Male Reproductive System Lecture Review

Comprehensive vocabulary flashcards covering the anatomy, physiology, hormonal regulation, and clinical disorders of the male reproductive system based on the lecture transcript.

Reproductive physiology

The study of the functions and processes involved in human reproduction.

HPG axis

The Hypothalamic–Pituitary–Gonadal axis, a hormonal system that regulates spermatogenesis, testosterone production, and sexual development.

GnRH

Gonadotropin-Releasing Hormone; produced by the hypothalamus in pulses to stimulate the release of LH and FSH from the anterior pituitary.

FSH

Follicle-stimulating hormone; an anterior pituitary hormone that stimulates spermatogenesis and Sertoli cells to produce inhibin and androgen-binding protein (ABP).

LH

Luteinizing hormone; an anterior pituitary hormone that stimulates Leydig cells in the testes to secrete testosterone.

Primary Sexual Characteristics

Reproductive organs directly involved in reproduction that are present at birth, such as the penis, testes, scrotum, and prostate gland.

Secondary sexual characteristics

Physical traits that develop during puberty under the influence of testosterone, such as deepening voice, facial hair, and increased muscle mass.

Scrotum

A pouch of skin and muscle that contains the testes and maintains a temperature of $2-3\,^\circ C$ below normal body temperature for proper sperm production.

Dartos muscle

A muscle within the scrotum that wrinkles the scrotal skin to conserve heat.

Cremaster muscle

A muscle that raises or lowers the testes in the scrotum based on temperature and emotional stimuli.

Spermatogenesis

The continuous process of male gamete (sperm) formation occurring in the seminiferous tubules of the testes.

Sertoli cells

Supporting cells in the seminiferous tubules that nourish sperm, form the blood-testis barrier, and produce inhibin and ABP.

Leydig cells

Interstitial cells located between seminiferous tubules that produce the hormone testosterone.

Blood-testis barrier

A specialized barrier formed by tight junctions between Sertoli cells that protects antigenically different sperm cells from the immune system.

Spermatogonia

Undifferentiated diploid germ cells ($46$ chromosomes) located at the basement membrane of seminiferous tubules that undergo mitosis.

Spermiogenesis

The phase of spermatogenesis where round spermatids transform into mature spermatozoa by condensing the nucleus and forming a tail and acrosome.

Acrosome

A cap-like structure on the sperm head containing enzymes that assist the sperm in penetrating the ovum.

Sperm development timeline

The total process takes roughly $10-12$ weeks ($64-74$ days in the testes and $1-2$ weeks in the epididymis).

Epididymis

A long, coiled tube on the posterior surface of the testis where sperm undergo maturation, gain motility, and are stored for $2-6$ weeks.

Vas deferens

A muscular tube that uses peristaltic contractions to transport sperm from the epididymis to the ejaculatory duct.

Ejaculatory ducts

Short ducts formed by the union of the vas deferens and the duct of the seminal vesicle, carrying semen into the urethra.

Corpora cavernosa

Two larger cylinders of erectile tissue on the dorsal side of the penis responsible for the firmness and rigidity of an erection.

Corpus spongiosum

A column of erectile tissue on the ventral side of the penis that surrounds the urethra and ends as the glans penis.

Seminal vesicles

Glands that contribute $60-70\%$ of semen volume, providing an alkaline fluid rich in fructose and prostaglandins.

Prostate gland

A chestnut-shaped gland that secretes a milky alkaline fluid containing enzymes and citrate, contributing $20-30\%$ of semen volume.

Bulbourethral (Cowper’s) glands

Small glands that secrete lubricating mucus to neutralize urethral acidity from urine residues before ejaculation.

Nitric oxide (NO)

A major mediator and signaling molecule that activates guanylate cyclase to produce cGMP, leading to smooth muscle relaxation and penile erection.

Emission

The movement of semen into the urethra, controlled by the sympathetic nervous system ($T11-L2$).

Detumescence

The process where the penis returns to a flaccid state, mediated by sympathetic activity and the breakdown of cGMP via phosphodiesterase-5 (PDE-5).

Hydrocele

A clinical condition characterized by fluid accumulation around the testicle.

Varicocele

Enlarged scrotal veins, often referred to as "varicose veins" of the scrotum.

Oligospermia

A clinical term indicating a low sperm count in the semen.

Azoospermia

A clinical term indicating the total absence of sperm in the semen.

Hypogonadism

A condition characterized by low testosterone production, which can be primary (testicular failure) or secondary (hypothalamic/pituitary problem).

Prostatitis

Inflammation of the prostate gland, often due to infection, which can lead to reduced semen volume and altered pH.