male reproductive

• Male genital organs


  Internal and external genital/reproductive organs
• Internal reproductive organs


  • Paired testes
  • Excurrent duct system (ductuli efferentes, epididymides, deferent ducts, ejaculatory ducts, male urethra)
  • Accessory reproductive glands
• External reproductive organs


  • Penis
  • Scrotum
  • Prepuce
• Testis


  • Enclosed by tunica albuginea (tough fibrous covering)
  • Tunica albuginea sends in septa that divide the testicular parenchyma into lobules
  • In some species, septa meet centrally to form a longitudinal mediastinum testis

  
• Testicular parenchyma


  Made up of elaborately coiled seminiferous tubules with interstitial tissue in between

  
• Seminiferous tubules


  • C shaped, extremely tortuous tubules that open into straight tubules (tubuli recti) which drain into rete testis
  • Lined by seminiferous epithelium with germ cells and Sertoli cells

  
• Spermatogenesis


  1. Spermatocytogenesis (development of germ cells from spermatogonia to primary spermatocytes)

  2. Meiosis (primary spermatocytes undergo meiotic division)

  3. Spermiogenesis (remodeling of round spermatids to produce functional flagellated spermatozoa)

  
• Spermatocytogenesis


  • Spermatogonia type A (stem cells) undergo mitotic divisions to produce spermatogonia type B which enter meiosis

  
• Meiosis


  • Primary spermatocytes undergo prophase I, metaphase I, anaphase I, telophase I to produce secondary spermatocytes which then undergo 2nd meiotic division to form round spermatids

  
• Spermiogenesis


  • Golgi phase (acrosomal vesicle formation)
  • Cap phase (acrosomal cap formation)
  • Acrosomal phase (nuclear transformation, tail development)
  • Maturation phase (spermatozoon release from Sertoli cells)

  
• Sertoli cells


  • Somatic cells that envelope and nurture germ cells
  • Divide seminiferous epithelium into basal and adluminal compartments
  • Form blood-testis barrier with peritubular myoid cells

  
• Spermatozoon


  Made up of head (nucleus and acrosome) and tail/flagellum

  
• Sperm head


  • Nucleus with condensed chromosomes stabilized by protamines
  • Acrosome (cap over anterior part of nucleus with hydrolytic enzymes)

  
• Sperm tail


  • Connecting piece, midpiece, principal piece, end piece
  • Axoneme (central pair of microtubules surrounded by 9 peripheral pairs)
  • Outer dense fibres, mitochondrial sheath/fibrous sheath

  
• Interstitial tissue


  Tissue between seminiferous tubules containing blood vessels, lymphatic vessels, nerves, and Leydig cells (secrete androgens)
• Excurrent ducts


  • Tubuli recti
  • Rete testis
  • Ductuli efferentes
  • Ductus epididymis
  • Ductus deferens
  • Ejaculatory ducts
  • Male urethra
• Tubuli recti


  • Straight terminal ends of seminiferous tubules opening into rete testis, lined by Sertoli cells only

  
• Rete testis


  • Anastomosing channels in mediastinum testis where seminiferous tubules open, lined by columnar or squamous epithelium

  
• Ductuli efferentes


  • Vary in number (13-23), have ciliated simple columnar epithelium, confluence into ductus epididymis
• Leydig cells


  • Polyhedral cells with large spherical nuclei
  • Cytoplasm has abundant agranular endoplasmic reticulum associated with steroid synthesis
• Excurrent ducts


  • Tubuli recti
  • Rete testis
  • Ductuli efferentes
  • Ductus epididymis
  • Ductus deferens
  • Ejaculatory ducts
  • Male urethra
• Tubuli recti


  • Straight terminal ends of seminiferous tubules opening into the rete testis
  • Lined by Sertoli cells only

  
• Rete testis


  • Anastomosing channels found in the mediastinum testis
  • Epithelium is columnar or squamous

  
• Ductuli efferentes


  • Vary in number (13-23)
  • Have a ciliated simple columnar epithelium
  • Confluence into a single epididymal duct
• Ductus epididymis


  • Divided into caput, corpus and cauda
  • Lined by pseudostratified columnar epithelium with stereocilia
  • Has principal cells and basal cells
  • Principal cells involved in secretion and absorption of epididymal fluid
  • Cauda has smooth muscle layer that increases in thickness distally
  • Larger lumen in cauda compared to corpus and caput
  • Provides conditions for maturation of spermatozoa

  
• Ductus (Vas) deferens


  • Continuation of epididymal duct
  • Thick muscular coat made of circular, longitudinal and oblique muscles
  • Pseudostratified columnar epithelium
  • Joined by ducts of vesicular glands to form ejaculatory duct
• Ampulla of vas deferens


  • Terminal dilation of vas deferens
  • Very prominent in stallion and man, thin in ruminants and dog, absent in cat and pig
  • Glandular with branched tubulo-alveolar glands
• Urethra


  • Serves both urinary and reproductive system
  • Has pelvic part and penile part
  • Pelvic urethra has transitional epithelium, stratum cavernosum, glands of disseminate prostate, smooth and striated muscle
  • Penile urethra has mixed transitional, stratified columnar or simple columnar epithelium, surrounded by corpus spongiosum and tunica albuginea
• Accessory sex glands


  • Vesicular gland
  • Prostate gland
  • Bulbourethral gland
• Accessory sex glands


  • Increase volume of semen
  • Nourish and protect spermatozoa
  • Buffer acidic vaginal environment
• Vesicular glands


  • Elongated smooth walled or saccular organs
  • Very large in boar and horse, moderate in ruminants, lacking in carnivores
  • Tubuloalveolar glands
• Prostate gland


  • Has a disseminate part and a body
  • Body well developed in carnivores and stallion
  • Capsule of dense connective tissue sending trabeculae dividing gland into lobules
  • Compound tubuloalveolar gland
  • Disseminate part well developed in boar and ruminants
  • In submucosa of pelvic urethra
• Bulbourethral glands


  • Compound tubular gland in boar, tomcat, billy goat
  • Compound tubuloalveolar gland in stallion, bull, ram
  • Absent in dog
  • Mucous secreting columnar or pyramidal cells with basal nuclei
• Penis


  • Attached radix or root, corpus or body, glans penis
  • Two types: musculocavernous and fibroelastic
  • Musculocavernous has two corpora cavernosa ensheathed by tunica albuginea
  • Fibroelastic has more connective tissue and elastic fibres, less smooth muscle
  • Carnivore penis is intermediate
• Prepuce


  • Tube-like reflection of skin covering distal free part of penis
  • Has external, parietal and visceral layers
  • External layer has skin structure
  • Parietal and visceral layers have stratified squamous epithelium
  • Stallion has sebaceous and tubular preputial glands

  
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