Lecture 24Outline of Current Lecture I. Male Reproductiona. Structuresb. Sexual Responsesc. Spermatogenesisd. Sertoli Cellse. Testosteronef. Hormonal Controlg. Problems with Exogenous Testosteroneh. Developmental AspectsCurrent LectureMale ReproductionStructures:- Testeso -Tunics:1. Tunica vaginalis - from peritoneum (visceral)2. Tunica albuginea - fibrous capsuleo -Blood Supply --Testicular arteries: branch from descending aorta --Pampiniform plexus: testicular veins --Spermatic cord: contains arteries, veins, nerves, & lymphatics --> supply testes & vas deferenso -Lobules: 250-300 of these; each one contains 1-4 seminiferous tubuleso -Seminiferous tubules --Function: produce sperm; surrounded by interstitial cells --Interstitial cells: produce androgen (testosterone)- Epididymiso -Composed of: 20ft of duct (in 1 ½" long organ)o -Regions: --Head --Body --Tailo -Duct Histology: --Mucosa: pseudostratified columnar epithelium ---Stereocilia: non-motile microvillio Absorb testicular fluido Pass nutrients to sperm --Muscularis: smooth muscle- Scrotumo -Description: sac of skin & superficial fasciao -Contains: testes, epididymis, & spermatic cordo -Function: thermoregulation (keeps testes 3C lower than body core temperature) BIOL 320 1st Editiono -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 glando --Membranous urethra: passes through urogenital diaphragmo --Spongy urethra: in penis- Accessory Glandso -Overall function: produce seminal fluido -Seminal vesicle: 60% of semen volume; alkaline, fructoseo -Prostate: 35% of semen volume; enzymes, citrates (slightly acidic), prostate-specific antigen; partially activates spermo -Bulbourethral gland: mucous secretion prior to ejaculation to clear any traces of acidic urine; can contain sperm & transmit STDso -Semen: testicular fluid, sperm, seminal vesicle fluid, and prostate fluid; contains fructose, ascorbic acid; coagulating enzymes, prostaglandins (induce reverse peristalsis in female reproductive tract)- Peniso -Function: sperm deliveryo -Root: site of attachmento -Shaft: free portiono -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- Erectiono -Definition: enlargement/stiffening of penis caused by increased blood flowo -Initiated by: sexual stimuli, erotic sights/sounds/thoughts/smells; can be induced/inhibited by emotional or increased mental activityo -Mechanism:1. P-ANS reflex promotes release of NO2. NO relaxes vascular smooth muscle --> vasodilation3. Erectile tissues fill with blood4. Expansion of corpora cavernosa compresses drainage veins --> maintain engorgement keeping urethra open (sperm can pass through)o Treatments for erectile dysfunction: Viagra, Cialis, Levitra- Ejaculationo -Definition: propulsion of semen from the male reproductive tracto -Mechanism:1. S-ANS kicks in2. Reproductive ducts/accessory organs contract & empty contents3. Bladder sphincter contracts (prevent urine escape)4. Bulbospongiosus muscle contracts rapidly5. Semen ejaculatedo -Systemic effects:1. Increased blood pressure2. Increased heart rate3. Generalized muscle contractions4. 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 Spermiogenesiso Meiosis- Two Compartments:o Adluminal compartmento Basal compartment--Sertoli Cells (Sustentacular Cells): surround developing gametes- -Surround developing gameteso --Formation of compartments: bound by tight junctionso --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-selfo --In the adluminal compartment, sertoli cells…1. Deliver nutrients to sperm2. Move sperm toward lumen3. Secrete testicular fluid4. Get rid of excess cytoplasm5. Secrete chemicals to mediate processTestosterone- -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 characteristicso 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 effectsDevelopmental 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;