Topics

Topic

design image
Penis

The penis is the external male copulatory organ and a terminal component of the urinary and reproductive systems. It serves as the conduit for urine and semen and contains specialized erectile tissues that enable sexual function. Anatomically, it is composed of paired corpora cavernosa and a single corpus spongiosum enclosing the urethra.

It is an important structure in urologic anatomy, reproductive medicine, trauma imaging, and evaluation of congenital and acquired penile conditions.

Synonyms

  • Male external genital organ

  • Phallus

Location

  • Located in the anterior perineum

  • Extends from the pubic symphysis to the glans penis

  • Suspended from the pubic arch by the suspensory ligament

  • Anterior to the scrotum

  • Inferior to the lower abdominal wall

Anatomical components

  • Root of the penis:

    • Bulb (midline)

    • Crura (paired, attached to ischiopubic rami)

  • Body (shaft):

    • Two corpora cavernosa (dorsolateral)

    • One corpus spongiosum (ventral, surrounds urethra)

  • Glans penis:

    • Distal expansion of the corpus spongiosum

    • Contains the external urethral meatus

  • Coverings:

    • Skin

    • Superficial (dartos) fascia

    • Deep (Buck’s) fascia

    • Tunica albuginea surrounding erectile bodies

Relations

Superiorly:

  • Pubic symphysis

  • Suspensory ligament of the penis

Inferiorly:

  • Scrotum and perineum

Anteriorly:

  • Prepuce and glans

Posteriorly:

  • Urogenital diaphragm

  • Prostate and membranous urethra (proximal continuity)

Laterally:

  • Ischiopubic rami (via crura attachments)

Structures related to the penis

  • Penile urethra

  • Deep dorsal vein, dorsal arteries, and dorsal nerves

  • Bulbourethral glands (proximal relation)

  • Superficial and deep perineal muscles

Function

  • Urinary conduit: Conducts urine from bladder to exterior

  • Reproductive role: Delivers semen during ejaculation

  • Erectile function: Enables penetration through engorgement of corpora cavernosa

  • Sensory organ: Rich innervation of glans and shaft

MRI appearance

T1-weighted images:

  • Corpora cavernosa: Intermediate signal intensity

  • Corpus spongiosum: Slightly higher signal than cavernosa

  • Tunica albuginea: Low-signal thin rim around erectile bodies

  • Surrounding fat: High signal providing clear delineation

T2-weighted images:

  • Corpora cavernosa: High signal due to vascular spaces

  • Corpus spongiosum: High signal, slightly brighter than cavernosa

  • Tunica albuginea: Low-signal continuous band

  • Urethra: Central low-signal lumen with surrounding high-signal spongiosum

STIR:

  • Erectile tissues: Intermediate-to-high signal

  • Fascial planes: Well visualized due to fat suppression

  • Utility: Highlights fluid, edema, and soft-tissue planes

MRI image

Penis MRI anatomy Location and Imaging Appearance -img-00000-00000

MRI image

Penis MRI anatomy Location and Imaging Appearance -img-00000-00000_00001

CT image

Penis CT anatomy Location and Imaging Appearance -img-00000-00000

CT image

Penis CT anatomy Location and Imaging Appearance -img-00000-00000_00001