Antomy of scrotum and testis

Antomy of scrotum and testis

1. Anatomy of scrotum and testis Dr. Priyanka Rana

2. I ntroduction 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. Skin Dartos muscle which replaces the superficial fascia. The external spermatic fascia. The cremasteric muscle and fascia. The internal spermatic fascia. The dartos muscle is prolonged into the medial vertical septum into the two halves of the scrotum.

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

6. Nerve supply Anterior 1/3 rd : segment L1 of spinal cord through ilioinguinal nerves and genital branch of genitofemoral nerve. Posterior 2/3 rd : 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

7. 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

8. 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

9. 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.

10. 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.

11. Covering of the testis The testis is covered by Three coats. Tunica Vaginalis . Tunica albuginea. Tunica vasculosa .

12. 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.

13. 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.

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

15. 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.

16. 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.

17. 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 .

18. 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.

19. 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.

20. 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.

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

22. 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.

23. 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.

24. 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)

25. MRI

26. Q-Layers of scrotum?

27. The scrotum is made up of the following layers from inside to outside. Skin Dartos muscle The external spermatic fascia. The cremasteric muscle and fascia. The internal spermatic fascia.