Gametogenesis and Fertilization

Vocabulary flashcards summarizing key terms and concepts from the lecture on hormonal regulation, gametogenesis, and fertilization.

Gametogenesis

General process by which specialized reproductive cells (gametes) with 23 chromosomes are produced via meiosis in the testes or ovaries.

Spermatogenesis

Male branch of gametogenesis that forms sperm in the seminiferous tubules from puberty throughout life.

Oogenesis

Female branch of gametogenesis that forms a single ovum per cycle; begins before birth, pauses twice, and finishes only after fertilization.

Hypothalamic-Pituitary-Gonadal (HPG) Axis

Endocrine pathway where GnRH from the hypothalamus triggers pituitary release of LH and FSH to regulate the gonads.

Gonadotropin-Releasing Hormone (GnRH)

Hypothalamic hormone that stimulates the anterior pituitary to secrete LH and FSH.

Follicle-Stimulating Hormone (FSH)

Pituitary gonadotropin; stimulates Sertoli cells and spermatogenesis in males, and follicular growth in females.

Luteinizing Hormone (LH)

Pituitary gonadotropin; stimulates Leydig cells to produce testosterone in males and triggers ovulation and corpus luteum formation in females.

Sertoli Cells

Nurse cells in seminiferous tubules that support developing sperm under FSH influence and secrete inhibin.

Leydig Cells

Interstitial testicular cells that produce testosterone in response to LH.

Folliculogenesis

Process of growth and maturation of ovarian follicles leading up to ovulation.

Negative Feedback (Sex Steroids)

Testosterone, estrogen, progesterone, and inhibin suppress GnRH, LH, and FSH release to maintain hormonal balance.

Primordial Germ Cells (PGCs)

Embryonic precursors of gametes that originate in the yolk sac and migrate to primordial gonads.

Teratoma

Tumor that can arise when PGCs lodge outside the gonads, containing diverse tissues such as hair or teeth.

Oogonia

Mitotically active diploid female germ cells present between the 2nd–5th fetal month.

Spermatogonia

Mitotically active diploid male germ cells; proliferate prenatally and resume at puberty in waves throughout life.

Atresia

Degeneration and loss of excess oogonia or follicles that do not mature.

Meiosis

Two-division cell process that reduces chromosome number from diploid to haploid and introduces genetic variation.

Crossing Over

Exchange of DNA between homologous chromosomes during prophase I of meiosis, increasing genetic diversity.

Polar Body

Small, non-functional cell produced during oogenesis due to unequal cytokinesis; helps preserve cytoplasm in the ovum.

Spermiogenesis

Final maturation phase in which spermatids differentiate into motile spermatozoa.

Capacitation

Biochemical changes sperm undergo in the female tract that enhance motility and prepare them for fertilization.

Acrosomal Reaction

Enzyme-releasing event at the sperm head that digests the zona pellucida, allowing penetration of the oocyte.

Cortical Reaction

Release of cortical granules by the oocyte after sperm entry, hardening the zona pellucida to block polyspermy.

Zona Pellucida

Glycoprotein shell surrounding the oocyte that mediates sperm binding and triggers the acrosomal reaction.

Pronucleus

Haploid nucleus of either sperm or ovum prior to their fusion inside the zygote.

Karyogamy

Fusion of male and female pronuclei forming the diploid zygote nucleus.

Zygote

First diploid cell of a new individual formed after fertilization in the fallopian tube.

Block to Polyspermy

Mechanisms (fast electrical and cortical reaction) that prevent entry of additional sperm after the first fertilizes the egg.

Corpus Luteum

Hormone-secreting structure formed from the ruptured follicle after ovulation; produces progesterone and estrogen.

Primary Spermatocyte

Diploid male germ cell that enters meiosis I to form two secondary spermatocytes.

Secondary Spermatocyte

Haploid male germ cell produced after meiosis I; quickly enters meiosis II to yield spermatids.

Spermatid

Haploid round cell that matures into a spermatozoon during spermiogenesis.

Primary Oocyte

Diploid female germ cell arrested in prophase I from fetal life until puberty.

Secondary Oocyte

Haploid female germ cell produced at ovulation; arrested in metaphase II until fertilization.

Diploid (2n)

Cell containing two sets of chromosomes (46 in humans).

Haploid (n)

Cell containing one set of chromosomes (23 in humans).

Seminiferous Tubule

Coiled structure in the testes where spermatogenesis takes place.

Male Secondary Sex Characteristics

Traits such as facial hair, deepened voice, and broadened shoulders induced by testosterone during puberty.

Female Secondary Sex Characteristics

Traits such as breast development and widened hips induced by estrogen during puberty.