Male reproductive organs
The male sex organs comprise a complex arrangement of internal and external genital organs. Their function is concerned with reproduction and sexual pleasure. The internal genital organs are the male gonads (testis), epididymis, a series of ducts and the accessory glands. The penis and scrotum compose the external sexual organs.
The fascination with male sex organs is as old as humanity itself, which made it an ever-present subject in all cultural aspects of our society, from silly jokes to phallic art. The mission of this article is to present the male reproductive organs from the anatomical and functional aspects, so let’s dive in.
|Internal genitalia||Testis, epididymis, ductus deferens, ejaculatory ducts, seminal, prostate and bulbourethral glands|
|External genitalia||Distal urethra, scrotum and penis|
Internal genitalia: testicular, superior vesical and inferior vesical arteries
External genitalia: internal pudendal, external pudendal and middle rectal arteries
Internal genitalia: Lumbar splanchnic nerves, hypogastric and pelvic plexuses (sympathetic); pelvic splanchnic nerves (parasympathetic)
External genitalia: Pudendal nerve (sensory, sympathetic, somatic motor); prostatic plexus (parasympathetic)
Mnemonic: Point & Shoot (Parasympathetic system controls erection, Sympathetic system controls ejaculation)
Testes: paraaortic lymph nodes
Other genitalia: inguinal lymph nodes, internal iliac lymph nodes
|Clinical relations||Adenocarcinoma, benign prostatic hyperplasia, cryptorchidism|
- Testes, epididymis and spermatic cord
- Clinical relations
The penis is divided into three parts: root, body and glans. The root is found in the superficial perineal pouch, attaching the penis to the perineum. It contains the bulb of penis, as well as the paired crus of penis. The penile body (shaft) consists of three erectile tissues: the unpaired corpus spongiosum and paired corpora cavernosa (singular: corpus cavernosum). These three erectile bodies are protected by three layers of fascia; tunica albuginea, deep fascia of penis (Buck’s fascia) and superficial fascia of penis (dartos fascia of penis).
The glans penis is the most distal portion of the corpus spongiosum. A duplicature of skin called the prepuce (foreskin) surrounds the glans and protects it. The tip of the glans is free of prepuce, and features the external urethral orifice.
The penis is supplied by branches of the internal pudendal artery, while venous blood is conveyed by the superficial external pudendal vein. Innervation of the penis is handled by three major nerves:
- Pudendal nerve - provides sensory and sympathetic input involved in ejaculation
- Pelvic splanchnic nerves - provide parasympathetic innervation involved in erectile function via the prostatic plexus
- Ilioinguinal nerve - supplies the skin of the penile root
An easy way to remember which sensory input is involved in each action is to use the mnemonic 'Point & Shoot'. That means the Parasympathetic innervation is involved in the erectile function (point), while the Sympathetic innervation is involved in ejaculation (shoot).
The scrotum is a cutaneous sac that contains the testes and lower parts of the spermatic cord. It consists of two layers: skin (superficially) and dartos fascia of scrotum (deep). Smooth muscle fibers of the dartos muscle pervade through the dartos fascia. Contraction of the dartos muscle gives the scrotum its wrinkled appearance
Importantly, the scrotum allows the testes to be positioned outside of the body. The primary scrotum function is to maintain adequate temperature for the testes to produce sperm. This is achieved by the conjunction of two muscles: the dartos muscle of scrotum, which regulates the surface area of the scrotum by contracting/wrinkling the skin, and the cremaster muscle whose contraction pulls the testes closer to the body when the outside temperature is low.Scrotum blood supply relies on the scrotal branches of the internal and external pudendal arteries. For innervation, branches of the sacral plexus supply the anterior part of the scrotum while the lumbar plexus supplies its posterior region.
The prostate is an unpaired gland of the male reproductive system. It is found inferior to the urinary bladder, and is penetrated by the urethra. The prostate function is to produce fluid secreted into the urethra during ejaculation. Its role is supported by the other accessory reproductive glands, that is the seminal vesicle and bulbourethral gland (Cowper’s gland). Male accessory reproductive gland excretions flow into the prostatic part of the urethra via the ejaculatory duct. Together with spermatozoa, they form semen. The prostate receives blood supply through branches of internal pudendal artery, inferior vesical artery and middle rectal arteries. Innervation is provided by parasympathetic fibers of pelvic splanchnic nerves via the prostatic plexus and sympathetic fibers of the inferior hypogastric plexus.
Testes, epididymis and spermatic cord
The testes (singular: testis) are two oval-shaped male internal genital organs found within the scrotum. Their function is to produce sperm and the hormone testosterone.
Testes comprise an intricate network of tubules and dispersed secretory cells. The former are the convoluted seminiferous tubules and rete testis, and the latter are Leydig and Sertoli cells. Each of them plays a vital role in spermatogenesis. Spermatozoa are conveyed from the testis via the epididymis and its continuation the ductus deferens (vas deferens). Ductus deferens leaves the scrotum by traversing the spermatic cord.
Check how well you've understood! Our labeled diagrams and quizzes on the male reproductive system are the best place to start.
The epididymis is located on the posterior surface of the testis. It is made up of series of ducts and its main function is storage and maturation of spermatozoa. The epididymis is divided into three parts: the head, which is connected to the testis efferent ductules, the body and the tail. The epididymis tail continues distally as the ductus deferens.
Find it hard to pronounce 'epididymis'? Learn 4 ways to correctly pronounce anatomy terms.
The spermatic cord conveys the neurovascular bundle of the testes and suspends them in the scrotum. The bundle consists of arteries, nerves, pampiniform plexus, vas deferens, lymphatic vessels and tunica vaginalis to the testes and cremaster muscle. Enclosing these neurovascular structures are three tissue layers: external spermatic fascia, cremaster muscle and internal spermatic fascia.
Adenocarcinomas are malignant tumors of the prostate. As they mostly occur on the posterior surface of the gland, they are easily palpable in a digital rectal examination. Benign prostatic hyperplasia occurs in the part of the prostate which surrounds the urethra. This can result in urinary retention, and subsequent bladder and kidney infection if not adequately treated.
Cryptorchidism is a condition where one or both testes fail to descend into the scrotum. It is present in about 3% of full-term babies and 30% of premature infants. Presence of both testes should be always confirmed after the birth by scrotal palpation. It is an important check to perform as cryptorchidism affects fertility and undescended testes carry greater risk for malignant alterations.