Human Biology - Fertilization and Development

A set of flashcards covering key concepts in fertilization and human development, useful for exam preparation.

What is fertilization in human biology?

Fertilization is the union of a sperm and an egg, forming a zygote, the first cell of a new individual.

What are the parts of a sperm cell and their functions?

The tail (flagellum) propels the sperm, the middle piece contains mitochondria, and the head contains the nucleus and acrosome with digestive enzymes.

What is the role of the zona pellucida in fertilization?

The zona pellucida surrounds the egg and acts as a barrier that several sperm must penetrate to allow one sperm to fertilize the egg.

How does a sperm penetrate the zona pellucida?

The acrosome of the sperm releases digestive enzymes that create a pathway through the zona pellucida.

What prevents polyspermy during fertilization?

Upon the first sperm's contact with the egg, the egg’s plasma membrane depolarizes, preventing any additional sperm from binding and entering.

What changes occur to the zona pellucida after fertilization?

Cortical granules release enzymes that modify the zona pellucida into a fertilization membrane, preventing other sperm from binding.

What processes occur immediately after fertilization?

Cleavage begins, where the zygote divides by mitosis, while the ball of cells does not increase in size.

What occurs during embryonic development weeks 2 to 8?

During weeks 2 to 8, embryonic development includes growth and differentiation into the primary germ layers: ectoderm, mesoderm, and endoderm.

What are the three primary germ layers and their derivatives?

Ectoderm (skin, nervous system), mesoderm (muscular and skeletal systems), and endoderm (lining of respiratory and digestive tracts).

What is the significance of human chorionic gonadotropin (HCG) after implantation?

Human chorionic gonadotropin (HCG) is secreted by the chorion to prevent menstruation and is the basis for pregnancy tests.

What happens during the fourth and fifth weeks of development?

The umbilical cord connects the embryo to the chorion, and limb buds appear, developing into arms and legs.

How does the fetal development process progress in terms of size and susceptibility?

In fetal development from the third to ninth months, the fetus increases in size and weight and becomes susceptible to environmental influences.

Describe the feedback mechanism used during labor.

Uterine contractions are strengthened by a positive feedback mechanism involving oxytocin release, stimulating further contractions that push the fetus down.