Endometrium Layers and Menstrual Cycle Hormones

Ovarian Cycle

• Ovulating follicle ruptures and releases a primary oocyte, which then forms the corpus luteum.
• Corpus luteum secretes progesterone until it shrinks and degrades into corpus albicans.
• FSH stimulates development of a few primordial to tertiary follicles.
• LH stimulates estradiol release from follicles, and larger follicles secrete more estrogen.
• High estrogen levels trigger a negative feedback loop, causing atresia of most follicles and selecting one dominant follicle to survive.

Hormonal Regulation

• If fertilization occurs, corpus luteum is maintained and progesterone secretion continues to support implantation.
• If fertilization does not occur, corpus luteum shrinks to corpus albicans and progesterone secretion ends, causing the stratum functionalis to shrink and menses to occur.
• GnRH, LH, and FSH secretion increases, causing dominant follicles to develop.
• GnRH stimulates the release of LH and FSH from the adenohypophysis.
• LH triggers ovulation, and FSH stimulates the development of follicles.

Endometrial Cycle

• The ovarian cycle regulates the endometrial cycle through estrogen and progesterone.
• The endometrial cycle ensures the suitability of the uterus for implantation of a newly formed embryo.
• The stratum basale has the same thickness throughout the reproductive cycle.
• Implantation is most successful during the secretory phase (after ovulation) because the cells are thickest there.

Menopause and Puberty

• At menopause, estrogen levels decrease drastically, and gonadotropin (LH and FSH) levels increase as a result.
• At puberty, estrogen levels increase, and gonadotropin (LH and FSH) levels decrease as a result.

Reproductive System

• The corpus luteum secretes mostly progesterone.
• The two hormones secreted by the adenohypophysis that influence the female reproductive cycle are FSH and LH.
• The thickest layer of the uterus is the myometrium.
• Ovulation is triggered by an increase in LH levels, while endometrial growth is triggered by an increase in progesterone levels.

Lactation and Breast Development

• Estrogen helps in developing the glands for lactation.
• Progesterone is involved in duct work for lactation.
• Oxytocin stimulates breast milk, while prolactin stimulates its release.

Sperm Development and Fertilization

• Spermatogenesis and oogenesis require a special form of cell division called meiosis.
• The acrosome of sperm contains enzymes needed to penetrate the egg.
• If fertilization occurs, the meiotic division of the secondary oocyte produces a second polar body, and a mature fertilized ovum called the zygote.
• Polyspermy is the penetration of an oocyte by more than one sperm.

Male Reproductive System

• Pathway of sperm: Seminiferous tubules (in the testes) → Epididymis → Ductus deferens → Ejaculatory duct → Urethra.
• Bulbourethral (Cowper's) glands secrete a thick, salty fluid that lubricates the urethra and vagina.
• Prostate glands secrete an alkaline, milky fluid.
• Fructose serves as an energy source for sperm mitochondria.

Gamete Production and Lifespan

• Females' gamete production starts at puberty and ends at menopause.
• Males' gamete production starts at puberty and ends at death.
• Mitosis I in females occurs before birth, while in males, it occurs after puberty.
• Meiosis I in females occurs after puberty, while in males, it occurs after puberty.
• Meiosis II in females occurs after fertilization, while in males, it occurs after puberty.

Fetal Development and Sex Organs

• Bipotential gonads are connected to a central cavity (cloaca) via Mullerian and Wolffian ducts.
• During fetal development, testosterone levels rise to stimulate early development of male sex organs.