Male reproductive system

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  • Created by: Saoirse
  • Created on: 22-12-14 11:15
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  • Male reproductive system
    • Internal anatomy of penis
      • parasympathetic fibres from sacral portion of spinal cord initiate and maintain erection
      • Release and stimulate local production of NO - nitric oxide
        • NO relaxes smooth muscle of arterioles in erectile tissue
      • Relaxation of blood vessel = increased blood flow = erection of penis
    • Spermatogenesis
      • Process of spermatozoa (mature gamete) production
      • Occurs in seminiferous tubes - proceeds from outer layer to lumen
      • Involves: mitosis, meiosis, spermiogenesis
      • Spermatogonia develop from primordial germ cells during week 5 of development
      • Spermiogenesis - formantion of acrosome, development of flagella and multiplication of mitochondria
        • Sperm are haploid (n), unable to swim at this point and incapable of fertilisation
      • Anatomy of spermatozoon
        • lacks many organelles - reduces size/mass, increasing mobility and speed
        • 4 distinct regions
          • Head: densely packed chromosomes, acrosome contains enzymes for fertilisation
          • Neck: centrioles and original spermatid
          • Middle piece: mitochondria
          • Tail: flagellum
      • Becoming fully functional
        • Epididymis
          • Cilia in efferent ductules move immobile spermatozoa into epididymis
          • Has a head body and tail bound to posterior region of each teste
            • Spermatozoa mainly stored in tail
          • Site of sperm functional maturation
          • Peristaltic contractions of smooth muscle and moving fluid transports spermatozoa along epididymis to ductus deferens
        • Ductus deferens
          • transport and storage of spermatozoa
    • Anatomy
      • Testes
        • Spermatic cord: muscle enclosing ductus deferens, blood vessels, nerves and lymphatic system supplying testes
        • Cremaster and dartos muscles: allow accent/descent of testes
        • Rafe: raised thickening of scrotum, externally divides 2 testes
        • Histology
          • Septa subdivide into 200-300 lobules
            • each lobule contains 1-3 seminiferous tubules
          • interstitial (leydig) cells between tubules produce androgens
        • Seminiferous tubules
          • Site of spermatogenesis
          • Spermatogenic cells: spem forming cells
          • Sertoli cells: support spermatogenesis
            • Nurture and provide structural support for sperm during development
            • Roles
              • phagocytosis of degenerated germ cells
              • promotion of mitosis and meiosis (stimulated by FSH and testosterone)
              • Blood-testes barrier- controls composition of fluid in tubule by regulating transport from blood
              • produce inhibin and androgen binding protein (ABP)
      • Seminal vesicles (glands)
        • Active secretory glands = 60% semen vol
        • Alkaline secretion to neutralise acids
          • High conc of fructose
          • Prostaglandins: stimulate smooth muscle contraction
          • Fibrinogen: formation of temporary semen clot upon ejaculation
      • Prostate gland
        • Prostatic fluid (20-30% of semen vol)
          • Proteolytic enzymes help break down clotting proteins from seminal fluid
          • Citric acid: used by sperm for ATP production via Krebs cycle
          • Seminal plasmin: protein with antibiotic properties
          • pH 6.5
    • Semen
      • Alkaline pH 7.2-7.7
      • Composed of spermatozoa and seminal fluid
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