Male Reproductive System PDF

RNB 10702 ANATOMY AND PHYSIOLOGY 2 The Male Reproductive System  Learning Outcomes At the end of the session, the students should be able to: describe the anatomy and functions of the organs in the male reproductive system explain the process of ejaculation explain the roles of...

RNB 10702 ANATOMY AND PHYSIOLOGY 2 The Male Reproductive System  Learning Outcomes At the end of the session, the students should be able to: describe the anatomy and functions of the organs in the male reproductive system explain the process of ejaculation explain the roles of hormone in regulating male reproductive functions list the main changes occurring at puberty in the male  Introduction Sexual reproduction is a process in which organisms produce offspring by means of germ cells called gametes The organs of reproduction are grouped as gonads (produce gametes and secrete hormones)  ducts (transport, receive, and store gametes) accessory sex glands (produce materials that support gametes)  Introduction…cont Male reproductive organs secrete androgen hormones, produce gametes (sperm), and facilitate fertilization Urology is the study of the urinary system includes diagnosis and treatment of diseases and disorders of the male reproductive system Andrology is the study of only male reproductive diseases  Anatomy of Male Reproductive The male reproductive system contains of: The gonads The male gonads - testes It is the site for gamete & hormone production System of ducts Epididymis, ductus deferens, ejaculatory duct & urethra Function - store & transport gametes Supporting structures  The scrotum & the penis Function - deliver and/or assist in joining gametes  Anatomy of Male Reproductive…cont Accessory sex glands Seminal vesicles, prostate gland, bulbourethral glands Functions - produce secretions to protect and support the gametes  Scrotum Consists of skin & subcutaneous tissue Function - regulates the temperature of the testes that required for sperm production Dartos muscle – in cold temperature the muscle contract & give the skin of scrotum firm & wrinkle appearance & reduce size Cremaster muscles – skeletal muscle fibres that control the position of the scrotum & testes – contract to pull the testes closer to the body for warmth  Testes Are paired oval-shaped male gonads in the scrotum It is the reproductive glands of the male & equivalent to ovaries in female Begin development on the embryo’s abdominal cavity Last 2 months before birth or shortly after birth - descent into the scrotum  Testes…cont Structure Each testes is about 5cm long & 3cm in diameter Contain about 200 - 300 lobules in each testes Each lobule contain 1-4 convoluted loops called seminiferous tubules Between the tubules contain leydig cells that secrete testosterone after puberty Sertoli cells in seminiferous tubules support, protect & nourish sperm cells & produce inhibin  Testes…cont Structure…cont Seminiferous tubules converge to form a single straight tubule The straight tubule lead into the rete testes (tubular network) Leave the scrotum as the deferent duct (vas deferens) in the spermatic cord Tunica albuginea – white fibrous connective tissue surrounds each testes  Testes…cont Function Seminiferous tubules produce sperm (spermatozoa) through spermatogenesis – begin at puberty till old age under influence of testosterone Successful spermatogenesis take place at temperature 3°C below normal body temperature  Testes…cont Androgen – hormone that promotes the development of masculine characteristic  Testes (clinical application) Cryptorchidism – condition which the testes do not descend into the scrotum 80% will descend spontaneously during the first year of life Untreated bilateral cryptorchidism cause sterility due to high temperature in pelvic cavity  Spermatogenesis It is process where seminiferous tubules of the testes produce spermatozoa Takes 65-75 days In early embryonic development, primordial germ cells enter the testes & differentiate into spermatogonia Spermatogonia - immature cells until puberty  At puberty, they undergo mitosis to become primary spermatocytes  Spermatogenesis…cont Meiosis I – primary spermatocytes divides to become secondary spermatocytes Meiosis II – secondary spermatocytes divides to become spermatids Spermiogenesis - is the maturation of the spermatids into spermatozoa Spermatogenesis…cont  Sperm Seminiferous tubules produced sperm about 300 million/day Begin production at puberty & continue through-out the life of male Mature as they pass through the long & convoluted ductus epididymis where the stored Live about 48 hours in the female reproductive tract  Sperm…cont Mature sperm consist of a head, midpiece, and tail Head - contains nuclear material (DNA) Acrosome – covered the tip of head filled with enzymes that help a sperm to penetrate a secondary oocyte for fertilization The middle piece contains many mitochondria which provide the energy (ATP) for locomotion Tail – involved in locomotion  System of Ducts Consists of: Epididymis, ductus deferens, ejaculatory duct & urethra Function - transport, receive, and store gametes  System of ducts…cont Epididymis Located along the superior & posterior margins of the testes It is long(6m) tube that is tightly coiled ductus epididymis Ductus epididymis - site of sperm maturation Help to propel sperm into vas deferense during ejaculation Store sperm for several months  System of ducts…cont Ductus Deferens or Vas deferens Continuous with epididymis & extends to ejaculatory duct posterior to the urinary bladder Store sperm up to 7 months Propel sperm towards urethra during ejaculation by peristaltic contraction Spermatic cord – the proximal portion of the duct deferens  System of ducts…cont Ejaculatory duct Formed by the union of the duct from ductus deferens & seminal vesicle Each ejaculatory duct passes through the prostate gland & empties into the urethra Function – eject spermatozoa into the prostatic urethra  System of ducts…cont Urethra Extends from urinary bladder to the external urethral orifice at the tip of penis Shared pathway for urine flow & sperm The urethra pass through the prostate, deep perineal muscles & penis Sphinter contract tightly to prevent urine entering the urethra External urethral orifice - the opening of urethra to exterior  System of ducts (clinical application) Vasectomy is a method of sterilization of males in which both ductus deferens are cut and tied Results in no sperm entered during ejaculation  Accessory Sex glands Consists of Seminal vesicles Prostate gland Bulbourethral gland Functions - produce secretions to protect and support the gametes  Accessory sex glands…cont Seminal vesicles Secrete an alkaline, viscous fluid that contains; Fructose – provide energy for the spermatozoa Prostaglandins - contribute to sperm motility and viability Clotting proteins - helps semen coagulate after ejaculation The alkaline nature of the fluid helps to neutralize acid in the male urethra and female reproductive tract Secreted about 60% of the volume of semen Contract & expel seminal fluid during ejaculation  Accessory sex glands…cont Prostate gland Secrete a thin milky fluid that make up 30 % of semen – enhance the motility of the sperm Contain clotting enzyme which thicken the semen Bulbourethral glands Secrete alkaline substance to protect sperm by neutralizing acids from urine in the urethra Secrete mucus to lubricate penis to prevent sperm damage during ejaculation  Semen (seminal fluid) Mixture of sperm and seminal fluid – make up of 60% of the volume of the semen Typical volume 2.5-5 mL with 50-150 million sperm/mL Slightly alkaline pH of 7.2-7.7 due to seminal vesicle secretions Coagulates after ejaculation due to clotting proteins If < 20 million per ml – the man is infertile Contains an antibiotic to destroy certain bacteria Once ejaculated, liquid semen coagulates within 5 minutes due to the presence of clotting proteins from the seminal vesicles  Penis Located anterior to the scrotum Has a root, body, and glans penis Consists of eractile tissue (corpus carvenosa & corpus spongiosum) Function – transfer sperma into the vagina Prepuce or foreskin – covers the glans penis  Penis (clinical connection) A circumcision is a surgical procedure that removes the foreskin (the loose tissue) covering the glans for either religious or hygienic reasons Benefit – lower risk of UTI, protect against penile cancer, lower risk sexual transmitted disease  Ejaculation Ejaculation & propulsion of semen from the urethra to the exterior, is a sympathetic reflex coordinated by lumbar portion of spinal cord Erection - expansion of its blood sinuses under the influence of sexual excitation The semen is propelled by contraction of smooth muscle in the wall of deferent duct, seminal vesicles & prostate gland  Ejaculation…cont Before ejaculation occur, peristaltic contractions cause semen propel into penile portion in the urethra – lead to emmision (discharge small amount of semen before ejaculation-may occur at night) Muscle sphincter at base of bladder closed to prevent expel of urine during ejaculation & semen does not enter the urinary bladder Sperm only comprise 10% of the final ejaculated , the reminder are seminal & prostatic fluids  Ejaculation…cont Before ejaculation, sperm travel via the following route: Seminiferous tubules → Rete testis (network) → Efferent ducts → Ductus epididymis → Vas (ductus) → deferens Ejaculatory duct (within the prostate gland) → urethra portions (prostatic, membranous & penile) Arrow show the routes taken by sperm during ejaculation  Ejaculation (clinical application) Premature ejaculation results from anxiety, other psychological factors and an over sensitive glans Erectile dysfunction (ED), previously termed impotence, is the consistent inability of an adult male to ejaculate or to attain or hold an erection long enough for sexual intercourse due to insufficient release of nitric oxide  Hormonal Control At puberty, gonadotropin releasing hormone stimulates anterior pituitary secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) FSH - initiates spermatogenesis LH assists spermatogenesis and stimulates production of testosterone  Hormonal control…cont Function of testosterone controls the growth, development, functioning, and maintenance of sex organs stimulates bone growth, protein anabolism, and sperm maturation stimulates development of male secondary sex characteristics. Negative feedback systems regulate testosterone Inhibin is produced by Sertoli cells Inhibition of FSH by inhibin helps to regulate the rate of spermatogenesis Negative feedback systems regulate testosterone production  Puberty in Male Occurs between the age 10 to 14 years old Changes occur in puberty Growth of muscle & bone and increases in weight & height Enlargement in larynx & deepening of the voice Growth of hair on the face, axillae, chest, abdomen & pubis Enlargement of scrotum, penis & prostate gland Maturation of the seminiferous tubules & production of sperm The skin thickens & becomes oilier  Summary functions of the male reproductive system The testes produce sperm & male sex hormone testosterone The ducts transport, store & assist in the maturation of sperm The accessory sex glands secrete most of the liquid portion of semen The penis contains urethra, a passageway for ejaculation of semen & excretion of urine  Recap Testes is the primary reproductive organ in male In early development, testes is located in abdominal cavity & located in the scrotum at birth The main function of scrotum is to regulates the temperature of the testes Seminiferous tubules produce sperm through spermatogenesis The leydig cells secrete testosterone Cryptorchidism is the condition which the testes do not descend into the scrotum  recap…cont The head of mature spermatozoa contain DNA Luteinizing hormone (LH) stimulates the production of testosterone The sperm matured in ductus epididymis Seminal vesicle is the accessory gland that makes the largest contribution to the seminal fluid Enlargement in larynx & deepening of the voice occurs after puberty