The Male Reproductive System Differentiation of the Embryo Gonad Development The male and Female gonads are derived embryologically from the same site in the body All fetuses start out as female Under the influence of the Y chromosome masculization occurs Default development is female A gene on the Y chromosome identified as SRY starts a chain of geneexpression reactions that causes STEROID SYNTHESIS specifically TESTOSTERONE which causes the testis development pathway Without testosterone the default or female pathway is followed Sexual Dimorphisms The glands penis and its prepuce and the clitoris and its prepuce are actually sexually dimorphic analogous structures They both contain a shaft glands and spongy tissue which becomes engorged with blood when stimulated They are highly sensitive Penile Components The scrotum is the pouch that contains the testes and maintains their temperature at approximately 93 6 degree Fahrenheit to allow for spermatogenesis Epididymis where the mature sperm are stored located at surface of each testis The Vas Deferentia which join the ducts of the seminal vesicles provide secretions that nurture the sperm Cowper s Glands flank the urethra and secrete clear mucus like fluid that appears as preejaculatory fluid Human Male Anatomy Sperm are produced in the testes which are located in the scrotum Before birth the testes form in the embryo s abdomen and then descend into the scrotum Sperm require a temp that is 3 degrees Celsius below body temp That is why they are outside the abdomen Muscles help regulate temp Components Scrotum Testes Duct system Penis Accessory glands 24 1 Scrotum Skin Dartos muscle smooth Septum Cremaster muscle skeletal 24 2 Scrotum Temperature Optimal for sperm development is 3 C below body temp 91 F Controlled by muscles Spermatic cord Testicular artery Plexus of veins Nerves vas deferens 24 2 Testes gross anatomy 4 cm long 2 5 cm wide Tunica vaginalis Tunica albuginea capsule Septa 250 300 lobules Seminiferous tubules Epididymis 24 3 Descent of the Testes 3 mos 7 mos birth 24 29 Seminiferous tubules Spermatogenic cells Spermatogenesis begins at puberty 400 million sperm day 24 3b Gametogenesis Spermatogenesis Vs Oogenesis Spermatogenic cells Spermatogonia On basal lamina Mitosis Primary spermatocytes 1st meiotic division Secondary spermatocytes 2nd meiotic division Spermatid Haploid 4 from each 1 spermatocyte 24 4b Seminiferous tubules Spermatogenesis Spermatogonia 1 spermatocyte 2 spermatocyte Spermatid 24 4c Hormones Spermatogenesis controlled by FSH follicle stimulating hormone from pituitary Testosterone from Leydig interstitial cells of testes secretions from Sertoli cells Spermiogenesis Spermatid spermatozoan Head Nucleus Acrosome lysosome Midpiece Base of tail Mitochondria Tail Long flagellum 24 5 Spermiogenesis Spermatid 24 5 spermatozoan Sustentacular Sertoli cells Nurse cells Extend from basal lamina to lumen Connected to each other by tight junctions Nourish spermatogenic cells Transport spermatogenic cells Phagocytize excess cytoplasm Secretions regulate spermatogenesis 24 4c Sustentacular cells 2 Sertoli cells with associated spermatogenesis cells 24 4c Interstitial Leydig cells Secretes testosterone sER for steroid production Controlled by LH from pituitary 24 3b Ducts Epididymis Ductus deferens Ejaculatory duct urethra 24 1 Epididymis Located in scrotum Between seminiferous tubules and vas deferens 6 m long 24 3a Ductus vas deferens From scrotum to pelvis Forms ejaculatory duct with seminal vesicle duct Empties into prostatic urethra Thick muscularis Propels sperm during ejaculation 24 1 Urethra Shared with urinary system Prostatic urethra Membranous urethra Spongy penile urethra 24 8 Accessory Glands Seminal vesicle 60 of semen Fructose to nourish sperm 24 1 Prostate Gland Prostate gland Surrounds prostatic urethra 30 of semen Supports sperm 24 9 Penis Thin skin Spongy urethra Erectile bodies Corpus spongiosum 2 corpora cavernosa Capsule Vascular spaces 24 8 Epididymis slide In PowerPoint file for male reproductive system http www southalabama edu biomedic al 311Anatomy BMD311 htm Erection Sexual excitement parasympathetic blood flow to erectile bodies Squeezes veins shut blood pressure in erectile bodies 24 8 Ejaculation Sympathetic activation Peristaltic contraction of smooth muscles in ducts and glands ejaculation Constriction of arteries blood pressure in erectile bodies 24 8