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Chapter 19 THE REPRODUCTIVE SYSTEM Introduction • Reproduction: process by which genetic material is passed from one generation to the next Introduction (cont’d.) • Meiosis produces sex cells – Sperm from male and egg from female join to form zygote – Zygote develops into embryo – Embryo develops into fetus THE MALE REPRODUCTIVE SYSTEM Introduction • Testes: produce sperm and male sex hormones • Accessory glands: produce secretions • Accessory organs: scrotum • Penis: transporting and supporting structure Introduction (cont’d.) The Scrotum • • • • Outpouching of abdominal wall Supports the testes Divided internally by a septum Scrotal sac elevates and descends The Testes • Tunica albuginea: capsule covering with lobules • Convoluted seminiferous tubules – Spermatogenesis The Testes (cont’d.) • Spermatogenesis – Spermatogonia > primary spermatocytes > secondary spermatocytes > spermatids > spermatozoa • Sertoli cells: supply sperm cells with nutrients The Testes (cont’d.) • Interstitial cells of Leydig: produce testosterone The Testes (cont’d.) The Anatomy of the Spermatozoa • Three hundred million produced daily • Anatomy – Head: contains genetic material and acrosome • Acrosome has enzymes that aid sperm in penetrating covering of ovum – Middle piece: contains mitochondria – Tail: propels sperm The Anatomy of the Spermatozoa (cont’d.) • Anatomy of a sperm cell The Functions of Testosterone • Controls development, growth, and maintenance of male sex organs • Stimulates muscle buildup and bone development • Causes sperm maturation • Causes thyroid cartilage enlargement • Produces body hair patterns The Ducts of the System • Seminiferous tubules: transport sperm cells • Rete testis: network of ducts • Ductus epididymis: site of sperm cell maturation • Epididymis located on posterior border of testis The Ducts of the System (cont’d.) • Vas deferens: straightened portion of epididymis – Enclosed in spermatic duct • Ejaculatory duct: ejects spermatozoa into urethra The Ducts of the System (cont’d.) • Urethra: terminal duct – Prostatic urethra, cavernous urethra, urethral orifice The Accessory Glands • Seminal vesicles: produce viscous part of semen • Prostate gland: produces fluid part of semen • Bulbourethral glands: produce mucus Semen • • • • • • • Mixture of sperm cells and secretions Provides energy to the sperm via fructose Neutralizes acidity of vagina Acts as a transport medium Contains enzymes that activate sperm Average volume is 2.5 to 6 mL Seminalplasmin: destroys certain bacteria The Penis • Delivers spermatozoa to female reproductive tract • Glans penis: end of the shaft • Prepuce: loose skin covering glans penis – Circumcision: removal of prepuce The Penis (cont’d.) • Contains masses of spongy tissue with sinuses • Sinuses fill with blood resulting in erection – Compress veins so blood is retained – Help penis penetrate vagina • During ejaculation, sphincter at base of urinary bladder is closed THE FEMALE REPRODUCTIVE SYSTEM Introduction • Primary sex organs – Ovaries • Accessory organs – Uterine tubes, uterus, vagina, external genitalia • Accessory glands: produce mucus Introduction (cont’d.) The Ovaries • Held in position by ligaments • Covered by germinal epithelium • Tunica albuginea: cortex contains ovarian follicles • Ovarian follicles: eggs in various developmental stages • Primary follicle: contains oocyte The Ovaries (cont’d.) The Ovaries (cont’d.) • Oogenesis – Begins in developing female fetus (700,000 produced) – Puberty: ovarian cycle begins • Primary oocyte: first meiotic division • Mature egg: second meiotic division The Uterine or Fallopian Tubes • Transport ova to the uterus • Infundibulum: funnel-shaped end with fimbriae • Cilia sweep an ovum into uterine tube • Egg moved by peristalsis toward uterus • Fertilization occurs in upper third of tube The Uterus • Site of menstruation, egg implantation and labor • Pear shaped • Uterine cavity: interior of the body • Cervical canal: interior of the cervix • Uterine wall: endometrium, myometrium, perimetrium The Menstrual Cycle • Menstrual phase – Endometrial lining shed along with blood and mucus – Ovarian follicles begin development • Preovulatory or proliferative phase – Secondary follicle matures into graafian follicle – Ovulation is rupturing of graafian follicle The Menstrual Cycle (cont’d.) • Postovulatory or secretory phase – Corpus luteum develops • Secretes estrogen and progesterone – If fertilization and implantation do not occur • Corpus luteum degenerates and new cycle starts – If fertilization and implantation occur • Corpus luteum maintained for four months Animation – Ovulation Click Here to Play Ovulation Animation The Functions of Estrogen • Development of female secondary sex characteristics – Breast development, pubic hair, fat deposits, widening of the pelvic bone • Enlargement of: – Uterine tubes, uterus, vagina, external genitalia The Vagina • • • • Passageway for menstrual flow Receptacle for the penis Lower portion of birth canal Fornix: surrounds vaginal attachment to cervix The External Genitalia of the Female • • • • • Vulva: external genitalia Labia: majora and minora Clitoris: erectile tissue Vestibule: vaginal and urethral orifices Glands: Skene’s and Bartholin’s The External Genitalia of the Female (cont’d.) THE PERINEUM The Perineum (cont’d.) • Diamond-shaped region at inferior end of trunk between buttocks and thighs • Divided into: – Anterior urogenital triangle containing external genitalia – Posterior anal triangle containing anus THE ANATOMY AND FUNCTION OF THE MAMMARY GLANDS The Anatomy and Function of the Mammary Glands (cont’d.) • • • • • Produce milk in females Contain 15 to 20 lobes with lobules Lobules contain milk-secreting cells Milk is conveyed through series of tubules Areola: circular pigmented area around nipple The Anatomy and Function of the Mammary Glands (cont’d.) PREGNANCY AND EMBRYONIC DEVELOPMENT Pregnancy and Embryonic Development (cont’d.) • Egg fertilization 12-24 hours after ovulation • Zygote: fertilized egg • Moves down uterine tube into uterus – Blastula • Zygote embeds in endometrium, placenta develops Pregnancy and Embryonic Development (cont’d.) • Primary germ layers – Ectoderm: skin and nervous system – Mesoderm: muscles and bones – Endoderm: linings of organs and glands • Amnion: fluid-filled sac – Attached to embryo by umbilical cord • Parturition: childbirth Summary • Discussed the organs of the male reproductive system • Discussed the role of testosterone • Described the process of spermatogenesis • Discussed the organs of the female reproductive system Summary (cont’d.) • Discussed the role of estrogen • Described the process of oogenesis • Described the phases of the menstrual cycle • Discussed pregnancy and embryonic development