Download Development of the Inguinal Canal

INGUINAL CANAL
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Is an oblique passage
through the lower part of the
anterior abdominal wall and
is present in both sexes.
It allows structures to pass
to and from the testis to the
abdomen in males.
In females it permits the
passage of the round
ligament of the uterus from
the uterus to the labium
majus.
In addition, it transmits the
ilioinguinal nerve in both
sexes.
INGUINAL CANAL
INGUINAL CANAL
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The canal is about (4 cm) long in
the adult and extends from the
deep inguinal ring downward and
medially to the superficial inguinal
ring.
It lies parallel to and immediately
above the inguinal ligament.
In the newborn child, the deep ring
lies almost directly posterior to the
superficial ring so that the canal is
considerably shorter at this age.
Later, as the result of growth, the
deep ring moves laterally.
INGUINAL CANAL
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The deep inguinal ring, an oval
opening in the fascia transversalis,
lies about (1.3 cm) above the
inguinal ligament midway between
the anterior superior iliac spine and
the symphysis pubis.
Related to it medially are the
inferior epigastric vessels, which
pass upward from the external iliac
vessels.
The margins of the ring give
attachment to the internal
spermatic fascia (or the internal
covering of the round ligament of
the uterus).
Walls of the lnguinal Canal
Anterior wall of the canal
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Is formed along its entire
length by the aponeurosis
of the external oblique
muscle.
It is reinforced in its lateral
third by the origin of the
internal oblique from the
inguinal ligament.
This wall is therefore
strongest where it lies
opposite the weakest part
of the posterior wall,
namely, the deep inguinal
ring.
Walls of the lnguinal Canal
Posterior wall of the canal
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Is formed along its entire
length by the fascia
transversalis.
It is reinforced in its
medial third by the
conjoint tendon.
This wall is therefore
strongest where it lies
opposite the weakest
part of the anterior wall,
namely, the superficial
inguinal ring.
Walls of the lnguinal Canal
Inferior wall of the canal (floor)
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Is formed by
the inguinal
ligament
and, at its
medial end,
the lacunar
ligament.
Walls of the lnguinal Canal
Superior wall of the canal (roof)
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Is formed by
the arching
lowest fibers
of the internal
oblique and
transversus
abdominis
muscles.
Functions of the lnguinal Canal

In the male, the inguinal canal allows structures of the
spermatic cord to pass to and from the testis to the
abdomen.
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(Normal spermatogenesis takes place only if the testis leaves
the abdominal cavity to enter a cooler environment in the
scrotum.)
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In the female, the smaller canal permits the passage of
the round ligament of the uterus from the uterus to the
labium majus.
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In both sexes, the canal also transmits the ilioinguinal
nerve.
Mechanics of the Inguinal Canal
The presence of the inguinal canal in the
lower part of the anterior abdominal
wall in both sexes constitutes a
potential weakness. It is interesting to
consider how the design of this
canal attempts to
lessen this weakness.
Mechanics of the Inguinal Canal
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Except in the newborn
infant, the canal is an
oblique passage with the
weakest areas, namely,
the superficial and deep
rings, lying some distance
apart.
The anterior wall of the
canal is reinforced by the
fibers of the internal
oblique muscle
immediately in front of the
deep ring.
Mechanics of the Inguinal Canal
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The posterior wall of the canal is
reinforced by the strong conjoint
tendon immediately behind the
superficial ring.
On coughing and straining, as in
micturition, defecation, and
parturition, the arching lowest fibers
of the internal oblique and
transversus abdominis muscles
contract, flattening out the arched
roof so that it is lowered toward the
floor.
The roof may actually compress the
contents of the canal against the floor
so that the canal is virtually closed.
Mechanics of the Inguinal Canal
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When great straining efforts may be necessary,
as in defecation and parturition, the person
naturally tends to assume the squatting
position: the hip joints are flexed, and the
anterior surfaces of the thighs are brought up
against the anterior abdominal wall.
By this means, the lower part of the anterior
abdominal wall is protected by the thighs.
Spermatic Cord
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The spermatic cord is a
collection of structures that
pass through the inguinal
canal to and from the testis.
It is covered with three
concentric layers of fascia
derived from the layers of
the anterior abdominal wall.
It begins at the deep
inguinal ring lateral to the
inferior epigastric artery and
ends at the testis.
Coverings of the
spermatic cord
Structures of the Spermatic Cord
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The structures are as follows:
vas deferens,
testicular artery,
testicular veins (pampiniform plexus),
testicular lymph vessels,
autonomic nerves,
remains of processus vaginalis,
cremasteric artery,
artery of the vas deferens,
genital branch of the genitofemoral nerve.
Spermatic Cord
Vas Deferens
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The vas deferens is a
cordlike structure that
can be palpated
between finger and
thumb in the upper part
of the scrotum.
It is a thick-walled
muscular duct that
transports spermatozoa
from the epididymis to
the urethra.
Spermatic Cord
Testicular Artery
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A branch of the
abdominal aorta (L2).
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It is long and slender
and descends on the
posterior abdominal
wall.
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It traverses the
inguinal canal and
supplies the testis and
the epididymis.
Spermatic Cord
Testicular Veins
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An extensive venous plexus
(pampiniform plexus), leaves
the posterior border of the
testis.
As the plexus ascends, it
becomes reduced in size so
that at about the level of the
deep inguinal ring, a single
testicular vein is formed.
This runs upon the posterior
abdominal wall and drains
into the left renal vein on the
left side and into the inferior
vena cava on the right side.
Spermatic Cord
Lymph Vessels
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The testicular lymph
vessels ascend through
the inguinal canal and
pass up over the
posterior abdominal wall
to reach the lumbar
(para-aortic) lymph
nodes on the side of the
aorta at the level of
(L1).
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This because the
gonads had migrated
from high up.
Spermatic Cord
Autonomic Nerves
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Sympathetic fibers run with the testicular artery
from the renal or aortic sympathetic plexuses.
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Afferent sensory nerves accompany the efferent
sympathetic fibers.
Spermatic Cord
Other Structures
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Remnants of Processus
Vaginalis.
Cremasteric artery (a branch
of the inferior epigastric
artery) supplies the
cremasteric fascia.
Artery to the vas deferens (a
branch of the inferior vesical
artery).
The genital branch of the
genitofemoral nerve, which
supplies the cremaster
muscle.
Coverings of the Spermatic Cord
Coverings of
the
Spermatic Cord
External
spermatic
fascia
Cremasteric
fascia
Internal
spermatic
fascia
Coverings of the Spermatic Cord
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External spermatic fascia
aponeurosis
Cremasteric fascia
Internal spermatic fascia
the external oblique
the internal oblique muscle
the fascia transversalis
Development of the Inguinal Canal
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A peritoneal
diverticulum called the
processus vaginalis is
formed.
It passes through the
layers of the lower
part of the anterior
abdominal wall.
It acquires a tubular
covering from each
layer.
Development of the Inguinal Canal
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A band of
mesenchyme,
extending from the
lower pole of the
developing gonad
through the inguinal
canal to the
labioscrotal swelling,
has condensed to form
the gubernaculum.
This band guides the
descent of the
developing gonad.
Development of the Inguinal Canal
Development of the Inguinal Canal
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The testis descends through the pelvis and inguinal
canal during the seventh and eighth months of fetal life.
The normal stimulus for the descent of the testis is
testosterone, which is secreted by the fetal testes.
The testis follows the gubernaculum and descends
behind the peritoneum on the posterior abdominal wall.
The testis then passes behind the processus vaginalis
and pulls down its duct, blood vessels, nerves, and
lymph vessels.
The testis takes up its final position in the developing
scrotum by the end of the eighth month.
Development of the Inguinal Canal
Development of the Inguinal Canal
Development of the Inguinal Canal
Development of the Inguinal Canal
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Because the testis and its accompanying
vessels, ducts, and so on follow the
course previously taken by the processus
vaginalis, they acquire the same three
coverings as they pass down the inguinal
canal.
Development of the Inguinal Canal
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Regarding females,
the round ligament of
the uterus is the part
of the gubernaculum
extending from uterus
to the labium majus.
The inguinal canal in
female transmits the
round ligament of the
uterus, lymph vessels
and the ilioinguinal
nerve.
VASECTOMY
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Bilateral vasectomy is a simple operation performed
to produce infertility.
Under local anesthesia, a small incision is made in
the upper part of the scrotal wall, and the vas
deferens is divided between ligatures.
Spermatozoa may be present in the first few post
operative ejaculations, but that is simply an emptying
process.
Now only the secretions of the seminal vesicles and
prostate constitute the seminal fluid, which can be
ejaculated as before.
Scrotum
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1.
2.
The scrotum can be considered as an
out- pouching of the lower part of the
anterior abdominal wall.
It contains the testes, the epididymis,
and the lower ends of the spermatic
cords.
The wall of the scrotum has the
following layers:
Skin,
Superficial fascia;
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dartos muscle (fatty layer),
Colles fascia (membranous layer),
External spermatic fascia (external
oblique),
Cremasteric fascia (internal oblique),
Internal spermatic fascia (fascia
transversalis),
Tunica vaginalis.
Scrotum
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The skin of the scrotum is thin, wrinkled, and pigmented
and forms a single pouch.
The dartos muscle is innervated by sympathetic nerve
fibers and is responsible for the wrinkling of the skin.
A slightly raised ridge in the midline indicates the line of
fusion of the two lateral labioscrotal swellings.
Both layers of superficial fascia contribute to the median
partition that crosses the scrotum and separates the
testes from each other.
In the female, the swellings remain separate and form
the labia majora.
Scrotum
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The spermatic
fasciae lie beneath
the superficial
fascia and are
derived from the
three layers of the
anterior abdominal
wall on each side.
Scrotum
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The cremaster muscle can be made to contract by
stroking the skin on the medial aspect of the thigh. This
is called the cremasteric reflex.
The afferent fibers of this reflex arc travel in the femoral
branch of the genitofemoral nerve (L1 and 2), and the
efferent motor nerve fibers travel in the genital branch of
the genitofemoral nerve.
The function of the cremaster muscle is to raise the
testis and the scrotum upward for warmth and for
protection against injury for testicular temperature and
fertility.
Scrotum
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The tunica vaginalis lies
within the spermatic fasciae
and covers the anterior,
medial, and lateral surfaces
of each testis.
It is the lower expanded
part of the processus
vaginalis; normally, just
before birth, it becomes
shut off from the upper part
of the processus and the
peritoneal cavity.
The tunica vaginalis is thus
a closed sac, invaginated
from behind by the testis.
Scrotum
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Lymph drainage
from the skin and
fascia. including
the tunica
vaginalis, drains
into the superficial
inguinal lymph
nodes.
Testis
The testis is a firm, mobile organ lying
within the scrotum.
 The left testis usually lies at a lower level
than the right.
 The upper pole of the gland is tilted
slightly forward.
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Testis
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Each testis is
surrounded by a
tough fibrous
capsule, the tunica
albuginea.
Extending from the
inner surface of the
capsule is a series of
fibrous septa that
divide the interior of
the organ into
lobules.
Testis
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Lying within each lobule
are one to three coiled
seminiferous tubules.
The tubules open into a
network of channels
called the rete testis.
Small efferent ductules
connect the rete testis to
the upper end of the
epididymis.
Testis
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Normal spermatogenesis can occur only if the testes are
at a temperature lower than that of the abdominal cavity.
When they are located in the scrotum, they are at a
temperature about 3°C lower than the abdominal
temperature.
The control of testicular temperature in the scrotum is
not fully understood, but the surface area of the scrotal
skin can be changed reflexly by the contraction of the
dartos and cremaster muscles.
Testis
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It is now recognized that the testicular veins in
the spermatic cord that form the pampiniform
plexus—together with the branches of the
testicular arteries, which lie close to the veins—
probably assist in stabilizing the temperature of
the testes by a countercurrent heat exchange
mechanism.
By this means, the hot blood arriving in the
artery from the abdomen loses heat to the blood
ascending to the abdomen within the veins.
Epididymis
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The epididymis is a firm structure lying posterior to the testis, with the vas
deferens lying on its medial side.
It has an expanded upper end, the head, a body, and a pointed tail
inferiorly.
Epididymis
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Laterally, a distinct groove lies
between the testis and the
epididymis, which is lined with
the inner visceral layer of the
tunica vaginalis and is called
the sinus of the epididymis.
The epididymis is a much
coiled tube nearly (6 m) long,
embedded in connective
tissue.
The tube emerges from the tail
of the epididymis as the vas
deferens, which enters the
spermatic cord.
Function of the Epididymis
The long length of the duct of the
epididymis provides storage space for the
spermatozoa and allows them to mature.
 A main function of the epididymis is the
absorption of fluid.
 Another function may be the addition of
substances to the seminal fluid to nourish
the maturing sperm.
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Varicocele
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A varicocele is a condition in which the veins of the
pampiniform plexus are elongated and dilated.
It is a common disorder in adolescents and young adults,
with most occurring on the left side.
This is thought to be because the right testicular vein
joins the low-pressure inferior vena cava, whereas the left
vein joins the left renal vein, in which the venous pressure
is higher.
Rarely, malignant disease of the left kidney extends along
the renal vein and blocks the exit of the testicular vein.
A rapidly developing left-sided variocele should therefore
always lead one to examine the left kidney.
Varicocele
Malignant Tumor of the Testis
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A malignant tumor of the testis spreads
upward via the lymph vessels to the
lumbar (para-aortic) lymph nodes at the
level of the L1 vertebra.
It is only later, when the tumor spreads
locally to involve the tissues and skin of
the scrotum, that the superficial inguinal
lymph nodes are involved.
Malignant Tumor of the Testis
Clinical Focus 5-15, Netter’s Clinical Anatomy, 3rd Ed
Clinical Anatomy, Abdominal Wall
61
Torsion of the Testis
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Torsion of the testes is a rotation of the testis
around the spermatic cord within the scrotum.
It is often associated with an excessively large
tunica vaginalis.
Torsion commonly occurs in active young men
and children and is accompanied by severe
pain.
If not treated quickly, the testicular artery may
be occluded, followed by necrosis of the testis.
Torsion of the Testis
Processus Vaginalis
Normally, the upper part becomes obliterated just before birth and the lower
part remains as the tunica vaginalis.
It may become very
much narrowed, but its
lumen remains in
communication with the
abdominal cavity.
 Peritoneal fluid
accumulates in it, forming
a congenital hydrocele.
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The
upper and lower ends of the
processus may become
obliterated, leaving a small
intermediate cystic area referred
to as an encysted hydrocele of the
cord.
It may persist
partially or in its
entirety as a
preformed hernial
sac for an indirect
inguinal hernia.
Processus Vaginalis
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The tunica vaginalis is closely
related to the front and sides of
the testis.
So, inflammation of the testis
can cause an accumulation of
fluid within the tunica vaginalis.
This is referred to simply as a
hydrocele.
Most hydroceles are idiopathic.
Processus Vaginalis
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Tapping a hydrocele is a procedure to remove excess fluid
from the tunica vaginalis.
A fine trocar and cannula are inserted through the scrotal
skin.
The following anatomic structures are traversed:
skin,
dartos muscle,
membranous layer of fascia (Colles’ fascia),
external spermatic fascia,
cremasteric fascia,
internal spermatic fascia,
parietal layer of the tunica vaginalis.
Processus Vaginalis
Congenital Anomalies of the Testis
1.
Anterior inversion, in which the
epididymis lies anteriorly and the testis
and the tunica vaginalis lie posteriorly.
2.
Polar inversion, in which the vertical
position of the testis is reversed and the
head of epididymis can be felt below
the testis.
Congenital Anomalies of the Testis
3.
Imperfect descent
(cryptorchidism);
Incomplete descent, in
which the testis,
although traveling down
its normal path, fails
reach the floor of the
scrotum, It may be
found within the
abdomen, within the
inguinal canal, the
superficial inguinal ring,
or high up in the
scrotum.
CONGENITAL ANOMALIES OF THE
TESTIS
4.
Maldescent, in which
the testis travels down
an abnormal path and
fails to reach the
scrotum. It may be
found in the superficial
fascia of the anterior
abdominal wall above
the inguinal ligament,
in front of the pubis, in
the perineum, or in the
thigh.
Congenital Anomalies of the Testis
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It is necessary for the testes to leave the
abdominal cavity because the
temperature there retards the normal
process of spermatogenesis.
If an incompletely descended testis is
brought down into the scrotum by
surgery before puberty, it will develop
and function normally.
Congenital Anomalies of the Testis
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A maldescended testis, although often
developing normally, is susceptible to
traumatic injury and, for this reason,
should be placed in the scrotum.
Many authorities believe that the
incidence of tumor formation is greater in
testes that have not descended into the
scrotum.
Congenital Anomalies of the Testis
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The appendix of
the testis and the
appendix of the
epididymis are
embryologic
remnants found
at the upper
poles of these
organs that may
become cystic.
LABIA MAJORA
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The labia majora are
prominent, hair-bearing folds
of skin formed by the
enlargement of the genital
swellings in the fetus. (In the
male, the genital swellings
fuse in the midline to form
the scrotum).
Within the labia are a large
amount of adipose tissue
and the terminal strands of
the round Iigaments of the
uterus.