MCAT - Organ Systems:: Reproductive System

The presence of a Y chromosome, specifically the SRY gene it carries, determines male sexual differentiation primarily by:

- **A)** Directly producing testosterone itself
- **B)** Triggering the undifferentiated bipotential gonad to develop into a testis, which then produces testosterone and anti-Mullerian hormone (AMH) to drive subsequent male development
- **C)** Suppressing all hormone production in the developing embryo
- **D)** Having no functional role in sex determination

Anti-Mullerian hormone (AMH), secreted by fetal Sertoli cells, functions to:

- **A)** Stimulate development of the uterus and fallopian tubes
- **B)** Directly produce testosterone
- **C)** Cause regression/involution of the Mullerian (paramesonephric) ducts, which would otherwise develop into the uterus, fallopian tubes, and upper vagina - allowing normal male internal reproductive tract development
- **D)** Have no functional role in sexual differentiation

Meiosis differs fundamentally from mitosis in that meiosis:

- **A)** Produces two genetically identical diploid daughter cells
- **B)** Involves only a single round of DNA replication and a single round of cell division, identical to mitosis
- **C)** Occurs in all somatic (body) cells throughout life
- **D)** Involves two successive rounds of cell division (meiosis I and II) following a single round of DNA replication, ultimately producing four genetically unique haploid gametes, with genetic recombination occurring during meiosis I via crossing over between homologous chromosomes

Spermatogenesis, the production of mature sperm, occurs within which structure of the testis?

- **A)** The seminiferous tubules, where germ cells progressively mature while closely associated with supportive Sertoli cells
- **B)** The epididymis, where sperm are actually produced from scratch
- **C)** The vas deferens
- **D)** The prostate gland

Sertoli cells, located within the seminiferous tubules, support spermatogenesis through which combination of functions?

- **A)** Only producing testosterone, with no other role
- **B)** Directly dividing to become sperm cells themselves
- **C)** Producing estrogen exclusively, with no other function
- **D)** Forming the blood-testis barrier (protecting developing germ cells from autoimmune attack and providing a specialized microenvironment), secreting nutrients/factors supporting germ cell maturation, secreting inhibin (providing negative feedback on FSH), and responding to FSH stimulation

Leydig cells, located in the interstitium between seminiferous tubules, are the primary site of:

- **A)** Sperm production itself
- **B)** Testosterone synthesis, stimulated by LH from the anterior pituitary
- **C)** Formation of the blood-testis barrier
- **D)** Inhibin secretion

Oogenesis differs from spermatogenesis in a key timing aspect: primary oocytes are:

- **A)** Continuously produced throughout adult life, identical to sperm production
- **B)** Not formed until puberty begins
- **C)** Arrested in prophase I of meiosis before birth, remaining in this suspended state (sometimes for decades) until that individual follicle is recruited for ovulation, at which point meiosis I completes just before ovulation
- **D)** Never undergo meiosis at all, unlike sperm

The menstrual cycle's follicular phase is characterized by which combination of hormonal and ovarian events?

- **A)** Rising FSH stimulates recruitment and growth of a cohort of ovarian follicles (with typically one dominant follicle emerging), which produce increasing amounts of estrogen as they mature, and estrogen stimulates proliferation of the endometrial lining
- **B)** Falling FSH and LH with no follicular development
- **C)** The corpus luteum is the dominant structure, producing high progesterone
- **D)** Uterine lining shedding is the primary event throughout this entire phase