Reproductive System

• Processes of the Reproductive System

  • Production of gametes
  • Fertilization
  • Development and nourishment of an individual
  • Production of reproductive hormones
• Formation of Gametes


  1. Meiosis

  2. One cell undergoes two consecutive cell divisions to produce four daughter cells, each having half as many chromosomes as the parent cell

  3. Meiosis I

  4. Meiosis II
• Male Reproductive Organs


  • Testes
  • Epididymis
  • Vas Deferens
  • Urethra
  • Seminal Vesicles
  • Prostate Gland
  • Bulbourethral Gland
  • Scrotum
  • Penis
• Penis


  • Contains three columns of erectile tissues: Pair of Corpora Cavernosa in the dorsal area, Corpus Spongiosum in the ventral area
  • Engorgement of erectile tissue with blood causes the penis to enlarge and become firm, a process called ERECTION
• Penis


  • The corpus spongiosum expands over the distal end of the penis to form a cap, the GLANS PENIS
• Scrotum


  • A saclike structure containing the testes
• Scrotum


  • Smooth muscles contract in cold temperature, relax in hot temperature
• Dartos Muscle Contraction


  Skin of the scrotum becomes firm and wrinkled, reducing the overall size of the scrotum
• Cremaster Muscle Contraction


  Pulls the scrotum near the body
• Testes


  • Male gonads ("seed")
  • Oval organs, each about 4–5 cm long, within the scrotum
  • Outer part consists of a thick, white connective tissue capsule
  • Extensions of the capsule project into the interior and divide each testis into about 250 cone-shaped lobules
  • Lobules contain seminiferous tubules, the site of sperm cell development
• Spermatogenesis


  The formation of sperm cells
• Interstitial Cells (Leydig Cells)

  • Clusters of endocrine cells which secrete testosterone
• Epididymis


  • Comma-shaped structure on the posterior side of the testis
  • Sperm cells continue to mature, developing the capacity to swim and the ability to bind to the oocyte
• Vas Deferens


  • Also known as "Ductus Deferens"
  • Emerges from the epididymis and ascends along the posterior side of the testes to become associated with the blood vessels and nerves that supply the testis
• Seminal Vesicle


  • Two small glands that store and produce the majority of the fluid that makes up semen
• Ejaculatory Duct


  • During ejaculation, the fluid from the seminal vesicles is expelled into the ejaculatory duct where it can then move on to mix with sperm and other reproductive fluids
• Prostate Gland


  • Surrounds the urethra and the two ejaculatory ducts
  • Consists of a capsule and numerous partitions
  • The cells lining the partitions secrete prostatic fluid
• Bulbourethral Gland


  • Also known as Cowper's glands
  • A pair of pea shaped exocrine glands
  • Contribute to the final volume of semen by producing a lubricating mucus secretion
• Urethra


  • Extends from the urinary bladder to the distal end of the penis
  • Can be divided into three parts: Prostatic urethra, Membranous urethra, Spongy urethra
• Semen


  Mixture of sperm cells and secretions from the male reproductive glands
• Composition of Semen


  • Prostate Gland - 30%
  • Testes - 5% (with sperm)
  • Seminal Vesicle - 60%
  • Bulbourethral Gland - 5%
• Mucous Secretions


  4 Primary Functions: 1. Lubrication of the urethra, 2. Neutralization of the acidic urethra, 3. Minimal lubrication during intercourse, 4. Reduction of the acidity of the vagina
• Substances in Semen


  • Thick Secretions: 1. Fructose - sperm cell nourishment, 2. Coagulation proteins - thicken the semen, 3. Enzymes - destroy abnormal sperm cells, 4. Prostaglandins - stimulate contractions of the female reproductive tract
  • Thin Secretions: 1. Regulate pH, 2. Liquefy coagulated semen
• Hormonal Regulation of Male Reproductive System

  1. Hypothalamus releases Gonadotropin-Releasing Hormones (GnRH)

  2. Anterior Pituitary Gland releases Luteinizing Hormone and Follicle-Stimulating Hormone

  3. Luteinizing Hormones bind to Leydig Cells and causes them to secrete Testosterones

  4. Follicle-Stimulating Hormones bind to Sertoli Cells and promote sperm development
• Effects of Testosterone


  • Penis and Scrotum enlargement and differentiation
  • Hair Follicles - hair growth and coarse hair, male pattern baldness
  • Skin - increased sebaceous and sweat gland secretions, coarser texture
  • Larynx - enlargement and deeper masculine voice
  • Blood - increased Erythropoietin secretion, increased RBC production
  • Muscle - increased Skeletal Muscle Mass
  • Bones - rapid bone growth
• Female Reproductive Organs


  • Ovaries
  • Fallopian Tubes
  • Uterus
  • Vagina
  • Mammary Glands (Breast)
• Ovaries


  • Females have two ovaries, small organs suspended in the pelvic cavity by two ligaments
• Ligaments of the Reproductive Tract

  • Broad Ligament - sheet of peritoneum associated with uterus and ovaries
  • Uterine Ligaments - ligaments associated with the uterus
  • Ovarian Ligaments - ligaments associated with the ovaries
• Fallopian Tubes


  • Also called "Uterine Tubes" or "Oviduct"
  • Each tube is associated with the uterus and the ovary
  • Receive the secondary oocyte from the ovary
  • Opening of each tube is surrounded by long, thin processes called FIMBRAE
  • Fertilization usually occurs in the ampulla near the ovary
• Uterus


  • As large as a medium-sized pear, shaped as such
  • Has three main parts - the fundus, the body, and the cervix
• Layers of the Uterine Wall

  • Perimetrium - serous layer formed from visceral peritoneum
  • Myometrium - middle muscular layer
  • Endometrium - innermost layer of simple columnar epithelium with underlying connective tissue
• Vagina


  • Female organ of copulation which receives the penis during intercourse, allows menstrual flow and childbirth
  • Superior part attached to the sides of the cervix, forming the Vaginal Fornix
  • Wall consists of an outer muscular layer and inner mucous membrane
• External Female Genitalia


  • Vestibule
  • Labia minora
  • Greater Vestibular Gland
  • Hymen
• Mammary Glands


  • Organs of milk production located in the breasts
  • Modified sweat glands
  • Enlarge during puberty under the influence of estrogen and progesterone
• Gynecomastia


  • Enlargement of the breast tissue in males, caused by higher than normal levels of the hormone ESTROGEN
• Breast Anatomy


  • Rib
  • Pectoralis Major Muscle
  • Fascia
  • Adipose Tissue
  • Suspensory Ligaments
  • Lobule
  • Lobe
• Milk Production and Flow


  Milk produced within the lobules drains into the mammary ducts, then into the lactiferous duct, and finally out through the nipple
• Breast Cancer


  • Most common types are Invasive Ductal Carcinoma (80%) and Invasive Lobular Carcinoma
  • Invasive Ductal Carcinoma begins from the mammary or lactiferous ducts, Invasive Lobular Carcinoma begins from the lobules
• Mammary Gland Structures


  • Myoepithelial cells that contract the alveoli
  • Epithelial cells that produce milk
  • Alveolus which is the secretory sac of the mammary gland
  • Mammary duct that drains the milk produced
• Effects of Hormones on Lactation

  1. Estrogen stimulates milk duct growth and differentiation, but high levels during pregnancy inhibit lactation

  2. Progesterone high during pregnancy inhibits lactation, but drops after birth to trigger milk production

  3. Prolactin stimulates the mammary gland to produce milk, the main hormone of lactation

  4. Oxytocin stimulates the myoepithelial cells to contract, expelling the milk