Gestation
Pregnancy begins with the fertilization of an egg and continues through to the birth of the individual. The length of time of gestation, or the gestation period, in humans is…
The Ovarian Cycle and the Menstrual Cycle
The ovarian and menstrual cycles are regulated by hormones of the hypothalamus, pituitary, and ovaries (Figure 13.17). The ebb and flow of the hormones causes the ovarian and menstrual cycles…
Hormonal Control of Reproduction
The human male and female reproductive cycles are controlled by the interaction of hormones from the hypothalamus and anterior pituitary with hormones from reproductive tissues and organs. In both sexes,…
Gametogenesis (Spermatogenesis and Oogenesis)
Gametogenesis, the production of sperm and eggs, involves the process of meiosis. During meiosis, two nuclear divisions separate the paired chromosomes in the nucleus and then separate the chromatids that…
Human Reproduction
As in all animals, the adaptations for reproduction in humans are complex. They involve specialized and different anatomies in the two sexes, a hormone regulation system, and specialized behaviors regulated…
Development and Organogenesis
The process by which an organism develops from a single-celled zygote to a multi-cellular organism is complex and well regulated. The regulation occurs through signaling between cells and tissues and…
Fertilization
The fusion of a sperm and an egg is a process called fertilization. This can occur either inside (internal fertilization) or outside (external fertilization) the body of the female. Humans…
Sexual Reproduction
Sexual reproduction is the combination of reproductive cells from two individuals to form genetically unique offspring. The nature of the individuals that produce the two kinds of gametes can vary,…
Introduction to Animal Reproduction and Development
Figure 13.1 Female seahorses produce eggs that are then fertilized by the male. Unlike with almost all other animals, the young then develop in a pouch of the male seahorse…
Disruptions in the Immune System
A functioning immune system is essential for survival, but even the sophisticated cellular and molecular defenses of the mammalian immune response can be defeated by pathogens at virtually every step.…
