Detailed Notes on the Reproductive System

Reproductive System Notes

Overview of Reproductive Systems

• The reproductive system is essential for the production, maintenance, and delivery of reproductive cells (gametes).
• Primary organs: testes (for males), ovaries (for females).
• Secondary organs maintain and deliver sperm and eggs.
• Endocrine control through hormones (e.g., androgens in males, estrogens/progesterone in females).

Male Reproductive System

Functions

• Produce, maintain, and deliver sperm to the female reproductive system.
• Secrete male sex hormones (androgens).

Primary Reproductive Organs (Testes)

• Structure: Ovoid shape (5x3 cm), suspended by spermatic cord, located in the scrotum.
• Descent of Testes:
  • Stimulated by testosterone, descend from near kidneys into scrotum shortly before birth.
  • Important for sperm production which requires lower temperatures than body heat.

Structure of Testes

• Enclosed in fibrous tunica albuginea.
• Divided into lobules that contain seminiferous tubules where spermatogenesis occurs.
• Sertoli cells provide nuture to developing sperm.
• Cells of Leydig produce hormones.

Spermatogenesis

1. Initiation: Spermatogonia undergo mitosis to produce more spermatogonia.
2. Meiosis: At puberty, testosterone triggers meiosis in spermatogonia, producing primary spermatocytes.
3. Differentiation: Primary spermatocytes divide to form secondary spermatocytes (23 chromosomes each).
4. Further Division: Secondary spermatocytes divide into spermatids, which mature into spermatozoa after acquiring a tail.
5. Storage: Mature sperm are stored in the epididymis until ejaculation.

Sperm Structure

• Head: Contains nucleus (23 chromosomes) and acrosome with enzymes.
• Midpiece: Contains mitochondria for energy.
• Tail: Flagellum for motility.

Seminal Fluid and Accessory Organs

• Epididymis: Supports maturing sperm, facilitates storage.
• Vas Deferens: Muscular tube carrying sperm towards ejaculation duct.
• Seminal Vesicles: Secrete alkaline fluid (regulates pH), fructose (nutrient for sperm).
• Prostate Gland: Secretes milky fluid to aid sperm motility.
• Bulbourethral Glands: Lubricates penis during intercourse.

Hormonal Control

• Hypothalamus releases GnRH (gonadotropin-releasing hormone), stimulating pituitary gland.
• LH (Luteinizing Hormone): Stimulates testosterone release from Leydig cells.
• FSH (Follicle Stimulating Hormone): Stimulates Sertoli cells to support spermatogenesis.

Female Reproductive System

Functions

• Produce and transport eggs, maintain and nourish a developing fetus, secrete female hormones.

Primary Reproductive Organs (Ovaries)

• Positioned in pelvic cavity, held by ligaments.
• Contains follicles with oocytes.
• Oogenesis: Begins in fetal development, halts until puberty.
  • Follicles produce estrogen which regulates menstrual cycle.

Female Reproductive Cycle

• Menstrual cycle involves phases: menses, proliferative phase, secretory phase.
  1. Menses: Shedding of the uterine lining.
  2. Proliferative Phase: Thickening of endometrium.
  3. Secretory Phase: Increase in vascularization and preparation for implantation.

Follicle Development and Ovulation

• At puberty, one follicle matures from group of primordial follicles
• Ovulation: Triggered by LH, egg is released into the uterine tube.

Structural Overview of Female Anatomy

• Uterine Tubes (Fallopian Tubes): Site of fertilization, transports egg.
• Uterus: Site for fertilized egg development (three layers: endometrium, myometrium, perimetrium).
• Vagina: Musculomembranous tube for coitus and birth, partially covered by hymen.
• External Accessory Organs: Vulva includes labia majora, labia minora, clitoris, vestibule, and their associated glands.

Hormonal Regulation

• Estrogen: Develops secondary sexual characteristics, regulates menstrual cycle.
• Progesterone: Prepares the uterus for potential pregnancy.
• FSH and LH: Regulates menstrual cycle, triggers follicle maturation and ovulation respectively.

Summary of Hormonal Changes and Feedback Mechanism

• Changes in estrogen and progesterone levels directly influence the menstrual cycle.
• Feedback mechanisms ensure the cycle continues with each phase preparing for potential fertilization.