Male reproductive system Aleš Hampl Key components & Gross anatomy Paired gonads = testes Genital ducts Intratesticular •Tubuli recti •Rete testis •Ductuli efferentes Extratesticular •Epididymis •Ductus (vas) deferens •Ejaculatory duct •Urethra Associated glands •Seminal vesicles (paired) •Prostate •Bulbourethral glands (paired) External genital organs •Scrotum •Penis Testis - 1 Length: 4 cm Width: 2-3 cm Thickness: 3 cm Tunica vaginalis • serous, originates from peritoneum Tunica albuginea - capsule • dense connective collagenous tissue Mediastinum + Septa • divide testis into lobuli (250-300) Tunica vasculosa • inside of T. albuginea + adjacent to septa Testis - 2 Mediastinum testis Septula testis Testis - 3 Tunica albuginea Septulum testis Interstitial tissue • derived from T. vasculosa • contains dispersed Leydig cells (brown) Seminiferous tubules • 1 to 4 in one lobule • 1 tubule – 30 to 70 cm in length • total number about 1000 • total length about 500 m Testis – 4 – continuation of seminiferous tubuli Testis - 5 Testis – 6 – interstitium – Leydig cells Myofibroblasts Leydig cells Capillaries Interstitium • loose connective tissue • fenestrated capillaries + lymphatics + nerves • mast cells + macrphages + Lyedig cells • round shaped • large centrally located nuclei • eosinophilic cytoplasm • lipid droplets • testosterone synthesis Testis – 7 – interstitium – Leydig cells crystals of Reinke Lipid droplets Mitochondria Testosterone Smooth ER + Testis – 8 – Blood supply – Plexus pampiniformis Spermatic cord Ductus deferens Testis – 9 – Seminiferous / Germinal epithelium capillary Leydig cell Sertoli cell basal lamina Testis – 10 – Sertoli cells adluminal compartment basal compartment Sertoli-to-Sertoli junctional complexes = blood-testis barrier occluding + gap junctions Morphology: • tall, collumnar • highly folded membranes, undistingushable boundaries • hosts 30 to 50 germ cells • abundant SER, minimal RER • numerous mitochondria + well developed Golgi • abundant cytoskeletal elements • occluding + gap junctions Function: • support – physical + nutritional • blood-testis barrier • phagocytosis • secretion of sperm transporting fluid + fructose • endocrine: anti-Mullerian hormone + inhibin + androgen-binding protein Testis – 11 – Sertoli cells – Junctional complexes Sertoli-to-Sertoli Sertoli-to-Spermatid Before puberty Slowly mitotically dividing spermatogonia in genital ridges After puberty ~0.25 mm ~0.5 km Lumen Spermatocytogenesis (mitotic) Meiotic phase Spermiogenesis Spermatogenesis Spermatogenesis A0 Spermatogonia – Stem cells A1 Spermatogonia A2 Spermatogonia A3 Spermatogonia B Spermatogonia • Mitotic divisions • Connected to basal membrane • 2N, 4C Primary Spermatocytes Secondary Spermatocytes - 1N, 2C 1. Meiotic division 2. Meiotic division Spermatides – 1N, 1C Spermiogenesis • No division • Differentiation BASALADLUMINAL Spermatogenesis - Spermatogonia Dark Pale Dark A Dark A Pale A Pale A B Pale A B Spermatocyte Spermatocyte heterochromatin eurochromatin About 12 m Spermatogenesis - Spermatocytes Primary spermatocytes • largest germ cells (16 m) • at various stages of Mei 1 (~24 days) • from basal to adluminal compartment • occlusion junctions with Sertoli cells Secondary spermatocytes • smaller (12 m) • short living (~8 hrs) • infrequently seen Spermatids Spermatogenesis - Spermatocytes Spermatogenesis – Cytoplasmic bridges Spermatogenesis – Spermiogenesis Spermatides • small germ cells (6-8 m) • cytoplasmic bridges Spermatozoamorphogenesis Key elements 1. Formation of acrosome 2. Development of flagellum 3. Chromatin condensation + shaping the nucleus 4. Reduction of cytoplasm Spermatogenesis – Spermiogenesis centrioles acrosomal vesicle (granule on TEM) Golgi • Prominent Golgi complex • Numerous mitochondria • Pair of centrioles • Transgolgi pathway produces granules • Granules form acrosomal vesicle Acrosomal enzymes • hyaluronidase • acrosin • acid phosphatase • neuraminidase acrosomal cup manchette • Acrosomal vesicle flatten - cup • Microtubules arrange into manchette • Chromosemes begin to condense Spermatid nucleus centrioles axoneme SCHEMATIC Spermatogenesis – Spermiogenesis flagellum manchette Spermatogenesis – Spermiogenesis Spermatogenesis – Spermiation = final stage of spermiogenesis Spermatids (syntitium) Residual body Spermatozoa processed by Sertoli cells releasefromthe seminiferousepithelium Spermatozoon neck middle piece principal piece end piece HEAD TAIL 45 m Total length = 65 m annulus mitochondria sheath outer dense fibers (9) cytoplasmic membrane axoneme cytoplasmic membrane axoneme axoneme outer dense fibers (7) column of FS column of FScytoplasmic membrane outer dense fibers fibrous sheath (FS) at „annulus“ Spermatozoon acrosome neck middle piece nucleus Spermatogenesis – Hormonal regulation Dihydro‐ testosterone (DHT) • Male pattern of development (before birth) • Growth of male sex organs and expression of male secondary sex characteristics (starting  at puberty) • Anabolism (protein synthesis) Spermatozoa + Ejaculate Properties of spermatozoa • life-span: 2 to 3 dys in female reproductive tract several weeks in epidydimis • fertilising ability: up to 2 days • velocity: 3-5 mm/min. • 2 types of spermatozoa: with X or Y chromosome Composition of ejaculate Corpuscular: • spermatozoa (40-100 mil./1ml) • desquamated epithelia • residual bodies • prostatic concrements Seminal plasma: • secretions of seminal vesicles, prostate, bulbourethral, and Littré's glands • testicular fluid • secretions of epithelia of excretory ducts Normozoospermia – WHO standard • volume of ejaculate: 2,0 ml and more • pH of ejaculate: 7,2-7,8 • sperm concentration: minimally 20 mil. spermatozoa/1ml, total at least 40 mil./ejaculate • movability: min. 50 % movable with 25 % quickly and progressively moving • morphology: min. 30 % normal spermatozoa • vital spermatozoa: minimally 50 % Spermatozoa + Ejaculate Abnormal spermiogram - Nomeclature • Asthenozoospermia: reduced sperm motility • Oligozoospermia: reduced sperm concentration in ejaculate • Teratozoospermia: large numbers of morphologically abnormal sperm • Oligoastenoteratospermia: combined abnormality in numbers, motility, and morphology of sperm • Azoospermia: complete absence of sperm in ejaculate • Necrozoospermia: high percentage of dead sperm (norm = minimum 50%) • Pyospermia: unusually high numbers of leukocytes in ejaculate (norm = max. 1 million) Genital ducts Intratesticular •Tubuli recti •Rete testis •Ductuli efferentes Extratesticular •Epididymis •Ductus (vas) deferns •Ejaculatory duct •Urethra Male efferent passages = Genital ducts Intartatesticular genital ducts – Tubuli recti • short – about 1 mm • in septula • proximal part: Sertoli cells • distal part: simple cuboidal epithelium Rete testis Tubuli recti Ductuli efferentesDuctus deferens Ductus epididymis Intartatesticular genital ducts – Rete testis • labyrinth – interconnected channels • in mediastinum • simple cuboidal epithelium (as in Tubuli recti) (with microvili + cilium) • circular smooth muscle cells Rete testis Tubuli recti Ductuli efferentesDuctus deferens Ductus epididymis Intartatesticular genital ducts – Ductuli efferentes • 10 to 20 • penetrate tunica albuginea • cuboidal + collumnar cells (patches) • non-ciliated + ciliated – sperm passage • microvili + lysosomes – absoption of luminal fluid • smooth muscle cells – passage of sperm Rete testis Tubuli recti Ductuli efferentesDuctus deferens Ductus epididymis Extratesticular genital ducts – Ductus epididymis 1 • about 5 meters long • highly convoluted (head + body) • tail (cauda) straight – sperm storage + maturation (under hormonal influence) • collumnar pseudostratified lining: basal cells (polyhedral) + principal cells (collumnar) • principal cells with stereocilia • surrounded by circular smooth muscle layer (peristaltic motion) Rete testis Tubuli recti Ductuli efferentesDuctus deferens Ductus epididymis HEAD TAIL BODY Extratesticular genital ducts – Ductus epididymis 2 basal cells principal cells (secretion + absorption) smooth muscle cells Sterocilia (non-motile microvioli – 10-20 m) Rete testis Tubuli recti Ductuli efferentesDuctus deferens Ductus epididymis Extratesticular genital ducts – Ductus deferens 1 • thick walled + folded lumen • epithelia similar to D. epididimis – collumnar pseudostratified (basal cells + principal cells) • surrounded by three layers of smooth muscle layer (circ+long+long) • sympathetic inervation – initiate ejaculation Fibroelastic connective t. Smooth muscle coat Extratesticular genital ducts – Ductus deferens 2 ductus deferens artery vein vein m. cremaster Funiculus spermaticus Extratesticular genital ducts – Ejaculatory duct • short + straight • portion after entry of seminal vesicle duct • surrounded by prostate • enters urethra at the colliculus seminalis (verumontanum) • lined with simple collumnar epithelium • NO smooth muscle laeyer Posterior view Lateral view Accessory genital glands – Seminal vesicles Seminal vesicle • develops from ductus deferens • about 15 cm long snaking tube – tubular gland • highly folded mucosa – labyrinthous cul-de-sac with opennings to lumen • pseudostratified epithelium - basal + principal cells (with microvilli+ flagellum) • fibroelastic submucosa + smooth muscle layer • seminal fluid – constitutes about 70 of ejaculate (rich for fructose) Accessory genital glands – Prostate gland 1 • size and shape of chesnut (the largest accesory gland) • stroma (derives from the capsule): fibroelastic elements, many smooth muscle cells • prostatic secretion: lipids, acid phosphatase, proteolytic enzymes, citric acid, fibrinolysin (liquifies semen) Concentrically organised parenchyma Capsule • collagenous • with smooth muscle cells • vascularised 30 to 50 tubuloalveolar glands Mucosal • closest to the urethra = shortest Submucosal • larger than mucosal Main • largest • most abundant • simple pseudostratified collumnar epithelium • abundant RER + Golgi + secretory granules GLANDS Accessory genital glands – Prostate gland 2 Corpora amylacea = prostate concretions • increase with age • may calcify • size even 1 mm corpora amylacea Accessory genital glands – Prostate gland 3 Accessory genital glands – Bulbourethral glands Lateral view Bulbourethral glands • small – 3 to 5 mm • at the root of the penis • lobular structure (septa) • skeletal muscle fibers (derived from urogenital diaphragm) • simple cuboidal epithelium • lubricating fluid (sialic acid + galactose) Penis - 1 Deep dorsal vein Superficial dorsal vein Dorsal artery Dorsal nerve Skin Urethra Deep artery Corpus cavernosum (2x) Corpus spongiosum Erectile tissue Tunica albuginea Septum (discontinuos) Penis - 2 Vascular spaces Trabeculae Tunica albuginea Corpus cavernosum Corpus cavernosum • lined by endothelia • elastic fibers • smooth muscle cells Capillary plexuses + Helical arteries Deep arteries Genital system Sexual dimorfism – individual can only have one type of genital organs Genetic determination: • Heterogametic (XY) – male • Homogametic (XX) - female Indifferent stage Differentiation into individual sexes 7th weekFertilization = genetic gender established (Barr body) Genital system – 7 weeks at indifferent stage Gonads External genitalia Sertoli cells Leydig cells No MIS No Testosterone Sexual Determination Sexual Differentiation Genital system – Sry gene Sry gene – Sox family TF – on short arm of Y chromosome Default pathway Y chromosome decides XXY – male X0 - female Genital system – Sry gene Pairing of X and Y chromosomes in pseudoautosomal region during meiosis Rare crossing-over causes translocation of SRY to X chromosome: XY females or XX males Genital system – Primordial germ cells PGC - large spherical cells Primordial germ cells (PGC) • first recognizable at day 24 • from epiblast-derived extraembryonic msoderm • few cells among endodermal cells of the yolk sac • they migrate through the dorsal mesentery of the hindgut • migrate towards genital rigdes (plicae genitales) • proliferate during migration • reach (1-2 thousands) genital ridges on week 6 of gestation Males PGC stop dividing Females PGC enter meiosisX decided by somatic cells in the genital ridges Genital system – migration of PGC into gonadal anlagen Genital system – gonadal anlagen Steroidogenic mesoderm along the ventromedial border of the mesonephros caudal region = Genital ridges cranial region = Adrenocortical primordia cells of coelomic epithelium + cells from mesonephric ridge Week 4 – Th6 to S2 cranial + caudal parts involute Week 6 – L3 to L5 become populated by PGC at week 6 Genital system – indifferent gonade (week 6) Genital system – Descent of the testes Gubernaculum – originates from caudal portion of genital ridge „Prerequisites + driving forces“ for the descent of testes: • testes enlargement • atrophy of mesonphros – allows for caudal movement • tension of gubernaculum • atrophy of paramesonephric ducts – move to unquinal canal • enlargement of processus vaginalis peritonei (6th month) • increased intraabdominal pressure ? By 26 weeks • the testes have descended retroperitoneally to the deep inguinal rings During 26th week • final descent through the inguinal canals into the scrotum – 2 to 3 days NOTES More than 97% of full-term newborn males have both testes in the scrotum During the first 3 months after birth, most undescended testes descend into the scrotum Spontaneous testicular descent does not occur after the age of one year Genital system – Descent of the testes Processus vaginalis obliterated NORMAL Remaing cyst = Hydrocele ABNORMAL Remanining connection = Risk of hernia ABNORMAL Genital system – Differentiation of the testes Late 6th week Cord cells differentiate to Sertoli cells (meiosis-inhibiting factor, anti-mullerian substance, androgen binding factor) Tunica albuginea develops (sets barrier between coelomic epithelium and testis cords) Cord cells form seminiferous tubuli, tubuli recti, and rete testis Rete testis joints ductuli efferentes that are derived from mesonephric ducts (5th to 12th) Week 8 to 18 Leydig cells develop and function in developing testis • from coelomic epithelia and mesonphros • produce testosteron • support development of Wolfian (mesonephric) duct • support development of external genitalia Genital system – Sexual duct system – Indifferent stage Paramesonephric duct Develops at days 44 to 48 Cranially opens to coelomic cavity Week 7 Wolffian Mullerian Genital system – Sexual duct system – Male Mesonephric ducts (Wolffian) • Ductus epididymis • Ductus deferens • Ductus ejaculatorius • Seminal vesicle Paramesonephric ducts (Mullerian) regresses in week 8 (anti-M hormone) • Appendix testis (cranial part) • Utriculus prostaticus (caudal part) Mesonephros • Ductuli efferentes • Paradidymis (under the testis, nonfunctional) Genital system – External genitalia - Indifferent stage They are derived from a complex mesodermal tissue located around cloaca. Week 8 Week 6 to 8 Genital tubercle – Phallus Urethral (genital) folds – Plicae urogenitales Genital swellings – Tori genitales Orificium urogenitale primitivum demarcated by: HORMONE-INDEPENDENT Genital system – External genitalia - Dimorphism Week 9 to 13 Weeks 12 + 13 are particularly critical = fusing of urethral folds Genital swellings Genital tubercle Genital (urethral) folds Clitoris Labia minora Labia majora Penis Urethra Scrotum MALE FEMALE Genital system – External genitalia - Male Influenced by dihydrotestosterone Influenced by testosterone Genital system – External genitalia - Male Genital tubercle elongates – penis (phallus) Genital swellings enlarge – scrotum Genital folds form the lateral walls of the urethral groove Genital folds form the spongy urethra Ventral epithelium of genital folds – urethra proper Corpora cavernosa develop from mesenchyme Scrotal raphe Urethral raphe Anus Scrotum Genital plate Fused genital folds + Canalized – urethra formed Genital groove Genital system – External genitalia – Urethral orifice • ectodermal ingrowth forms a cellular ectodermal cord Penis body Ectodermal cord Glans penis Spongy urethra Coronary groove Surface ectoderm Spongy urethra Spongy urethra Developing septum External urethral orifice Distal part of spongy urethra Prepuce Glandular part of urethra • the cord grows towards the root of the penis to meet the spongy urethra • the cord canalizes • circular ingrowth of ectoderm occurs at the periphery of the glans penis (week 12) • circular ingrowth breaks down forming prepuce (for some time adherent to the glans penis, hard to retract at birth) Genital system – External genitalia – Male hypospadia Normal midline raphe Raphe off center Thank you for your attention ! Questions and comments at: ahampl@med.muni.cz