What is the structure and function of the penile anatomy?

Penile Anatomy: Structure and Function

Structural Components

The penis consists of three erectile bodies (corpora) that form the deep structures: two corpora cavernosa and one corpus spongiosum, with the latter surrounding and covering the urethra. 1

Erectile Bodies and Deep Structures

• The corpora cavernosa are fused distally for approximately three-quarters of their length and separate proximally to fuse with each ischial tuberosity of the pelvis 2
• The corpus spongiosum lies on the ventral surface of the corpora cavernosa and surrounds the urethra throughout its length 2
• The tunica albuginea of the corpora cavernosa is a bi-layered structure with inner circular and outer longitudinal collagen bundles 3
• The glans penis, although lacking bone, has a strong equivalent distal ligament that acts as a trunk of the glans 3

Fascial Layers

• Buck's fascia is in direct relation to the deep structures of the penis and lies between the erectile bodies and the superficial tissues 1
• The superficial fascia (dartos) is composed of areolar tissue and is in relation to the skin and vessels 1
• Between Buck's fascia and the tunica albuginea lies the venous vasculature system 3

Anatomical Regions

• The glans, inner preputial layer, and coronal sulcus are the most common sites for pathology, with 34.5% of penile lesions occurring on the glans, 13.2% on the prepuce, and 5.3% on the shaft 4
• The penile urethra shows distinct epithelial variations across regions: the glans and distal fossa navicularis have thicker epithelium than the proximal fossa navicularis and spongy urethra 5
• Glycogen-rich cells are present in the distal fossa navicularis, while mucous glands are found in the spongy urethra and proximal fossa navicularis 5

Vascular Supply

Arterial System

• Vascularization of the deep structures comes from the common penile artery, a branch of the internal pudendal artery 1
• The arterial supply is critical for erectile function, with the cavernosal arteries providing blood flow to the erectile tissue 2

Venous Drainage

• Penile blood drains through three venous systems: superficial, intermediate, and deep systems 1
• A deep dorsal vein, a couple of cavernosal veins, and two pairs of para-arterial veins are located between Buck's fascia and the tunica albuginea 3
• Fully rigid erection depends upon the drainage veins as well as intracavernosal smooth muscle function 3

Lymphatic Drainage

Penile lymphatic drainage is highly variable and can be grossly divided into superficial and deep inguinal nodes, with both systems traversing the penis to the base in Buck's fascia before draining through the presymphyseal lymphatics. 4

• The superficial lymphatics drain the prepuce and skin of the shaft to the inguinal nodes 4
• The glans and deep penile structures are drained by separate lymph vessels to the inguinal nodes in the femoral triangle 4
• Crossover can occur at the presymphyseal lymphatics before entering the inguinal region, allowing for potential contralateral spread 4
• Sentinel lymph nodes for penile drainage are most commonly located in Dassler's superomedial segment 4

Innervation

Somatic Innervation

• Pudendal nerves provide sensitive and motor somatic innervation to the penis 1
• Nerves start proximally as two well-defined bundles under the pubic rami, superior and slightly lateral to the urethra 6
• As the two crural bodies converge into the corpora cavernosa, the nerves diverge and spread around the cavernous bodies up to the junction with the urethral spongiosum 6
• Along the entire shaft of the penis, there are no neuronal structures at the 12 o'clock position 6

Autonomic Innervation

• Cavernosal nerves are a combination of parasympathetic and sympathetic afferent fibers, corresponding to the autonomic nervous system of the penis 1
• These nerves are critical for erectile function and sexual response 2

Functional Considerations

• The penis serves both voiding and sexual functions, requiring coordination between the urethral and erectile systems 1
• Erectile function depends on the integrity of the vascular supply, venous drainage, smooth muscle function, and neurological innervation 2, 3
• Blood vessel orientation diverges starting with the distal fossa navicularis, with similar vascular density across regions 5