx, it helps to fix the central point of the perineum, so that the Bulbocavernosus may act from this fixed point.
The Sphincter ani internus (Internal sphincter ani)
is a muscular ring which surrounds about
Actions.—Its action is entirely
involuntary. It helps the Sphincter ani externus to occlude the anal aperture and aids in the
expulsion of the feces.
Transversus perinaei superficialis.
Transversus perinaei profundus.
Sphincter urethrae membranaceae.
Coronal section of anterior part of pelvis, through the pubic arch. Seen
from in front. (Diagrammatic.)
Nerve Supply.—The perineal branch
of the pudendal nerve supplies this group of muscles.
Actions.—The muscles of both sides act together as a
sphincter, compressing the membranous portion of the urethra. During the
transmission of fluids they, like the Bulbocavernosus,
are relaxed, and only come into action at the end of the process to eject the
last drops of the fluid.
2. B. The
Muscles of the Urogenital Region in the Female
Transversus perinaei superficialis.
Transversus perinaei profundus.
Sphincter urethrae membranaceae.
Muscles of the female perineum.
The
Transversus perinei profundus arises from the inferior rami of the ischium and
runs across to the side of the vagina. The Sphincter urethrae membranaceae (Constrictor urethrae), like the corresponding
muscle on the male, consists of external and internal fibers. The external
fibers arise on either side from the margin of the inferior ramus of the pubis.
They are directed across the pubic arch in front of the urethra, and pass
around it to blend with the muscular fibers of the opposite side, between the
urethra and vagina. The innermost fibers encircle the lower end of the urethra.