BIOL 320 1st Edition Lecture 24 Outline of Current Lecture I Male Reproduction a Structures b Sexual Responses c Spermatogenesis d Sertoli Cells e Testosterone f Hormonal Control g Problems with Exogenous Testosterone h Developmental Aspects Current Lecture Male Reproduction Structures Testes o Tunics 1 Tunica vaginalis from peritoneum visceral 2 Tunica albuginea fibrous capsule o Blood Supply Testicular arteries branch from descending aorta Pampiniform plexus testicular veins Spermatic cord contains arteries veins nerves lymphatics supply testes vas deferens o Lobules 250 300 of these each one contains 1 4 seminiferous tubules o Seminiferous tubules Function produce sperm surrounded by interstitial cells Interstitial cells produce androgen testosterone Epididymis o Composed of 20ft of duct in 1 long organ o Regions Head Body Tail o Duct Histology Mucosa pseudostratified columnar epithelium Stereocilia non motile microvilli o Absorb testicular fluid o Pass nutrients to sperm Muscularis smooth muscle Scrotum o Description sac of skin superficial fascia o Contains testes epididymis spermatic cord o Function thermoregulation keeps testes 3C lower than body core temperature o How Dartos muscle smooth muscle that wrinkles skin Cremaster muscle skeletal muscle that raises lowers temperature When it s cold contract wrinkle skin hold testes close to body wall When it s hot relax smooth skin push testes away from body wall Vas deferens location of a vasectomy Ejaculatory duct Urethra carries both urine and semen NOT simultaneously o Prostatic urethra region wrapped by prostate gland o Membranous urethra passes through urogenital diaphragm o Spongy urethra in penis Accessory Glands o Overall function produce seminal fluid o Seminal vesicle 60 of semen volume alkaline fructose o Prostate 35 of semen volume enzymes citrates slightly acidic prostate specific antigen partially activates sperm o Bulbourethral gland mucous secretion prior to ejaculation to clear any traces of acidic urine can contain sperm transmit STDs o Semen testicular fluid sperm seminal vesicle fluid and prostate fluid contains fructose ascorbic acid coagulating enzymes prostaglandins induce reverse peristalsis in female reproductive tract Penis o Function sperm delivery o Root site of attachment o Shaft free portion o Internal penis urethra three cylindrical bodies erectile bodies o Erectile tissue net of connective tissue smooth muscle with vascular spaces Copora cavernosum pair of erectile bodies Bound by tunica albuginea Crura legs proximal end surrounded by ischiocavernosus muscle anchor peins to pubic arch Corpus spongiosum Proximal enlargement bulb Distal enlargement glans penis covered by foreskin prepuce Sexual Responses Erection o Definition enlargement stiffening of penis caused by increased blood flow o Initiated by sexual stimuli erotic sights sounds thoughts smells can be induced inhibited by emotional or increased mental activity o Mechanism 1 P ANS reflex promotes release of NO 2 NO relaxes vascular smooth muscle vasodilation 3 Erectile tissues fill with blood 4 Expansion of corpora cavernosa compresses drainage veins maintain engorgement keeping urethra open sperm can pass through o Treatments for erectile dysfunction Viagra Cialis Levitra Ejaculation o Definition propulsion of semen from the male reproductive tract o Mechanism 1 S ANS kicks in 2 Reproductive ducts accessory organs contract empty contents 3 Bladder sphincter contracts prevent urine escape 4 Bulbospongiosus muscle contracts rapidly 5 Semen ejaculated o Systemic effects 1 Increased blood pressure 2 Increased heart rate 3 Generalized muscle contractions 4 Emotional pleasure arousal Spermatogenesis Meiosis of diploid stem cell 46 chromosomes to haploid 23 chromosome mature spermatozoa About 400 million spermatozoa made daily Stem cells spermatogonia undergo mitosis spermatocytes undergo meiosis Haploid maturing cells spermatids Mature gamete spermatozoon Stage occur at specific locations in Sertoli cells Mature spermatozoa travel from seminiferous tubules to epididymis by peristalsis Two Phases o Spermiogenesis o Meiosis Two Compartments o Adluminal compartment o Basal compartment Sertoli Cells Sustentacular Cells surround developing gametes Surround developing gametes o Formation of compartments bound by tight junctions o Blood testis border boundary Why Prevents sperm anitgen from escaping to blood could be attack by immune system sperm not present during thymic education spermatogonia self sperm non self o In the adluminal compartment sertoli cells 1 Deliver nutrients to sperm 2 Move sperm toward lumen 3 Secrete testicular fluid 4 Get rid of excess cytoplasm 5 Secrete chemicals to mediate process Testosterone Synthesized from cholesterol Transformed in some organs to be effective o Prostate dihydrotesterone DHT o Neurons estrogen Responsible for libido in males females Testosterone targets local distant primary secondary sexual characteristics Hormonal Control LH Interstitial Cells Testosterone Blood FSH Sertoli Cells Spermatogenesis with Testosterone produced by interstitial cells Also stimulate male secondary sexual characteristics o Hair muscle mas vocal chords behavior Adam s apple Problems wit Exogenous Testosterone Effectiveness depends on existing body structure Can permanently alter development Negative feedback on LH causes testicular atrophy Can be converted to estrogen feminizing effects Activates gene transcription liver damage cancer Psychological effects Developmental Aspects Week 5 Wolffian ducts form internally primordial germ cells populate these spermatogonia Week 7 under influence of testosterone male structures form internally testes near kidneys externally labioscrotal swelling scrotum genital tubercle penis grows around urethra Month 8 surge of testosterone stimulate testes descent into scrotum cryptorchid failure of one or both testes to descend Puberty organs reach full size function hair beard armpit growth muscle development voice drops Adam s apple