Male Reproduction Physiology II PDF 2024 Ross University

Male L. Segabinazzi 2024  Male fertility requires Physiology MM II - Reproduction Competent spermatogenesis Endocrine regulation Thermoregulation Spermatocytogenesis Mitosis, meiosis Spermio...

Male L. Segabinazzi 2024  Male fertility requires Physiology MM II - Reproduction Competent spermatogenesis Endocrine regulation Thermoregulation Spermatocytogenesis Mitosis, meiosis Spermiogenesis Morphological transformation Functional delivery system Accessory glands Erection, ejaculation Libido  Male Physiology MM II - Reproduction Endocrinology of Male Reproduction Anti-Mullerian Hormone (AMH) Gonadotropin releasing hormone (GnRH) Luteinizing hormone (LH) Follicle stimulating hormone (FSH) Testosterone (T4) Estradiol (E2) Inhibin (INH)  Hormones Physiology MM II - Reproduction AMH Low levels in postnatal male Produced by immature Sertoli cells Elevated in cryptorchidism compared to castrated males (Diagnostic test on single blood test) LH Acts on Leydig cells – induce Testosterone secretion FSH Acts on Sertoli cells – major action is to promote protein synthesis (ABP) Estradiol Secreted by Sertoli cells – cause negative feedback to the anterior pituitary for the synthesis of FSH. Androgen binding protein (ABP) Secreted into the seminiferous tubules. It serves to ensure a constant high intratubular concentration of testosterone essential for the function of the epididymis, and possibly other accessory glands.  Hormones Physiology MM II - Reproduction Testosterone Produced by Leydig cells 100 to 500x higher in the seminiferous tubules Exchanges occurs in the pampiniform plexus, so arterial blood entering the testes has high concentration Negative feedback on hypothalamus decreases GnRH and therefore FSH and LH secretion by pituitary Dihydrotestosterone (DHT) More potent than testosterone Local conversion in Sertoli cells and prostate Mediator of sexual development and secondary sex characteristics Phenotype Importance in clinical practice Mediator of Benign Prostatic Hyperplasia (BPH) 5-α reductase inhibitors (e.g. finasteride) – Humans and dogs  Hormones Physiology MM II - Reproduction Hypothalamic centers ▪ Hypothalamic centers ▪ Tonic (MALES) – Regulates the release of frequent low amplitude tong GnRH pulses ▪ Surge - Only in females – responsive to high levels of estradiol and release of high amplitude GnRH pulse Regulate by levels of Testosterone and Estrogens  Male endocrinology * Physiology MM II - Reproduction I Brain (-) Steroides (-) Opióides Seasonality Melatonin HYPOTHALAMUS (+) Gonadotropin concentrations GnRH decrease during the non-breeding season HIPOPHYSIS Driven by effect of photoperiod on pineal gland and subsequent production of melatonin (which is Testosterone (-) FSH LH Estrogens (-) secreted mainly at night) However Inibin (-) Mammal males are not as drastically affect by seasonality as females Some reptiles present 8 T4 spermatogenesis quiescence SERTOLI LEYDIG Testis  Male anatomy Physiology MM II - Reproduction Anatomy Scrotum Testis Epididymis Ductus deferens Accessory glands Penis Prepuce  Male anatomy Physiology MM II - Reproduction Scrotum Testes Oval, laterally compressed Blood supply Vertical in bulls and rams; more horizontal in External pudendal artery stallions, dogs, cats, and pigs Nerves Blood supply From 2nd and 3rd lumbar roots Originates from the anterolateral surface of the abdominal aorta (Genitofemoral nerve) Testicular artery follows a tortuous route Lymph drainage before entering the testis Superficial inguinal lymph Testicular vein: Pampiniform plexus node Lymphatic drainage: Scrotal skin Lumbar lymph Thin nodes Sweat glands Delicate Ginther 2007  Testicular thermoregulation Physiology MM II - Reproduction Testes approximately 3.1 °C/5.6 °F lower than core body temperature Scrotal skin Thin, numerous sweat glands Tunica dartos similar to cremster muscle Pampiniform plexus Countercurrent arterio-venous exchange coolet the blood in the temperature becomes Cremaster muscle Originates from internal oblique Whole body response Elevated scrotal temperature (in rams) → increased respiratory rate!  Pampiniform plexus also helps to Physiology MM II - Reproduction Network of veins and artery - Convoluted veins and artery that drain blood and help thermoregulation. Thermoregulation Countercurrent Concentration of testosterone Countercurrent blood testis barrier it can break the Reduced pulsatility Contorted and long if is higher Blood testis barrier  Testis Physiology MM II - Reproduction Seminiferous tubules Sertoli cells Spermatogenic cells Rete testis Efferent ducts Interstitial cells of Leydig Seminiferous tubules Leidig cells Sertoli cells Basal lamina  Male Physiology MM II - Reproduction Blood-Testis Barrier Maintains a unique environment for the development and maturation of germ cells Protects germ cells from noxious agents Prevents autoimmune response to sperm toxicity Structure Specialized capillary endothelium Non-fenestrated Basement membrane Specialized (tight) junctions between neighboring Sertoli cells  Male Physiology MM II - Reproduction Epididymis Head, body and tail Macroscopically, more or less cylindrical Single tortuous duct – up to 15 m long Functions in sperm maturation, storage, and transit – motility and fertility capacity All epididymal functions are androgen (Testosterone) dependent  Male Physiology MM II - Reproduction Accessory Glands Species Ampulla Prostate Vesicular Bulbourethral Gland Gland Cat + + Dog + Stallion + + + + Bull + + + + Ram/Buck + + + + Boar (Pig) + + + Camelid + + Fvention in the process the sperm Production of seminal plasma help have a sexual glands will Most species Spermatogenesis Physiology MM II - Reproduction Sperm function requires development and maturation through the testis and epididymis Overall 60ish days Spermatogenesis Bull - 61 days Ram – 48 days Boar – 39 days Stalion – 59 days Rabbit – 48 days Dog – 61 days Man – 74 days  Male Physiology MM II - Reproduction Penis and erection stimulation and evation Sensory - Pudendal nerve – initiation of erection and compressing of the veins in the penis, which helps to maintain blood in the erectile tissues most Parasympathetic stimulus (external) - pelvic nerve - smooth muscle relaxation in the corpora cavernosa, allowing increased blood flow into the penis Two basic variations of penile structure in domestic animals Musculocavernous in stallions, dogs, cats (increase in size due to blood engorgement within corpus cavernosum penis, and to a lesser extent in corpus spongiosum penis) - enormous blood supply for erection Fibro elastic Fibrous in ruminants, boar, camelids. A strong tunica albuginea prevents substantial increase in diameter; increase in length involves relaxation of retractor penis muscle and extension of sigmoid flexure of penis - low addition of blood volume but enormous increment in blood pressure  Male Physiology MM II - Reproduction Erection Sympathetic system (“automatic”) - controls “fight-or-flight” responses - put your body’s systems on alert. In other words, this system prepares the body for strenuous physical activity. Its effects include increasing your heart rate and breathing ability, improving your eyesight and slowing down processes like digestion Associated with the detumescence (the return to a flaccid state) of the penis and ejaculation Parasympathetic system - regulates "rest-and-digest" or "feed and breed" activities that occur when the body is at rest, especially after eating, including sexual arousal, salivation, lacrimation (tears), urination, digestion, and defecation.  Male Physiology MM II - Reproduction Erection and ejaculation Fonte: McKinnon, 2014.  Male Physiology MM II - Reproduction Ejaculation EJACULATION/EJECTION EMISSION Ejection of sperm from epididymis Ejection of semen from urethra and seminal fluid from the sexual glands to the urethra Parasympathetic Sympathetic Reflex afferents – stimulus Efferent - stimulus from the brain from the penis towards to the towards to the reproductive tract brain Hypogastric nerve to muscles Glans penis to pudendal nerve Neuro-endocrine loop to spinal cord Oxytocin  Male Physiology MM II - Reproduction Libido Genetically determined fortune levels tee Threshold level of Testosteronehigh of Estradiol 5α Reductase  Male Physiology MM II - Reproduction Seminal fluid (seminal plasma) Testes Accessory sex glands – mainly from Ampullae, Vesicular glands, Prostate, Bulbourethral glands, depending on species Prostaglandins, Citrate, Fructose, Zinc, Mucus, antioxidants etc. Important for sperm motility, metabolism, uterine contraction, DNA stabilization, control of capacitation, immunoregulation and much more β-Nerve Growth Factor (camelids) Ovulation Inducing Factor (OIF) finished  Male Physiology MM II - Reproduction Copulation Visual stimuli Penile sensation Musculoskeletal system Initiate ejaculation  Lorenzo Segabinazzi, DVM, MSc, PhD Ross University School of Veterinary Medicine THANK YOU [email protected] VETERINARY.ROSSU.EDU ©2021 Ross University School of Veterinary Medicine. 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