The Male Reproductive System
Components Scrotum Testes Duct system Penis Accessory glands
Scrotum Skin Dartos muscle (smooth) wrinkles Septum Cremaster muscle (skeletal) (lifts)
Scrotum Temperature Spermatic cord 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 (aka ductus defrens)
Testes – gross anatomy ~4 cm long, 2.5 cm wide Tunica vaginalis Tunica albuginea (capsule) Septa 250-300 lobules Seminiferous tubules Epididymis
Descent of the Testes 3 mos. 7 mos. birth
Seminiferous tubules Spermatogenic cells Spermatogenesis begins at puberty ~400 million sperm/day
Spermatogenic cells Spermatogonia Primary spermatocytes 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 Spermatid
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 Midpiece Tail Nucleus Acrosome (lysosome) Midpiece Base of tail Mitochondria Tail Long flagellum
Spermiogenesis Spermatid 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
Sustentacular cells 2 Sertoli cells with associated spermatogenesis cells.
Interstitial (Leydig) cells Secretes testosterone sER for steroid production Controlled by LH from pituitary
Ducts Epididymis Ductus deferens Ejaculatory duct (urethra)
Epididymis Located in scrotum Between seminiferous tubules and vas deferens ~6 m long
Epididymis Pseudostratified columnar epithelium With stereocilia (long microvilli) Smooth muscle Sperm mature and stored
Ductus (vas) deferens From scrotum to pelvis Forms ejaculatory duct with seminal vesicle duct Empties into prostatic urethra Thick muscularis Propels sperm during ejaculation
Ductus deferens Microscopic anatomy Pseudostratified epithelium Lamina propria Muscularis Inner longitudinal Middle circular Outer longitudinal
Urethra Shared with urinary system Prostatic urethra Membranous urethra Spongy (penile) urethra
Accessory Glands Seminal vesicle 60% of semen Fructose to nourish sperm
Prostate Gland Prostate gland Surrounds prostatic urethra 30% of semen Supports sperm
Penis Thin skin Spongy urethra Erectile bodies Corpus spongiosum 2 corpora cavernosa Capsule Vascular spaces CC cs
Erection Sexual excitement (parasympathetic) blood flow to erectile bodies Squeezes veins shut blood pressure in erectile bodies
Ejaculation Sympathetic activation Peristaltic contraction of smooth muscles in ducts and glands - ejaculation Constriction of arteries blood pressure in erectile bodies