Gametogenesis and Fertilization

Study Notes

Understanding sperm production through gametogenesis (spermatogenesis).
Understanding oocyte production through oogensis (gametogenesis in females).
Comprehending fertilization and its immediate consequences.
Identifying processes occurring during the first three weeks of human development.

Male gametes are called spermatozoa; spermatogenesis occurs in the testes after puberty (12-14 years).
Influenced by follicle-stimulating hormone (FSH) and testosterone.
Optimal spermatogenesis temperature is 2-3°C below body temperature.
Continuous process that peaks at approximately age 25, producing about 150,000 spermatozoa per testis daily.
Transition from spermatogonium to primary spermatocytes takes 16 days, primary spermatocytes to spermatids takes 24 days, and spermatids to spermatozoa takes 24 days, totaling 64 days for the entire process.

Female gametes are secondary oocytes (ova), and oogenesis starts in the ovaries before birth (5 months in utero).
Occurs under the influence of FSH and luteinizing hormone (LH) and involves primordial germ cells transforming into oogonia and then primary oocytes.
Oogenesis is unique as it is suspended between birth and puberty and resumes at puberty (9-13 years).
Continues cyclically until menopause (45-55 years), producing typically one ovum per cycle.
Post-puberty, primary oocytes undergo first meiosis, resulting in secondary oocytes; ovulation occurs through LH surge.

Fertilization involves the fusion of one male gamete (spermatozoon) with one female gamete (secondary oocyte).
Successful fertilization requires female ovulation of secondary oocyte, competent spermatozoa within 24 hours, and an environment free from infections.
Spermatozoon is significantly smaller than the ovum, which is larger and has protective layers including zona pellucida and corona radiata.

Begins with zygote formation from fertilization, leading to cleavage.
Cleavage consists of rapid mitotic divisions, producing smaller cells (blastomeres) without cytoplasm synthesis.
First week characterized by cleavage occurring within the oviduct.
The human blastocyst forms around days 5-9 post-fertilization, featuring a fluid-filled cavity (blastocoel).

Process where the blastocyst attaches and invades the uterine endometrium, requiring hatching from the zona pellucida.
Trophoblast cells adhere to the receptive endometrium during the secretory phase influenced by progesterone from the corpus luteum.

Notable for differentiation of cells; the blastocyst develops into an embryoblast and trophoblast, both important for implantation.
Formation of two cavities develops in relation to the two layers of the embryoblast (bilaminar embryonic disc).

Characterized by gastrulation, transitioning the bilaminar disc into a trilaminar disc.
Involves cell migration from the epiblast through the primitive streak to form the three primary germ layers: ectoderm, mesoderm, and endoderm.
Each germ layer gives rise to specific tissues: epithelia from all layers, connective tissue from mesoderm, nerve tissue from ectoderm, and muscle tissue from mesoderm.