Spermatogenesis and Oogenesis Overview

Spermatogenesis and Oogenesis

• Spermatogenesis: The process of sperm production in males, occurring in seminiferous tubules without any arrests.
• Oogenesis: The formation of oocytes in females, characterized by two key arrests: one at prophase I and another at metaphase II.
• Fertilization: When sperm encounters a secondary oocyte arrested in metaphase II, leading to the transition from secondary oocyte to mature ovum.

Female Reproductive Cycle

• Primary oocytes: Present in females at birth, arrested in prophase I.
• Secondary oocytes: Formed during puberty as primary oocytes complete the first meiotic division, arrested in metaphase II until fertilization.
• Genetics of Fertilization: If sperm carries X chromosome and ovum is X, resulting zygote is XX (female); if sperm carries Y, zygote is XY (male).

Endocrinology Overview

• Hypothalamus and Anterior Pituitary: Hypothalamus releases hormones (e.g., GnRH) that stimulate anterior pituitary to produce FSH and LH, which regulate gonadal function.
• FSH and LH in Males:
  • FSH is crucial for spermatogenesis via Sertoli cells.
  • LH stimulates Leydig cells to produce testosterone.

Hormonal Functions

• FSH in Females: Promotes follicle development.
• LH in Females: Triggers ovulation and formation of the corpus luteum which secretes progesterone.
• Adrenal Gland Regulation: ACTH from the pituitary regulates cortisol production in the adrenal cortex.

Posterior Pituitary

• Storage of Hormones: Stores ADH (antidiuretic hormone) and oxytocin, produced by hypothalamic nuclei.
• Functions of ADH: Maintains blood pressure by restricting blood vessels and promoting water reabsorption in kidneys.
• Functions of Oxytocin: Facilitates milk ejection in breastfeeding and uterine contractions during childbirth.

Structure of Sperm

• Composed of three main parts:
  • Head: Contains nucleus and acrosome (enzymes for fertilization).
  • Midpiece: Contains mitochondria for energy (ATP production).
  • Flagellum: Provides motility.

Spermatogenesis Process

• Stages include spermatogonia, primary spermatocyte, secondary spermatocyte, spermatid, and spermatozoa.
• Sertoli Cells: Support spermatogenesis and form blood-testis barrier; they do not produce sperm.
• Temperature Sensitivity: Spermatogenesis is temperature-sensitive, necessitating external testicle location to maintain lower temperatures.

Male and Female Cancer Risks

• Hormonal Influence on Cancer:
  • Male cancers (e.g., prostate) may be influenced by male hormones, with treatments including anti-androgens.
  • Female cancers (e.g., breast, ovarian) can be hormone-dependent, treated with aromatase inhibitors.

Pharmacology Highlights

• Testosterone Modulation:
  • Antagonists (e.g., flutamide) block testosterone receptors.
  • Inhibitors (e.g., finasteride) block conversion to dihydrotestosterone through 5-alpha reductase.
  • Aromatase inhibitors (e.g., anastrozole) prevent testosterone conversion to estrogen.

Side Effects of Cancer Treatments

• Anti-androgens may lead to decreased libido, erectile dysfunction, and gynecomastia in males.
• GnRH analogs may induce menopause-like symptoms in females, including hot flashes and osteoporosis.

Summary of Ejaculatory Pathway

• Seven-Up Pathway:
  • Seminiferous tubules ➔ Epididymis ➔ Vas deferens ➔ Ejaculatory duct ➔ Urethra ➔ Penis.

Upcoming Topics

• Further exploration of oogenesis and the menstrual cycle expected in future discussions.

Explore the processes of spermatogenesis and oogenesis, essential for male and female reproductive cycles. Learn about the stages of oocyte development and the role of fertilization in determining genetic outcomes. This quiz covers hormonal influences and developmental biology pertinent to reproduction.