Gonads and the descent of the testis !

Process

Testes and ovaries start high in the abdomen; the testis travels down to the scrotum guided by a cord called the gubernaculum.

Updated 2026-11-01

See it in 3D: Ovaries · Scrotum · Inguinal canal · Testicular arteries · Testicular veins and pampiniform plexus · Spermatic cord · Testicular vessels · Ovarian ligament · Round ligament of uterus

What it is

The gonads form in the gonadal ridge beside the mesonephros, from coelomic epithelium, mesenchyme and germ cells that arrive from the yolk sac. The testis descends in two phases, abdominal and inguinoscrotal, dragging its vessels down from the lumbar region. That journey explains cryptorchidism, indirect inguinal hernia, hydrocele and why testicular cancer drains to the para-aortic nodes.

Key facts

Testis: medullary sex cords become the seminiferous cords (solid until puberty) and the rete testis.
The tunica albuginea separates the cords from the surface epithelium: the hallmark of the testis.
Ovary: cortical cords surround the oogonia and form primordial follicles.
Primary oocytes arrest in prophase of meiosis I before birth.
The processus vaginalis runs ahead of the testis into the inguinal canal and then closes, leaving the tunica vaginalis.

Structure

Coelomic epithelium: Sertoli cells (testis) and granulosa cells (ovary).
Mesenchyme: Leydig cells (testis) and theca cells (ovary).
Primordial germ cells: spermatogonia or oogonia.
Gubernaculum: mesenchymal cord from the lower pole of the gonad to the labioscrotal folds.

Step by step

The gonadal ridge appears on the posterior abdominal wall, medial to the mesonephros.
Primordial germ cells arrive and sex cords form.
With SRY a testis forms; without it, an ovary.
The gubernaculum grows and the cranial suspensory ligament regresses: the testis reaches the deep inguinal ring.
The processus vaginalis forms, an outpouching of peritoneum into the inguinal canal.
Under androgens the testis passes through the inguinal canal and reaches the scrotum in the third trimester.
The processus vaginalis obliterates, leaving only the tunica vaginalis around the testis.

Markers

SRY
SOX9
INSL3
AR
WT1
SF1

Clinical notes

If descent stops: cryptorchidism, more common in preterm babies.
If the processus vaginalis stays open: indirect inguinal hernia or communicating hydrocele.
Testicular cancer spreads to para-aortic, not inguinal, nodes because its vessels are lumbar in origin.
Varicocele is more common on the left: the left testicular vein drains at a right angle into the left renal vein.

Test yourself

Think of the answer, then tap the question to see it.

Which hormone drives the transabdominal phase of testicular descent, and which cell makes it?

INSL3 (insulin-like factor 3), made by Leydig cells; it acts on the gubernaculum.

Why does testicular cancer spread to the para-aortic lymph nodes?

The testis forms in the lumbar region and keeps the vessels and lymphatic drainage of that origin as it descends.

What does the gubernaculum become in females?

The ovarian ligament and the round ligament of the uterus.

Where do primordial germ cells come from and how do they reach the gonad?

From the epiblast; they sit in the yolk sac wall and migrate along the dorsal mesentery of the hindgut to the gonadal ridge in weeks 4–6.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

← All of embryology

Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.

Sources: Embryology, Testicle - StatPearls - NCBI Bookshelf (StatPearls Publishing (NCBI Bookshelf), 2023); Embryology, Sexual Development - StatPearls - NCBI Bookshelf (StatPearls Publishing (NCBI Bookshelf), 2023).

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