Chapter 01: The Male Reproductive System

Reference

Salustiano, R. (2024). The Male Reproductive System. In Dr. RPS Maternal & Newborn Care: A Comprehensive Review Guide and Source Book for Teaching and Learning (2nd ed., pp. 2-22). C&E Publishing, Inc.

Andrology is the study of the male reproductive system and urological problems. The primary reproductive function serves to produce and transport sperm through and out of the genital tract into the female genital tract. It is composed of the penis, scrotum, testes (testosterone, sperm), ducts (seminiferous tubules, epididymis, spermatic cord), accessory glands (seminal vesicles, prostate glands, Cowper’s glands, urethra).

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The Penis

The penis is an elongated and cylindrical appendage, consisting of a body (shaft) and a cone-shaped end (glans). Within it is the urethra, a passageway for both urine (excretory function) and semen (reproductive function, primary). It lies in front of the scrotum. The penile root lies in the perineum, from where it passes forward below the symphysis pubis, while the lower two-thirds are outside the body in front of the scrotum and covered in skin. It is extremely vascular; blood spaces fill and become distended during sexual excitement, resulting in penile distention and stiffening, termed as an erection. The erectile tissue is composed of three columns, of two types:

1. Corpora Cavernosa (two columns): lateral columns located on either side and in front of the urethra
2. Corpus Spongiosum (one column): posterior column, which contains the urethra. The tip is expanded to form the glans penis. The skin at the end of the penis is folded back on itself above the glans penis to form the prepuce (foreskin), a movable double fold.

The penis is mainly attached and supported by the suspensory ligament, originating from the symphysis pubis and merging with the deep fascia of the penis. The blood supply of the penis is a parallel system of internal and external pudendal arteries and veins. Blood to the cavernous sinuses is provided by two branches of the penile artery (the terminal end of the internal pudendal artery).

The penis is innervated by the pudendal nerve. Sympathetic fibers come from the hypogastric and pelvic plexuses, while parasympathetic fibers come from the third and fourth sacral nerves. Stimulation of the parasympathetic causes contraction of the ischiocavernous muscle, which prevents the return of venous blood from the cavernous sinuses. The blood vessels engorge, and the penis becomes elongated, thickened, and stiff. If stimulation is intense, there is rhythmic contraction of the penile muscles, resulting in the forceful and sudden expulsion of semen, a phenomenon called ejaculation.

• Released with ejaculation is about 2 to 4 mL (or 1.25 to 5 mL) of semen containing about 100 million sperm per mL, of which about 20% to 25% are likely abnormal; sperms move at a speed of 2 to 3 mm per minute. In a single ejaculation, the male deposits approximately 200 to 400 million spermatozoa in the vagina, of which fewer than 200 actually reach the ampulla.
• A successful sperm can fertilize an ovum in 5 to 30 minutes after ejaculation.
• Volume and force of ejaculate varies due to some factors:
  • Age: males tend to ejaculate the largest volume of semen in their thirties; decreases with age.
  • Sexual activity: decreased semen volume with recent sexual activity/masturbation reduces the distance semen can travel; increased semen volume than usual with prolonged periods of abstinence.
  • Genetic factors: some people naturally ejaculate more or less compared to others, regardless of health or lifestyle.
  • Lifestyle factors: diet, smoking, and other lifestyle factors can affect semen quality and overall health; regular exercise may improve fertility, sperm quality, and semen volume.
  • Overall health: injury, chronic illness, or surgery causing nerve damage may affect semen volume and quality.
  • Certain drugs: there are certain drugs that interfere with the production of sperm (anabolic drugs, testosterone, chemotherapy medication, opioids), antibiotic ketoconazole, and long-term use of antidepressant selective serotonin reuptake inhibitors (SSRIs).

Special Concerns

1. Impotence/Erectile Dysfunction: the inability of the male to perform sexual intercourse due to absence or lack of ability to initiate and/or maintain erection. May be primary (though rare), or secondary (organic causes, e.g. diabetes, atherosclerosis, alcohol, drugs, psychogenic, injury).
   • Treatment: Viagra, Penile Prosthesis
2. Ejaculatory Incompetence/Ejaculation Disorders
   • Premature Ejaculation: ejaculation occurring before or very soon after penetration (the most common form of sexual dysfunction in men), or its counterpart, Inhibited or Retarded Ejaculation: when duration of stimulation required to reach climax is prolonged or climax cannot be reached.
     • Causes: often due to performance anxiety; lack of attraction for a partner; past trauma; drugs (antidepressants); psychological factors (strict religious background); and nerve damage to the spinal cord and back.
   • Retrograde Ejaculation: occurs when, at orgasm, the ejaculate is forced back into the bladder rather than the urethra and out the end of the penis.
     • Causes: problems with the nerves in the bladder and the bladder neck that permits ejaculate to flow into the bladder; diabetes/diabetic nephropathy; drugs/medications that treat mood disorders.
     • Treatment: generally does not require treatment unless fertility becomes impaired.
   • Inability to Ejaculate Intravaginally: potentially an emotional defense mechanism after the discovery of spousal infidelity or a subconscious refusal to become a father.
3. Refractory Period: the length of time/phase post-orgasm during which sexual response is diminished, and is unable to achieve another erection, orgasm, or ejaculation. This the hormones oxytocin, serotonin, prolactin, and dopamine.
   • This period inhibits feelings of pleasure, or potentially even causes pain. Males may be unable to get an erection, orgasm, or ejaculate, even with sexual stimulation. This is a normal phenomenon and is not synonymous with incompetence.
   • The duration of this period can last for minutes to days, depending on age (shorter in younger men, longer in older man) and overall health. Other factors that affect its duration include mental health, medical conditions, sexual dysfunction, quality and frequency of sex, and routine exercise and engaging in sexual fantasy may indirectly influence the refractory rate by improving one’s sexual fitness, self-image, and sex-drive (Myhre & Sifris, 2023)

Phases of Sexual Response

(mn. APOR, EPOR)

1. Arousal/Excitement: the sexual stimulation by physical or mental stimuli such as touch, kissing, fantasizing, or viewing erotic images.
2. Plateau: the period of increasing sexual excitement during which the penis, vagina, and clitoris will engorge with blood and become highly sensitive.
3. Orgasm: the spontaneous release of sexual energy accompanied by rapid contractions of the lower pelvic muscles, including ejaculation.
4. Resolution: the gradual return to the normal level of functioning and swollen or erect body parts return to their normal sizes. This phase also includes refractory period.

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The Scrotum

The sac-like or pouch-like structure from the root of the penis, suspended from the perineal region. It contains the testes and epididymis, and primarily serves to maintain a lower temperature than the body (by ~1°C) to protect the testes and sperm, and promote spermatogenesis.

• The scrotum is formed of pigmented skin. It has two compartments, one for each testis. Dartos muscles in the scrotum contract to shorten or lengthen the distance of the testes from the body; related to the degree of wrinkling. Temperature affects the degree of wrinkling, e.g. the least wrinkling is found in older men at warmer temperatures, greatest wrinkling is found in young men at cold temperatures. Wrinkling in newborns depends on age. The scrotum is smooth in preterm babies, and wrinkled in full-term newborns.
• Nursing Implication: when educating for testicular self-examination (TSE), the best timing for checking is after a warm bath or shower when the scrotum is soft and less wrinkled, allowing for better palpation of the testes.
• Nursing Implication: in newborns, perform assessment of successful descent of the testes (palpation of the scrotum) from the abdominal cavity. Failure to do so will result in failure for spermatogenesis to occur.

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Testes

Two small (4.5 cm to 6 cm long, 2.5 cm wide, 3 cm thick), oval male gonads are suspended in the scrotum, weighing 10 to 15 grams. They secrete male sex hormones (androgens) and are the site of spermatozoa production in the mature male. They have endocrine and exocrine functions:

1. Endocrine Function: the process of spermatogenesis and the other functions of the testes are under neural and hormonal control. Several structures contribute. Hormonal balance must be maintained in order to maintain proper development of sperm, and infertility can result from a hormonal imbalance.
   • The Hypothalamus stimulate or inhibit APG secretions.
   • The APG secretes the gonadotropins FSH (stimulates Sertoli cells) and LH (stimulates Leydig cells).
   • The Testes are the site of testosterone production, through special Leydig cells that synthesize testosterone from cholesterol. These also locally support sperm production.
2. Exocrine Function: spermatogenesis begins during puberty, where the germinal epithelium in the seminiferous tubules begin producing male gamete (sperm) under the influence of follicle-stimulating hormone and testosterone. This process continues throughout adult life.

The testes are covered into three testicular layers. They are covered by tunica vaginalis, under which is the tunica albuginea, a tough, fibrous, white capsule that covers each testis. It sends inward projections that divide the testis into 250 to 400 lobules, which each contain one to three convoluted seminiferous tubules containing sperm cells in various stages of development. An additional inner layer of connective tissue which contains a fine network of capillaries is the tunica vasculosa, the innermost of the testicular covering layers.

Sertoli cells are special cells that provide structural and metabolic support to the developing sperm cells, being in close contact with the spermatogenic cells at all stages of differentiation. They extend from the basement membrane to the lumen of the seminiferous tubule.

• Maintains the environment necessary for development and maturation.
• Secretes substances initiating meiosis.
• Secretes supporting testicular fluid.
• Secretes androgen-binding protein, which keeps testosterone close to the developing gametes.
• Secretes hormones effecting pituitary gland control of spermatogenesis, particularly the hormone inhibin.
• Phagocytose residual cytoplasm left over from spermiogenesis.

Sperm Production

The primary spermatogonia, the primitive germ cell, are present at birth with diploid 44XY cells. After puberty, spermatogenesis is continuous and is completed in 72 hours. There are various stages:

1. Spermato-Cytogenesis: the diploid spermatogonium produces primary spermatocytes (44XY), which undergo meiosis into two secondary spermatocytes (now a haploid; 22X or 22Y).
2. Spermatidogenesis: second meiotic cell division produces four spermatids.
3. Spermiogenesis: the spermatids grow a tail, develops a mid-piece where mitochondria gather and form an axoneme, and removing residual cytoplasm and organelles to form four spermatozoa/sperms (22X or 22Y). The nucleus becomes compacted in the head of the sperm, and covered with a cap (acrosome).
4. Spermination Process: occurs when mature, non-motile spermatozoa are released from protective Sertoli cells (the “nursing cells of the testes) into the lumen of the seminiferous tubules.

Sperm production creates about 1,000 sperm cells every second, and maturation takes ~9 to 10 weeks for full development and maturation (~70 days in the testes, ~12 to 26 days in the epididymis). Comparatively, a woman’s egg cells are all already present at birth, and are cyclically released.

Sperm Cells

Sperm cells generally live for three to five days if released within the female reproductive tract, but dies within minutes if released into the open. If ejaculation does not occur, sperm remains within the body for ~74 days before dying and being recycled.

Androsperm (22Y)	Gynosperm (22X)
Carries the Y chromosome	Carries the X chromosome
Fast-moving	Slow-moving
Smaller, weaker, short-lived	Bigger, stronger, long-lived
Acid-sensitive	Acid-resistant

Who determines the gender of the child?

The female gamete contains XX sex chromosomes, one of which is used for the child. The other is from the male gamete, which contains XY sex chromosomes. Conception resulting in XY sex chromosomes produce males and XX produces females. From this, as the father has the determining X or Y chromosome, he determines the sex of the offspring.

Sperm anatomy is divided between the head, neck, body, and tail:

1. Head: spheric shape containing a large nucleus, made up of chromosomal material compacted with all the genetic information and 23 chromosomes. Its high compression allows for the sperm to be small, light, and fast. The tip of the head is covered by a cap called an acrosome, which contain hyaluronidase enzyme that can break through the protective covering of an egg cell (zona pellucida) by destroying the hyaluronic acid of the cell during fertilization.
2. Neck: contains the proximal and distal centrioles
3. Body/Middle-piece: an important part containing spirally arrange mitochondria, that provides energy for the sperm.
4. Tail: the flagellum, which aids in motility through the male and female reproductive system.

Testosterone

The primary male hormone. It is responsible for the regulation of sex differentiation, expression of male sex characteristics, spermatogenesis, and fertility.

• Its effects are first seen in the fetus; Gonadal development begins at 5 to 6 weeks (prior to this, reproductive tissue is identical in both genders of the fetus). Around week 7 in utero, the sex-determining region Y (SRY) from the Y chromosome initiates the development of the testicles. Development results in the beginning of the production of testosterone, and begins acting on the body throughout life.
• Secondary sexual characteristics developed by testosterone include: growth (height, muscle, bone), vocal deepening, reproductive system growth, and hair (face, chest, axilla, pubis).
• Spermatogenesis (by the seminiferous tubules) is aided by testosterone, along with FSH.

Pathology may occur as a result of overproduction, underproduction, receptor insensitivity, or impaired metabolism of testosterone (done by the liver).

1. Overproduction of androgens can occur from polycystic ovarian syndrome (PCOS), adrenal virilization/adrenal tumors, ovarian or testicular tumors, Cushing syndrome, or exogenous steroid use.
2. Underproduction of testosterone can occur with aging, medication, chemotherapy, hypothalamus-pituitary axis disorders, primary hypogonadism, cryptorchidism, orchitis (testicular inflammation), and genetic disorders.
3. Impaired metabolism can occur in cases of congenital adrenal hyperplasia (CAH). In 95% of CAH cases, the 21-hydroxylase deficiency result in ambiguous genitalia and later salt wasting, vomiting, hypotension, and acidosis.

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The Duct System of the Testis

1. Seminiferous Tubules: the “seed-carrying” tubules. It is the site of sperm production (spermatogenesis). One to three of these tubules can be found within the lobules (250 to 400) of the testis. Each tubule join to form a system of channels leading to the epididymis.
2. Epididymis: soft, cord-like, and comma-shaped, located on the superior surface of the testis, travelling down the posterior aspect of the lower pole of the testis, leading to the deferent duct (vas deferens).
   • Divided into the head, attached to the top of the testis; tail, which connects to the vas deferens; and storage house, the site for maturation of the sperm to develop their swimming ability
3. Spermatic Cord, which contains the vas deferens, blood vessels, nerves, and lymphatic vessels. The vas deferens joins the duct of seminal vesicles to become ejaculatory ducts; small muscular ducts that carry the spermatozoa and the seminal fluid to the urethra.
   • Nerves connect to the tenth and eleventh thoracic nerves.
   • Lymphatic vessels drain to lymphatic vessels around the aorta.
   • Blood supply comes from a branch of the abdominal aorta, and drains to the inferior vena cava (right testis) and left renal vein (left testis)

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Accessory Glands

1. Seminal Vesicles: paired structures or pouches situated posterior to the bladder. They are 5-cm long and pyramid shaped, and contributes to the ejaculate. This provides nutrition (fructose) for the sperm. It also contains mucus and prostaglandin (causes uterine contraction to aid in sperm motility.
2. Prostate Gland: just below the bladder, surrounding the urethra at the base of the bladder, and lies between the rectum and the symphysis pubis. It is 4-cm long, 3-cm wide, and 2-cm deep. It is composed of columnar epithelium, a muscular layer and enclosed in a form outer fibrous layer/capsule. It connects to the urethra and ejaculatory ducts, and secretes a thin, lubricating milky fluid that enters the urethra through the ducts and helps in the passage and viability of spermatozoa. It contributes alkaline to the sperm, which give it its scent and protects against the acidic environment of the vaginal canal.

Doderlein's bacilli is responsible for acidity of the vaginal canal, as it produces lactic acid from glycogen in the lining of the vagina. This protects the vagina, but is harmful to the sperm.

3. Cowper’s Glands: located on each side of the urethra, just below the prostate gland; it secretes a small amount of lubricating fluid.
4. Urethra: the conduit of semen (sperm with fluids) outside the body through the penis.

flowchart LR
A(Seminiferous Tubules)
B(Epididymis)
C(Vas Deferens)
D(Seminal Vesicles)
E(Prostate)
F(Cowper's Gland)
G(Urethra)
H(Outside)
A-->B-->C-->D-->E-->F-->G-->H

Reproductive Concerns

1. Benign Prostatic Hyperplasia (BPH): an increase in the size of the cells of the prostate. This results in the narrowing of the urethra and thicker bladder walls, weakening the bladder, which eventually results in urinary retention and fullness even after voiding. This is the main problem with BPH.
   • The most common problem of the male* reproductive system, occurring in 50% of men over the age of 50 and in 75% of men over the age of 75.
   • Signs and symptoms: (Early) decreased force, difficulty in starting, frequency, urgency, retention, incontinence, or pain in urinating
   • Diagnosis: personal and family history, physical exam (digital rectal examination), and other medical tests (urinalysis, increased urine alkalinity, cystoscopy, transrectal ultrasound, and importantly the prostate-specific antigen test).
   • Treatment: avoid caffeine and alcohol, fluid intake before sleep or going out, and perform Kegel (to strength the bladder). If moderate or severe, a prostatectomy may be done (or transurethral removal via TURP, laser surgery, TUIP). The operation of choice in very large (>80 grams) prostates is open prostatectomy.
2. Prostatic Cancer: often an adenocarcinoma, with an unknown cause. It may also spread from the prostate to other nearby structures.
   • Diagnosis: no single test is available for prostate cancer, but protein-specific antigen (PSA) tests are among the most commonly used, along with physical examinations, MRI scans, and biopsies. A new test, Prostate Screening EpiSwitch (PSE) is has been found to be 94% accurate and rapid (University of East Anglia, 2023).
   • Prevention: a mediterranean diet has been shown to lower incidence of prostatic cancer. Particular mediterranean micronutrients include Lycopene (tomatoes, melons, papayas, grapes, peaches, watermelons, and cranberries) and Selenium (white meat, fish, shellfish, eggs, and nuts).
3. Male Infertility: diagnosed after inability to conceive after one year of unguarded, appropriately time coitus. Subinfertility is the inability to achieve a pregnancy after one year of unprotected intercourse. Sterility implies an intrinsic inability to achieve pregnancy. An adequate quantity of mature, motile sperm capable of surviving the hostile environment and trip to the egg is required.
   • The most common cause involve low sperm count (<15 million/mL, oligospermia). It may also be due to ejection problems or morphologic or motile abnormalities of the sperm. Normal sperm count is from 15 to 200 million/mL. Other factors include testicular disorders, genital tract obstructions, sperm autoimmunity, hormonal disorders, and ejaculation/sexual dysfunctions. It may also be idiopathic.
   • Diagnosis: history, semen analysis (and subsequent urology, endocrine evaluation, and karyotyping if abnormal/severe).
   • Treatment: lifestyle (diet, sleep, avoid obesity, alcohol, caffeine, smoking, and stress), variocele repair (dilated scrotal veins, most common diagnosis), surgical sperm retrieval, and intrauterine insemination or in-vitro fertilization. If so, a state-mandated infectious disease panel is required.
   • Semen Analysis: a simple non-invasive test for assessing infertility. It detects oligospermia, the most common male factor in infertility.

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Sperm Analysis

A sperm analysis is a simple, non-invasive test for assessing infertility and other potential abnormalities. Preparation requires abstinence for 2 to 3 days (at least 48 hours) prior to specimen collection. Specimen collection, as always, should be done in a clean container. The specimen is kept at body temperature and delivered to the laboratory within 30 to 45 minutes, or up to 60 minutes. Earlier is better.

• The test may be repeated in 2 to 4 weeks due to variance between specimens. Because of the duration of spermatogenesis (2.5 months), 2 to 3 specimens may be obtained over several months. Normal values are as follows: Contesting values were found between p. 15 (Semen Analysis: Preparation/Procedure) and p. 21 (Semen Analysis Results).

Semen Analysis Results	Normal Findings
Volume	2 to 6 mL, with a pH of 7 to 8
Viscosity	liquid within 30 minutes (or 20 minutes)
Sperm Count	more than 20 million/mL
Morphology	more than 50% are mature and normal
Motility	more than 40% (or 50%) are moving
Leucocytes	<1 million/mL

Semen Analysis Results	Reference Range (WHO)
Total sperm count in ejaculate	39 to 928 million
Ejaculate volume	1.5 to 7.6 mL
Sperm concentration	15 to 259 million per mL
Total motility (progressive and non-progressive)	40 to 81%
Progressive motility	32 to 75%
Sperm morphology	4 to 48%

Other considerations for low sperm count if it is seemingly idiopathic:

1. Activities that increase scrotal heat: frequent hot tub or sauna use, long period of sitting, or clothing (tight-fitting)
2. Alcohol and drug use, such as marijuana
3. Frequency of ejaculation
4. Men whose mothers took diethylstilbestrol (DES) while pregnant
5. Trauma/surgery to the testes.