Types of Asexual Reproduction

Asexual Reproduction

• Binary fission: a method used by unicellular organisms (prokaryotes and mitochondria and chloroplasts of eukaryotes) where DNA is replicated and cell divides into two separate cells.
• Budding: a method used by organisms like hydra and yeast, where a bud forms, receives a copy of DNA, and breaks off to create a new individual.
• Regeneration: a method used by organisms like hydra, planaria, and fungi, where a new individual can grow from a broken piece or a fragment.
• Parthenogenesis: a method used by some organisms, like honeybees, where an unfertilized egg develops into a viable offspring.

Human Reproduction - Sexual Reproduction

• Sexual reproduction: the joining of two gametes (male sperm and female egg) to create offspring.
• Gametes are produced by germ cells (male spermatogonia, female oogonia) through meiosis.

Spermatogenesis

• Spermiogenesis: the final stage of spermatogenesis, where haploid spermatids differentiate into mature, motile spermatozoa.
• Spermatogenesis: the formation of mature spermatozoa from spermatogonia, involving two meiotic divisions to produce 4 spermatids.
• Spermatogenesis occurs in seminiferous tubules of testes, involving Sertoli cells and spermatogenic cells.
• Sperm are transported through epididymis, vas deferens, and ejaculatory duct to be ejaculated out of the penis as semen.

Sperm Structure

• Head: contains nucleus and acrosome.
• Midpiece: contains mitochondria for ATP production.
• Tail: long flagellum (microtubules) for propulsion.

Accessory Glands

• Seminal vesicles: secrete fructose, viscous mucus, and prostaglandins.
• Prostate gland: secretes alkaline fluids to counteract uterine acidity.
• Bulbourethral glands: secrete viscous mucus that cleans and lubricates the urethra.

Hormones in Males

• Follicle stimulating hormone (FSH): stimulates sperm development in seminiferous tubules.
• Luteinizing hormone (LH): stimulates Leydig cells to produce testosterone.
• Testosterone: matures sperm and gives rise to male secondary sex characteristics.

Female Anatomy and Oogenesis

• Vagina: opens to an external environment where sperm enters and birth occurs.
• Uterus: a muscular, vascular organ that provides an ideal environment for fertilized eggs to implant and develop.
• Ovary: produces eggs (ova) that travel through the oviduct to the uterus.

Oogenesis

• Many oogonia are produced, with the majority dying via apoptosis, and a small fraction differentiating into primary oocytes that begin meiosis but are arrested in prophase I until puberty.
• At puberty, one egg per month ovulates, completing meiosis I, and producing a large secondary oocyte and a polar body.