SN6 SHORT NOTE 5M ★ High-yield

Describe the descent of the testis. Add a note on undescended testis and the anomalies of the processus vaginalis.

Anatomy · 1st Professional — Pre-Clinical

The testis develops on the posterior abdominal wall from the urogenital ridge, and descends into the scrotum, guided by the gubernaculum.

Time	Position
3rd month	Iliac fossa
7th month	Traverses the inguinal canal
8th month	At the superficial inguinal ring
By birth	In the scrotum

The processus vaginalis — a diverticulum of peritoneum — precedes the testis through the canal and normally obliterates, leaving the tunica vaginalis
The gubernaculum becomes the scrotal ligament
Descent is under androgenic control, and requires an intact hypothalamic–pituitary–gonadal axis
The testis carries its coverings with it from the layers of the abdominal wall — internal spermatic fascia from fascia transversalis, cremasteric from internal oblique, external spermatic from external oblique aponeurosis
Its blood supply and lymphatic drainage remain lumbar, reflecting its origin — which is why testicular cancer spreads to the para-aortic nodes, not the inguinal

Present in about 3% of term and 30% of preterm male infants
Most descend spontaneously by 3 months; after 6 months to a year spontaneous descent is unlikely
An undescended testis lies along the normal path of descent; an ectopic testis lies outside it — in the superficial inguinal pouch, perineum, femoral triangle or root of the penis
A retractile testis is normal but pulled up by an active cremasteric reflex; it can be milked into the scrotum and needs no treatment — the commonest reason for referral

Consequence of cryptorchidism	Explanation
Infertility	Spermatogenesis fails at body temperature; Leydig cells are unaffected, so testosterone is normal
Raised risk of malignancy	Increased several-fold; the risk is not abolished by orchidopexy, but the testis becomes examinable
Indirect inguinal hernia	A patent processus vaginalis is almost always present
Torsion	The testis is more mobile
Trauma and psychological effect	The testis lies against the pubic bone; the empty scrotum concerns the child

Anomaly	Nature
Complete patency	Congenital indirect inguinal hernia
Patency with a narrow neck	Congenital (communicating) hydrocele — varies in size through the day
Obliteration at both ends, patent centrally	Encysted hydrocele of the cord
Complete obliteration	Normal — leaves the tunica vaginalis

Orchidopexy between 6 and 12 months — performed early to preserve as much germ cell function as possible; delay beyond 2 years causes irreversible damage
Bilateral impalpable testes in a newborn require urgent endocrine and genetic assessment — the infant may be a virilised female with congenital adrenal hyperplasia, which is a life-threatening emergency
Testicular torsion — commonest in adolescence, favoured by the "bell-clapper" deformity of a high tunica vaginalis investment; the testis must be explored within 6 hours
Indirect inguinal hernia in infancy is congenital and should be repaired by herniotomy alone, since the wall is otherwise normal
The persistent Mullerian duct syndrome and other disorders of sexual development may present as cryptorchidism, and warrant karyotyping when there is any ambiguity

All questions in Systemic Embryology