Male Reproductive system

• Testes

  Site of spermatozoa development and steroidogenesis
• Genital excurrent ducts

  Ducts through which spermatozoa continue to develop and other secretions are added. Include efferent ductules, duct of epididymis & ductus (vas) deferens.
• Components of the male reproductive system

  • Testes
  • Genital excurrent ducts
  • Accessory sex glands
  • Penis
• General histological pattern

  • The male reproductive system is composed of a series of interconnected 'tubes'/ducts lined by epithelium and supporting tissues
  • Variation of the histological structure is linked to the function of the region
• Testes structure

  • Mediastinum: BV, lymphatic vessels and excurrent ducts enter/leave through mediastinum
  • Divided into lobules by CT septa that are continuous with outer connective tissue covering (tunica albuginea)
  • Within each lobule, there are 2 functional regions: Seminiferous tubules & Interstitial tissue
• Testes: Interstitial tissue

  • Found outside of seminiferous tubules and tunica propria
  • Characterised by Leydig cells/interstitial cells that synthesise and secrete sex hormones (steroidogenesis)
  • Stimulated by LH
• Testes: Seminiferous tubules

  • Epithelium: Complex stratified epithelium with Sertoli cells and spermatogenic cells
  • Supporting tissue: Tunica propria (peritubular multi-layer connective tissue) surrounding seminiferous tubules that contain myoid cells.
  • Rhythmic contractions of myoid cells help move spermatozoa and testicular fluid through the seminiferous tubules)
• Seminiferous epithelium - Sertoli cells

  Columnar cells with apical and lateral processes that surround spermatogenic cells and perform various functions to support spermatogenesis

  >They extend throughout the thickness of the seminiferous epithelium
• Spermatogenesis phases

  1. Spermatogonial phase: spermatogonia divide by mitosis

  2. Spermatocyte phase: – primary spermatocytes undergo meiotic divisions to produce haploid spermatids

  3. Spermatid phase (spermiogenesis): spermatids differentiate into mature spermatozoa
• Mature sperm

  >Head: flattened, contains acrosomal enzymes

  >Tail: subdivided into the neck, middle piece, principal piece & end piece
• Functions of testes include

  • Spermatogenesis: production of male gametes
  • Steroidogenesis: synthesis of androgens/sex hormones
• Sertoli cells and Leydig cells

  Sertoli cells perform functions to support spermatogenesis, Leydig cells synthesise and secrete sex hormones
• Gonadotropins

  • FSH acts on Sertoli cells to stimulate spermatogenesis
  • LH acts on Leydig cells to stimulate steroidogenesis
• Tubuli rectiAKA tubuli recti

  Short terminal section of seminiferous tubule, initially lined by Sertoli cells then changes to simple cuboidal epithelium
• Rete testis

  Series of interconnecting channels within highly vascular CT of mediastinum, lined by simple cuboidal/low columnar epithelium with cilia and microvilli
• Duct system

  Developing spermatozoa moves from seminiferous tubules to:

  • Intra-testicular ducts: tubuli recti to rete testis
  • Excurrent ducts: efferent ductules to epididymis to vas deferens
• Efferent ductules

  Connect rete testis with the duct of the epididymis,

  >Lined with pseudostratified columnar epithelium with ciliated cells and cells with microvilli

  >Occasional basal cells act as epithelial stem cells

  >Function in transport of spermatozoa and reabsorption of fluid secreted in seminiferous tubule.

  >Smooth muscle layer starts to appear at this point
• The epididymis is important for the maturation and storage of spermatozoa before ejaculation, where spermatozoa acquire motility and fertility
• Duct of epididymis

  • Lined with pseudostratified columnar epithelium with principal cells that contain stereocilia and basal cells: epithelial stem cells
  • Function: absorption (reabsorb testicular fluid) and secretion by principal cells aid in maturation of spermatozoa
  • Smooth muscle layer gradually thickens throughout length of epididymis
• Ductus deferens

  • Pseudostratified columnar epithelium with stereocilia
  • Thick muscular layer arranged in 3 layers
  • Star-shaped lumen
• Seminal vesicles

  • Paired highly folded tubular glands found on posterior wall of the urinary bladder
  • Pseudostratified columnar epithelium contains tall, non-ciliated columnar cells (secreting cells) and short, round cells (stem cells)
  • Smooth muscle
• Function of seminal vesicles

  Fluid from seminal vesicles typically makes up about 70% of the ejaculate and its components including fructose, which is the principal metabolic substrate for sperm
• Prostate Gland

  • Consists of 30 to 50 tubuloalveolar glands
  • Glandular epithelium is variable - it is generally simple columnar, but there may be patches that are simple cuboidal, squamous, or occasionally pseudostratified
  • Supporting tissues: glands are embedded in a dense fibromuscular stroma in which smooth muscle contracts at ejaculation
• Function of prostate

  Secrete alkaline prostatic fluid which contains several enzymes and constitutes roughly 30% of the volume of the semen
• Prostatic concretions (corpora amylacea)

  • Calcified glycoprotein and coagulated prostatic secretion in lumen of peripherally situated glandular acini
  • Increase in number with age and present in ejaculate
• Bulbourethral/Cowper's glands

  • Pea-sized structures found in the urogenital diaphragm and empty into the proximal part of the penile urethra
  • Each gland has several lobules with tubuloalveolar secretory units surrounded by smooth muscle cells and lined by a mucus-secreting simple columnar epithelium
  • Secrete a clear mucus-like secretion that coats and lubricates the urethra
• Semen

  Sperm from testes and secretory products from the epididymis, ductus deferens, and accessory sex glands (prostate, seminal vesicles and bulbourethral glands)
• Penis

  • Consists of erectile tissue bound by dense fibroelastic CT (tunica albuginea):
  • 2 dorsal masses of erectile tissue known as corpora cavernosa, central arteries in the corpora cavernosa branch to form small coiling helicine arteries, which lead to the cavernous spaces
  • 1 ventral mass known as corpus spongiosum (contains penile urethra), venous cavernous spaces are lined with endothelium, separated by trabeculae with smooth muscle and connective tissue
• Penile urethra

  Most of the penile urethra is lined with pseudostratified columnar epithelium, in the glans it becomes stratified squamous epithelium continuous with that of the thin epidermis covering the glans surface
• Pathway of spermatozoa

  Seminiferous tubule → tubuli recti → rete testes → efferent ductules → duct of epididymis → ductus (vas) deferens → ejaculatory duct → prostatic urethra → membranous urethra → penile urethra
• Accessory sex glands

  Add secretions to ejaculate. Include seminal vesicles, prostate gland & bulbourethral glands
• Seminiferous epithelium - Sertoli cell functions

  • Secrete fluid to facilitate the passage of sperm
  • “Nurse cells”- exchange of metabolic substances and waste between developing spermatogenic cells and circulatory system
  • Continuous tight junctions between cells form blood-testis barrier and divide the lumen into basal and luminal compartments
  • Its activity is stimulated by FSH and testosterone – to promote spermatogenesis
• Seminiferous epithelium - Spermatogenic cells

  They regularly replicate and differentiate into mature spermatozoa

  • The most mature (spermatids) are attached to the apical portion of the Sertoli cell (luminal compartment)
  • Most immature (spermatogonia) rest on basal lamina (in the basal compartment)
• Spermatogenesis

  Process by which spermatogonia develop into mature sperm

  • Starts shortly before puberty, under influence of rising levels of pituitary gonadotropins and continues throughout life
• Ejaculatory duct

  Ampulla of ductus deferens + excretory duct of seminal vesicles
• Vascular spaces in penis increase in size and rigidity by filling with blood (mainly from the helicine arteries which dilate during erection to increase the blood flow to the penis)