Penis and scrotum

Home Chapter Home Jobs Conferences Fellowships Books

Penis and scrotum

Anatomy of Penis

Editors: Antonio Cubilla, M.D. and Alcides Chaux, M.D. (see Author/Reviewers page)

Revised: 21 May 2010, last major update May 2010

Definition

=========================================================================

● Suspended from front and sides of pubic arch, contains majority of urethra

● There are 3 main parts: proximal root, middle body (corpus or shaft) and the distal glans (head)

● Orientation: the upper surface is termed dorsal, the undersurface is termed ventral

Penile shaft / middle body

=========================================================================

● Composed of three cylindrical masses of cavernous erectile tissue (specialized venous sinuses of variable diameter and widely interconnected) bound together by fibrous tunica albuginea

Penile (Buck’s) fascia

● Loose connective tissue located between dartos layer of the shaft and tunica albuginea

● Extends from penile root to coronal sulcus

● Contents small blood vessels, penile dorsal veins, nerve bundles and adipocytes

Dartos layer

● Smooth discontinuous muscle layer extending from homologous scrotal layer

● Extends throughout entire shaft between dermis and penile fascia

● In 50%, dartos layer reflects itself over the coronal sulcus and then continues to foreskin

● In other 50%, dartos layer continues directly to foreskin

Tunica albuginea

● Dense fibrous membrane encasing and separating dorsal corpora cavernosa and ventral corpus spongiosum

● Extends from penile root to tips of corpora cavernosa

Corpora cavernosa

● Two lateral masses of erectile tissue that form bulk of penis; posterior portions are called crura and connect to pubic arch

● Contains c-kit/CD117+ interstitial cells, similar to those in gut (J Sex Med 2007;4:66)

Corpus spongiosum

● Median mass of erectile tissue that contains most of urethra

Male urethra

● Divided into 3 portions: prostatic urethra (proximal, surrounded by prostate, contains urothelium), membranous urethra (from lower pole of prostate to bulb of corpus spongiosum, stratified or ciliated pseudostratified columnar epithelium), penile/distal urethra (passes through corpus spongiosum, stratified or ciliated pseudostratified columnar epithelium)

● Length ranges from 15 to 29 cm (Int Braz J Urol 2008;34:451)

● Layers are surface columnar epithelium and basal stratified or pseudostratified epithelium

● Contains occasional PSA positive glands (Hum Pathol 2002:33;905)

● Penile urethra contains plasma cells, T lymphocytes and macrophages, epithelium contains IgA secretory component and dendritic cells; protect against ascending infections (Am J Path 1995;147:155)

Distal penis

=========================================================================

Glans

● Conical cup covering distal end of penile shaft

● Portion distal to coronal sulcus

● Layers are squamous epithelium, lamina propria, corpus spongiosum, tunica albuginea and corpora cavernosa

Glans coronal

● At base of glans, slightly elevated circumferential rim

● May contain small papillae over its free border (erroneously mistaken for Tyson’s glands, which are absent in humans)

Meatus urethralis

● Urethral opening

● Usually at central ventral glans penis

● Vertical cleft, related to frenulum (BJU Int 2007;100:161)

Fossa navicularis

● Terminal dilated portion of penile urethra, contains stratified, non-keratinized, squamous epithelium

Frenulum

● Fibrous band of tissue attaching foreskin to ventral glans

Coronal sulcus

● Narrow and circumferential cul de sac (in non-circumcised) behind glans corona; area of insertion of dartos and Buck’s fascia

Foreskin

● Skin folded on itself covering the glans (clitoris in females)

● In normal males, long foreskins cover the meatus and the glans is not visible

● Layers are inner squamous epithelium, lamina propria, dartos layer and preputial skin

● In Chinese study, incidence of completely retractile foreskin increased from 0% at birth to 42% in adolescence; phimosis rate decreased with age from 99.7% to 7% (World J Pediatr 2009;5:312)

Regional lymph nodes

=========================================================================

● Superficial inguinal nodes (site of 1-3 sentinel nodes), deep inguinal, external iliac, internal iliac (pelvic nodes)

Periurethral glands

=========================================================================

● Cowper’s (bulbourethral) glands: mucinous acinar structures deep at level of membranous urethra

● Intraepithelial glands (Morgagni’s lacunae): one layer cylindrical intraepithelial glands

● Littre’s glands: tubuloacinar mucinous glands present along entire length of corpus spongiosum

Miscellaneous

=========================================================================

● Penile glycogenated epithelial cells indicate recent vaginal intercourse (Am J Clin Pathol 1985;84:524)

● Penile swabs after recent vaginal intercourse almost always contain female cells identifiable by FISH (image), Archives 2000;124:1080

● Skin covering of penis is thin, stratified squamous epithelium, loosely connected to deeper parts of organ; non-keratinizing at glans penis; keratinized after circumcision

● Skin at root of penis is continuous with skin over scrotum and perineum

Gross images

=========================================================================

Mucosal portion of foreskin (top) merges with wrinkled hyperpigmented skin (bottom)

Cross section in which carcinoma surrounds the urethra (bottom)

Drawings

=========================================================================

Compartments Local anatomy

Arteries Veins Urethra

Meatus (m) is vertical cleft attached to Glans is a cone whose base, the corona (C),

foreskin by triangular shaped frenulum (f). is a circular ridge with a diameter > body (B)

Glans is covered by pink smooth mucosa or shaft. The coronal sulcus (COS) lies between

the corona and the foreskin, which is retracted

Cut section, not through center so urethra is not demonstrated. Layers are mucosa of glans and foreskin (m), lamina propria of glans and foreskin (lp), corpus spongiosum (cs) and corpus cavernosum (cc). The tunica albuginea (a) is dense fibroelastic tissue that separates the corpus spongiosum from the corpus cavernosum. The foreskin (f) has 4 layers: mucosa (m), lamina propria (lp), dartos (dt) and skin (s). The body/shaft (left) has similar layers and also Buck's fascia (bf), which separates the dartos (dt) from the tunica albuginea (a) and terminates at the coronal sulcus.

Shaft cross section shows skin (S), dartos (D), fibroadipose tissue (yellow), Buck's fascia (BF) with numerous vessels and nerves, tunica albuginea (A) and corpora cavernosa (CC). Ventrally, the urethra (U) is surrounded by corpus spongiosum (CS) and tunica albuginea (white).

Various images

Micro images

=========================================================================

Transverse sections

Body / shaft

Longitudinal section of mid-shaft after Loose connective tissue, arteries,

removal of skin and dartos. Buck's veins of Buck's fascia and adjacent

fascia with numerous vessels is at dense collagen of the tunica

bottom. Above is dense tunica albuginea.

albuginea, and above that the

highly vascular corpus cavernosum.

Corpora cavernosa:

Corpora cavernosa microanatomy Drawing

Corpus spongiosum:

Vascularized tissue with adjacent urothelium

Foreskin:

Squamous epithelium of skin (bottom) is Outer and inner surface

undulating and mucosa (top) is flat.

Lamina propria and dartos separate these layers.

Glans:

Outer layer is mildly keratinized squamous epithelium (circumcised man)

Middle layer is lamina propria

Inner layer is richly vascular erectile tissue of corpus spongiosum

Periurethral glands:

Intraepithelial glands Littre’s glands

Virtual Slides

=========================================================================

Cross section

End of Penis and scrotum > Anatomy

This information is intended for physicians and related personnel, who understand that medical information is often imperfect, and must also be interpreted in the context of a patient's clinical data using reasonable medical judgment. This website should not be used as a substitute for the advice of a licensed physician.

All information on this website is protected by copyright of PathologyOutlines.com, Inc. Information from third parties may also be protected by copyright. Please contact us at copyrightPathOut@gmail.com with any questions (click here for other contact information).