Testes: Anatomy and Function, Diagram, Conditions

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Testis

The External Features Of The Testis And Explain In Detail The Coverings Of The Testis

Testes Anatomy

 

  • Male gonad
  • Homologous with ovary in female
  • It is suspended in the scrotal sac by spermatic cord
  • Lies obliquely in both half of the scrotum, such that the upper pole is tilted forwards and medially
  • Function: Secretion of testosterone, production of spermatozoa
  • Oval in shape, weight: 10–15 g
  • Measurements
    • Length: 4–5 cm
    • Breadth: 2.5 cm
    • Anteroposterior Diameter: 3 cm

Read And Learn More: Abdomen And Pelvis

Testis External Features: Testis has

  • Two Poles: Upper and lower
  • Two Borders: Anterior and posterior
  • Two Surfaces: Medial and lateral
    • Two poles are convex and smooth
    • The upper pole provides attachment to the spermatic cord

Testis Borders

  1. Anterior Border
    • Convex and smooth
    • Completely covered by tunica vaginalis
  2. Posterior Border
    • Straight
    • Partially covered by tunica vaginalis

Testis Relations:

  • Epididymis lies on its lateral aspect
  • Both are separated by an extension of the cavity of tunica vaginalis known as the sinus of the epididymis
    • Two Surfaces (Medial And Lateral): Convex and smooth.

Appendix Of The Testis:

  • Small oval body attached to the upper pole of the testis
  • It is the remnant of the paramesonephric duct.

Coverings of Testis

The Spermatic Cord And Testis

 

1. Tunica Vaginalis

  • Tunica Vaginalis is a serous sac
  • Represents the lower persistent portion of processus vaginalis
  • Tunica Vaginalis is invaginated by the testis from behind
  • As a result, it has two layers (parietal and visceral) with a cavity between them
  • Tunica vaginalis completely covers the testis, except for its posterior border.

2. Tunica Albuginea

  • The thick, dense, white fibrous layer
  • Tunica Albuginea completely covers the testis
  • Tunica Albuginea is enclosed by the visceral layer of tunica vaginalis except posteriorly where testicular nerves and vessels enter into testis
  • Mediastinum Testis: Vertical septum formed by the thickened posterior border of the tunica albuginea
  • Numerous incomplete fibrous septa extend from the mediastinum into the inner aspect of Tunica albuginea
  • These septa divide testis in to 200–300 lobules.

3. Tunica Vasculosa

  • Innermost vascular layer
  • It lines the lobules.

Testis Blood Supply

  1. Arterial Supply
    • Testicular Artery
      • Branch of abdominal aorta given of at level of L2 vertebrae
      • Descends through posterior abdominal wall
      • Reach deep inguinal ring
      • Enters spermatic cord
      • Reaches posterior border of testis
      • Divides Into:
        • Two large branches—medial and lateral
        • Small branches
      • Medial and lateral branches Pierces the tunica albuginea
      • Ramify in tunica vasculosa.
    • Artery To Vas (Sometimes)
  2. Venous Drainage
    • By pampiniform plexus of veins
    • Thy condenses into two veins at the deep inguinal ring and accompanies testicular artery
    • Finally, two veins fuse together forming one vein which drains into the inferior vena cava.

Testis Lymphatic Drainage: Preaortic and para-aortic lymph nodes.

Testis Nerve Supply: By sympathetic fibers from the T10 segment.

Development of Testis

The Development Of Testis

The development of the testis and ovaries begins in a similar manner but parts way at a particular point.

Development Of Gonads

Development Of Testis

  • Sex cords increase in length and extend into the medulla of the developing gonad. Sex cords are now called as medullary cords
  • The sex cords anastomose with each other and canalize resulting in the formation of seminiferous tubules
  • The ends of seminiferous tubules anastomoses with one another giving rise to rete testis
  • Two Types Of Cells Line The Seminiferous Tubules:
    • Spermatogenic cells: Formed from primordial germ cells
    • Sertoli cells: Formed from coelomic epithelium
  • A dense fibrous layer is formed by mesoderm which separates the sex cords from coelomic epithelium, known as the tunica albuginea.
  • Mesoderm Also Gives Rise To:
    • Leydig cells
    • The connective tissue around seminiferous tubules
    • Mediastinum testis
  • The canal of the epididymis and vas deferens develop from the mesonephric duct. The development of the testis and ovaries begins in a similar manner but parts way at a particular point
  • Gonads develop from three sources:
    • Intermediate mesoderm—which is present medial to the middle part of the mesonephros
    • Coelomic epithelium—which covers the intermediate mesoderm
    • Primordial germ cells from the wall of the yolk sac near the allantois
  • Coelomic epithelium begins to proliferate and it gets thickened
  • Mesoderm below the coelomic epithelium condenses due to the thickening of coelomic epithelium
  • Both these processes lead to the formation of the genital ridge
  • Coelomic epithelial cells continue to proliferate and they invade the condensed mesoderm in the form of solid cords, known as the ‘sex cords’
  • Primordial germ cells from the wall of the yolk sac migrate along the dorsal mesentery of the hindgut toward the developing gonad
  • Sex cords and primordial germ cells get intermixed
  • Till this point, the development of the testis and ovaries are the same.

 Descent of Testis

Descent Of Testis

  • Testis which develops in relation to the lumbar region of the posterior abdominal wall starts to descend
  • It gradually descends to the scrotum through the iliac fossa (3rd month) and the inguinal canal (7th month), finally reaching the scrotum by the end of 8th month.
  • It is a mandatory developmental process to ensure that the mature testis promotes normal spermatogenesis
  • Some Factors Responsible For The Descent Of The Testis Are:
    • Increased intra-abdominal pressure
    • Gubernaculum: A guiding force for the descent
    • Differential growth of body wall.

Vas Deferens

The Features And Course Of Vas Deferens

  • Also known as ductus deferens
  • Thick-walled muscular tubes
  • Two in number
  • Length: 45 cm
  • Lumen: Narrow, but the terminal part (ampulla) is sacculated.

Vas Deferens Course: It has

  • External course
  • Internal course.

Vas Deferens  External Course

Male Genital Organs Vas Deferens External Course

Vas Deferens Internal Course

Male Genital Organs Vas Deferens Internal Course

Vas Deferens Blood Supply

1. Arterial Supply

  • From artery to vas deferens
  • This artery can arise from either
    • Superior vesical artery (common)
    • Inferior vesical artery or
    • Middle vesical artery.

2. Vas Deferens Venous Drainage

Male Genital Organs Vas Deferens Bllod Supply Venous Drainge

3. Vas Deferens Nerve Supply

Pelvic splanchnic nerves—parasympathetic.

Male Internal Genital Organs

  • Penis
  • Scrotum

Male External Genital Organs

  • Testis
  • Epididymis
  • Vas deferens
  • Prostate
  • Seminal vesicles
  • Bulbourethral glands

Male Genital Organs Sagittal Section Depicting The Location Of Various Organs Of Male Reproductive System

Layers Of The Scrotum From Outside To Inside

The Layers Of The Scrotum From Outside To Inside

  1. Skin
  2. Dartos muscle (which replaces the superficial fascia)
  3. External spermatic fascia
  4. Cremasteric muscle and fascia
  5. Internal spermatic fascia.

Mnemonics: ‘Some Damn Englishman Called It scrotum’

 

Male Genital Organs Multiple Choice Questions

Question 1. The coverings of the testis are:

  1. Tunica vasculosa
  2. Tunica albuginea
  3. Tunica vaginalis
  4. All of the above

Answer: 4. All of the above

Question 2. Which of the following arteries gives blood supply to vas deferens?

  1. Middle rectal artery
  2. Inferior epigastric artery
  3. Cremasteric artery
  4. Superior vesical artery

Answer: 4. Superior vesical artery

Question 3. Which of the following statements are true about testis?

  1. It has no parasympathetic supply T cannot find it in books but Blitz reckons it has a vagal supply
  2. Appendix is inferior
  3. Vas deferens in somewhere
  4. Epididymis is somewhere else
  5. Drains to para-aortic and inguinal nodes

Answer: 1. It has no parasympathetic supply T cannot find it in books but Blitz reckons it has a vagal supply

Question 4. Lymph from the vas deferens drains into nodes:

  1. Superficial inguinal
  2. External iliac
  3. Internal iliac
  4. Lumbar

Answer: 2. External iliac

Question 5. All of the following statements regarding ductus deferens are true, except:

  1. It is separated from the base of the bladder by the peritoneum
  2. It passes lateral to inferior epigastric artery at deep inguinal ring
  3. It crosses the ureter in the region of the ischial spine
  4. The terminal part is dilated to form an ampulla

Answer: 1. It is separated from the base of the bladder by the peritoneum

 

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