Male Reproductive System - Lecture 10a PDF

Male Reproductive System © 2018 Pearson Education, Inc.  An Introduction to the Reproductive System  Reproductive system – The only system that is not essential to the life of the individual – However does affect other systems – Male and female rep...

Male Reproductive System © 2018 Pearson Education, Inc.  An Introduction to the Reproductive System  Reproductive system – The only system that is not essential to the life of the individual – However does affect other systems – Male and female reproductive organs Produce and store specialized reproductive cells that combine to form new individuals Also secrete hormones that play major roles in maintenance of normal sexual function – Male and female Gonads are the main functional component of this system via production of gametes (AKA reproductive cells) and hormones © 2018 Pearson Education, Inc.  Structures of the Reproductive System  Reproductive system – Required for continued existence of species  Reproductive structures – Gonads—organs that produce gametes and hormones – Ducts receive and transport gametes – Accessory glands secrete supportive fluids into ducts protect gametes – Perineal structures known as external genitalia (I.E. Penis)  Reproductive tract – Includes all chambers and passageways that connect ducts to exterior of body  Male and female reproductive systems – Functionally different – Female release roughly one gamete per month Retains and nurtures zygote – Male produces large quantities of gametes Half a billion sperm per day © 2018 Pearson Education, Inc.  Structures of the Reproductive System  Male reproductive system – Testes (male gonads) Secrete male sex hormones (androgens) Produce male gametes (sperm)  Female reproductive system – Ovaries (female gonads) Release one immature gamete (oocyte) per month Produce hormones – Uterine tubes Carry oocytes to uterus—if sperm reaches oocyte, fertilization is initiated; oocyte matures into ovum – Uterus encloses and supports developing embryo – Vagina connects uterus with exterior © 2018 Pearson Education, Inc.  Male Reproductive Structures  Pathway of sperm – Extensive ductal system between Production in the testis to External release via Urethra – Testis (Production) Epididymis Ductus deferens Ejaculatory duct Urethra (Penis)  Accessory glands secrete fluids into duct system – Seminal glands – Prostate – Bulbo-urethral glands  Testes – 5 cm long, 3 cm wide, 2.5 cm thick – Each weighs 10–15 g – Hang in scrotum  Scrotum – Fleshy pouch that encloses testes – Suspended inferior to perineum – Posterior to base of penis © 2018 Pearson Education, Inc.  Prostatic urethra Pubic symphysis Urinary bladder Major Structures of the Male Reproductive System Ducts Ejaculatory duct Membranous urethra Spongy urethra Ductus deferens Epididymis Gonad Testis Corpus cavernosum External Genitalia Penis Corpus spongiosum External urethral orifice Scrotum © 2018 Pearson Education, Inc. Figure 28–1 Sagittal Section of the Male Reproductive System Ureter The Male Prostate can Rectum be palpitated through the anal canal during Accessory Glands Seminal gland preventive physical Prostate exam to assess prostate cancer and other Bulbo-urethral gland prostate conditions Anus  Male Reproductive Structures  Scrotum – Divided into two chambers by raphe of scrotum Raised thickening in scrotal surface – Each testis lies in a separate scrotal cavity  Tunica vaginalis – Serous membrane – Lines scrotal cavity – Reduces friction between opposing surfaces Parietal (outer) layer Visceral (inner) layer  Dartos muscle – Layer of smooth muscle in dermis of scrotum – Causes characteristic wrinkling of scrotal surface  Cremaster – Layer of skeletal muscle deep to dermis – Tenses scrotum and pulls testes closer to body Due to sexual arousal or decreased temperature © 2018 Pearson Education, Inc.  Male Reproductive Structures – Testes within the Scrotum  Temperature regulation in testes – Normal sperm development Requires temperatures 1.1ºC lower than body temperature – Muscles relax or contract To move testes away or toward body Maintains acceptable testicular temperatures – When it is cold outside the scrotum containing the testes are pulled up toward the body to regulate temperature for spermatogenesis Muscles contract © 2018 Pearson Education, Inc.  Male Reproductive Structures  Gross anatomy of testes – (Located within the Scrotum) – Tunica albuginea Deep to tunica vaginalis Dense layer of connective tissue rich in collagen fibers Continuous with fibers surrounding epididymis Fibers form septa testis that converge near entrance to epididymis Supports blood and lymphatic vessels of testis and efferent ductules © 2018 Pearson Education, Inc.  Male Reproductive Structures: Testes (male Gonads)  Histology of testes (two testes within scrotum) (male gonads) – 2 glands for the production of Sperm Cells and hormones – Septa subdivide each testis into lobules – Seminiferous tubules: Lobules contain about 800 slender and tightly coiled Location of sperm production Each is about 80 cm long Nearly one-half mile of seminiferous tubules in each testis – Areolar connective in spaces between seminiferous tubules – Within those spaces, there are Blood vessels Large interstitial endocrine cells (Leydig cells) – Produce androgens, dominant male sex hormones – Testosterone is most important androgen Connect to rete testis, Efferent ductules connect rete testis to epididymis - sperm & hormones exits the testes and move to the reproductive tracts © 2018 Pearson Education, Inc.  Figure 28–3a Anatomy of the Scrotum and the Testes. Ductus deferens Stores inactive sperm prior to arousal / sexual intercourse Epididymis 2nd stage of Sperm Efferent ductule cell Production Rete Scrotum testis Skin Dartos muscle Superficial Seminiferous scrotal fascia Tubules Cremaster 1 Stage of ST Tunica vaginalis Sperm Cell Production Septa testis Scrotal cavity Septa testis Lobule Raphe of scrotum Red Dotted line surrounds the Testes (male gonad) © 2018 Pearson Education, Inc.  Male Reproductive Structures – Sperm Production  Sperm Production in Regions of Testes  Seminiferous Tubules within the Testes produce immobile sperm that are not yet capable of fertilizing an oocyte – 1st Stage of Sperm Cell Production – Other parts of reproductive system are responsible for Functional maturation, nourishment, storage, and transport of sperm – Immobile sperm from testes Moved by cilia lining efferent ductules into the epididymis  Functions of epididymis – 2nd Stage of Sperm Cell Production – Monitor and adjust composition of fluid produced by seminiferous tubules – Recycle damaged sperm – Store and protect sperm and facilitate their functional maturation © 2018 Pearson Education, Inc.  Male Reproductive Structures  Epididymis – Start of male reproductive tract – Coiled tube almost 7 m long Bound to posterior border of each testis – Has head, body, and tail  Epididymis Structure – Head Largest part Receives sperm from efferent ductules – Body On posterior surface of testis – Tail Begins near inferior border of testis Ascends to connection with ductus deferens Primary storage location of sperm © 2018 Pearson Education, Inc.  Figure 28–5a Anatomy of the Epididymis. Spermatic cord Ductus deferens (AKA Vas Deferens) Storage location of immobile sperm prior to arousal / sexual intercourse – Connects sperm cell production in Efferent ductules testes to other glands that are Straight tubule associated with the activation of sperm and production of complete semen Rete testis Seminiferous Epididymis tubule Tunica Head of epididymis albuginea Body of epididymis Testis Tail of epididymis Scrotal Again: Epididymis is the location cavity of the Second Stage of Sperm a A diagrammatic view of the Cell Production in the testes head, body, and tail of an epididymis © 2018 Pearson Education, Inc.  Male Reproductive Structures -  Ductus deferens (AKA vas deferens) – 40–45 cm long – Begins at tail of epididymis and ascends through inguinal canal – Curves inferiorly along urinary bladder Toward prostate and seminal glands – Lumen enlarges into ampulla of ductus deferens – Wall contains thick layer of smooth muscle Peristaltic contractions propel sperm and fluid – Can store immobile (inactive) sperm for several months – Site for Vasectomy (vas) © 2018 Pearson Education, Inc.  Male Reproductive Structures  Male urethra – Used by urinary and reproductive systems – The tube for the external release of Urine and Semen – Extends from urinary bladder through the penis and all the way to tip of penis  Accessory glands: Generates the fluid composition of Semen – Focus Point – Sperm (AKA male gametes) is the cellular component of semen) Mixture of different secretions from different glands – Accessory glands include Seminal glands Prostate Bulbo-urethral glands © 2018 Pearson Education, Inc.  Male Reproductive Structures: Accessory Glands  Major functions of accessory glands – Activate sperm – Provide nutrients sperm need for motility – Propel sperm and fluids along reproductive tract via the Mainly by peristaltic contractions – Facilitate Ejaculation – Produce buffers To counteract acidity of urethral and vaginal environments – Basic functions of the Seminal Fluid Acts as a buffer to neutralize low pH due to urine Provides lubrication through the reproductive tract system Provides nutrients and protection for the Gametes (sperm) Activates the Sperm © 2018 Pearson Education, Inc.  Male Reproductive Structures – Accessory Glands  Seminal glands (seminal vesicles) – Paired Glands – 15 cm long with short side branches from body – First Accessory glands after testes: vas deferens connects the Seminal Gland to the testes – First Accessory gland to encounter immobile sperm storage in vas deferens – Extremely active secretory glands – Produce majority of seminal fluid volume – Alkaline (basic) pH which activates the Sperm (male gametes – Also provide nutrients to prolong the life of the male gametes  Ejaculatory duct – Short passageway (2 cm) Starts at junction of ampulla of ductus deferens and duct of seminal gland – Penetrates wall of prostate – Empties into prostatic urethra (Charging or EMISSION phase of Orgasm) © 2018 Pearson Education, Inc.  Male Reproductive Structures – Accessory Glands  Prostate – Small, muscular organ (about 4 cm in diameter) – Encircles the superior (top) portion of urethra Just interior to the urinary bladder – Consists of tubulo-alveolar glands – Surrounded by smooth muscle fibers which contracts during ejaculation to prevent urine from entering ejaculate  Prostatic fluid from Prostate Secretions – Slightly acidic which combines with and neutralizes the alkaline secretions from the seminal gland after the male gametes have been activated – Together these secretions preserve or prolong the life of the male gametes (sperm) – Forms about 25 percent of semen volume – Ejected into prostatic urethra By peristalsis of prostate wall  Prostatitis – Prostatic inflammation – While Can occur at any age : Most commonly afflicts older men – Also related to prostate cancer © 2018 Pearson Education, Inc.  Male Reproductive Structures – Accessory Glands  Bulbo-urethral glands (Cowper’s glands) – Compound, tubular mucous glands – Round, up to 10 mm in diameter – Located at base of penis – Secrete thick, alkaline mucus Helps neutralize urinary acids in urethra Lubricates tip of penis – Duct of each gland travels alongside spongy urethra and empties into urethral lumen © 2018 Pearson Education, Inc.  Figure 28–6a Anatomy of the Ductus Deferens and Accessory Glands. Ureter (Urine Only from Bladder) Urinary bladder Paired Ductus deferens (Stores Sperm cells only limited fluid) Paired Seminal gland Seminal Fluid secretions Ejaculatory duct Nutrients and sperm activation Charges Prosthetic Urethra with semen Prostate During EMISSION Seminal Fluid secretions pre-orgasm phase Smooth muscle contraction due to arousal during intercourse “pinching” to prevent urine from entering ejaculate Prosthetic Urethra Paired Bulbo-urethral glands (Portion of the urethra that extends through the prostate) – Important because this is how Urine Seminal Fluid Secretions can be pinched off so it does not enter semen that A) Neutralize urinary acids during ejaculations. This region gets charged in urethra & B) Lubricates which semen during the arousal phase of intercourse. Know as EMISSION Phase of ejaculation (orgasm) © 2018 Pearson Education, Inc.  Male Reproduction  Semen (aka the ejaculate) – Consists of – activated male gametes (AKA Sperm) and the seminal fluids secreted from the Seminal Glands, Prostate Glands and the Bulbo-urethral glands – Typical ejaculation releases 2–5 mL – Abnormally low volume may indicate problems With prostate or seminal glands – Sperm count Taken of semen collected after 36 hours of sexual abstinence Normal range is 20–100 million sperm/mL © 2018 Pearson Education, Inc.  Male Reproduction  Seminal fluid (Reminder – Semen is ejaculated into the vagina so some components of semen are associated with the fertilization process) High conc. of fructose to provide nutrients to sperm cells Prostaglandin hormones for smooth muscle contractions in male & female reproductive tracts (when ejaculated into vagina) Fibrinogen forms temporary semen clot in vagina (when ejaculated in vagina) – Secretions of seminal glands are slightly alkaline To neutralize acids in prostate and vagina – Semen also contains enzymes largely associated with allowing sperm to enter the ovum (female gametes) when ejaculated into the vagina – Enzymes Proteases (breaks down wall of ovum so sperm can enter and fertilize the ovum) Seminalplasmin (antibiotic protein) Fibrinolysin (to help form semen clot to facilitate fertilization) © 2018 Pearson Education, Inc.  Male Reproductive Structures  Penis – Tubular organ through which distal portion of urethra passes – Conducts urine to exterior – Introduces semen into female’s vagina  Root of penis – Fixed portion that attaches penis to body wall – Attachment occurs inferior to pubic symphysis  Body of penis (shaft) – Tubular, movable portion of penis  Glans penis (head) – Expanded distal end of penis that surrounds external urethral orifice © 2018 Pearson Education, Inc.  Figure 28–7a Anatomy of the Penis. Pubic symphysis Membranous urethra Bulb of penis Right crus Body of of penis penis Ramus of ischium Corpus spongiosum Neck of glans Corpora cavernosa Glans penis Scrotum External urethral orifice  Male Reproductive Structures  Erectile tissue – In body of penis – Located deep to areolar tissue – In dense network of elastic fibers That encircles internal structures of penis – Consists of network of vascular channels Incompletely separated by partitions of elastic connective tissue and smooth muscle fibers © 2018 Pearson Education, Inc.  Male Reproductive Structures  Erectile tissue – In resting state Arterial branches are constricted (preventing blood flow into the erectile tissue of the penis) Associated smooth muscle is tense – During erection Erection is a parasympathetic response to arousal Results in dilation of smooth muscle associated with the arterials that lead to the erectile tissue This allows for the flow of blood into the erectile tissue Penis stiffens and elevates to upright position for penetration into the vagina © 2018 Pearson Education, Inc.  Male Sexual Function  Autonomic nervous system – Controls male and female reproductive systems – Sexual intercourse Introduces semen into female reproductive tract  Male sexual function – Coordinated by complex neural reflexes Sympathetic and parasympathetic divisions of ANS – Male sexual arousal Increases parasympathetic outflow over pelvic nerves, leading to erection  Male sexual stimulation – Initiates secretion of bulbo-urethral glands Lubricates spongy urethra and surface of glands – Leads to emission and ejaculation) which is a sympathetic response © 2018 Pearson Education, Inc.  Male Sexual Function  Emission – Occurs under sympathetic stimulation – Peristaltic contractions of ampullae of ductus deferentia Push seminal fluid and sperm into prostatic urethra – Contractions in seminal glands and prostate Move seminal mixture along urethra and prevents urine from entering the ejaculate – Sympathetic contraction of urinary bladder and internal urethral sphincter Helps prevent urine from entering the ejaculate and Prevents passage of semen into bladder © 2018 Pearson Education, Inc.  Male Sexual Function  Ejaculation – Sympathetic Response – Occurs with powerful, rhythmic contractions in ischiocavernosus and bulbospongiosus skeletal muscle (somatic motor neurons – largely voluntary HOWEVER premature ejaculation can and does occur. Push semen toward external urethral opening – Causes pleasurable sensations (orgasm) – After orgasm, resolution phase occurs Heart rate and blood pressure decrease Blood begins to leave erectile tissue  Erectile dysfunction (ED) – Also called impotence – Inability to achieve or maintain an erection – Caused by physical or psychological factors © 2018 Pearson Education, Inc.  Figure 28–7b Anatomy of the Penis. The Urethra is divided into 3 sections depending on its position Ureter through the reproduction / urinary tract Prostatic Urethra Ductus deferens Proximal to the Bladder (most Seminal Opening of superior region just inferior to the gland ejaculatory duct Bladder passes through the Prostate prostate) – pinched to prevent Prostatic urethra urine in ejaculate Membranous Bulbo-urethral gland urethra Crus at root of penis Membranous Urethra Bulb of penis Region where Urethra passes Opening from through the pubic bone into the bulbo-urethral Erectile Tissue pelvic cavity gland Corpus spongiosum Corpora cavernosa Spongy Urethra Most distal to the Bladder (most Spongy urethra inferior region) passes through Glans penis Foreskin the penis and connects to the External urethral External Urethral Orifice orifice  Mitosis, Meiosis, and Spermatogenesis – Production of Gametes  There are TWO Types of Cell Division in Human – Mitosis Somatic cells – All cells other then the sex cells (AKA gametes) Diploid (a pair of chromosomes) 23 X 2 = 46 – Meiosis Only sex cells – (AKA Gametes) Haploid (chromosome not paired only 23 X 1 = 23 Two stage of Meiosis: – Meiosis I and Meiosis II © 2018 Pearson Education, Inc.  Mitosis, Meiosis, and a The fate of three homologous chromosome pairs during mitosis. Spermatogenesis – MITOSIS Parent cell (before chromosome replication) Production of Gametes Prophase Duplicated chromosome  Mitosis (two sister chromatids) 2n = 6 – Part of somatic cell Metaphase division (all cells but Chromosomes gametes) align at the metaphase plate – Produces two diploid (2n) daughter cells Anaphase Telophase Both have identical numbers and pairs of chromosomes Daughter cells Members of each pair of mitosis (2n) are homologous KEY Maternal chromosomes chromosomes Paternal chromosomes © 2018 Pearson Education, Inc.  Mitosis, Meiosis, and Spermatogenesis  Meiosis – Special form of cell division involved only in production of gametes Sperm in males Oocytes in females – Produces four haploid (n) gametes Each with 23 individual chromosomes At the end of complete meiosis there are 4 cells with only 23 chromosome in each cell – Sexual Fertilization is the fusion of Fusion of male and female gametes Produces zygote with 46 chromosomes (genetic variability with 23 chromosome coming from mom and 23 coming from dad) © 2018 Pearson Education, Inc.  b The fate of three homologus Meiosis I & II chromosome pairs during meiosis. Parent cell MEIOSIS I (before chromosome replication) Site of a Meiosis I crossing over Prophase I Chromosomes Tetrad formed replicate (4 of each by synapsis of chromosome) and 2n = 6 homologous chromosomes first division occurs (2 cells) with each Metaphase I cell having two of Tetrads align at each chromosome the metaphase plate Meiosis II Second division Homologous Anaphase I Telophase I occurs (4 cells) with chromosomes separate during each cell being anaphase I; sister haploid (only one chromatids chromosome) remain together Sister chromatids MEIOSIS II separate during anaphase II KEY Haploid Maternal chromosomes n=3 n n n n Paternal chromosomes Daughter cells (gametes) of meiosis  Mitosis, Meiosis, and Spermatogenesis  Spermatogenesis – Process of sperm production – Begins at puberty – Continues past age 70 – Complete process takes about 64 days – Involves three steps 1. Mitosis 2. Meiosis 3. Spermiogenesis © 2018 Pearson Education, Inc.  Mitosis, Meiosis, and Spermatogenesis  Spermatogenesis (production of sperm cells)  Result of Meiosis  Begins in testes – Production of immature gametes (spermatids)  Gametes mature and become motile and activate after immature gametes are released from the testes  Cells of spermatogenesis – Spermatogonia (sperm stem cells) Divide by mitosis to produce two daughter cells One remains a spermatogonium Second differentiates into primary spermatocyte – Primary spermatocytes Begin meiosis and form secondary spermatocytes – Secondary spermatocytes differentiate into spermatids – Spermatids Immature gametes Differentiate into sperm – Sperm Lose contact with wall of seminiferous tubule Enter fluid in lumen © 2018 Pearson Education, Inc.  Figure 28–9 The Process of Spermatogenesis Spermatogenesis Mitosis of spermatogonium (stem cell) Each division of a diploid spermatogonium produces two daughter cells. One is a spermatogonium that remains in contact with the basement membrane of the seminiferous tubule, and the other is a primary spermatocyte that moves toward the lumen. The primary spermactocytes will become the future male gamete (AKA sperm). These Primary events from spermatogonium to primary spermatocyte spermatocyte take 16 days. (diploid, 2n) Mitosis of Stem Cells © 2018 Pearson Education, Inc.  Figure 28–9 The Process of Spermatogenesis Spermatogenesis Meiosis I DNA replication As meiosis I begins, each primary spermatocyte contains 46 individual chromosomes. At the end of meiosis I, the Primary daughter cells are called secondary spermatocytes. spermatocyte Every secondary spermatocyte contains 23 chromosomes, each with a pair of duplicate chromatids. This phase of Synapsis and spermatogenesis takes about 24 days. tetrad formation Secondary spermatocytes Spermatogenesis Meiosis II Spermatids The secondary spermatocytes soon enter (haploid, n) meiosis II, which yields four haploid spermatids, each containing 23 chromosomes. For each primary spermatocyte that enters meiosis, four spermatids are produced. This phase lasts only a few hours. 40 © 2018 Pearson Education, Inc.  Figure 28–9 The Process of Spermatogenesis Spermatogenesis Spermiogenesis (physical maturation) In spermiogenesis, the last step of spermatogenesis, each spermatid matures Sperm into a single sperm. The process of (haploid, n) spermiogenesis—from spermatids to sperm—takes 24 days. Maturation is process that occurs in the Testes and in the Reproductive Tract – Secretions largely from the Seminal Gland (and from the prostate gland to a lesser degree) result in finally stages of maturation – become motile. The Tail is produced in the Testes but the sperm is not motile until it leaves the testes and enters the reproductive ducts 41 © 2018 Pearson Education, Inc.  Mitosis, Meiosis, and Spermatogenesis Spermatogonia Primary Secondary (daughter cell Spermatocytes Spermatocytes Testes) Testes Testes Meiosis I & II Spermatids (immature Spermatogonia Mitosis sperm in testes) (Stem cell Testes) Mature Sperm (but immotile) – Leaves testes Spermatogonia and stored in vas deferens (daughter cell) Sperm (mature, active, motile sperm) in Reproductive tract after Vas Deferens – (via Seminal Glands) © 2018 Pearson Education, Inc.  Mitosis, Meiosis, and Spermatid Nurse Dividing cell spermatocytes Capillary Spermatogenesis  Contents of seminiferous tubules in the Testes – Spermatogonia – Spermatocytes at various stages of Lumen meiosis – Spermatids – Sperm – Large nurse cells Spermatogonium Sperm Nurse cells surround the stem cells of the tubule and support the developing spermatocytes and spermatids. © 2018 Pearson Education, Inc.  Figure 28–11 Spermiogenesis & Anatomy of Sperm Spermatid (Has no tail) Spermiogenesis. The differentiation of a spermatid into a sperm. This process is Mature Sperm However not motile completed in approximately 24 days. until activated by the Seminal © 2018 Pearson Education, Inc. Glands (alkaline secretions)  Mitosis, Meiosis, and Spermatogenesis  Spermiogenesis – Last step of spermatogenesis – Each spermatid matures into one sperm with a tail – Involves major structural changes – At spermiation, a sperm is release from the nurse cells so it can enter the reproductive tract  Nurse cells (Sertoli cells) – Play a critical role in spermatogenesis Maintenance of blood testis barrier Support of mitosis and meiosis Support of spermiogenesis Secretion of inhibin Secretion of androgen-binding protein (ABP) © 2018 Pearson Education, Inc.  Mitosis, Meiosis, and Spermatogenesis  Blood testis barrier – Isolates seminiferous tubules from general circulation – Nurse cells maintain this barrier Joined by tight junctions that divide seminiferous tubule into compartments Outer basal compartment contains spermatogonia Inner luminal compartment is where meiosis and spermiogenesis occur Gonadotropin Hormones from anterior lobe of the pituitary gland enter the testes via the blood barrier © 2018 Pearson Education, Inc.  Mitosis, Meiosis, and Spermatogenesis  Support of mitosis and meiosis – Nurse cells are stimulated by Follicle-stimulating hormone (FSH) (Gonadotropin) Testosterone – Stimulated nurse cells promote Division of spermatogonia Meiotic divisions of spermatocytes  Support of spermiogenesis – Nurse cells Surround and enfold spermatids Provide nutrients and chemical stimuli for development Phagocytize cytoplasm shed by developing spermatids – Nurse cells are stimulate by hormones and release hormones when stimulated © 2018 Pearson Education, Inc.  Mitosis, Meiosis, and Spermatogenesis  Sperm leaving epididymis – Mature but immobile – To become motile (actively swimming) and fully functional Sperm must undergo capacitation  Two steps in capacitation 1. Sperm become motile When mixed with secretions of seminal glands Occurs in male reproductive tract 2. Sperm become capable of fertilization When exposed to female reproductive tract Occurs in female reproductive tract © 2018 Pearson Education, Inc.  Anatomy of Sperm – Head ; Neck ; Middle piece ; Tail – Head A flattened ellipse that contains nucleus with chromosomes (DNA) – Neck - Contains enzymes essential to fertilization – Middle piece Attached to head by short neck Contains mitochondria – In a spiral around microtubules which provides ATP to move tail – Tail The only flagellum in human body – Whiplike organelle – Moves cell from one place to another – Has complex, corkscrew motion © 2018 Pearson Education, Inc.  Hormonal Regulation of Reproduction  Hormones and male reproductive function  Gonadotropin-releasing hormone (GnRH) – Synthesized in hypothalamus Carried to pituitary by hypophyseal portal system – Controls rates of secretion of FSH and LH (From Pituitary gland) Testosterone (From Testes) (released in response to LH)  Luteinizing hormone (LH) – Targets interstitial endocrine cells of testes – Induces secretion of Testosterone  FSH and testosterone – Target nurse cells of seminiferous tubules – Nurse cells Secrete inhibin Secrete androgen-binding protein (ABP) Promote spermatogenesis and spermiogenesis © 2018 Pearson Education, Inc.  Hormonal Regulation of Reproduction  Nurse cells secrete inhibin (peptide hormone) – In response to factors released by sperm – Inhibin stops Pituitary production of FSH (Gonadotropin) – Regulation of FSH by inhibin (Gonadotropin) Allows negative feedback control of spermatogenesis – As rates of sperm production increase, secretion of inhibin increases  Nurse cells secrete androgen-binding protein (ABP) – Important for Elevating androgen concentration Stimulating spermiogenesis – Production of ABP is stimulated by FSH © 2018 Pearson Education, Inc.  Hormonal Regulation of Reproduction  Testosterone – Plays a major role in establishing male traits – Plays major role in maintaining male sexual function – Stimulates spermatogenesis – Maintains libido (sexual drive) and related behaviors (Male Traits) – Stimulates bone and muscle growth – Establishes and maintains male secondary sex characteristics (Male Traits) – Maintains accessory glands and organs of male reproductive system © 2018 Pearson Education, Inc.  Figure 18-9 Hypothalamus – Pituitary Regulation  Gonadotropin Hormones (FSH and LH) are release from anterior lobe and stimulate testes to release other hormones (Inhibin and Testosterone) © 2018 Pearson Education, Inc.