Male Reproductive System PDF

Male Reproductive System Chapter 27 Pages 1008-1031 The Descent Male Reproductive Anatomy  Terminology Gonads – Primary Reproductive organs Testes Ovaries Gametes – Reproductive cells Sperm or Spermatozoa Oocyte (called an Ovum wh...

Male Reproductive System Chapter 27 Pages 1008-1031 The Descent Male Reproductive Anatomy  Terminology Gonads – Primary Reproductive organs Testes Ovaries Gametes – Reproductive cells Sperm or Spermatozoa Oocyte (called an Ovum when sperm begins to fertilize) Zygote – Union of two gametes  Male Reproductive Anatomy Testis – Male gonads that produce spermatozoa Epididymis – Stores Spermatozoa Vas Deferens – Tube connecting testes to urethra Seminal Vesicle – Produces secretion, which aids in spermatozoa survival as well as provides fluid for sperm to move in Urethra – Dual function Spermatozoa (sperm) Produced in the testes Stored in the epididymis Transported through the ductus (vas) deferens to accessory glands Accessory glands activate and provide aid for spermatozoa  Spermatic Cord Spermatic cord consists of layers of fascia and muscle enclosing: Ductus (vas) deferens Testicular artery, nerves, and lymphatic vessels Pampiniform Plexus of a Testicular vein Penetrates through the inguinal canal (a passage through the abdominal musculature) The presence of the spermatic cord creates a weakness that can lead to an inguinal hernia Turn your head and cough Male Inguinal Hernias Protrusions of visceral tissue (usually small intestine) into the inguinal canal  Scrotum Is divided into 2 chambers, or scrotal cavities Each testis lies in a separate scrotal chamber 2 muscles involved Dartos muscle Resting tone keeps the testes elevated Wrinkling of the scrotal surface Cremaster muscle Tenses the scrotum to pull testes closer to the body Why do we have these muscles? Cremaster reflex Stroke inner thigh will cause the scrotum to move the testes closer to the body  Temperature Regulation Normal sperm development in testes: requires temperatures ~2°F lower than body temperature The Dartos and Cremaster Muscles help regulate the testes temperature to allow proper conditions to produce spermatozoa i.e. In cold temperatures, testes are brought close to the body to help increase temp.  Seminiferous Tubules Produce sperm Each is about 80 cm long If we uncoiled all of these tubules and stretched them out, they would stretch roughly half a mile! New sperm are produced continually  Leydig Cells aka Interstitial Endocrine Cells Cells between the seminiferous tubules Produce androgens: Male sex hormones Testosterone - most important androgen  Spermatogenesis The process of sperm production Begins at outermost cell layer in seminiferous tubules The word seminiferous means sperm producing Proceeds toward the lumen 2n = 2*23 = 46chromosomes 2n x 2 = 92 chr Spermatogenesis n = 23 chr Spermatogonium (2n) Mitosis (not illustrated) Primary Spermatocyte (2n x 2) Meiosis I Secondary Spermatocyte (n x 2) Meiosis II Spermatid (n) Spermiogenesis (maturation) Spermatozoa (sperm) 2n = 2*23 = 46chromosomes 2n x 2 = 92 chr Spermatogenesis n = 23 chr Spermatogonium (2n) Mitosis (copy) Primary Spermatocyte (2n x 2) Meiosis I Secondary Spermatocyte (n x 2) Meiosis II Spermatid (n) Spermiogenesis (maturation) Spermatozoa (sperm)  Spermatogenesis 23chr 23chr 22+x 22+y 23 Chr 46chr 46chr 46 Chr 23 sister Meiosis II chromatids 23 Chr 46 Meiosis I 46 Chr pairs Haploid Mitosis 46 sister chromatids 23 Chr Spermatogonium Primary Spermatocyte 46 Chr 23 Chr Secondary Spermatocyte Spermatids  Spermiogenesis & Spermiation Final Steps of Spermatogenesis Spermiogenesis (maturation) Each spermatid matures into one spermatozoa (sperm) Still attached to nurse cell Spermiation (detachment) Spermatozoa loses attachment to nurse cell Enters lumen of seminiferous tubule The whole process – from Spermatogonium to Spermiation - takes about 64 days.  Nurse Cells aka Sustentacular Cells aka Sertoli Cells Surround spermatids Provide nutrients and chemical stimuli for development They nurse the sperm through development Stimulated by FSH & Testosterone Secretes Inhibit & Androgen Binding Protein  Sperm Maturation Testes produce physically mature spermatozoa that can not fertilize an oocyte Other parts of reproductive system are responsible for Functional maturation Nourishment Storage Transport This guy can’t swim yet!  Sperm Regions Mature sperm Head Acrosomal enzymes 23 Chromosomes Midpiece – Mitochondria (energy) Tail Propels the sperm Sperm Maturation Spermatozoa (Sperm) detach from nurse cells Free in lumen of seminiferous tubule Physically Mature Functionally Immature Are incapable of locomotion or fertilization Are moved by cilia lining efferent ductules into the epididymis n = 23 46 Spermatogonium (2n) Mitosis ~16 days 46 Primary Spermatocyte (2n x 2) Meiosis 1 Inside the nurse ~24 days 46 46 Secondary Spermatocyte (n x 2) cells of the Meiosis 2 seminiferous tubules ~4 hours 23 23 23 23 Spermatid (n) Spermiogenesis ~24 days Physical maturation 23 Spermatozoa (n) Spermiation Detachment from nurse cells 23 Spermatozoa (n) Leaves through the lumen of the seminiferous tubules to the epididymis Spermatozoa are Physically Mature Functionally Immature Sperm Maturation  Epididymis Monitors and adjusts fluid produced by seminiferous tubules Recycles damaged spermatozoa Stores and protects spermatozoa Facilitates Functional Maturation ~2-3 weeks Spermatozoa Leaving Epididymis are: Physically Mature Functionally Mature Immobile (can’t swim) Spermatozoa still need to undergo capacitation To become motile and capable of fertilization 2 Steps In Capacitation 1. Spermatozoa become motile(actively swimming) : when mixed with secretions of seminal vesicles 2. Spermatozoa become capable of fertilization: when exposed to female reproductive tract  Ductus (Vas) Deferens Curves inferiorly along urinary bladder: toward prostate gland and seminal vesicles Lumen enlarges into ampulla Wall contains thick layer of smooth muscle Peristaltic contractions sperm can spend several months in the vas deferens Ejaculatory Duct Is a short passageway (2cm) at junction of ampulla and seminal vesicle duct Penetrates wall of prostate gland Empties into urethra Male Accessory Glands Each Contribute Fluids To Create Semen: Seminal Vesicles (60%) aka Seminal Gland Prostate Gland (30%) Bulbourethral Glands (5%) Remaining 5% from the nurse cells and epididymis Male Accessory Glands Function Activating spermatozoa Providing nutrients spermatozoa need for motility Propelling spermatozoa and fluids along reproductive tract peristaltic contractions Produces buffers to counteract acidity of urethral and vaginal environments  Seminal Vesicles Secretions Fructose easily metabolized by spermatozoa Prostaglandins stimulate smooth muscle contractions (male and female) Fibrinogen forms temporary semen clot in vagina  Seminal Vesicles Secretions 60% of final volume of semen slightly alkaline [↑pH] neutralizes acidic secretions in prostate gland and vagina Initiates the first step in capacitation: When the secretions mix with the spermatozoa, their flagella start beating and become highly motile Are discharged into ejaculatory duct at emission: when peristaltic contractions are underway Contractions are controlled by sympathetic nervous system  Prostate Gland Prostatic Fluid Slightly acidic Forms 20–30% of semen volume Contains antibiotic seminalplasmin Helps prevent UTI’s in males Is ejected into prostatic urethra: by peristalsis of prostate wall  Bulbourethral Glands aka Cowper Glands Secrete thick, alkaline mucus: helps neutralize urinary acids in urethra It prepares the urethra for the sperm lubricates the glans (tip of the penis) Duct of each gland: travels alongside penile urethra empties into urethral lumen Semen Ejaculate Typical ejaculation releases 2 – 5 ml Is The Volume Of Semen Contains: Produced By Ejaculation Spermatozoa Seminal Fluids (from accessory glands) Enzymes Sperm Count Collected after 36-hours of sexual abstinence Normal range: 15–200 million spermatozoa/ml of ejaculate Low sperm count: < 15 million sperm/ml < 39 million sperm/total ejaculate  Seminal Fluid Protease – help dissolve mucous secretions in vagina Seminalplasmin – antibiotic that kills bacteria, ie E. Coli Prostatic enzyme – coagulates semen by converting fibrinogen to fibrin Fibrinolysin – liquefies clotted semen after 15-30 minutes  Male External Genitalia Penis Is a tubular organ: through which distal portion of urethra passes Conducts urine to exterior Introduces semen into female vagina Scrotum  Circumcision Is the surgical removal of the prepuce (foreskin) Can lead to decreased risk of infection Corpora Cavernosa 2 cylindrical masses of erectile tissue under anterior surface of flaccid penis separated by thin septum encircled by dense collagenous sheath Corpus Spongiosum Surrounds penile urethra Is relatively slender Extends from urogenital diaphragm to tip of penis Expands to form the glans Blood Flow Flaccid state: arterial branches are constricted muscular partitions are tense blood flow into erectile tissue is restricted Erect state: arterial vasodilation venous vasoconstriction blood fills erectile tissue penis stiffens Erection subsides when parasympathetic activity returns to baseline  Blood Flow Parasympathetic Activity Causes Nitric Oxide (Vasodilator) levels to rise in the arteries Viagra (PDE5 inhibitor)  Hypothalamus Hormones GnRH Anterior Pituitary FSH – Follicle Stimulating Hormone LH – Luteinizing Hormone Testes Interstitial (Leydig) cell Stimulated by LH Secretes Testosterone Inhibits release of GnRH Testosterone stimulates Nurse Cells Nurse cell Stimulated by FSH & Testosterone Secretes inhibin Inhibits release of FSH Secretes ABP (Androgen Binding Protein) Increases available androgens (testosterone) Stimulates maturation of spermatids Hormones Gonadotropin-Releasing Hormone (GnRH) Is synthesized in hypothalamus: Carried to pituitary by hypophyseal portal system Is secreted in pulses: At 60–90 minute intervals Control rates of secretion of: FSH and LH Testosterone (in response to LH) Inhibin Inhibits FSH production: In anterior pituitary gland FSH stimulates spermatogenesis Suppresses secretion of GnRH: At hypothalamus Follicle Stimulating Hormone (FSH) High FSH levels: Increase Inhibin production Until FSH returns to normal Low FSH levels: Inhibin production falls FSH production increases Luteinizing Hormone (LH) Targets interstitial cells (Leydig cells) Secretes Testosterone and other androgens  Functions Of Testosterone 1. Stimulates spermatogenesis: promoting functional maturation of spermatozoa 2. Affects CNS function: libido (sexual drive) and related behaviors 3. Stimulates metabolism: especially protein synthesis blood cell formation muscle growth  Functions Of Testosterone 4. Establishes male secondary sex characteristics: distribution of facial hair increased muscle mass and body size characteristic adipose tissue deposits 5. Maintains accessory glands and organs of male reproductive tract  Andropause male climacteric aka Is the period of declining reproductive function Circulating testosterone begins to decline between ages 50 and 60 Circulating FSH and LH increase Sperm production still continues Sexual activity gradually decreases with declining testosterone levels  Male Sexual Function Male Sexual Arousal Leads to increase in parasympathetic outflow over pelvic nerves, which leads to erection Male Sexual Stimulation Initiates secretion of bulbourethral glands Lubricates penile urethra and surface of glans Leads to coordinated processes of emission and ejaculation  Male Sexual Function Emission Occurs under sympathetic stimulation Peristaltic contractions of ampulla Push fluid and spermatozoa into prostatic urethra Seminal glands contract Peristaltic contractions in prostate gland Move seminal mixture into urethra Contraction of urinary internal urethral sphincter Prevents passage of semen into bladder  Male Sexual Function Ejaculation Powerful, rhythmic contractions ischiocavernosus and bulbospongiosus muscles Push semen toward external urethral opening Followed by subsidence of erectile tissue (Detumescence)