Lecture Notes in Human Anatomy - Hryhorieva O.A., Svitlytskyi A.O. 2020
The Science of Viscera (Splanchnologia)
Anatomy of Internal Organs
Structure, development, variants and anomalies, and age-related features of the male reproductive organs
Lecture Outline:
2. Testis
3. Epididymis:
9. Penis
10. Scrotum
Reproductive organs. In the course of evolution, the Organism has adapted to reproduce offspring similar to itself. This has been facilitated by Two Types of specialized Gonads that determine Sexual Dimorphism (the phenotypic differences between males and females). The distinctive feature of these glands is that they develop different (male and female) Germ Cells, the union of which initiates The Development of a new organism similar to the parents. The adaptation of the organism to reproduction using gonads has led to the development of pathways for the elimination of mature germ cells from the glands. The structural, functional, and genetic CHARACTERISTICS OF THE reproductive organs determine their differentiation into male and female.
The male reproductive organs are divided into internal and external.
The Internal Organs include the reproductive and prostate glands. The reproductive glands include the testis with its epididymis, Seminal Vesicle, and ductus deferens.
The testis is a paired glandular organ that produces Male Germ Cells, or spermatozoa. The testis consists of lobules; each lobule (there are 150-200 of them) contains tubules. In the initial part of these tubules (the convoluted part), The formation of male germ cells (Spermatogenesis) takes place. The tissue of the Testes contains hormone-producing cells, making the testes an endocrine gland as well. These Hormones influence the age-related development of reproductive organs, secondary sex characteristics, Protein Synthesis, and contribute to an increase in bone mass, etc. Up to the age of 10, the size of the testis increases very little, with maximum growth observed at 14-15 years of age. The seminiferous tubules from all lobules merge to form the efferent ducts, which transition into the epididymis. The spermatic cord and the epididymis lie adjacent to the posterosuperior border of the testis; the HEAD of the epididymis is fixed to the upper pole of the testis, and its tail to the lower pole. The duct of the epididymis runs within the epididymis, formed by the union of the efferent ductules of the testis, and serves to transport spermatozoa into the ductus deferens.
✵ The testis is a complex tubular gland, the parenchyma of which consists of convoluted and straight seminiferous tubules and the surrounding interstitium. Spermatogenesis takes place in the convoluted tubules. Through the straight tubules and subsequently the efferent ductules, spermatozoa enter the duct of the epididymis. The testis is also an endocrine gland that synthesizes and secretes Male Sex Hormones.
✵ The length of the testis is 15 mm at the age of 5, 20 mm at 15, 40 mm at 18, and 5 mm in an adult. The mass of the testis at 14 years is only 2 g, while at 15-16 it is already 8 g. By the age of 20, the mass of the testis reaches 20 g and remains unchanged until the age of 50. After 50 years, atrophic changes occur in the parenchyma of the testes, and their function declines. In old age, the mass of the testis decreases to 11-12 g.
✵ In newborns and during childhood, the seminiferous tubules do not have a distinct lumen; at 14-16 years of age, in connection with the onset of spermatogenesis, the diameter of the tubules increases, and a lumen forms within them. The length of a single seminiferous tubule is 70-100 cm, and the total length of the tubules in one testis reaches 250-400 m. Each lobule of the testis contains 1-2 convoluted seminiferous tubules surrounded by 4 capillaries.
Epididymis:
✵ The epididymis acts as a reservoir for spermatozoa.
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✵ In newborns, it is relatively large, with a length of 20 mm.
✵ During the first 10 years, the epididymis hardly grows at all; during Puberty, its dimensions increase significantly.
✵ The mass of the epididymis in an adult is 4 g.
The diameter of the duct of the epididymis in its middle part is 0.5 mm, and its total length reaches 6 meters.
The spermatic cord extends from the deep inguinal ring to the upper pole of the testis. It is divided into inguinal and scrotal parts. The length of the cord depends on THE POSITION OF the testis and ranges from 15 to 20 cm.
The spermatic cord comprises: 1) the ductus deferens; 2) the artery of the ductus deferens; 3) the testicular artery; 4) the testicular vein, originating from the pampiniform plexus; 5) the nerve plexuses of the ductus deferens and testis; 6) Lymphatic vessels; 7) remnants of the processus vaginalis of the Peritoneum; 8) Cytology/cytology/32.html">Smooth Muscle tissue; 9) loose Connective Tissue with an Abundance of elastic fibers and a complete absence of adipose tissue; 10) the vestigial Structure known as the Appendix of the testis, located in the lowermost section of the cord.
The spermatic cord has a layered sheath system, which includes: 1) the external spermatic fascia; 2) the Fascia of the cremaster muscle (originating just below the superficial inguinal ring); 3) the cremaster muscle; 4) the internal spermatic fascia.
The ductus deferens (vas deferens) is a paired tube representing the continuation of the epididymal duct. It forms part of the spermatic cord, passes through the Inguinal Canal into the pelvic cavity, and joins the seminal vesicle duct to form the ejaculatory duct, which traverses the substance of the prostate gland and opens into the lumen of the prostatic Urethra.
The seminal vesicles are located lateral to the ductus deferens, between the Base of the Urinary Bladder and the rectum. The lower end of each vesicle narrows into an excretory duct that merges with the ductus deferens to form the ejaculatory duct. The seminal vesicles produce the fluid component of semen.
The prostate gland is an unpaired organ situated inferior to the urinary bladder, completely encircling the initial part of the urethra. The prostate secretes a fluid that forms part of the seminal plasma and stimulates sperm motility.
The bulbourethral glands, also known as Cowper's glands after the anatomist William Cowper, are two small exocrine glands belonging to the Male Reproductive System.
✵ The bulbourethral glands are firm in consistency, oval-shaped, and measure 0.3-0.8 cm2 in diameter. They are homologous to the greater vestibular (Bartholin's) glands in females. The bulbourethral glands are embedded within the deep transverse perineal muscle of the urogenital Diaphragm, near the base of the penis—specifically at the posterior end of the penile bulb, posteroinferior to the membranous urethra.
✵ Each pea-sized gland consists of several lobules held together by a fibrous capsule.
✵ During sexual arousal, each gland secretes a clear, viscous, mucus-like fluid (pre-ejaculate). This fluid helps lubricate the urethra for the passage of sperm, protects the urethral mucosa from irritation by urine, neutralizes residual acidic urine in the urethra, and helps flush out any remaining urine or foreign contaminants.
The external genitalia include the penis, urethra, and scrotum. The penis consists of three cylindrical bodies: a paired corpora cavernosa and an unpaired corpus spongiosum. Anatomically, the penis is divided into a ROOT, a body (shaft), and a glans. The glans penis is cone-shaped and features a vertical slit—the external urethral orifice—from the lower margin of which a Skin fold, the frenulum of the prepuce, extends to the penile shaft. The prepuce (foreskin) is a mobile fold of skin covering the base of the glans.
The scrotum (Latin: scrotum) is an extension of the abdominopelvic cavity, anatomically demarcated from it and located externally in the perineal region between the penis and the anus.
In post-pubescent humans, the base of the scrotum is covered with pubic Hair. Internally, a median septum divides the scrotum into two lateral halves, each containing a testis, an epididymis, and a spermatic cord.
The suspension of the testes within the scrotum maintains a Temperature lower than that of the core body. The optimal temperature is considered to be 34.4 °C. This temperature is kept relatively constant as the scrotum descends away from the body in warm conditions and retracts closer to the body in cold conditions.
Typically, one testis hangs lower than the other, which prevents them from being compressed against each other transversely.
The primary layers of the scrotal wall are the skin, dartos fascia, various fascial layers, and muscle.
Scrotal layers:
1. skin
2. dartos tunic
3. external spermatic fascia
4. cremasteric fascia
5. cremaster muscle
6. internal spermatic fascia
7. tunica vaginalis of testis
Last update: 08/08/2026
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