Phys: Male Repro

Testes

Primary male reproductive organs located outside the pelvic cavity that produce mature sperm within seminiferous tubules and synthesize sex hormones, primarily testosterone, within Leydig cells.

tunica vaginalis

outer covering of testes

tunica albuginea

inner covering of testes

Seminiferous Tubules

Coiled tubular structures within the testes where spermatogonia undergo growth, division, and maturation supported by Sertoli cells.

Leydig Cells

Interstitial cells of the testes stimulated by LH to synthesize and secrete testosterone from cholesterol, exerting local paracrine effects on Sertoli cells and systemic endocrine effects.

Sertoli Cells

Testicular nurse cells stimulated by FSH that nurture developing spermatogonia, secrete androgen-binding protein and inhibin, and convert testosterone to estrogen.

Epididymis

Comma-shaped structure curving over the posterior portion of each testis where ejaculated sperm undergo maturation.

Vas Deferens

Duct with muscular layers capable of powerful peristalsis that stores sperm and transports it through the spermatic cord toward the urethra.

Spermatic Cord

Anatomical structure entering the pelvic cavity through which the vas deferens passes to transport sperm.

Scrotum

Skin-covered fibromuscular sac with rugae that encloses the testes outside the pelvic cavity to maintain a temperature 1°C to 2°C cooler than body temperature for optimal sperm production.

Tunica Dartos

Scrotal muscle layer forming the septum between the testes that tightens or relaxes the scrotum based upon ambient temperature.

Penis

External male organ that delivers sperm to the female vagina and eliminates urine.

Glans Penis

Distal structural component of the penis containing the external opening of the urethra.

Prepuce

Foreskin covering the glans penis.

Corpora Cavernosa

Paired erectile tissue columns in the penis that fill with blood during parasympathetically mediated vasodilation to produce an erection.

Corpus Spongiosum

Single erectile tissue column surrounding the urethra that engorges with blood during erection to maintain urethral lumen patency.

Urethra

Duct passing through the corpus spongiosum of the penis that eliminates urine and conducts semen during ejaculation.

Seminal Vesicles

Paired glands lying behind the urinary bladder that provide fructose as an energy source for sperm and secrete prostaglandins to promote smooth muscle contraction and sperm transport.

Prostate Gland

Male accessory gland with three zones that surrounds the urethra and produces prostatic fluid

prostatic fluid

thin, milk substance that has an alkaline pH for sperm survival in the acidic female reproductive tract as wells as clotting enzymes and fibrinolysin to help mobilize sperm post ejaculation

Bulbourethral Glands

Accessory male glands that release lubricating secretions into the urethral canal during sexual arousal.

Ejaculatory Ducts

Ducts formed by the union of the vas deferens ampulla and seminal vesicle ducts that contract rhythmically during emission and ejaculation.

Mesonephric Ducts (Wolffian Ducts)

Paired embryonic ducts present in early homologous embryos that differentiate into internal male genitalia under hormonal influence.

Paramesonephric Ducts (Müllerian Ducts)

Paired embryonic ducts present in early homologous embryos that degenerate in male embryos.

Genital Tubercle

Homologous embryonic structure present during the first 7 to 8 weeks of gestation that differentiates into male external genitalia under testosterone stimulation.

SRY Gene & Testis-Determining Factor

Region on the Y chromosome encoding this protein that directs male gonadal differentiation in utero

Gonadotropin-Releasing Hormone (GnRH)

Hypothalamic hormone suppressed until puberty that stimulates the anterior pituitary gland to secrete FSH and LH.

Extrahypothalamic factors

factors that cause the hypothalamus to secrete GnRH

Luteinizing Hormone (LH)

Anterior pituitary gonadotropin that acts on Leydig cells to increase cholesterol activity, driving testosterone synthesis.

Follicle-Stimulating Hormone (FSH)

Anterior pituitary gonadotropin that acts on Sertoli cells to stimulate spermatogenesis, androgen-binding protein secretion, and inhibin release.

Testosterone

Primary male sex hormone secreted by Leydig cells responsible for internal genital differentiation, pubertal growth spurts, muscle mass, vocal deepening, epiphyseal plate closure via conversion to estrogen, elevated hematocrit, and libido; has a positive feedback loop for increased sex hormone production during growth to form the testes, scrotum, and penis

Estradiol

hormone released for breast development, maturation of vagina/uterus/ovaries, and fat deposition in hips

Estrogen and GH

hormone released for rapid skeletal growth in boys and girls

Dihydrotestosterone

Potent androgen synthesized peripherally from testosterone that is specifically required for external virilization and prostate development.

Androgen-Binding Protein

Glycoprotein secreted by Sertoli cells into the seminiferous tubule lumen that binds local testosterone to maintain high androgen concentrations for spermatogenesis.

Inhibin

Hormone secreted by Sertoli cells that inhibits anterior pituitary FSH secretion, regulates spermatogonia proliferation, and facilitates LH-stimulated androgen production in Leydig cells.

Estrogens

Hormones formed from testosterone within Sertoli cells and peripheral tissues that mediate epiphyseal plate closure and support normal spermatogenesis.

Spermatogenesis

Process of male gamete/mature sperm production in the seminiferous tubules from germ cells requiring testosterone, FSH, LH, estrogens, and Sertoli cell growth factors.

Spermiogenesis

Final maturation phase of spermatogenesis where spermatids differentiate into mature spermatozoa.

spermatogonia

diploid (2 n, 46 chromosomes) germ cells that can do mitosis or become primary spermatocytes

primary spermatocytes

diploid cells that undergo meiosis

secondary spermatocytes

the 2 haploid cells (n, 23 chromosomes) produced from one round of meiosis from primary version

spermatids

produced after final meiosis; need to still go through spermiogenesis and differentiate into spermatozoa/mature sperm

SEVEN UP Pathway

Anatomical sequence of sperm movement during emission and ejaculation

Penile Erection Reflex

Parasympathetically mediated vascular reflex where parasympathetic nerves release nitric oxide to dilate penile arterioles, causing blood engorgement of the erectile tissue.

Emission and Ejaculation

Sympathetically mediated phases of sexual response involving rhythmic smooth muscle contractions of the internal ducts and urethra to propel semen out of the penis.

Detumescence

Sympathetic resolution mechanism returning the penis to a flaccid state via hypogastric nerve release of norepinephrine, increasing intracellular calcium to induce vasoconstriction and smooth muscle contraction.

Delayed Puberty

Condition defined by the absence of secondary sex characteristics in males by 14 years of age, caused primarily by physiological HPG axis delay in 95% of cases or HPG disruption in 5%.

Central Precocious Puberty

GnRH-dependent premature sexual maturation occurring before 9 years of age in males due to early activation of an otherwise normal HPG axis.

Peripheral Precocious Puberty

GnRH-independent premature sexual maturation occurring before 9 years of age in males caused by autonomous sex hormone production outside the HPG axis.

Complete Precocious Puberty

Premature onset and progression of all sex-appropriate pubertal features in males.

Partial Precocious Puberty

Premature development of appropriate secondary sex characteristics alone or in combination.

Mixed Precocious Puberty

Premature sexual development involving feminization of a boy with secondary sex characteristics of the opposite sex.

Primary Male Hypogonadism

Primary testicular failure characterized by an underdeveloped penis and scrotum, gynecomastia, low libido, sparse facial hair, and infertility despite elevated FSH and LH levels.

Gynecomastia

Overdevelopment of male breast tissue resulting from an altered estrogen-to-testosterone ratio, occurring most frequently in adolescents and men over 50 years of age.