Scrotum and Testis and Epididmides and Labia majora pdf - Abdomen

Basic Anatomy

ent motor nerve fibers travel in the genital branch of

of the genitofemoral nerve (L1 and 2), and the effer

ent fibers of this reflex arc travel in the femoral branch

The affer

cremasteric reflex.

the thigh. This is called the

to contract by stroking the skin on the medial aspect of

nerve (see page 222). The cremaster muscle can be made

is supplied by the genital branch of the genitofemoral

from the fascia transversalis. The cremaster muscle

cle; and, finally, the internal spermatic fascia is derived

masteric fascia is derived from the internal oblique mus

the aponeurosis of the external oblique muscle; the cre

explained. The external spermatic fascia is derived from

anterior abdominal wall on each side, as previously

ficial fascia and are derived from the three layers of the

These three layers lie beneath the super

Spermatic fasciae.

and separates the testes from each other.

tribute to a median partition that crosses the scrotum

ischiopubic rami. Both layers of superficial fascia con

membrane (see Fig. 4.1). At the sides, it is attached to the

perineal body and the posterior edge of the perineal

wall (Scarpa’s fascia), and behind it is attached to the

with the membranous layer of the anterior abdominal

(often referred to as Colles’ fascia) is continuous in front

ing skin. The membranous layer of the superficial fascia

fibers and is responsible for the wrinkling of the overly

This is innervated by sympathetic nerve

dartos muscle.

fat is, however, replaced by smooth muscle called the

membranous layers of the anterior abdominal wall; the

This is continuous with the fatty and

Superficial fascia.

remain separate and form the labia majora.)

eral labioscrotal swellings. (In the female, the swellings

in the midline indicates the line of fusion of the two lat

mented and forms a single pouch. A slightly raised ridge

The skin of the scrotum is thin, wrinkled, and pig

Skin.

The wall of the scrotum has the following layers:

mides, and the lower ends of the spermatic cords (see Figs.

anterior abdominal wall. It contains the testes, the epididy

The scrotum is an outpouching of the lower part of the

Scrotum

Scrotum, Testis, and Epididymides

the uterus to the superficial inguinal nodes.

vessels convey a small amount of lymph from the body of

ligament of the uterus and a few lymph vessels. The lymph

inguinal canal from the abdominal cavity are the round

131

4.4 and 4.21).

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the genitofemoral nerve. The function of the cremaster

cremaster muscles. It is now recognized that the testicular

be changed reflexly by the contraction of the dartos and

fully understood, but the surface area of the scrotal skin can

The control of testicular temperature in the scrotum is not

perature about 3°C lower than the abdominal temperature.

When they are located in the scrotum, they are at a tem

at a temperature lower than that of the abdominal cavity.

Normal spermatogenesis can occur only if the testes are

Fig. 4.21).

nect the rete testis to the upper end of the epididymis (see

con

efferent ductules

Small

rete testis.

channels called the

The tubules open into a network of

seminiferous tubules.

Lying within each lobule are one to three coiled

lobules.

of fibrous septa that divide the interior of the organ into

Extending from the inner surface of the capsule is a series

tunica albuginea.

fibrous capsule, the

level than the right. Each testis is surrounded by a tough

(see Figs. 4.5 and 4.21). The left testis usually lies at a lower

is a firm, mobile organ lying within the scrotum

testis

The

Testis

drains into the superficial inguinal lymph nodes (see Fig. 4.22).

Lymph from the skin and fascia, including the tunica vaginalis,

Lymph Drainage of the Scrotum

testis.

nalis is thus a closed sac, invaginated from behind by the

the processus and the peritoneal cavity. The tunica vagi

before birth, it becomes shut off from the upper part of

expanded part of the processus vaginalis; normally, just

medial, and lateral surfaces of each testis. It is the lower

within the spermatic fasciae and covers the anterior,

(see Figs. 4.4, 4.5, and 4.21). This lies

Tunica vaginalis

temperature and fertility, see below.

warmth and for protection against injury. For testicular

muscle is to raise the testis and the scrotum upward for

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 sta

stances to the seminal fluid to nourish the maturing sperm.

tion of fluid. Another function may be the addition of sub

mature. A main function of the epididymis is the absorp

storage space for the spermatozoa and allows them to

The long length of the duct of the epididymis provides

enters the spermatic cord.

which

vas deferens,

from the tail of the epididymis as the

long, embedded in connective tissue. The tube emerges

The epididymis is a much coiled tube nearly 20 ft (6 m)

(see Fig. 4.21).

sinus of the epididymis

the inner visceral layer of the tunica vaginalis and is called

between the testis and the epididymis, which is lined with

inferiorly. Laterally, a distinct groove lies

and a pointed

body,

head,

Fig. 4.21). It has an expanded upper end, the

testis, with the vas deferens lying on its medial side (see

is a firm structure lying posterior to the

epididymis

The

blood ascending to the abdomen within the veins.

arriving in the artery from the abdomen loses heat to the

heat exchange mechanism. By this means, the hot blood

bilizing the temperature of the testes by a countercurrent

Epididymis

tail

the

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Vasectomy

postoperative ejaculations, but that is simply an emptying process.

between ligatures. Spermatozoa may be present in the first few

upper part of the scrotal wall, and the vas deferens is divided

infertility. Under local anesthesia, a small incision is made in the

Bilateral vasectomy is a simple operation performed to produce

Now only the secretions of the seminal vesicles and prostate con-

stitute the seminal fluid, which can be ejaculated as before.

C L I N I C A L N O T E S

132

CHAPTeR 4

aorta (lumbar or para-aortic) nodes at the level of the 1st

matic cord and end in the lymph nodes on the side of the

The lymph vessels (see Fig. 4.22) ascend in the sper

Lymph Drainage of the Testis and Epididymis

cava, and the left vein joins the left renal vein.

canal. The right testicular vein drains into the inferior vena

reduced to a single vein as it ascends through the inguinal

This becomes

pampiniform plexus.

a venous network, the

testicular veins emerge from the testis and the epididymis as

The testicular artery is a branch of the abdominal aorta. The

Blood Supply of the Testis and Epididymis

The Abdomen: Part I—The Abdominal Wall

lumbar vertebra (i.e., on the transpyloric plane). This is

migrated from high up on the posterior abdominal wall,

to be expected because during development the testis has

Clinical Conditions Involving the Scrotum and Testis

should therefore always lead one to examine the left kidney.

exit of the testicular vein. A rapidly developing left-sided variocele

ease of the left kidney extends along the renal vein and blocks the

vein, in which the venous pressure is higher. Rarely, malignant dis

sure inferior vena cava, whereas the left vein joins the left renal

cents and young adults, with most occurring on the left side. This is

A varicocele is a condition in which the veins of the pampiniform

Varicocele

plexus are elongated and dilated. It is a common disorder in adoles-

thought to be because the right testicular vein joins the low-pres-

Malignant Tumor of the Testis
A malignant tumor of the testis spreads upward via the lymph

vessels to the lumbar (para-aortic) lymph nodes at the level of

the first lumbar 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.

The process of the descent of the testis is shown in

Figure 4.23. The testis may be subject to the following congenital

anomalies.

the lower part of the anterior abdominal wall with the formation

The formation of the processus vaginalis and its passage through

Torsion of the testis is a rotation of the testis around the sper

Torsion of the Testis

matic 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.

Processus Vaginalis

of the inguinal canal in both sexes were described elsewhere

(see page 130). Normally, the upper part becomes obliterated just

before birth and the lower part remains as the tunica vaginalis.

The processus is subject to the following common congenital

anomalies:
1. It may persist partially or in its entirety as a preformed hernial

sac for an indirect inguinal hernia (Fig. 4.24).

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 (Fig. 4.24).

The upper and lower ends of the processus may become

spermatic fascia, cremasteric fascia, internal spermatic fascia,

The tunica vaginalis is closely related to the front and sides

obliterated, leaving a small intermediate cystic area referred

to as an encysted hydrocele of the cord (see Fig. 4.24).

of the testis. It is therefore not surprising to find that inflam-

mation of the testis can cause an accumulation of fluid within

the tunica vaginalis. This is referred to simply as a hydrocele

(Fig. 4.25). Most hydroceles are idiopathic.

To remove excess fluid from the tunica vaginalis, a proce-

dure termed tapping a hydrocele, a fine trocar and cannula are

inserted through the scrotal skin (see Fig. 4.25). The following

anatomic structures are traversed by the cannula: skin, dartos

muscle and membranous layer of fascia (Colles’ fascia), external

and parietal layer of the tunica vaginalis.

C L I N I C A L N O T E S

peritoneal cavity

vas deferens

epididymis

testis

cyst

peritoneal fluid

persistent
processus
vaginalis

coils of small intestine inside

persistent processus vaginalis,

which forms hernial sac

FIGURE 4.24

Common congenital anomalies of the processus vaginalis.

Preformed hernial sac for indirect inguinal hernia.

Encysted hydrocele of

Congenital hydrocele.

the cord. C.

Basic Anatomy

133

acquired

hydrocele

scrotal skin

dartos muscle

membranous layer of

superficial fascia

external spermatic fascia

cremasteric fascia

internal spermatic fascia

tunica vaginalis

testis

hydrocele fluid

FIGURE 4.25

The tunica vaginalis distended with fluid (hydrocele). Also shown are the various anatomic layers traversed by a

trocar and a cannula when a hydrocele is tapped.

Development of the Testis

developing normally, is susceptible to traumatic injury and, for

and function normally. A maldescended testis, although often

down into the scrotum by surgery before puberty, it will develop

because the temperature there retards the normal process of

mal path and fails to reach the scrotum. It may be found in the

found within the abdomen, within the inguinal canal, at the

The sex cords become

tunica albuginea.

dense fibrous layer, the

The male sex chromosome causes the genital ridge to secrete

testosterone and induces the development of the testis and the

other internal and external organs of reproduction.

The sex cords of the genital ridge become separated from the

coelomic epithelium by the proliferation of the mesenchyme (Fig.

4.26). The outer part of the mesenchyme condenses to form a

U-shaped and form the seminiferous tubules. The free ends of

the tubules form the straight tubules, which join one another in

the mediastinum testis to become the rete testis. The primordial

sex cells in the seminiferous tubules form the spermatogonia,

and the sex cord cells form the Sertoli cells. The mesenchyme

in the developing gonad makes up the connective tissue and

fibrous septa. The interstitial cells, which are already secret-

ing testosterone, are also formed of mesenchyme. The rete testis

becomes canalized, and the tubules extend into the mesonephric

tissue, where they join the remnants of the mesonephric tubules;

the latter tubules become the efferent ductules of the testis. The
duct of the epididymis, the vas deferens, the seminal vesicle,

and the ejaculatory duct are formed from the mesonephric duct

(see Fig. 4.26).

Descent of the Testis
The testis develops high up on the posterior abdominal wall, and

in late fetal life it “descends” behind the peritoneum, dragging its

blood supply, nerve supply, and lymphatic drainage after it (for

details, see page 130). The process of the descent of the testis is

shown in Figure 4.23.

Congenital Anomalies of the Testis
The testis may be subject to the following congenital anomalies.

■

Anterior inversion, in which the epididymis lies anteriorly and

the testis and the tunica vaginalis lie posteriorly

■

Polar inversion, in which the testis and epididymis are com-

pletely inverted

■

Imperfect descent (cryptorchidism): Incomplete descent

(Fig. 4.27), in which the testis, although traveling down its

normal path, fails to reach the floor of the scrotum. It may be

superficial inguinal ring, or high up in the scrotum.

■

Maldescent (Fig. 4.28), in which the testis travels down an abnor-

superficial fascia of the anterior abdominal wall above the ingui-

nal ligament, in front of the pubis, in the perineum, or in the thigh.

It is necessary for the testes to leave the abdominal cavity

spermatogenesis. If an incompletely descended testis is brought

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.

The appendix of the testis and the appendix of the epididy-

mis are embryologic remnants found at the upper poles of these

organs that may become cystic. The appendix of the testis is

derived from the paramesonephric ducts, and the appendix of

the epididymis is a remnant of the mesonephric tubules.

E M B R Y O L O G I C N O T E S

134

CHAPTeR 4

The Abdomen: Part I—The Abdominal Wall

posterior abdominal wall

coelomic epithelium

dorsal

mesentery

gut

primordial sex cells

sex cords

genital ridge

tunica albuginea

coelomic epithelium

mesonephric duct

mesonephric tubule

U-shaped sex cords

rete testis

mesonephros

paramesonephric duct

genital ridge

gubernaculum

appendix of epididymis

superior aberrant ductules

efferent ductules

tunica albuginea

vas deferens

inferior aberrant ductules

canal of epididymis

seminal

vesicle

prostatic

urethra

FIGURE 4.26

The formation of the testis and the ducts of the testis.

FIGURE 4.27

Four degrees of incomplete descent of the

the five lumbar vertebrae and their intervertebral discs and

The posterior abdominal wall is formed in the midline by

Structure of the Posterior Abdominal Wall

ligaments of the uterus. (For further details, see page 288.)

of adipose tissue and the terminal strands of the round

to form the scrotum.) Within the labia are a large amount

fetus. (In the male, the genital swellings fuse in the midline

formed by the enlargement of the genital swellings in the

The labia majora are prominent, hair-bearing folds of skin

dragging its blood supply and lymph vessels after it.

down through the inguinal canal, and into the scrotum,

In the upper part of scrotum.

ring.

At the superficial inguinal

ring.

In the abdominal cavity close to the deep inguinal

testis. 1.

2. In the inguinal canal. 3.

Labia Majora

laterally by the 12th ribs, the upper part of the bony pelvis
(Fig. 4.29), the psoas muscles, the quadratus lumborum