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Chapter 20 The Reproductive Systems

Chapter 20 The Reproductive Systems. COMMON STRUCTURAL AND FUNCTIONAL CHARACTERISTICS BETWEEN THE SEXES. Common general structure and function can be identified between the systems in both sexes

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Chapter 20 The Reproductive Systems

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  1. Chapter 20The Reproductive Systems

  2. COMMON STRUCTURAL AND FUNCTIONAL CHARACTERISTICS BETWEEN THE SEXES • Common general structure and function can be identified between the systems in both sexes • Systems adapted for development of sperm or ova followed by successful fertilization, development, and birth of offspring • Sex hormones in both genders important in development of secondary sexual characteristics and normal reproductive system activity

  3. MALE REPRODUCTIVE SYSTEM • Structural plan—organs classified as essential or accessory • Essential organs of reproduction are the gonads (testes), which produce sex cells (sperm or spermatozoa) • Accessory organs of reproduction • Ducts—passageways that carry sperm from testes to exterior • Sex glands—produce protective and nutrient solution for sperm • External genitals

  4. MALE REPRODUCTIVE SYSTEM • Testes—the gonads of men • Structure and location (Figure 20-2) • Testes in scrotum—lower temperature • Covered by tunica albuginea, which divides testis into lobules containing seminiferous tubules • Interstitial cells produce testosterone

  5. MALE REPRODUCTIVE SYSTEM • Testes (cont.) • Functions • Spermatogenesis is process of sperm production (Figure 20-4) • Sperm precursor cells called spermatogonia • Meiosis produces primary spermatocyte, which forms four spermatids with 23 chromosomes • Spermatozoa—highly specialized cells • Head contains genetic material • Acrosome contains enzymes to assist sperm in penetration of ovum • Mitochondria in midpiece provide energy for movement • Production of testosterone by interstitial cells • Testosterone “masculinizes” and promotes development of male accessory organs • Promotes and maintains development of male accessory organs • Stimulates protein anabolism and development of muscle strength

  6. MALE REPRODUCTIVE SYSTEM • Reproductive ducts—ducts through which sperm pass after exiting testes until they exit from the body • Epididymis—single, coiled tube about 6 m in length; lies along the top and behind the testis in the scrotum • Sperm mature and develop the capacity for motility as they pass through epididymis • Ductus (vas) deferens—receives sperm from the epididymis and transports them from scrotal sac through the abdominal cavity • Passes through inguinal canal • Joins duct of seminal vesicle to form the ejaculatory duct

  7. MALE REPRODUCTIVE SYSTEM • Accessory, or supportive, sex glands—semen: mixture of sperm and secretions of accessory sex glands; averages 3 to 5 mL per ejaculation, with each milliliter containing about 100 million sperm • Seminal vesicles • Pouchlike glands that produce about 60% of seminal fluid volume • Secretion is yellowish, thick, and rich in fructose to provide energy needed by sperm for motility • Prostate gland • Shaped like a doughnut and located below bladder • Urethra passes through the gland • Secretion represents 30% of seminal fluid volume—is thin and milk-colored • Activates sperm and is needed for ongoing sperm motility • Bulbourethral (Cowper’s) glands • Resemble peas in size and shape • Secrete mucus-like fluid constituting less than 5% of seminal fluid volume

  8. MALE REPRODUCTIVE SYSTEM • External genitals • Penis and scrotum called genitalia • Penis has three columns of erectile tissue—two dorsal columns called corpora cavernosa and one ventral column surrounding urethra called corpus spongiosum • Glans penis covered by foreskin (prepuce) • Surgical removal of foreskin called circumcision

  9. FEMALE REPRODUCTIVE SYSTEM • Structural plan—organs classified as essential or accessory • Essential organs are gonads (ovaries), which produce sex cells (ova) • Accessory organs of reproduction • Ducts or modified ducts—including oviducts, uterus, and vagina • Sex glands—including the breasts • External genitals

  10. FEMALE REPRODUCTIVE SYSTEM • Ovaries • Structure and location • Paired glands weighing about 3 g each • Resemble large almonds • Attached to ligaments in pelvic cavity on each side of uterus • Microscopic structure (Figure 20-8) • Ovarian follicles—contain an oocyte, which is an immature sex cell (about 1 million at birth) • Primary follicles—about 400,000 at puberty are covered with granulosa cells • About 350 to 500 mature follicles ovulate during the reproductive lifetime of most women—sometimes called graafian follicles • Secondary follicles have a hollow chamber called the antrum • Corpus luteum forms after ovulation

  11. FEMALE REPRODUCTIVE SYSTEM • Ovaries (cont.) • Functions • Oogenesis—this meiotic cell division produces daughter cells with equal chromosome numbers (23) but unequal cytoplasm; ovum is large; polar bodies are small and degenerate • Production of estrogen and progesterone • Granulosa cells surrounding the oocyte in the mature and growing follicles produce estrogen • Corpus luteum produces progesterone • Estrogen causes development and maintenance of secondary sex characteristics • Progesterone stimulates secretory activity of uterine epithelium and assists estrogen in initiating menses

  12. FEMALE REPRODUCTIVE SYSTEM • Reproductive ducts • Uterine (fallopian) tubes (oviducts) • Extend about 10 cm from uterus into abdominal cavity • Expanded distal end surrounded by fimbriae • Mucosal lining of tube is directly continuous with lining of abdominal cavity • Uterus—composed of body, fundus, and cervix (Figure 20-9) • Lies in pelvic cavity just behind urinary bladder • Myometrium is muscle layer • Endometrium lost in menstruation • Menopause—end of repetitive menstrual cycles (about 45-50 years of age) • Vagina • Distensible tube about 10 cm long • Located between urinary bladder and rectum in the pelvis • Receives penis during sexual intercourse and is birth canal for normal delivery of baby at end of term of pregnancy • Accessory or supportive sex glands

  13. FEMALE REPRODUCTIVE SYSTEM • Accessory, or supportive, sex glands • Bartholin’s (greater vestibular) glands • Secrete mucus-like lubricating fluid • Ducts open between labia minora • Breasts (Figure 20-10) • Located over pectoral muscles of thorax • Size determined by fat quantity more than amount of glandular (milk-secreting) tissue • Lactiferous ducts drain at nipple, which is surrounded by pigmented areola • Lymphatic drainage important in spread of cancer cells to other body areas

  14. FEMALE REPRODUCTIVE SYSTEM • External genitals (Figure 20-11) • Vulva includes mons pubis, clitoris, orifice of urethra, Bartholin’s gland, vagina, labia minora and majora, and hymen • Perineum—area between vaginal opening and anus • Surgical cut during childbirth called episiotomy

  15. FEMALE REPRODUCTIVE SYSTEM • Menstrual cycle—involves many changes in the uterus, ovaries, vagina, and breasts (Figures 20-12 and 20-13) • Length—about 28 days, varies from month to month among individuals and in the same individual • Phases • Menses—about the first 4 or 5 days of the cycle, varies somewhat; characterized by sloughing of bits of endometrium (uterine lining) with bleeding • Proliferative phase—days between the end of menses and secretory phase; varies in length; the shorter the cycle, the shorter the proliferative phase; the longer the cycle, the longer the proliferative phase • Secretory phase—days between ovulation and beginning of next menses; secretory about 14 days before next menses; characterized by further thickening of endometrium and secretion by its glands in preparation for implantation of fertilized ovum; combined actions of the anterior pituitary hormones FSH and LH cause ovulation; sudden sharp decrease in estrogens and progesterone bring on menstruation if pregnancy does not occur

  16. SUMMARY OF MALE AND FEMALE REPRODUCTIVE SYSTEMS • In men and women the organs of the reproductive system are adapted for the specific sequence of functions that permit development of sperm or ova after the successful fertilization and then the normal development and birth of offspring • The male organs produce, store, and ultimately introduce mature sperm into the female reproductive tract

  17. SUMMARY OF MALE AND FEMALE REPRODUCTIVE SYSTEMS • The female system produces ova, receives the sperm, and permits fertilization followed by fetal development and birth, with lactation afterward • Production of sex hormones is required for development of secondary sex characteristics and for normal reproductive functions in both sexes

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