Male Reproductive System Quiz

Physiology & Anatomy II - Reproduction - Sex Hormones

• Competency Objectives: Students will be able to illustrate the anatomy of the male and female genital systems, detail the chemical nature, actions, and regulation of testosterone, estrogen, and progesterone hormones, and describe ovarian hormone regulation.

Male Reproductive System

• Anatomy: Includes two testes producing sperm and secreting androgens (primarily testosterone).
• Testis Structure: Composed of:
  • Seminiferous Tubules (80%): Coiled tubes (900) where sperm are formed (spermatogenesis). Bounded by a basement membrane, contain fluid-filled lumen with spermatozoa. Sertoli cells within the tubules provide nutrients, hormones, and enzymes to growing spermatids.
  • Leydig Cells (20%): Interstitial cells located in the connective tissue between seminiferous tubules; these cells primarily secrete testosterone.
• Ducts: Series of ducts leading from testes to penis:
  • Epididymis: Coiled tube (6 meters) where sperm undergo maturation.
  • Vas Deferens: Sperm remain viable here for months; dilated terminal part is the ampulla
  • Ejaculatory Duct: Opens into the urethra.
• Accessory Glands: Secrete fluid suspending ejaculated sperm:
  • Prostate: Secretes thin alkaline fluid (20% of semen volume), containing cholesterol, phospholipids, zinc, and citric acid.
  • Seminal Vesicles: Secrete mucoid material (60% of semen volume), containing fructose and other nutrients.
  • Bulbourethral Glands: Secrete mucus.

Testosterone Hormone

• Chemical Nature: A steroid hormone synthesized by Leydig cells from cholesterol, sometimes converted to dihydrotestosterone (more active form) in target organs (e.g., prostate).
• Actions:
  • Growth of Sex Organs: Increased secretion at puberty promotes growth of testes, scrotum, and penis, and increases secretory activity of epididymis, prostate, and seminal vesicles.
  • Secondary Sex Characteristics:
    • Body Hair: Increases hair on face, chest, and other body areas. Influences male hair distribution (e.g., hairline recession).
    • Voice: Enlargement of the larynx and thickening of vocal cords lead to a deeper voice.
    • Body Configuration: Broader shoulders and enlarged muscles.
    • Skin: Thickening of skin and increased secretion of sebaceous glands.
  • Growth: Increases protein synthesis, leading to overall body growth and skeletal muscle development. Stimulates bone growth during puberty (linear growth spurt).
  • Erythropoiesis: Stimulates the production of erythropoietin hormone.
  • Prenatal Development: Stimulates fetal differentiation of the male genital tract and the descend of the testes.

Regulation of Testosterone Secretion

• Hypothalamic Regulation: Hypothalamus secretes GnRH into hypothalamic-hypophyseal portal vessels, stimulating FSH and LH secretion from the anterior pituitary.
• Anterior Pituitary Regulation: Anterior pituitary secretes FSH and LH. FSH acts on Sertoli cells to maintain spermatogenesis; LH acts on Leydig cells to promote testosterone synthesis.
• Negative Feedback: Testosterone inhibits LH secretion by inhibiting GnRH release from the hypothalamus and inhibiting LH secretion directly from the anterior pituitary. Sertoli cells secrete inhibin, which also inhibits FSH.

Female Reproductive System

• Functional Anatomy:
  • Ovaries: Produce ova and secrete estrogen and progesterone.
  • Uterus: Divided into fundus, body, and cervix; lined by the endometrium, thick muscular wall (myometrium).
  • Vagina: Muscular tube (10 cm) lined by stratified squamous epithelium.
  • Fallopian Tubes: (2) Each tube is 10 cm long and 8 mm in diameter, with a fimbriated end opening into the abdominal cavity.

Estrogen Hormone

• Chemical Nature: A steroid hormone synthesized by ovaries from cholesterol, secreted by growing follicles.
• Actions:
  • Growth of Sex Organs: Stimulates growth and development of the uterus, fallopian tubes, vagina, and breasts; also, increases myometrial contractions and responsiveness to oxytocin during pregnancy, and prepares the endometrium for progesterone actions.
  • Secondary Sex Characteristics:
    • Figure: Deposition of body fat (breasts, thighs, buttocks), narrower shoulders, broader hips, less body hair, more scalp hair, and higher-pitched voice.
  • Growth: Stimulates linear bone growth during puberty (pubertal growth spurt), resulting in early closure of the epiphyses, potentially leading to shorter adult height compared with males.
  • Metabolic Effects: Promotes salt and water retention.
  • Prolactin Secretion: Stimulates prolactin secretion by anterior pituitary but inhibits prolactin's milk-producing action on the breasts (can result in increased prolactin with no milk formation), particularly during pregnancy.

Progesterone Hormone

• Chemical Nature: A steroid hormone synthesized by the ovary from cholesterol secreted by the corpus luteum.
• Actions:
  • Uterus: Essential for preparing the endometrium for fertilized ovum implantation, increasing vascularity and secretory activity. During pregnancy, it decreases myometrial excitability and sensitivity to oxytocin.
  • Mammary Glands: Promotes growth of acini and increases secretory function in estrogen-primed mammary glands.
  • Thermogenic Effect: Increases basal body temperature.

Regulation of Ovarian Hormones

• Hypothalamic Regulation: Hypothalamus secretes GnRH, stimulating anterior pituitary to secrete FSH and LH.
• Anterior Pituitary Regulation: FSH and LH stimulate:
  • Secretion of Estrogen and Progesterone.
  • Follicular Development.
  • Ovulation.
  • Corpus Luteum Formation.
• Feedback Regulation:
  • Estrogen: Provides negative feedback with moderate increase, positive feedback with marked increase.
  • Progesterone: Provides negative feedback on the anterior pituitary and hypothalamus.