Lecture 26: Reproduction 3 — Sex Determination & Hormonal Regulation of Gametogenesis

What is the typical female sex chromosome pattern in the slides?

XX.

What is the typical male sex chromosome pattern in the slides?

XY.

What gene initiates typical testis differentiation?

SRY.

What gonads develop in the absence of testis-determining signals?

Ovaries.

What does GnRH stand for?

Gonadotropin-releasing hormone.

Where is GnRH released?

Hypothalamus.

What gland responds to GnRH by releasing FSH and LH?

Anterior pituitary.

What does FSH stand for?

Follicle-stimulating hormone.

What does LH stand for?

Luteinizing hormone.

What ovarian cells make androgens after LH stimulation?

Theca cells.

What ovarian cells convert androgens into estrogen?

Granulosa cells.

What enzyme converts androgens to estrogens?

Aromatase.

What hormone from granulosa cells inhibits FSH?

Inhibin B.

What are the two ovarian cycle phases?

Follicular and luteal.

What is the follicular phase?

The pre-ovulation period of follicle growth.

What is the luteal phase?

The post-ovulation period when the corpus luteum is active.

What hormone surge triggers ovulation?

LH surge.

What causes the midcycle LH surge?

Sustained high estrogen produces positive feedback.

What does the corpus luteum secrete?

Mainly progesterone, plus estrogen.

What happens when the corpus luteum breaks down?

Progesterone and estrogen fall.

What are the three uterine cycle phases?

Menstrual, proliferative, and secretory.

What happens during the menstrual phase?

The uterine lining is shed.

What happens during the proliferative phase?

The endometrium rebuilds under estrogen influence.

What happens during the secretory phase?

Progesterone prepares the endometrium for implantation.

When does ovulation occur in the model 28-day cycle?

Around day 14.

What is a primary oocyte?

An immature oocyte arrested in meiosis I.

What cell is released during ovulation?

A secondary oocyte.

What is the role of Leydig cells?

Produce testosterone in response to LH.

What is the role of Sertoli cells?

Support sperm development and release inhibin B.

Which hormone stimulates Leydig cells?

LH.

Which hormone acts on Sertoli cells?

FSH.

What does inhibin B do in males?

Reduces FSH secretion by negative feedback.

What is androgen-binding protein (ABP)?

A Sertoli-cell protein that helps maintain testosterone concentration in seminiferous tubules.

Where is testosterone produced?

Leydig cells in testes.

How is male GnRH secretion described in the slides?

Pulsatile throughout the day, about every 1.5–2 hours.

What is spermatogenesis?

Formation of sperm in seminiferous tubules.

When does spermatogenesis begin?

At puberty.

What are the three broad stages of spermatogenesis?

Mitosis, meiosis, and sperm maturation (spermiogenesis).

What do spermatogonia do?

Divide by mitosis to maintain germ-cell supply and form sperm precursors.

What does a primary spermatocyte produce after meiosis I?

Two haploid secondary spermatocytes.

What do two secondary spermatocytes produce after meiosis II?

Four haploid spermatids.

What is spermiogenesis?

Transformation of spermatids into mature-shaped sperm.

How many chromosomes are in a mature human sperm?

23.

What is the acrosome?

An enzyme-containing cap on the sperm head.

What does the sperm midpiece contain?

Mitochondria.

What does the sperm flagellum do?

Provides propulsion.

What is the difference between mitosis and meiosis?

Mitosis maintains chromosome number; meiosis reduces it by half.

What does diploid (2n) mean?

Two sets of chromosomes.

What does haploid (n) mean?

One set of chromosomes.