reproductive system

• Gonads (testes)


  Produce sperm and secrete hormones
• Anatomy of male reproductive system

  1. Gonads (testes)

  2. System of ducts (ductus, epididymis, ductus deferens, ejaculatory duct, urethra)

  3. Accessory sex glands (seminal vesicles, prostate gland, bulbourethral glands)

  4. Supporting structures (Scrotum, Penis)
• Scrotum


  • Cutaneous outpouching of the abdomen that supports the testes
  • Normal sperm production and survival requires a temperature 2-3°C below core body temperature
• Testes or testicles


  • Paired oval glands that descend from the abdomen to the scrotum during the 7th month of fetal development
  • Covered by a fibrous tissue called tunica albuginea
  • Invaginations form 200 - 300 compartments called lobules
  • Each lobule is filled with 2 or 3 seminiferous tubules (Spermatogenesis)
• Leydig cells


  Interstitial endocrinocytes found in the spaces between adjacent seminiferous tubules that secrete the male hormone testosterone
• Sertoli cells


  • Form blood testes barrier
  • Nourish spermatocytes
  • Mediate the effects of testosterone and FSH on spermatogenesis
  • Phagocytose excess spermatids
  • Secrete the hormone inhibin which helps regulate sperm production by inhibiting production of FSH
• Spermatogenesis


  1. Spermatogenesis produces haploid sperm (n) (one set of 23 chromosomes) from diploid spermatogonia (2n)

  2. Meiosis I - Reduction division, homologous pairs line up to form a tetrad

  3. Meiosis II - Equatorial division, 2 chromatids separate

  4. Results in 4 Spermatids - each is haploid and unique, 50% X chromosome, 50% Y chromosome

  5. Spermiogenesis - development of spermatids into sperm, acrosome and flagella form, mitochondria multiply

  6. Spermiation - release from connections to Sertoli cells
• Sperm Morphology


  • Head contains DNA (23 chromosomes) and acrosome
  • Acrosome contains enzymes that help sperm penetrate secondary oocyte (hyaluronidase and proteinase)
  • Midpiece contains mitochondria to form ATP
  • Produced at the rate of about 300 million/day
  • Life expectancy of 48 hours in the female reproductive tract
• Reproductive system ducts in males

  1. Ducts of testis - efferent ducts that empty into epididymis

  2. Epididymis - site of sperm maturation and storage

  3. Ductus (vas) deferens - conveys sperm during sexual arousal through peristaltic contractions

  4. Spermatic cord - ductus deferens ascends out of the scrotum with arteries/veins, autonomic nerves, lymphatic vessels, and cremaster muscle

  5. Ejaculatory ducts - formed by union of ducts from seminal vesicle and ductus deferens, terminating in the prostatic urethra

  6. Urethra - shared terminal duct of reproductive and urinary systems, subdivided into prostatic urethra, membranous urethra, spongy (penile) urethra
• Accessory Sex Glands


  • Seminal Vesicles (60% of semen volume) - viscous alkaline fluid that helps neutralise acid environment, contains fructose for ATP production by sperm and prostaglandins contribute to sperm motility and viability
  • Prostate Gland (25% of semen volume) - single donut shaped gland that secretes milky, slightly acidic fluid containing citric acid, proteolytic enzymes, PSA, seminalplasmin
  • Paired Bulbourethral (Cowper's) glands - secrete alkaline fluid that protects passing sperm by neutralizing acids from urine in urethra, mucus lubricates end of penis and lining of urethra
• Penis


  • Passageway for the ejaculation of semen
  • Body composed of three erectile tissue masses filled with blood sinuses surrounded by smooth muscle and elastic connective tissue
  • Erection - parasympathetic fibers release/cause local production of nitric oxide (NO) which dilates arterial smooth muscle, large amounts of blood enter blood sinuses, compresses veins draining the penis
• You should now be familiar with the male reproductive anatomy and physiology, and the process of spermatogenesis
• Female Reproductive System


  • Gonads (ovaries) - produce secondary oocytes and hormones
  • Uterine (fallopian) tubes or oviducts - transport fertilised ova
  • Uterus - where fetal development occurs
  • Vagina
  • External organs - vulva or pudendum
  • Mammary glands - produce milk
• Ovaries


  • Paired glands homologous to the testes
  • Produce gametes - secondary oocytes that develop into mature ova (eggs) after fertilization
  • Produce hormones including progesterone, estrogens, inhibin and relaxin
• Ovarian ligaments


  • Broad ligament - a fold of parietal peritoneum
  • Ovarian ligament - anchors ovaries to uterus
  • Suspensory ligament - attaches ovaries to pelvic wall
• Histology of ovary


  • Germinal epithelium - covers surface of ovary
  • Tunica albuginea - located underneath epithelium
  • Ovarian cortex - contains ovarian follicles and stromal cells
  • Ovarian medulla - contains blood vessels, lymphatic vessels, and nerves
• Ovarian follicles


  • In cortex and consist of oocytes in various stages of development
  • Mature (graafian) follicle - large, fluid-filled follicle ready to expel secondary oocyte during ovulation
  • Corpus luteum - remnants of mature follicle after ovulation
• During early fetal development, primordial (primitive) germ cells migrate from yolk sac to ovaries and differentiate into oogonia - diploid (2n) stem cells
• Before birth, most germ cells have undergone meiosis I, resulting in the formation of a single haploid secondary oocyte
• Ovaries


  Include progesterone, estrogens, inhibin and relaxin
• Ovarian ligaments


  • Series of ligaments hold ovaries in place
  • Broad ligament - a fold of parietal peritoneum
  • Ovarian ligament - anchors ovaries to uterus
  • Suspensory ligament - attaches ovaries to pelvic wall
• Histology of ovary


  • Germinal epithelium - covers surface of ovary
  • Tunica albuginea - located underneath epithelium
  • Ovarian cortex - contains ovarian follicles and stromal cells
  • Ovarian medulla - contains blood vessels, lymphatic vessels, and nerves
• Ovarian follicles


  • In cortex and consist of oocytes in various stages of development
  • Mature (graafian) follicle - large, fluid-filled follicle ready to expel secondary oocyte during ovulation
  • Corpus luteum - remnants of mature follicle after ovulation
• Oogenesis and follicular development

  1. During early fetal development, primordial (primitive) germ cells migrate from yolk sac to ovaries

  2. Differentiate into oogonia - diploid (2n) stem cells

  3. Before birth, most germ cells degenerate - atresia

  4. A few develop into primary oocytes that enter meiosis I during fetal development

  5. Each covered by single layer of flat follicular cells - primordial follicle

  6. About 200,000 to 2,000,000 at birth in each ovary, 40,000 remain at puberty, and around 400 will mature and ovulate during a lifetime
• Follicular development


  1. Each month from puberty to menopause, FSH and LH stimulate the development of several primordial follicles (one reaches ovulation)

  2. Just before ovulation, diploid primary oocyte completes meiosis I

  3. Produces 2 unequal sized haploid (n) cells - secondary oocyte and first polar body (discarded)

  4. Once secondary oocyte is formed it begins meiosis II but stops at metaphase

  5. At ovulation, secondary oocyte expelled with first polar body

  6. If fertilisation does not occur, cells degenerate

  7. If a sperm penetrates secondary oocyte, meiosis II resumes

  8. Secondary oocyte splits into 2 cells of unequal size - second polar body (discarded) and ovum or mature egg

  9. Nuclei of sperm cell and ovum unite to form diploid zygote - fertilisation
• Uterine (fallopian) tubes or oviducts

  • Provide a route for sperm to reach an ovum
  • Site of fertilisation
  • Transport secondary oocytes and fertilised ova from ovaries to uterus
  • Infundibulum ends in finger-like fimbriae
  • Produce currents to sweep secondary oocyte into tube
  • Ampulla - widest longest portion
  • Isthmus - joins uterus
  • Three layers: 1) Mucosa - ciliary conveyor belt, peg cells provide nutrition to ovum, 2) Muscularis - peristaltic contractions, 3) Serosa - outer layer
• Uterus (womb)


  • Functions - the transport of spermatozoa, menstruation, implantation of fertilised ovum, development of foetus during pregnancy and labour
  • Anatomically - can be subdivided into: Fundus, Body, Isthmus, Cervix (opens into vagina)
• Histology of the uterus

  • Perimetrium - outer layer
  • Myometrium - 3 layers of smooth muscle, contractions in response to oxytocin from posterior pituitary
  • Endometrium - inner layer, highly vascularized, Stratum functionalis - lines cavity, sloughs off during menstruation, Stratum basalis - permanent, gives rise to new stratum functionalis after each menstruation
• Blood supply of the uterus

  • Uterine arteries branch as arcuate arteries and radial arteries that supply the myometrium
  • Straight & spiral branches penetrate to the endometrium
  • Spiral arteries supply the stratum functionalis
  • Their constriction due to hormonal changes starts menstrual cycle
• Cervical mucus


  • A mixture of water, glycoprotein, serum-type proteins, lipids, enzymes, and inorganic salts
  • When thin, is more receptive to sperm
  • When thick, forms a cervical plug that physically impedes sperm penetration
  • Mucus supplements the energy needs of the sperm
  • The cervix and the mucus also play a role in capacitation - renders them competent to fertilise an oocyte
• Vagina


  • Fibromuscular canal extending from exterior of body to uterine cervix
  • Mucosa continuous with uterine mucosa
  • Decomposition of glycogen makes acidic environment hostile to microbes and sperm
  • Alkaline components of semen raise pH
  • Functions as a passageway for spermatozoa and the menstrual flow, the receptacle of the penis during sexual intercourse, and the lower portion of the birth canal
  • 4 inch long fibromuscular organ ending at cervix
  • Mucosal layer, muscularis layer is smooth muscle allows considerable stretch, adventitia is loose connective tissue that binds it to other organs
• Vulva or pudendum - external female genitalia

  • Mons pubis - fatty pad cushions pubic symphysis
  • Labia majora - homologous to scrotum
  • Labia minora - homologous to spongy (penile) urethra
  • Clitoris - small mass of erectile tissue and numerous nerves/blood vessels, homologous to glans penis
  • Vestibule - region between labia minora
  • Bulb of the vestibule - 2 elongated masses of erectile tissue on either side of vaginal orifice
• Perineum


  • Diamond-shaped area medial to thighs and buttocks of males and females
  • Contains external genitalia and anus
  • During childbirth the emerging fetus may cause excessive stretching and tearing of the perineum
  • A physician may make a surgical incision (episiotomy) in this region to prevent excessive, jagged tears
• Mammary glands


  • Modified sudoriferous (sweat) glands that produce milk (lactation)
  • 15-20 lobes divided into lobules composed of alveoli (milk-secreting glands)
  • Milk secreting glands open by lactiferous ducts at the nipple
  • Areola - pigmented area around nipple
• The Female Reproductive Cycle

  • Encompasses ovarian and uterine cycle, hormonal changes that regulate them, and related changes in breast and cervix
  • Controlled by monthly hormone cycle of anterior pituitary, hypothalamus and ovary
  • Ovarian cycle - changes in ovaries that occur during and after maturation of oocyte
  • Uterine (menstrual) cycle - concurrent series of changes in uterine endometrium preparing it for arrival of fertilized ovum
  • If implantation does not occur the stratum functionalis is shed during menstruation