Antomy of scrotum and testis

1. Anatomy of scrotum and
testis
Dr. Priyanka Rana

2. Introduction
 Scrotum is cutaneous bag containing the right and left
testis, the epididymis and the lower part of spermatic
cords.
Externally, the scrotum is divided into right and left parts
by a ridge or raphe which is continued forwards on to the
undersurface of the penile and backwards along the
middle of the perineum to the anus.
The left half of the scrotum hangs a little lower than the
right, in correspondence with the greater length of the left
spermatic cord.

3.  Under the influence of cold, and in young and robust
persons, the scrotum is short, corrugated and closely
applied to the testis. This is due to contraction of the
subcutaneous muscle of scrotum, called the dartos.
However, under the influence of the warmth and in old
and debilitated persons, the scrotum is elongated and
flaccid due to relaxation of dartos. From this it appears
that the dartos muscle helps in regulation of
temperature within the scrotum.

4. Layers of scrotum
 The scrotum is made up of the following layers from inside
to outside.
1. Skin
2. Dartos muscle which replaces the superficial fascia.
3. The external spermatic fascia.
4. The cremasteric muscle and fascia.
5. The internal spermatic fascia. The dartos muscle is
prolonged into the medial vertical septum into the two
halves of the scrotum.

6. Blood supply
 Scrotum is supplied by
 Superficial external pudendal, deep external pudendal.
 Scrotal branches of intenal pudendal
 Cremasteric branch of inferior epigastric

7. Nerve supply
 Anterior 1/3rd : segment L1 of spinal cord through
ilioinguinal nerves and genital branch of genitofemoral
nerve.
 Posterior 2/3rd : segment S3 of spinal cord through the
posteior scrotal branches of the pudendal nerve, and
the perineal branch of the posterior cutaneous nerve of
the thigh.
 The dartos muscle is supplied by genital branch of
genitofemoral nerve

8. TESTIS
 The testis is the male gonad. It is homologous with the ovary
of the female.
 It is suspended in the scrotum by the spermatic cord. It lies
obliquely, so that its upper pole is titled forwards and medially.
The left testis is slightly lower than the right.
 The testis is oval in shape, and is compressed from side to
side. It is 3.75 cm long, 2.5 cm thick from side to side. An
adult testis weight about 10 to 15 gms.
Size :
 At birth : 1.5cm(L) x 1.0cm(W)
 <12 years : 1-2cc
 10-15cc (2x3x4cms-BaPL) in adults Puberty achieved :
>4cc

9. External features
1. Two poles or ends: upper and lower
 Upper and lower pole are convex and smooth.Upper
pole provides attachment to the spermatic cord

10. 2. Two borders, anterior and posterior.
 The anterior border is convex and smooth, and is fully
covered by tunica vaginalis.
The posterior border is straight, and is only partially
covered by the tunica vaginalis. The epididymis lies along
the lateral part of the posterior border. The lateral part of
the epididymis is separated from the testis by an
extension of the cavity of the tunica vaginalis. This
extension is called the sinus of epididymis.

11. 3. Two surfaces, medial and lateral.
 The medial and lateral surfaces are convex and
smooth.
 Attached to the upper pole of the testis, there is a small
oval body called the appendix of the testis. It us a
remnant of the paramesonephric duct.

12. Covering of the testis
 The testis is covered by Three coats.
1. Tunica Vaginalis.
2. Tunica albuginea.
3. Tunica vasculosa.

13.  1. TUNICA VAGINALIS
The tunica vaginalis represents the lower persistent
portion of the processus vaginalis. It is invaginated by the
testis from behind and , therefore, has a parietal and a
visceral layer with a cavity in between. It covers the whole
testis, except for its posterior border.

14. 2. TUNICA ALBUGINEA
It is a dense, white fibrous coat covering the testis all
around. It is covered by the visceral layer of the tunica
vaginalis, except posteriorly where the testicular vessels
and nerves enter the gland. The posterior border of the
tunica albuginea is thickened to form an incomplete
vertical septum, called the mediastinum testis, which is
wider above than below. Numerous septa extend from
the mediastinum to the inner surface of the tunica
albuginea. They incompletely divide the testis into 200 to
300 lobules.

15. 3. TUNICA VASCULOSA
It is the innermost, vascular coat of the testis lining its
lobules.

16. Structure of the testis
The glandular part of the testis consist of 200 to 300
lobules. Each lobule contains two to three seminiferous
tubules. Each tubule is highly coiled on itself. When
stretched out, each tubules measures about 60 cm in
length, and is about 0.2 mm in diameter. The tubules are
lined by cells which represents stages in the formation of
spermatozoa.

17.  The seminiferous tubules join together at the apices of the
lobules to form 20 to 30 straight tubules which enter the
mediastinum. Here they anastomose with each other to
form a network of tubules, called the rete testis. In its turn
the rete testis gives rise to 12 to 30 efferent ductules which
emerge near the upper pole of the testis and enter the
epididymis. Here each tubule becomes highly coiled and
forms a lobe of the head of the epididymis. The tubules end
in a single duct which is coiled on itself to form the body and
tail of the epididymis. It is continuous with the ductus
deferens.

18. Arterial supply of testis
 The testicular artery is a branch of the abdominal aorta
given off at the level of vertebra L2. It descends on the
posterior abdominal wall to reach the deep inguinal ring
where it enters the spermatic cord. At the posterior
border of the testis, it divides into branches. Some
small branches enter the posterior border, while larger
branches; medial and lateral, pierce the tunica
albuginea and run on the surface of the testis to ramify
in the tunica vasculosa.

19. Venous Drainage
 The veins emerging from the testis form the
pampiniform plexus. The anterior part of the plexus is
arranged around the testicular artery, the middle part
around the ductus deferens and its artery, and the
posterior part is isolated.
 The plexus condenses into four veins at the superficial
inguinal ring, and into two veins at the deep inguinal
ring. These veins accompany the testicular artery.
Ultimately one vein is formed which drains into the
inferior vena cava on the right side, and into the left
renal vein on the left side.

20. Lymphatic Drainage
 The lymphatic's from the testis ascends along the
testicular vessels and drains into the pre aortic and
para aortic groups of lymph nodes at the level of
second lumbar vertebra.

21. Epididymis
 The epididymis, which overlies the superolateral aspect
of the testis, comprises a head, body, and tail. The tail
of the epididymis continues as the vas deferens in the
spermatic cord. The epididymal head is a 5–12-mm
pyramidal structure situated atop the superior pole of
the testis. At US, the head is nearly isoechoic to the
testis. The body of the epididymis is 2–4 mm thick.

23. Imaging Modalities
 Scrotal USG (with colour Doppler)
 MRI
 CT

24. Testicular and scrotal ultrasound is the primary modality
for imaging most of the male reproductive system. It is
relatively quick, relatively inexpensive, can be correlated
quickly with the patient's signs and symptoms, and, most
importantly, is non-ionising.
MRI is occasionally used for problem solving if the diagnosis
is unclear on ultrasound. CT is only rarely needed, and is
avoided because of its ionising radiation.

28.  Normal testis in a 24-year-old man. Mediastinum testis (arrow) is a normal finding,
seen as an echogenic band running across the testis on a sagittal US scan.

29.  Longitudinal US scan of a normal testis in a adult-shows the appendix testis (arrow)
as a hypoechoic structure. The presence of hydrocele renders the appendix testis
visible. (b) Longitudinal US scan of a normal epididymis shows normal epididymis
(arrow)

30. MRI

33. Q-Layers of scrotum?

34.  The scrotum is made up of the following layers from
inside to outside.
1. Skin
2. Dartos muscle
3. The external spermatic fascia.
4. The cremasteric muscle and fascia.
5. The internal spermatic fascia.