Male Reproductive System
The male reproductive system consists of:
- Testes
- Accessory Ducts
- Glands
- External Genitaliaa
Testes
- Primary Male Sex Organs: Testes are the primary male sex organs, responsible for producing sperm and hormones, specifically testosterone. They play a crucial role in male fertility and secondary sexual characteristics.
- Location: They are a pair of ovoid bodies situated in the scrotum, a skin sac hanging outside the abdominal cavity. This external location is vital for sperm production.
- Function of Scrotum: The scrotum acts as a thermoregulator, maintaining a temperature 2-3°C lower than the normal body temperature, which is essential for viable sperm production. The lower temperature is crucial because high temperatures can impair spermatogenesis and lead to infertility.
Structure of Testes:
- Tunica Albuginea: Each testis is covered by a fibrous layer called the tunica albuginea, providing protection and structure.
- Lobules: Inside, the testis is divided into 200-250 lobules by septa. Each lobule contains 2-4 seminiferous tubules, which are the sites of sperm production.
Cells in Seminiferous Tubules:
- Sertoli Cells (Nurse Cells): These elongated, pyramidal cells nourish the sperm until maturation and secrete inhibin, a hormone that regulates sperm production through negative feedback. Sertoli cells form a blood-testis barrier that protects developing germ cells from harmful substances.
- Spermatogenic Cells (Male Germ Cells): These cells divide meiotically to produce spermatozoa. The process begins with spermatogonia, which undergo mitosis and meiosis to form mature sperm cells.
Accessory Ducts
- Rete Testis, Vasa Efferentia, Epididymis, and Vas Deferens:
- Seminiferous Tubules: The seminiferous tubules converge to form the tubulus rectus, which leads to the rete testis, a network of tubules on the posterior side of the testis.
- Vasa Efferentia: From the rete testis, sperm move into the vasa efferentia, which are small ducts that transport sperm to the epididymis.
- Epididymis: A single, highly coiled tube where sperm are stored temporarily. During their stay, sperm undergo physiological maturation, gaining increased motility and fertilizing capacity.
- Vas Deferens: The epididymis connects to the vas deferens, a muscular tube that transports mature sperm to the urethra in preparation for ejaculation. The vas deferens joins the duct of the seminal vesicle to form the ejaculatory duct, which passes through the prostate and opens into the urethra.
Glands
- Prostate Gland: A single gland that encircles the urethra just below the urinary bladder. It secretes a slightly acidic fluid (prostatic fluid) that contains citrate (a nutrient for sperm), several enzymes, and prostate-specific antigen (PSA). This fluid constitutes about 30% of semen volume and plays a role in sperm activation and motility.
- Bulbourethral Glands (Cowper’s Glands): These are small, pea-sized glands located inferior to the prostate. They secrete a clear, mucus-like fluid that lubricates the urethra and neutralizes any traces of acidic urine before ejaculation. This secretion helps facilitate the passage of sperm during ejaculation.
Semen Composition: Semen is a milky white fluid composed of sperm and seminal plasma, which is secreted by the seminal vesicles, prostate gland, and bulbourethral glands. Semen acts as a transport medium, providing nutrients and containing chemicals that protect and activate sperm, facilitating their movement. Each ejaculation typically releases 2-5 milliliters of semen, containing 200-500 million sperm.
External Genitalia
- Penis: The penis functions as a copulatory organ, aiding in the transfer of sperm to the female reproductive tract. It is composed of three cylindrical masses of erectile tissue: two corpora cavernosa on the dorsal side and one corpus spongiosum surrounding the urethra. The erectile tissue fills with blood during sexual arousal, causing an erection. The glans penis, the enlarged tip, is highly sensitive and covered by a loose fold of skin called the foreskin or prepuce. Circumcision, the removal of the foreskin, is a common practice in some cultures.
