VGO 511: Veterinary Andrology and Reproductive Techniques (1+1)

Anatomy

ANATOMY OF SCROTUM AND TESTIS

Testis - Primary andrological organ located inside the scrotum.

• Testis is the primary andrological organ which produces spermatozoa and male sex hormone (testosterone).
  • Testes are morphologically oval shaped, paired glands. Right and left testicles are separated by muscular septum which is formed by dartos muscle.
  • The scrotum is a bilobed sac/pouch (derived from the skin and fascia) and is the external part of male reproductive system which encloses the testis.
  • It is located between the thighs except in case of boar and tom cat.
  • In boar and tom cat, it is located caudal to the thighs, caudal and ventral to the ischiatic arch.
  • Scrotum externally composed of skin which is relatively devoid of hair except in ram (male sheep) and buck (male goat) and tom cat (male cat).
  • Beneath the skin is the dartos muscle, which consists of fibro-elastic tissue and unstriped muscle.
  • Dartos muscle divides the scrotum in to two halves.
  • It is closely attached with the tunica vaginalis and scrotal ligament which is a remnant of gubernaculum. Scrotal ligament absent in bulls.
  • Testis and epididymis are fixed in scrotum by means of scrotal ligament which is attached near the tail of the epididymis and mesorchium

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Scrotum has the following 8 layers from externally

• Epidermis – outermost layer
• Dermis
• Dartos muscle
• Connective tissue
• Parietal layer of vaginal process (PVP)
• Cavity of vaginal process (CV)
• Visceral layer of vaginal process (VVP)
• Tunica albuginea
• The testis is supported in one of the two scrotal pouches where it is held by its tunics and by the spermatic cord.

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The Spermatic Cord is composed of

• Spermatic artery
• Spermatic vein
• Spermatic nerve
• Lymphatic vessels
• Internal cremaster muscle
• Vas deferens
• Tunica vaginalis

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Species difference

Characters	Bull	Stallion	Ram	Boar	Dog	Cat
Shape	Oval	Oval	Oval	Oval	Round to oval	Round to oval
Length	10-15 cm	7.5-12.5 cm	7.5-11.5 cm	10-15 cm	2-4 cm	1.2-2 cm
Diameter	5-8.5 cm	4-7 cm	3.8-6.8 cm	5-9 cm	1-2.5 cm	0.7-1.5 cm
Weight	200-500 gm	200-300 gm	200-400 gm	600 gm	7-15 gm	0.7-1.5 cm
Plane	Vertical	Horizontal	Vertical	Vertical	Oblique	Oblique

• In bulls - head of the epididymis is dorsal and tail ventral to the testis.
• In stallions - the head of the epididymis is cranial and tail caudal to the testis. The appendix testis is present at cranial pole of testis. It is remnant of paramesonephric duct.
• In Rams - head of the epididymis is dorsal and tail ventral to the testis. Appendix testis is rarely present
• In boars - the head of the epididymis is ventral and tail dorsal to the testis.
• In dogs - the head of the epididymis is cranial and tail caudal to the testis

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Blood Supply

• The testis is richly supplied with blood by the Spermatic artery/ Testicular artery, a branch of the abdominal aorta.
• The veins on leaving the testicles form a network, the pampiniform plexus around the artery in spermatic cord. The spermatic vein which issues from this plexus, usually joins with the posterior venacava on the right side, the left renal vein on left side.

Nerve Supply

• The nerves derived from the renal and posterior mesenteric plexus form the spermatic plexus around the vessels to which they are chiefly distributed.

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