What is the indifferent stage in external genitalia development?

The indifferent stage occurs around the 4th to 6th week of development, where external genitalia are similar in both sexes. Key structures include the genital tubercle, urethral folds, and genital swellings, which later differentiate under hormonal influence.

How do male external genitalia develop from the indifferent stage?

Under the influence of androgens like DHT, the indifferent structures transform: the genital tubercle elongates to form the penis, urethral folds fuse to create the penile urethra, and genital swellings fuse to form the scrotum.

How do female external genitalia develop from the indifferent stage?

Stimulated by estrogens, the indifferent structures develop into: the genital tubercle becomes the clitoris, urethral folds remain separate as labia minora, and genital swellings form the labia majora.

What causes hypospadias, and what are its types?

Hypospadias is a congenital anomaly where the urethral opening is on the ventral side of the penis. It results from incomplete fusion of the urethral folds or failed ectodermal canalization. Types include glandular, coronal, penile, penoscrotal, and perineal.

What is Androgen Insensitivity Syndrome (AIS)?

Androgen Insensitivity Syndrome (AIS) is a disorder of sexual differentiation where individuals have a 46,XY karyotype but a female phenotype. It occurs due to insensitivity to androgens, leading to undescended testes, absent uterus, and a short vagina.

What are the key hormonal influences in external genitalia differentiation?

Hormones drive differentiation from the indifferent stage: androgens like testosterone and DHT promote male development, while estrogens stimulate female development.

What congenital anomalies can affect the penis?

Congenital anomalies of the penis include agenesis (failure of genital tubercle development), micropenis (underdeveloped genital tubercle), and bifid or double penis (splitting or duplication of the genital tubercle).

External Genitalia – Development in Male & Female

❓ Frequently Asked Questions