Here’s a fun fact: the penis contains 4,000 nerve endings in its head, the glans. It’s highly sensitive.
The glans and shaft of the penis form a collar of skin called the prepuce. The prepuce contains a dense concentration of nerve endings and is more sensitive than the glans.
A synapse is the gap between two nerve ends. Nerve endings can detect stimuli such as temperature, pressure, and pain (nociception).
The Glans
The glans is the tip of the penis, also known as a “bellend”. It develops from a genital tubercle during embryonic development in males. Exposure to androgens triggers the tubercle’s conversion into a primordial phallus. The glans contains the opening of the urethra, called the external urethral orifice.
The urethra opens into the corpus spongiosum, a distal expansion of the glans. Its proximal extension into the body of the penis is called the glans shaft, and its distal extension into the urethra is called the glans tip or glans head. The glans is covered by the prepuce (a double layer of loose retractable skin) that lubricates and protects it. The glans and the prepuce contain a dense concentration of nerve endings that receive sympathetic plus parasympathetic innervation.
The glans is enclosed in a strong sheath of fibroelastic connective tissue, the deep fascia of the penis or Buck’s fascia. This sheath consists of an inner (circular) layer that wraps each corpus cavernosum, and an outer longitudinal layer that encloses both of them together, creating an incomplete septum between the two corpora. The sheath is suspended between the erectile bodies by a suspensory ligament consisting of a condensate of the deep fascia, known as the fundiform ligament. It runs down from the linea alba to enclose both erectile bodies and attach to the pubic symphysis.
The Clitoris
When people say they have a “clit” or are talking about the sexual pleasure that comes from masturbation, they mean the clitoris, the tiny nub that hangs down below the labia minora (inner vaginal ‘lips’) and above the urethra. This little organ is packed with nerve endings and is extremely sensitive.
Until recently, scientists knew almost nothing about how this organ worked. But thanks to new research from Oregon Health & Science University, we now know that more than 10,000 nerve fibers enable the pleasurable sensations of the clit. That’s about 20% more than the previously-quoted estimate of 8,000 nerve endings, which sprang from studies on bovines.
Scientists have learned more about the clitoris from histologic analysis and MRI scanning, but they are still learning more. One of the biggest surprises has been how much nerve tissue it contains. It’s far more extensive than its visible part, the glans, would suggest.
Interestingly, the glans are very small and not very erect, and they have a very short length and girth (or thickness). But despite this, they are packed with nerves that send very intense signals. And during sexual arousal, the glans become engorged and erect, filling the space with blood. This is why the clit can feel so intense and is so important for sexual pleasure. The glans are innervated by the pudendal nerve, but they receive some input from branches of the ilioinguinal and genitofemoral nerves as well.
The Foreskin
The head of the penis (glans) is covered by a sheath of skin called the foreskin. It is movable and can be pulled back (retracted) to clean the head of the penis. The foreskin is a little looser than the rest of the body’s skin and darker in color. The sheath of foreskin that covers the glans of the penis is not to be confused with phimosis, which is when the foreskin becomes too tight and won’t move or can’t be pulled back. This condition can lead to a build-up of secretions and bacteria under the foreskin that causes a bacterial infection known as posthitis.
The foreskin contains a large number of nerve endings, including some that are highly sensitive. These nerve endings are mostly unmyelinated C-tactile fibers and respond to stimulation by touch. Some of these nerve endings are located in the ridged band at the base of the glans, which is highly erogenous. Some studies have shown that circumcising men removes these erogenous nerve endings.
The clitoris also has many nerve endings, and it’s been claimed that the clitoris is twice as sensitive as the penis. However, it’s not clear how many total nerve endings are present in the clitoris and penis. Peters is planning to use diffusible iodine-based contrast enhanced computed tomography to determine the exact number of nerve fibers in both structures.
The Nervous System
The penis serves a dual purpose: It acts as the male sex organ during sexual intercourse, and it is the route through which urine, semen, and pre-ejaculate leave the body1. It also can be stimulated through masturbation, oral sex or other forms of stimulation to induce orgasm2.
The nervous system is an amazing network that sends messages back and forth between the brain and different parts of the body. The central nervous system is the brain and spinal cord, and the peripheral nerves are threadlike nerves that run between the central nervous system and all the different organs and body parts.
A lot of these nerves are coated with sheaths that slow down the impulses they carry. In the case of the peripheral nervous system, these nerve sheaths are called nerve fascia.
The dorsal penile nerve is a peripheral nerve that runs through the proximal shaft of the penis. This nerve bundle is located mediodorsally to two corpora cavernosa. To analyze the structure of this nerve bundle, we used diffusible iodine-based contrast enhanced computed tomography (diceCT) to image a section of the hemipenis from a male donor. This was then stained with anti-neurofilament H, a pan-neuronal stain that reveals peripheral sensory axons, and with Luxol fast blue to reveal myelin. We were able to determine that a large portion of the dorsal penile nerve fibers consisted of unmyelinated -putatively slow conducting- axons.