Reproduction and Development in Humans

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.

The resolution phase of the male sexual cycle is divided into two parts. During the primary stage of involution, penile detumescence occurs; the penis reduces to 50% of its fully erect state and remains completely refractory to stimulation. This stage is relatively short.

Erection occurs after activation of the parasympathetic nervous system.

During puberty, estrogen produced by the ovaries causes several changes in secondary sexual characteristic keratinization or cornification of the vaginal mucosa, enlargement of the labia minora and majora, uterine enlargement and increased fat deposition in the hips and thighs.

Both the epididymis and the vas deferens are made up of ducts which have muscular components. These muscular parts aid in peristalsis, which helps move spermatozoa along the ducts.

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.

It is correct. If SRY is absent, a fetus will develop into a female phenotype.

Renal glomerular filtration increases rather than decreases during pregnancy. Consider that during pregnancy the maternal circulating blood volume increases and along with that comes an increase in the renal blood flow simply because of the increased volume. An increase in renal blood flow correlates with an increase in the glomerular filtration rate. Filtration increases by as much as 50% by mid-pregnancy.

After the conception and implantation have occurred, the developing embryonic trophoblast secretes hCG which acts like luteinizing hormone to maintain support of the corpus luteum.

Primordial germ cells are maintained against the basement membrane of the seminiferous tubules; Sertoli cells do not appear to have a role in this process.

In gonadal development, undifferentiated primordial germ cells arise from the endoderm lining the yolk sac. These germ cells detach and migrate dorsally to reach the coelomic epithelium lining the genital ridges.

During ovulation, the oocyte is arrested in the metaphase of the second meiotic division.

Amnion is the membrane that surrounds and protects the fetal side of the placenta.

In males and females, the adrenal gland produces and secretes increased amounts of several weak androgens during puberty: androstenedione, dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEA-S). DHEA and DHEA-S are responsible for the commencement of pubic and axillary hair growth.

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.