M

• Male Reproductive System


  Function: 1) Produce and transport the semen. 2) Place the semen )by ejaculation in the vagina of the female genital tract). 3) Produce hormones )testosterone by leydig cells &estrogen by Sertoli's cells).

  
• Components of the Male Reproductive System

  • Gonads (Right and left testes)
  • Duct system (Epididymis, Ductus deferens, Urethra)
  • Accessory genital glands (Ampulla, Vesicular glands, Prostate gland, Bulbourethral glands)
  • Single male copulatory organ (penis)

  
• Testis


  It is compound tubular gland that has an exocrine function (cytocrine gland) which produce spermatozoa and an endocrine function which produces testosterone by Leydig & estrogen by Sertoli cells.

  
• Testis


  • Located in scrotum and hanged by spermatic cord that has blood vessels and nerves
  • Surrounded by tunica vaginalis parietalis (that lined scrotum) and tunica vaginalis visceralis covers testis, two serous membrane extend from peritoneum and a space between them contain fluid

  
• Histological components of the Testis

  • Stroma (capsule and septa)
  • Parenchyma (seminiferous tubules and intertubular part)

  
• Stroma


  • Tunica albuginea is a testicular capsule which formed from outer vascular layer (Tunica vasculosa) that contains anatomizing branches of testicular artery and veins
  • Mediastinum testis is a connective tissue area containing the channels of rete testis, large blood and lymph vessels

  
• Compartments of the Parenchyma

  • Intertublar (interstitial tissue) compartment
  • Tubular compartment (Straight part, Intermediate, Convoluted seminiferous tubules)

  
• Intertublar (interstitial tissue) compartment

  Formed of C.T. fibers and cells, Bl. Capillaries, lymph vessels and cells (Myoid cell+ Leydig cells)

  
• Leydig cells


  • Polygonal, oval shape
  • Central spherical nuclei
  • Eosinophilic, containing all organelles; well developed s E/R and abundant mitochondria (steroid-secreting)
  • They secret testosterone hormone that develop the male sex organs, male sex characters and control spermatogenesis
• Myoid cells


  • Squamous cell shape
  • Single flat nucleus
  • Contains contractile microfilaments
  • They are organized in one cell thick sheet (continuous) that surrounds the seminiferous tubules

  
• Tubular compartment


  • Straight part (duct-like) opens on rete testis
  • Intermediate
  • Convoluted seminiferous tubules are lined with a stratified germinal epithelium rest on a basal lamina and surrounded by a lamina propria
• Cells in the Tubular compartment

  • Somatic cells (sustentacular, supporting, or Sertoli's cells)
  • Spermatogenic cells (spermatogonia, primary spermatocytes, secondary spermatocytes and round to elongated spermatids)

  
• Sertoli cells


  • Irregularly outlined, elongated pyramidal or columnar cells
  • Single oval nucleus with a large nucleolus, located near the broad bases of the cell
  • Cytoplasm has mitochondria, abundant sER, microtubules, actin and vimentin filaments, secondary lysosomes, and lipid
  • Functions: Nutritive, protective, and supportive functions for the spermatogenic cells, Phagocytosis, Release the spermatozoa into the lumen of the seminiferous tubules, Produce estrogen, androgen-binding protein and secrete inhibin, Form Blood testis barrier

  
• Blood-testis barrier


  • Formed by the tight junctions between the basal parts of the Sertoli cells, dividing the lumen of the seminiferous tubule into a basal and an adluminal compartment
  • Functions: Allows passage of useful materials, Prevents entrance of damaging substances, Prevents passage of sperms from the seminiferous tubule to the blood stream

  
• Spermatogenesis


  1. Spermatocytogenesis (spermatogonia develop into primary spermatocytes)

  2. Meiosis (primary spermatocytes results in haploid round spermatids)

  3. Spermiogenesis (transformation of round spermatids into elongated spermatozoa)

  
• Spermatogenesis duration: 64 days in man, 50 days in the bull, ram, and stallion and 52 days in rats

  
• Stages of Spermatogenesis


  • Spermatocytogenesis (2N to 4N)
  • Meiosis I (4N to 2N)
  • Meiosis II (2N to N)
  • Spermiogenesis (N to N)

  
• Spermiogenesis


  1. Golgi phase (Acrosomal vesicle formation)

  2. Cap phase (Acrosomal cap formation)

  3. Acrosomal phase (Nucleus elongation, Centriole migration, Axoneme and mitochondrial sheath formation)

  4. Maturation phase (Removal of extra-cytoplasmic fluid)

  
• Spermatozoon


  • Elongated cell with oval or round head and a tail supported with structure necessary for cell motility
  • Head: Elongated condensed nucleus, Acrosomal cap
  • Neck: Short and narrow structure between head and middle piece, Contains centriole that forms axoneme
  • Tail: Middle piece (Axoneme, Mitochondrial sheath), Principal piece (Axoneme, Longitudinal fibers)

  
• Parts of the sperm

  • Head
  • Neck
  • Tail
• Head


  • Elongated condensed nucleus, anterior 2/3 of the nucleus is covered by acrosomal cap (outer and inner acrosomal membrane with several hydrolytic and proteolytic enzymes) necessary for fertilization of the ovum

  
• Neck


  • Relatively short (5 um) and narrow structure between the head and middle piece, consists of a centrally located centriole that form axoneme (two central singlets and nine peripheral doublets microtubules)
• Parts of the tail

  • Middle piece
  • Principal piece
  • End piece
• Middle piece


  • Core is a flagellum-like; axoneme (two central and nine peripheral doublets microtubules), nine peripheral longitudinally oriented coarse fibers surrounded with the mitochondria sheath in a helicoidal arrangement (provide energy for sperm motility) and plasma membrane. A ring-shaped thickening of the plasma membrane (annulus) limits middle piece from principal piece

  
• Principal piece


  • Longest portion of the spermatozoon; axoneme, seven longitudinally oriented coarse fibers, fibrous sheath and plasma membrane

  
• End piece


  • Contains only axoneme with plasma membrane
• Rete testis


  • Irregular anastomosing channel surrounded by vascular connective tissue of the mediastinum, lined by simple cuboidal to columnar epithelium, some have microvilli. Elastic fibers and contractile cells are present beneath the epithelium

  
• Tubuli recti


  • Lining epithelium varies from simple cuboidal (proximal part) to simple columnar (distal part) in bull

  
• Efferent ductules


  • Gathered in small lobules and lined by patches of non ciliated cuboidal cells alternate with ciliated columnar cells

  
• Epididymis


  • Extremely tortuous and coiled, length is 40 m in the bull and boar and 70 m in stallion, consists of head, body and tail. Lining epithelium is a pseudostratified columnar epithelium with stereocilia (non-motile cilia) which help in the movement of sperms. Lamina propria: loose C.T. & circular smooth muscle fibers. Functions: Transfer sperms from testis to ductus deferns, Absorb extra cellular fluid, Nutrition of sperm (glycoprotein), Storage of sperm, Development of progressive motility

  
• Ductus deferens


  • Straight tube with a thick muscular wall, continues towards the prostatic urethra and empties into it. Mucosa with longitudinal folds, covered along most of its extent by pseudostratified columnar epithelium with stereocilia. Lamina propria is rich in elastic fibers. Tunica muscularis consists of inner and outer longitudinal layers separated by a circular layer (produces strong peristaltic contractions that participate in the expulsion of the spermatozoa during ejaculation). T. Adventitia: C.T.
• Accessory glands


  • Ampulla
  • Seminal glands/vesicles
  • Prostate gland
  • Bulbourethral glands
• Ampulla ductus deferens


  • Thickening of the Ductus deferens (simple branched tubulo-alveolar gland), function: Nutrition
• Seminal gland/vesicle in stallion


  • True with wide central lumen, mucosa shows thin, branched folds, epithelium is variable appearing columnar or pseudostratified columnar secretory epithelium, propria sub mucosa: C.T, muscularis consists of IC and OL layers of smooth muscle, adventitia: thin fibroelastic connective tissue layer

  
• Seminal gland/vesicle in bull

  • Compact gland (stroma and Parenchyma), stroma: C.T capsule with several septa, parenchyma: coiled tubular portions of the tubuloalveolar gland are lined with Pseudo stratified columnar epithelium. Function: Secretion is alkaline fluid rich in protein, fructose and vitamin C, important for nutrition and production of energy for sperms

  
• Prostate gland


  • Two portions: Compact or external portion (corpus) surrounds part of the pelvic urethra, Disseminate or internal portion located in the propria-submucosa of the pelvic urethra. Stroma: Surrounded by a fibromuscular capsule with many septa, parenchyma: Secretory portions are lined by a simple cuboidal or columnar epithelium, occasionally concentrically laminated concretions of secretory material are found. Function: Prostatic secretions contain proteolytic enzymes, acid phosphatase, citric acid, and fibrinolysin (One of the functions is to initiate active movements of the ejaculated spermatozoa)

  
• Bulbourethral gland


  • Pair of glands, stroma: Ensheathed by a fibroelastic capsule containing a variable amount of smooth muscle cells with several septa, parenchyma: Secretory portions are lined with a tall simple columnar or cuboidal epithelium. Function: Produce the preejaculate fluid that lubricates the urethra before ejaculation and neutralize the urethral environment
• Urethra


  • Divided into prostatic, membranous, and spongiose portions (penile urethra). Tunica mucosa: Predominant lining is a transitional epithelium with variably sized patches of simple columnar epithelium, stratified columnar epithelium, or cuboidal epithelium. Propria-submucosa: Dense irregular C.T. Tunica muscularis: Smooth muscle in the vicinity of the bladder or striated muscle in the remainder of the urethra. Tunica adventitia: Loose or dense irregular C.T.
• Parts of the penis

  • Roots
  • Body
  • Glans penis
• Corpora cavernosa penis


  • Paired erectile structures surrounded by the tunica albuginea, a connective tissue septum completely (in the stallion and dog) or partially divides the corpora cavernosa penis. The spaces between the tunica albuginea and the trabecular network are filled with erectile tissue; this tissue consists of caverns lined by endothelium and surrounded by C.T and smooth muscle cells. The cavernous spaces receive their main blood supply from arteries with a helical arrangement that are referred to as helicine arteries