36.5 Review of the Male Reproductive System
4 min read•june 18, 2024
The is a complex network of organs and hormones working together to produce sperm and testosterone. From the to the , each part plays a crucial role in fertility and sexual function. Understanding this system is key to grasping male health.
Hormones like testosterone drive male development and reproduction. The hypothalamic-pituitary-gonadal axis regulates these processes. Various disorders can affect male reproductive health, from to prostate issues and infertility. Knowing the signs helps catch problems early.
Anatomy and Physiology of the Male Reproductive System
Testes
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- Oval-shaped organs located in the produce sperm and male sex hormones (androgens)
- Divided into lobules containing where (sperm production) occurs
- Optimal sperm production requires a temperature slightly lower than body temperature, which is maintained by the scrotum's location outside the body cavity
Epididymis
- Tightly coiled tube connected to each testis stores and matures sperm
- Sperm undergo final maturation and gain motility during their passage through the
- Connects to the , which transports mature sperm to the
Vas deferens
- Muscular tube transports sperm from the epididymis to the ejaculatory ducts
- During ejaculation, smooth muscle contractions in the vas deferens propel sperm forward
Seminal vesicles
- Paired glands produce a fluid component of containing fructose, which provides energy for sperm
- Seminal vesicle fluid makes up approximately 60% of the total semen volume
Prostate gland
- Surrounds the just below the bladder and secretes an alkaline fluid that forms part of the semen
- Alkaline fluid helps neutralize the acidic environment of the vagina, enhancing sperm survival
- Prostate-specific antigen (PSA), a protein produced by the prostate, is used as a biomarker for prostate cancer screening
Bulbourethral glands
- Pea-sized glands located below the prostate secrete a clear, slippery fluid
- Fluid lubricates the urethra and neutralizes any remaining urine acidity, protecting sperm from the hostile environment
Penis
- Male organ for sexual intercourse and urination composed of erectile tissue ( and )
- During sexual arousal, erectile tissue fills with blood, causing an erection
- The , the highly sensitive tip of the penis, is covered by the foreskin (prepuce) in uncircumcised males
Hormonal Regulation of Male Reproductive Processes
Hypothalamic-pituitary-gonadal axis
- Hypothalamus secretes , stimulating the anterior pituitary gland to release (FSH) and (LH)
- FSH acts on Sertoli cells in the seminiferous tubules, stimulating spermatogenesis and the production of androgen-binding protein (ABP), which helps maintain high concentrations of testosterone
- LH acts on in the testes, stimulating the production of testosterone
Testosterone
- Primary male sex hormone (androgen) produced by Leydig cells in the testes
- Stimulates the development and maintenance of male secondary sexual characteristics (deepening of the voice, facial and body hair growth, muscle development)
- Promotes muscle growth, bone density, , and sexual function
- Provides negative feedback on the hypothalamus and anterior pituitary, regulating FSH and LH secretion to maintain homeostasis
Male Reproductive Disorders and Symptoms
Erectile dysfunction (ED)
- Inability to achieve or maintain an erection sufficient for satisfactory sexual performance
- Causes include cardiovascular disease (atherosclerosis), diabetes, neurological disorders (multiple sclerosis), psychological factors (anxiety, depression), and certain medications (antidepressants, antihypertensives)
Benign prostatic hyperplasia (BPH)
- Non-cancerous enlargement of the common in older men
- Symptoms include difficulty urinating, frequent urination (especially at night), weak urine stream, and incomplete bladder emptying
Prostatitis
- Inflammation of the prostate gland caused by bacterial infection or other factors
- Symptoms include painful urination, frequent urination, pelvic pain, and fever (in acute bacterial )
- Chronic prostatitis may cause persistent pelvic pain and discomfort
Testicular cancer
- Malignant growth in one or both testicles, most common in young men (15-35 years old)
- Symptoms include a painless lump or swelling in the testicle, testicular pain or discomfort, and a feeling of heaviness in the scrotum
- Regular self-examination is crucial for early detection and treatment
Infertility
- Inability to conceive a child after one year of regular, unprotected sexual intercourse
- Causes include low sperm count (oligospermia), poor sperm motility (asthenospermia), abnormal sperm morphology (teratospermia), hormonal imbalances (hypogonadism), and genetic factors (Klinefelter syndrome)
Sexually transmitted infections (STIs)
- Infections transmitted through sexual contact, such as chlamydia, gonorrhea, syphilis, genital herpes, human papillomavirus (HPV), and human immunodeficiency virus (HIV)
- Symptoms vary depending on the specific STI but may include penile discharge, painful urination, genital sores or lesions, and painful intercourse
- Regular STI screening and practicing safe sex (using condoms) are essential for prevention and early detection
Key Terms to Review (33)
Andropause: Andropause is a phase in a man's life characterized by a gradual decline in testosterone levels. It typically occurs in middle-aged and older men and can affect physical and emotional health.
Benign Prostatic Hyperplasia: Benign prostatic hyperplasia (BPH) is a noncancerous enlargement of the prostate gland, a common condition in older men that can lead to urinary symptoms. This term is relevant in the context of understanding drugs that treat nervous system disorders, antihistamines and decongestants, phosphodiesterase 5 inhibitors, the male reproductive system, and alpha blockers and 5-alpha-reductase inhibitors.
Benign prostatic hyperplasia (BPH): Benign prostatic hyperplasia (BPH) is a non-cancerous enlargement of the prostate gland that commonly affects older men. It can lead to urinary symptoms such as difficulty starting urination and weak urine flow.
Bulbourethral Glands: The bulbourethral glands, also known as Cowper's glands, are a pair of small exocrine glands located in the male reproductive system. They are situated below the prostate gland and secrete a clear, viscous fluid that helps lubricate the urethra during sexual arousal, facilitating the passage of sperm.
Corpora Cavernosa: The corpora cavernosa are a pair of spongy, erectile tissues that run along the length of the penis. They are responsible for the penis's ability to become erect and engorged with blood during sexual arousal.
Corpus Spongiosum: The corpus spongiosum is a spongy tissue structure that runs along the underside of the penis. It is one of the three cylindrical bodies that make up the penile anatomy and is responsible for helping to maintain the shape and rigidity of the penis during an erection.
Cowper's Glands: Cowper's glands, also known as the bulbourethral glands, are a pair of small exocrine glands located below the prostate gland in the male reproductive system. They secrete a clear, viscous fluid that lubricates and cleanses the urethra prior to and during ejaculation, helping to neutralize any acidity and facilitate the passage of sperm.
Ejaculatory Ducts: The ejaculatory ducts are a pair of short tubes that connect the vas deferens to the urethra. They serve as the final pathway for the transport of seminal fluid during ejaculation, allowing the sperm and other components of semen to be expelled from the body during sexual activity.
Epididymis: The epididymis is a tightly coiled tube located at the back of the testicle that stores and transports sperm. It is a crucial component of the male reproductive system, serving as a storage and maturation site for sperm before they are released during ejaculation.
Erectile Dysfunction: Erectile dysfunction (ED) is the inability to achieve or maintain an erection sufficient for satisfactory sexual performance. It is a common condition that can have physical, psychological, and social implications for men. This term is particularly relevant in the context of topics related to the male reproductive system, phosphodiesterase 5 inhibitors, and the use of androgens, antiandrogens, and anabolic steroids.
Follicle-Stimulating Hormone: Follicle-stimulating hormone (FSH) is a glycoprotein hormone produced by the anterior pituitary gland that plays a crucial role in the regulation of the female and male reproductive systems. It is essential for the development and maturation of egg follicles in women and the production of sperm in men.
Glans Penis: The glans penis is the sensitive, rounded tip of the penis. It is the distal portion of the corpus spongiosum, the spongy erectile tissue that forms the bulk of the penis's body.
Gonadotropin-releasing hormone: Gonadotropin-releasing hormone (GnRH) is a hormone produced by the hypothalamus in the brain that regulates the production and release of the gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), from the anterior pituitary gland. This hormone plays a crucial role in the functioning of the male and female reproductive systems.
Gonadotropin-releasing hormone (GnRH): Gonadotropin-releasing hormone (GnRH) is a peptide hormone responsible for the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary gland. It plays a critical role in regulating reproductive function.
Leydig Cells: Leydig cells, also known as interstitial cells, are specialized endocrine cells found in the testes that are responsible for the production and secretion of the male sex hormone, testosterone. These cells play a crucial role in the male reproductive system and are also involved in the process of feminizing hormonal therapy.
Libido: Libido refers to an individual's sexual drive or desire. It is a fundamental aspect of the male reproductive system, influencing sexual behavior, arousal, and overall sexual health and function.
Luteinizing Hormone: Luteinizing hormone (LH) is a glycoprotein hormone produced and released by the anterior pituitary gland. It plays a crucial role in the regulation of reproductive processes in both males and females.
Male reproductive system: The male reproductive system consists of organs involved in the production and delivery of sperm and the secretion of male sex hormones. Key structures include the testes, vas deferens, prostate gland, and penis.
Penis: The penis is the male reproductive organ responsible for urination and sexual intercourse. It is a cylindrical structure composed of spongy tissue that becomes engorged with blood during sexual arousal, causing it to become erect and increase in size and rigidity.
Premature Ejaculation: Premature ejaculation is a common sexual dysfunction characterized by the inability to delay ejaculation, leading to unsatisfactory sexual experiences. It is a condition that affects the male reproductive system and can have significant impacts on an individual's sexual health and relationships.
The term 'premature ejaculation' refers to the occurrence of ejaculation before or shortly after the start of sexual activity, often before the individual or their partner is ready. This can lead to feelings of frustration, inadequacy, and distress, and can negatively impact the quality of sexual intimacy.
Prostate Gland: The prostate gland is a small, walnut-sized exocrine gland located at the base of the bladder in males. It is an essential part of the male reproductive system, responsible for producing a key component of seminal fluid that nourishes and transports sperm.
Prostatitis: Prostatitis is a condition characterized by inflammation of the prostate gland, a walnut-sized organ located just below the bladder in men. It can cause a variety of urinary and sexual symptoms, and is an important consideration in the review of the male reproductive system.
Scrotum: The scrotum is a pouch of skin that hangs below the penis and contains the testicles. It is an essential part of the male reproductive system, responsible for protecting and regulating the temperature of the testes.
Semen: Semen is the fluid that is released from the male reproductive organs during ejaculation. It is a complex mixture of various substances that serves as the vehicle for transporting and nourishing sperm cells, which are essential for male fertility and reproduction.
Seminal Vesicles: The seminal vesicles are a pair of glandular pouches located behind the bladder in the male reproductive system. They produce a viscous, alkaline fluid that makes up a significant portion of the semen, which helps to nourish and transport sperm during ejaculation.
Seminiferous Tubules: The seminiferous tubules are the functional units of the testes, responsible for the production and maturation of sperm cells. These highly coiled tubular structures are the site where spermatogenesis, the process of sperm cell development, takes place.
Spermatogenesis: Spermatogenesis is the process by which male germ cells, known as spermatogonia, undergo a series of mitotic and meiotic divisions to produce mature, motile sperm cells. This process is essential for male fertility and is closely regulated by hormones from the hypothalamus, pituitary, and testes.
Spermatozoa: Spermatozoa, also known as sperm cells, are the male reproductive cells responsible for fertilizing the female egg during sexual reproduction. They are produced in the testes and play a crucial role in the male reproductive system.
Testes: The testes are the male reproductive glands responsible for producing sperm and the male sex hormone, testosterone. They are a crucial component of the male reproductive system and also play a role in feminizing hormonal therapy.
Testicular Cancer: Testicular cancer is a type of cancer that originates in the testicles, the male reproductive glands responsible for producing testosterone and sperm. It is one of the most common cancers among young men, typically occurring between the ages of 15 and 35, and is highly treatable if detected early.
Testicular reproductive system: The testicular reproductive system encompasses the structures and functions of the testes, which are responsible for producing sperm and testosterone. It is a crucial aspect of male fertility and hormonal balance.
Urethra: The urethra is a tube that carries urine from the bladder out of the body. It is an essential part of both the urinary and reproductive systems, playing a crucial role in eliminating waste and facilitating sexual function.
Vas Deferens: The vas deferens, also known as the ductus deferens, is a muscular tube that transports sperm from the epididymis to the ejaculatory duct, which then carries the sperm to the urethra for ejaculation. It is a crucial component of the male reproductive system.