Reproduction

The LH surge is primarily responsible for ovulation.

The primary function of Leydig cells is to synthesize and secrete testosterone. Leydig cells do this in a dose-dependent manner in response to LH.

During fertilization, a sperm cell penetrates an oocyte (egg); fusion of sperm and oocyte membranes drives an increase in intracellular calcium in the oocyte. This fusion and rise in calcium causes depolarization of the egg membrane which prevents other sperm cells from fusing with the egg cell (this is the primary block to polyspermy).

The ovaries are supplied by the ovarian arteries which branch directly off of the aorta just below the renal arteries.

Prolonged elevations in estrogen, not progesterone, triggers the LH surge. Prolonged elevations of progesterone suppress FSH and thus the next menstrual cycle (consider that pregnancy results in elevated progesterone levels, maintaining the endometrium and suppressing ovulation).

Removal of the middle portions of both fallopian tubes does not affect the function of the cilia which lines the inside of the fallopian tubes.

During initial follicular growth, the oocyte grows larger, granulosa cells increase in number, and a zona pellucida, or protein matrix, forms around the oocyte. The fluid filling the follicler continues to accumulate and the cellular surface of the follicle thins in preparation for ovulation. This process can be seen grossly and has been described as a blister on the ovarian surface.

Those testicular cells destined to become Sertoli cells will secrete MIS under the direction of SRY and cause the Müllerian ducst to degenerate.

Ectoderm is the outermost of the three primary germ layers of an embryo, from which the epidermis, nervous tissue and sense organs develops. The human mammary gland is derived from ectoderm.

The developing embryo has two main populations of cells: an inner cell mass and a trophectoderm. The trophectoderm cells lie at the outer surface of the developing embryo and will become the placenta.

Follicle-stimulating hormone (FSH) causes maturation of a cohort of early-stage ovarian follicles; one of these will ultimately become the dominant or graafian follicle.

Mesenchyme arising beneath the germinal epithelium in the testes is the precursor to testicular interstitial cells, or Leydig cells, while in the ovaries it is the precursor to ovarian stroma or thecal cells.

Urine flows more slowly through the maternal renal collecting system due to dilatation of the ducts. This dilatation is the result of mechanical obstruction by the enlarging uterus along with the relaxing effects of progesterone on smooth muscle.

A fall in maternal progesterone levels results in sloughing of the endometrial wall and allows the next ovulation cycle to begin. Therefore, in order for an embryo to implant and remain in the uterus, local and systemic maternal progesterone levels must remain elevated. For the first 14 days after ovulation, the corpus luteum secretes progesterone. Without additional support, the corpus luteum spontaneously regresses at the end of a typical menstrual cycle.

Interphase occurs just prior to cell division. Prepubertal male primordial germ cells are reactivated from interphase at puberty and enter rounds of mitoses followed by meiosis 1 and 2 to produce unique haploid sperm.