Lecture 1 - Anatomy of the Male Reproductive System PDF

PP2201 Reproduction Lecture 1 Assoc. Prof. Damien Paris [email protected]  Reproductive Physiology Lecturer: Assoc. Prof. Damien Paris Gamete & Embryology (GAME) Lab College of Public Health, Medical & Veterinary Sciences Room: DB047-109D Tel: 07 4781 6006 Email: dami...

PP2201 Reproduction Lecture 1 Assoc. Prof. Damien Paris [email protected]  Reproductive Physiology Lecturer: Assoc. Prof. Damien Paris Gamete & Embryology (GAME) Lab College of Public Health, Medical & Veterinary Sciences Room: DB047-109D Tel: 07 4781 6006 Email: [email protected] Facebook: https://www.facebook.com/gamete.embryo.lab/ URL: https://portfolio.jcu.edu.au/researchers/damien.paris/  Background: BSc Hons (Monash U), PhD (U Melb) Research Fellow (U Glasgow & U Utrecht)  Research Interests:  Impact of adverse conditions (IVF, heat-stress, social-stress, disease, maternal- age) on fertility (various production & wild animals)  Assisted reproduction for animal breeding & conservation (marsupials, African wild dogs, frogs & production animals)  Techniques used:  highly sensitive reproductive & molecular tools as ‘barometer’ to detect compromised viability in sperm, oocytes & embryos I don’t feel so good!  Sperm quality evaluation: concentration, motility, morphology, viability, DNA damage (computer analysis, microscopy & FACS) live damaged dead intact  Oocyte & embryo health evaluation: viability, development, morphology, heart-rate, DNA damage (microscopy & protein/gene expression) live NANOG dead GATA6  Assisted reproductive techniques: semen collection, sperm freezing, artificial insemination, IVF  Impact of heat-stress on sperm DNA integrity & mitigation by antioxidants in the boar Contact me for future student research opportunities  Sperm banking & artificial insemination as conservation management tools for endangered African wild dogs  Developing advanced reproductive techniques to detect infertility & accelerate selective breeding in barramundi  Impact of chytrid fungus on sperm quality in endangered Corroboree frogs  Development of redclaw crayfish sperm, egg & embryo technologies for commercial crayling production  Integrating spatial & reproductive sciences to conserve endangered pygmy hippos  Scrotum & testes  Penis  Male duct system  Accessory glands  Semen  Background reading:  Marieb & Hoehn 2013 Human Anatomy & Physiology. 9th edition – Chapter 27 (via LearnJCU)  Describe the location, structure & function of the testes  Describe the location, structure & function of the accessory reproductive organs of the male  Discuss the sources & functions of semen The Gonads:  Testes in males  Ovaries in females  Produce sex cells – gametes (sperm & oocytes respt.)  Secrete steroid hormones – sex hormones Accessory Reproductive Organs:  Remaining reproductive ducts, glands & external genitalia  Sac of skin & superficial fascia that hangs outside the abdomino-pelvic cavity at the root of the penis  Contains paired testes Marieb & Hoehn 2010  Vulnerable position....what are the benefits???  sperm production is highly temperature sensitive  Superficial location permits a testicular temperature that is ~3°C lower than core body temperature  Regulated by temperature changes:  cold temperature: scrotum raised to body & becomes heavily wrinkled (reducing surface area & heat loss)  warm temperature: scrotum hangs lower & skin relaxes (increasing surface area & distance from the body for cooling)  Marieb & Hoehn 2010  Dartos muscle: smooth muscle in superficial fascia that wrinkles scrotal skin  Cremaster muscle: skeletal muscle that arise from internal oblique muscles of the trunk that elevate testes  Lie within the scrotum  ~4 cm long & 2.5 cm wide  Primary function:  produce sperm  produce steroids (androgens such as testosterone) Marieb & Hoehn 2010  Each testis is divided into lobules contains 1-4 tightly coiled seminiferous tubules (site of spermatogenesis)  Sperm pass from the seminiferous tubules through the rete testis & into the efferent ducts of the epididymis  In the epididymis, sperm undergo further maturation (acquire motility & fertilization ability) & storage until ejaculation Marieb & Hoehn 2010  Marieb & Hoehn 2010 Sertoli cell Leydig cells  interstitial (Leydig) cells: produce androgens (testosterone)  sustentacular (Sertoli) cells: support spermatogenesis  spermatogonia, spermatocyte & spermatid: form sperm  myoid cells: contract to move sperm & fluid through tubules   Testicular arteries branch from the abdominal aorta superior to the pelvis (37°C blood)  Testicular veins arise from a network called the pampiniform venous plexus (34°C blood)  Cooler venous blood absorbs heat of arterial blood before it enters testes Marieb & Hoehn 2010 ram Senger 2005  Male copulatory organ – delivers sperm into female reproductive tract  Attached root & free shaft that ends in an enlarged tip known as the glans penis  Loose fold of skin that covers the glans penis is called the prepuce or foreskin Marieb & Hoehn 2010 Internal anatomy:  spongy urethra: urinary & ejaculatory duct  corpus spongiosum: surrounds urethra & extends from glans to bulb of penis  corpora cavernosa: paired dorsal erectile bodies extends from base of glans to crus of penis Erection occurs when vascular Marieb & Hoehn 2010 spaces fill with blood  Epididymis  Ductus deferens (vas deferens)  Ejaculatory duct  Urethra Marieb & Hoehn 2010  Regions:  caput (head)  corpus (body)  cauda (tail)  Structure:  highly coiled duct ~6 m Marieb & Hoehn 2010  pseudo-stratified epithelia with stereocilia  Function:  sperm maturation (acquisition of motility & fertilizing ability)  sperm storage in cauda possible for several months  sperm are ejaculated from the caudal epididymis not the testes  Also called vas deferens  ~45 cm long  Runs upwards from the epididymis through the inguinal canal into pelvic cavity  Descends over the posterior bladder wall  Terminal end expands to form the ampulla of ductus deferens  Finally joins with duct of the seminal vesicle to form the ejaculatory duct  Structure:  mucosa: pseudo-stratified epithelium  muscular layer: thick layers of smooth muscle  Ejaculation:  peristaltic waves of smooth muscle contraction expel sperm into the urethra What does vasectomy mean? How does it work as an effective form of contraception? ?  Terminal portion of the male duct system  Conveys both urine & semen  Three regions:  prostatic urethra  membranous urethra  spongy urethra  Mucosa contains scattered urethral glands that secrete mucus into the lumen just before ejaculation Marieb & Hoehn 2010  Seminal vesicles  Seminal vesicles  Prostate  Bulbourethral glands Bulbourethral glands Produce the bulk of the seminal plasma Marieb & Hoehn 2010 The Seminal Vesicles:  Large hollow glands (~15 cm uncoiled)  Outer fibrous capsule with thick inner layer of smooth muscle (contracts during ejaculation)  Secrete yellow viscous alkaline fluid containing fructose, ascorbic acid, coagulating enzymes & prostaglandins (enhance sperm motility/fertilization)  Account for 70% of semen volume The Prostate:  Single doughnut-shaped gland that encircles the urethra just inferior to the bladder  Outer thick capsule containing 20-30 compound tubulo-alveolar glands embedded in smooth muscle & connective tissue  Secretes milky acidic fluid containing citrate, several enzymes & prostate specific antigen (activates sperm)  Account for up to 30% of semen volume  Contraction of smooth muscle causes prostatic secretions to enter the urethra The Bulbourethral Glands:  Inferior to the prostate  Secretes a thick clear alkaline mucus (neutralises traces of acidic urine in urethra prior to ejaculation) Why would traces of urine be a problem at ejaculation? ?  Mixture of sperm, testicular fluid & accessory gland secretions  Function:  transport medium for sperm  provides nutrients & chemicals that protect & activate sperm  facilitate sperm movement  Components:  Prostaglandins: stimulate contraction in female tract (facilitates sperm uptake)  Relaxin: enhances sperm motility  Clotting factors: promote semen coagulation Typical ejaculate is 2-5 ml of semen containing 15 – 150 x 106 sperm/ml (pH 7.2)